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PubMed1993

Fine structure and elemental analysis of the enamel in the cryptobranchid salamander Megalobatrachus japonicus.

Teeth from Megalobatrachus japonicus were prepared for scanning electron microscopy (SEM) and electron microprobe analyzer (EMPA) to assay the elements of the enamel layer. The enamel layer of each of tooth is thin and the arrangement of the enamel crystals is regular in the Megalobatrachus japonicus. Based on calcium, phosphate and magnesium levels of distribution, the calcification level of the enamel layer differs between the labial and lingual surfaces. Concentrations of iron and fluoride are located in both portions of the enamel layer as well. The presence of trace elements and distribution of calcified levels are related to the mineral formation in the enamel layer and function of the teeth during feeding.

Animals↗
PubMed2003

Permanent incisors traumatized through predecessors: sequelae and possible management.

This report describes the sequence of events following a traumatic dental injury to primary maxillary anterior teeth of a five-year old male during a bicycle accident. The development of the affected teeth during the subsequent ten years was studied from the radiographic records. A detailed account of the clinical and radiographic findings as well as the physio-pathologic changes that have taken place is discussed. In view of the inevitable prognosis of dentitions that sustain traumatic injury during the formative years preventive measures and feasible dental management are proposed. These precautionary measures are aimed to circumvent the sequelae that were experienced in the present case, and avoid predictable complications.

Bicycling↗
PubMed1999

Ultrastructural localization of proteins involved in sea urchin biomineralization.

Three skeletal tissues of the adult echinoid Paracentrotus lividus (the pedicellaria primordium, the test, and the tooth) were immunolabeled with three sera raised against the total mineralization organic matrix and two specific matrix proteins (SM30 and SM50) from the embryo of the echinoid Strongylocentrotus purpuratus. Two conventional chemical fixation protocols and two high-pressure freezing/freeze-substitution protocols were tested. One conventional protocol is recommended for its good preservation of the ultrastructure, and one high-pressure freezing/freeze-substitution protocol is recommended for its good retention of antigenicity. Immunolabeling was obtained in the three adult tissues. It was confined to the active skeleton-forming cells and to the structured organic matrix. The results indicate that the matrix proteins follow the classical routes of secretory protein assembly and export and suggest that SM30 and SM50 are a part of the tridimensional network formed by the organic matrix before the onset of mineralization. They show that the genetic program of part of skeletogenesis is conserved among different calcification models and developmental stages.

Animals↗
PubMed2001

The whereabouts of a morphogen: direct evidence for short- and graded long-range activity of hedgehog signaling peptides.

Sonic Hedgehog (Shh) and Indian Hedgehog (Ihh) are members of the Hedgehog (Hh) family of signaling molecules known to be involved in embryonic patterning and morphogenesis. The Hh proteins undergo an autocatalytic cleavage to yield an N-terminal and a C-terminal peptide, with the signaling capacities confined to the N peptide. Drosophila Hh-N has been shown to act via both short- and long-range signaling. In vertebrates, however, attempts to directly demonstrate Shh (SHH) or Ihh (IHH) proteins at a distance from producing cells have been largely unsuccessful. Furthermore, the fact that the Hh N peptides occur in a cholesterol-modified, membrane-tethered form is not easily reconciled with long-range signaling. This study used optimized immunohistochemistry combined with tissue separation and biochemical analyses in vivo and in vitro to determine the range of action of SHH and IHH in the mouse embryo. In all embryonic structures studied, we detect signaling peptides in producing cells, but we also find that ligands move over considerable distances depending on the tissue. These data provide direct evidence for the presence of Hedgehog signaling peptides in target compartments, suggesting a direct long-range action without a need for secondary mediators. Visualization of Hedgehog proteins in target tissues was achieved only under conditions that allowed proteoglycan/glycosaminoglycan (PG/GAG) preservation. Furthermore, we show that induced changes of the composition of PG/GAG in the tooth alter SHH signaling. These data suggest a crucial role for PG/GAGs in Hedgehog movement.

Animals↗
PubMed1999

Apexification & apexogenesis.

When there is pulpal involvement of permanent teeth with incompletely formed roots, techniques for the induction of apical closure should be completed before endodontic therapy is begun. Apexification is a method of inducing a calcified barrier at the apex of a nonvital tooth with incomplete root formation. Apexogenesis refers to a vital pulp therapy procedure performed to encourage physiological development and formation of the root end.

