Publikationen

1: Al-Ahmad, A; Wiedmann-Al-Ahmad, M; Faust, J; Bächle, M; Follo, M; Wolkewitz, M; Hannig, C; Hellwig, E; Carvalho, C; Kohal, R

Biofilm formation and composition on different implant materials in vivo.

Journal of biomedical materials research. Part B, Applied biomaterials 2010/Oct, 95(1):101-9

Department of Operative Dentistry and Periodontology, Albert-Ludwigs-University, 79106 Freiburg, Germany.

Biofilm formation was evaluated on the following titanium and zirconia implants in vivo: machined titanium (Ti-m), modified titanium (TiUnite), modified zirconia (ZiUnite), machined alumina-toughened zirconia (ATZ-m), sandblasted alumina-toughened zirconia (ATZ-s), and machined zirconia (TZP-A-m). Bovine enamel slabs were used as controls. Surface morphologies were examined by atomic force (AFM) and scanning electron microscopy (SEM). The surface wettability was also determined. Twelve healthy volunteers wore a splint system with the tested materials. After 3 and 5 days the materials were examined by fluorescence in situ hybridization (FISH) and confocal laser scanning microscopy (CLSM). The levels of Streptococcus spp., Veillonella spp., Fusobacteriaum nucleatum, and Actinomyces naeslundii were quantitatively determined. The biofilm thickness was found to be between 19.78 and 36.73 μm after 3 days and between 26.11 and 32.43 μm after 5 days. With the exception of Ti-m the biofilm thickness after 3 days was correlated with surface roughness. In addition to Streptococcus spp. as the main component of the biofilm (11.23-25.30%), F. nucleatum, A. naeslundii, and Veillonella spp. were also detected. No significant differences in biofilm composition on the implant surfaces could be observed. In total, the influence of roughness and material on biofilm formation was compensated by biofilm maturation.

PMID: 20725954 [found with GoPubMed]


2: Hannig, Christian; Weinhold, Hans Christian; Becker, Klaus; Attin, Thomas

Diffusion of peroxides through dentine in vitro with and without prior use of a desensitizing varnish.

Clinical oral investigations 2010/Aug, :

Clinic of Conservative Dentistry, Faculty of Medicine 'Carl Gustav Carus', Technical University of Dresden, 01307, Dresden, , Fetscherstr. 74, Germany, christian.hannig@uniklinikum-dresden.de.

Different bleaching regimens are used in dentistry possibly penetrating the dentine and affecting the pulp. The aim of the present study was to investigate peroxide diffusion through dentine pre-treated with a desensitizing varnish (Vivasens(R)) in a standardized in vitro setup during application of different bleaching materials. The penetration was tested using 1.3-mm-thick bovine dentine slabs. The following bleaching materials were tested with and without prior application of the desensitizing varnish on the external side of the dentine slabs: Vivastyle, Whitestrips, Simply White, Opalescence (external bleaching), and sodium perborate (internal bleaching, only tested without varnish; n = 8 samples per subgroup). The penetration of peroxides was measured photometrically using 4-aminoantipyrin as a substrate, the penetration of peroxides was monitored over 240 min. All bleaching agents yielded a diffusion of peroxides through the dentine, the kinetics of penetration were approximately linear for all materials tested. The significantly highest diffusion of peroxides was observed with Opalescence, the lowest with sodium perborate. The adoption of the desensitizing varnish reduced the diffusion of peroxides significantly for all external bleaching materials. Peroxides penetrated the dentine during application of bleaching materials; the penetration of peroxides can be reduced by application of a desensitizing agent.

PMID: 20697758 [found with GoPubMed]


3: Hannig, Matthias; Hannig, Christian

Nanomaterials in preventive dentistry.

Nature nanotechnology 2010/Aug, 5(8):565-9

Clinic of Operative Dentistry, Periodontology and Preventive Dentistry, University Hospital, Saarland University, Building 73, D-66421 Homburg/Saar, Germany. matthias.hannig@uks.eu

The prevention of tooth decay and the treatment of lesions and cavities are ongoing challenges in dentistry. In recent years, biomimetic approaches have been used to develop nanomaterials for inclusion in a variety of oral health-care products. Examples include liquids and pastes that contain nano-apatites for biofilm management at the tooth surface, and products that contain nanomaterials for the remineralization of early submicrometre-sized enamel lesions. However, the treatment of larger visible cavities with nanomaterials is still at the research stage. Here, we review progress in the development of nanomaterials for different applications in preventive dentistry and research, including clinical trials.

PMID: 20581832 [found with GoPubMed]


4: Hannig, C; Spitzmüller, B; Lux, H C; Altenburger, M; Al-Ahmad, A; Hannig, M

Efficacy of enzymatic toothpastes for immobilisation of protective enzymes in the in situ pellicle.

Archives of oral biology 2010/Jul, 55(7):463-9

Clinic of Conservative Dentistry, Technical University of Dresden, Germany. christian.hannig@uniklinikum-dresden.de

AIM: Different enzyme-containing toothpastes are available on the market. The aim of the present in situ study was to investigate their efficacy for immobilisation of protective enzymes in the pellicle layer. METHODS: Pellicle formation took place in situ on bovine enamel slabs fixed to individual upper jaw splints carried by 6 subjects. After pellicle formation for 1 min, brushing was performed for 3 min with the commercially available toothpastes Enzycal, biotène and BioXtra, respectively. Before as well as 0, 20 and 40 min after brushing, samples were removed from the splints and tested for lysozyme, peroxidase and glucoseoxidase activity. The assays for the respective enzyme activities were based on fluorogenic substrates. Separate experiments were conducted for the different enzymes and toothpastes. RESULTS: Brushing with the toothpastes caused an extensive increase of glucoseoxidase activity in the pellicle, but it was of low tenacity whereas peroxidase activity was enhanced considerably. However, targeted accumulation of lysozyme in the pellicle was not very pronounced. Brushing without toothpaste had no effect on enzyme activities in the acquired pellicle. CONCLUSION: Targeted immobilisation of enzymes in the in situ pellicle can be achieved with toothpastes.

PMID: 20417500 [found with GoPubMed]


5: Jung, David Jonathan; Al-Ahmad, Ali; Follo, Marie; Spitzmüller, Bettina; Hoth-Hannig, Wiebke; Hannig, Matthias; Hannig, Christian

Visualization of initial bacterial colonization on dentine and enamel in situ.

Journal of microbiological methods 2010/May, 81(2):166-74

Department of Operative Dentistry and Periodontology, University of Freiburg, Hugstetter Str. 55, D-79106 Freiburg, Germany.

Bacterial colonization of dentine is of high relevance in cariology, endodontology and periodontology. The aim of the present in situ study was to establish recent methods for visualization and quantification of initial bacterial adherence to dentine in comparison to enamel. For this purpose, bovine enamel and dentine slabs were fixed on buccal sites of individual upper jaw splints worn by 6 subjects for 30min, 120min and 360min, respectively. Adherent bacteria on the slabs were visualized and quantified with DAPI-staining (4',6-diamidino-2-phenylindole) and fluorescence in situ hybridization (FISH) of streptococci and eubacteria using the CLSM (confocal laser scanning microscopy) as well as an epifluorescence microscope. In addition, the number of colony forming units was quantified after desorption. Representative samples were processed for SEM (scanning electron microscopy) and TEM (transmission electron microscopy). All methods clearly indicated that a significantly higher number of bacteria adhered to dentine than to enamel. Furthermore, the amount of bacteria on the dentine increased with increasing oral exposure time, but remained rather constant on the enamel. The CLSM allowed visualization of bacteria in the dentinal tubules. Bacteria were found preferentially at the openings of the dentine tubules, but were distributed randomly on the enamel. In conclusion, the adopted methods are suitable for visualization and quantification of bacterial adhesion to dentine. Even the initial bacterial colonization of dentine is much more pronounced than bacterial adherence to the enamel.

PMID: 20211207 [found with GoPubMed]


6: Hannig, Christian; Spitzmüller, Bettina; Hoth-Hannig, Wiebke; Hannig, Matthias

Targeted immobilisation of lysozyme in the enamel pellicle from different solutions.

Clinical oral investigations 2009/Dec, :

Department of Operative Dentistry and Periodontology, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany, christian.hannig@uniklinik-freiburg.de.

Mouthwashes containing protective enzymes are required especially for patients suffering from xerostomia. The present study aimed to investigate the possibilities of modulating the immobilisation of lysozyme in the in situ pellicle layer. In situ formed pellicles were incubated in vitro for 10 min with various enzymatic buffer solutions containing lysozyme and additive enzymes such as transglutaminase or trypsin as well as polyphenolic compounds (cistus tea). After the rinses, the pellicle samples were incubated in collected whole saliva or in desorption solutions for 0, 20 and 40 min and the enzyme activities were measured. Furthermore, accumulation of lysozyme in the pellicle was visualised in ultrathin sections of the pellicle using the gold immunolabelling technique and transmission electron microscopy. Hen egg white lysozyme was accumulated in the in situ pellicle tenaciously. Up to 2.8-fold higher activities than in controls were observed. The addition of transglutaminase did not enhance the immobilisation of lysozyme activity, whereas the polyphenolic compound had no adverse effect. Accumulation of lysozyme in the acquired pellicle was confirmed by gold immunolabelling. Targeted and tenacious immobilisation of lysozyme in the acquired pellicle is possible. Poylphenolic compounds might be a relevant additive for mouthwashes containing lysozyme.

PMID: 19967422 [found with GoPubMed]


7: Hannig, C; Hannig, M

Natural enamel wear--a physiological source of hydroxylapatite nanoparticles for biofilm management and tooth repair?

Medical hypotheses 2010/Apr, 74(4):670-2

Department of Operative Dentistry and Periodontology, University of Freiburg, Hugstetter Str. 55, D-79106 Freiburg, Germany. christian.hannig@uniklinik-freiburg.de

Dental caries is a widespread chronic disease caused by glucolytic biofilms. Despite considerable success in prophylaxis, there is still a strong demand for biomimetic biofilm management. Reflections on the abraded, but mostly caries-free teeth observed in prehistoric sculls or omnivorous primates, respectively, offer perspectives for developing new approaches in preventive dentistry. It is hypothesized that nano-sized hydroxylapatite crystallites occur in the oral cavity during extensive physiological wear of the hierarchical structured enamel surface due to dental abrasion and attrition. These nano-scaled apatite enamel crystallites might promote re-mineralization and physiological biofilm management at the tooth surface. Indeed, modern bioinspired nanomaterials in preventive dentistry containing nano-sized hydroxylapatite particles have shown efficacy in reducing oral biofilm formation and yield re-mineralizing effects. Accordingly, they seem to mimic extensive abrasions which do not occur with modern diet.

PMID: 19962245 [found with GoPubMed]


8: Hannig, C; Spies, B; Spitzmüller, B; Hannig, M

Efficacy of enzymatic mouth rinses for immobilisation of protective enzymes in the in situ pellicle.

Archives of oral biology 2010/Jan, 55(1):1-6

Department of Operative Dentistry and Periodontology, University of Freiburg, Hugstetter Str. 55, D-79106 Freiburg, Germany. christian.hannig@uniklinik-freiburg.de

AIM: Mouth rinses containing enzymes are designed for patients suffering from xerostomia. The objective of the present in situ study was to investigate the efficacy of these rinses for targeted accumulation and immobilisation of protective enzymes in the acquired pellicle. METHODS: A number of six healthy subjects carried bovine enamel slabs fixed on individual upper jaw splints for pellicle formation in situ. After 1 min, they rinsed with biotène or BioXtra for 10 min, respectively. Enzyme activities of lysozyme, peroxidase and glucoseoxidase in the in situ pellicle and in the saliva were assayed before as well as 0, 20 and 40 min after the rinses. The assays for the respective enzyme activities were based on fluorogenic substrates. Separate experiments were performed for the different enzymes and mouth rinses, respectively. Statistical evaluation was carried out with the Kruskal-Wallis test. RESULTS: None of the investigated rinses had any significant impact on the activities of lysozyme, peroxidase and glucoseoxidase detectable in the in situ pellicle or in the saliva (Kruskal-Wallis test, p>0.05). Despite the fact that both products should contain lactoperoxidase activity according to manufacturers' instructions, no peroxidase activity was measurable in the pure mouth rinses. CONCLUSION: With the tested enzymatic mouth rinses targeted accumulation and immobilisation of protective enzymes in the in situ pellicle did not seem possible.

PMID: 19913216 [found with GoPubMed]


9: Hannig, Christian; Follo, Marie; Hellwig, Elmar; Al-Ahmad, Ali

Visualization of adherent micro-organisms using different techniques.

