Randomized Clinical Trial of Implant-Supported Ceramic-Ceramic Posterior FDPs

Objectives: To determine the survival of implant supported ceramic-ceramic posterior prostheses as a function of material type, occlusal veneer thickness, radius of curvature of gingival embrasure and connector height.
Methods: A total of 96 subjects were randomly assigned to receive an implant-supported three-unit posterior FDP, made of either a metal-ceramic (Au-Pd-Ag alloy and InLine POM, Ivoclar, Vivadent) or a ceramic-ceramic (ZirCAD and ZirPress, Ivoclar, Vivadent). Twenty five of these 96 subjects received two FDPs. The two groups were further randomized into three different groups with occlusal veneer thicknesses of 0.5, 1.0, or 1.5 mm; connector heights of 3, 4, or 5 mm; and a diameter of curvature at the gingival embrasure of 0.5, 1.0, or 1.5 mm. Patients were enrolled after eligibility criteria were met and two endosseous implants (Osseospeed, Dentsply) were placed. Custom abutments (Atlantis, Dentsply) were placed to receive either a computer-designed, machine-milled zirconia FDP or a metal-ceramic FDP with two crown retainers and a pontic. Patients were recalled at 6 months, and yearly for 5 years.
Results: A total of 129 FDPs in 96 patients (42 males, 54 females) were placed with 65 ceramic-ceramic and 64 metal-ceramic prostheses. 27 FDPs exhibited chipping fractures of the veneer during the five-year observation period, representing 20% of the population. The distribution of failures according to design parameter is shown in Table 1.

Conclusions: The R statistical software (Vienna, Austria; V.3.0.2) package was used to calculate descriptive statistics and perform univariate tests between the fractured and nonfractured groups. To account for repeated observations for these subjects, generalized estimating equations for logistic regression were used to conduct these tests. The subject was considered a repeated factor and an exchangeable working correlation was assumed. There was no statistically significant effect of type of material, veneer thickness, diameter of curvature of gingival embrasure and connector height on the occurrence of fracture.