Fatigue resistance of ultrathin CAD/CAM ceramic and nanoceramic composite occlusal veneers

Objective. The fracture resistance of different ultrathin occlusal computer-aided design/computer-aided manufacturing (CAD/CAM) veneers was investigated under cyclic mechanical loading to restore combined enamel-dentin defects. Methods. Eighty-four molars were reduced occlusally until extensive dentin exposure occurred with a remaining enamel ring. Twenty-four molars were ground flat for examination of highly standardized specimens, of which 8 were treated with uniformly flat 0.3 mm IPS Empress CAD and 0.3 and 0.5 mm IPS e.max CAD restorations. Sixty-four molars were anatomically prepared until dentin exposure and were restored using occlusal veneers with fissure/cusp thicknesses of 0.3/0.5 mm from 3 different dental CAD/CAM materials: IPS Empress CAD, IPS e.max CAD and Lava Ultimate CAD/CAM. Teeth were etched with 37% phosphoric acid, and occlusal veneers were bonded using an adhesive luting system (Syntac Primer, Adhesive, Heliobond and Variolink II). Specimens were placed under cyclic mechanical loading in a chewing simulator (1 million cycles at SON) and were examined for cracks after each cyclic loading sequence. The anatomical 0.3/0.5 mm IPS e.max CAD specimens experienced an additional 1 million cycles at 100 N. Kaplan-Meier survival curves and log-rank tests were used for data analysis. Results. All highly standardized and 0.3/0.5 mm IPS e.max CAD specimens tolerated cyclic loading. One anatomical Lava Ultimate CAD/CAM and 10 IPS Empress CAD specimens showed cracks. Significance. Ultrathin occlusal veneers of lithium disilicate ceramic and nanoceramic composite showed remarkably high fracture strength under cyclic mechanical loading. These veneers might be a tooth substance preserving option for restoring combined dentin-enamel defects. (C) 2019 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.