Enamel loss and adhesive remnants following bracket removal and various clean-up procedures in vitro

This study evaluated the enamel loss and composite remnants after debonding and clean-up. The tested null hypothesis is that there are no differences between different polishing systems regarding removing composite remnants without damaging the tooth surface. Brackets were bonded to 75 extracted human molars and removed after a storage period of 100 hours. The adhesive remnant index (ARI) was evaluated. The clean-up was carried out with five different procedures: 1. carbide bur; 2. carbide bur and Brownie and Greenie silicone polishers; 3. carbide bur and Astropol polishers; 4. carbide bur and Renew polishers; and 5. carbide bur, Brownie, Greenie and PoGo polishers. Silicone impressions were made at baseline (T0) and after debonding (T1) and polishing (T2) to produce plaster replicas. The replicas were analysed with a three-dimensional laser scanner and measured with analytical software. Statistical analysis was performed with the Kruskal-Wallis test and pairwise Wilcoxon tests with Bonferroni-Holm adjustment (α = 0.05). Enamel breakouts after debonding were detectable in 27 per cent of all cases, with a mean volume loss of 0.02 mm3 (±0.03 mm3) and depth of 44.9 μm (±48.3 μm). The overall ARI scores was 3 with a few scores of 1 and 2. The composite remnants after debonding had a mean volume of 2.48 mm3 (±0.92 mm3). Mean volume loss due to polishing was 0.05 mm3 (±0.26 mm3) and the composite remnants had a mean volume of 0.22 mm3 (±0.32 mm3). There were no statistically significant differences in volumetric changes after polishing (P = 0.054) between the different clean-up methods. However, sufficient clean-up without enamel loss was difficult to achiev

Three-year randomised clinical trial to evaluate the clinical performance, quantitative and qualitative wear patterns of hybrid composite restorations

The aim of the study was to compare the clinical performance, quantitative and qualitative wear patterns of conventional hybrid (Tetric Ceram), micro-filled hybrid (Gradia Direct Posterior) and nano-hybrid (Tetric EvoCeram, TEC) posterior composite restorations in a 3-year randomised clinical trial. Sixteen Tetric Ceram, 17 TEC and 16 Gradia Direct Posterior restorations were placed in human molars and evaluated at baseline, 6, 12, 24 and 36 months of clinical service according to US Public Health Service criteria. The gypsum replicas at each recall were used for 3D laser scanning to quantify wear, and the epoxy resin replicas were observed under scanning electron microscope to study the qualitative wear patterns. After 3 years of clinical service, the three hybrid restorative materials performed clinically well in posterior cavities. Within the observation period, the nano-hybrid and micro-hybrid restorations evolved better in polishability with improved surface gloss retention than the conventional hybrid counterpart. The three hybrid composites showed enamel-like vertical wear and cavity-size dependant volume loss magnitude. Qualitatively, while the micro-filled and nano-hybrid composite restorations exhibited signs of fatigue similar to the conventional hybrid composite restorations at heavy occlusal contact area, their light occlusal contact areas showed less surface pitting after 3 years of clinical service

Wear prediction for dental composites (an in vivo and in vitro correlative approach)

