Microradiographic aspects of the growing mandibular body during permanent premolar eruption in the dog.

In order to explore the bony changes in the mandibular body during prefunctional intraosseous eruption of premolars, 18 dogs aged from 8 to 16 wk at the beginning of experimental period, were given two intraperitoneal injections of oxytetracycline (50 mg/kg and 35 mg/kg 2 wk later) and 2 wk later a final injection of Alizarin red S (70 mg/kg). Microradiographic and fluorescent light microscopy studies showed that changes of the alveolar bony crypt walls were influenced by the growing dental germs which they surrounded. The cervical volumetric reduction, which indicates the end of crown formation, induced the apposition of lamellar and then woven bone on the adjacent alveolar walls. Furthermore, with occlusal displacement of the dental crown, the space below the tooth was immediately filled with woven bone trabeculae and chondroid tissue. The same phenomenon was observed at the level of the alveolar base, when the speed of tooth eruption was greater than that of root growth. During premolar development, the changes in the dental germ produces accommodating changes in the adjacent alveolar bone walls, and mandibular transversal growth has the same characteristics as that of a growing diaphysis.