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PubMed2003

Evaluation of composite restorations in hypomineralised permanent molars: a four year clinical study.

AIM: The objective of this investigation was to evaluate the clinical performance of composite restorations in enamel hypomineralised posterior teeth. METHODS: 52 composite restorations were placed in 52 permanent molars of 46 children, aged 8-10 years. All the teeth were clinically diagnosed as hypomineralised and restorations were placed on two or more surfaces of the teeth, including cusps. All treated teeth had at least 2 sound surfaces, thus excluding defective teeth with total disruption of the crown. The materials used were a hybrid composite and a fourth generation one-bottle adhesive material and manufacturer's instructions were carefully followed. The restorations were initially evaluated 7 days after the treatment and subsequent evaluation was performed at 12, 24, 36, 48 months. Clinical evaluation of the restorations was made according to the criteria of Ryge [1980]. RESULTS: In 6 cases, postoperative complaint was relieved after occlusal re-adjustment at the second appointment, 7 days later. At the end of the 48 months study period, 49 restorations were available for evaluation, all with full retention. Radiographically there was no periapical pathology. Problems were found in colour match in 10, surface appearance in 3 and anatomic form in 4 restorations. Hypersensitivity was recorded in 17 teeth after one week and in 3 teeth one year later. All teeth were sensitivity free after two years and until the end of the study period. CONCLUSIONS: Composite resin restorations using contemporary materials, in certain cases of hypomineralised permanent molars, can be an acceptable restorative procedure with satisfactory long-term results.

Analysis of Variance↗
PubMed2003

[Changes of dentin, dental pulp and periodontium tissue in tail-suspended rats].

OBJECTIVE: To investigate the metabolic changes of calcium and phosphorus in dentin, dental pulp and periodontium in tail-suspended rats, and the functions of TGF-beta 1, c-fos, collagen-I and collagen IV in dentin, dental pulp and periodontium. METHOD: Relative percentage contents of Ca, P in dentin, dental pulp and periodontium were measured with scanning electron microscope and energy spectrum analytical system in 3 groups of rats. The expression of TGF-beta 1, c-fos, collagen-I and collagen IV were also observed. RESULT: In the suspension group, the relative percentage content of Ca declined significantly, while P increased slightly. There were no significant differences of Ca, P in alveolar bone. The expressions of TGF-beta 1, c-fos and collagen-I declined, but the expression of collagen-IV in pulp vessel increased. There were no significant changes of expressions of TGF-beta 1, c-fos, collagen-I and collagen-IV in the vicinity of PDL. After adopting artificial countermeasures, the above expressions restored partly. CONCLUSION: Weightlessness might cause abnormal mineralization in dentin, and 1.5 G artificial countermeasures could eliminate the above changes of mineral metabolism. The poor mineralization of dentin might be associated with the reduced secretion of TGF-beta 1, c-fos and collagen-I in tail-suspended rats.

Animals↗
PubMed1978

[Concerning the reversibility of initial carious lesions in the fissure region (author's transl)].

Using a light microscope, the authors compared longitudinal ground sections of human premolars from a region where the drinking water contains 1,0 p.p.m. of fluorine with the preparations from a region where the drinking water contains 0.35 p.p.m. of fluorine. Under the microscope, "healty" teeth may also show initial carious lesions in the fissure region. These changes are significantly less frequent in premolars which developed under the influence of fluorine. This finding and an age-depending decrease of the initial carious lesions in the fissures militate in favour of the reversibility of these changes.

Adolescent↗
PubMed2004

Radiographic survey of third molar development in relation to chronological age among Japanese juveniles.

The aim of the present study was to establish Japanese reference material on the third molar development of Japanese juveniles for forensic application. Observations were performed on the orthopantomograms of 1282 Japanese patients between the ages of 14.0 and 24.0 years. Demirjian formation stages of the maxillary and mandibular third molars were recorded for chronological evaluation of wisdom teeth and applied for further statistical analysis. Statistically significant differences were noted between the upper and lower jaws and genders. Accordingly, males achieved root developmental grades earlier than females. We assessed the mean ages for all formation grades and predicted the probability that a Japanese juvenile would be older than the relevant ages of 14, 16, and 20 as defined by Japanese Juvenile Law. We determined the likelihood that a Japanese youth is older than the relevant age of 18 as defined by legislation in the United States.

