Fracture Resistance of Fixed Dental Prostheses

Methods: A typodont model (Frasaco) with a missing mandibular right first molar was used. A full crown preparation with chamfer outline was made on the second premolar and second molar. Silicon moulds were made of the typodont model, the premolar, and the first molar. The model was reproduced in PMMA and the teeth in composite to mimic the stiffness's of the teeth and the bone. The periodontium was mimicked by an impression material. Morphologically standardized FDPs of Protemp 3 Garant (n=10), Trim II (n=10), porcelain/gold (n=7), porcelain/Lava Zirconia (n=7), Filtek Z250 (n=10), and Filtek Z250/Everstick fibers (n=10) were luted (RelyX UniCem or PreVISION CEM) on the models. The fracture resistance, by loading on the first molar, was determined in a universal testing machine.

Results: The fracture resistance showed an increasing order: Trim II (375N), porcelain/gold (733N), Protemp 3 Garant (783N), porcelain/Lava Zirconia (868N), Filtek Z250 (959N), and Filtek Z250/StickTech fibers (1494N). Trim II was significantly weaker, while Filtek Z250/StickTech fibers was significantly stronger compared to porcelain/gold, Protemp 3 Garant, porcelain/Lava Zirconia (868N), and Filtek Z250. The modes of failure were; deformation (Trim II), delamination (porcelain/gold and Filtek Z250/StickTech), and catastrophic failure (porcelain/Lava Zirconia, Filtek Z250, and Protemp 3 Garant)

Conclusion: Within the limitations of this study, it was shown that FDPs made of different materials fail at different loads and in different ways. Furthermore, these data are valuable for computer models to rationalize the failure behavior.