Abstract
The present study examined the age-related changes of the physiological root resorption and the maturation process of odontoclasts during the physiological distal movement of rat molars. During physiological tooth movement, odontoclasts appeared to resorb the distobuccal root of the maxillary second molars. The number of odontoclasts increased in rats from 4 to 7 weeks of age, and gradually decreased from 10 to 13 weeks of age.
On the basis of light microscopic findings, it was found that root resorption was divided into the three stages of early, resorption, and final stage. During the early stage, odontoclasts, spindle-shaped mononuclear cells, and fibroblasts, were observed in the large and small resorption lacunae, and many blood vessels and fibroblasts were found in the periodontal space. During the resorption stage, resorption lacunae became larger, and the large odontoclasts were found within them. At the final stage, odontoclasts were rare, and the resorption lacunae were repaired by deposition of the cementum. The periodontal space became wider, and the arrangement of the periodontal fibers became regular.
Root resorption during the early stage was also examined by electron microscopy. The odontoclasts with the resorption zone, which was not clearly differentiated into clear zone and ruffled borders, began to resorb the root, resorbed the cementum, and extended to the dentin. At the surface of the resorption lacunae, lateral stripes of collagenous fibrils were found. As the resorption proceeded, the odontoclasts developed a well-formed ruffled border, and the deposition of new cementum produced by cementoblast-like cells was observed along the resorption lacunae.
