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  • Title: Dental enamel in relation to ionized calcium and parathyroid hormone. Studies of human primary teeth and rat maxillary incisors.
    Author: Ranggård L.
    Journal: Swed Dent J Suppl; 1994; 101():1-50. PubMed ID: 7886618.
    Abstract:
    The aims of this thesis were to evaluate the role of lowered calcium values in blood on enamel formation and mineralization, and further to analyze whether the calcium regulating parathyroid hormone (PTH) would have any effects on the forming and mineralizing enamel. DENTAL ENAMEL AND IONIZED CALCIUM: Human primary teeth from two groups of infants were clinically and histologically examined. One group (n = 25) was born with optimal perinatal conditions. The infants had low, but not hypocalcemic values on day 1 when compared with days 3 and 5 postpartum. The second group of infants (n = 11) was subjected to blood exchange transfusion on the first few days postpartum. All infants developed very low values of blood ionized calcium due to the treatment, and the infants had a mean of three hypocalcemic days. Enamel aberrations were seen in both groups, but only four infants had multiple enamel aberrations located at levels corresponding to the enamel development at the time of the birth. Low values of blood ionized calcium alone were not associated with enamel aberrations, as the aberrations were only seen in infants subjected to more than three blood exchange transfusions. The neonatal line was present in all teeth investigated, thin lines dominated, and the widths were not dependent on the levels of blood ionized calcium during the first few days after birth. Rats were also used to investigate whether the maxillary incisor enamel would be affected during a diet-induced hypocalcemic state. Of ten experimental rats, nine had normal enamel, indicating that hypocalcemia in rats does not generally affect the enamel. DENTAL ENAMEL AND PARATHYROID HORMONE: Rats was used in a study where they were subjected to daily injections of PTH. Three different doses were used and the experimental periods were 7 and 14 days. In a pilot part, enamel aberrations were seen but not in the main study performed later. The main difference in experimental design between the pilot and the main part of the study was the use of hard tissue marker, oxytetracycline, at start of the pilot part. For this reason, a separate study was performed to evaluate the use of oxytetracycline in hard tissue research. The results clearly demonstrated that oxytetracycline itself induces enamel aberrations and so it was not used in the main study of parathyroid hormone. As no enamel aberrations were seen in the main part, it was concluded that the doses of PTH used do not seem to affect enamel formation and mineralization.
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