Análise da deformação de cúspide por micro-CT e de trincas por transiluminação em restaurações de resina composta incremental e bulkfill em molares

Abstract

The purpose of this study was to measure cusp deformation using microcomputed tomography (micro-CT) and enamel crack propagation using transillumination of incremental or bulk-fill composite resin restorations in molars. Twenty human molars received Class II mesio-oclusal-distal cavity preparations and were restored with bulk-fill resin, X-tra fil (XTRA) or conventional composite, Filtek Z100 (Z100). The composite resins were tested for post-gel shrinkage using the strain gauge method. Enamel crack were detected using a standard transillumination method and classified. Cusp deformation was evaluated using the images obtained from a new micro-CT protocol and using strain-gauges method. Shr of Z100 was higher than XTRA. Cusp deformation of Z100 was higher than XTRA irrespective of measured methods. Lingual cusp had higher CD than buccal cusp irrespective of measured methods. Positive correlation (r = 0.78) was found between cusp deformation measured by micro-CT and straingauge methods. Hygroscopic expansion recovered significantly the cusp displacement irrespective of composite resin and cusp type. No tooth demonstrated visible crack before and after cavity preparation. Z100 had more occurrence and larger cracks than XTRA. The crack tended to be horizontal, locate at the base of the cavity, involving mainly the center and the distal region. After hygroscopic expansion, the enamel crack size increased around 17% for XTRA and 18% for Z100. The proposed methods using micro-CT proved to be effective for evaluating the cusp deformation and the enamel crack detection using transillumination and mighty to help a development of new materials and techniques used in clinical practice. Bulk fill composite resin tested had lower negative effects of polymerization shrinkage than conventional composite resin.