Evaluation of polymerization in fluoride-containing composite resins

Fluoride-containing restorative materials are frequently utilized to delay or inhibit caries. The quality of the fluoride-containing composite resins was evaluated by testing their microhardness, polymerization shrinkage, thermal expansion coefficient, and surface morphology. Some of them were evaluated in conjunction with the thermocycling process. The microhardness values of the thermocycled specimens were similar to those of the specimens immersed only in distilled water. Among the specimens, Surefil showed the highest (68.6 ± 1.2 Hv) value. A linear correlation was found between microhardness and the filler content (vol%) of the specimens regardless of their states. Polymerization shrinkage rapidly increased during the light curing, and then it reached a plateau. The shrinkage values increased as the specimens became thicker. In a temperature range of 30 ∼ 80 °C, the coefficients of thermal expansion of the control specimens ranged between 43 × 10−6/°C and 77 × 10−6/°C. An inverse correlations were observed between the filler content (vol%) and the coefficient of thermal expansion and between microhardness and the coefficient of thermal expansion of the control specimens. Tetric Ceram showed a perforated or “Swiss-cheese” morphology after thermocycling. It was unique and occurred only in this product.