Microleakage in class II restorations of two bulk fill resin composites and a conventional nanohybrid resin composite: an in vitro study at 10,000 thermocycles.

BACKGROUND: The contraction presented by resin composites causes an increase in stress at the tooth-resin interface, causing micro-gaps that allow microleakage. This study aims to evaluate the degree of in vitro marginal microleakage in class II restorations with two bulk fill resin composites compared to a conventional nanohybrid resin composite. METHODS: The present study was an in vitro experimental design. A total of 30 standardized class II cavities were prepared in 15 human molars (mesially and distally). These cavities were later distributed in 3 groups according to the type of resin. Groups A and B were restored with bulk fill resin composites (Filtek-3 M/ESPE and Tetric N-Ceram-Ivoclar/Vivadent respectively) in a single increment of 4 mm. Group C was restored with the Filtek Z350 XT - 3 M/ESPE resin composite and two increments of 2 mm. Later, the restorations were subjected to 10,000 thermocycles between 5 °C to 55 °C and immersed in a silver nitrate solution (1 M for 24 h). The crowns were then sectioned mesiodistally and observed under the stereomicroscope to determine the degree of marginal microleakage at the occlusal and cervical areas. The results were analyzed with the Kruskal-Wallis and the Mann-Whitney U statistical tests. RESULTS: There were no statistically significant differences regarding the degree of microleakage between the three types of resin composites in the occlusal and cervical areas (p > 0.05). Similarly, there were no significant differences after comparing each resin type in its occlusal and cervical area (p > 0.05). CONCLUSION: Filtek Bulk Fill and Tetric N-Ceram Bulk Fill resin composites showed no statistically significant differences with the conventional nanohybrid resin composite Filtek Z350XT at both occlusal and cervical areas.

Cleaning of endodontic files with and without enzymatic detergent by means of the manual method versus the ultrasonic method: An experimental study.

AIM: The aim of this article is to evaluate the cleanliness level achieved with and without the application of enzymatic detergent for the manual method versus the ultrasonic method, applied to Flexoreamer K-type files No. 25, No. 30, and No. 35. MATERIALS AND METHODS: 192 K-type Flexoreamer files were divided into four categories: A1 (ultrasonic method with enzymatic detergent), A2 (ultrasonic method without enzymatic detergent), B1 (manual method with enzymatic detergent), and B2 (manual method without enzymatic detergent). Each category was randomly distributed in three groups of 16 files each (No. 25, No. 30, and No. 35). The files were used for biomechanical instrumentation of the root canal in premolars. The active part of the files was examined under a stereomicroscope, considering four cleaning levels: 4 (100% cleanliness), 3 (95-99% cleanliness), 2 (85-94% cleanliness), 1 (75-84% cleanliness), and 0 (less than 75% cleanliness). For hypothesis testing, the Mann-Whitney U-test was used to differentiate between techniques, and the Kruskal-Wallis multiple comparison test was used to compare pairs of files within each cleaning method. RESULTS: When using enzymatic detergents, the manual and ultrasonic methods did not show significant differences when comparing each group of the files analyzed (P > 0.05). However, when comparing the cleaning level without enzymatic detergent between the manual and ultrasonic methods, we observed that it obtained a superior result when compared with the manual method for each type of file: No. 25 (P = 0.021), No. 30 (P < 0.001), and No. 35 (P < 0.001). Both methods achieved a significantly higher level of cleaning with the application of the enzymatic detergent (P < 0.05) than without applying it. CONCLUSION: The ultrasonic cleaning method proved to be the most effective method for the removal of biologic waste when compared with the manual method using a nylon brush. However, there was no significant difference between these two methods when enzymatic detergent was used.