Measurement of Light Power from 940 nm Diode Laser Transmitted Through Tooth Crown

Introduction: Light transmission in biological tissues is used in many subsurface intervention applications, such as photobiomodulation, fluorescence, and laser Doppler flowmetry. The aims of the current study were to measure the light power of a 940-nm diode laser transmitted through dental crowns and to correlate this transmission with crown thickness. Methods: Thirty non-carious extracted human premolar longitudinal-half-crown sections were used in this experiment. The laser device was operated in continuous wave mode at 0.59 W for 10 s. The power density was 468.25 W/cm², and the irradiation dose was 4682.5 J/cm² at the laser tip. The laser irradiation was applied twice to each sample, on the external crown surface and the pulpal surface. The transmitted laser power through the tooth crown was measured using a power meter. Results: Descriptive statistics indicated a transmitted power of 0.044±0.018 W when the external surface of the tooth was irradiated and 0.164±0.039 W when the pulpal side was irradiated. Spearman correlation analysis revealed a non-significant negative relationship between sample thickness and transmitted laser power in the externally irradiated group (r=- 0.111, P=0.558) and a significant negative relationship in the pulpal irradiated group (r=- 0.637, P=0.000). Conclusion: The laser power transmission was four times greater after irradiation of the pulpal side than the external side. Our findings demonstrated that laser transmission is inversely associated with tooth thickness.