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Results for “Tooth Calcification”

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PubMed1995

[Scanning electron microscopy of the resorption surface of deciduous teeth].

Based on a study of ten deciduous human teeth, (front teeth and molars) under a Scanning Electron Microscope type Tesla BS 300 we could observe that the differences of the mineralization levels are more striking in the peritubular dentin, then in the intertubular structures. The structural transformation increases by approaching the resorption surface. Near the enamel the resorption surface shows a two-edged demineralization. The mineralized part near the enamel is probably the result of the protecting processes of the human organism.

Dentin↗
PubMed1977

Surface structure of tooth germs from newborn infants: a light and scanning electron microscopical study.

Tooth germs from the mandibles of 5 stillborn infants were examined by scanning electron microscopy and light microscopy in order to investigate the surgace structure at different stages of mineralization. The surface of the completed enamel of the incisal third of the incisors was smooth, indicating that amelogenesis was at an end. The interface relief between ameloblasts and enamel matrix on the remaining part of the incisors, and on the forming cusps, was characterized by numerous deep pits caused by the Tomes' processes of the ameloblasts. When parts of the organic matrix were removed by sodium hypochlorite, the crystals were exposed as needle-shaped structures. Towards the bases of the cusps the pits gragually smoothed out, continuing as a narrow even surface zone corresponding to the first formed aprismatic enamel. In this zone circular holes 1 micronm were encountered which the light microscope studies showed were dentinal tubules passing into the enamel. At the bases of the cusps there was a rather abrupt demarcation toward a surface zone exhibiting countless slender villi. The light microscope observations indicated that these villi represented the first formed dentine after the basement membrane had disappeared.

Amelogenesis↗
PubMed1996

[The effect of the initial level of mineralization of the erupting molars on their caries susceptibility].

A method for predicting caries of permanent molars at the stage of enamel mineralization has been developed. It is based on measuring the electric conductivity of hard dental tissues. A total of 100 children have been examined over time (for 7 years), starting from the age of 5 to 6 when permanent molars are just erupting and after they appear. The erupting molars are characterized by different levels of mineralization which determines tooth resistance or liability to caries. The initial level of mineralization of erupting molars is the earliest and sufficiently objective prognostic criterion which helps start individual preventive measures.

Adolescent↗
PubMed1996

Recombination of epithelial root sheath and dental papilla cells in vitro.

Hertwig's epithelial root sheath (HERS) cells were isolated and recombined with ectomesenchymal cells in vitro utilizing extracellular matrix components as substrate. After 14 days in culture, HERS cells were differentiated and exhibited a stratified organization. These features resembled those observed in vivo as epithelial rests of Malassez. A mineralization process was also present in HERS cells, in which calcium salts were deposited. This mineralization was correlated with the strong immunoexpression of osteopontin by HERS. The results obtained add support to the possible role of HERS in the secretion of hypocalcified material on the root during early cementogenesis.

Animals↗
PubMedDate not supplied

The effects of acid-etching on enamel from different clinical variants of amelogenesis imperfecta: an SEM study.

PURPOSE: Successful bonding of resins to teeth affected by amelogenesis imperfecta (AI) may be highly dependent on how the enamel responds to acid etching. The aim of this study was to determine, using scanning electron microscopy (SEM), the types of etching pattern achieved with 37% phosphoric acid on dental enamel of 5 clinical variants of AI, namely, pitted hypoplastic, smooth hypoplastic, X-linked (male), X-linked (female), and hypomineralized. METHODS: A normal premolar and primary molar from two healthy patients were used as controls. The enamel was scanned before and after acid etching for 1 min. In the normal, control teeth, the three classical etching patterns were produced: type 1, in which the prism cores are preferentially removed; type 2, in which the prism peripheries are removed, and type 3 in which the removal of enamel does not relate to prism structure. RESULTS: In the normal primary molar, patterns of types 2 and 3 were generally produced. In the AI teeth, the effects of acid etching reflected the clinical variant of AI. All three etch patterns were observed in the enamel surrounding the pits in the pitted type of AI and in the bands of normal enamel in the female with X-linked AI, as well as in the hypomineralized variant. In contrast, no typical etch patterns could be detected in the enamel from the male patient with X-linked variant, as well as from the enamel affected by the smooth hypoplastic variant. CONCLUSIONS: The lack of typical etching patterns in these variants may be the result of abnormal prism structure, or the standard etching time and/or acid concentration may be inappropriate for the abnormal enamel. The results of this study may have useful applications in the restoration of teeth affected by AI.