Adolescent↗
PubMed2004

[Mineralization of dental hard tissues].

Tooth is a composite of the three different biological mineralized tissues (dentin, enamel, and cementum) that acquired supreme mechanical properties and function necessary for the mechanical digestion of the food throughout life. The underlining mechanisms of mineralization of each of these three components are unique and different from each other. Here the focus was placed on the mineralization process of dentin and enamel of the teeth of vertebrates.

Amelogenesis↗
PubMed1979

[Changes in microhardness of hard dental tissues of rabbits after internal medication of antibiotics (author's transl)].

Comparative Vickers hardness measurements on hard dental tissues mineralized under normal conditions and under the influence of antibiotic substances showed substance-and dose-dependent variations in quality of superficial enamel and dentine. They were found to correlate with other physicochemical properties (acid solubility) and must be considered as belonging to what is generally referred to as structural anomalies. - Consequently, the administration of antibiotics to babies and young children should be reexamined because of possible late effects.

Animals↗
PubMedDate not supplied

Scanning electron microscopic analysis of dentin in vitamin D-resistant rickets--assessment of mineralization and correlation with clinical findings.

In vitamin D-resistant rickets, the basic dental defect is manifested in dentin. Structural investigations of rachitic dentin by light and scanning electron microscopy have revealed the presence of calcospherites separated by interglobular dentin. This occurs when calcospherites do not fuse. This study investigated the morphology and ultrastructure of rachitic dentin with three different clinical and histologic grades of severity to determine if dentin mineralization can be quantified by calcospherite size and degree of calcospherite fusion. The results showed that a correlation existed between calcospherite size, calcospherite fusion, and the degree of dentin mineralization. The present findings indicate that calcospherite size and calcospherite fusion are valid parameters for assessing and quantifying dentin mineralization. In addition, an SEM grading of severity was established based on these two parameters. The SEM grades correlated directly with the clinical and histologic grades, suggesting that the dental clinical manifestations are a reflection of the underlying morphology of the dentin and the extent of abnormal dentin mineralization.

Dentin↗
PubMed2006

Radiographic appearance of apical closure in apexification: follow-up after 7-13 years.

AIM: This was the radiographic evaluation of 15 maxillary incisors apexification treatment carried out on 7-9 years old patients with periapical pathology due to pulpal necrosis after dental trauma. MATERIALS AND METHODS: The treatment consisted of two phases. The aim of first phase was the formation of a calcified apical barrier through calcium hydroxide medications repeated twice with a three months interval. The aim of the second phase was the obturation of the root canal system once achieved a radiographic evidence of the formation of an apical barrier. The treated teeth were radiographed at six months and then periodically once a year for a period of 7 and 13 years. RESULTS: The radiographic analysis allowed to underline three different kinds of apical formation: a physiological development of the apical portion with a final root length equal to the contralateral tooth; the formation of a cap tissue and an apical development with the final root length slightly shorter than the contralateral tooth; or the formation of different layers of mineralised tissue that aggregate together trough the years. CONCLUSION: Apexification is not a static phenomenon and the apexified area undergoes through the years to a conspicuous readjustment involving bone, apical root tissues and root filling material.

Calcium Hydroxide↗
PubMed1991

Molecular mechanisms in dental hard tissue mineralization.

During the period covered by this issue, over 500 papers were published in the area of biology of dental hard tissues. This review is limited to publications that focus on the organic matrix components believed to be important in the formation of dentin, cementum, and enamel. The advances made in this area for the collagen-based dental hard tissues (dentin and cementum) have been primarily in the isolation and partial characterization of the noncollagenous proteins such as proteoglycans, phosphoproteins, and proteins normally found in bone. These proteins are being studied because of their potential role for directing hydroxyapatite nucleation or crystal growth. The progress made in the enamel field has been primarily in the area of molecular biology. Enamel is quite different physically from dentin and cementum because it is formed from a noncollagenous matrix (mostly amelogenin), which is almost completely removed and replaced with hydroxyapatite. Serum proteins have now been found in all dental hard tissues including enamel. Opinions on the clinical significance of these advances are provided.

Amelogenesis↗
PubMed2006

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.

