Adhesive Luting of All-ceramic Restorations - The Impact of Cementation Variables and Short-term Water Storage on the Strength of a Feldspathic Dental Ceramic

Purpose: To investigate the impact of resin cement luting variables and short-term water storage on the strength of an adhesively luted all-ceramic restorative material. An understanding of the strengthening mechanisms will result in optimisation of operative techniques and materials selection criteria. Materials and Methods: The "fit" surfaces of 480 disk-shaped feldspathic porcelain specimens were alumina air abraded to introduce a clinically relevant surface texture and consistent surface defect population. Thirty specimens randomly allocated to each of 16 groups were coated with silane, unfilled resin or filled resin cement, or a combination. Eight groups were stored either dry or wet for 24 h prior to bi-axial flexure testing (ball-on-ring). Statistical analysis of the flexure strength data involved a three-factor general linear model (p 0.05) prior to a Weibull analysis. Results: Resin coating the porcelain surface resulted in a significant increase in the characteristic stress (σo), and strengthening was dependent on coating type (p 0.001). Silane priming resulted in additional strengthening when preceding filled resin cement coating. Water immersion for 24 h resulted in a strength degradation of both the uncoated control and coated specimens, whereby the magnitude of strength degradation was dependent on coating type (p 0.001). Conclusion: Resin luting of dental ceramics results in significant strengthening likely to impact on clinical performance. The strengthening is dependent on the creation of a resin-ceramic hybrid layer sensitive to cementation variables and clinical placement technique. Short-term water immersion results in a significant degradation of strengthening sensitive to the characteristics of the resin-ceramic hybrid layer. Keywords: silane priming, resin luting, water storage, feldspathic porcelain