During the last couple of decades, most of the information about dental restorative materials is embedded in a collection of huge numbers of lab oratory tests. A large share of the laboratory research done with dental materials has been concerned with the wear of the materials. Over the y ears, only about 5-10% of all the in-vitro information h as been associated with clinical data retrieved from clinical trials tha t are often short term and limited in terms of products tested. Establis hing the relationship between laboratory testing and clinical outcomes f or a collection of restorative materials is needed not only for the futu re predictions of their long- term in-vivo performance b ut also to drive evidence-based clinical decision making of the right restorative materials in dentistry. Focussing on the intraoral wear phenomenon, the objective of this PhD dissertation was to examine t he correlation of laboratory test results with the clinical wear events of a collection of commercial dental composites tested in randomized cli nical trials and explain the wear behavior of the investigated composite s relative to clinical decision making. Since RCTs provide ulti mate proof of performance of any restorative material, it was decided to first conduct two individual RCTs to investigate the overall clinical p erformance of a collection of commercial dental composites and to record the clinical wear events (wear magnitude and worn surface topography). Pooled analysis of the clinical wear data retrieved from both the RCTs e nabled a) establishing the CFOA and OCA wear rates of the investigated c omposites and that of human enamel; b) investigating a wide range of fac tors such as operator factors, material factors, intraoral location fact ors and patient factors suspected to be involved in the wear performance of any restoration. Subsequently, it was decided to identify l aboratory tests that correlate with observations of clinical wear events by examining if the laboratory tests rank the materials similar to that produced by clinical trials. Further attempt was made to understand the effect of mechanical stresses occuring cyclically during intercuspation , swallowing, or chewing on the clinical wear performance of the restora tives that might reflect as a change in the initial rank order. Very pro mising was the fact that the rank order produced by in-vitro scratch tests correlated well with the in-vivo CFOA wear rank order and a similar good correlation was observed between t he rank orders of simulated wear in a chewing simulator and in-v ivo contact wear. This indicated the suitability of the applied testing and simulating devices to reliably predict the in-vivo wear of new resin composite materials and the usefulness of the c orrelative rank order approach as a fast, simple method for estimating a nd/or predicting the relative clinical wear characteristics. Preservation of a similar rank order in-vitro and in-vivo by the investigated composites suggested that composites per forming superior in-vitro, also exhibit superior wear resista nce clinically, which is a useful evidence for clinical decision making.nrpages: 148status: publishe

Genomic evidences for the redox activity in oral-microbial induced corrosion

Tese de mestrado em Bioinformática, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2006Esta dissertação investiga indícios moleculares para compreensão de fenómenos de corrosão induzida por micróbios da cavidade oral com recurso a métodos da bioinformática, como o alinhamento de sequências, a análise comparativa de sequências e a análise filogenética. O estudo adopta uma abordagem reducionista para obtenção de conhecimento sobre estes fenómenos, através da filtragem de um conjunto alargado de dados seguida de uma análise detalhada de uma lista reduzida de sequências de bactérias da cavidade oral associadas a efeitos de biocorrosão observados experimentalmente. A estratégia seguida recorreu à inspecção de 500 micróbios da placa dental e 22 enzimas redox de forma a obter um conjunto de dados representativo restrito a 17 micróbios e três enzimas. O significado estatístico dos resultados obtidos e a correlação entre os indícios genómicos e os efeitos de corrosão induzida em micróbios observados experimentalmente mostram a efectividade da aproximação. A análise do bootstrap evidencia, com suporte acima de 90%, o envolvimento de padrões preservados e resíduos de factores electroquímicos que governam a modulação do potencial de redução para promoção da corrosão em sistemas biológicos complexos. Este trabalho identifica partilhas prováveis de genes entre espécies da placa dentária distantes entre si, sugerindo a presença de grupos de genes específicos da placa dentária.This dissertation researches molecular clues of microbially induced corrosion phenomena of the oral cavity using bioinformatics methods. These include sequence alignments, comparative sequence analysis, and phylogenetic analysis. It adopts a reductionist approach to obtain this knowledge, by screening a large dataset and then conducting a detailed analysis of a shortlist of biologically meaningful sequences featured in oral microbes that are associated with the experimental effects of biocorrosion. The strategy involved the screening of a large dataset of 500 dental plaque microbes and 22 redox enzymes, to select a representative subset of the data, restricted to 17 microbes and three enzymes. The statistical confidence of the obtained results and the correlation between the genomic evidences and the experimentally observed effects of MIC show the effectiveness of the approach. High bootstrap support above 90% provides the molecular evidence of involvement of conserved patterns and residues in electrochemical factors that govern the modulation of reduction potential for promoting corrosion in complex biological systems. This work also identifies probable gene sharing events between distantly related dental plaque species, suggesting the presence of dental plaque-specific gene pools