Journal of medical microbiology 2010/Jan, 59(Pt 1):1-7

Department of Operative Dentistry and Periodontology, University of Freiburg, Freiburg, Germany. christian.hannig@uniklinik-freiburg.de

The visualization and quantification of adherent bacteria is still one of the most relevant topics in microbiology. Besides electron microscopic techniques such as transmission electron microscopy, scanning electron microscopy and environmental scanning electron microscopy, modern fluorescence microscopic approaches based on fluorogenic dyes offer detailed insight into bacterial biofilms. The aim of the present review was to provide an overview of the advantages and disadvantages of different methods for visualization of adherent bacteria with a special focus on the experiences gained in dental research.

PMID: 19815663 [found with GoPubMed]


10: Al-Ahmad, Ali; Roth, Dominik; Wolkewitz, Martin; Wiedmann-Al-Ahmad, Margit; Follo, Marie; Ratka-Krüger, Petra; Deimling, Daniela; Hellwig, Elmar; Hannig, Christian

Change in diet and oral hygiene over an 8-week period: effects on oral health and oral biofilm.

Clinical oral investigations 2010/Aug, 14(4):391-6

Department of Operative Dentistry and Periodontology, Albert-Ludwigs-University, Hugstetter Strasse 55, 79106 Freiburg, Germany. ali.al-ahmad@uniklinik-freiburg.de

The aim of the study was to monitor changes in oral health and oral biofilm composition in vivo during an experiment simulating prehistoric lifestyle and diet and poor oral hygiene. Thirteen subjects lived for a period of 8 weeks under Neolithic conditions. The following clinical parameters were recorded before and after the project: gingival and plaque index (Löe and Silness, Acta Odontol Scand 21:533, 1963; Silness and Löe, Acta Odontol Scand 22:121-135, 1964), probing pocket depth, and bleeding upon probing. In addition, supragingival plaque samples were collected both before and after the project and were analysed quantitatively using multiplex fluorescence in situ hybridization and confocal laser scanning microscopy. The following plaque bacteria were evaluated: Streptococcus spp., Veillonella spp., Fusobacterium nucleatum, and Actinomyces naeslundii. The plaque index increased significantly from 1.12 up to 1.55 over the 8-week period (gingival index before, 0.46; after, 0.93; p < 0.05). A strong correlation of both indices was recorded before (r = 0.77) and after (r = 0.83) participation in the study. Each of the children in the study showed a progression of carious lesions and/or new areas of demineralisation. The probing pocket depth and bleeding upon probing were not affected. All subjects yielded an intra-individual shift in biofilm composition. The proportion of F. nucleatum decreased across all subjects. The proportion of Veillonella spp. increased among the children. Poor oral hygiene and change of diet lead to an increase in oral plaque and gingival inflammation. The inter-individual comparison indicated a shift in bacterial composition.

PMID: 19626350 [found with GoPubMed]


11: Al-Ahmad, Ali; Follo, Marie; Selzer, Ann-Carina; Hellwig, Elmar; Hannig, Matthias; Hannig, Christian

Bacterial colonization of enamel in situ investigated using fluorescence in situ hybridization.

Journal of medical microbiology 2009/Oct, 58(Pt 10):1359-66

Department of Operative Dentistry and Periodontology, University of Freiburg, Hugstetter Strasse 55, D-79106 Freiburg, Germany.

Oral biofilms are one of the greatest challenges in dental research. The present study aimed to investigate initial bacterial colonization of enamel surfaces in situ using fluorescence in situ hybridization (FISH) over a 12 h period. For this purpose, bovine enamel slabs were fixed on buccal sites of individual splints worn by six subjects for 2, 6 and 12 h to allow biofilm formation. Specimens were processed for FISH and evaluated with confocal laser-scanning microscopy, using probes for eubacteria, Streptococcus species, Veillonella species, Fusobacterium nucleatum and Actinomyces naeslundii. The number of adherent bacteria increased with time and all tested bacterial species were detected in the biofilm formed in situ. The general percentage composition of the eubacteria did not change over the investigated period, but the number of streptococci, the most frequently detected species, increased significantly with time (2 h: 17.7+/-13.8 %; 6 h: 20.0+/-16.6 %; 12 h: 24.7+/-16.1 %). However, < or =1 % of the surface was covered with bacteria after 12 h of biofilm formation in situ. In conclusion, FISH is an appropriate method for quantifying initial biofilm formation in situ, and the proportion of streptococci increases during the first 12 h of bacterial adherence.

PMID: 19528150 [found with GoPubMed]


12: Hannig, Christian; Kupilas, Florian Jan; Wolkewitz, Martin; Attin, Thomas

[Validity of decision criteria for replacement of fillings]

Schweizer Monatsschrift für Zahnmedizin = Revue mensuelle suisse d'odonto-stomatologie = Rivista mensile svizzera di odontologia e stomatologia / SSO 2009, 119(4):328-38

Abteilung für Zahnerhaltungskunde und Parodontologie der Universität Freiburg, Hugstetterstr. 55, D-79106 Freiburg. christian.hannig@uniklinik-freiburg.de

One of the main treatments in dental practice is the exchange of restorations due to secondary or residual caries. Thereby, only restorations indeed infected with secondary or residual caries should be renewed. The aim of the study was to check the validity of different criteria for the replacement of fillings. Three hundred seventeen replacements of dental restorations were evaluated retrospectively by using an examination form. Different clinical parameters were correlated with the finding of caries after removal of the old restoration. Clinical findings were differentiated between caries soft to probing, caries only stainable with caries detector and caries-free cavities. Sixty-seven percent of the cavities showed caries that could be probed, 16.1% were just stainable with caries detector and 17% were caries-free. In general, results of previous replacements of fillings were a valid criterion. Other indicators for caries-free cavities were properly placed fillings with a correctly reconstructed morphology, fillings without marginal defects, a low age of the filling and a positive impression of the patients' general hygiene. Indicators for cavities with secondary caries were marginal gaps, pain within the respective section of the jaw, a high number of filled surfaces and a bad impression of the general hygiene. Systematic diagnostic criteria should be adopted in decision making on replacement of fillings in order to avoid new restorations of caries-free cavities.

PMID: 19485073 [found with GoPubMed]


13: Hannig, Christian; Sorg, Julia; Spitzmüller, Bettina; Hannig, Matthias; Al-Ahmad, Ali

Polyphenolic beverages reduce initial bacterial adherence to enamel in situ.

Journal of dentistry 2009/Jul, 37(7):560-6

Department of Operative Dentistry and Periodontology, University of Freiburg, Hugstetter Str. 55, D-79106 Freiburg, Germany. christian.hannig@uniklinik-freiburg.de

OBJECTIVES: Polyphenols are antibacterial and anti-oxidative natural agents. The present in situ study aimed to investigate the effect of different polyphenolic beverages on initial bacterial adherence to enamel in the oral cavity. METHODS: Initial biofilm formation was performed on bovine enamel specimens mounted buccally on individual upper jaw splints and carried by six subjects. After 1 min of pellicle formation, oral rinses with black tea, green tea, grape juice, Cistus tea or red wine were performed for 10 min. Afterwards the slabs were carried for another 19 or 109 min, respectively. Samples exposed to the oral fluids for 30 and 120 min served as controls. Following intraoral exposure, the slabs were rinsed with saline solution. The amount of adherent bacteria was determined with DAPI-staining (4',6-diamidino-2-phenylindole) and with fluorescence-in situ hybridization (FISH) of eubacteria and streptococci. RESULTS: Rinses with all beverages reduced the amount of detectable bacteria. Lowest number of adherent bacteria was found following rinses with red wine, Cistus tea and black tea as measured with DAPI (up to 66% reduction of adherent bacteria vs. controls). Also FISH revealed significant impact of most tested beverages. CONCLUSIONS: Rinses with certain polyphenolic beverages as well as consumption of these foodstuffs may contribute to prevention of biofilm induced diseases in the oral cavity.

PMID: 19394124 [found with GoPubMed]


14: Hannig, C; Berndt, D; Hoth-Hannig, W; Hannig, M

The effect of acidic beverages on the ultrastructure of the acquired pellicle--an in situ study.

Archives of oral biology 2009/Jun, 54(6):518-26

Department of Operative Dentistry and Periodontology, University of Freiburg, Hugstetter Str. 55, D-79106 Freiburg, Germany.

AIM: The aim of the present in situ study was to investigate ultrastructural alterations as well as protective properties of the pellicle layer during consumption of acidic beverages. METHODS: Bovine enamel slabs were fixed on buccal and palatal aspects of individual splints and exposed in the oral cavities of three subjects for 120 min. In the following, the subjects drank orange juice, coke light or sprite light. Half of the specimens were removed afterwards, the others were exposed to the oral fluids for another 120 min. Erosive alterations of the bovine enamel slabs were measured by determination of the Knoop-micro-hardness. In addition, the ultrastructure of the pellicle was evaluated by transmission electron microscopy (TEM). RESULTS: Determination of Knoop-micro-hardness yielded only little reduction of the relative Knoop-hardness in situ during consumption of sprite light (-0.053+/-0.019) and coke light (-0.075+/-0.04). With orange juice nearly no change of the hardness was recorded. TEM-pictures showed that the globular outer layers of the pellicle were removed to a different extent according to the localisation of the specimens in the oral cavity, whereas the basal pellicle was not affected by the acidic beverages. On the specimens carried for another 120 min after the erosive attack, lacunae filled with organic structures were observed underneath the basal side of the pellicle. CONCLUSION: During fast consumption of acidic beverages in situ, the erosive effects on pellicle coated bovine enamel are moderate and juices seem to be less harmful as compared with low pH soft drinks. Pellicle proteins in eroded lacunae may impact the remineralization process.

PMID: 19327752 [found with GoPubMed]


15: Hannig, C; Spitzmüller, B; Hannig, M

Transaminases in the acquired pellicle.

Archives of oral biology 2009/May, 54(5):445-8

Department of Operative Dentistry and Periodontology, University of Freiburg, Hugstetter Str. 55, D-79106 Freiburg, Germany. christian.hannig@uniklinik-freiburg.de

OBJECTIVE: Transaminases (AST, aspartate amino transferase; ALT, alanine amino transferase) are relevant enzymes in physiology and pathology of the human organism. The aim of the present in situ study was to demonstrate the presence of these enzymes in the enamel pellicle. METHODS: Bovine enamel slabs were fixed on buccal sites of individual upper jaw splints and worn for 3, 30 and 120 min by 5 subjects to allow pellicle formation. The in situ pellicles were tested for AST and ALT. Enzyme activities were measured photometrically via determination of the products pyruvate and oxalacetate using lactate-dehydrogenase and malate-dehydrogenase, respectively. RESULTS: Enzymatic AST- as well as ALT-activities are present in the acquired pellicle within 3 min. The enzyme activities exposed at the pellicles' surfaces increased slightly with the pellicle formation time (ANOVA, AST: n.s., ALT: p=0.021). However, the two enzymes show considerable intraindividual and interindividual variability. The mean AST-activity of the pellicle amounted to 1.07+/-0.81 mU/cm(2) (ALT 1.18+/-0.52 mU/cm(2)). The ALT-activity of the centrifuged saliva was 26.62+/-11.09 mU/ml (AST 35.98+/-29.35 mU/ml). CONCLUSIONS: AST as well as ALT are present in the in situ pellicle layer and may contribute to the intrinsic maturation of pellicle proteins.

PMID: 19321161 [found with GoPubMed]


16: Hannig, Christian; Hannig, Matthias

The oral cavity--a key system to understand substratum-dependent bioadhesion on solid surfaces in man.

Clinical oral investigations 2009/Jun, 13(2):123-39

Department of Operative Dentistry and Periodontology, University of Freiburg, Freiburg, Germany. christian.hannig@uniklinik-freiburg.de

One of the greatest challenges in life sciences and biomaterials research is adhesion of biomolecules and bacteria to solid surfaces in aqueous solutions. An example concerning everybody is biofilm formation in the oral cavity on dental materials and dental hard substances, respectively. The main characteristics typical for any bioadhesion can be observed excellently in the oral cavity. Initially, a proteinaceous layer termed pellicle is formed. It mediates the interactions between solid substrata, oral fluids and microorganisms. Numerous different materials with differing physico-chemical properties and possible impact on the acquired pellicle are present in the oral cavity such as enamel, dentine, restorative materials or dental implants. Despite the fact that in vitro studies demonstrate considerable differences of experimental pellicles formed on these materials, the in situ pellicles seem to be relatively similar and level off the different properties of the underlying substrates. However, the bacterial colonisation of pellicle-coated surfaces under in vivo conditions differs considerably. Long-range forces and detachment of biofilm layers may account for this phenomenon despite the masking effect of the pellicle. Accordingly, low-energy surfaces are desirable for restorative materials exposed to the oral cavity to minimise bacterial adhesion. The oral cavity is an easy accessible in vivo model for understanding bioadhesion and for investigation of protein-surface interactions noninvasively. For evaluation of biofilm formation on dental materials, in situ or in vivo studies are preferable.

