2014 Volume 25 Issue 2 Pages 75-81
The usefulness of high reactive-level laser therapy (HLLT) and low reactive- level laser therapy (LLLT) using a carbon dioxide laser for socket preservation in clinical cases has recently been reported. However, the mechanism of the healing-promoting effects of carbon dioxide laser irradiation remains unclear. Therefore, the emergence of osteoclasts and change of new bone formation of rats' extraction sockets by the carbon dioxide-enhanced healing process were investigated.
Ninety-nine 5-week-old male Wistar rats were divided into an HLLT irradiation group (group L1), a combination of HLLT+LLLT irradiation group (group L2) and a non-irradiation group (control group) and compared. The upper-left first molar was extracted to prepare an extraction socket model. The laser irradiation groups (groups L1 and L2) underwent HLLT immediately after tooth extraction and then LLLT 1 day post-extraction (group L2). The irradiated tissues including the extraction socket were excised 6 hours and 3, 5, 7, 10 and 21 days after extraction. Then, they were fixed in 4% paraformaldehyde, decalcified in 10% EDTA solution, and paraffin-embedded employing the standard method. Next, serial sagittal sections were prepared, and granulation tissue of the extraction socket was histologically investigated using hematoxylin-eosin staining.
On day 3, many osteoclasts appeared and active bone resorption at the socket was noted in the irradiation groups (groups L1 and L2) compared to the control group. On day 7, new bone formation started from the superficial layer to the middle layer of the socket in the irradiation groups. However, new bone formation was observed around the socket in the control group. On day 21, a concavity existed in the alveolar crest region in the control group, whereas the region was flat without concavity in the irradiation groups (groups L1 and L2). On osteomorphometry, the alveolar crest height in group L2 (0.7660 ± 0.039) was significantly higher than that in the control group (0.6516 ± 0.079).
Carbon dioxide laser irradiation may enhance the rapid bone resorption and new bone formation on the superficial layer over the middle layer. It is suggested that carbon dioxide laser irradiation promotes the healing of tooth extraction sockets.
