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How do infrared and near-infrared lasers influence autophagy and alveolar bone remodeling in rats during orthodontic tooth retention?

Year: 2025

Type: article

Abstract: BACKGROUND: Few studies have explored the association between autophagy and osteogenesis during orthodontic retention. This study compared the impact of 660-nm infrared (IR) and 808-nm near-infrared (NIR) lasers on the autophagy and alveolar bone remodeling in rats during orthodontic tooth retention. METHODS: Seventy-five rats were divided into three groups: Group A (control), Group B (660 -nm IR irradiation), and Group C (808-nm NIR irradiation). A 50-g force was applied by ligating a nickel-titanium coil spring from the left upper first molar to the incisors to move the molar in a mesial direction for 3 weeks, with weekly force applications. Post-force application, a fixed retainer was used to maintain the molar-incisor distance on days 1, 7, 14, 21, and 28, establishing a retention model; 660-nm and 808-nm lasers (100 mW, 9 mm spot, 5 J/cm²) were directed to the buccal and palatal gingiva at the mid-root height of the first molar for 30 s every 3 days. After removal of the fixed retainers, the rats underwent a 3-day recovery phase before euthanasia on days 4, 10, 17, 24, and 31 post-irradiation. The relapse rates of the molar were assessed by 3Shape scanning, alveolar bone density using micro-computed tomography, and periodontal tissue remodeling through histological staining at the tensile zone of the molar. RESULTS: With longer retention, the relapse rate and the number of tartrate-resistant acid phosphatase (TRAP)-positive cells decreased. At the same time, alveolar bone density and autophagy protein Beclin-I/osteoprotegerin (OPG) expression increased, peaking at 28 days (P < 0.001). From days 7-21, Group C exhibited the lowest relapse and TRAP-positive cells, and the highest bone density and Beclin-1/OPG levels (P < 0.05). At day 28, Groups B and C exhibited comparable outcomes, both superior to Group A (P < 0.001). CONCLUSION: Compared with 660-nm IR irradiation, 808-nm NIR irradiation more effectively enhanced autophagy, promoted periodontal remodeling, reduced rather than inhibit osteoclast proliferation, and decreased relapse during retention; however, the effects diminished over time.

Source: BMC Oral Health

DOI: 10.1186/s12903-025-07385-1