Influência da profundidade de preparo intracâmara no desempenho biomecânico de dentes com restaurações endocrown

Abstract

The aim of this study was to evaluate the influence of pulp chamber pulp preparation depth on in vitro biomechanical performance of endocrowns restorations on molars made of different ceramic materials. Fifty healthy molars with approximate dimensions were divided into 5 groups (n = 10). The teeth were sectioned 2 mm above the cementoenamel junction and defined endodontically, except for the control group (CG). Then they were randomly distributed in 4 groups (n = 10) according to the endocrown ceramic material and with a preparation depth, respectively: EX2- lithium-disilicate (IPS e.max CAD)/ 2 mm; EX4- (IPS e.max CAD)/ 4 mm; EN2- polymer infiltrated ceramic (VITA Enamic)/ 2 mm; EN4- (VITA Enamic)/ 4 mm. For preparation of endocrowns restorations, all preparations were designed and milled by the CAD/CAM method with the CEREC AC system. Then, the endocrowns were conditioned with 5% hydrofluoric acid, the silane was applied and cemented with self-adhesive resin cement (Rely-XTM U200). Posteriorly, the samples were submitted to thermal cycling (5.000 cycles), mechanical fatigue (600.000 cycles with 125 N axial load at 4 Hz), fracture resistance test (1.8Kg load, 1mm/min) and analysis of the failure modes. ANOVA two-way and Tukey’s test were used to compare the different materials investigated and the different depths of preparation of the pulp chamber. The comparation of groups with the control group was evaluated by Dunnett's test (α = 0.05). The fracture resistance results presented showed a significant interaction between material factors and depth (p = 0.020). Comparing the pulp chamber floors for each material, there was a statistically significant difference for the lithium-disilicate group, so that EX4 presented higher fracture resistance (2060.6 ± 503.0 N) compared to EX2 (1433.5 ± 260.0 N) (p = 0.040). No significant difference was observed between EN2 (1147.9 ± 337.5 N) and EN4 (1048.2 ± 208.8 N) groups (p = 0.07). EX4 presented higher fracture resistance compared to group EN4 (p = 0.001), but EX2 and EN2 did not show significant difference between fracture resistance of materials (p = 0.08). When comparing ceramic materials at different pulp chamber depths with the control group (1663.8 ± 552.0 N), only the EN4 group presented significant difference (p = 0.040), presenting lower fracture resistance (1048.2 ± 208.8 N). Irreparable fractures were mostly observed in both the lithium-disilicate group and the polymer infiltrated ceramic group. The endocrowns made with lithium-disilicate ceramics were influenced by the pulp chamber depth, presenting greater fracture resistance at a depth of 4 mm. There was no difference in fracture strength at different extension depths for enamic endocrowns.