Effect of thermal shock on mechanical properties of injection-molded thermoplastic denture base resins

Abstract

Objective. This study investigated the effect of thermal shock on the mechanical properties of injection-molded thermoplastic denture base resins. Materials and methods. Four thermoplastic resins (two polyamides, one polyethylene terephthalate, one polycarbonate) and, as a control, a conventional heat-polymerized polymethyl methacrylate (PMMA), were tested. Specimens of each denture base material were fabricated according to ISO 1567 and were either thermocycled or not thermocycled (n = 10). The flexural strength at the proportional limit (FS-PL), the elastic modulus and the Charpy impact strength of the denture base materials were estimated. Results. Thermocycling significantly decreased the FS-PL of one of the polyamides and the PMMA and it significantly increased the FS-PL of one of the polyamides. In addition, thermocycling significantly decreased the elastic modulus of one of the polyamides and significantly increased the elastic moduli of one of the polyamides, the polyethylene terephthalate, polycarbonate and PMMA. Thermocycling significantly decreased the impact strength of one of the polyamides and the polycarbonate. Conclusions. The mechanical properties of injection-molded thermoplastic denture base resins changed after themocycling.

Key Words::

• thermal shock
• mechanical properties
• thermoplastic denture base resin
• thermocycling

Acknowledgement

The authors would like to thank Aishi Dental Laboratory Co., Ltd., for supplying some of the specimens used in this project.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.