Polishing performance of multiple-use silicone rubber-based polishing instruments with and without disinfection/sterilization.

PURPOSE: To evaluate the effect of the multiple-use of a three-step rubber-based polishing system on the polishing performance with and without a disinfection/sterilization protocol with prolonged disinfection (overnight). METHODS: The three-step polishing system Astropol was applied under standardized contact pressure of 2 N on 320 grit pre-roughened flat composite specimens of Tetric EvoCeram for 10 seconds (F and P disc) and 30 seconds (HP disc) respectively. After each polishing step, the surface gloss and roughness were measured with a glossmeter and an optical sensor (FRT MicroProf), respectively. Material loss of the composite specimens and polishing instruments were measured after each step with a high precision digital scale. For all four variables (surface gloss, surface roughness, composite loss, loss of rubber material) the mean percentage of change compared to the reference was calculated. RESULTS: Already after the first use, the instruments which were used without disinfection or sterilization demonstrated a statistically significantly reduced polishing performance in all polishing steps compared to the reference (new polishing system) (t-test, P < 0.05). In addition, this loss in performance further increased with the second and third re-use. Especially the third component (Astropol HP) was affected by performance loss. By contrast, the multiple-use of the instruments which were subjected to prolonged disinfection did not result in a reduced polishing performance. For the P disc, a statistically significant improvement of the polishing performance could be observed throughout almost all multiple-use sessions (ANOVA, P < 0.05). The improved polishing performance was, however, accompanied by an increased loss of the silicone rubber material of the P and F polishing discs; the HP discs were not affected by this loss. Furthermore, particles of the rubber material also adhered to the composite. The polishing performance of the discs which were only subjected to the sterilization process was not statistically significantly different to the polishing performance of the control group in terms of surface roughness; but the surface gloss was worse than that of the control group. No loss of rubber material or adherence to the composite was observed in this group.

Microleakage of Class II restorations with different tracers--comparison with SEM quantitative analysis.

PURPOSE: (1) To compare SEM quantitative marginal analysis data with the depth of penetration (DP) of the three most commonly used tracers for microleakage in Class II fillings in vitro; (2) based on the obtained results to calculate the discriminatory power of a sample size of 12. MATERIALS AND METHODS: Standardized large cavities (mesially 1 mm above the CEJ, distally 1 mm below the CEJ, intercuspal distance 70%) were prepared into 36 extracted caries-free first mandibular molars and filled with Tetric EvoCeram/AdheSE, the resin being applied in horizontal layers 2 mm thick. Each increment was light cured for 20 s (1200 mW/cm2). Finishing was performed with fine diamond burs and disks. All teeth were subjected to occlusal loading (1,200,000 cycles, 49 N/1.7 Hz) and simultaneous thermocycling (3000 cycles at 5 degrees C/55 degrees C). The percentage of continuous margin of the cervical dentin and enamel was evaluated on replicas using SEM. The teeth were subjected to tracer penetration with either 0.5% basic fuchsin (24 h, 37 degrees C), 2% methylene blue (24 h, 37 degrees C) or 50% silver nitrate solution (4 h, 37 degrees C, followed by 8-h exposure to a photodeveloping solution and overnight fluorescent light). The teeth were mesiodistally sectioned twice. The depth of tracer penetration was measured with a stereomicroscope and averaged for each site. Due to data inhomogeneity and abnormal distribution, both SEM and DP data were transformed. Sample size calculations were performed based on standard deviation and statistical error estimates. RESULTS: For the dentin margin, there was an acceptable correlation between SEM data and both fuchsin penetration (Pearson: -0.74, p < 0.01) and silver nitrate penetration (Pearson: -0.79, p < 0.01), but not between methylene blue and SEM data. For enamel margins, no significant correlation between SEM and DP data was found for the three tracers. There was statistically no significant difference in tracer penetration between the three tracers (Kruskal Wallis, p > 0.05). For all three tracers, statistically significantly higher penetration occurred at the dentin than at the enamel margin (Wilcoxon, p < 0.05). A sample size of 12 makes it possible to discriminate between materials only when they differ in tracer penetration in the range of 1 mm for enamel and 2 mm for dentinal margins. CONCLUSION: Tracer penetration with fuchsin or silver nitrate showed a moderate correlation with SEM quantitative marginal analysis data at dentinal margins, but not at enamel margins.

Automated margin analysis of contemporary adhesive systems in vitro: evaluation of discriminatory variables.

