Handling Properties and Exothermicity of Chemically Initiated Silorane Biomaterial

Objective: Newly developed silorane dental composites are biocompatible and therefore potentially valuable in orthopedic applications. A chemical initiation system has been developed for the silorane polymer to expand its usefulness. One of the negative aspects of current bone cements is high polymerization exothermicity which can cause thermal necrosis. Therefore, this study was completed to compare the exothermicity and handling properties of our chemically initiated silorane with commercial bone cement. The objective of this study was to determine if a chemically initiated silorane polymer (CC-SP) would have a lower exothermicity than traditional polymethyl-methacrylate bone cement (BC) and/or light initiated silorane polymer (LC-SP) while maintaining equivalent handling properties as BC. Methods: Exothermicity was measured for SP and BC with a thermocouple secured onto a glass slide. The monomer was mixed with initiators for 60 seconds and then mounded on the thermocouple. Temperature readings were collected (1Hz) to determine the maximum temperature. Handling time was measured by penetrometer readings. The materials were mixed and then placed in an aluminum washer (12.7mm diameter, 2.5mm deep). Post-mixing, penetration (mm) measurements were taken periodically with a 0.5N load applied to the penetrometer cone for 5s. Results: Some comparative results show a significant difference (p<0.05) between maximum exotherms (n=8) of BC (61.6±3.7°C), LC-SP (127.2±6.2°C), and CC-SP (39.0±6.2°C). However, the handling time of the CC-SP was shorter than BC. Conclusion: CC-SP has a significantly lower maximum exotherm than traditional BC, which reduces the risk of thermal necrosis. Future studies will explore various fillers and initiator systems to increase working time of the silorane system while maintaining low exotherm. Supported in part by NIH-NIDCR Grant T32 DE07294, NIH-NIDCR Grant R21 DE 018336 and DOD Grant W81XWH.