Immunocytochemical characterization of ectopic enamel deposits and cementicles in human teeth

Pérola de esmalte: epidemiologia, morfopatogênese e relevância na clínica odontológica

INTRODUÇÃO: Distúrbios da odontogênese geram anomalias dentárias com relevância diagnóstica e terapêutica. OBJETIVO: O presente artigo teve como objetivos fazer uma revisão sistemática sobre a pérola de esmalte e discutir seu processo formativo, bem como a sua significância na clínica odontológica. MATERIAL E MÉTODO: Três bancos de dados eletrônicos (Pubmed, Cochrane e Biblioteca Virtual em Saúde) foram usados para recuperar artigos científicos dos últimos 30 anos, usando o descritor enamel pearls. RESULTADO: O Brasil ocupa posição de destaque nas publicações temáticas existentes (18%). A etiopatogênese desta anomalia ainda permanece obscura, sendo necessários mais estudos acerca da contribuição de fatores envolvidos com amelogênese ectópica e cementogênese deficiente in situ. Dados epidemiológicos apontam uma frequência variável na população brasileira (0,8 a 8%) e mundial (0,2 a 6,2%), sendo os molares os dentes mais acometidos. Análise morfológica das pérolas de esmalte mostra que esta anomalia de forma e volume pode ser de dois tipos: simples (pérola verdadeira externa ou interna) ou composta (esmalte-dentina ou esmalte-dentina-polpa). É importante o diagnóstico clínico-radiológico diferencial de pérolas de esmalte para permitir o tratamento odontológico adequado, que inclui a ameloplastia como conduta eficaz para minimizar o acúmulo de biofilme oral e a exarcerbação da doença periodontal. CONCLUSÃO: Faz-se necessária a publicação de pesquisas pormenorizadas sobre pérolas de esmalte, a fim de gerar evidências científicas no fazer profissional da Odontologia.

Wound healing following regenerative procedures in furcation degree III defects: histomorphometric outcomes

Degree III furcation involvements were surgically created at four first molars in each of three monkeys. Following 6 weeks of healing, full-thickness flaps were elevated. Following 24% EDTA gel conditioning, the defects were treated with one of the following: (1) enamel matrix proteins (EMD), (2) guided tissue regeneration (GTR) or (3) a combination EMD and GTR. The control defects did not receive any treatment. After 5 months of healing, the animals were sacrificed. Three 8 μm thick histological central sections, 100 μm apart, were used for histomorphometric analysis in six zones of each tooth either within the furcation area or on the pristine external surface of the root. In all specimens, new cementum with inserting collagen fibres was formed. Following GTR or GTR + EMD, cementum was formed up to and including the furcation fornix indicating complete regeneration on the defect periphery. Periodontal ligament fibres were less in all four modalities compared to pristine tissues. In the teeth treated with GTR and GTR + EMD a higher volume of bone and periodontal ligament tissues was observed compared to EMD. After 5 months of healing, regenerated tissues presented quantitative differences from the pristine tissues. In the two modalities where GTR alone or combined with EMD was used, the regenerated tissues differed in quantity from the EMD-treated sites.

Mutual induction of noncollagenous bone proteins at the interface between epithelial cells and fibroblasts from human periodontal ligament

BACKGROUND AND OBJECTIVE

Epithelial-mesenchymal interactions are responsible for cell differentiation during periodontal regeneration. The present study was undertaken to examine the expression of alkaline phosphatase and noncollagenous bone proteins, such as osteopontin, osteocalcin and bone sialoprotein, with respect to interaction between the cells of the epithelial rests of Malassez and fibroblasts from human periodontal ligament.

MATERIAL AND METHODS

Explants of human periodontal ligament tissues produced outgrowths containing both putative epithelial rests of Malassez cells and human periodontal ligament fibroblasts in a modified serum-free medium. Putative epithelial rests of Malassez cells cultured alone, and human periodontal ligament fibroblasts cultured alone, were used as controls. The expression levels of amelogenin were analyzed by in situ hybridization. The expression and distribution of alkaline phosphatase and noncollagenous bone proteins in both cell populations at the interface between putative epithelial rests of Malassez cells and human periodontal ligament fibroblasts were analyzed by immunohistochemistry, in situ hybridization and reverse transcription-polymerase chain reaction.