PMID: 19137331 [found with GoPubMed]


17: Hannig, Christian; Becker, Klaus; Yankeu-Ngalene, Valerie Estelle; Attin, Thomas

Applicability of common methods for short time erosion analysis in vitro.

Oral health & preventive dentistry 2008, 6(3):239-48

Department of Operative Dentistry and Periodontology, University of Freiburg, Hugstetter Strasse 55, D-79106 Freiburg, Germany. Christian.hannig@uniklinik-freiburg.de

PURPOSE: Dental erosion can be measured by different methods. The aim of the present study was to check the applicability of common methods to determine initial erosive effects. MATERIALS AND METHODS: Enamel surfaces (4.5 mm2) were eroded in vitro by treatment with hydrochloric acid (pH 2, 2.3 and 2.6) for 5 to 60 s or 240 s, respectively. Erosive effects were assayed with three different methods: Knoop's diamond indentation, profilometry and the determination of the dissolved calcium ions (Ca2+) in a colorimetric assay based on the arsenazo-III-reaction. RESULTS: Erosive mineral loss of > 1 microm are measurable with profilometry. This corresponds to the erosive effects that occur after 60 s or more. Profilometric data yielded variance of up to 50%. Knoop's diamond indentation also showed some limitations: the depth of indentation reached a plateau after 30 to 120 s and the measurements showed variance of up to 85%. With the colorimetric assay, short time erosive effects occurring within 5 s could be assessed precisely and kinetically. The method allowed small amounts of 400 pmol Ca2+ per well to be quantified in small volumes with little variability. CONCLUSIONS: For evaluation and quantification of short time erosive effects, the colorimetric method is superior to diamond indentation and profilometry.

PMID: 19119579 [found with GoPubMed]


18: Hannig, Christian; Spitzmüller, Bettina; Hannig, Matthias

Characterisation of lysozyme activity in the in situ pellicle using a fluorimetric assay.

Clinical oral investigations 2009/Mar, 13(1):15-21

Department of Operative Dentistry and Periodontology, University of Freiburg, Freiburg, Germany. Christian.hannig@uniklinik-freiburg.de

Lysozyme is among the most protective enzymes in the pellicle layer. The aim of the present study was to establish a precise fluorimetric assay for determination and characterisation of lysozyme activity immobilised in the initial in situ formed pellicle. For in situ pellicle formation, bovine enamel slabs were fixed on maxillary splints and carried by six subjects for different times (3, 30 min) on buccal and palatal sites. The enzymatic assay was based on hydrolysis of cell walls from Micrococcus lysodeicticus linked to a fluorogenic substance. When the substrate is hydrolysed, a fluorescing product is released. Furthermore, the effects of chlorhexidine and black tea on lysozyme in the in situ pellicle were investigated. The fluorimetric method allowed direct determination of the enzyme activity with the slab inside the well of a microtiter plate. The mean immobilised activity over all samples amounted to 68.67 +/- 27.35 U/cm(2) (desorbed activity = 46.76 +/- 21.18 U/cm(2)). The enzyme activity exposed at the pellicles' surfaces increased in a time-dependant manner and showed a Michaelis-Menten kinetic. Chlorhexidine and black tea reduced lysozyme activity of the in situ pellicle significantly. After rinsing with tea or chlorhexidine, V(max) was reduced, whereas K(m) remained unaffected indicating a negative allosteric effect of the V type. The fluorimetric method is appropriate for determination of pellicle lysozyme activity. The influence of effectors on immobilised lysozyme activity can be monitored.

PMID: 18810509 [found with GoPubMed]


19: Hahn, Wolfram; Fricke-Zech, Susanne; Fricke, Julia; Gruber, Rudolf M; Dullin, Christian; Zapf, Antonia; Hannig, Christian; Kubein-Meesenburg, Dietmar; Sadat-Khonsari, Reza

Detection and size differentiation of simulated tooth root defects using flat-panel volume computerized tomography (fpVCT).

Oral surgery, oral medicine, oral pathology, oral radiology, and endodontics 2009/Feb, 107(2):272-8

Department of Orthodontics, Georg-August-University of Göttingen, Robert-Koch-Strasse 40, Goettingen, Germany. weahahn@aol.com

OBJECTIVE: Our aim was to evaluate the capacity of flat-panel volume computerized tomography (fpVCT) to enable the observer to detect and differentiate 3 different sizes of simulated tooth root defects in radiographs. STUDY DESIGN: Three simulated tooth root defects of different sizes and a defect-free area (160 sites in total) were randomly distributed on the buccal and lingual surface of 20 mandibular premolar roots of Sus scrofa domestica with round burs. For the imaging of the specimens, an fpVCT prototype was used. Findings were evaluated by 3 observers. RESULTS: Cavity 0 (no lesion) was correctly identified in 53%, cavity 1 in 69%, cavity 2 in 96%, and cavity 3 in 89%. Altogether, the simulated cavities were classified in a correct manner in 77%. The values were compared using receiver operating characteristic curves. The area under the curve (AUC) for cavity 0 versus the pooled results for cavities 1-3 was found to be 0.72. The AUC for the pooled results for 0-2 (no pathologic impact) versus cavity 3 (potential pathologic impact) was 0.94. There was no significant dependence of the results on the observer (P = .37). Results with P < .05 were considered to be significant. CONCLUSIONS: Flat-panel volume computerized tomography, which is currently used only as a research tool, has a high potential in detection and differentiation at an early stage of external root resorption cavities with pathologic relevance..

PMID: 18602316 [found with GoPubMed]


20: Ziebolz, Dirk; Hannig, Christian; Attin, Thomas

Influence of a desensitizing agent on efficacy of a paint-on bleaching agent.

American journal of dentistry 2008/Apr, 21(2):77-82

Department of Operative Dentistry, Preventive Dentistry and Periodontology, University of Goettingen, Germany. dirk.ziebolz@zm-goettingen.de

PURPOSE: To evaluate the influence of a desensitizing agent (VivaSens) on efficacy of a paint-on bleaching agent (VivaStyle Paint On Plus). METHODS: Bleaching was performed for 7 days with VivaStyle Paint On Plus. The varnish was applied twice a day for 10 minutes each. 80 subjects were included in the study and randomly distributed in two groups (n = 40) according to exposed cervical dentin and perceived hypersensitivities. Group A used VivaStyle without VivaSens while Group B used VivaStyle Paint On Plus after a single application of VivaSens. Tooth color was assessed on facial surfaces of first upper incisors with Vita shade guide at baseline and 10 days after bleaching therapy. Sensitivity, with intensity graded from 0 (no sensitivity) to 10 (high sensitivity), was assessed chair-side using a blow of air at baseline, at the end of therapy (7 days) and 10 days after bleaching therapy. Statistical evaluation was performed with non parametric ANOVA. RESULTS: Thirteen subjects dropped out of the study; six due to gingival burning sensation (A: 3; B: 3) related to the bleaching regimen and seven due to lack of compliance. Directly after completion of bleaching therapy, tooth color had changed significantly compared to baseline in both treatment groups without difference among the groups. Color changes (Delta) according to Vita shade guide were as follows (mean +/- standard deviation): Group A: Delta 2.7 +/- 1.0, Group B: Delta 2.8 +/- 0.9. After bleaching (7 days) the intensity of tooth hypersensitivity (mean +/- standard deviation) was increased significantly compared to baseline in both groups (P < 0.05): Group A: 1.58 +/- 1.91 (baseline: 0.4 +/- 0.5); Group B: 1.3 +/- 1.8 (baseline: 0.5 +/- 0.7). The number of subjects reporting tooth hypersensitivity increased in Group A by 5 (n = 13) and in Group B by 1 (n = 10) subject. Although degree of hypersensitivities and number of subjects with hypersensitivities were lower in Group B, there was no significant difference between the groups.

PMID: 18578172 [found with GoPubMed]


21: Hannig, C; Ruggeri, A; Al-Khayer, B; Schmitz, P; Spitzmüller, B; Deimling, D; Huber, K; Hoth-Hannig, W; Bowen, W H; Hannig, M

Electron microscopic detection and activity of glucosyltransferase B, C, and D in the in situ formed pellicle.

Archives of oral biology 2008/Nov, 53(11):1003-10

Department of Operative Dentistry and Periodontology, University of Freiburg, Hugstetter Str. 55, D-79106 Freiburg, Germany. christian.hannig@uniklinik-freiburg.de

OBJECTIVE: Glucosyltransferases (GTFs) represent a virulence factor of mutans streptococci. The aim of the present in situ study was to investigate the distribution of different GTF-isoforms in the pellicle. DESIGN: Bovine enamel slabs were fixed on buccal and palatal sites of individual splints worn by five subjects for 30 and 120 min to allow pellicle formation. Pellicle specimens were processed for transmission electron microscopy (TEM) and field emission in-lens scanning electron microscopy (FEI-SEM). Gold-immunolabelling was used for detection of GTF-isoforms B, C and D. Furthermore, glucosyltransferase activity of 3-, 30- and 120-min pellicles was tested via determination of fructose release. RESULTS: All isoforms of the enzyme were found to be randomly distributed within all layers of the pellicle. In cross-sections (TEM), GTF D was the most abundant isoform. More labelled molecules were detected on buccal sites compared with palatal surfaces, the number of molecules detected increased with time. The amount of GTF B, C and D found on the pellicle surface by FEI-SEM showed no correlation with pellicle formation time or localisation in the oral cavity. Overall, GTF D was detected more frequently on the surface than GTF B and C. All pellicles tested showed GTF-activity. CONCLUSION: The study shows for the first time the presence of the GTF-isoforms B, C and D within all layers of the in situ formed pellicle. This emphasises the impact of streptococcal products on the composition of the pellicle and illustrates a mechanism used by bacteria to colonize dental surfaces.

PMID: 18513702 [found with GoPubMed]


22: Hannig, Christian; Spitzmüller, Bettina; Al-Ahmad, Ali; Hannig, Matthias

Effects of Cistus-tea on bacterial colonization and enzyme activities of the in situ pellicle.

Journal of dentistry 2008/Jul, 36(7):540-5

Department of Operative Dentistry and Periodontology, University of Freiburg, Hugstetter Strasse 55, 79106 Freiburg, Germany. Christian.hannig@uniklinik-freiburg.de

OBJECTIVES: Polyphenols are expected to have antibacterial properties. Cistus is a tea rich in polyphenols. The aim of the present in situ study was to investigate the effect of Cistus-tea on the pellicle and on the initial oral biofilm. METHODS: For in situ pellicle formation and initial biofilm formation, bovine enamel slabs were fixed on maxillary splints and carried by four subjects at buccal sites for up to 2 h. Bacteria present in 120-min pellicles were determined with DAPI-staining and fluorescence in situ hybridization with and without a 10 min rinse with Cistus-tea performed 1 min after incorporation of the slabs. In addition, amylase, lysozyme, glucosyltransferase and peroxidase activities immobilised in the pellicle layer were measured before and after rinsing for 10 min with Cistus-tea. RESULTS: The amount of bacteria detected in the 120-min biofilm was reduced significantly, if a 10 min rinse with Cistus-tea was performed one min after insertion of the enamel slabs. DAPI-staining yielded 13.2+/-3.5 for controls and 6.5+/-1.1 x 10(4) bacteria/cm(2), if a rinse with Cistus-tea was applied. Lysozyme, amylase and glucosyltransferase activities immobilised in the pellicle were not affected following a rinse with Cistus-tea. However, peroxidase activity was reduced significantly. CONCLUSIONS: Cistus-tea may be used to reduce the initial bacterial adhesion in the oral cavity.

PMID: 18468764 [found with GoPubMed]


23: Hannig, Christian; Spitzmüller, Bettina; Knausenberger, Stefan; Hoth-Hannig, Wiebke; Hellwig, Elmar; Hannig, Matthias

Detection and activity of peroxidase in the in situ formed enamel pellicle.

