Postnatal Development of the Rat Palate

¹ Department of Anatomy, School of Medicine, Department of Orthodontics, School of Dentistry, University of Southern California, Los Angeles, California

The postnatal development of the rat palate was studied and correlated with the development and eruption of the maxillary first molar teeth. Heads of rats, ranging in age from newborn to adult, were embedded in nitrocellulose and sectioned coronally through the maxillary and mandibular first molar teeth.

Epiphyseal-like endochondral bone formation was active in varying degrees in the midpalatal suture from birth until the 20th day.

As the palate grew in width, there was progressive decrease in height of the palatal vault. The middle third of the palate assumed a more inferior position in relation to the lateral thirds.

Growth in width and thickness of the palate was most rapid between birth and 5 days, and between 15 and 20 days. Growth in width and thickness of the palate was slowest between 10 days and 15 days, at which time the first molar teeth underwent initial active eruption.

Growth in width of the palate ceased by the 20th day, but osteoblastic evidence of growth in thickness remained at 35 days.

While maxillary first molar teeth were in their bony crypts, their occlusal surfaces were oriented downward or slightly medially. On eruption into the oral cavity, the occlusal surfaces faced in a slightly lateral direction.

A complete bridge of hyaline cartilage persisted across the midpalatal suture of the adult rat.