RESULTS

Amelogenin mRNA was detected at high levels only in putative epithelial rests of Malassez cells at the interface. Alkaline phosphatase and bone sialoprotein mRNAs were detected significantly at the interface between putative epithelial rests of Malassez cells and human periodontal ligament fibroblast cells. In particular, bone sialoprotein and its mRNA were expressed significantly in human periodontal ligament fibroblasts at the interface between putative epithelial rests of Malassez cells and human periodontal ligament fibroblast cells. The expressions of osteopontin and its mRNA were not different between putative epithelial rests of Malassez cells and human periodontal ligament fibroblasts at the interface. Osteocalcin and its mRNA were expressed strongly in putative epithelial rests of Malassez cells at the interface between putative epithelial rests of Malassez cells and human periodontal ligament fibroblasts.

CONCLUSION

These findings indicate that the epithelial-mesenchymal interaction modulates the expression of alkaline phosphatase, osteocalcin and bone sialoprotein in putative epithelial rests of Malassez cells and human periodontal ligament fibroblasts, suggesting that epithelial-mesenchymal interactions play a role in the maintenance of periodontal ligament.

In vitro differentiation of epithelial cells cultured from human periodontal ligament

BACKGROUND AND OBJECTIVE

Alkaline phosphatase and noncollagenous bone proteins are produced prior to cementum formation. While it has been suggested that epithelial rests of Malassez are involved in cementum formation, little is known about the relationship between epithelial rests of Malassez and cementum formation. The purpose of the present study was to determine whether the epithelial rests of Malassez cells cultured from human periodontal ligament can produce alkaline phosphatase and noncollagenous bone proteins, such as osteopontin, osteocalcin and bone sialoprotein.

MATERIAL AND METHODS

An outgrowth of putative epithelial rests of Malassez cells was produced from periodontal ligament explant, and second passage cultures were used in the experiments. Human gingival epithelial cells and periodontal ligament fibroblasts were used as controls. The expression levels of amelogenin were analyzed by immunostaining and in situ hybridization. Furthermore, the expression levels of alkaline phosphatase and noncollagenous bone proteins were assessed by immunostaining and reverse transcription-polymerase chain reaction.

RESULTS

Amelogenin, alkaline phosphatase and osteopontin proteins and their corresponding mRNAs were detected at high levels in putative epithelial rests of Malassez cells. Osteocalcin and bone sialoprotein were not expressed in putative epithelial rests of Malassez cells. Alkaline phosphatase and noncollagenous bone proteins were seen in periodontal ligament fibroblasts, but not in gingival epithelial cells.

CONCLUSION

Our results suggest that putative epithelial rests of Malassez cells cultured alone do not transform into maturing cells to form the cementum, but may play a potential role in the mineralization process.

Progressive, generalized, apical idiopathic root resorption and hypercementosis

BACKGROUND

Root resorption is a multifactorial process that results in loss of tooth structure. The causes of root resorption may vary, leading to several types of resorptions. Some factors have been identified and may be categorized into physiological resorption, local factors, systemic conditions, and idiopathic resorptions. The objective of this report was to present a case of a 17-year-old white female with progressive, generalized, apical idiopathic root resorption followed up for 34 months.

METHODS

Two panoramic radiographs, 14 and 34 months after initial clinical and radiological examinations, showed the rapid progression of apical root resorption. Two molars, teeth #15 and #16, which had to be extracted, and a bone sample from the distal aspect of tooth #15 were processed for histologic analysis.

RESULTS

Two millimeters apical to the cemento-enamel junction, an abrupt increase in the cementum thickness was noted, amounting to 300 and 800 microm in teeth #15 and #16, respectively. The thickening of the cementum layer was due to an accelerated deposition of cellular intrinsic fiber cementum. An unusually high number of mineralization foci were observed in association with acellular extrinsic fiber cementum, and both free and fused cementicles were seen. In contrast to tooth #16, tooth #15 revealed extensive dentin replacement by a bone-like and a cementum-like tissue. Furthermore, ankylosis was demonstrated in tooth #15 and confirmed in the bone sample.

CONCLUSIONS

At present, there is no preventive or therapeutic regimen for the type of root resorption seen in this case report. Treatment usually consists of the extraction of teeth with advanced lesions.

