Aim: The aim of this in vitro study was to investigate the influence of heterogeneous abutment supports on the load-bearing capacity of zirconia posterior four-unit fixed dental prostheses.
Methods: A total of 18 specimens were fabricated and divided into 3 groups. Specimens in the first group were supported by teeth with simulated periodontal resilience, in the second group by the combination of a tooth with simulated periodontal resilience and an implant, whereas in the last group by implants only. The bridgeworks were loaded in a universal testing machine until fracture, and the load-bearing capacity was recorded. Statistical analysis was performed by one-way analysis of variance, with the level of significance set at 0.05.
Results: Implant-supported zirconia restorations exhibited the highest loads at fracture (2689.3 N), followed by combined restorations (2144.2 N) and tooth-retained prostheses (2009.4 N). Statistical analysis revealed a significant influence of abutment support on the load-bearing capacity (P = 0.014). Visual inspection of the tested specimens showed different fracture patterns in the 3 groups.
Conclusion: For all support scenarios, the recorded loads were much higher than maximum natural bite forces, so that all the tested prosthesis designs could be recommended for application in posterior areas. The long-term prognosis of such restorations should however be further evaluated within in vivo studies to recommend their use in the clinic.