Ameloblasts↗
PubMedDate not supplied

Molecular determinants during dental morphogenesis and cytodifferentiation: a review.

Craniofacial development provides a number of opportunities to investigate the cellular and molecular biology of morphogenesis, cytodifferentiation, tissue-specific extracellular matrix (ECM) formations, and biomineralization. Regulatory processes associated with mandibular morphogenesis and specifically tooth formation are being investigated by the identification of when and where molecular determinants such as cell adhesion molecules (CAMs), substrate adhesion molecules (SAMs), and tissue-specific structural gene products are expressed during sequential developmental stages. Based upon in vitro organotypic culture studies in serumless, chemically defined medium, instructive and permissive signaling has been found to be required for both mandibular and dental morphogenesis and cytodifferentiation. For example, intrinsic developmental instructions (autocrine and paracrine factors), independent of long-range hormonal or exogenous growth factors, mediate morphogenesis from the initiation of the dental lamina through crown and initial root stages of tooth development. This review summarizes recent results using experimental embryology, organ culture, recombinant DNA technology, and immunocytology to elucidate mechanisms responsive to instructive epithelial-mesenchymal interactions associated with mandibular morphogenesis, tooth positional information, and subsequent tooth crown and initial root development.

Amelogenesis Imperfecta↗
PubMed1976

Matrix vesicle heterogeneity: possible morphogenetic functions for matrix vesicles.

Extracellular membranous matrix vesicles were localized and described using electronmicroscopy during chondrogenesis, osteogenesis, and dentinogenesis. Evidence indicates that matrix vesicles in each of these specific tissue types function to concentrate and transport ions and enzymes which serve as nucleation sites for the mineralization of hydroxylapatite. We have examined different developmental stages of Meckel's cartilage, alveolar bone and epithelial-mesenchymal interactions associated with tooth formation in newborn mice. These ultrastructural studies indicate matrix vesicle heterogeneity. Whereas most matrix vesicles contain alkaline phosphatase activity during cartilage, bone and dentine mineralization, in earlier developmental stages matrix vesicles contain acid phosphatase activities and little, if any, alkaline phosphatase. Tissue type, specific developmental stage, and ultrastructural criteria indicate various "classes" of matrix vesicles. During epithelial-mesenchymal interactions in tooth development, mesenchymal cells (preodontoblasts) appear to be the source of matrix vesicles as indicated by the complementarity between H-2 histocompatibility alloantigen specificity on the cell surface and that of the matrix vesicle outer surface; matrix vesicles are limited by a trilaminar membrane derived from the mesenchymal cells. Some of the vesicles located adjacent to dividing inner enamel epithelial cells contain RNA's as determined by electron microscopic autoradiography in situ, as well as by direct biochemical assays. We postulate that matrix vesicles have many different and important biological functions, one of which may be to mediate developmental information from mesenchyme to epithelia during "instructive" stages of tooth development.

Animals↗
PubMed1991

[Experimental models for study of fluorosis].

In most animal species, acute fluorosis is triggered by the accidental consumption of substances with a high content of fluorine, widely used in pest control. Fluorine normally concentrates in bones and teeth, and forms nearly 0.05% of these structures in mature animals, positively contributing to increase resistance of enamel to caries and favoring mineralization after eruption, a process which increases with age. The present article submits a form of study of fluorosis, stressing due warning as to its harmful effects.

Animals↗
PubMed1991

Morphological study of calcospherites in rat and rabbit incisor dentin.

Calcospherites from incisors of rats and rabbits were studied, by means of secondary and backscattered electron images, using scanning electron microscopy. Part of each incisor specimen was made anorganic to allow observation of the surface of the mineralization front by scanning electron microscopy; the other part was ground on one side for observation by scanning electron microscopy with a backscattered electron image detector. In both species the labial mineralization front was wavy and the image showed fused calcospherites, whereas the lingual mineralization front appeared to consist of a combination of linear and globular forms. In rat labial dentin the calcospherites were large and globular form, but they did not develop in the lingual dentin and were small and oval. The shape and size of rabbit incisor calcospherites varied from the pulp horn to the root apex. There were great differences between rats and rabbits with respect to the size and shape of the calcospherites at the mineralization front. This may be due to species differences and possibly the differing rates of dentinogenesis in rats and rabbits.

Animals↗