2010 Volume 53 Issue 5 Pages 495-501
Irradiation of gallium-aluminum-arsenide (GaAlAs) semiconductor laser to rat molars is known to induce the formation of mineralized tissue in the pulp chamber. The purpose of this study was to analyze mRNA expression levels of selected non-collagenous proteins in GaAlAs laser-irradiated rat molars by means of reverse transcription-polymerase chain reaction (RT-PCR). The mesial surface of the upper right first molar of 8-week-old Wistar rats was irradiated by a pulsed GaAlAs semiconductor laser (Lightsurge 3000, Osada) at an output power of 1.5W for 60 seconds, 3 times. The first molars of unirradiated 8-wk-old rats were used as the control. After 1, 3 and 7 days, the first molars were extracted, and total RNAs were isolated from the coronal pulp. Then, expression levels of mRNAs for osteopontin, osteonectin, osteocalcin, dentin sialophosphoprotein, dentin matrix protein 1, and bone sialoprotein were analyzed by means of RT-PCR. The pulp reaction was examined histologically. mRNA expression levels of all the proteins were upregulated by 3 days, and the upregulation was maintained at 7 days. Histological observation revealed localized tissue necrosis in the mesial portion of the irradiated pulp at 1 and 3 days, whereas rearrangement of odontoblast-like cells and a small amount of newly formed calcified matrix were recognized at 7 days. In conclusion, it was demonstrated that GaAlAs laser irradiation to rat molars caused upregulation of mRNAs for non-collagenous proteins prior to the appearance of newly-generated mineralized tissue-forming cells.
