Effect of Ga-Al-As Laser Irradiation at Wavelengths of 660 nm or 810 nm with a Constant Output on Hard Tissue Forming Ability in Human Pulp

Abstract

 Purpose: In order to preserve the dental pulp, it is necessary to effectively promote the formation of hard tissue. In recent years, research has been carried out with the aim of developing an adjunct to pulp capping by using Ga-Al-As lasers on human dental pulp cells (hDPCs) to promote the formation of hard tissue. However, their effects on hDPCs have not yet been clarified. The present study investigated the effect of the wavelength of laser irradiation on the acceleration of calcification in hDPCs.

 Methods: This study was approved by the ethics committee of Nihon University School of Dentistry, Matsudo, Japan. hDPCs were harvested from third molars extracted under aseptic conditions from 20-year-old patients undergoing orthodontic treatments. hDPCs were cultured in alpha-minimal-essential medium supplemented with 10% fetal bovine serum for up to 30 days, and irradiated with a Ga-Al-As laser at a wavelength of 660 nm or 810 nm and an output of 300 mW, approximately 10 cm above the culture supernatant. Alkaline phosphatase (ALP) activity and bone morphogenetic protein (BMP)-2 production were evaluated and staining of calcified nodules was performed.

 Results: Increase in ALP activity was observed when using Ga-Al-As lasers of both wavelengths and increased dyeability of von Kossa staining was observed in both the groups. Moreover, the expression level of BMP-2 gene and protein in the 660-nm irradiation group was notably increased, but no significant difference in BMP-2 expression was observed in the 810-nm irradiation group.

 Conclusion: These findings suggest the prospective use of Ga-Al-As lasers to enhance the formation of hard tissue in hDPCs, but also indicate that the expression level of BMP-2 may differ when using lasers at different wavelengths.