Background: Repair bond strength of different composite resins has been assessed in few studies. In addition, reports on the efficacy of surface treatments are debated. Therefore, this in vitro study was conducted to evaluate the effect of three surface treatments on two nanocomposites versus a microhybrid composite. Materials and Methods: In this experimental study, 135 composite blocks (45 specimens per composite) of microhybrid (Filtek Supreme Z250, 3M ESPE, USA), nanohybrid (Filtek Supreme XT, 3M ESPE), and nanofilled (Filtek Supreme Z350, 3M ESPE) were thermocycled (5000 rounds) and then surface roughened (except in a control group of 9 specimens of three composite types). Each composite type was divided into three subgroups of surface treatments: (1) Bur abrading and phosphoric acid (PA) etching, (2) sandblasting and PA etching, and (3) hydrofluoric etching and silane application (n = 15 × 9, complying with ISO TR11405). Composite blocks were repaired with the same composite type but of a different color. Microtensile bond strength and modes of failure were analyzed statistically using two-way analyses of variance, Tukey and Chi-square tests (α = 0.05). Results: There were significant differences between three composite resins (P < 0.0001) and treatment techniques (P < 0.0001). Their interaction was nonsignificant (P = 0.228). The difference between nanofilled and nanohybrid was not significant. However, the microhybrid composite showed a significantly higher bond strength (Tukey P < 0.05). Sandblasting was significantly superior to the other two methods, which were not different from each other. Conclusion: Within the limitations of this in vitro study, it seems that microhybrid composite might have higher repair strengths than two evaluated nanocomposites. Among the assessed preparation techniques, sandblasting followed by PA etching might produce the highest bond strength.

Background: The purpose of this study was to compare the clinical performance of Class II direct and indirect composite restorations according to the United States Public Health Service criteria (USPHS). Materials and Methods: Seventy patients were included and four different composite resins, P60 (FP), SureFil Posterior (SP), Gradia Posterior (GP), and Bisco Aelite LS Packable (BAP) were used as direct restorative material. All of the composite resins except BAP were used as indirect restorative material. Instead of BAP, Tescera Laboratory composites were polymerized in Tescera inlay oven. All restorations were evaluated according to USPHS criteria during a one-year period. Results: There were no statistically significant differences between direct and indirect composite restorations according to the retention, marginal discoloration, surface staining, proximal contact continuity, and secondary caries. Indirect restorations have less surface roughness, postoperative sensitivity (P < 0.05), and soft tissue irritation (P < 0.1) than direct ones. Conclusion: The clinical performances of the indirect restorations were more satisfactory than the direct restorations.

Objective: The aim of this study was to evaluate the change in surface hardness of silorane-based composite resin (Filtek Silorane) in time and compare the results with the surface hardness of two methacrylate-based resins (Filtek Supreme and Majesty Posterior). Materials and Methods: From each composite material, 18 wheel-shaped samples (5-mm diameter and 2-mm depth) were prepared. Top and bottom surface hardness of these samples was measured using a Vicker's hardness tester. The samples were then stored at 37°C and 100% humidity. After 24 h and 7, 30 and 90 days, the top and bottom surface hardness of the samples was measured. In each measurement, the rate between the hardness of the top and bottom surfaces were recorded as the hardness rate. Statistical analysis was performed by one-way analysis of variance, multiple comparisons by Tukey's test and binary comparisons by t-test with a significance level of P = 0.05. Results: The highest hardness values were obtained from each two surfaces of Majesty Posterior and the lowest from Filtek Silorane. Both the top and bottom surface hardness of the methacrylate based composite resins was high and there was a statistically significant difference between the top and bottom hardness values of only the silorane-based composite, Filtek Silorane (P < 0.05). The lowest was obtained with Filtek Silorane. The hardness values of all test groups increased after 24 h (P < 0.05). Conclusion: Although silorane-based composite resin Filtek Silorane showed adequate hardness ratio, the use of incremental technic during application is more important than methacrylate based composites.

