Light Source Influences the Conversion Degree of Dual-Curing Luting Composites

METHODS: 120 cylindrical onlays (Signum composite – Heraeus - shade A2, 6mm of diameter) of different thickness (2mm, 3mm, 4 mm) were prepared in a custom template. The specimens were divided into four groups (N=30)and luted with different LED light sources (Bluephase C8-Ivoclar Vivadent 800mW/cm2*s for 60s, Bluephase G2-Ivoclar Vivadent 1200 mW/cm2*s for 40 s, Valo-Ultradent, 1000mW/cm2*s for 48s). In each group, 15 inlays were cemented with MultilinkAutomix (Ivoclar-Vivadent), while 15 were cemented with Calibra (Dentsply) interposing interposing the cement between a glass plate and a restoration; the curing tip was shielded so that the light reached the composite material only through the onlay. Each sample was examinated using the Micro-Raman Dilor HR LabRam spectrometer to evaluate the polymer DC. Statistical analysis was carried out using ANOVA test, Tukey's and Fisher's test.

RESULTS: Multilink Automix DC is significantly higher (p=<0.05) than that of Calibra, regardless of the radiation source used for curing. Bluephase C8 allows to obtain DC values significantly lower (p=<0.05) than those obtained with Valo, while there are no significant differences with Bluephase G2. 

CONCLUSIONS: High radiation power allows a higher degree of conversion in both tested materials. Greater collimation of the light beam allows, even in lamps with medium power, to obtain high DC and a reduced standard deviation.