Purpose: The purpose of this exploratory in vitro study was to compare and evaluate the load-bearing capacity (LBC) of ceramic-veneered zirconia and composite-veneered polyetheretherketone (PEEK) three-unit fixed dental prostheses (FDPs) with and without thermocycling (TC).
Materials and methods: The study included 40 samples of three-unit FDPs replacing mandibular first molars. The four groups included were: ceZIR (feldspathic ceramic-layered zirconia), ceZIR TC (feldspathic ceramic-layered thermocycled zirconia), cPEEK (composite-layered PEEK), and cPEEK TC (composite-layered thermocycled PEEK) (n = 10 per group). All frameworks were CAD/CAM milled. Ten PEEK and 10 zirconia samples were subjected to TC (6,000 cycles). All 40 FDP specimens were loaded by applying static load, using a universal testing machine. The maximum load required to fracture the specimens denoted the LBC. The comparison of LBC between the four groups was done by using two-way ANOVA with Tukey's post-hoc analysis (α = .05).
Results: There was no statistically significant difference between LBC of cPEEK and ceZIR (P > .001) without thermal aging. LBC values decreased considerably for thermally aged specimens. Statistically significant differences were observed between LBC of cPEEK TC and ceZIR TC (P < .001), cPEEK TC and cPEEK (P < .001), and ceZIR TC and ceZIR (P = .001). On fracture analysis, cPEEK showed delamination failures whereas ceZIR displayed catastrophic connector fractures.
Conclusion: This comparative evaluation offers preliminary data highlighting substantial depreciation in the LBC of layered PEEK under simulated intraoral conditions, thus raising a question regarding the clinical longevity of layered PEEK multi-unit restorations. In contrast, feldspathic-layered zirconia can be suitable for use in posterior FDPs.