Effect of laser phototherapy on the hyalinization following orthodontic tooth movement in rats.

OBJECTIVE: We aimed to assess histologic changes after the use of laser phototherapy (LPT) during induced tooth movement with 40 g/F on young adult male rats. BACKGROUND DATA: Hyalinization is a sterile necrosis at the pressure zone of the periodontal ligament observed during the initial stages of the orthodontic movement, and extensive hyaline areas might cause an important delay in the tooth movement. The use of LPT is considered an enhancement factor for bone repair, as it stimulates microcirculation as well as the cellular metabolism. MATERIALS AND METHODS: Thirty animals were divided into two groups (n=15), named according to the time of animal death (7, 13, and 19 days). Half of the animals in each group were subjected to irradiation with infrared (IR) laser (λ790 nm, round shaped beam, 40 mW, continuous wave (CW), diameter=2 mm (0.0314 cm(2)), 1.273 W/cm(2), time=2×112 sec+1×275 sec (total time 499 sec), 2×142.6/4.48 J+1×350/11 J, 635.2 J/cm(2)/20 J/ session), during orthodontic movement, the other half were used as nonirradiated controls. After animal death, specimens were sectioned, processed, and stained with hematoxylin and eosin (HE) and Sirius Red, and were used for semi-quantitative histologic analysis by light microscopy. Data were statistically analyzed. RESULTS: We demonstrated that LPT positively affected an important aspect of dental movement; the hyalinization. In the present study, we found a significant reduced expression of hyalinization after 19 days. On irradiated subjects, hyalinization was increased at day 7 with significant reduction at day 13. CONCLUSIONS: It is possible to conclude that the use of laser light caused histologic alterations during the orthodontic movement characterized by increased formation of areas of hyalinization at early stages, and late reduction when compared to nonirradiated animals.

Laser-induced alveolar bone changes during orthodontic movement: a histological study on rodents.

OBJECTIVE: The aim of this study was to assess by light microscopy changes in alveolar bone during orthodontic movement in rats. BACKGROUND: Orthodontic movement causes both removal and deposition of bone tissue. The use of laser phototherapy (LPT) is considered an enhancement factor for bone repair. METHODS: Thirty Wistar rats were divided into two groups (n = 15) and subdivided according to animal death (7,13, and 19 days). Half of the animals in each group were treated with LPT during orthodontic movement. After animal death, specimens were processed and underwent histological and semi-quantitative analyses (HE and Sirius red). RESULTS: LPT-irradiated specimens showed significantly higher numbers of osteoclasts when compared with controls at both 7 (p = 0.015) and 19 (p = 0.007) days, as well as significant increases in the number of osteoblasts (p = 0.015) between days 7 and 13. The amount of collagen matrix was significantly reduced between days 7 and 13 at both pressure and tension sites in controls (p = 0.015) but not in LPT-treated animals. LPT-treated subjects showed significantly greater deposition of collagen matrix at the pressure site at both the thirteenth (p = 0.007) and nineteenth days (p = 0.001). At the tension site, a significant increase in the amount of collagen matrix was observed in non-irradiated specimens (p = 0.048) between days 7 and 19. CONCLUSIONS: LPT caused significant histological changes in the alveolar bone during induced tooth movement, including alterations in the number of both osteoclasts and osteoblasts and in collagen deposition in both pressure and tension areas.

Tooth movement after infrared laser phototherapy: clinical study in rodents.

OBJECTIVES: The aim of this research was to investigate the influence of low-power laser on tooth movement in rats. BACKGROUND: Tooth movement is closely related to the process of bone remodeling. The biologic result, with the application of a force to the tooth, is bone absorption on the pressure side and neoformation on the traction side of the alveolar bone. The laser photobiomodulation is capable of providing an increase in cellular metabolism, blood flow, and lymphatic drainage. METHODS: Thirty young-adult male Wistar rats weighing between 250 and 300 g were divided into two groups, control and experimental, containing 15 animals each. The animals received orthodontic devices calibrated to release a force of 40 g/F, with the purpose of moving the first upper molar mesially. Low-intensity laser, wavelength 790 nm, was used in the experimental group; the dose was 4.5 J/cm(2) per point, mesial and distal, on the palatal side, 11 J/cm(2) on the buccal side, and this procedure was repeated every 48 h, totaling nine applications. The active movement was clinically evaluated after 7, 13, and 19 days. RESULTS AND CONCLUSION: The results showed no statistically significant difference, p = 0.079 (T0-T7), p = 0.597 (T7-T13), and p = 0.550 (T13-T19) between the laser and control groups on the amount of tooth movement in the different times evaluated. It may be concluded that laser phototherapy, with the parameters in the present study, did not significantly increase the amount of tooth displacement during induced orthodontic movement in rodents.