INFLUENCE OF THE PREPARATION DESIGN AND AGING ON THE VERTICAL MARGINAL GAP OF OCCLUSAL VENEERS CONSTRUCTED OF DIFFERENT CERAMIC MATERIALS

Abstract

Aim: The current study aimed to investigate the marginal adaptation of two different designs of occlusal veneers manufactured from two different ceramic materials before and after aging. Material and Methods: Twenty freshly extracted mandibular second molars were used in this study. The teeth were randomly divided into 2 groups according to the occlusal veneer material (n =10 each). The first group in which the teeth were restored with occlusal veneers constructed of reinforced lithium silicate (ZLS), (Celtra Duo, Dentsply Sirona, Germany), while the second group, the occlusal veneer material was the polymer-infiltrated hybrid ceramic (Vita Enamic, Vita Zahnfabrik, Germany). Each group was further subdivided into 2 subgroups (n =5 each) according to the preparation design. In the first subgroup, the reduction of teeth involved conventional oc-clusal reduction (planner preparation). In the second subgroup, the reduction of teeth involved the occlusal surface plus 1 mm axial reduction with rounded shoulder finish line. The occlusal veneers were designed and milled using CAD/CAD technology. The vertical marginal gap was measured using stereomicroscope before and after the cemented teeth-veneer assemblies were imbedded in food/oral simulating liquids, and thermocycled. Two samples of the constructed occlusal veneers of the two studied materials were examined before and after ageing by FT-IR spectroscopy technique. Results of marginal gap were collected ,tabulated and statistically analyzed using independent t-test, and 3way Anova for the interaction between different variables results were considered significant at p≤0.05. Results: the results showed that the marginal gap of the two preparation designs of the two materials were statistically non significant before ageing P≤ 0.05.while after ageing, the subgroups of Celtra recorded, 90.45±13.0 and88.7±11.60µm, for conventional and, rounded shoulder designs respectively, with no significant difference between the two designs, while the subgroups of Vita Enamic recorded 113±7.01µm and 105.2±8.01µm for conventional and, rounded shoulder designs respectively, with high significant difference p≤0.003**. The Anova test revealed that the interaction between the materials, preparation designs and the ageing procedures, recorded very significant influence on the marginal gap discrepancy. Conclusions: The choice of certain preparation design should be associated with meticulous knowledge of the material of the occlusal veneers properties .Both materials could be used in oc-clusal veneers restorations .Celtra Duo had a marginal adaptation that survived with better values, qualitatively and quantitatively , even after the protocol of ageing applied in this study. (1262) Manal R. Abo-Eittah and Mohammed M. Shalaby E.D.