Archives of oral biology 2008/Sep, 53(9):849-58

Department of Operative Dentistry and Periodontology, University of Freiburg, Hugstetter Str. 55, D-79106 Freiburg, Germany. christian.hannig@uniklinik-freiburg.de

AIM: Peroxidase is the main salivary antioxidant. The aim of the present study was to detect and to characterise peroxidase in the in situ enamel pellicle. METHODS: Bovine enamel slabs were fixed on maxillary splints and carried by six subjects for different times (3, 30 and 120 min) on buccal and palatal sites. Pellicle bound peroxidase activity was determined fluorimetrically using 2',7'-dichlorofluorescin as a substrate. The peroxidase molecules present in the pellicle were visualised with the gold-immunolabelling technique and evaluated by TEM. Furthermore, effects of polyphenols and hydrogen peroxide on peroxidase and its enzymatic activity were examined. RESULTS: All pellicles which were tested revealed peroxidase activity and labelled peroxidase molecules were detected in all samples. The numbers of gold-labelled peroxidase molecules detectable in cross-sections of the pellicles were correlated significantly with the pellicle formation time. After 3 min, 0.50+/-1.01 labelled molecules were detected (30 min: 1.42+/-1.98; 120 min: 4.15+/-4.13, ANOVA, p<0.001). The mean immobilised peroxidase activity exposed at the surface amounted to 24.4+/-27.7 mU/cm2; no continuous increase of activity with formation time was found. Hydrogen peroxide and polyphenolic beverages inactivated peroxidase activity of the pellicle. Despite these inhibiting effects, considerable amounts of peroxidase molecules were still detectable by gold-immunolabelling. After contact with the inhibiting agents in situ, peroxidase activity of the pellicle reconstituted slowly. CONCLUSION: Peroxidase activity is present in the pellicle already after 3 min of formation time, but is inhibited by the substrate and polyphenolic beverages.

PMID: 18423562 [found with GoPubMed]


24: Hannig, C; Spitzmüller, B; Miller, M; Hellwig, E; Hannig, M

Intrinsic enzymatic crosslinking and maturation of the in situ pellicle.

Archives of oral biology 2008/May, 53(5):416-22

Department of Operative Dentistry and Periodontology, University of Freiburg, Hugstetter Street 55, D-79106 Freiburg, Germany. christian.hannig@uniklinik-freiburg.de

AIM: The acquired enamel pellicle is a proteinaceous layer formed on all solid substrata exposed to the oral cavity. It has been supposed that the pellicle undergoes maturation after protein adsorption. The aim of the present study was to investigate enzyme activities with an impact on intrinsic maturation processes in in situ formed pellicles. METHODS: Bovine enamel specimens were exposed to the oral cavity in six subjects to allow in situ pellicle formation over 3, 30 and 120 min. The slabs were fixed on the buccal and palatal surfaces of individual splints fixed with silicone impression material. After rinsing with deionised water, the pellicle samples were tested fluorimetrically for transglutaminase, protease and elastase activity. Phosphatase activities were tested photometrically. Separate samples were used for each of the enzymes tested. RESULTS: Transglutaminase was detected in in situ pellicle (16.7+/-21.2 mU/cm(2)) as was alkaline phosphatase activity (0.87+/-0.99 mU/cm(2)). For both enzymes, there was no correlation of enzyme activities with time or localisation of pellicle formation. Acidic phosphatase- and protease-activities were not detectable. Only traces of elastase activity were found in 57% of the samples. CONCLUSION: Transglutaminase and phosphatase activity are detectable within in situ pellicle. Enzymatic crosslinking and dephosphorylation appear more important for intrinsic maturation of the acquired enamel pellicle than proteolysis.

PMID: 18207133 [found with GoPubMed]


25: Hannig, C; Hannig, M; Rehmer, O; Braun, G; Hellwig, E; Al-Ahmad, A

Fluorescence microscopic visualization and quantification of initial bacterial colonization on enamel in situ.

Archives of oral biology 2007/Nov, 52(11):1048-56

Department of Operative Dentistry and Periodontology, University of Freiburg, Hugstetter Street 55, D-79106 Freiburg, Germany. Christian.hannig@uniklinik-freiburg.de

OBJECTIVE: The acquired salivary pellicle has been defined as proteinaceous film free of bacteria. However, due to the large numbers of microorganisms existent in the oral fluids, it is conceivable that adherent bacteria are already present in the initial pellicle. The aim of this in situ study was to visualize and to quantify these bacteria. DESIGN: Initial biofilm formation was performed on bovine enamel slabs mounted buccally on individual splints and carried in situ by six subjects for 3, 30 and 120 min, respectively. After intraoral exposure, the slabs were rinsed with saline solution and the adherent bacteria were investigated with the following fluorescence microscopic methods: staining with 4',6-diamidino-2-phenylindole (DAPI), staining of vital and nonvital bacteria with fluoresceinediacetate and ethidiumbromide (live/dead staining) and fluorescence in situ hybridization (FISH) of eubacteria and streptococci, respectively. In addition, determination of colony forming units after ultrasonically induced detachment of bacteria was performed. RESULTS: With all the methods, bacteria were detected in the initial in situ biofilm irrespective of the formation time. The numbers of bacteria revealed high intraindividual and interindividual variability and the microorganisms were distributed randomly in small aggregates. The results of the epifluorescence microscopic techniques corresponded well. The mean number of adherent bacteria detected was in the range of 10-20x10(4)cm(-2). CONCLUSION: Already after 3 min, adherent bacteria are present in the initial pellicle. For the first time, DAPI-staining as well as FISH have proven success for visualization of initial intraoral colonization of enamel specimens.

PMID: 17603998 [found with GoPubMed]


26: Hannig, Christian; Lindner, Dirk; Attin, Thomas

Efficacy and tolerability of two home bleaching systems having different peroxide delivery.

Clinical oral investigations 2007/Dec, 11(4):321-9

Department of Operative Dentistry and Periodontology, University of Freiburg, Hugstetter Str 55, 79102 Freiburg, Germany. christian.hanning@uniklinik-freiburg.de

The aim of this study was to investigate tooth whitening efficacy and oral side effects during bleaching with Whitestrips (WS) (6% hydrogen peroxide H(2)O(2) gel) and Vivadent Vivastyle (VS) (10% carbamide peroxide gel). Forty-seven subjects were included in this single blind, randomized, parallel group study. Application of WS was performed twice a day for 30 min. Trays filled with VS were worn for 60 min once a day. Tooth color was evaluated by measuring L*a*b* values before the study and after completion of the bleaching. Treatment tolerability was monitored throughout bleaching with an 8-week follow-up after completion of therapy. After 2 weeks both treatment groups demonstrated significant improvements in tooth color compared to baseline. A shift toward less yellow (-Deltab) and brighter (+DeltaL) tooth color was observed. Deltab amounted to -1.69 +/- 0.38 for WS and -1.20 +/- 0.34 for VS (mean value +/- SE). DeltaL was +1.55 +/- 0.41 for WS and +1.20 +/- 0.37 for VS. There was no significant difference between the two systems. No significant differences between the two bleaching systems were recorded for clinically observed signs or reported symptoms. Gingival irritation was observed in 13%, reported tooth hypersensitivities in 22% and reported gum irritation in 20% of the total study population. At an 8-week follow-up visit no adverse effects were observed. Both WS and VS demonstrated significant and comparable levels of tooth color improvement after 2 weeks. Each treatment caused similar levels of transient oral side effects.

PMID: 17593406 [found with GoPubMed]


27: Hannig, Christian; Huber, Karin; Lambrichts, Ivo; Gräser, Jan; D'Haen, Jan; Hannig, Matthias

Detection of salivary alpha-amylase and lysozyme exposed on the pellicle formed in situ on different materials.

Journal of biomedical materials research. Part A 2007/Oct, 83(1):98-103

Department of Operative Dentistry and Periodontology, University of Freiburg, Hugstetter Street 55, D-79106 Freiburg, Germany. christian.hannig@uniklinik-freiburg.de

Amylase and lysozyme are components of the salivary pellicle, exposing considerable enzymatic activity in the immobilized state. The purpose of the present study was to elucidate the influence of different solid substrata on the amount and distribution of amylase and lysozyme exposed on the surface of the salivary pellicle formed in situ. Slabs of titanium, feldspar ceramic, and bovine enamel were fixed on the buccal sites of individual splints worn by three subjects for 3 or 30 min, respectively, to allow pellicle formation. Subsequently, slabs were removed from the splints and rinsed with running water. Detection of amylase and lysozyme was performed by FEI-SEM after gold-immunolabeling of the enzymes. Both enzymes were found to be distributed randomly at the pellicle surface. Irrespective of formation time and substratum, significantly more labeled lysozyme molecules (5.23 +/- 4.5 microm(-2)) were detected compared with amylase (3.4 +/- 2.9 microm(-2)). Neither the substratum nor the pellicle formation time had significant impact on the amount of the respective enzyme that could be detected. This study for the first time provides evidence, that amylase and lysozyme are exposed at the surface of the salivary pellicle formed in situ on titanium and ceramics. Both enzymes are distributed randomly on the surface of the pellicle, irrespective of the underlying substratum.

PMID: 17380501 [found with GoPubMed]


28: Deimling, Daniela; Hannig, Christian; Hoth-Hannig, Wiebke; Schmitz, Philipp; Schulte-Mönting, Jürgen; Hannig, Matthias

Non-destructive visualisation of protective proteins in the in situ pellicle.

Clinical oral investigations 2007/Sep, 11(3):211-6

Department of Operative Dentistry and Periodontology, Albert Ludwigs University of Freiburg, Freiburg, Germany.

Several salivary anti-microbial and buffering components are part of the acquired in vivo pellicle. The purpose of the present in situ study was to visualise these proteins within the in situ formed pellicle and to investigate their distribution with respect to pellicle formation time and intra-oral localisation. Bovine enamel slabs were fixed on individual splints. They were carried by 6 subjects buccally and palatally in the region of the upper first molar teeth over 30 and 120 min, respectively, for in situ pellicle formation. After intra-oral exposure, enamel specimens were processed for transmission electron microscopy. Secretory immunoglobulin A (sIgA), lactoferrin, lysozyme, carbonic anhydrase (CA) I and II were visualised successfully in the in situ pellicle layer by gold immuno-labelling. All components were found to be distributed randomly within all layers of the pellicle. Significantly higher amounts of the proteins were detected after 120 min of formation time. Furthermore, significantly more labelled lactoferrin and lysozyme were found on buccal surfaces compared with palatal sites. For CA I, CA II and sIgA, no significant influence of the localisation was detected. All investigated anti-bacterial and buffering proteins are distributed randomly in the in situ formed pellicle layer and thus could contribute to its protective properties as an early defence barrier.

PMID: 17361451 [found with GoPubMed]


29: Lennon, Aine M; Wiegand, Annette; Buchalla, Wolfgang; Wahl, Britta; Werner, Carola; Betke, Herbert; Hannig, Christian; Rödig, Tina; Attin, Thomas

Subjectivity and examiner experience in diagnosis of residual caries--an in vitro study.

Schweizer Monatsschrift für Zahnmedizin = Revue mensuelle suisse d'odonto-stomatologie = Rivista mensile svizzera di odontologia e stomatologia / SSO 2007, 117(2):123-7

Clinic for Preventive Dentistry, Periodontology and Cariology, University of Zürich, Switzerland. aine.lennon@zzmk.unizh.ch

The aim was to evaluate subjectivity (using inter- and intraexaminer repeatability), the effect of examiner experience, and residual caries diagnostic accuracy with visual tactile (VT) criteria and using a caries disclosing agent (CD). Thirty teeth with occlusal caries were excavated by a single operator not involved in the diagnostic part of the study. A test area was marked in each cavity. Four dentists with more than five and five dentists with less than five years' experience rated the marked area twice (a week apart) using VT criteria. A week later, the samples were stained using Caries Detector. The same examiners rated the presence or absence of stain in the marked area twice (a week apart). Undecalcified thin slices were examined for bacteria using light microscopy. Overall kappa for inter-examiner repeatability was higher for CD (0.45) than VT (0.31). In the less experienced group the kappa value was higher for CD (0.41) than for VT (0.23). In the experienced group kappa was lower for CD (0.43) than for VT (0.46). Median kappa for intra-examiner repeatability was higher for caries detector (0.77, 0.53) compared to visual tactile (0.52, 0.34) for the more and less experienced examiners respectively. There was no significant difference between the experienced and the inexperienced group in combined sensitivity and specificity (mean) for VT (0.52, 0.53) or CD (0.60, 0.58). In conclusion: VT was more subjective than CD, except for experienced examiners who had a higher inter-examiner repeatability for VT than CD. Diagnostic accuracy for residual caries does not increase with experience.

PMID: 17345999 [found with GoPubMed]


30: Ziebolz, Dirk; Helms, Kristina; Hannig, Christian; Attin, Thomas

Efficacy and oral side effects of two highly concentrated tray-based bleaching systems.

