Wavelength-Dependent Transmitted Irradiance Through Lithium Disilicate Ceramics

Novel photoinitiator systems responsive to longer wavelengths are being developed to overcome limitations of conventional camphorquinone-based resin cements. This study evaluated transmitted irradiance of short-wavelength (blue) and long-wavelength (red) light through lithium disilicate ceramics of varying translucencies, shades, and thicknesses to determine whether longer wavelengths provide enhanced light delivery under standardized conditions MATERIALS AND METHODS: Lithium disilicate CAD/CAM blocks (IPS e.max CAD, Ivoclar Vivadent) with three translucency levels (HT, MT, LT) and three shades (A1, A2, A3) were sectioned into six thicknesses (0.5-3.0 mm) and crystallized (n = 3). Precalibrated experimental LEDs emitting blue or red wavelengths were standardized to 1000 mW/cm². Transmitted irradiance (mW/cm²) was measured using a calibrated spectrometer system with integrating-sphere collection (MARC Light Collector, BlueLight Analytics). Data were analyzed using full-factorial four-way ANOVA and Tukey test (α = 0.05).

All factors significantly influenced irradiance (p < 0.001). Ceramic thickness exerted greatest influence (F = 8270.89), followed by light source (F = 7827.34), translucency (F = 2001.89), and shade (F = 55.02). Red light demonstrated significantly higher transmitted irradiance than blue light across all conditions.

Wavelength significantly affected transmitted irradiance, with red light penetrating more effectively than blue light.