Objectives: To observe porcelain veneer behavior of zirconia and metal-ceramic full coverage crowns when subjected\udto compression testing, comparing zirconia cores to metal cores.\udStudy Design: The porcelain fracture surfaces of 120 full coverage crowns (60 with a metal core and 60 with a\udzirconia core) subjected to static load (compression) testing were analyzed. Image analysis was performed using\udmacroscopic processing with 8x and 12x enlargement. Five samples from each group were prepared and underwent\udscanning electron microscope (SEM) analysis in order to make a fractographic study of fracture propagation in the\udcontact area and composition analysis in the most significant areas of the specimen.\udResults: Statistically significant differences in fracture type (cohesive or adhesive) were found between the metalceramic\udand zirconia groups: the incidence of adhesive fracture was seen to be greater in metal-ceramic groups\ud(92%) and cohesive fracture was more frequent in zirconium oxide groups (72%). The fracture propagation pattern\udwas on the periphery of the contact area in the full coverage crown restorations selected for fractographic study.\udConclusions: The greater frequency of cohesive fracture in restorations with zirconia cores indicates that their\udbehavior is inadequate compared to metal-ceramic restorations and that further research is needed to improve their\udclinical performance.
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