Daniel A. Collins

Growth and transformation of the mandibular joint in the rat II. Hypophysectomized female rats

Abstract The mandibular joint was studied in 79 hypophysectomized female rats at postoperative intervals ranging from 4 to 645 days. The transformations occurring following hypophysectomy are similar to those occurring in aging rats. The changes occur, however, very much earlier in the hypophysectomized rat; chondrogenesis is considerably slowed within four days after the operation. The ossification of the mandible of the hypophysectomized rat by twenty-eight days after operation is as advanced as in a 258-day-old normal rat. As in the normal rat some uncalcified cartilage remains in the condyle for long periods. The persistence of this tissue confers upon this joint the continued capacity for growth and remodeling.

Changes in oral structures of the dog persisting after chronic overdoses of vitamin D.

Abstract Young dogs receiving daily excessive doses of vitamin D 2 and D 3 for a five-month period manifested profound pathologic changes, which included distorted and deformed roots, pathologic calcifications of connective tissues of the paradentium, hypercementosis, pulp stone formation, and advanced paradentosis. The changes persisted following a recovery period of similar duration. No evidence of healing or repair could be demonstrated. The warnings of other investigators regarding the danger of administering chronic excessive doses of vitamin D are further emphasized.

The effects of a single massive dose of vitamin D2 (D-stoss therapy) on oral and other tissues of young dogs

A DECADE ago European clinicians introduced the vitamin D-Stoss (shock) technique for the prevention of rickets in infants.6 This treatment consisted of the administration of large single doses, of l/s million international units or more, of vitamin D. Since the introduction of this method, large single doses of vitamin D,* or D,t have been employed in this country a1so.18, 22 Administration of as high as 11h2 million international units daily to human beings as a treatment for refractory rickets has been tried.l Warnings have been expressed2’ 9, 10, 12, 13, 22 against too much enthusiasm in biologic therapy because of marked roentgenographic and histologic changes in dental and paradental structures of dogs as the result of overdoses of vitamin D. Complete knowledge on the storage and destruction of excessive amounts of vitamin D is not available as yet; studies along these lines have been conducted in experimental animals** I3 and in human beings.14 Assay of the various body tissues of dogs, sacrificed three days after a large single dose, accounted for less than 10 per cent of the original massive dose.ll Caution was advised against the acceptance of the vitamin D-Stoss therapy for rickets or its prevention until more is known about the possible damaging effects, The hypercalcemia which results from hyperparathyroidism and that from the toxic effect of overdosage of vitamin D are of different physiologic 0rigins.l” The former is from a withdrawal of calcium from the body stores and the latter from an increased absorption from the ihtestines or diminished loss through the feces. Deposition of minerals in bone, dentine, and soft tissue has been observed following the hypercalcemic state of both hyperparathyroidism and hypervitaminosis D.15 Pathologic calcifications have been demonstrated in dogs on the surfaces of bone trabeculae, and tooth roots; connective tissue, as for instance Sharpey’s fibers, and pulp tissue showed amorphous highly calcified depositions.2 Small malformed teeth were also observed in these animals. The establishment of the maximum nontoxic dose of vitamin D is a difficult task, as various species and even individual animals of the same species differ in their tolerance of overdosage of vitamin D. In addition, the vitamin D products used by investigators have varied as to source and method of prepara-

Growth and transformation of the mandibular joint in the rat. IV. The effects of thyroidectomy at birth

Abstract The influence of thyroidectomy at birth on the growth and transformation of the mandibular condyle was studied histologically. The cartilage of the condylar head remained wide for long periods, as in young animals. However, the histologic characteristics of this condyle were not those of youth; the chondrocytes were not arranged in orderly columns. A distortion of the head of the condyle occurred, and consisted especially in a disproportionately great breadth and marked flattening. The bone of the condylar head and neck was denser than in normal animals of corresponding ages. Later, by 105 days of age, the reduction in width of the cartilage and the dense bony tissue resulted in a histologic structure of the condylar head and neck which approached that of the control of the same age. Thus, at this time the mandibular condyle appeared slowly to be gaining the structure characteristic of the normal rat. The bone age in these animals, as determined by roentgenographic analysis of representative skeletal structures 4 was 18 days. The long bones which were examined histologically (tibia, metacarpal, and caudal vertebrae) showed a development which confirmed this age. In sharp contrast, however, at none of the ages studied did the structure of the mandibular condyle correspond to that of a normal animal as young as 18 days.