Mechanical Properties of an Experimental Temporary Crown and Bridge Material

Objectives: Making of fixed dental prostheses (FDP) usually requires temporary FDPs. In cases of adverse effects to commonly used BisGMA-based temporary materials resins with an alternative chemistry may be useful. This study investigated mechanical properties of an experimental BisGMA-free temporary materials based on multifunctional methacrylic ester (VOCO, Germany). Two BisGMA-based materials (Protemp 4, 3M ESPE AG, Germany; Luxatemp, DMG, Germany) served as control.
Methods: Methods and Material: According to a standardized protocol from each material 30 temporary 4-unit FDPs (44-47) were made on identical PMMA casts, subsequently cemented on their casts (Provicol, VOCO, Germany) and divided into three groups with 10 specimens each. Group 1 underwent 48h of water storage (WS) only. Group 2 underwent thermo-cycling (TC) (5°C, 55°C, 27s each, 1.700 cycles), group 3 underwent cyclic mechanical loading (CML) under wet conditions (vertical sinusoidal loading 0 to 50N, 50.000 cycles) simulating 28 days of service. Then all specimens were loaded until failure by 3-point bending test (TIRA-Test, crosshead speed 1mm/min). Statistical analysis used Kruskal-Wallis and post-hoc analysis.
Results: After WS failure loads differed significantly between experimental material and Luxatemp (group 1, p<0.05). After TC both controls performed significantly better (group 2, p<0.05). However, no significant differences were found after CML (group 3, p>0.3).
Conclusions: Conclusion: Overall failure loads of the experimental material were comparable to both controls and should be clinical sufficient. Failure loads were significantly influenced by the type of artificial aging. Increase in failure loads of the controls after TC may be attributed to differences in water absorption or stress release after polymerization.