Fracture resistance of ultrathin occlusal veneer fabricated by different CAD/CAM materials

Abstract

Purpose The purpose of this in vitro study was to evaluate the fracture resistance of ultrathin occlusal veneer fabricated by different CAD/CAM materials. Methods The occlusal surface of 40 extracted lower premolars was prepared in the enamel layer and restored with occlusal veneers with fissures/cusp thickness of 0.5/1 ml made from two different dental CAD/CAM materials. Groups of the study included the following. Group I: lithium disilicate glass-ceramic n = 20; the group was further divided into two subgroups according to the thickness of each of them. Subgroup A: (n = 10) 0.5 mm and subgroup B: (n = 10) 1 mm. Group II: Cerasmart n = 20 is further divided into two subgroups according to the thickness of each of them. Subgroup A: (n = 10) 0.5mm, subgroup B: (n = 10) 1 mm. Occlusal veneers were etched with ceramic etch (Ips ceramic etching gel/ATZGEL-IVOCLAR AG) and then bonded using an adhesive luting system (G-MULTI PRIMER and G-CEMTM Veneer) light cure adhesive resin cement (G-CEHTM veneer). The prepared teeth were etched using phosphoric gel and bonded using Bisco All bond universal. All specimens were subjected to load till fracture; these loads were recorded and statistically analyzed using the one-way ANOVA. The mode of failure of the specimen was classified; the correlation between fracture strength and mode of failure was analyzed. Results In this study, fracture strengths (mean ± standard deviation) of cerasmart recorded were 0.5 mm (887.71 ± 284.79N), 1 mm (953.73 ± 214.06N), and for lithium disilicate 0.5 mm (455.16 ± 134.96N), 1 mm (768.59 ± 154.08N). Cerasmart had significantly higher fracture strength than lithium disilicate in 0.5 mm thickness, and significantly different fracture strength in 1 mm thickness. Most specimens (31 from 40) had been fractured in the restoration without involving the tooth structure. Conclusion The Cerasmart material could be considered a valid alternative to IPS e.max material.