Real-time multispectral transmission of hard tooth tissues and dental composites with their heating

Abstract

The objective of the study was to investigate the real-time transmission of Violet, Blue, Red and Near Infra-Red (NIR) irradiation through 2 or 4 mm thick dental composites and tooth tissue samples at varying positions of Light Curing Unit (LCU) with polymerization temperature monitoring.

Methods: The composites tested were: Filtek Universal Restorative (FUR), Filtek One Bulk Fill (FBF), Tetric EvoCeram (TEC), Tetric Bulk Fill (TBF) and Tetric PowerFill (TPF). The new LCU Pinkwave (a four-wavelength source manufactured by Vista Apex, USA) was placed either centrally or eccentrically for 3 mm above the sample. A Fiber spectrometer detected irradiation and Infrared Thermal camera polymerization temperatures.

Results: All eccentric LCU positions significantly weaken transmitted spectra for all composites in both thickness, jeopardizing Blue light. The LCU position did not affect transmitted irradiation for tooth tissues. The reduction in wavelength intensity when penetrating through thicker compared to thinner composite samples was 62%, 50% and 31% for Blue, NIR and Red, respectively, and 90%, 50% and 35% for tooth tissue samples, respectively. The temperature of bulk fill composites with additional photoinitiators rises faster. Eccentric LCU positions cause a significant decrease in both speed and the maximal value of temperature rise. Red and NIR irradiations contribute to the polymerization temperature.

Significance: Tested LCU source cause considerable inhomogeneity in the emitted and transmitted spectra. Tooth tissues homogenize irradiation, but drastically attenuates it. Red light has better potential than Blue light concerning penetration and could be further investigated as the wavelength for activation of an adjusted photoinitiator.

Keywords: Light curing unit; Multispectral; Polymerization temperature; Quadwave; Radiation uniformity; Red curing light; Tooth tissue attenuation; Transmittance.