Odontoma: retrospective study and confocal laser scanning microscope analysis of 52 cases.

AIM: The aim of this study was to perform a retrospective analysis of 52 cases of odontoma treated at the Department of Dentistry and Surgery, University of Bari, in the period 1971-2005. METHODS: The odontogenic tumors were diagnosed as complex or compound odontoma following histological analysis and clinical radiological examination, and applying the 2005 WHO classification. The data analysis was conducted by considering the following factors: gender, age, site of the lesion, association with impacted teeth, aplasia, presence of supernumerary teeth as well as preoperative diagnosis by panoramic and periapical radiographs. Biopsy tissue samples were conventionally processed for histopathologic paraffin embedding and then were observed by optical microscopy and subsequently by confocal laser scanning microscopy (CLSM) in autofluorescence. RESULTS: Thirty specimens (57.6%) were from females and 22 (42.3%) were from males patients. The patients' age ranged from 5 to 75 years. Fifty-one percent of the specimens were excised from the mandible. In the maxilla, the most common location for odontomas was the anterior region. Most odontomas were associated with impacted teeth and only in one case there was an odontoma instead of a permanent tooth. CONCLUSION: Odontomas are considered hamartomatous malformations whose diagnosis is generally formulated by routinary radiographic examination. The CLSM analysis could help in diagnosis and histopathological analysis showing well-defined follicular area entrapped in hard tissues and pointing out ghost cells, otherwise not identifiable by traditional microscopy.

Complex odontoma: confocal laser scanning microscopy analysis of a case.

Confocal laser scanning microscopy (CLSM) represents a recent acquisition in the study of biological samples stained for fluorescence observation. Particularly, this technique allows a bidimensional investigation of tissues and cells with the possibility to elaborate a three-dimensional model. The aim of this study is the use of this technique, as a complementary and not substitutive application of the histological examination, for the morphological and histopathological analysis in a case of mixed complex-composed odontoma. The analyzed specimen has been surgically removed in the superior frontal region in a 12 year-old boy and submitted to conventional histopathological analysis. The specimen, hematoxylin-eosin stained, has been subsequently submitted to confocal laser scanning microscopic analysis in autofluorescence by using a Nikons C1 system. This analysis has underlined not visible aspects in traditional optical microscopy, such as the mineralization of hard tissues and the morpho-structural organization of the cellular component. The presence of enamel and dentin may be observed in the different phases of odontogenesis with clear fluorescence gradients determined by the different mineralization degrees. Thus, the odontogenetic components appear strongly autofluorescent in the classical follicular configuration. Three-dimensional reconstruction is made possible by the acquisition of serial bidimensional images that are subsequently analysed by using a specific software device. This study shows the confocal laser scanning microscopy versatility in the analysis of odontogenic neoplasms with production of mineralized tissues.

An ultrastructural study of calcifying odontogenic cyst, especially calcified material.

The ultrastructural features of calcification in a case of calcifying odontogenic cyst (COC) were studied. Scanning electron microscopic examination of the inner parts of the cyst wall revealed many short microvilli, and X-ray microanalysis of the high-density masses in the intercellular parts showed prominent calcium peaks, which meant that these masses were calcified materials. On transmission electron microscopic observations, many calcifications exhibited a distinctive ring formation around the periphery of a central core that consisted of an amorphous structure. These calcifications were observed with necrotic remnants of nuclear material and many identifiable mitochondria, thin fibers, and epithelial cells. The cytoplasm of ghost cells consisted of numerous short electron-dense tonofilament bundles. Needle-like structures were shown in the tonofilament bundles. X-ray diffraction analysis showed that the needle-like crystals were hydroxyapatite. It is suggested that calcification in a COC may be related to degenerative mitochondria and tonofilament bundles of ghost cells.

A case report of a compound odontoma causing delayed eruption of a central maxillary incisor: clinical and microscopic evaluation.

A case of a compound odontoma caused delayed eruption of a central incisor in the maxilla is presented with clinical, radiographic, and microscopic findings. The odontoma was surgically removed and microscopic examination showed a lot of crown-like structures in a very irregular form, some of which were fused to each other at their apical parts. Enamel and pre-enamel were totally abnormal, whereas the inside of the pulp chamber tissue did not present any histological sign of functional tissue. The most homogeneous tissue was dentin. The removal of the odontoma was followed by a rapid eruption of the impacted central incisor.

Initiation of ectopic epithelial calcification in a calcifying odontogenic cyst.

