RESUMO
Objective@#To investigate the effect of low level laser on osteoclast and collagen fiber remodeling during the process of tooth retention after tooth movement in rats and to provide the experimental basis for clinical application.@*Methods @# In total, 20 eight-week-old Wistar rats were selected to establish a mesial movement model of the maxillary first molar and then randomly divided into four groups after the appliance was removed. In total, 5 rats were included in each group, including baseline group (without force as blank control), control group (without any intervention after removing the force appliance), retention group (teeth were wrapped with orthodontic ligature wires that were screwed into hemp flower as fixed retention to maintain the space between the first molar and incisor after appliances were removed) and retention and low energy laser irradiation group (teeth were wrapped with the orthodontic ligature wires that were screwed into hemp flower as fixed retention and low energy laser irradiation was applied on days 0, 3, 6, 9 and 12 after appliance removal). Two weeks later, all the rats were sacrificed and the first molar tissue blocks of each group were collected. The distribution of osteoclasts and collagen fiber were studied by HE staining, TRAP staining and Masson staining to illustrate the process of alveolar bone and collagen fiber remodeling.@*Results @# Two weeks after appliances were removed, collagen fibers were deposited on both sides of the root in the baseline group, but no osteoclasts were observed in the distal side of the root. In the control group, collagen fibers on the two sides of the root were not obvious and osteoclasts were active on the distal side. In the retention group, collagen fibers were obvious on the two sides of the root and the osteoclasts on the distal side were less active than the control group. Regarding the retention and low energy laser irradiation group, collagen fibers were significantly obvious and osteoclasts were not seen. The difference was statistically significant between the retention and low energy laser irradiation group and the other three groups (P＜0.05). @*Conclusion@#These results suggest that fixed retention with simultaneous low level laser can effectively promote the synthesis of collagen fibers and inhibit the activity of osteoclasts during the process of tooth retention after movement, thus reducing the possibility of molar recurrence.
RESUMO
Objective@#To investigate the effects of Tim-3 on osteoclast-like cell (OLC) formation and bone resorption induced by peripheral blood mononuclear cells (PBMCs). @*Methods@#The expression levels of Tim-3 in of rheumatoid arthritis (RA) patients and healthy controls were detected by flow cytometry. The OLCs were induced by human PBMCs in vitro. The expression levels of tartrate-resistant acid phosphatase (TRAP), cathepsin K (CTSK) and matrix metalloproteinase 9 (MMP9) mRNAs in the formation of OLCs were detected by real-time quantitative PCR. The morphology of OLCs was observed by Wright′s staining and G-actin staining, and the number of OLCs was counted by TRAP staining. The number and area of bone resorption pits in OLCs were detected by the Corning Osteo Assay Surface. @*Results@#The expression levels of Tim-3 in PBMCs of RA patients ([77.31±10.66]%) were significantly higher than that of healthy controls ([51.72±16.69]%, t=7.593, P＜0.01). When PBMCs with different Tim-3 levels were induced into OLCs, the area of bone resorption pits in the high Tim-3 level group ([1.054±0.085] S/mm 2 ) were significantly lower than those in the intermediate Tim-3 level group ([1.889±0.053] S/mm 2 ) and the low Tim-3 level group ([2.763±0.066] S/mm 2 , F=9.318, P＜0.05). @*Conclusion@#Tim-3 may negatively regulate the bone resorption of OLCs.