Avaliação biomecânica do efeito da férula em restaurações do tipo endocrown

Abstract

The objective of the present study was to evaluate fracture resistance and deformation of the dental structure after production of endocrown restorations with or without the presence of ferule, varying the ceramic restorative materials (lithium disilicate and hybrid feldspathic ceramic). Fifty healthy human molar teeth were selected and randomly distributed into 5 groups (n = 10): (1) Control - sound teeth; (2) Cavity preparation with ferule, restored with lithium disilicate; (3) Cavity preparation without ferule, restored with lithium disilicate; (4) Cavity preparation with ferule, restored with hybrid feldspathic; and (5) Cavity preparation without ferule, restored with hybrid feldspathic. The ferule groups were performed with 1mm height and 1.5mm thickness and finished at 1mm from the cementoenamel junction. Samples without ferule had the coronary portion sectioned 1mm above the cementoenamel junction and the circumferential wall thickness was maintained at 1.5mm. The restorations were produced using the CAD/CAM method and cemented using a self-adhesive resin cement. The samples were subjected to aging by thermal and mechanical cycling. The axial loading to fracture test was performed with a deflectometer positioned near the cervical region of the samples. The data obtained were submitted to statistical analysis using Two-way ANOVA, One-way ANOVA, Dunnett and Kruskal-Wallis tests (α = 5%). For fracture resistance of the tooth/restoration complex, statistical significance was verified for the material factor (p<0.001) and for the ferule x material interaction (p=0.008). The hybrid feldspathic ceramic group without ferule presented the lowest values of fracture resistance. There was no statistical difference between groups for deformation of the dental structure when loading samples with 100N (p=0.179). The fracture patterns were similar for molars restored with endocrown, regardless of the presence of ferule or the type of restorative material (p=0.182), but different from the sound tooth (p=0.001). It was concluded that ferule should be performed in preparations where the strength of the restorative material is directly related to its ability to resist to deformation and limit of rupture.