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Aim The aim of the present study was to evaluate the effect of the application of a hydrophobic resin on the microleakage of Cl V composite resin restorations using a universal adhesive system applied in the self-etch ( SE) and etch-and-rinse ( ER) modes. Method Cl V cavities were prepared on the buccal surfaces of 64 human premolar teeth and divided into four groups ( n = 16): ER, ER with hydrophobic resin ( ERH), SE, and SE with hydrophobic resin ( SEH). Microleakage at occlusal and gingival margins was evaluated using 0.5% methylene blue dye penetration technique under stereomicroscope at 40 × magnification. Data were analyzed using Kruskal-Wallis and Mann-Whitney U-tests ( P < 0.05). Results At the enamel margins, the ER group had significantly less microleakage than the SE and SEH groups ( P < 0.001), but had no significant difference compared with the ERH group ( P > 0.05). There was also no statistically-significant difference between the SE and SEH groups ( P > 0.05). At the dentinal margins, the SE group had significantly less microleakage compared with the ER ( P < 0.001) and ERH groups ( P = 0.005). Furthermore, microleakage of the SEH group was significantly less than the SE group ( P < 0.001). Conclusion Applying an extra layer of hydrophobic resin significantly decreased microleakage in the SE mode at the dentinal margin, but had no significant effect in the ER mode. [ABSTRACT FROM AUTHOR]

Objectives: The present study aimed to investigate the effect of preheating on the color stability and surface roughness of a silorane-based composite resin. Materials and Methods: A total of 44 Filtek P90 composite resin disks, (10mm×1mm), were fabricated using plastic molds and were divided into two groups. In group 2, the composite resin syringes were placed in a thermostatically controlled water bath at 55‒60°C before preparing the disks. After polishing the samples with silicon carbide papers, they were stored in distilled water for 48 hours. Roughness and color parameters were then measured in two stages: immediately after retrieval from distilled water and after 40 days of storage in tea solution. Finally, the differences in roughness and color parameters were recorded. Independent sample t-test and regression analysis were used at a significance level of P<0.05. Results: Based on the findings of the present study, there was no significant difference among the mean ∆E values (P=0.4); however, a significant difference in mean surface roughness (P=0.01) was found between the two groups. Regression analysis showed a significant relationship between the study groups in terms of surface roughness and ΔE values​ (preheated: r 2 = 0.73; non-preheated: r 2 = 0.76). Conclusion: Filtek P90 silorane-base composite showed ΔE>3.3 and surface roughness above 0.2µ under preheated and non-preheated conditions and discoloration increased following preheating., (Copyright © 2022 The Authors. Published by Tehran University of Medical Sciences.)

Background: The present study was aimed to evaluate the effect of pre-heating of bulk -fill resin composites on monomer elution from them., Material and Methods: Three different types of resin composites were used including Tetric N-Ceram Bulk Fill, X-tra Fill and X-tra Base. 10 cylindrical samples were prepared from each resin composites. Before light curing, 5 samples were pre-heated until reaching 68˚C, then 5 other samples were polymerized at room temperature. After 24 hours, release of UDMA, TEGDMA and BIS-GMA monomers were measured by High-Performance Liquid Chromatography analysis. Data analysis was performed by two-way ANOVA test, Games-Howell and Sidak post hoc tests., Results: Pre-heating did not have any statistically significant effect on the mean values of UDMA, TEGDMA and Bis-GMA elution ( p >0.05). The greatest amount of released Bis-GMA and UDMA was obtained from Tetric N-Ceram Bulk-fill composite. The greatest amount of released TEGDMA was obtained from X-tra Fill composite. X-tra Base composite showed the lowest amount of monomer release ( P <0.001)., Conclusions: Pre-heating did not have any effect on monomer release from bulk-fill resin composites. Moreover, the amount and the type of monomers released from various bulk-fill resin composites were not similar. Key words: Bulk fill composite resin, elution, HPLC, residual monomer, temperature., Competing Interests: Conflicts of interest There are no conflicts of interest., (Copyright: © 2020 Medicina Oral S.L.)

