Survival of three types of veneer restorations in a clinical trial: a 2.5-year interim evaluation

Objectives: In this clinical trial, 180 veneer restorations (VRs) were evaluated. The purpose of the study was to collect survival data and to find possible relations between survival and (1) `type of VRʹ, (2) `preparation designʹ, (3) `operatorʹ and (4) the patient-related variables `tooth-typeʹ and `vitality of the toothʹ. Methods: The restorations were provided by seven dentists in 112 patients on central and lateral maxillary incisors. Experimental variables were: `type of VRʹ (either direct resin composite (DC), indirect resin composite (IC) or porcelain (P)), `preparation designʹ (with and without incisal overlap) and `operatorʹ. Failures were recorded at two levels: absolute failure (need for new restoration) and relative failure (need for repair). Survival was defined at three levels: (1) s!urvival of original restoration (Sr, endpoints: `absoluteʹ failures), (2) functional survival (Sf, endpoints: `relativeʹ failures) and (3) overall survival (So, endpoints: both `absolute-ʹ and `relative failuresʹ). Results: The variable `type of VRʹ showed significant influence on Sf and So but not on Sr. Sf and So rates of P, IC and DC were, respectively: Sf-P, 94%; So-P, 94%; Sf-IC, 94%; So-IC, 90%; Sf-DC, 80%; So-DC, 74%. VRs on vital teeth showed a significantly better survival than VRs on non-vital teeth at all survival levels. Conclusions: Preparation of the incisal edge for incisal coverage is considered to be unnecessary to assure or improve the strength of VRs. c non-vital teeth showed higher risk to fail than veneers placed on vital teeth. Porcelain veneers showed the best overall survival.