Macroscopic Sectioning of Undecalcified Tissues

An inexpensive laboratory apparatus designed to section undecalcified teeth and bone has been constructed. It consists of an electric motor with a mandrel bearing a carborundum sectioning disk centered within a Plexiglas enclosure. A coolant flows from a reservoir positioned in the upper portion of the Plexiglas enclosure to prevent desiccation or burning of the tissues. Undecalcified tissue can be cut into a series of thin, 0.5-1 mm slices to facilitate studies of pulpal enzymes, tooth morphology and design of dental cavity preparations.     

Mineral content of calcified tissues in cystic fibrosis mice

Although abnormal hard tissue mineralization is a recognized complication of cystic fibrosis (CF), the pathogenesis leading from the defective cystic fibrosis transmembrane conductance regulator (CFTR) protein is poorly understood. We hypothesized that CFTR plays a direct role in the mineralization of bone and teeth and tested the hypothesis using CF mouse models [CFTR(−) mice]. In vivo measurements by dual-emission X-ray absorpitometry (DEXA) indicated that bone mineral density (BMD) was reduced in CF mice as compared to gender-matched littermates. However, no change was evident after correction of BMD for the covariant of body weight. The latter finding was confirmed in isolated femurs and nasal bones by standard dry-ashing and instrumental neutron activation analysis (INAA). INAA of the continuously growing hypsodont incisor teeth from CFTR(−) mice revealed reduced Ca and normal P in the enamel layer—a finding consistent with changes in the deciduous teeth of CF children. Interestingly, enamel fluoride was increased in the CFTR(−) incisors and may associate with abnormal enamel crystallite formation. The iron content of the incisor enamel was reduced, explaining the loss of yellow pigmentation in CFTR(−) incisors. In contrast to the incisors, the mineral content of the slow-growing brachydont molar teeth was not different between CFTR(−) and CFTR(+) mice. It was concluded that CFTR does not play a direct role in the mineralization of bones or brachydont teeth in mice. Functional CFTR is apparently required for normal mineralization of the hypsodont incisors. However, multiple changes in the mineral composition of the CF incisors suggest an indirect role for CFTR, perhaps by maintaining a normal salivary environment for continuous tooth eruption. Preliminary reports published in Pediatric Pulmonology, 14, 253A (1997) and 15, 253A (1998).     

GROWTH LAYER PATTERNS IN TEETH FROM THE FRANCISCANA, PONTOPORIA BLAINVILLEI: DEVELOPING A MODEL FOR PRECISION IN AGE ESTIMATION

A model for estimating age from teeth of the franciscana, Pontoporia blainvillei , was developed using teeth from 72 specimens taken incidentally in fishing nets in Brazil and Uruguay. The goal of the model was to allow for accurate and precise age estimates for a larger sample of specimens. Growthlayer characteristics were selected on the basis of similarities in growth layers among various species of cetaceans, including those whose growth layers have been calibrated for time, and on length groups in the franciscana, which calves seasonally. Growth-layer patterns, including relative size and appearance, in both dentine and cementum did not vary by sex but did vary by the orientation of the tooth when it was sectioned. The model developed proved useful in providing guidelines for consistency in age estimation for biological studies of the larger sample of animals. We recommend the development of this type of model for other species to facilitate standardizing age estimation.