LED and Halogen Light Transmission through a CAD/CAM Lithium Disilicate Glass-Ceramic

The effect of thickness, shade and translucency of CAD/CAM lithium disilicate glass-ceramic on light transmission of light-emitting diode (LED) and quartz-tungsten-halogen units (QTH) were evaluated. Ceramic IPS e.max CAD shades A1, A2, A3, A3.5, high (HT) and low (LT) translucency were cut (1, 2, 3, 4 and 5 mm). Light sources emission spectra were determined. Light intensity incident and transmitted through each ceramic sample was measured to determine light transmission percentage (TP). Statistical analysis used a linear regression model. There was significant interaction between light source and ceramic translucency (p=0.008) and strong negative correlation (R=-0.845, p<0.001) between ceramic thickness and TP. Increasing one unit in thickness led to 3.17 reduction in TP. There was no significant difference in TP (p=0.124) between shades A1 (ß₁=0) and A2 (ß₁=-0.45) but significant reduction occurred for A3 (ß₁=-0.83) and A3.5 (ß₁=-2.18). The interaction QTH/HT provided higher TP (ß₁=0) than LED/HT (ß₁=-2.92), QTH/LT (ß₁=-3.75) and LED/LT (ß₁=-5.58). Light transmission was more effective using halogen source and high-translucency ceramics, decreased as the ceramic thickness increased and was higher for the lighter shades, A1 and A2. From the regression model (R²=0.85), an equation was obtained to estimate TP value using each variable ß₁ found. A maximum TP of 25% for QTH and 20% for LED was found, suggesting that ceramic light attenuation could compromise light cured and dual cure resin cements polymerization.

halogen dental curing lights; LED dental curing lights; lithium disilicate; dental porcelain; glass ceramics