Enamel loss and adhesive remnants following bracket removal and various clean-up procedures in vitro

This study evaluated the enamel loss and composite remnants after debonding and clean-up. The tested null hypothesis is that there are no differences between different polishing systems regarding removing composite remnants without damaging the tooth surface. Brackets were bonded to 75 extracted human molars and removed after a storage period of 100 hours. The adhesive remnant index (ARI) was evaluated. The clean-up was carried out with five different procedures: 1. carbide bur; 2. carbide bur and Brownie and Greenie silicone polishers; 3. carbide bur and Astropol polishers; 4. carbide bur and Renew polishers; and 5. carbide bur, Brownie, Greenie and PoGo polishers. Silicone impressions were made at baseline (T0) and after debonding (T1) and polishing (T2) to produce plaster replicas. The replicas were analysed with a three-dimensional laser scanner and measured with analytical software. Statistical analysis was performed with the Kruskal-Wallis test and pairwise Wilcoxon tests with Bonferroni-Holm adjustment (α = 0.05). Enamel breakouts after debonding were detectable in 27 per cent of all cases, with a mean volume loss of 0.02 mm(3) (±0.03 mm(3)) and depth of 44.9 μm (±48.3 μm). The overall ARI scores was 3 with a few scores of 1 and 2. The composite remnants after debonding had a mean volume of 2.48 mm(3) (±0.92 mm(3)). Mean volume loss due to polishing was 0.05 mm(3) (±0.26 mm(3)) and the composite remnants had a mean volume of 0.22 mm(3) (±0.32 mm(3)). There were no statistically significant differences in volumetric changes after polishing (P = 0.054) between the different clean-up methods. However, sufficient clean-up without enamel loss was difficult to achieve.status: publishe

Correlating in vitro scratch test with in vivo contact free occlusal area wear of contemporary dental composites

Objectives The aims of this study are to determine the extent to which the ranking order for clinical Contact-Free-Occlusal-Area (CFOA) wear performance of composites correlates with the ranking based on in vitro scratch hardness, and to analyze the extent to which the microstructure influences the overall trend. Materials and methods The patient data and CFOA wear measurements of 16 Tetric-C, 17 Tetric-EC, 16 Gradia-DP, 18 Filtek Supreme, 19 Z100 restorations in 31 subjects (8 males, 23 females) of two randomized clinical trials were fitted in a mixed-effect model. The in vivo performance of the restoratives was summarized by ranking the estimated material-related coefficients in the model. Scratch tests on two specimens per composite were run at a constant speed of 0.05 mm/s under indenter with normal loads of 15, 25, and 35 mN. Scratch width, depth and hardness calculated by imaging the scratch tracks were summarized in a model, the material-related coefficients were ranked and correlated with that of in vivo ranking order. Results The best in vivo model included as significant factors (p Tetric-C, Tetric-EC > Gradia-DP-correlated closely (R² = 0.991) with the order of scratch hardness – Z100 > Filtek Supreme > Tetric-C, Tetric-EC > Gradia-DP. Significance Scratch tests could roughly categorize a new material as to whether it will probably exhibit a high or low in vitro scratch resistance and/or clinical CFOA wear rate.status: publishe

Enamel loss and adhesive remnants following bracket removal and various clean-up procedures in vitro

