AVALIAÇÃO CLÍNICA E LABORATORIAL DE RESTAURAÇÕES COM RESINA BULK FILL INSERIDAS DE FORMA INCREMENTAL OU EM INCREMENTO ÚNICO

Abstract

Objectives: In the experiment 1, an in vitro study, the aim was to evaluate the microtensile bond strength (μTBS), nanoleakage (NL) and degree of conversion (DC) of different bulk-fill resin-based materials placed in bulk [BUL] or incrementally [INC] and in the experiment 2, a double blind randomized clinical trial, split mouth for each adhesive system, was conducted to compare the postoperative sensitivity of a bulk-fill resin-based material placed in BUL or INC in posterior composite resin restorations bonded with two different adhesive strategies (self-etch and etch-and-rinse). In the experiment 3, the objective was to describe the clinical steps involved in the placement of posterior composite resin restorations with bulk-fill resins. Materials and methods: In experiment 1, flat dentin surfaces of thirty extracted teeth were exposed and then were randomly assigned into 6 experimental conditions (n = 5). Composite buildups were constructed according to the combination of the main factors filling technique (BUL [single 4-mm thick layer] and INC [two 2-mm thick layers]) and composite resin (Filtek Bulk Fill Flow [FIL], 3M ESPE, Tetric N-Ceram Bulk Fill [TET], Ivoclar Vivadent and SureFil SDR Flow [SDR], Dentsply Caulk) with their respective conventional adhesive systems. Teeth were sectioned to obtain bonded sticks (0.8 mm2) to be tested in tension (0.5 mm/min) for μTBS. For NL, two bonded sticks from each tooth were placed in 50% silver nitrate and polished with SiC paper and then analyzed using scanning electron microscopy. For DC, three specimens per tooth were analyzed in micro-Raman spectroscopy. The mean μTBS (MPa) NL (%) and DC (%) data were submitted to a two-way ANOVA and Tukey´s test (α = 0.05). In experiment 2, a total of 236 posterior dental cavities with a cavity depth of at least 3 mm (72 participants) were randomly divided in four groups (n=59). Restorations were bonded either with the etch-and-rinse Tetric N-Bond (Ivoclar Vivadent) or with the self-etch Tetric N-Bond SE (Ivoclar Vivadent). The composite resin TET (Ivoclar-Vivadent) was placed either INC or in BUL techniques. Two experienced and calibrated examiners performed the evaluation of the restorations using the FDI criteria after one week of clinical service. Spontaneous postoperative sensitivity was assessed using a 0-4 and a 0-100 numerical rating scale (NRS), and a 0-10 visual analog scale (VAS) up to 48 h after the restorative procedure and one-week later. Results: In experiment 1, higher μTBS values (mean ± SD) were observed for FIL (57.5 ± 3.5) in the BUL technique when compared to other groups inserted in BUL (TET 52.6 ± 7.8; SDR 54.9 ± 4.3) or INC filling (FIL 51.8 ± 4.1; TET 47.9 ± 4.5; SDR 49.7 ± 3.8) - p > 0.05. No statistically significant difference was observed among the materials tested (p > 0.05). No significant difference was 9 detected in NL (FIL [7.6 ± 1.9 INC and 10.3 ± 2.3 BUL]; TET [10.9 ± 3.3 INC and 12.8 ± 4.0 BUL]) and DC (FIL [87.9 ± 7.0 INC and 85.6 ± 8.4 BUL]; TET [92.2 ± 3.4 INC and 83.3 ± 5.4 BUL]) between filling technique (p > 0.05). Higher NL values (13.0 ± 3.6 INC and 14.8 ± 2.5 BUL [p = 0.001]) and lower DC (49.7 ± 8.3 INC and 48.6 ± 4.0 BUL [p = 0.003]) were found when SDR was used. In experiment 2, neither the restorative technique nor the adhesive strategy affected the risk (p > 0.49) and intensity of spontaneous postoperative sensitivity (p > 0.38). The overall risk of postoperative sensitivity observed was 20.3% (95% CI 15.7 to 25.9) and occurred practically within the 48 h after the restorative procedure. Conclusions: The filling technique did not affect the μTBS, NL and DC of the bulk fill materials tested in this study. Clinically, the use of single increment of this new bulk-fill material, even in deep restorations, did not generate more postoperative sensitivity when compared to the incremental filling technique.