Efeito da morfologia do preparo cavitário e técnica restauradora indireta em molares. Avaliação laboratorial e revisão sistemática da literatura.

Abstract

Ceramics are used for indirect restorations such as inlays, onlays and full crowns, due to their advantages. There are some cavity preparation designs for each of them, and we should prioritize preservation of tooth structure, better biomechanical behavior, simplicity of technique, and, in addition, we must consider the tooh structure remaining for vital tooth and for endodontically treated tooth. This doctoral thesis has three specific objectives: 1) To evaluate the effect cavity preparation design and ceramic type on biomechanical behavior of indirect restorations in vital molars. Forty molars were divided into four groups (n=12), submitted to fracture resistance, failure mode, stress distribution and finite element analysis. 2) To analyze the internal and marginal integrity of the resin cement and the adaptation of indirect restoration in vital molars for different cavity designs and different ceramics types. Twenty molars divided into four groups (n=5) were scanned using the high-resolution 3D micro-CT for calculate the porosity and volume of the cement. 3) To investigate “in vivo” and “in vitro” the endocrown technique cavity design for endodontically treated teeth with extensive loss of tooth structure. In the systematic review, sixty studies had their data extracted and evaluated. After data analysis from these studies, the lithium disilicate ceramic onlay exhibited significantly higher fracture resistance than leucite ceramic, and the presences of boxes on disilicate ceramic restorations reduced significantly the fracture resistance. The failure mode distributions showed that the lithium disilicate ceramic resulted in more severe failure mode irrespective of cavity preparation. The cavity design with boxes resulted in a coronal deformation similar to cavity designs without boxes. The marginal adaptation on the non-boxes preparation design decresed the volume and porosity in resin cement compared with boxes. In the systematic review, the “in vitro” studies showed that the endocrown restorations presented a more conservative preparation design and presents biomechanical advantages with a same performance in a classical technique design restoration with fiberglass post, composite resin core and full ceramic crown. Despite the clinical studies presents satisfactory results of teeth restored with endocrown, they are insufficient for clinical confirmation of this technique. Within the limitations of this study, the ceramics reinforced by leucite had less coronal deformation and failure mode. The homogeneous thickness of ceramic restorations influenced in less porosity and volume in the resin cement. It was observed that more conservative preparations designs, such as onlay without proximal and occlusal boxes and the endocrown preparations designs, requires less chair time because there are fewer procedures, and besides being easier and faster techniques, they also present greater resistance to fracture. However, longitudinal clinical studies are needed to prove these indirect restoration techniques.