Dynamic fatigue and fracture resistance of non-retentive all-ceramic full-coverage molar restorations. Influence of ceramic material and preparation design

ObjectivesThe purpose of the study was to evaluate the influence of preparation design, and ceramic material, masticatory fatigue and fracture resistance of non-retentive all-ceramic full-coverage restorations luted on human mandibular molars.MethodsFull-coverage occlusal restorations were laboratory fabricated from leucite reinforced glass-ceramic (IPS Empress Esthetic) or lithium disilicate glass-ceramic (IPS e.max Press). For each ceramic material four groups with eight specimens each were randomly assigned. Groups had either a non-retentive, occlusal preparation with chamfer finishing line or straight-beveled finishing line and the preparation was either completely within enamel or within dentin with a finishing line in enamel. Restorations were adhesively luted to the teeth using composite resin. After storage in water for 1 week specimens were cyclic loaded 600,000 times with a weight of 10 kg and additionally, thermocycled 3500 times (5/55 °C) in a masticatory simulator. Surviving specimens were loaded until, fracture in a universal testing machine. Statistical analysis was done using three-way ANOVA.ResultsAll specimens survived the masticatory fatigue. Mean fracture resistance ranged from 2895 to 4173 N. Influence of ceramic material on fracture resistance was significant (p = 0.0001). Lithium disilicate glass-ceramic restorations had higher fracture resistances than leucite reinforced glass-ceramic restorations. Different preparation designs showed no significant influence on fracture resistance (p = 0.0969). The design of the finishing line did not influence the fracture resistance (p = 0.9461).SignificanceThe fracture resistance of adhesively luted non-retentive full-coverage molar restorations, made of lithium disilicate or leucite reinforced glass-ceramic is promising and seems to permit clinical application.