Adolescent↗
PubMed1983

Clinical considerations in the diagnosis and treatment of intra-alveolar root fractures.

Clinical and radiographic data collected from the 14 cases of intra-alveolar root-fractures, with follow-ups of one to 25 years, complement the findings of other investigators in that the prognosis of the endodontium is extremely favorable. A survey of reports indicate that 75% to 80% of the pulps in intra-alveolar root fractures recover with no need of any endodontic therapy. Furthermore, pulpal pain is seldom encountered. Although the electric pulp tester is considered an important diagnostic tool, it does have limitations. The significance of the negative response is questionable, especially in young, undeveloped teeth with open apexes. The failure to respond to the tester may be attributed to a high electrical impedance. As nociceptor nerve fibers are last to develop, failure to respond to the tester in young teeth may give a false signal of pulp necrosis. Traumatized vital teeth often give an initial negative response, as does a tooth with rapid dentin deposition. Fracture detection can be increased by taking X rays from more than one angle. Radiolucent areas occur in the region of the root fracture more readily than in the periapical region, in a ratio of 7 to 1. Variations in angulations can give false impressions of complete dentinal union and complete or incomplete calcification of the pulpal space and an illusion of a comminuted fracture. The latter seldom occur in intra-alveolar root fractures. Furthermore, the apparent obliteration of the canal and pulp chamber, as seen on the radiograph, does not imply total obliteration with calcific tissue. The root canals are most often patent and negotiable.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Pulp↗
PubMed2005

Ammonium hexafluorosilicate increased acid resistance of bovine enamel and dentine.

Although diamine silver fluoride (AgF: (NH3)2AgF) stains teeth black, it is known as a very effective agent to prevent the dental caries progress. In order to find another fluoride that has a similar anticariogenic effect without changing tooth color, we prepared ammonium hexafluorosilicate (SiF: (NH4)2SiF6), in which the silver of AgF is replaced with silicon. In this study, the anticariogenic effect of SiF was evaluated using bovine teeth. Fluoride solutions, SiF, AgF, acidulated phosphate fluoride (APF), and sodium fluoride (NaF), were applied to bovine enamel and dentine blocks, and the depth of demineralization was measured after exposure to a demineralizing solution for 24 h. Also, fluoride was applied to a simulated dentine caries specimen to evaluate the caries progress-preventing ability. For the dentine specimens, mineral loss (Delta Z) was also measured with microradiography. We found that SiF treated enamel showed better acid resistance than specimens treated with NaF or APF. AgF treated enamel also showed similar acid resistance, but was stained black. SiF and AgF treated caries-affected dentine showed reduced demineralization when exposed to a demineralization solution for 24 h. Mineral loss (Delta Z) was reduced to 85% and 75%, respectively. Although the acid resistance of the SiF treated teeth was inferior to that of the AgF treated teeth, we consider that SiF has good potential as anticariogenic agent, since it increased acid resistance without changing tooth color.

Acids↗
PubMed2004

Combined endodontic and surgical treatment of a three-rooted maxillary first premolar.

A case is reported in which endodontic treatment of a maxillary first premolar was complicated by the fact that the tooth had three roots. One of the roots was completely calcified and therefore could not be negotiated with endodontic files. There was a large periapical lesion associated with the tooth and this was surgically removed. During the surgical procedure a retrograde cavity was prepared on the calcified root using ultrasonic instruments and this was filled using Super EBA cement. Twelve months later the tooth was asymptomatic and the periapical tissues had completely healed.

Aged↗
PubMed2003

Coronal pulp size in molars: a study of bitewing radiographs.

AIM: To: (i) study coronal pulp dimensions in human first molar teeth; (ii) investigate the effects of restorations on pulp size; (iii) determine differences in dimensions between teeth of Mongoloid patients and teeth of other ethnic groups; and (iv) record the presence of pulp stones. METHODOLOGY: Bitewing radiographs of 121 subjects (mean age, 20.9 years) were taken under standardized conditions. The films were digitally scanned and nine measurements were made from the image of each first molar. The data were analysed in terms of presence or absence of restorations and in terms of racial group. Differences were examined using Student's t-test, Pearson correlations and Levene's test. RESULTS: A total of 445 teeth were analysed. Large crowns were correlated to large pulps. Teeth restored with occlusal and proximal restorations had significantly smaller pulps (P = 0.044 and 0.004, respectively), but no difference was found in pulp area in the clinical crown between the restoration types. Mongoloid crowns were shorter and more bulbous. Pulp areas of maxillary molars and pulp widths at the cervix of mandibular molars were significantly larger in Mongoloids. The pulp area in the clinical crown correlated to pulp horn height for Mongoloids and others and for maxillary and mandibular teeth. No differences were found between the heights of pulp horns in the Mongoloid and other teeth. Four of the pulp measurements demonstrated sexual dimorphism. Stones were present in almost 10% of the subjects, representing 4% of the tooth pulps examined. CONCLUSION: Even teeth with shallow occlusal restorations had reduced pulp spaces. There were significant differences in pulp and crown dimensions between the teeth of Mongoloid patients and those of other patients.