Clinical oral investigations 2007/Sep, 11(3):267-75

Department of Operative Dentistry, Preventive Dentistry and Periodontology, Georg-August University of Goettingen, Robert-Koch Str 40, 37075, Goettingen, Germany. dirk.ziebolz@zm-goettingen.de

The aim of this study was to investigate the tooth-whitening efficacy and oral side effects of the two tray-based bleaching systems Visalys whitening (VW) and Opalescence PF (OP). A stratified, randomised distribution of the subjects (n = 60) to two treatment groups was performed according to baseline tooth brightness (L* values) as determined by colourimeter and to the criteria smoker/non-smoker. Tooth colour was evaluated by measuring L*a*b* values generated from standardised digital image analysis with Adobe Photoshop of the facial surfaces of the right central maxillary incisor. Tooth hypersensitivity, with intensity graded from 0 (no hypersensitivity) to 10 (high hypersensitivity), was assessed chair-side using an air syringe. After bleaching therapy, both treatment groups demonstrated significant improvements in tooth colour (p < or = 0.05). A shift towards less yellow (-Deltab*) and brighter (+DeltaL*) tooth colour was observed. Deltab* was significantly higher in the OP group in comparison to the VW group, DeltaL* showed no significant difference between the both treatment groups (p < or = 0.05). After bleaching, the intensity of tooth hypersensitivity was increased significantly compared to baseline in both groups (p < or = 0.05), with no significant difference between the both groups. Both highly concentrated bleaching systems are effective as tooth-whitening systems, with few reported side effects such as transient tooth hypersensitivity.

PMID: 17333304 [found with GoPubMed]


31: Hannig, Christian; Becker, Klaus; Häusler, Nico; Hoth-Hannig, Wiebke; Attin, Thomas; Hannig, Matthias

Protective effect of the in situ pellicle on dentin erosion - an ex vivo pilot study.

Archives of oral biology 2007/May, 52(5):444-9

Department of Operative Dentistry and Periodontology, University of Freiburg, Hugstetter Str. 55, D-79106 Freiburg, Germany. christian.hannig@uniklinik-freiburg.de

AIM: The acquired pellicle is well known as an anti-erosive proteinaceous layer on enamel, but its protective properties on dentin have not been investigated in detail until now. The aim of the present ex vivo study was to evaluate the erosive effects on pellicle coated dentin. METHODS: Bovine dentin slabs were exposed to the oral cavity of one subject for 120 min for in situ pellicle formation. Subsequently, the slabs were incubated with HCl (pH 2.3) in vitro for 5 min and erosive calcium-release was measured photometrically. In addition, the acid treated specimens were evaluated by transmission electron microscopy (TEM). Pellicle free samples served as controls. RESULTS: Calcium erosion from the pellicle coated dentin slabs amounted to 23.5+/-2.9 microg Ca/min (pellicle free samples: 32.2+/-4.2 microg Ca/min). The difference was statistically significant (p < or = 0.05). In pellicle coated as well as in uncoated dentin samples, TEM-evaluation showed a demineralised dentinal surface layer which thickness ranged between 3 and 6 microm. The pellicle itself was partially dissolved but not removed by hydrochloric acid treatment. CONCLUSION: The protective properties of the acquired pellicle against an erosive challenge of the dentinal surface are limited. The dentinal pellicle functions like an ion permeable network rather than a barrier.

PMID: 17126806 [found with GoPubMed]


32: Hannig, C; Willenbücher, S; Becker, K; Mahony, C; Attin, T

Recovery of peroxides in saliva during home bleaching--influence of smoking.

Journal of oral rehabilitation 2006/Jul, 33(7):533-41

Department of Operative Dentistry, Preventive Dentistry and Periodontology, University of Göttingen, Göttingen, Germany. christian.hannig@med.uni-goettingen.de

The study aimed at determining hydrogen peroxide recovery in saliva during use of different home bleaching products by smokers and non-smokers. Peroxide recovery was evaluated with respect to the safe level reported in the literature. Determination of peroxide levels in saliva was performed with peroxidase, phenol and 4-aminoantipyrin in a photometric method. Four different bleaching regimens were used by 10 smokers and 10 non-smokers: Whitestrips, Vivastyle (tray-based) and two paint-on products (Crest Night Effects, Colgate Simply White). Whole saliva was collected and total amount of peroxide (mg) released during the 60 min bleaching period was determined: Colgate Simply White: 2.67 +/-0.88 (non-smokers); 2.66 +/- 1.17 (smokers); Crest Night Effects: 0.23 +/- 0.13 (non-smokers); 0.25 +/-0.16 (smokers); Vivastyle: 2.47 +/- 0.82 (non-smokers), 2.44 +/- 1.31 (smokers); Whitestrips: 1.39 +/- 0.62 (non-smokers), 2.02 +/- 1.86 (smokers). In terms of amount of peroxide kg(-1) body weight the bleaching systems led to a single exposure of 0.004-0.046 mg kg(-1), which is distinctly less than safe daily dose of 0.26 mg kg(-1) day(-1), if calculated for a small person (58 kg). The criterion smoker versus non-smokers had no influence on peroxide levels in the oral cavity. Conclusion: Smoking did not appear to impact the anti-oxidant defence capacity of the oral cavity with respect to degrading peroxides released from bleaching products. Significantly lower amounts of peroxides were detected in saliva during application of the paint-on product Crest Nights Effects compared with the other bleaching systems.

PMID: 16774513 [found with GoPubMed]


33: Hannig, Christian; Wasser, Mathias; Becker, Klaus; Hannig, Matthias; Huber, Karin; Attin, Thomas

Influence of different restorative materials on lysozyme and amylase activity of the salivary pellicle in situ.

Journal of biomedical materials research. Part A 2006/Sep, 78(4):755-61

Department of Operative Dentistry and Periodontology, University of Freiburg, Hugstetter Str. 55, D-79102 Freiburg, Germany. christian.hannig@uniklinik-freiburb.de

Lysozyme and amylase are the most abundant enzymatic components in the salivary pellicle. The purpose of the present study was to determine the influence of different substrata on amylase and lysozyme activity in salivary pellicles formed in situ. Slabs (5 mm diameter) of bovine dentine and enamel, of titanium, gold alloy, resin composite, PMMA, amalgam, and feldspar ceramic were fixed on the buccal sites of individual splints worn by six subjects for 30 min to allow pellicle formation. Thereafter, slabs were removed from the trays and rinsed with running water. Lysozyme activity was determined via lysis of Micrococcus lysodeicticus. Amylase activity was measured with a photometric method using 2-chloro-4-nitrophenyl-4-O-beta-D-galactopyranosylmaltotriosid (GalG2CNP) as substrate. Both pellicle enzymes were evaluated in the immobilized as well as in the desorbed state. Salivary enzyme activities were also measured. All investigated pellicles exhibited lysozyme and amylase activity. Great intraindividual and interindividual differences were observed. Over all samples, immobilized amylase activity amounted to 0.65 +/- 0.64 mU/cm2. Immobilized lysozyme activity was 5.04 +/- 1.55 U/cm2. There were no major effects of the substratum on pellicle-bound amylase and lysozyme activity. Immobilized and desorbed enzyme activities revealed a strong correlation (lysozyme: r = 0.700; amylase: r = 0.990). Salivary enzyme activities had only little impact on pellicle-bound enzyme activities. Amylase and lysozyme are incorporated in the acquired in situ pellicle on different solid surfaces in an active conformation. Dental material and enzyme activity in the saliva have only little impact on enzymatic activity in the pellicle in situ.

PMID: 16739107 [found with GoPubMed]


34: Hannig, Christian; Krieger, Eva; Dullin, Christian; Merten, Hans-Albert; Attin, Thomas; Grabbe, Eckhardt; Heidrich, Gabert

Volumetry of human molars with flat panel-based volume CT in vitro.

Clinical oral investigations 2006/Sep, 10(3):253-7

Department of Operative Dentistry and Periodontology, University of Freiburg, Hugstetter Str. 55, 79102, Freiburg, Germany. Christian.hannig@uniklinik-freiburg.de

The flat panel-based volume computed tomography (fpVCT) is a new CT device applicable for experimental, three-dimensional evaluation of teeth at a resolution of about 150 microm in the high contrast region. The aim of this study was to investigate whether fpVCT was suitable for quantification of the volumes of dental hard tissues and the root canal system to establish a new method for morphological studies. Fifty-two extracted third molars (maxillary: 31, mandibular: 21) were examined with a prototype of an fpVCT using a volumetry algorithm at different levels according to the radiographic density of enamel and dentine. Volumetry of the root canal system was performed after "region growing segmentation": starting from a voxel in the centre of the root canal, this algorithm searches voxels of same density in the surrounding. The volumetry of the root canal system was stopped by the investigator at the apical constriction. Results showed that dentine, enamel and root canal system could be well distinguished in three-dimensional images. Volumetry yielded the following data (cm(3), mean+/-SD): dentine 0.438+/-0.111, enamel 0.227+/-0.051, root canal system 0.052+/-0.017 and total volume 0.753+/-0.159. In conclusion, the fpVCT is appropriate for non-destructive volumetry of large numbers of teeth in experimental laboratory studies.

PMID: 16715215 [found with GoPubMed]


35: Hannig, Christian; Duong, Sebastian; Becker, Klaus; Brunner, Edgar; Kahler, Elke; Attin, Thomas

Effect of bleaching on subsurface micro-hardness of composite and a polyacid modified composite.

Dental materials : official publication of the Academy of Dental Materials 2007/Feb, 23(2):198-203

Department of Operative Dentistry and Periodontology, University of Freiburg, Hugstetter St. 55, D-79106 Freiburg, Germany. christian.hannig@uniklinik-freiburg.de

OBJECTIVE: To investigate the influence of different bleaching techniques on subsurface physical properties of composite and polyacid modified composite tested via determination of micro-hardness. METHODS: Specimens of Tetric Flow, Tetric EvoCeram and Compoglass were light cured (2.5mm thickness) and stored in artificial saliva for 2 weeks (n=12/group). The samples were only removed for application of the following bleaching agents in a humid atmosphere: Either Vivastyle (1h/d), Whitestrips (30min/d), sodium-perborate-water mixture (once for 72h), Simply White (1h/d), or Opalescence XtraBoost (1st and 5th day for 15min) were applied on the surfaces of the samples. Untreated specimens served as negative controls, samples treated with ethyl alcohol for 1h acted as positive controls. After the bleaching period, samples were cross-sectioned and the micro-hardness (Knoop) of different subsurface levels (0.1mm-2.0mm) was determined. RESULTS: All bleaching techniques significantly reduced the Knoop-hardness of the restoratives compared to untreated controls. Thereby, bleaching significantly affected not only superficial but also the deep layers of the specimens: in superficial layers (0.1mm, 0.2mm) lowest micro-hardness values amounted to 69.5% and 76.3% of the respective untreated controls (Compoglass/Vivastyle). In deeper subsurface levels, the lowest hardness was observed with Opalescence/Tetric EvoCeram (0.3mm: 78.3%; 0.4mm: 80%; 0.5mm: 80.5%; 1.0mm: 84.2%; 2.0mm: 84.4%). SIGNIFICANCE: Bleaching with the tested bleaching agents softens the adhesive restorative materials examined. Due to the fact that subsurface layers are also affected, polishing of the surface may not suffice for re-establishing the physical properties of the surface of the fillings.

PMID: 16546248 [found with GoPubMed]


36: Hannig, Christian; Laubach, Sebastian; Hahn, Petra; Attin, Thomas

Shear bond strength of repaired adhesive filling materials using different repair procedures.

The journal of adhesive dentistry 2006/Feb, 8(1):35-40

Department of Operative Dentistry, Preventive Dentistry and Periodontology, University of Göttingen, Germany. Christian.hannig@med.uni-goettingen.de

PURPOSE: Matrices of adhesive restorative materials and repair procedures may both influence bond strength of repaired adhesive materials. This study examined the bond strength of adhesive filling materials to mature adhesive materials after pretreatment with Co-Jet, Monobond S, and Silibond. MATERIALS AND METHODS: A hybrid composite (Tetric Ceram), a polyacid-modified composite resin (Dyract), and an ormocer (Definite) and their corresponding bonding agents were tested in combination with the repair systems. Restorative materials were placed in molds and polymerized. In group A (control), homologous materials were applied on the polymerized surface directly. In group B, homologous filling materials were placed onto the respective material with the corresponding bonding agent. In group C, adhesive repair filling material was applied after solely pretreating with the repair systems. In group D, the restorative material was applied after pretreatment with the repair systems and application of the corresponding bonding agent. Each subgroup consisted of 20 specimens. The shear bond strength of the samples was measured in a universal testing machine according to the test procedure ISO 10477. RESULTS: The significantly best bond strength of repair filling material on Tetric was achieved by pretreating with Co-Jet followed by application of the corresponding bonding agent (25.5 +/- 5.4 MPa, p < 0.05). A single application of the bonding agent or use of Monobond with bonding agent also yielded bond strengths of 20 MPa or more on Tetric. For Dyract or Definite, bond strengths of 15.5 +/- 5.3 MPa or less were achieved with the different repair procedures. CONCLUSION: Successful pretreatment of hybrid composites for repair can be achieved by application of Co-Jet followed by the corresponding bonding material, whereas sufficient repair of ormocers and polyacid-modified resin composites is limited.