This study evaluated the enamel loss and composite remnants after debonding and clean-up. The tested null hypothesis is that there are no differences between different polishing systems regarding removing composite remnants without damaging the tooth surface. Brackets were bonded to 75 extracted human molars and removed after a storage period of 100 hours. The adhesive remnant index (ARI) was evaluated. The clean-up was carried out with five different procedures: 1. carbide bur; 2. carbide bur and Brownie and Greenie silicone polishers; 3. carbide bur and Astropol polishers; 4. carbide bur and Renew polishers; and 5. carbide bur, Brownie, Greenie and PoGo polishers. Silicone impressions were made at baseline (T0) and after debonding (T1) and polishing (T2) to produce plaster replicas. The replicas were analysed with a three-dimensional laser scanner and measured with analytical software. Statistical analysis was performed with the Kruskal-Wallis test and pairwise Wilcoxon tests with Bonferroni-Holm adjustment (α = 0.05). Enamel breakouts after debonding were detectable in 27 per cent of all cases, with a mean volume loss of 0.02 mm(3) (±0.03 mm(3)) and depth of 44.9 μm (±48.3 μm). The overall ARI scores was 3 with a few scores of 1 and 2. The composite remnants after debonding had a mean volume of 2.48 mm(3) (±0.92 mm(3)). Mean volume loss due to polishing was 0.05 mm(3) (±0.26 mm(3)) and the composite remnants had a mean volume of 0.22 mm(3) (±0.32 mm(3)). There were no statistically significant differences in volumetric changes after polishing (P = 0.054) between the different clean-up methods. However, sufficient clean-up without enamel loss was difficult to achieve

Nanohybrid and microfilled hybrid versus conventional hybrid composite restorations: 5-year clinical wear performance

The 5-year findings of a randomized clinical trial testing the null hypothesis that there are no differences between the clinical-wear performances of nano-, microfilled-, and conventional hybrids placed in class I and class II cavities are reported. Effects of subject-, operator-, and restoration-related variables on wear were assessed. Sixteen Tetric-C, 17 Tetric-EC, and 16 Gradia-DP restorations were placed in human molars and recalled at baseline, 6 months and at yearly intervals. The gypsum replicas at each recall were scanned (3D laser scanning), epoxy resin replicas were observed under scanning electron microscope and linear mixed models were used to study the influence of different variables on wear. The generalized vertical wear rate/month were (1.4 μm Tetric-C and Tetric-EC; 1.8 μm Gradia-DP) and volume wear rate/month were (0.017 mm(3) Tetric-EC; 0.018 mm(3) Gradia-DP, and 0.011 mm(3) Tetric-EC). Operator-cavity type interaction and surface area of restorations did significantly influence the volume wear rates (p < 0.05). The three wear patterns: fatigue cracks at heavy occlusal contact area/OCA, pitting at light OCA, and scratches/striations along the food escape pathways were evident. The three hybrids differed significantly in volume wear due to material and operator variables. Clinical relevance: Clinically, operators and cavity type can affect restorations' wear magnitude but do not contribute to increased functional risk of fracture or harmful effect on pulp and periodontal biocompatibility.status: publishe

Three-year randomized clinical trial to evaluate the clinical performance and wear of a nanocomposite versus a hybrid composite

OBJECTIVES: Compare the 3-year clinical performance (wear as an additional parameter) of a nanocomposite and a microhybrid composite, versus ADA guidelines (2001) using direct (clinical/USPHS) and indirect (quantitative/3D laser scan and qualitative/SEM) methods, in parallel. MATERIALS AND METHODS: 18 Filtek Supreme and 17 Z100 restorations were placed in molars (split mouth model) and bonded with Single bond Adhesive. Restorations were evaluated at baseline and 6-, 12-, 24-, 36-months of clinical service according to modified USPHS criteria. The gypsum replicas at each recall were used for 3D-Pro-laser scanning to quantify wear and the epoxy resin replicas were observed under SEM to study the qualitative wear patterns. Repaired restorations were considered functionally present and not failed. Restorations were judged as failed, whenever completely replaced or when scored Delta due to material related factors impairing clinical function. RESULTS: Filtek Supreme appeared better polishable than Z100 (p=0.0078; McNemar test). However, there were no significant differences between groups for other criteria including wear (p>0.05; Mann-Whitney U test). Qualitatively, fatigue wear at heavy occlusal contact areas (OCA), pitting at light OCA and scratches/striations along the food escape pathways were evident in almost all worn surfaces under SEM. CONCLUSIONS: At 3 years, nanocomposite and microhybrid composite meet ADA Acceptance Guidelines (2001) for tooth-colored restorative materials for posterior teeth.status: publishe