INFLUENCE OF LONG-TERM WATER IMMERSION ON THE COEFFICIENT OF THERMAL EXPANSION OF COMPOSITE RESINS

AIYANG SONG¹, JIAHUI ZHANG², ZHAOYING LIU³, QI ZHAO⁴, PING GAO⁵, QIANQIAN WEI⁶, SONG ZHU^7*

¹School and Hospital of Stomatology, Jilin University, Changchun, Jilin, People’s Republic of China - ²School and Hospital of Stomatology, Jilin University, Changchun, Jilin, People’s Republic of China - ³School and Hospital of Stomatology, Jilin University, Changchun, Jilin, People’s Republic of China, - ⁴School and Hospital of Stomatology, Jilin University, Changchun, Jilin, People’s Republic of China - ⁵School and Hospital of Stomatology, Jilin University, Changchun, Jilin, People’s Republic of China - ⁶School and Hospital of Stomatology, Jilin University, Changchun, Jilin, People’s Republic of China - ^7*School and Hospital of Stomatology, Jilin University, Changchun, Jilin, People’s Republic of China

Introduction: Light-cured composite resins have been widely used as dental restoratives. The purpose of this study was to investigate the change of coefficient of thermal expansion (CTE) of low-shrinkage composite resins after long-term water immersion.

Materials and methods: Immersed in distilled water at 37°C for 24 h, 1 month, 3 months and 6 months, the CTE of six kinds of composite resin were measured with a thermomechanical analyzer (TMA). The measured data were statistically analyzed. Additionally, the surface morphology of the composite resins were evaluated after long-term water immersion.

Results: After water immersion, the CTE increased initially, then reduced or remained stable with changing temperature and time.

Conclusion: The change of the CTE is closely related to the composition of the composite resin. The CTE of epoxide and pre- polymerized filler in low-shrinkage composite resin is relatively stable, and the CTE of high-content filler nanometer resin is the clos- est to the thermal expansion coefficient of tooth structure.