Controlled, prospective, randomized, clinical evaluation of partial ceramic crowns inserted with RelyX Unicem with or without selective enamel etching. Results after 2 years.

Among the materials used for luting indirect restorations, growing interest has been directed towards the use of self-adhesive resin cements. The aim of this prospective randomized controlled clinical trial was to evaluate the clinical performance of the self-adhesive resin cement RelyX Unicem (RXU) for luting partial ceramic crowns (PCCs). In addition, the influence of selective enamel etching prior to luting (RXU+E) was assessed. Two-year results are reported. Thirty-four patients (68 PCCs) had originally received the intended treatment at baseline (BL). Twenty-nine patients (14 male, 15 female) with a total of 58 PCCs participated in the 2-year recall. In each patient, one PCC had been placed with RXU, one PCC with RXU+E. Restorations were evaluated at BL and 24 months after placement using modified United States Public Health Service criteria for postoperative hypersensitivity, anatomic form, marginal adaptation, marginal discoloration, surface texture and recurrent caries. Additionally, the "percentage failure" within the 2-year recall period for all restorations (n = 68) was calculated according to ADA Program Guidelines. Target value for acceptability of each procedure was <5% failure within 24 m. For statistical analysis of the data, the chi-square test was applied (α = 0.05). The median patient age was 41 years (24-59 years). Median PBI was 8% (5-10%). Twenty-two RXU PCCs were placed in molars, seven in premolars. Twenty-one RXU+E PCCs were placed in molars, eight in premolars. Statistically significant changes were observed for marginal adaptation (MA) and marginal discoloration (MD) between BL and 2 years but not between the two groups (RXU, RXU+E). Percentage of alfa values at BL for MA (RXU, 97% and RXU+E, 100%) and for MD (RXU, 97% and RXU+E, 97%) decreased to RXU, 14% and RXU+E, 28% for MA and to RXU, 50% and RXU+E, 59% for MD after 24 months. Within the observation period, three failures were recorded with RXU (5.1% failure), one failure was recorded for RXU+E (1.7% failure), but a significant influence of selective enamel etching on failure could not be verified. Although the results of the present study reveal a slight tendency for more favourable results if selective enamel etching is applied prior to insertion of ceramic PCCs with a self-adhesive luting material, longer-term evaluation is needed to confirm this. Additional selective enamel etching with a self-adhesive luting material does not considerably improve clinical performance of the restorations within the observation period reported, neither does it impose a hazard with respect to postoperative hypersensitivity.