Adolescent↗
PubMed2003

Tissue reaction to orthodontic tooth movement in different bone turnover conditions.

OBJECTIVES: To study the tissue reaction to orthodontic load in normal, high, and low bone turnover states. DESIGN: 'Split mouth' design performing orthodontic tooth movement in 52, 6-month-old male rats with: normal (n = 19), high (n = 16), and low bone turnover (n = 17), the latter two being obtained by induction of hyperthyroidism and hypothyroidism, respectively. Performed at the Department of Orthodontics at Aarhus University. EXPERIMENTAL VARIABLE: The upper left first molar was moved for 21 days. Bone markers were administered 7 and 2 days before killing. Histological sections were cut at the coronal and apical levels. OUTCOME MEASURE: Alveolar socket area, periodontal ligament width, the relative extension of alveolar wall with erosion surfaces, and the mineralizing surfaces were measured and compared in the three groups. RESULTS: Alveolar socket, periodontal ligament width, and erosion surface were larger on the treated than on the control side in the three groups. The normal and hypothyroid groups showed a wider periodontal ligament at the bucco-distal site at the coronal level, while the hyperthyroid group showed a widening which was not spatially oriented. The normal and hyperthyroid groups showed higher erosion at the corono-mesial site. The mineralizing surfaces were larger on the treated than on the control side in the normal and hypothyroid groups, but not in the hyperthyroid group. CONCLUSION: In the hyperthyroid group, the widening of the periodontal ligament was not spatially oriented and the increased erosion was not accompanied by increased formation, as observed in the normal and hypothyroid groups.

Alveolar Process↗
PubMed2006

[A histological innovative study of Balb/c mouse tooth germ transplanted to nude mouse in vivo].

PURPOSE: To observed the changes of the developed mouse's dental germs after transplanting into nude mouse and find some theoretical foundation for establishing an innovative experimental model. METHODS: Eight tooth germs from four 5th day postnatal Balb/c mice were transplanted to the back muscles of the adult nude mice. At seventh and fourteenth day after grafting, the germs were collected, fixed, demineralized, dehydrated, and embedded in wax. Serial sections of 5 microm thick were made following the routine methods, stained with haematoxylin-eosin dying solution, and observed under a light microscope. The mandibular first molars were taken out from the 12th and 19th day postnatal mouse. Serial sections of 5 microm thick were made following the routine methods, then compared with the germs after graft. RESULTS: All implantations were located in the superficial muscles with abundant capillary vessels. The dental germs could further developed after grafting under the microscope, but slower than dental germs self-development. The layer of dentin was thin, plenty of dentin with disorganized dentin tubule formed after grafting. Although the location of Hertwig's epithelial root sheath hardly moved, the roots developed further. The floor of pulp chamber could form and the pulp chambers were shrinking. The degree of calcification in the area of root increased very clearly. The inflammatory reaction was found at 7th day while hardly noted at 14th day after grafting. CONCLUSIONS: It suggests that late development of mouse tooth germs could further develop after heterotopic transplantation within the superficial muscles of the nude mouse. This model is useful for study of tooth root development in short time.

Animals↗
PubMed2004

Dentin dysplasia type I: report of atypical cases in the permanent and mixed dentitions.

Dentin dysplasia type I is a rare hereditary disturbance of dentin formation characterized clinically by nearly normal appearing crowns and severe hypermobility of teeth. Radiographic analysis shows obliteration of all pulp chambers, short, blunted, and malformed roots, and periapical radiolucencies of noncarious teeth. This paper presents 2 cases demonstrating both classic and atypical features of type I dentin dysplasia in the mixed and permanent dentitions. The clinical, radiographic, and histopathologic\findings of this condition and treatment are described.

Adolescent↗

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