Fracture Behavior of Minimally Invasive, Posterior, and Fixed Dental Prostheses Manufactured from Monolithic Zirconia.

Objectives: To compare ultimate fracture load (F ), load at first damage (F ), and fracture pattern for posterior fixed dental prostheses (FDPs) manufactured from translucent, yttria-stabilized zirconia polycrystal.

Methods: Premolar-size FDPs in 4 test groups (n = 16/group) were constructed as veneered complete crown-retained (group 1), monolithic complete crown-retained (group 2), monolithic partial veneer crown-retained (group 3), or monolithic resin-bonded (group 4) prostheses with minimum zirconia wall thickness (0.5 mm). Adhesively cemented to metal abutments, half of the prostheses were artificially aged by use of 10,000 thermocycles (6.5°C/60°C) and 1,200,000 chewing cycles (F = 108 N), before fracture loading. Statistics included two-way non-parametric ANOVA and Dunn-Bonferroni post-hoc tests (α = 0.05).

Results: None of the restorations failed during artificial aging. F was affected by test group (p < 0.001); F was also affected by the factor combination of test group and aging (p = 0.001 for test group; p = 0.049 for test group*aging). Mean F for all groups exceeded 1000 N; it was comparable for group 1 and group 2 and statistically significantly higher for group 2 and group 3 than for group 4 (p < 0.01). Fracture usually occurred through the retainer wall. F  = 200 N was determined for individual samples in group 1 (chipping) and group 3 (local debonding).

Conclusions: F of all the restorations was adequate for clinical use. Complications might, however, be expected at forces below 500 N for veneered prostheses (chipping) as well as for monolithic partial veneer crown-retained prostheses (local debonding).

Clinical Significance: With regard to fracture behavior, all-ceramic complete crown-retained fixed dental prostheses (FDP) manufactured from monolithic zirconia, with a retainer wall thickness of 0.5 mm, might be suitable for use as a conservative alternative to their veneered counterparts in the rehabilitation of posterior tooth loss. Monolithic zirconia resin-bonded FDP might, moreover, be a viable alternative to resin-bonded FDPs with metal adhesive retainers in posterior arches, with improved esthetics and biocompatibility. The performance of both should, however, be verified in clinical trials. (J Esthet Restor Dent 28:367-381, 2016).