Evaluation of the influence of polymerization light intensity, irradiation time, and source distance on the depth of cure of resin based composite

Background/Aim: To evaluate the effect of curing light parameters (intensity, duration, and distance of curing tip) on the depth of cure of conventional resin-based composite. Material and methods: Cylindrical specimens made of nanohybride resin-based composite are cured with 12 different curing protocols, combined with 3 different light intensities (300, 650, and 1100 mW/cm²), 2 distances of curing tip (0 and 8 mm), and 2 exposure times (20 and 40 seconds). The specimens were measured after scraping the uncured composite material according to the ISO 4049 standard. The depth of cure was calculated by dividing the length of the remaining composite by 2. Data were analyzed using: Levene's test and Multivariate Analysis-of-variance (MANOVA). The level of significance was set at P<0.05. Results: The highest depth of cure (3.332 mm) was observed for curing protocol 1100mW/cm²/0mm/40s. The lowest depth of cure had specimens cured with curing protocol 300 mW/cm²/8mm/20s (2.034mm). MANOVA showed a significant influence of the distance of the curing tip (P=0.014; P=0.001) regardless of light intensity and duration of exposure time. Exposure time was a significant factor (P=0.009) when cured from different distances. Although higher light intensity produced a higher depth of cure, light intensity was not a significant factor. Conclusions: The depth of cure can be increased by reducing the distance of the curing tip, when it is possible. At a distance of 8 mm, the depth of cure can be increased by a longer exposure time, regardless of curing light intensity.