FRACTURE RESISTANCE AND MARGINAL FIT OF CERAMIC REINFORCED RESIN CROWNS FABRICATED BY ADDITIVE MANUFACTURING (IN VITRO STUDY)

Abstract

Background: The fit and strength of the additively manufactured restorations have not been thoroughly investigated. Objectives: this study was conducted to evaluate the marginal fit and fracture resistance of hybrid ceramic crowns fabricated by additive and subtractive manufacturing. Material and Methods: A Maxillary first premolar typodont tooth was prepared to receive a hybrid ceramic full crown. The prepared tooth was duplicated into 18 epoxy resin dies that were divided into 3 groups (n=6): (VE) subtractive manufacturing of Polymer network infiltrated ceramic (Vita enamic) crowns, the other 2 groups were additively manufactured using ceramic-reinforced resin Flexcera smile ultra+ (Flex) and Varseosmile crown plus (VS) respectively. Intraoral scanner was used to scan all epoxy resin dies. A dental CAD program was used to make a standardized crowns design. VE was fabricated using a dental milling machine, while Flex and VS were fabricated using a 3D resin printer. Marginal gap was measured before cementation and after cementation and thermo-mechanical aging. All specimens were subjected to load till failure using a universal testing machine, followed by failure mode analysis. Statistical analysis was performed using Kruskal Wallis and Wilcoxon signed ranks tests.Results: VITA Enamic and Varseosmile had statistically significant higher fracture resistance compared to Flexcera. VITA Enamic had statistically significant largest marginal gap than both Flexcera and Varseosmile. Thermomechanical aging significantly increased the marginal gap of all groups.Conclusions: VITA Enamic and Varseosmile demonstrated significantly better fracture resistance compared to Flexcera. Printed crowns showed less marginal gap than milled crowns.