Effect of luting agent on the load to failure and accelerated-fatigue resistance of lithium disilicate laminate veneers

Abstract

OBJECTIVE The aim of this study was to investigate the influence of the luting agent on the application of laminate veneers (LVs) in an accelerated fatigue and load-to-failure test after thermo-cyclic aging. METHODS Sound maxillary central incisors (N=40) were randomly divided into four groups to receive LVs (Li2Si2O5) that were adhesively bonded: Group CEMF: Adhesive cement (Variolink Esthetic LC), fatigue test; Group CEMLF: Adhesive cement, load-to-failure test; Group COMF: Resin composite (Enamel HFO), fatigue test; Group COMLF: Resin composite, load-to-failure test. The specimens were thermo-mechanically aged (1.2×106 cycles at 1.7Hz/50N, 8000 cycles 5-55°C) and then subjected to either accelerated fatigue (5Hz, 25N increasing after each 500 cycles) or load to failure (1mm/min). Failure types were classified and data analyzed using chi-square, Kaplan Meier survival, Log Rank (Mantel-Cox) and independent-samples t-test. RESULTS After thermo-mechanical aging, fracture resistance (p<0.000) was higher in the composite groups. Kaplan Meier survival rates showed significant difference (p<0.001) between the composite (mean load: 1165N; mean cycles: 22.595) and the cement groups (mean load: 762.5N; mean cycles: 14.569). The same differences were observed in the load to failure test (cement M=629.4N, SD±212.82 and composite M=927.59N, SD±261.06); t (18)=-2.80, p=0.01. Failure types were observed as fractures and chipping in group CEMF, all other groups were predominantly adhesive failures between the luting agent and the laminate veneer. SIGNIFICANCE The delivery of laminate veneers using a direct restorative composite rather than a resin cement resulted in significantly less chipping and fractures, higher fracture strength in both accelerated fatigue and load-to-failure.