Effects of adhesive fixed prosthesis retainer design on resultant resin luting agent thickness

Statement of problem. Resin cement thickness may influence the success or otherwise of adhesive fixed prostheses and needs to be quantified for future stress analyses. Purpose. This study evaluated the effect of different complexities of retainer preparation design on resultant resin lute thickness. Material and methods. Five retainer designs were evaluated for resin luting thickness (Panavia Ex) after cementation to appropriately selected natural teeth as follows: (1) flat plate retainer; mandibular canine; (2) occlusal rests, mandibular premolar; (3) occlusal rests, proximal grooves, mandibular premolar; (4) modified three-quarter crown, mandibular premolar; and (5) occlusal strut, maxillary premolar. Five samples of each design were prepared in vitro. A mesiodistal and a buccolingual section were obtained from each sample with a diamond saw. Measurements were carried out on the fluorescent cement lute with a confocal microscope. Mean resin thickness and cervical resin thickness were analyzed with analysis of variance and Tukey tests. Results. Resin thickness (mu m) for each of the retainer designs were as follows (mean +/- SD): design 1, 58 +/- 40; design 2, 67 +/- 42; design 3, 80 +/- 28; design 4, 87 +/- 15; and design 5, 85 +/- 29. There were no significant differences among the designs (mean global value 75.4). The three-quarter crown (design 4) had a significantly wider cervical resin thickness (P less than or equal to .01) than designs 1, 2, and 3.