Immature complex odontoma: a light and electron microscopic study with reference to eosinophilic material and epithelio-mesenchymal interaction

Generalized gingival enlargement due to accumulation of amyloid-like material

Hyaline or amyloid-like substances may be seen in several oral lesions. Some of these originate from epithelial cells and some from connective tissue components. In this study, amyloid-like material causing gingival enlargement in three patients, with eyelid involvement in two, was examined using histochemistry, immunohistochemistry and electron microscopy. These accumulations did not share the classical features of amyloid such as green birefringence under polarized light after Congo red staining. Our findings suggest that epithelial degeneration plays an important role in the pathogenesis of these amyloid-like accumulations. These substances may be the result of defective amyloidogenesis and our cases may represent an oral counterpart of ligneous conjunctivitis or colloid milium of the skin.

Experimental odontomas in osteopetrotic op/op rats

Osteopetrosis is an autosomal recessive disease in several mammalian species. Osteopetrotic op/op rats suffer from complete failure of tooth eruption related to reduced bone resorption. In our earlier studies, op/op rats grafted with bone marrow cells 3 days after birth were cured of the disease and their molar eruption was restored. However, the incisors failed to erupt and their proliferating ends were distorted, forming odontomas. The purpose of the present investigation was to study the odontogenic tissues in the odontomas, using the correlated techniques of radiography and microradiography of undecalcified material, together with histology of decalcified material and scanning electron microscopy.

Mixed odontogenic tumors: an analysis of 23 new cases

The ameloblastic fibroma, ameloblastic fibrodentinoma, and ameloblastic fibro-odontoma are mixed odontogenic tumors that are considered to arise from both epithelial and mesenchymal elements of the tooth germ. This article presents the clinical and histopathologic characteristics of 23 new cases. The patients' ages ranged from 3 to 19 years (median 9). Most tumors were asymptomatic and were associated with an unerupted tooth or teeth. All patients were treated with simple enucleation of the tumor. We found that histologically these lesions comprise a spectrum. Some were probably benign odontogenic tumors (neoplasms) and others were odontomas undergoing maturation (hamartomas); however, in any given case we were, on histologic grounds, unable to differentiate the two. The majority, if not all, of our cases were nonaggressive with little or no tendency to recur, whereas some reported cases have exhibited local aggressiveness and recurrence, suggestive of neoplasia. In our opinion, it is clinically important to distinguish the mixed odontogenic tumors from ameloblastoma since the mixed tumors, found mostly in children, are relatively benign when compared to ameloblastoma, which is found in all age groups (usually adults). The usually innocuous behavior of these lesions does not justify aggressive treatment initially, and simple enucleation should be appropriate in most cases.

Epithelial odontogenic tumours in domestic animals

Epithelial odontogenic tumours are uncommon, poorly understood and often difficult to diagnose, oral neoplasms. Dental organ pre-ameloblasts and basal lamina induce development of mesenchymal cells into odontoblasts, which produce dentin and induce pre-ameloblasts to mature into secretory ameloblasts. These reciprocal sequential inductive interactions between dental epithelium and mesenchyme form the basis for classifying epithelial odontogenic tumours. There are three tumours classified as non-inductive: ameloblastoma characterized by cords and islands of stellate reticulum with peripheral palisades of polarized columnar cells, adenomatoid ameloblastoma which has acini, rosettes and ducts of polarized columnar cells and stellate reticulum and calcifying epithelial odontogenic tumour which contains foci of Congo-red-positive material surrounded by pleomorphic polygonal epithelial cells. There are five tumours in which induction of mesenchymal tissue is evident: ameloblastic fibroma with characteristics of ameloblastoma plus proliferation of closely associated pulp-like mesenchyme; dentinoma consisting of masses of dentin, often with minimal cellular component; ameloblastic odontoma which contains palisaded epithelium and stellate reticulum as in ameloblastoma, as well as foci of dentin and/or enamel; complex odontoma which is a disorderly array of dentin, enamel, ameloblastic epithelium and odontoblasts; and compound odontoma containing denticles with well-organized tooth morphology. This paper reviews the embryogenesis of teeth and describes six types of epithelial odontogenic tumours in 13 animals. The literature concerning these tumours in nearly 250 animals is reviewed. The most commonly reported tumour is ameloblastoma and the species in which all types are most commonly reported is the dog.

Ameloblastic fibroma of the mandible

A case of an ameloblastic fibroma in the mandible is presented. The ameloblastic fibroma is a benign neoplasm belonging to the group of mixed odontogenic tumours. Enucleation is the treatment of choice. Recurrence of the tumour is very rare, but follow up is necessary. Fewer than 75 cases are described in the literature. An additional case is presented with radiographic signs of calcification which could not be identified on histopathological examination.

Ghost cells in complex odontoma: a light microscopic and SEM study

Ghost cells in complex odontoma were studied by light microscopic and scanning electron microscopic examination of decalcified sections. They were found at different locations in odontomas: next to tubular dentin, at the site where enamel would be expected; adjacent to remnants of enamel matrix or surrounded by enamel matrix; within granular calcified masses in contact with bone or tubular dentin; in contact with ameloblasts or adjacent to small rests of odontogenic epithelium. They were either isolated or arranged in groups. Their cytoplasm presented a fibrillar component and a lack of keratohyaline. In a complex odontoma, ghost cell keratinization occurs as a result of metaplastic transformation. The calcifying process in these cells was found to be a passive one, with the cells becoming gradually entrapped within the calcified material--bone, osteoid, dentin, dystrophic osteodentin, or dystrophic granular or lamellar types of calcification. Complex odontomas contain both normal and metaplastic odontogenic epithelial cells, which may have lost their developmental and inductive properties.

An ultrastructural study of cytodifferentiation in the developing human root-tip

Transmission electron microscopy showed that in growing human teeth, the root sheath consisted of inner and outer epithelial cells. The inner epithelial cells formed a basal lamina associated filamentous layer which increased in density in coronal direction. Extensions of developing odontoblasts were in contact with the basal lamina. Direct contact with the epithelial plasmalemma was not observed. The odontoblasts obtained their fully-developed cylindrical appearance after making contact with the basal lamina of the inner epithelial cells. But, they possessed already abundant RER before these contacts were present, indicating that the differentiation of dental papillary cells into collagen-producing cells did not require heterotypic epithelio-mesenchymal contacts. After deposition of dentine, the odontoblast processes were withdrawn from the epithelium and the outer layer of root dentine. Differentiation of cementoblasts was observed in the dental follicle in which mesenchymal cells develop into RER-containing cells, migrating through apical root-sheath fenestrations to their final position between the continuous root sheath and outer dentinal layer. The findings suggest that all differentiation steps of odontogenic epithelium and odontogenic papillary and follicular mesenchyme proceed without actual contact between epithelium and mesenchyme.

Ameloblastic fibro-odontome. Report of a case, with ultrastructural study

An ameloblastic fibro-odontome of the mandible in an 11-year-old female is reported. The clinical, radiological, histological and electron microscopic findings are presented and compared to similar cases reported in the literature. Histogenetic features as well as differential diagnostic aspects of the ameloblastic fibro-odontome are discussed.