Objective: The aim of this study was to evaluate the effect of three mouthwashes on color changes of three composite resins stained with tea. Materials and Methods: Fifty specimens were prepared for each of the three composite resins [Clearfil Majesty Esthetic (CME), Filtek Z250 (Z25), and Charisma (CH)], and the specimens were then stained in a tea solution. Each composite group was randomly divided into five subgroups (n = 10) according to the product applied: Distilled water (DW) (negative control); Crest 3D White mouthwash (CR); Listerine whitening mouthwash (LS); Scope White SC mouthwash (SC), and Opalescence PF gel (OP) (10% carbamide peroxide, positive control). The color of the specimens was measured with a spectrophotometer at baseline, after staining, and on the 7th, 28 ^th , and 56 ^th days of the treatment period. The color differences (ΔE) were analyzed with a three-way analysis of variance (ANOVA), followed by Tukey's test (P < 0.05). Results: Compared with the clinically acceptable threshold unit, the level of staining on all the composite resins was considerably high (ΔE > 3.3). The composite resin, mouthwash, immersion time, and their interaction had a significant effect on the color change procedure (P < 0.05), but the immersion time × mouthwash × composite did not. Conclusion: The discoloration of the specimens after immersion in the mouthwashes decreased significantly over time. Only the staining of the CME specimens treated with CR, LS, and OP decreased to a clinically acceptable level at the end-treatment period.

Aim: The aim of this study was to evaluate the microhardness of two composite resins when subjected to three different temperatures and three different light-curing times. Materials and Methods: Two composites were used; Filtek Z250 and Grandio. Three different temperatures (23, 37, and 55 ^o C) were used, utilizing a composite warmer. The heated samples were immediately injected into cylindrical molds (6 mm × 2 mm) and the top surface of the specimens was polymerized for 10, 20, and 40 sec, using a Quartz-Tungsten-Halogen light-curing unit (QTH LCU). Vickers microhardness measurements were performed from both the top and bottom surface of the specimens, following dry storage for 24 hours in the dark. Statistical analysis were performed using one-way analysis of variance (ANOVA) and Tukey post-hoc test at a level of significance of a = 0.05. Results: The results indicated that there was an increase in microhardness as the temperature of the composite was increased for either the top or the bottom surface (P < 0.05). Furthermore, there was a general increase in microhardness for both composites as curing time increased (P < 0.05). The type of composites did not influence the surface microhardness (P > 0.05). Conclusions: Temperature of composites affects their surface microhardness. Also, light-curing time influence microhardness values of the composites tested.

Objective: The objective was to investigate the way that various surface treatments could influence the bond strength of the repair of methacrylate (MC) and silorane (SIL) composites. Materials and Methods: A total of 160 MC and SIL cylindrical specimens were polymerized and aged in artificial saliva solution for 7 days. Depending on the following surface treatment (diamond bur or air abrasion), and the conditioning procedure (orthophosphoric acid or sodium hypochlorite), 16 groups were formed and repaired either with MC, either with SIL composite. Repaired specimens were subjected to an additional aging procedure in artificial saliva for 7 days, followed by thermo-cycling and then stressed in shear at a rate of 0.5 mm/min until failure. Failure patterns were analyzed using stereomicroscope and scanning electron microscopy . Results: MC composite showed statistically significant higher bond strength both as a base or repair material than SIL (P < 0.001). Statistically significant differences were not observed, when grinding and conditioning procedures was compared. Pretest failures were observed when aged MC-based composite was repaired with SIL-based. Conclusions: Type of composite seems to be the main factor influencing the bond strength of the repair. MC-based composite showed better repairability than SIL composite. Optimum repair conditions should include knowledge of the composite's composition.

Aim: The aim of this in vitro study was an attempt to investigate the effect of different surface treatments on the bond strength between pre-existing composite and repair composite resin. Materials and Methods: Forty acrylic blocks were prepared in a cuboidal mould. In each block, a well of 5 mm diameter and 5 mm depth was prepared to retain the composite resin (Filtek™ Z350, 3M/ESPE). Aging of the composite discs was achieved by storing them in water at 37°C for 1 week, and after that were divided into 5 groups (n = 8) according to surface treatment: Group I- 37% phosphoric acid, Group II-10% hydrofluoric acid, Group III-30% citric acid, Group IV-7% maleic acid and Group V- Adhesive (no etchant). The etched surfaces were rinsed and dried followed by application of bonding agent (Adper™ Single Bond 2. 3M/ESPE). The repair composite was placed on aged composite, light-cured for 40 seconds and stored in water at 37°C for 1 week. Shear bond strength between the aged and the new composite resin was determined with a universal testing machine (crosshead speed of 0.5 mm/min). Statistical Analysis: The compressive shear strengths were compared for differences using ANOVA test followed by Tamhane's T2 post hoc analysis. Results: The surface treatment with 10% hydrofluoric acid showed the maximum bond strength followed by 30% citric acid, 7% maleic acid and 37% phosphoric acid in decreasing order. Conclusion: The use of 10% hydrofluoric acid can be a good alternative for surface treatment in repair of composite resin restoration as compared to commonly used 37% orthophosphoric acid.

