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At least 1,261 records · Page 70Linked to original sources
PubMed1998

Innervation of the periodontal ligament in the alligatorid Caiman crocodilius.

The mode of development and structure of crocodilian teeth and periodontium parallels that of mammals, but the teeth are continuously replaced throughout the lifetime of those animals. In this report, the innervation and fibres of the crocodilian periodontal ligament were examined using histology, immunohistochemistry for S-100 protein and transmission electron microscopy. Crocodilian periodontal ligaments had the following characteristics: (1) horizontal fibres, which connect the alveolar bone to the root cementum and (2) longitudinal fibres, which ran parallel to the tooth axis, with nerves and blood vessels in the middle layer of the ligament. The apex of root and tooth germs were both embedded in thick circular fibres. S-100 protein was detected in neural elements including terminal portions which were densely distributed in the periodontal ligament and dental follicle. The S-100 positive neural elements formed a periodontal plexus. We found two types of nerve endings; free endings and simple encapsulated corpuscles as described in mammals. The presence of such nerve endings in caiman suggests that these teeth, in addition to having a biting function, may also act as highly sensitive sensory organs.

Alligators and Crocodiles↗
PubMed2006

Developmental movements of the inner enamel epithelium as derived from micromorphological features.

It was the purpose of this article to analyze the (micro) morphological structure of enamel at different stages of development in order to deduce movement patterns of ameloblasts during formation of the human dental primordium. Developing enamel and overlying ameloblasts were dried and fractured for scanning electron microscopy (SEM) and sectioned for transmission electron microscopy (TEM). Specimens of human permanent enamel were either fractured and/or ground and etched to visualize the enamel rods. All specimens were viewed by SEM. Moreover, three-dimensional reconstructions were made from serial ground sections of enamel blocks to follow the enamel rods for a longer distance. In addition, the outline of the dentino-enamel junction was analyzed under the SEM after removal (using nitric acid) of the enamel cap, and in serial histological sections. Two basic movements of the inner enamel epithelium can be derived from the micromorphological features: (i) the scalloped dentino-enamel junction may be a consequence of a bulged inner enamel epithelium owing to initial spatial impediment; and (ii) the undulating path of the enamel rods may be a consequence of unequal growth of the cells in the cervical loop.

Acid Etching, Dental↗
PubMed2006

Expression of Pit2 sodium-phosphate cotransporter during murine odontogenesis is developmentally regulated.

Different sodium-dependent inorganic phosphate (P(i)) uptake mechanisms play a major role in cellular P(i) homeostasis. The function and detailed distribution patterns of the type III Na(+)-phosphate cotransporter, PiT-2, in different organs during development are still largely unknown. We therefore examined the temporospatial expression patterns of Pit2 during murine odontogenesis. Odontoblasts were always devoid of Pit2 expression, whereas a transient, but strong, expression was detected in young secretory ameloblasts. However, the stratum intermedium and, later on, the papillary layer and cells of the subodontoblastic layer, exhibited high levels of Pit2 mRNA, which increased gradually as the tooth matured. Hormonal treatment or P(i) starvation of tooth germs in vitro did not alter Pit2 levels or patterns of expression, indicating mechanisms of regulation different from those of PiT-1 or other cell types. PiT-2 also functions as a retroviral receptor, and functional membrane-localized protein was confirmed throughout the dental papilla/pulp by demonstrating cellular permissiveness to infection by a gammaretrovirus that uses PiT-2 as a receptor. The distinct pattern of Pit2 expression during odontogenesis suggests that its P(i)-transporter function may be important for homeostasis of dental cells and not specifically for mineralization of the dental extracellular matrices. The expression of viral receptors in enamel-forming cells and the dental pulp may be of pathological significance.

Ameloblasts↗
PubMed1989

Hertwig's epithelial root sheath differentiation and initial cementum and bone formation during long-term organ culture of mouse mandibular first molars using serumless, chemically-defined medium.

Studies were designed to test the hypothesis that Hertwig's epithelial root sheath (HERS) synthesizes and secretes enamel-related proteins that participate in the process of acellular cementum formation. Our experimental strategy was to examine sequential root development of the mouse mandibular first molar in vivo and in long-term organ culture in vitro using serumless, chemically-defined medium. Using anti-amelogenin, anti-enamelin and anti-peptide antibodies, enamel-related antigens were localized within intermediate cementum during HERS differentiation and root formation in vivo. Cap stage molars maintained for periods of up to 31 days in organ culture expressed morphogenesis and cytodifferentiation as identified by tooth crown and initial root, cementum and bone formation. Metabolically-labeled HERS products were analyzed by immunodetection using enamel-related antibodies and one- and two-dimensional SDS gel electrophoresis. A 72 kDa and 26 kDa polypeptide were identified in forming mouse cementum. Both of these root putative cementum proteins yield similar (identical) amino acid compositions; however, both proteins differed from the compositions of either mouse crown enamelin or amelogenin proteins. This approach provides a new and novel in vitro model towards understanding HERS differentiation and functions related to root and bone formation. The data support the hypothesis that HERS cells synthesize polypeptides related to but also different from canonical crown enamel proteins.