Maxillary sinus augmentation with Bio-Oss particles: a light, scanning, and transmission electron microscopy study in man

Biological interactions occurring at the bone-biomaterial interface are critical for long-term clinical success. Bio-Oss is a deproteinized, sterilized bovine bone that has been extensively used in bone regeneration procedures. The aim of the present study was a comparative light, scanning, and electron microscopy evaluation of the interface between Bio-Oss and bone in specimens retrieved after sinus augmentation procedures. Under light microscopy, most of the particles were surrounded by newly formed bone, while in a few cases, at the interface of some particles it was possible to observe marrow spaces and biological fluids. Under scanning electron microscopy, in most cases, the particle perimeter appeared lined by bone that was tightly adherent to the biomaterial surface. Transmission electron microscopy showed that the bone tissue around the biomaterial showed all the phases of the bone healing process. In some areas, randomly organized collagen fibers were present, while in other areas, newly formed compact bone was present. In the first bone lamella collagen fibers contacting the Bio-Oss surface were oriented at 243.73 +/- 7.12 degrees (mean +/- SD), while in the rest of the lamella they were oriented at 288.05 +/- 4.86 degrees (mean +/- SD) with a statistically significant difference of 44.32 degrees (p < 0.001). In the same areas the intensity of gray value was 172.56 +/- 18.15 (mean +/- SD) near the biomaterial surface and 158.71 +/- 21.95 (mean +/- SD) in the other part of the lamella with an unstatistically significant difference of 13.79 (p = 0.071). At the bone-biomaterial interface there was also an electron-dense layer similar to cement lines. This layer had a variable morphology being, in some areas, a thin line, and in other areas, a thick irregular band. The analyses showed that Bio-Oss particles do not interfere with the normal osseous healing process after sinus lift procedures and promote new bone formation. In conclusion, this study serves as a better understanding of the morphologic characteristics of Bio-Oss and its interaction with the surrounding tissues.

Immunohistochemical characterization of noncollagenous matrix molecules on the alveolar bone surface at the initial principal fiber attachment in rat molars

This study was designed to immunodetect proteoglycans (PGs) and the noncollagenous glycoproteins, bone sialoprotein (BSP) and osteopontin (OPN) on developing alveolar bone surface in rat molars by the indirect immunoperoxidase method, and to discuss the roles of these molecules at the initial principal fiber (PF) attachment. To characterize PGs, antibodies against five species of glycosaminoglycans (GAGs), chondroitin-4-sulfate (C4S), chondroitin-6-sulfate (C6S), unsulfated chondroitin (C0S), dermatan sulfate (DS), and keratan sulfate (KS) were used. Maxillary alveolar bone facing the distal root of the second molar was examined in 20- and 25-day-old male Wistar rats. Routine histological staining was also used. A hematoxylin-stained, fibril-poor layer always appeared on the alveolar bone surface just prior to the initial PF organization. This layer was strongly immunoreactive for C4S, C0S, OPN, and BSP, and weakly for C6S, but not for DS and KS. Then the initial PFs were attached to this layer. When new bone containing Sharpey's fibers covered this layer, it remained as a hematoxylin-stained, fibril-poor layer between Sharpey's fiber-containing and -lacking bone. The layer was consistently immunoreactive for OPN and BSP but had no immunoreactivity for GAGs. The results suggest that the accumulation of C4S-, C0S-, and C6S-carrying PGs, and of BSP and OPN is a primary event at the initial PF attachment, and is involved in the adhesion of PFs and mineralization of the initial attachment layer. The BSP and OPN act to maintain the interface integrity between Sharpey's fiber-containing and Sharpey's fiber-lacking alveolar bone after the PF attachment is established.

Hertwig's epithelial root sheath, enamel matrix proteins, and initiation of cementogenesis in porcine teeth

OBJECTIVES

The aim of this study was to analyze the association between Hertwig's epithelial root sheath (HERS) cells, enamel matrix proteins (EMPs), and cementogenesis.

MATERIAL AND METHODS

Porcine teeth were examined at the beginning of root formation by light and transmission electron microscopy. Colloidal gold immunocytochemistry was used to analyze the protein expression of amelogenin and ameloblastin.

RESULTS

Before and during disintegration of HERS, its cells displayed the cytologic features of protein synthesis and secretion. While some cells assumed an ameloblast-like phenotype, others extended their territory away from the root surface. A collagenous matrix filled the widening intercellular spaces, and tonofilaments and desmosomes were still present in cells featuring the morphologic characteristics of cementoblasts. Labeling for amelogenin was observed but ameloblastin was not immunodetected. Labeling was associated with organic matrix deposits that were sporadically and randomly distributed both along the root surface and away from it among the dissipated epithelial cells.

CONCLUSIONS

These findings suggest that HERS' cells occasionally assume a lingering ameloblastic activity at the beginning of root formation in the pig. While the results do not support the hypothesis of a causal relationship between EMPs and cementogenesis, they lend support to the concept of an epithelial origin of cementoblasts.