Background One of the problems with a high filler content composite resins is gap formation at restorative material–tooth interface. The present study investigated the effect of preheating composite resins on the formation of marginal gap in Cl II restorations. Material and Methods In this in vitro study Sixty Cl II cavities were prepared on the mesial and distal surfaces of 30 extracted premolar teeth. The gingival floor of cavities was placed 1 m below the CEJ. The samples were randomly allocated to 4 groups for restoration placement: group 1, Filtek P60 composite resin at room temperature; group 2, Filtek P60 composite resin at 68°C; group 3, X-tra fil composite resin at room temperature; and group 4, X-tra fil composite resin at 68°C. After a thermocycling procedure, the teeth were sectioned longitudinally in a buccolingual direction. Then the marginal gaps of the samples were measured at proximal and gingival margins under a scanning electron microscope at ×2000 magnification in µm. The data were analyzed with SPSS 21, using one-way ANOVA, post hoc Tukey tests and paired t-test (α=0.05). Results Groups 2 and 4 exhibited significantly lower marginal gaps, compared to groups 1 and 3, at both enamel ( P <0.0001 and P =0.001, respectively) and dentinal walls ( P <0.0001). In all the groups, there was significantly less marginal gaps at composite-enamel wall compared to composite-dentin wall interfaces ( P <0.0001). There was no significant difference between groups 1 and 3 and groups 2 and 4 in enamel walls ( p = 0.96, p = 0.99 respectively) and dentinal walls ( p = 0.85, p =0.98 respectively). Conclusions Preheating resulted in a decrease in marginal gaps in both composite resins. The effect of composite resin type on marginal adaptation was the same. Key words: Composite resin, dental marginal adaptation, preheating.

Deciding whether to replace or preserve a compromised tooth, even with emerging trends in implant dentistry, is still a common dilemma for practitioners. This study sought to determine the 3- to more than 10-year survival rate of teeth that had undergone endodontic, periodontal and prosthodontic treatments. A total of 245 teeth in 87 patients were clinically and radiographically evaluated. All the teeth had received crown lengthening surgery by a single periodontist. Root canal therapy and prosthodontic procedures were rendered either by specialists or by experienced general dentists. Numbers of lost teeth were recorded and the criteria for hopeless teeth were defined. Survival rate was determined using the Kaplan-Meier estimator. Clinical indices including pocket depth (PD), bleeding index (BI), C/R ratio, position of the restoration margin relative to the gingival margin (RM-GM) and the presence of intra-canal post were compared between different survival groups (<3, 3-5, 5-10 and >10 years) using one-way analysis of variance (anova). Potential predictors of failure were determined using the Cox regression model. The mean ± s.d. of 3-, 5-, 10- and 13-year survival rates was 98 ± 1%, 96 ± 1·6%, 83·1 ± 4·5% and 51·9 ± 14·5%, respectively. The mean PD (P < 0·013), as well as C/R ratio in the mesial (P = 0·003) and distal (P = 0·007) surfaces, was significantly higher in the >10-year-survived teeth. Bleeding index and RM-GM showed no significant differences between the groups. C/R ratio and RM-GM position appeared to be the major determinants of tooth loss. The long-term survival rate of multidisciplinary-treated teeth was 83-98% in this specific sample.

Background: One of the concerns in using composite resins is color change. The aim of this study was to investigate the effect of preheating on color stability of composite resins when immersed in coffee and tea. Material and Methods: this experimental study included 60 composite disks. The samples were divided into 2 groups, one group prepared at room temperature and the other prepared at 68°C. After curing, the samples were placed in 37 °C distilled water for 24 hours. The color of the samples was measured (t0) using spectrophotometer according to CIE-L*a*b* system. The samples of each group were then divided into 3 subgroups and respectively immersed in distillated water, coffee and tea for 30 days and the final color (t1) was measured. The difference between the measured colors was calculated (∆E) and the results were analyzed using version 21.0 of SPSS software, Paired t-test, ANOVA, Tukey's test, and Dunnett t-test. Results: The preheated composites showed significantly lower staining in the coffee solution than the room temperature composites (p<0.0001). In contrast, no statistically significant difference was observed for the tea solution (p=0.317). The staining of the preheated composites in distillated water was higher than those in the room temperature, however, the difference was not significant (p=0.99). Conclusions: Within the limits of this study, preheating was effective to improve color stability of composite resin after long time immersion in coffee solution.

Introduction: Mouthwashes which prevent and control caries and periodontal diseases are commonly used even without professional prescription. Long-term use of mouthwashes may cause softening of restorative composites and lowering the longevity of restoration. The aim of this study was evaluation of surface hardness value of a microhybride composite (Filtek Z250) after 12 hours immersion in three kinds of alcohol-free mouthwashes. Materials and Methods: 72 Cylinderical specimens of a microhybride composite 5mm wide were prepared, using drinking straw as a mold. Specimens were light-cured continuously for 40 seconds on each side with Elipar(3M,ESPE) curing light. The specimens were immersed in 50ml of distilled water for12 hours. After that, all of them were finished with silicone carbide papers under constant water as coolant. The specimens were divided into 4 groups, each with 18 samples, the first group immersed in Colgate plax , the second in Crest (pro-health for me) , group3 in OraCare and group4 in water as the control group for 12 hours, which is equivalent to 1 year of daily mouthwash use at 2 minutes per day. Hardness measurement was taken by Vickers hardness tester with 1 kilogram load and 10 seconds loading time. Result: Statistical analysis according to t-test and One-Way ANOVA test showed that there was no significant difference in surface hardness value of composite after 12 hours immersion between groups of mouthwashes and water(P value=0.353) Conclusion: Based on the present study, alcohol-free mouthwashes didn't affect the surface hardness of Filtek(Z250) composite.

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