Influence of photoinitiator system and nanofiller size on the optical properties and cure efficiency of model composites.

OBJECTIVE: To establish the relationship between photoinitiator system and nanofiller size on the optical properties and cure efficiency of model composites. METHODS: Model composites based on BisGMA/TEGDMA (60:40mol%) were loaded with 40wt% of 7nm or 16nm-sized filler particles. One of the following photoinitiator systems was added: camphorquinone (CQ) associated with an amine (EDMAB), monoacylphosphine oxide (TPO), or bysacylphosphine oxide (BAPO). The optical properties of disk-shaped specimens were measured 24h after curing and repeated after storage in water for 90 days and coffee for 15 days. A large spectrum LED unit (Bluephase G2, Ivoclar Vivadent) was used for photoactivation. CIE L*a*b* parameters, color difference (DeltaE), and translucency parameter (TP) were calculated. Knoop hardness readings were taken at top and bottom composite surfaces. Cure efficiency was determined by bottom/top hardness ratio. Data were statistically analyzed at alpha=0.05 significance level. RESULTS: Composites formulated with 16nm particles had higher CIE L* than those with 7nm particles in all storage conditions. BAPO-based composites generally had lower CIE a* than the other composites. The group TPO+16nm before storage and all groups with 16nm-sized particles after storage had lower CIE b* (i.e. lower degree of yellowing) than the other groups. TPO-based materials had higher color stability. The cure efficiency was not significantly affected by photoinitiator system or particle size. CQ+7nm had the lowest and BAPO+16nm the highest hardness values. SIGNIFICANCE: Combination of photoinitiator system and filler particle size might affect the optical properties of composites, with low influence on cure efficiency.