Pulp response after CO2 laser irradiation to rat exposed dentin

Objectives: In clinically, CO2 laser has been used for a treatment of hypersensitivity tooth which surface were not covered by enamel. However, pulp response after CO2 laser irradiation to dentin was still not clear. The purpose of this study was to investigate the expression of TNFa- and IL-1-mRNA of rat dental pulp after CO2 laser irradiation to cusp of molar tooth where there was no covering with enamel because of abrasion.

Methods: Adult male Sprague-Dawly rats, weighing about 200 g/BW, were used. The CO2 laser was irradiated at cusp legion of upper first molar for morphological observations and for detection of mRNA expression. Irradiation conditions: The CO2 laser (Panalas C05Sigma; Panasonic Dental Co. Osaka, Japan) was Super Pulse-1 mode, 2W, pulse 0.6ms, and expose time was 8.8s. Total energy was 4J (Density; 203.84 J/cm2). The animals were sacrificed at 0, 3, 6, 12, 24 and 48 hrs after the irradiation. For morphological observations, the sections were observed HE staining. For Quantitative RT-PCR, laser irradiated tissues were detected expression of TNFa-, IL-1-mRNA.

Results: In histological observation, degeneration of pulp tissue in the pulp horn was observed. Expressions of both TNFa- and IL-1-mRNA were significantly higher at 6, 12, 24 hrs after laser irradiation compare to those of control group (p<0.05). However, there were no significant differences of the expressions of both TNFa- and IL-1-mRNA at 48 hrs after the irradiation.

Conclusions: An increased expression of TNFa- and IL-1 -mRNA in pulp cell after CO2 laser irradiation to rat molar dentin seems to be started to the immune and pathological cytokine pathways involved in many inflammatory responses in pulp tissue. This study was supported by TDCHRC7 of Tokyo Dental College.