Calcification of non-collagenous matrix in human gingiva: a light and electron microscopic study

Amelogenesis imperfecta and unusual gingival hyperplasia

BACKGROUND

Amelogenesis imperfecta (AI) is a group of hereditary conditions that primarily involves the defective formation and/or calcification of enamel. The association of AI with gingival enlargement-like lesions has also been reported.

METHODS

This paper reports a case of a hypoplastic AI associated with unusual generalized gingival hyperplasia.

RESULTS

Histological aspect of the gingival growth was characterized by a dense connective tissue with a mild mononuclear inflammatory infiltrate, calcified bodies, and islands of odontogenic epithelium.

CONCLUSION

The present case represents a very interesting demonstration of the fact that, although rare, AI may be associated with generalized gingival enlargement.

Evidence that cyclosporin A administration induces the formation of new cementum-like islets inside the gingival connective tissue

Two groups of 3 male Sprague-Dawley rats were given orally 30 mg/kg/d of vehicle (control group) or cyclosporin-A (experimental group) solution for 14 wk. The rats were anesthetized, tissues fixed by intracardiac perfusion of fixative solution and jaws dissected, demineralized, processed for Epon inclusion and cut by semi-thin serial sections. Histological examination revealed the presence of several islets located paravascularly inside the gingival connective tissue in the proximity of the root surfaces. The structure of these new cementum-like islets (NCLIs) was either compact and homogeneous or heterogeneous, but identical to that of the adjacent new cementum (NC) deposits. Histomorphometric evaluation indicated that the volume and the external surface of the NCLIs varied from 2354 to 679,497 micron 3 and from 465 to 47,517 micron 2, respectively. These observations (a) suggest that CsA stimulates possibly paravascular progenitor cells which secrete in situ a NC-like material and (b) provides further evidence about the high potential of CsA to induce NC formation.

Bone formation in experimental myositis ossificans. Light and electron microscopy study

The development of ectopic ossification in experimental myositis ossificans of the rabbit thigh was studied. The right hind limb of 25 rabbits was immobilized with the knee in extension. Once a day the limb was passively mobilized for 2-3 minutes. The animals were killed 3, 5, 7, 14, 21, 28 and 35 days after the beginning of the experiment. Specimens for light and electron microscopy were obtained from both hind limbs. Extensive necrosis and fibrosis were observed in the right vastus intermedius muscle during the first week. Proliferation of chondrocytes and osteoblasts with newly formed woven bone and cartilage formation were found in the periosteum within 7 and 14 days after the beginning of the experiment. Intensive enchondral ossification and hard calcified tissue were observed later. It was evident that bone formation in this experimental model started in the periosteum after necrosis of the adjacent skeletal muscle. Therefore the temporal and spatial relationship of traumatic changes in the periosteum and muscle seems important for the development of myositis ossificans.

Autosomal recessive rough hypoplastic amelogenesis imperfecta. A case report with clinical, light microscopic, radiographic, and electron microscopic observations

A case is presented of a 12-year-old Japanese girl with nearly complete lack of enamel in the deciduous and the permanent dentitions, coupled with a gross abnormality in the pattern of eruption. There was no family history of a similar condition. Deciduous molars were extracted, and hyperplastic gingival tissue was resected. On the basis of clinical, radiographic, and microscopic findings, a diagnosis of autosomal recessive rough hypoplastic amelogenesis imperfecta was made. The configuration of the abnormal enamel was examined with scanning and transmission electron microscopy as well as with light microscopy. Prismatic structure was virtually absent, and the scant enamel showed globular protrusions superficially. Two different surface structures were identified as covering parts of the enamel. At the ultrastructural level, calcified bodies located in the gingival tissue appeared to be composed, in part, of a dense enamel-like substance and, in part, of a tissue with features of afibrillar cementum.