Mandibular growth and tooth eruption after localized x-radiation

The effect of localized x-radiation on the growth of mandibular bone and molar eruption was evaluated by morphometric methods. A dose of 20 Gy of x-radiation was given to the molar zone of growing rats. The animals were then killed in groups at 30 and 60 days postirradiation. Two groups of nonirradiated, age-matched rats were used as controls. Parameters related to molar eruption, mandibular length, and mandibular height were measured on lateral radiographs. The results obtained showed that the values of the biometric parameters were lower in experimental than in control animals. Odontoblastic atrophy, alveolodentary ankylosis, and meager or no root formation were the most conspicuous histologic findings. Osteodentin was found between canaliculary dentin and bone in cases of ankylosis. The morphometric data presented confirm the probability of alterations in mandibular growth and tooth eruption following x-radiation and suggest that this be considered in planning radiotherapy in children.

Effects of gamma radiation on incisor development of the prenatal albino mouse

Fetuses of pregnant albino mouse exposed to 400 rad of gamma-irradiation, on the 12th gestational day, were compared with unirradiated fetuses to asses the radiation effect on developing incisors. Pregnant animals were sacrificed on day 18 post coitum, and their fetuses were decapitated. Heads were routinely prepared, frontally sectioned, and stained with hematoxylin and eosin. Histologic examination demonstrated that the development of the maxillary and mandibular incisors was retarded in all the experimental fetuses and were in early bell stage, whereas those of the control animals were elaborated their matrices. It was concluded that gamma-irradiation interferes with cytodifferentiation of the enamel organ and dental papilla and subsequently inhibits normal odontogenesis.

Ultrastructural study of osteodentin formation induced by irradiation

A single dose of 16,000 rads was delivered to a 1 X 1.5 cm area of the cheek of 2 day old Wistar rats. The lower first molar region was removed 1, 3, 5 and 8 days postirradiation and processed for light and electron microscopy observation. The most distinct structural feature at optical level was osteodentin production in the dental papilla, which began at the level of the initiation of Hertwig's epithelial sheath and continued until the pulpal area was completely filled by osteodentin. At the ultrastructural level, ameloblasts exhibited large lipidic vacuoles and irregular intracytoplasmic secretory granules. Odontoblasts underwent multiple regressive alterations with vacuolization and numerous myelin figures. Pulpal cells exhibited a capacity for odontoblastic differentiation with formation of one or more odontoblastic processes and dentin matrix secretion. Thus, irradiation resulted in stimulation of a great potential for dentin production in these cells.

SDH activity in the developing incisors or irradiated mouse fetuses

Pregnant CD1 Swiss albino mice were irradiated with 400 rads of whole body X-irradiation on the twelfth gestational day. The animals were then sacrificed beginning on day 14 through 20 of gestation by chloroform inhalation. The fetuses were extirpated via laparotomy and decapitated. The severed heads were rapidly frozen and sectioned in a cryostat. The sections were affixed to glass slides and incubated for succinic dehydrogenase activity according to the method of Nachlas et al. (1957) and counterstained in Safranin 0, routinely dehydrated and mounted. Data from observations indicated that siccinic dehydrogenase activity appeared normal in the tissue layers of the developing tooth germ when compared to control animals. When the experimental procedure had invoked damage to the developing tooth, succinic dehydrogenase activity was lessened relative to the degree of damage. Presumably the X-irradiation had affected the cellular maturation process thereby reducing the functional competency of the cells as illustrated by the reduced enzyme activity.

Sensitivy of mouse molar tooth germs to x-ray irradiation in vitro

Molar tooth germs, extirpated from 18-day mouse fetuses were cultured on Millipore filter strips in Falcon organ culture dishes. The tooth germs were exposed to 250 kVcp X-rays at 106 R/min. for a total exposure of 1 600 R. Tissues were harvested on a daily basis for a total period of 12 days and were examined microscopically, utilizing H and E stain. Severe disorganization of the tooth germs was evident within 24 hours of irradiation. The basement membrane became hyalinized; pyknotic nuclei and lysed cells were observed throughout the dental papilla, but mostly in the regions of the presumptive cusps. Although a thin layer of predentin was elaborated by the odontoblasts, the matrix failed to calcify and enamel matrix was not produced. Cultures older than 10 days demonstrated extensive cell death. The entire pulp was reduced to a mass of necrotic cells and the ameloblastic layer consisted of an epithelial remnant covering the cuspal tips.

The effect of irradiation on developing teeth

Although the consequences of ionizing irradiation on adult teeth have been adequately described in the literature, there have been few reports concerning the adverse effects on the developing dentition. A case is presented in which the jaws were irradiated at an early age and it was possible to examine some of the abnormal teeth in detail by using clinical, radiographic, and histologic techniques.