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This study investigated the effects of growth and tooth loading on the adaptation of the developing periodontium adjacent to the tooth root as the tooth erupts into function. Growth and occlusal function were expected to lead to increased boneMoreThis study investigated the effects of growth and tooth loading on the adaptation of the developing periodontium adjacent to the tooth root as the tooth erupts into function. Growth and occlusal function were expected to lead to increased bone apposition. The supporting alveolar bone was expected to develop a dominant trabecular orientation (anisotropy) and to increase remodeling through bone resorption only after occlusal loading. Minipigs with erupting and occluding lower first molars (M1s), as well as minipigs with one side upper opponent teeth extracted prior to occlusal contact with the M1 were used as experimental models.-Biomechanical testing and microCT analysis demonstrated that growth and occlusal function led to a stiffer PDL and distinct ABP development. In cancellous bone, trabeculae became thicker and decreased in number after growth and occlusal loading. However, occlusal function did not lead to increased bone density or structural anisotropy, nor was alveolar bone stiffness increased.-Bone resorption did not appear to be a key factor in alveolar bone development as an erupting tooth becomes functional. The occluding alveolar bone did not demonstrate higher osteoclast numbers than the erupting specimens. After occlusal loading, the alveolar bone did not show remodeling activity by secondary osteons. Furthermore, the expression of important osteoclastogenesis molecules, RANKL protein and mRNA, as well as the Csf-1 mRNA, showed no difference with or without occlusal loading. Occlusal function did not promote increased resorption activity in supporting alveolar bone.-Cumulative bone apposition plays the key role in bone adaptation as M 1 erupts into function. Fibrolamellar bone, a mixture of woven bone and lamellar bone, were found both before and after occlusal function. Both bone marker apposition study and Q RT-PCR results showed the bone apposition activity was not increased after occlusal function but stayed at a steady state.-In conclusion, growth determines the adaptation of alveolar bone during tooth eruption. The impact of occlusal function on alveolar bone may need a more extensive period of time to demonstrate structural changes.