Acid Etching, Dental↗
PubMedDate not supplied

Scanning electron microscopy examination of resorbing enamel surfaces in unexfoliated primary molar teeth.

We examined unexfoliated primary molar teeth by scanning electron microscopy to study the resorbing internal enamel surfaces. They were fixed in a cacodylate buffered glutaraldehyde-formaldehyde mixture, treated with 2 percent sodium hypochlorite, washed, dehydrated with ethanol and air-dried, before sputter-coating with a 40 nm layer of gold. The examination with a Jeol 6100 scanning electron microscope revealed large areas of enamel resorption, characterized by closely adjoining honeycomb-like lacunae (concavities). In higher magnification, lacunae show enamel with various patterns of resorption: whereas in some regions, only the central portions of prisms are removed; in others, the prism sheath regions are seen below the other enamel structures. Also, regions showing a random pattern of resorption are observed. In addition, lacunae showing resorbing enamel prisms in longitudinal and other orientations are also observed. The results of the present study reveal, therefore, that in unexfoliated primary teeth, the odontoclasts first remove the coronal dentin and then reach and resorb large areas of enamel. Furthermore, the various patterns of resorption support the idea that removal of enamel by odontoclasts depends upon the orientation of enamel structures, rather than of the different degrees of mineralization suggesting that enamel structures do not possess different inorganic/organic composition.

Ankylosis↗
PubMed2000

Application of high resolution microfocus X-ray CT for the observation of human tooth.

The calcification degree of extracted human teeth was observed by using high resolution microfocus X-ray CT. As samples, upper and lower first premolars extracted from a 21-year-old female were used. The computed tomograms were produced by high resolution microfocus X-ray CT with a open vacuum X-ray source, rotating sample stage, and image sensor. The distinction between enamel and dentin was very clear, and the shape of the pulp cavity was also clearly identified. The secondary dentin was visible in the circumpulpal dentin. The color map displays showed the heterogeneity of the calcification degree not only in the dentin but also in the enamel. The enamel was divided into three layers according to the calcification degree. High resolution microfocus X-ray CT was very useful for the observation of the internal structure of human teeth without destroying the samples.

Adult↗
PubMed2001

Tablet fluoridation influences the calcification of primary tooth pulp.

This study was conducted to determine the influence of long-term tablet fluoridation on primary pulp calcification by light microscopy. Twenty-four caries-free primary molars (after continuous postpartally initiated 1- to 10-year tablet fluoridation) were compared to 17 primary molars of children without fluoride prophylaxis. Pulp calcification in children with tablet fluoridation was significantly more frequent and more pronounced than in untreated children (p = 0.001). Besides the known pulp stones, the prophylaxis group evidenced a special form of calcification consisting of fibrodentin-like hard tissue not observed in the untreated children. These hard tissue bodies developed "intramurally" on the pulp floor and the inside of the dental roots with an irregular extramural spread into the coronal and radicular pulp by displacement and fibrotization of the pulp tissue. Moreover, some of the teeth had more or less extensive areas of interglobular dentin. The affected teeth were ankylosed in the area of the bi- and trifurcation and on the inside of the roots and were thus infra-occluded. Although the duration of tablet fluoridation has no statistically significant influence on pulp calcification, there is a correlation between extensive pulp calcification, postnatally initiated fluoride prophylaxis and the infraocclusion of primary molars.

Child↗
PubMed1967

Wrinkling of molar crowns: new evidence.

We submit that wrinkling of molar crowns in Primates is a phenomenon of genetically controlled activity of the inner enamel epithelium that is grossly evident soon after initial calcification of the tooth occurs. The amount and pattern of this wrinkling are characteristic of the species before they are evident in the enamel surface itself.

Amelogenesis↗
PubMed2003

Calcification of degenerating tissues in the periodontal ligament during tooth movement.

OBJECTIVE: Calcification of degenerating tissues in the periodontal ligament (PDL) during tooth movement was investigated longitudinally. MATERIALS AND METHODS: Upper first molars of male Wistar rats were moved lingually for 1, 7 and 21 d, following which unfixed undecalcified sections of the lingual PDL (in the pressure zone) were examined histologically, histochemically (autoradiography and electron probe microanalysis). RESULTS: On d 1 of tooth movement, degenerating tissues, together with some calcified particles, were visible in the pressure zone of the lingual PDL. On d 7, substantial calcified aggregations were seen in the degenerating tissues, predominantly situated between the bone and root. This was confirmed by the 45Ca autoradiography. On d 21 of tooth movement, large calcified aggregations were still clearly evident between the bone and root. CONCLUSIONS: This calcification of the degenerating tissues is a self-defense response of the living body to prevent direct contact between alveolar bone and the tooth root during compression of the PDL, so preventing friction between them and the development of ankylosis.

