Determination of inorganic pyrophosphatase in rat odontoblast layer by a radiochemical method

abstract — The enzyme inorganic pyrophosphatase (PP_iase, EC 3.6.1.1) from the odontoblastic layer of rat incisors has been studied by means of a radiochemical micromethod. The enzyme was incubated with ³²P-pyrophosphate in tris-HCl buffer at 37°C. The reaction was linear with time for at least 45 min, and the pH optimum was found to be 8.8, independent of the amount of pyrophosphate present. Heating the enzyme at 56°C inhibited the enzyme activity rapidly, Mg²⁺ ions activated the enzyme by 15% at an ion concentration of 4 mM, while higher concentrations were inhibitory. Ca²+ ions and PO₄³⁻ ions inhibited the enzyme at all concentrations. F- ions did not affect the PP_iase at concentrations below 8 mM, whereas higher concentrations had an inhibiting effect. Urea was found to inhibit the enzyme at concentrations above 1.5 M, while EDTA was a strong inhibitor at very low concentrations. The characteristics of PP_iase agree well with the properties of the enzyme non-specific alkaline phosphatase (EC 3.1.3.1.) studied earlier.     

A 3-year clinical follow-up study of pulpotomized primary molars treated with the formocresol technique

abstract — The purpose of the present investigation was to evaluate the prognosis of primary molars treated with pulpotomy employing formocresol. The material consisted of 98 primary molars. The study included clinical and radiographic observations 3, 12, 24 and 36 months after treatment. The survival rate at the 3-month follow-up was 91%, whereas the rate was 83%, 78% and 70%– 12, 24 and 36 months respectively after the treatment. The results were computed according to the life table method.     

Effect of thyroxine and growth hormone on dentin production in maxillary incisors in the rat

ABSTRACT – Dentin production and longitudinal growth of maxillary incisors in female rats, age 60–95 d, were determined by the tetracycline technique in hypophysectomized rats after administration of growth hormone and thyroxine during age 75–95 d. Hypophysectomy was performed at age 60 d. Administration of thyroxine resulted in a considerable increase in dentin apposition and longitudinal growth of the tooth. The same effect, but somewhat lower, was registered for growth hormone. Growth hormone and thyroxine administered simultaneously had an additive synergistic effect. Compared with the effect of hypophysectomy and of hormone administration on longitudinal bone growth and cortical bone remodeling the effect on dentin production and longitudinal growth of the maxillary incisors in the same rats is less pronounced and shows a different pattern in reaction, indicating differences in sensitivity for different cell systems and difference in endocrine control.