Ultrastructural observation was performed on a calcifying odontogenic cyst (COC) associated with an odontoma and arising in the right mandibular region of an 8-year-old Japanese boy. Four types of cells were identified in the epithelial layer of the COC. The basal cells were low columnar in shape and contained some intracellular organelles. They were attached to the neighboring cells with a few desmosomes and resembled inner enamel epithelium of the normal enamel organ. The stellate reticulum-like cells, polygonal in shape, possessed desmosomes and many cytoplasmic projections. Some intracellular organelles and a few bundles of tonofilaments were observed in the cytoplasm. The light oval cells that were pale staining with toluidine blue contained dilated membranous organelles and many relatively evenly distributed tonofilaments. These cells were usually scattered in the vicinity of the focal accumulations of ghost cells, and the cell membrane was discontinuous in parts. The ghost cells contained many bundles of tonofilaments that were 60-240 nm in diameter and arranged in various directions. No intact intracellular organelles were noted in the cytoplasm. They were attached to the neighboring ghost cells with some desmosomes and their cell membrane was discontinuous in parts. A variety of vesicles, 90-450 nm in diameter, were scattered among the tonofilament bundles. Some of these contained needle-like crystals that were considered to be initial calcification sites in ghost cells. These vesicles presented morphological similarities to matrix vesicles, and it is therefore suggested that matrix vesicle-like structures are deeply involved with initiation of calcification of ghost cells in COC.

[Ameloblastic fibrosarcoma: an immunohistochemical and ultrastructural study of the mesenchymal component].

To study the characteristics of the mesenchymal cells of ameloblastic fibrosarcoma (AFS), three cases of AFS were studied immunohistochemically and ultrastructurally. The results showed that the mesenchymal component of AFS consisted predominantly of fibroblastic cells with a small number of undifferentiated cells, a few histiocytes and occasionally myofibroblastic cells under electron microscope. The fibroblastic cells were Vimentin positive only, and myofibroblastic cells were positive for Vimentin, HHF35 and alpha-SMA. The histiocytes were positive both for kp1 and PG-M1, suggesting that these cells were infiltrating cells from peripheral blood rather than histiocytic differentiation of tumor cells. Compared with ameloblastic fibroma, AFS showed much higher PCNA labeling index, suggesting higher proliferation activity of AFS.

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.

Observations on the enamel of odontomas.

The morphological study of odontomas provides an alternative model for observing the formation of dental tissues, since different maturing stages are present simultaneously. Investigations were performed on decalcified samples (using light microscopy and transmission electron microscopy) and on undecalcified samples of complex odontoma enamel (using transmission electron microscopy). Simultaneous presence of prismatic enamel at various maturing stages with different structural characteristics was observed. Such enamel was sometimes associated with layers of ameloblastic cells with characteristics of cells in functional activity. In other sites, the enamel did not present a prismatic structure but it appeared as unstructured material clusters with abundant organic component. It was concluded that the theory according to which an ecto-mesenchymal inductive failure occurs in odontomas is not confirmed. The defect seen at the beginning of the differentiated and anomalous tissue maturation may be related to latest events in the development of the enamel organ. In this regard, it was concluded that such events involve the efficiency of the ameloblasts and the possible alterations in the organic matrix.

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.

Dysplastic enamel in odontoma: a light microscopic, microradiographic and SEM study.

Dysplastic enamel and calcifications at the enamel surface in 7 odontomas were studied, using correlated light microscopy of decalcified and undecalcified material, microradiography and SEM. Much of the dentin in the odontomas was not covered with enamel. When present, the enamel was immature and assumed a prismatic structure. The prisms were irregular distributed and associated with spherical calcifications. The calcifications adhering to the enamel surface or separated from it presented variations in size, morphology, staining reactions and radiodensity. The correlated techniques of light microscopy, microradiography and SEM indicated that all the calcifications adhering to the enamel surface and part of those separated from it may be related to a pathological process of amelogenesis. Most of the calcifications separated from enamel and often formed around nidi of ghost cells, are the result of a dystrophic mineralizing process, definitely distinct from amelogenesis.

Epithelio-mesenchymal morphology in ameloblastic fibro-odontoma: a light and electron microscopic study.

Five cases of ameloblastic fibro-odontoma were examined by light and electron microscopy. The ultrastructure of the epithelio-mesenchymal interface was compared with the morphology of the normally developing tooth germ. It was noted that the ultrastructure of the tumors was identical with the normally developing odontogenic tissues up to but not including the differentiation of mesenchymal cells into tall columnar odontoblasts. The absence of odontoblasts in the ameloblastic fibro-odontomas results in an absence of tubular dentin in place of which a homogeneous collagen-containing material is synthesized. The failure of mesenchymal cells to acquire the morphology of tall columnar odontoblasts probably is due to the absence of the normally occurring induction of the mesenchyme by the odontogenic epithelium.

An ultrastructural study of the calcifications in calcifying odontogenic cysts and odontomas.

The calcifications associated with the epithelium of the calcifying odontogenic cyst and odontoma were studied ultrastructurally and found to be of three types: (1) spherical calcifications which form on ghost cells and which therefore are dystrophic, (2) spherical calcifications which appear to be dysplastic enamel, and (3) irregularly shaped, diffuse calcifications which form on a collagenous matrix and appear to by dysplastic dentin or cementum.