Thermo-mechanical behavior of alternative material combinations for full-arch implant-supported hybrid prostheses with short cantilevers'

Objectives: To compare the fracture resistance (FR) of three combinations of materials for full-arch maxillary implant-supported hybrid prostheses (HPs) with short cantilevers (<= 10 mm). Methods: Maxillary HPs were fabricated and classified as follows (n = 5 each): Group-1 (CC-A, control): acrylicresin-veneered Co-Cr frameworks; Group-2 (CF-A): acrylic-resin-veneered carbon-fiber mesostructures; and Group-3 (CF-R): composite-resin-veneered carbon-fiber frames. Specimens were thermal-cycled (5,000 cycles; 5 degrees C-55 degrees C; dwell time: 30 s). Vertical loads were applied until failure, first at the 10-mm-long cantilever (LC), and, afterwards, at the anterior region (AR), using a universal testing machine (crosshead speed: 0.05 mm/s). The fracture pattern was assessed by stereomicroscope and SEM. The one-way ANOVA, the Bonferroni, and the independent samples t tests, were run (alpha= 0.05). Results: At LC, CF-A, and CC-A samples exhibited the highest FR values (p< 0.001), showing no differences to each other. At AR, CC-A specimens recorded the highest FR, followed by CF-A samples (p< 0.001). CF-R HPs displayed the lowest FR at both locations (p< 0.001). The only group with differences between the tested sites was the CC-A, the AR being more resistant (p< 0.001). Most CC-A and CF-A HPs failed cohesively. CF-R prostheses mainly failed adhesively. Conclusions: Maxillary HPs with short cantilevers (<= 10 mm) made of Co-Cr or carbon-fiber veneered with acrylic resin demonstrated an adequate mechanical resistance (> 900 N). Clinical significance: For maxillary HPs with cantilevers up to 10 mm, acrylic-veneered carbon- fiber mesostructures may be recommended, whereas coating carbon-fiber frames with composite resin seems not suitable.