Objective: This study analyses the effects of shade and thickness of porcelain on light transmission.
Methods: Thirty-five porcelain disks (25 Vita Mark II, 10 Empress Cad) were made to combine four different thicknesses (2, 4, 8 and 10 mm) and six shades (0M1; 1M1; 2M2; 4M2; A1HT A1LT). An integrative sphere coated with barium sulfate (Gigahertz-Optik, Puchheim, Germany) coupled with a P9702 optometer was used to measure the percentage of transmitted light power (PTLP). Four high power light curing units were based on the three technologies (LED, Plasma and halogen) were used.
Results: The percentage of transmitted light power (PTLP) through ceramics range between 0.01 and 13.95, with an overall mean of 2.95 (SD= 4.02). The mean PTLP per curing unit, through 2 mm thickness, were 9.65 (Celalux), 9.15 (Flipo) and 8.27 (SM light). Globally, the mean values of PTLP per thickness were 9.02 (2 mm), 1.70 (4 mm), 0.78 (8 mm) and 0.32 (10 mm). Analysis of variance for PTLP showed a significant effect of thickness (p=0.0001), shade (p=0.0001) and curing unit (p=0.0001).
Conclusions: Whatever the shade or curing unit, there was a significant decrease in light transmission as the sample porcelain thickness increased. For the same thickness most shades presented statistical difference between the PTLP. However, for larger thicknesses, the curing unit effect was no longer statistically significant.