Effects of different numbers of micro-osteoperforations on acceleration of orthodontic tooth movement and alveolar bone remodeling in rats

‌BACKGROUND: Micro-osteoperforations (MOPs) have been confirmed to accelerate orthodontic tooth movement (OTM). However, the optimal number of perforations and the associated changes in alveolar bone structure, composition, and biomechanical properties under different numbers of perforations remain unclear. METHODS: Seventy-two Sprague-Dawley rats undergoing OTM were divided into four groups: OTM (0 MOPs), 2MOP, 3MOP, or 4MOP. Rats were euthanized on Days 3, 7, or 14, and maxillary samples were analyzed using micro-CT, Raman spectroscopy, and nanoindentation to assess bone morphology, composition, and biomechanical properties. RESULTS: MOPs accelerated OTM, with 3MOP and 4MOP showing superior efficacy to 2MOP. Alveolar bone in 3MOP and 4MOP groups exhibited initial resorption followed by regeneration from Days 3-14. Mineral-to-matrix ratios decreased then increased from Days 3-14 across all groups, while carbonate substitution levels showed the opposite trend. Elastic modulus and hardness followed a similar decreasing-increasing pattern. No consistent pattern of intergroup differences was observed in bone microstructure, chemical composition, or biomechanical properties. CONCLUSIONS: MOPs can accelerate OTM, with three MOPs potentially offering a more effective balance between therapeutic efficacy and surgical intervention. No additional acceleration effect was observed in the four-perforation group. Under higher trauma levels (≥3 MOPs), alveolar bone demonstrated a time-dependent transition (initial resorption followed by regeneration) across microstructural, compositional, and biomechanical parameters.