Aim: To evaluate the effect of prepolymerized custom-made composite megafiller and configuration factors (C-factor) on marginal adaptation of resin composite restorations. Materials and Methods: Forty extracted human mandibular molars were divided into four experimental groups consisting of 10 samples each. In groups I and III, class V (configuration factor 5) and in groups II and IV, class II box-shaped cavities (configuration factor 2) were prepared. Groups I and II were restored with a nanofilled composite (Filtek™ Z350 3M ESPE, St Paul, MN, USA) placed in horizontal increments. In groups III and IV, preformed composite megafiller was placed and cavities were restored with nanofilled composite Z-350. After curing, the samples were finished and prepared for examination under low vacuum scanning electron microscope. The data were analyzed with one-way analysis of variance. The significance between the individual groups was calculated by Post hoc test using the Holm-Sidak method ( P≤0.05). Results: The marginal gap values in groups III and IV were significantly lower than in groups I and II, respectively ( P≤0.05). Minimum gap values were seen in group IV. Conclusion: Use of prepolymerized composite megafiller and a lower C-factor decreased the marginal gaps between the tooth and composite restorations.

Aim: The study aims to evaluate and compare marginal microleakage in deep class II cavities restored with various techniques using different composites. Materials and Methods: Sixty freshly extracted teeth were divided into six groups of 10 teeth each. Standardized class II cavities were made and were restored using composites of different consistencies with different placement techniques. Group 1 with Microhybrid composite, Group 2 with Packable composite, Group 3 Microhybrid composite with a flowable composite liner, Group 4 Packable composite with a flowable composite liner, Group 5 Microhybrid composite with precured composite insert in second increment and Group 6 Packable composite with precured insert in second increment. Specimens then were stored in distilled water, thermocycled and immersed in 50% silver nitrate solution. These specimens were sectioned and evaluated for microleakage at the occlusal and cervical walls separately using stereomicroscope. Results: The results demonstrated that in the occlusal wall, packable composite, showed significantly more marginal microleakage than the other groups. In the cervical wall, teeth restored with a flowable composite liner showed less marginal microleakage when compared to all other groups. Conclusion: Based on the results of this study, the use of flowable composite as the first increment is recommended in deep class II cavities.

Background: The restorative materials used in dentistry are required to have long-term durability in the oral cavity. Effect of various fluids in the oral environment can affect the hardness of these restorations. This study was carried out to evaluate the effect of different mouth rinses on the hardness of Silorane and Nano-hybrid resin composites. Materials and Methods: Thirty specimens were prepared from each type of composite and stored in artificial saliva for 24 h at 37°C. They were then divided into six experimental groups based on the test solution and were immersed and stored for 24 h at 37°C. Thereafter, the specimens were washed, dried and the hardness was measured for each specimen by Vickers microhardness tester. Results: Nano-hybrid resin composite showed higher Vickers hardness number (VHN) than Silorane composite in any test solution. There was only a mildly significant difference in the mean VHN of Silorane composite immersed in alcohol-containing mouthwash compared with artificial saliva. However, there was a significant difference in the mean VHN of Nano-hybrid composite when immersed in different mouthwashes. Conclusion: The microhardness values of Silorane-based and Nano-hybrid resin composites were decreased after immersion in the mouthwashes. The hardness of Nano-hybrid composite immersed in artificial saliva showed the highest VHN and was significantly affected when immersed in other test solutions. Silorane-based composite is more resistant to alcohol-containing mouthwash than Nano-hybrid composite.