2011 Volume 22 Issue 2+3 Pages 93-99
Objective: The usefulness of laser irradiation for socket preservation in clinical cases has recently been reported, and the effective laser irradiation conditions for healing of the extraction wound have also been investigated. It was reported by our laboratory that HLLT and LLLT therapies using a CO2 laser for extraction sockets resulted in characteristic new bone formation and the maintenance of a high alveolar crest in rats. However, the mechanism of healing promotion by CO2 laser irradiation remains unclear, so we investigated the emergence of myofibroblasts (α-smooth muscle actin (α-SMA)) involved in granulation tissue scar contracture in extraction wounds and changes in the expression of transforming growth factor-beta 1 (TGF-β1) associated with myofibroblast differentiation and apoptosis.
Subjects and Methods: Seventy-two 5-week-old male Wistar rats were used. The first molar was extracted to prepare an extraction socket model. The rats were divided into CO2 laser-irradiated and non-irradiated (control) groups and pathologically compared. In the CO2 laser-irradiated group, HLLT was performed immediately after tooth extraction, followed by LLLT after one day, corresponding to clinical cases. The irradiated tissue including the extraction socket was excised 6 hours and 3, 5, 7, 10, and 21 days after treatment, fixed in 4% paraformaldehyde, decalcified in 10% EDTA solution, and paraffin-embedded employing the standard method, and serial sagittal sections were prepared. Granulation tissue of the superficial layer of the extraction socket was immunohistologically investigated using anti-α-SMA and anti-TGF-β1 antibodies. The number of α-SMA-positive cells and TGF-β1-positive area were measured, and the significance of differences was tested.
Results: On immunostaining with anti-α-SMA antibody, there were many α-SMA-positive cells in the non-irradiated group at 3 and 7 days, whereas significantly fewer positive cells were noted in the CO2 laser-irradiated group (p < 0.05). On immunostaining with anti-TGF-β1 antibody, TGF-β1-positivity was not marked in the CO2 laser-irradiated group, compared to that in the non-irradiated group, and a significant difference was noted 5 days after treatment (p < 0.05).
Conclusion: The combination of CO2 HLLT and LLLT for the extraction sockets inhibited scar formation in the sockets, and the involvement of TGF-β1 was suggested.