Alveolar Process↗
PubMed1987

Nuclear magnetic resonance imaging of a benign cystic teratoma in the retroperitoneum.

A retroperitoneal teratoma arising from the vicinity of the upper pole of the right kidney in an 18-year-old woman is described. The plain anteroposterior abdominal radiographs showed irregular calcific shadows with tooth-like calcifications within the right upper quadrant of the abdomen. The findings of a primary cystic teratoma in the retroperitoneum examined by computerized tomography and magnetic resonance imaging of the abdomen are presented. Sagittal and coronal magnetic resonance imaging scans were useful to determine the extent of the mass, and to distinguish the mass from adjacent structures and organs.

Adolescent↗
PubMed1990

[Clinical study of ectopic eruption of the permanent first molars].

The purpose of this study was to investigate the etiology and characteristics of the ectopic eruption of first permanent molars. The subjects were 35 cases (27 maxilla and 8 mandible) with ectopically erupted permanent first molars, which were recognized in 24 out-patients (10 boys and 14 girls) visiting Tohoku University, Dental Hospital. The materials used for the analysis were dental casts, X-ray lateral cephalograms and panoramic radiographs, and both materials of the ectopic and normal groups were compared. The results were as follows: 1) There were no significant differences statistically between the mesio-distal crown diameters of the maxillary permanent first molar, central and lateral incisor, and all deciduous teeth in ectopic group and their mean values in Ono's and Otsubo's studies. 2) There were no significant differences as compared to all parts of the size of the dental arch in ectopic sides with those in the normal sides of same individuals at IIA and IIC of Hellman's developmental stage in dentition. 3) When the sizes of the dental arch in the ectopic group were compared with those of the normal group, the former were smaller at the distance between the mid-point and the canine mesial surface (Fig. 1-4), the ridge of the posterior region of the basal arch and most distal point of the primary second molar (Fig. 1-6) at the Hellman's dental age IIA, while the canine distance to the midline (Fig. 1-1), the dental arch perimeter from mid-point to the distal surface of primary second molar (Fig. 1-4+5), and the distance between the canine and primary second molar, div. X (Fig. 1-7) at Hellman's dental age of IIC were significantly smaller than the latter. 4) Regarding the comparison of the value of the changes in dental arch size between the ectopic group and the normal group from Hellman's dental age of IIA to IIC, the distance between the canine and primary second molar, div. X (Fig. 1-7) decreased markedly and the distance between the ridge of the posterior region of the basal arch and the most distal point of the primary second molar (Fig. 1-6) increased. 5) Results of the analysis of X-ray lateral cephalograms showed that the angle of eruption of first molars in the ectopic group was significantly smaller compared with normal group. 6) According to the cluster analysis on the calcification of tooth germ using panoramic radiographs, similarity among all of the samples was lacking in the ectopic group, especially congenital missing of the second molars and second premolars in the ectopic side and the delayed calcification of the ectopically erupted teeth were found in maxilla.

Child↗
PubMed2000

Specialized basement membrane of monkey maturation stage ameloblasts mediates firm ameloblast-enamel association by its partial calcification.

A basement membrane-like structure associated with the maturation stage ameloblasts of the monkey (Macaca fuscata) tooth germ was examined with high resolution electron microscopy. The tissue was prepared either with or without demineralization. This structure was composed of a lamina lucida-like (lamina lucida) and lamina densa-like (lamina densa) structure. The latter was made up of a fine "cord" network, the major constituent of the basement membrane. It was closely associated with the third layer of a 200 nm wide looser cord network. In specimens without demineralization the third layer and a part of the lamina densa were calcified, and it formed the edge of the enamel. This particular area had a higher electron density, and the size, shape, and arrangement of mineral crystals were different from those of the rest of the enamel. Also, mineralization appeared to be proceeding along the cords. These observations indicate that this dense layer is a highly specialized basement membrane which mediates the firm association of maturation stage ameloblasts with the enamel by means of the mineralization of a part of this basement membrane itself which becomes integrated as a part of the enamel. Also, this highly specialized manner of association is favorable with the reported control of the loss of organic substances in the maturing enamel by maturation stage ameloblasts.

Ameloblasts↗