PMID: 16536343 [found with GoPubMed]


37: Attin, Thomas; Albrecht, Kerstin; Becker, Klaus; Hannig, Christian; Wiegand, Annette

Influence of carbamide peroxide on enamel fluoride uptake.

Journal of dentistry 2006/Oct, 34(9):668-75

Department of Operative Dentistry, Preventive Dentistry and Periodontology, Georg-August-University Göttingen, D-37075 Göttingen, Germany. thomas.attin@med.uni-goettingen.de <thomas.attin@med.uni-goettingen.de>

OBJECTIVE: Aim of the study was to evaluate the influence of carbamide peroxide (CP) on enamel fluoride uptake by comparing enamel fluoride uptake from a 1% amine fluoride (AmF) gel with the fluoride acquisition from a 10% carbamide peroxide agent supplemented with 1% AmF. MATERIALS AND METHODS: Three enamel cylinders (4mm in diameter) were prepared from the buccal surfaces of 60 bovine incisors. One sample of each tooth was used for determination of baseline fluoride content of the respective tooth. The two remaining samples were allocated to the experimental series 1 or 2, respectively. Each series consisted of five experimental groups (A-E, n=12) and differed with respect to the length of the treatment period with the gels (A-D). The experimentally designed gels (pH 5.5) used in the study were as follows: A (10% CP), B (10% CP, 1% F(-) as AmF), C (1% F(-) as AmF), D (no CP, no F(-)) and were formulated on the same basis. The enamel samples were covered for 4h with the respective gel at 37 degrees C and were then transferred to artificial saliva for 20 h (series 1). The samples of group E served as controls and were not treated with a gel. In series 2, treatment with the gels and storage in saliva was conducted seven times. Finally, the samples were assessed for KOH-soluble and structurally bound fluoride. RESULTS: Only the enamel samples treated with the fluoridated bleaching gel (group B) and with the amine fluoride gel (group C) exhibited significant fluoride acquisition. Thereby, both gels showed significantly lower uptake in series 1 as compared to series 2. Both KOH-soluble and structurally bound fluoride acquisition was significantly higher in group C than in group B. CONCLUSION: Treatment with a carbamide peroxide gel supplemented with amine fluoride causes less fluoride acquisition in enamel than a pure amine fluoride gel. Under the conditions of the study, it is assumed that carbamide peroxide seems to influence enamel fluoride uptake.

PMID: 16472904 [found with GoPubMed]


38: Hannig, C; Dullin, C; Hülsmann, M; Heidrich, G

Three-dimensional, non-destructive visualization of vertical root fractures using flat panel volume detector computer tomography: an ex vivo in vitro case report.

International endodontic journal 2005/Dec, 38(12):904-13

Department of Operative Dentistry, Preventive Dentistry and Periodontology, University of Göttingen, Germany. christian.hannig@med.uni-goettingen.de

AIM: To detect and to visualize radiographically vertical root fractures in extracted teeth with a prototype of a novel, high resolution, three-dimensional flat panel volume detector computer tomograph (FD-VCT) system. SUMMARY: Five teeth with root fillings and clinical symptoms such as fistulas and isolated periodontal pockets of 8 mm or more were extracted after dental radiography indicating lateral or periapical lesions. Vertical root fractures or cracks were suspected because of the symptoms and clinical findings were evident after extraction in all cases but fracture lines were not visible on routine dental radiographs acquired before extraction. The extracted teeth were explored with a prototype of a FD-VCT. Using the FD-VCT, in all cases vertical root fractures or crack lines could be detected clearly in different views, depiction-modes and cross-sections at a spatial resolution of 140 microm. The evaluation of the fracture lines and teeth could be performed in three-dimensional views. The FD-VCT findings were confirmed by detailed inspection of the extracted teeth. KEY LEARNING POINTS: The FD-VCT is an innovative diagnostic tool for non-destructive, three-dimensional evaluation of extracted teeth in pre-clinical and experimental studies. The FD-VCT allows precise visualization and evaluation of vertical root fractures or cracks in extracted teeth. Clinical application of the system may be possible if technical modifications reduce the exposure dose: the high resolution detector systems of the FD-VCT should be combined with radiation systems that focus the radiation to the area of interest.

PMID: 16343118 [found with GoPubMed]


39: Heidrich, G; Hassepass, F; Dullin, C; Attin, T; Grabbe, E; Hannig, C

[Non-destructive, preclinical evaluation of root canal anatomy of human teeth with flat-panel detector volume CT (FD-VCT)]

RöFo : Fortschritte auf dem Gebiete der Röntgenstrahlen und der Nuklearmedizin 2005/Dec, 177(12):1683-90

Abteilung Diagnostische Radiologie, Universitätsklinikum Göttingen, Robert-Koch-Strasse 40, 37075 Göttingen. Gabert.Heidrich@t-online.de

PURPOSE: Successful endodontic diagnostics and therapy call for adequate depiction of the root canal anatomy with multimodal diagnostic imaging. The aim of the present study is to evaluate visualization of the endodont with flat-panel detector volume CT (FD-VCT). MATERIALS AND METHODS: 13 human teeth were examined with the prototype of a FD-VCT. After data acquisition and generation of volume data sets in volume rendering technology (VRT), the findings obtained were compared to conventional X-rays and cross-section preparations of the teeth. RESULTS: The anatomical structures of the endodont such as root canals, side canals and communications between different root canals as well as denticles could be detected precisely with FD-VCT. The length of curved root canals was also determined accurately. The spatial resolution of the system is around 140 microm. Only around 73 % of the main root canals detected with FD-VCT and 87 % of the roots could be visualized with conventional dental X-rays. None of the side canals, shown with FD-VCT, was detectable on conventional X-rays. In all cases the enamel and dentin of the teeth could be well delineated. No differences in image quality could be discerned between stored and freshly extracted teeth, or between primary and adult teeth. CONCLUSION: FD-VCT is an innovative diagnostic modality in preclinical and experimental use for non-destructive three-dimensional analysis of teeth. Thanks to the high isotropic spatial resolution compared with conventional X-rays, even the minutest structures, such as side canals, can be detected and evaluated. Potential applications in endodontics include diagnostics and evaluation of all steps of root canal treatment, ranging from trepanation through determination of the length of the root canal to obturation.

PMID: 16333792 [found with GoPubMed]


40: Hannig, Christian; Westphal, Christoph; Becker, Klaus; Attin, Thomas

Fracture resistance of endodontically treated maxillary premolars restored with CAD/CAM ceramic inlays.

The Journal of prosthetic dentistry 2005/Oct, 94(4):342-9

Department of Operative Dentistry, PreventiveDentistry and Periodontology, University of Gottingen, Robert-Koch-Strasse 40, 37075 Gottingen, Germany. christian.hannig@med.uni-goettingen.de

STATEMENT OF PROBLEM: Endodontically treated posterior teeth are more likely to fracture compared to posterior teeth with vital pulps. Reinforcement with an extracoronal restoration that covers the cusps is the most commonly recommended method for reducing the risk of fracture. It is not known whether bonded intracoronal restorations without cuspal coverage will reduce the risk of fracture. PURPOSE: The aim of this in vitro study was to investigate whether reinforcement of endodontically treated premolars with MOD preparations could be achieved by insertion of bonded CAD/CAM ceramic inlays. MATERIAL AND METHODS: Forty-five extracted maxillary premolars were equally distributed among 3 groups (END, CER, CTR). In group END (n=15), root canals were enlarged with a rotary NiTi system and obturated with heat-softened gutta-percha around a plastic carrier (Thermafil). After filling of the endodontic access cavities with autopolymerizing composite resin (Luxacore), standardized MOD cavity preparations were made and CAD/CAM ceramic inlays (CEREC) were fabricated and then bonded to the teeth with composite resin (Tetric) and an adhesive system (Syntac Classic). In group CER (n=15), teeth without endodontic treatment were restored with bonded inlays (CEREC). Sound premolars served as controls (group CTR, n=15). Teeth were then thermal cycled (1445 cycles, dwell time: 30 seconds, 5 degrees /55 degrees C). An eccentric load was applied on the buccal incline of the palatal cusp in a universal testing machine until cusp fracture (N). Fracture load was evaluated with the Mann-Whitney test, and type of fracture, with a chi-square analysis (alpha=.05). The type of fracture was determined by visual inspection: type I - supragingival fracture within the palatal cusp; type II - fracture below cemento-enamel junction of palatal cusp; and type III - fracture of palatal cusp and central portion of the tooth exposing the root canal cavity. RESULTS: No significant difference was found among the 3 groups with respect to load required for fracture. Mean fracture load +/- SD was recorded as follows: 291.6 +/- 113.7 N for group END, 363.2 +/- 140.3 N for group CER, and 296.5 +/- 170.5 N for group CTR. Regarding fracture modes, significantly more teeth from group END exhibited fractures of type III and II compared with control specimens. CONCLUSION: Teeth restored with bonded CAD/CAM ceramic inlays (CEREC) fractured with a significantly higher number of severe fractures compared to the control group.

PMID: 16198171 [found with GoPubMed]


41: Attin, T; Becker, K; Hannig, C; Buchalla, W; Hilgers, R

Method to detect minimal amounts of calcium dissolved in acidic solutions.

Caries research 2005 Sep-Oct, 39(5):432-6

Department of Operative Dentistry, Preventive Dentistry and Periodontology, Georg August University Göttingen, Göttingen, Germany. thomas.attin@med.uni-goettingen.de

The study describes the application of the Arsenazo III method for detection of minimal amounts of calcium 12.4-49.4 micromol/l in different acidic solutions (hydrochloric acid, oxalic acid, maleic acid, phosphoric acid, tartaric acid, citric acid, lactic acid and acetic acid) adjusted to pH 2.0, 2.3 and 3.0. A mixture of the respective calcium concentrations with distilled water served as control. The experiments were run with ten repeats in series. Assessment of intra- and interassay coefficient of variation, and lower limit of quantification revealed that depending on the acid used, the Arsenazo III method is a reliable tool to quantify minimal calcium contents in acidic solutions.

PMID: 16110217 [found with GoPubMed]


42: Hannig, Christian; Hoch, Jörg; Becker, Klaus; Hannig, Matthias; Attin, Thomas

Lysozyme activity in the initially formed in situ pellicle.

Archives of oral biology 2005/Sep, 50(9):821-8

Department of Operative Dentistry, Preventive Dentistry and Periodontology, University of Göttingen, Robert-Koch-Street 40, D-37075 Göttingen, Germany. christian.hannig@med.uni-goettingen.de

Lysozyme is one of the most abundant enzymatic components in the salivary pellicle. The purpose of the present in situ study was to determine if and to which extent lysozyme immobilised in pellicles exposes enzymatic activity. Influence of different oral sites and pellicle formation time on enzyme activity was also evaluated. Bovine enamel slabs (5mm diameter) were fixed on buccal and oral sites of individual trays worn by six subjects for 3 and 30 min on different days. After pellicle formation, slabs were removed from the trays and rinsed with running water. Afterwards, pellicle-bound lysozyme activity was determined via lysis of Micrococcus lysodeicticus photometrically in two steps. In a first step, lysozyme was desorbed in phosphate buffer and dissolved activity was measured. In a second step, slabs were incubated in phosphate buffer with the substrate and remaining immobilised activity was determined. All investigated pellicles exhibited lysozyme activity. Great intra- and inter-individual differences were observed. Mean desorbed activity of 3 min-pellicles amounted to 26.06+/-17.81 U/cm(2) (30 min; 26.79+/-17.48). The remaining immobilised activity was 13.54+/-11.42 for 3 min-pellicles and 16.08+/-12.81 for 30 min-pellicles. Pellicle derived lysozyme showed a Michaelis type kinetic. CONCLUSION: In situ pellicle exposes lysozyme activity even after a 3 min formation period. Exposed enzyme activity is neither influenced by pellicle formation time nor by the site of pellicle formation. It shows great inter- and intra-individual differences.

