Effect of age on physiologic and mechanically stressed rat alveolar bone: a cytologic and histochemical study

The effect of age on physiologic and mechanically stressed rat alveolar bone was assessed with special focus on bone formation and resorption in maxillary molar sections of 1-, 4-, 9-, 16-, and 24-month-old male Fischer rats. Tetracycline- and calcein-labeled undecalcified sections were used for observation by confocal laser scanning microscopy and contact microradiography. The localization of osteoclasts and the morphological change of osteoblasts were observed on decalcified sections. Mechanical stress was applied by an orthodontic elastic inserted between the first and second maxillary molars for 7 days. Results showed that bone-formative activity of osteoblasts and bone-resorptive activity of osteoclasts declined with age around the maxillary molar section of physiologic rat alveolar bone. However, results of mechanically stressed rat alveolar bone revealed no evidence of numerical difference in number, size, and activity of osteoclasts and osteoblasts among the ages, suggesting that mechanical stress provokes a higher activity of osteoblasts and osteoclasts similarly in both adult and younger rat alveolar bone.