Background and aims. A proper bond must be created between the existing composite resin and the new one for successful repair. The aim of this study was to compare the effect of three mechanical surface treatments, using diamond bur, air abrasion, and Er,Cr:YSGG laser, on the repair bond strength of the silorane-based composite resin. Materials and methods. Sixty cylindrical composite resin specimens (Filtek Silorane) were fabricated and randomly divided into four groups according to surface treatment: group 1 (control group) without any mechanical surface treatment, groups 24 were treated with air abrasion, Er,Cr:YSGG laser, and diamond bur, respectively. In addition, a positive control group was assigned in order to measure the cohesive strength. Silorane bonding agent was used in groups 14 before adding the new composite resin. Then, the specimens were subjected to a shear bond strength test and data was analyzed using one-way ANOVA and post hoc Tukey tests at a significance level of P &0.05. The topographical effects of surface treatments were characterized under a scanning electron microscope. Results. There were statistically significant differences in the repair bond strength values between groups 1 and 2 and groups 3 and 4 (P &0.001). There were no significant differences between groups 1 and 2 (P = 0.98) and groups 3 and 4 (P= 0.97). Conclusion. Surface treatment using Er,Cr:YSGG laser and diamond bur were effective in silorane-based composite resin repair.

Background and Aims: Considering the importance of disinfecting dentin after cavity preparation and the possible effect of disinfection methods on induction of various reactions between the tooth structure and the adhesive restorative material, the aim of the present study was to evaluate microleakage of composite resin restorations after disinfecting the prepared dentin surface with Nd:YAG and Diode lasers and photodynamic therapy., Materials and Methods: Standard Class V cavities were prepared on buccal surfaces of 96 sound bovine teeth. The samples were randomly divided into 4 groups based on the disinfection method: Group 1: Nd:YAG laser; Group 2: Diode laser; Group 3: photodynamic therapy; and Group 4: the control. Self-etch bonding agent (Clearfil SE Bond) was applied and all the cavities were restored with composite resin (Z100). After thermocycling and immersing in 0.5% basic fuchsin, the samples were prepared for microleakage evaluation under a stereomicroscope. Data was analyzed with Kruskal-Wallis and Wilcoxon signed-rank tests at P<0.05., Results: There were no significant differences in the microleakage of occlusal and gingival margins between the study groups (P>0.05). There were no significant differences in microleakage between the occlusal and gingival margins in the Nd:YAG laser group (P>0.05). In the other groups, microleakage at gingival margins was significantly higher than that at the occlusal margins (P<0.05)., Conclusion: Nd:YAG and Diode lasers and photodynamic therapy can be used to disinfect cavity preparations before composite resin restorations.

Background and Aims: This study was aimed at evaluating the effect of different prophylaxis methods on microleak-age of microfilled composite restorations., Materials and Methods: In this in vitro study, class V cavities were prepared on buccal surfaces of 84 bovine teeth. The teeth were restored with Tetric N-Bond adhesive and Heliomolar composite resin. Subsequent to a thermocycling procedure and three months of storage in distilled water, the teeth were randomly assigned to four groups (n=21): (1) prophylaxis with a rubber cup and pumice; (2) prophylaxis with a brush and pumice; (3) prophylaxis with air/powder polishing device; and (4) no prophylaxis (the control group). Then the teeth were immersed in 2% basic fuchsin for 24 hours and sectioned for microleakage evaluation under a stereomicroscope. Data were analyzed using Kruskal-Wallis and Wilcoxon Signed Rankstests. Statistical significance was defined at p<0.05., Results: There were no statistically significant differences in occlusal and gingival microleakage between the groups (p=0.996 and p=0.860, respectively). In all the groups gingival margins exhibited significantly higher microleakage values compared to occlusal margins (p<0.0005)., Conclusion: Prophylaxis methods had no adverse effect on marginal leakage of microfilled composite resin restorations.

Background and Aims: Salivary glands are extremely susceptible to radiation injuries. The aim of this study was to evaluate radiation-induced xerostomia in patients with nasopharyngeal carcinomas, referring to Tabriz Imam Khomeini Hospital in 2005-2006., Materials and Methods: Thirty patients with nasopharyngeal carcinomas, who received conventional radiotherapy, were included in the present study. The patients' unstimulated saliva samples were collected at three intervals, i.e. before treatment, 3 weeks after the initiation of treatment and at the end of treatment by spitting, and measured with a graduated pipette., Results: The differences in the mean values of the patients' salivary flow rates at three afore-mentioned intervals were statistically significant (p<0.001). Two-by-two comparison of the mean values of salivary flow rates of all the patients and of males and females, carried out separately, demonstrated statistically significant differences (p<0.0025). However, there were no statistically significant differences between males and females before treatment (p = 0.723), 3 weeks after the initiation of treatment (p = 0.724) and at the end of treatment (p = 0.595). There were no statistically significant relationships between age and a decrease in salivary flow rate in the total sample (p = 0.76, r = -0.057), in males (p = 0.96, r = 0.011) and in females (p = 0.539, r = -0.208)., Conclusion: Conventional radiotherapy results in severe xerostomia in 3 weeks in patients with nasopharyngeal carcinomas. Age and sex do not influence radiotherapy-induced xerostomia.