PMID: 15970212 [found with GoPubMed]


43: Attin, R; Thon, C; Schlagenhauf, U; Werner, C; Wiegand, A; Hannig, C; Attin, T

Recolonization of mutans steptococci on teeth with orthodontic appliances after antimicrobial therapy.

European journal of orthodontics 2005/Oct, 27(5):489-93

Department of Operative Dentistry and Preventive Dentistry and Periodontology, University of Göttingen. Rengin@tutuncu.de

The aim of the present study was to compare the recolonization pattern of mutans streptococci on densely colonized teeth with and without fixed orthodontic appliances after treatment with a 40 per cent chlorhexidine (CHX) varnish (EC 40, Explore). Healthy subjects free of carious lesions requiring fixed orthodontic appliance treatment but with high bacterial mutans streptococci saliva counts were recruited (n = 10). For baseline registration, plaque from buccal sites was sampled and cultivated on Dentocult strips. Following professional tooth cleaning, CHX varnish was applied to all teeth for 8 minutes. Subsequently, orthodontic brackets and bands were inserted in either the upper or lower arch. Eight weeks after varnish application the degree of recolonization with mutans streptococci was reassessed on the buccal sites. Statistical analysis showed that recolonization with mutans streptococci was significantly higher (P < 0.05) on teeth with orthodontic appliances. The results indicate that the use of fixed orthodontic appliances creates artificial environments suitable for the proliferation of mutans streptococci after CHX varnish suppression.

PMID: 15961573 [found with GoPubMed]


44: Attin, T; Becker, K; Hannig, C; Buchalla, W; Wiegand, A

Suitability of a malachite green procedure to detect minimal amounts of phosphate dissolved in acidic solutions.

Clinical oral investigations 2005/Sep, 9(3):203-7

Department of Operative and Preventive Dentistry and Periodontology, Georg-August-University Göttingen, Robert-Koch-Strasse 40, 37075 Göttingen, Germany. thomas.attin@med.uni-goettingen.de

The study describes the suitability of a colorimetric method (malachite green procedure) for detection of minimal amounts of phosphate (7.3-29.1 micromol/L) in different acidic solutions (hydrochloric acid, oxalic acid, maleic acid, perchloric acid, tartaric acid, citric acid, lactic acid and acetic acid) adjusted to pH 2.0. A mixture of the respective phosphate concentrations with distilled water served as control. The experiments were run with ten repeats in series. Assessment of intra- and interassay coefficient of variation and lower limit of quantification revealed that depending on the acid used, the applied method is a reliable and suitable tool to detect and quantify minimal phosphate contents in small samples of acidic solutions that have the potential to cause erosive dental lesions.

PMID: 15912408 [found with GoPubMed]


45: Hannig, Christian; Hamkens, Arne; Becker, Klaus; Attin, Rengin; Attin, Thomas

Erosive effects of different acids on bovine enamel: release of calcium and phosphate in vitro.

Archives of oral biology 2005/Jun, 50(6):541-52

Department of Operative Dentistry, Preventive Dentistry and Periodontology, University of Göttingen, Robert-Koch-Str. 40, D-37075 Göttingen, Germany. christian.hannig@med.uni-goettingen.de

The present study intended to investigate minimal erosive effects of different acids on enamel during short time incubation via determination of calcium and phosphate dissolution. Bovine enamel specimens were eroded for 1-5 min with eight different acids of pH 2, 2.3 and 3 (citric (CA), maleic (MA), lactic (LA), tartaric (TA), phosphoric (PA), oxalic (OA), acetic (AA) and hydrochloric acid (HCl)). Calcium (Ca) and phosphate (P) release were determined photometrically using arsenazo III (calcium) and malachite green (phosphate) as substrates. Each subgroup contained eight enamel specimens. Amount of titratable acid was determined for all acidic solutions. MA, LA, TA, AA and HCl caused linear release of Ca and P, PA of Ca, CA of P. For CA, MA, LA, TA, AA, PA and HCl mineral loss was shown to be pH-dependent. Ca dissolution varied between 28.6+/-4.4 (LA, pH 2) and 2.4+/-0.7 nmol mm(-2)min(-1) (HCl, pH 3), P dissolution ranged between 17.2+/-2.6 (LA, pH 2) and 1.4+/-0.4 nmol mm(-2)min(-1) (HCl, pH 3). LA was one of the most erosive acids. AA was very erosive at pH 3. HCl and MA were shown to have the lowest erosive effects. There was only a weak correlation (r=0.28) between P and Ca release and the amount of titratable acid. The method of the present study allows investigation of minimal erosive effects via direct determination of P and Ca dissolution. During short time exposition at constant pH level, erosive effects mainly depend on pH and type of acid but not on amount of titratable acid.

PMID: 15848147 [found with GoPubMed]


46: Hannig, Christian; Zech, Ronald; Henze, Elvira; Dreier, Sönke; Attin, Thomas

Peroxide release into saliva from five different home bleaching systems in vivo.

American journal of dentistry 2005/Feb, 18(1):13-8

Department of Operative and Preventive Dentistry and Periodontology, University of Göttingen, D-37075 Göttingen, Germany. christian.hannig@med.uni-goettingen.de

PURPOSE: This study determined hydrogen peroxide release into the oral cavity during use of different home bleaching products and compared them with accepted safe levels. METHODS: Determination of peroxide in saliva was performed with peroxidase, phenol and 4-aminoantipyrin in a photometric method. Upper jaw incisors were bleached with individual trays charged with 350 mg Opalescence 10%, Opalescence 15% (OP) and Vivastyle (V). Additionally, Whitestrips (WS) designed for upper or lower jaw were used. All systems were adopted by five subjects for 30 minutes on different days. Whole saliva was collected at 2-minute intervals during the first 10 minutes of bleaching and every 5 minutes thereafter. RESULTS: Highest release of peroxide was found for all products in the saliva sample collected initially after application of the bleaching agent. Total amount of peroxide released into saliva during 30-minute bleaching period was 0.78+/-0.45 for Opalescence 10% and 1.52+/-0.44 mg for Opalescence 15%. Significantly more peroxide was released from Vivastyle (2.67+/-1.03 mg) and from Whitestrips (upper: 3.25+/-5,65, lower: 2.09+/-0.34 mg). A significantly smaller fraction of the charged peroxides was released into saliva from individual trays than from Whitestrips during the 30-minute use time. From the peroxide loaded in the trays or strips the following fractions were released during the application period: Opalescence 10% (6.4+/-3.7%), Opalescence 15% (8+/-2.4%), Vivastyle (18.6+/-8.5%), upper Whitestrips (30.4+/-4.9), lower Whitestrips (27.4+/-4.4%). In terms of amount/kg body weight the bleaching systems led to a single exposure of 0.013-0.056 mg/kg which is distinctly less than the maximum safe daily dose of 0.26 mg/kg/day if calculated for a small person (58 kg/128 lbs).

PMID: 15810475 [found with GoPubMed]


47: Attin, T; Grieme, R; Paqué, F; Hannig, C; Buchalla, W; Attin, R

Enamel fluoride uptake of a novel water-based fluoride varnish.

Archives of oral biology 2005/Mar, 50(3):317-22

Department of Operative and Preventive Dentistry and Periodontology, Georg-August-University Göttingen, Robert-Koch-Str. 40, D-37075 Göttingen, Germany. thomas.attin@med.uni-goettingen.de

Aim of the in situ-study was to evaluate fluoride retention in sound and demineralised enamel after application of a novel water-based fluoride (0.12% F) varnish Mirafluorid (Hager and Werken, Germany) compared to the resin-based varnish (2.26% F) Duraphat (Colgate, USA). Each five enamel specimens were prepared from 60 bovine incisors. In 150 of these specimens, incipient lesions were produced with acidic hydroxyethylcellulose (pH 4.8; 72 h), 150 specimens were not demineralised. The samples were equally (n=100) allotted to three groups (A: Mirafluord, B: Duraphat, and C: control). Each 80 specimens (40 demineralised and 40 sound) were varnished with either Mirafluorid or Duraphat or remained unfluoridated (controls). The other specimens were used for measuring base-line fluoride content of the respective tooth. Each six specimens (three demineralised and three sound) were fixed in intraoral appliances worn for 5 days by 10 volunteers in three series (A-C). During the experiment, the samples were brushed twice daily with fluoridated toothpaste. KOH-soluble and structurally bound fluoride (0-30 and 31-60 microm depth) was determined immediately, 1, 3 and 5 days after fluoridation. Fluoride uptake was calculated as compared to base-line content and statistically analysed. Immediately after fluoridation, uptake of KOH-soluble and structurally bound fluoride was similar for Mirafluorid and Duraphat in both demineralised and sound enamel. However, at day 1, 3 and 5 statistically significantly higher amounts of KOH-soluble and structurally bound fluoride were found in the samples treated with Duraphat. For Mirafluorid only the uptake for KOH-soluble fluoride and structurally bound fluoride in the first enamel layer (0-30 microm) of the demineralised samples was significantly higher compared to the controls (C). It is concluded that the novel fluoride varnish Mirafluorid deposits less KOH-soluble and structurally bound fluoride on both demineralised and sound enamel compared to Duraphat under in situ-conditions.

PMID: 15740710 [found with GoPubMed]


48: Hannig, Christian; Hannig, Matthias; Attin, Thomas

Enzymes in the acquired enamel pellicle.

European journal of oral sciences 2005/Feb, 113(1):2-13

Department of Operative Dentistry, Preventive Dentistry and Periodontology, University of Göttingen, Robert-Koch-Strasse 40, D-37075 Göttingen, Germany. christian.hannig@med.uni-goettingen.de

The acquired pellicle is a biofilm, free of bacteria, covering oral hard and soft tissues. It is composed of mucins, glycoproteins and proteins, among which are several enzymes. This review summarizes the present state of research on enzymes and their functions in the dental pellicle. Theoretically, all enzymes present in the oral cavity could be incorporated into the pellicle, but apparently enzymes are adsorbed selectively onto dental surfaces. There is clear evidence that enzymes are structural elements of the pellicle. Thereby they exhibit antibacterial properties but also facilitate bacterial colonization of dental hard tissues. Moreover, the immobilized enzymes are involved in modification and in homeostasis of the salivary pellicle. It has been demonstrated that amylase, lysozyme, carbonic anhydrases, glucosyltransferases and fructosyltransferase are immobilized in an active conformation in the pellicle layer formed in vivo. Other enzymes, such as peroxidase or transglutaminase, have been investigated in experimental pellicles. Despite the depicted impact of enzymes on the formation and function of pellicle, broader knowledge on their properties in the in vivo-formed pellicle is required. This might be beneficial in the development of new preventive and diagnostic strategies.

PMID: 15693823 [found with GoPubMed]


49: Deimling, Daniela; Breschi, Lorenzo; Hoth-Hannig, Wiebke; Ruggeri, Alessandra; Hannig, Christian; Nekrashevych, Yuriy; Prati, Carlo; Hannig, Matthias

Electron microscopic detection of salivary alpha-amylase in the pellicle formed in situ.

European journal of oral sciences 2004/Dec, 112(6):503-9

Department of Operative Dentistry and Periodontology, University of Freiburg, Hugstetterstr. 55, D-79106 Freiburg, Germany. deimling@zmk2.ukl.uni-freiburg.de

Immunological and biochemical analyses have shown that alpha-amylase is an essential component of the acquired pellicle. After adsorption, this enzyme might act as a receptor for bacterial adherence. However, data indicating that amylase is bound to the pellicle surface in vivo and thus available for adhering bacteria are rare. Therefore, the present study focused on alpha-amylase within the pellicle formed in situ, using gold-immunolabeling electron microscopic techniques. Pellicles were formed by intra-oral exposure of enamel specimens for 30 and 120 min in six subjects. The results obtained by transmission electron microscopy indicate that amylase was randomly distributed in the pellicle layer without any preferential localization within the pellicle. Thus, salivary alpha-amylase might be considered as an important structural component that is even involved in the early stages of pellicle formation. The findings of field emission in-lens scanning electron microscopy provided evidence that the enzyme is located on the pellicle surface. It could be concluded that alpha-amylase might act as a receptor for bacterial adherence to the pellicle in vivo.

PMID: 15560833 [found with GoPubMed]


50: Attin, Thomas; Hannig, Christian; Wiegand, Annette; Attin, Rengin

Effect of bleaching on restorative materials and restorations--a systematic review.

