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| Effect of He-Ne laser irradiation on root resorption induced by orthodontical treatment |
| XU Yan1, and SUN Xinhua2. |
1. Department of Stomatology， General Hospital of Chinese People’s Armed Police Forces, Beijing 100039, China.
2. Department of Orthodontics, School of Stomatology, Jilin University, Changchun 130041, Chin |
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Abstract Objective To investigate the effect of low power laser irradiation on root resorption induced by heavy force during the experimental tooth movement.Methods Fifty-five Wistar rats were used in this study. The animals were divided into 11 groups of 5 animals each: 5 groups of animals as irradiated groups were exposed to low power laser irradiation for 15 minutes per day after orthodontic treatment, 5 groups of animals as control groups did not receive low power laser irradiation, and 1 group of animals as blank control group was left untreated. An orthodontic appliance, consisting of a coil spring, connected the left first molar and the two incisors by ligature wire. 90 g force was used in the experiment as heavy force. The animals were sacrificed on days 1, 4, 7, 14, and 21. Tartrate resistant acid phosphatase (TRAP) staining and HE staining were used for observing root resorption and counting osteoclast cells. t-test was used for statistical analysis.Results The earliest root resorption was detected on day 4 in the circumference of necrotic hyalinized tissue. On day 7, the osteoclast-like cells close to cementum in control group outnumbered those in irradiated group (P<0.05), reaching the peak on day 14(P<0.01). On day 14, serious root loss deep into dentine could be often observed in the pressure side. After 21days, resorption stopped generally. The area of resorption in irradiated group was significantly smaller than in control group (P<0.01). Besides, the repair process of root resorption was detected on day 21 in the irradiated group. The cells involved in root resorption were mono- and multi-nucleated TRAP-positive cells.Conclusions Low power laser irradiation not only accelerates alveolar bone and periodontal tissue turn-over during tooth movement but also reduces root resorption effectively.
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Received: 10 June 2011
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