PURPOSE: Using an optical sensor, to automatically evaluate the marginal seal of restorations placed with 21 adhesive systems of all four adhesive categories in cylindrical cavities of bovine dentin applying different outcome variables, and to evaluate their discriminatory power. MATERIALS AND METHODS: Twenty-one adhesive systems were evaluated: three 3-step etch-and-rinse systems, three 2-step etch-and-rinse systems, five 2-step self-etching systems, and ten 1-step self-etching systems. All adhesives were applied in cylindrical cavities in bovine dentin together with Tetric Ceram (n=8). In the control group, no adhesive system was used. After 24 h of storage in water at 37 degrees C, the surface was polished with 4000-grit SiC paper, and epoxy resin replicas were produced. An optical sensor (FRT MicroProf) created 100 profiles of the restoration margin, and an algorithm detected gaps and calculated their depths and widths. The following evaluation criteria were used: percentage of specimens without gaps, the percentage of gap-free profiles in relation to all profiles per specimen, mean gap width, mean gap depth, largest gap, modified marginal integrity index MI. The statistical analysis was carried out on log-transformed data for all variables with ANOVA and post-hoc Tukey's test for multiple comparisons. The correlation between the variables was tested with regression analysis, and the pooled data accordingto the four adhesive categories were compared by applying the Mann-Whitney nonparametric test (p < 0.05). RESULTS: For all the variables that characterized the marginal adaptation, there was a great variation from material to material. In general, the etch-and-rinse adhesive systems demonstrated the best marginal adaptation, followed by the 2-step self-etching and the 1-step self-etching adhesives; the latter showed the highest variability in test results between materials and within the same material. The only exception to this rule was Xeno IV, which showed a marginal adaptation that was comparable to that of the best 3-step etch-and-rinse systems. Except for the variables "largest gap" and "mean gap depth", all the other variables had a similar ability to discriminate between materials. Pooled data according to the four adhesive categories revealed statistically significant differences between the one-step self-etching systems and the other three systems as well as between two-step self-etching and three-step etch-and-rinse systems. CONCLUSIONS: With one exception, the one-step self-etching systems yielded the poorest marginal adaptation results and the highest variability between materials and within the same material. Except for the variable "largest gap", the percentage of continuous margin, mean gap width, mean gap depth, and the marginal integrity index MI were closely related to one another and showed--with the exception of "mean gap depth"--similar discriminatory power.

Surface roughness of different dental materials before and after simulated toothbrushing in vitro.

This study measured the effect of toothbrushing with a slurry of toothpaste on different dental materials that have been optimally polished. Specimens (n=8) of 21 dental materials, 16 resin composites, 1 amalgam and 4 ceramic materials, were subjected to 36,000 cycles (approximately five hours) of circular toothbrushing with a force of 1.7 N and a slurry of toothpaste (RDA 75) in a device for simulated toothbrushing. The unpolished enamel and dentin of extracted anterior teeth were used as a control. The mean roughness (Ra) was measured with an optical sensor (FRT MicroProf) before and after toothbrushing. To compare the roughness of the different materials, ANOVA with a post hoc Tukey B test was applied (p<0.05). Among the resin composites, the hybrid composites showed the greatest increase in mean roughness, while the microfilled composites and the compomer Compoglass F demonstrated the lowest increase. No statistically significant difference in roughness was found before and after simulated toothbrushing for the Amalcap amalgam, Esthet-X resin composite, TPH Spectrum resin composite, d.SIGN ceramic and the experimental ceramic. The other ceramic materials and dentin and enamel specimens showed a statistically significant decrease in mean roughness after simulated toothbrushing. Glazed Empress demonstrated a statistically significant higher initial roughness than polished Empress. For resin composites, no correlation was found between the mean particle size and mean roughness after simulated toothbrushing.

Automatic gap detection at restoration margins with an optical sensor in vitro.

PURPOSE: To develop and validate a software program which automatically detects gaps of cylindrical fillings in bovine dentin by using an optical sensor (FRT MicroProf), evaluate 8 different adhesive systems with the defined parameters, and compare the results with that of SEM quantitative marginal analysis. MATERIALS AND METHODS: An optical measuring head with strong wavelength dependency on its focal length splits white light into its colors. The surface height can be measured from the wavelength of the reflected light (resolution: x/y 1 to 2 microm, z 10 nm). A profile of the surface is taken by scanning the measuring point radially from the center of the filling over the restoration margins. An algorithm detects gaps and calculates their depths and widths. Eight adhesive systems (AdheSE, Clearfil SE, Excite, iBond, Optibond Solo Plus, Prompt L-Pop, Touch and Bond, Xeno III) were applied in cylindrical cavities (n = 8, ø = 4 mm, depth 2.5 mm, C-factor 3.5) in bovine dentin together with Tetric Ceram. In the control group, no adhesive system was used. After 24 h of storage in distilled water at 37 degrees C, the surface was polished with 4000-grit abrasive paper, and then epoxy resin replicas were produced. The evaluation criteria were as follows: the percentage of continuous margin along the entire margin (SEM, 500X) and the percentage of gap-free profiles to total profiles (FRT MicroProf), the latter being evaluated by using 100, 300 and 1000 profiles per sample. Two groups (Touch and Bond, Optibond Solo Plus) with 16 samples were selected to evaluate reproducibility and the occurrence of voids adjacent to the restoration margins. For each adhesive, a paired t-test was applied to evaluate the differences between both test methods for each adhesive. A linear regression analysis procedure was used to evaluate the overall agreement between the two test methods. RESULTS: The mean deviation between three consecutive measurements was 2.75%. Ten percent of all profiles showed voids adjacent to the restoration margins; 92% of the voids were excluded by setting the threshold value of the gap width at 20 microm. In less than 1% of the profiles, the concurrent presence of gap and void resulted in the nondetection of gaps. It was found that 100 profiles per sample are sufficient to characterize a sample as compared to SEM analysis. Except for the control group, the paired t-test did not reveal any statistically significant difference between the two test methods for either adhesive (p < 0.05). Regression analysis for all 72 data points yielded R2 = 0.72 (p < 0.0001). CONCLUSION: The results of the quantitative marginal analysis by means of the FRT optical sensor are comparable to those obtained by SEM. The advantages of this method include (1) saving of operator time, (2) independence of operator's experience and bias, and (3) additional information about the gap width and depth.