Tooth eruption depends in bone resorption: Experimental evidence from osteoetpotrotic (ia) rats

Abstract

Resorption of alveolar bone around erupting teeth is known to be independent of tooth eruption. However, the failure of tooth eruption and reduction in bone resorption in the osteopetrotic rat mutation, incisors absent (ia), suggest that tooth eruption depends upon bone resorption. This hypothesis was tested by determining the effects of neonatal restoration of bone resorption In is rats on eruption of first molars. Newborn is rats were treated with irradiation and spleen cells and tooth eruption and bone resorption were examined 30 days later. In 24 treated is rats at least two molars erupted in every rat and all four molars erupted In 14. In 24 untreated is littermates, no molars erupted in 21, one molar erupted in two and two molars erupted in one rat. All molars erupted in 38 untreated normal littermates. Alveolar bone overlying unerupted first molars In untreated is rats was not present in treated mutant littermates. Neonatally treated is rats had osteoclasts with ruffled borders and no skeletal sclerosis by 30 days. Within 48 hours after treatment two types of osteoclasts could be found in treated rats. One type resembled those found in untreated is littermates and the other those found in normal rats. These data suggest that failure of tooth eruption in ia rats is directly related to the reduction In bone resorption and that alveolar bone resorption is required for tooth eruption.