Abstract:

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.

Key words: rat, orthodontics, tooth movement, low level laser, osteoclasts, collagen fiber, Masson staining, TRAP staining

摘要：

目的 探讨低能量激光（low level laser,LLL）对大鼠牙移动后保持过程中破骨细胞和胶原纤维改建的影响,为临床应用提供实验依据。方法 8周龄Wistar大鼠20只,随机选取5只为基线组：不施加正畸力,作为空白对照。其余15只建立上颌第一磨牙近中移动模型,加力结束去除加力装置后随机3组,每组各5只。对照组：即刻拆除加力装置后,不采用任何保持措施;保持组：拆除口内装置后,结扎丝拧成麻花状作为固定保持,维持大鼠第一磨牙与切牙之间的距离;保持+激光组：加力结束拆除口内装置后,结扎丝拧成麻花状作为固定保持,并在去除加力装置后的第0天、第3天、第6天、第9天、第12天应用LLL照射。2周后处死所有大鼠,取第一磨牙组织块,用HE染色、TRAP染色、Masson染色法观察破骨细胞以及胶原纤维的分布,分析牙槽骨及胶原纤维改建的过程。结果 去除加力装置后2周,基线组牙根两侧可见胶原纤维沉积,牙根远中侧未见明显破骨样细胞;对照组牙根两侧未见明显胶原纤维沉积,远中侧破骨细胞活动活跃;保持组牙根两侧可见胶原纤维沉积,远中侧亦可见破骨细胞活动,但不如对照组活跃;保持+激光组牙根两侧胶原纤维合成明显,未见明显破骨细胞分布,且保持+激光组与其余各组差异具有统计学意义（P＜0.05）。结论 固定保持同时进行低能量激光照射能有效促进大鼠牙移动后保持阶段内胶原纤维的合成,抑制破骨细胞活动,从而减少磨牙复发的可能性。

关键词: 大鼠, 正畸, 牙移动, 低能量激光, 破骨细胞, 胶原纤维, Masson染色, TRAP染色