Dental materials : official publication of the Academy of Dental Materials 2004/Nov, 20(9):852-61

Department of Operative Dentistry, Preventive Dentistry and Periodontology, Georg-August-Universität Göttingen, Robert-Koch-Str. 40, D-37075, Germany. thomas.attin@med.uni-goettingen.de

OBJECTIVE: Internal and external bleaching procedures utilizing 3-35% hydrogen peroxide solutions or hydrogen peroxide releasing agents, such as carbamide peroxide or sodium perborate, can be used for whitening of teeth. The purpose of the review article was to summarize and discuss the available information concerning the effects of peroxide releasing bleaching agents on dental restorative materials and restorations. SOURCES: Information from all original scientific full papers or reviews listed in PubMed or ISI Web of Science (search term: bleaching AND (composite OR amalgam OR glass ionomer OR compomer OR resin OR alloy) were included in the review. DATA: Existing literature reveals that bleaching therapies may have a negative effect on physical properties, marginal integrity, enamel and dentin bond strength, and color of restorative materials as investigated in numerous in vitro studies. However, there are no reports in literature indicating that bleaching may exert a negative impact on existing restorations requiring renewal of the restorations under clinical conditions. CONCLUSION: Bleaching may exert a negative influence on restorations and restorative materials. Advice is provided based on the current literature to minimize the impact of bleaching therapies on restorative materials and restorations.

PMID: 15451241 [found with GoPubMed]


51: Hannig, Christian; Attin, Thomas; Hannig, Matthias; Henze, Elvira; Brinkmann, Kirsten; Zech, Ronald

Immobilisation and activity of human alpha-amylase in the acquired enamel pellicle.

Archives of oral biology 2004/Jun, 49(6):469-75

Department of Operative Dentistry, Preventive Dentistry and Periodontology, University of Göttingen, Robert-Koch-Str. 40, D-37075 Goettingen, Germany. christian.hannig@med.uni-goettingen.de

Amylase is an important salivary component and structural element of the acquired enamel pellicle. Aim of the study was to establish a method for precise and direct determination of pellicle bound amylase activity in order to analyse kinetics and activity of the immobilised enzyme. Six bovine enamel slabs (5mm diameter) were fixed on individual maxillary trays and worn by five subjects for different times (3, 30 and 120 min) on buccal and palatal sites on different days. Slabs were removed from the trays and rinsed with aqua dest. Afterwards, pellicle bound amylase activity was determined directly with a photometric method using 2-chloro-4-nitrophenyl-4-O-beta-D-galactopyranosylmaltotriosid (GalG2CNP) as substrate yielding the coloured product chloronitrophenolate (CNP). All investigated pellicles exhibited immobilised amylase activity. Mean activity was 1.39 +/- 187 mU/cm(2) (n=87, range 0.14-11.5 mU/cm(2)). Product formation of CNP by immobilised amylase was linear over time. Pellicle bound amylase showed a Michaelis type kinetic (Km = 3.3 x 10(-3) M). Immobilised activity on buccal surfaces ranged between 0.25 and 11.1 mU/cm(2) (palatal slabs: 0.14-3.06 mU/cm(2)). Thirty minutes pellicles formed on buccal sites exhibited significantly higher immobilised amylase activity (2.85 +/- 3.65 mU/cm(2)) than palatal ones (0.63 +/- 0.32 mU/cm(2)). Amylase activity showed great intraindividual variability when comparing same positions on different days. CONCLUSION: Pellicle bound amylase activity can be determined directly with GalG2CNP and shows a Michaelis Menten kinetic. Enzyme activity of the amylase immobilised in the in situ pellicle reveals great intra- and interindividual differences.

PMID: 15099804 [found with GoPubMed]


52: Attin, T; Siegel, S; Buchalla, W; Lennon, A M; Hannig, C; Becker, K

Brushing abrasion of softened and remineralised dentin: an in situ study.

Caries research 2004 Jan-Feb, 38(1):62-6

Department of Operative Dentistry, Preventive Dentistry and Periodontology, Georg August University Göttingen, Göttingen, Germany. thomas.attin@med.uni-goettingen.de

The aim of the present in situ study was to evaluate the effect of different periods of intra-oral remineralisation on the susceptibility of softened dentin to toothbrushing abrasion. Groups of 6 human dentin specimens (A-F) were recessed in the buccal aspects of intra-oral appliances which were worn for 21 days by 11 volunteers. The samples were demineralised twice a day extra-orally in the acidic beverage Sprite Light (pH 2.9) for 90 s. Subsequently, the dentin specimens were brushed at different times. Specimen A was brushed immediately after demineralisation. Specimens B-E were brushed after the intra-oral appliances had been worn for various periods in the mouth: specimen B for 10 min, C for 20 min, D for 30 min and E for 60 min. Specimen F was not brushed (control). After 21 days, dentin wear was measured with a profilometer. The following values (means +/- standard deviation) were recorded (microm): A, 23.6 +/- 16.7; B, 37.9 +/- 29.7; C, 31.8 +/- 26.5; D, 18.5 +/- 10.5; E, 15.3 +/- 11.6; F, 12.6 +/- 6.7. There was a statistically significantly increased dentin loss for groups A, B and C as compared to the controls (U test: p < 0.05). However, after intra-oral periods of 30 and 60 min, wear was not significantly higher than in unbrushed controls. It is concluded that for protection of dentin surfaces at least 30 min should elapse before toothbrushing after an erosive attack.

PMID: 14684979 [found with GoPubMed]


53: Hannig, Christian; Hahn, Petra; Thiele, Patrick-Philipp; Attin, Thomas

Influence of different repair procedures on bond strength of adhesive filling materials to etched enamel in vitro.

Operative dentistry 2003 Nov-Dec, 28(6):800-7

Department of Operative Dentistry, Preventive Dentistry and Periodontology, University of Göttingen, Göttingen, Germany. Christian.hannig@med.uni-goettingen.de

Contamination of etched enamel with repair bond agents during repair of dental restorations may interfere with the bonding of composite to enamel. This study examined the bond strength of adhesive filling materials to etched bovine enamel after pre-treatment with the repair systems Monobond S, Silibond and Co-Jet. The materials Tetric Ceram, Dyract and Definite and their corresponding bonding agents (Syntac Single Comp, Prime & Bond NT, Etch and Prime) were tested in combination with the repair systems. One hundred and thirty-five enamel specimens were etched (37% phosphoric acid, 60 seconds) and equally distributed among three groups (A-C). In Group A, the repair materials were applied on etched enamel followed by applying the composite materials without using their respective bonding material. In Group B, the composite materials were placed on etched enamel after applying the repair materials and bonding agents. In control Group C, the composite materials and bonding agents were applied on etched enamel without using the repair systems. In each sub-group, every composite material was applied on 15 specimens. Samples were stored in artificial saliva for 14 days and thermocycled 1,000 times (5 degrees C/55 degrees C). The shear bond strength of the samples were then determined in a universal testing machine (ISO 10477). Applying Monobond or Silibond followed by the use of its respective bonding agents resulted in a bond strength that was not statistically different from the controls for all filling materials (Group C). The three composites that used Monobond and Silibond without applying the corresponding bonding agent resulted in bond strengths that were significantly lower than the controls. Utilizing the Co-Jet-System drastically reduced the bond strength of composites on etched enamel. Contamination of etched enamel with the repairing bonding agents Monobond and Silibond does not interfere with bond strength if the application of Monobond and Silibond is followed by using its corresponding bonding system of the composites tested.

PMID: 14653297 [found with GoPubMed]


54: Hannig, Christian; Zech, Ronald; Henze, Elvira; Dorr-Tolui, Reza; Attin, Thomas

Determination of peroxides in saliva--kinetics of peroxide release into saliva during home-bleaching with Whitestrips and Vivastyle.

Archives of oral biology 2003/Aug, 48(8):559-66

Department of Operative Dentistry, Preventive Dentistry and Periodontology, University of Göttingen, Robert-Koch-Str. 40, 37075 Göttingen, Germany. christian.hannig@med.uni-goettingen.de

Aim of the study was to determine peroxides in saliva, released during bleaching procedures. Upper incisors of five subjects were bleached with Whitestrips (5% H2O2) and Vivastyle (10% carbamide peroxide, tray charged with 225mg) for 30min, each on different days. Saliva was collected before and during the whole period of bleaching at different intervals. The amount of peroxide in the salivary samples was assessed with peroxidase, phenol and 4-aminoantipyrin in a photometric assay. Additionally the amount of peroxides in the bleaching material was determined before and after the bleaching, so that the peroxide release into saliva could be balanced. The amount of peroxides released into saliva was related to the bleaching system and only partially influenced by the individual salivary flow rate. Bleaching with Vivastyle led to lower release of peroxides into saliva compared to Whitestrips (Vivastyle: 0.8+/-0.17mg; Whitestrips: 1.5+/-0.84mg). Salivary flow rate was not correlated to release of peroxides from the bleaching products. It can be concluded that the enzymatic method adopting 4-aminoantipyrin and peroxidase is valid for the determination of peroxides in saliva. Furthermore distinctly more peroxides are released into the oral cavity from Whitestrips than from trays charged with Vivastyle .

PMID: 12828984 [found with GoPubMed]


55: Attin, T; Manolakis, A; Buchalla, W; Hannig, C

Influence of tea on intrinsic colour of previously bleached enamel.

Journal of oral rehabilitation 2003/May, 30(5):488-94

Department of Operative, Preventive Dentistry and Periodontology, Georg-August-University Göttingen, Göttingen, Germany. thomas.attin@med.uni-goettingen.de

Aim of the study was to evaluate the influence of tea applied at various time intervals after bleaching of enamel on intrinsic tooth colour. Ninety bovine specimens were distributed among six groups (A-F, n=15). The samples of group A-D were bleached with the 10% carbamide peroxide (CP) gel VivaStyle for 8 h, followed by storing in artificial saliva for the remaining period of the day. The specimens were removed from the saliva at different intervals (A: 0 min, B: 60 min, C: 240 min) and immersed in freshly prepared black tea for 10 min. Group D (bleaching, no tea), E (no bleaching, but tea) and F (no bleaching, no tea) served as controls. These procedures were repeated for 8 days. Colour was measured at baseline, after each day, and after final cleaning using the CIELab-system. Then Deltab (initial b-value - final reading), DeltaL, and composite colour (DeltaE) were statistically analysed. External bleaching (A-D) led to a distinct whitening effect with lower Deltab- (=reduction in yellow) and higher DeltaL-values (=increase in brightness) compared with controls. The Deltab- and DeltaL-values of the samples A-C were not significantly different from the samples which were bleached only. No significant difference was observed comparing specimens of group A-C. It is concluded that application of tea directly after bleaching with 10% CP does not significantly effect the outcome of a bleaching treatment irrespective of the time interval elapsed between the bleaching procedure and the contact of the tooth surface with tea.

PMID: 12752928 [found with GoPubMed]


56: Attin, T; Kocabiyik, M; Buchalla, W; Hannig, C; Becker, K

Susceptibility of enamel surfaces to demineralization after application of fluoridated carbamide peroxide gels.

Caries research 2003 Mar-Apr, 37(2):93-9

Department of Operative Dentistry, Preventive Dentistry and Periodontology, Georg August University Göttingen, Göttingen, Germany. thomas.attin@med.uni-goettingen.de

The aim of the present study was to evaluate the effect of experimental, fluoridated carbamide peroxide gels on formation of erosively induced demineralization of enamel. Seventy-five bovine enamel specimens were polished for microhardness determination and evenly distributed among 5 groups (A-E). The specimens were treated with 10% carbamide peroxide gel (8 h) and subjected twice to remineralization for 2 h in artificial saliva and demineralisation for 90 s in 1% citric acid, pH 2.2. The cycles of treatment with carbamide peroxide and twofold re- and demineralization were repeated three times. The carbamide peroxide gels were different in pH and fluoride content. Gel A (pH 7.0) and gel B (pH 5.7) were fluoridated (0.5% F), gel C (pH 7.0) and gel D (pH 5.7) were not fluoridated. In control group E the samples were not treated with a gel, but stored in 100% humidity for 8 h instead. Knoop microhardness of the specimens was assessed directly after polishing, and after each carbamide peroxide treatment and demineralization. All specimens showed a loss of microhardness at the end of the experiment. After 3 days, the controls revealed a significantly lower hardness loss compared to the specimens treated with the carbamide peroxide gels. Surface softening was significantly lower for the specimens of group A compared to the remaining groups (B-D), which were not significantly different among each other. It is concluded that treatment with either fluoridated or unfluoridated carbamide peroxide gels, at either neutral and acidic pH, renders enamel more susceptible to demineralization. Use of a fluoridated neutral gel decreases the degree of surface softening compared to the other gels investigated.

PMID: 12652046 [found with GoPubMed]