Animals↗
PubMed2005

The effect of Emdogain on ectopic bone formation in tubes of rat demineralized dentin matrix.

BACKGROUND: Emdogain (EMD) is made from enamel matrix proteins (EMPs) from the tooth germ of swine and propylene glycol alginate (PGA) as a matrix. The function of EMD is known to differentiate cells of the dental follicle into cementoblasts. However, little is known about the effect of EMD on mesenchymal cells in other tissue. OBJECTIVE: The purpose of this study was to investigate whether EMD has the ability to induce hard tissue when applied with or without demineralized dentin matrix. METHODS: Half of the dentin tubes prepared from rat incisors were demineralized by treatment with 0.6 N hydrochloric acid for 3 h. EMD or PGA was injected into the demineralized or non-demineralized dentin tubes, which were then transplanted into rectus abdominis muscles. Untreated dentin tubes were also transplanted as a control. Animals were killed at 7, 14 and 21 days after the implantation. RESULTS: Non-demineralized dentin tubes with or without EMD or PGA did not form any hard tissue. In the demineralized group, chondrogenesis in the PGA groups occurred earlier than in the EMD groups. The expression of vascular endothelial growth factor (VEGF) mRNA in the demineralized group with PGA at day 14 was the highest. The expression of osteopontin and osteocalcin mRNAs was higher in all groups at 21 days compared with 7 or 14 days. CONCLUSION: These results suggest that neither EMD nor PGA has the ability to induce hard tissue and that EMPs contained within EMD might aggregate on the dentin surface and inhibit the effect of the demineralized dentin matrix.

Alginates↗
PubMed2004

Pulp canal obliteration in an unerupted permanent incisor following trauma to its primary predecessor: a case report.

Trauma to a primary tooth may result in damage to the underlying developing permanent tooth bud because of the close proximity between the root of the primary tooth and its permanent successor. We report an unusual case where injury to the primary dentition resulted in pulp canal obliteration (PCO) of a permanent maxillary central incisor prior to its eruption. The other permanent maxillary central incisor was diagnosed as malformed because of trauma to the primary dentition at an earlier age. The occurrences of PCO or crown malformation dose not routinely disrupt the eruption of those teeth. Periodic assessment is required to determine the need for endodontic intervention.

Child↗
PubMed1995

Developmental arrest of tooth bud after correction of mandibular fracture.

A case of multiple fractures of the mandible following a car accident in a five-year-old patient is reported. The fracture line passed distal to the first molar tooth bud. The fracture was treated by wire osteosynthesis and skeletal fixation. During the ensuing 18 months, a gradual arrest of the development of the first molar tooth bud was radiologically observed. The eruption process had not been disturbed, and the tooth erupted at the age of 6 1/2 years. Since the distal root had completely failed to develop and the mesial roots showed a diminished size, the tooth was extracted. Histopathological examination revealed disturbed dentin apposition, there was almost complete obliteration of the pulp chamber by globular dentin, and evidence of root resorption.

Child, Preschool↗
PubMed1997

Intra-alveolar surgical uprighting of impacted teeth: a case report.

Although orthodontic repositioning of impacted teeth is widely used, the treatment has its limitations. Autotransplantation or intra-alveolar surgical repositioning of teeth is an alternative therapy that may be used in selected cases of desperate impactions, when orthodontic extrusion is unsuccessful or when orthodontic treatment is rejected by the patient. A case report is presented to stress both the indications and limitations of a modified technique of intra-alveolar surgical uprighting of impacted teeth.

Alveolar Bone Loss↗
PubMed1999

The role of dietary fluoride supplements in caries prevention.

Nearly all dental researchers and public health authorities agree that fluoride supplements are highly effective in reducing dental caries in primary and permanent teeth, that benefits to all teeth are greater when administration begins at 2 years of age or younger, that both preeruptive and posteruptive exposure is important in imparting cariostatic benefits, that effectiveness is neither enhanced nor reduced by their being combined with vitamins, and that benefits to the offspring of pregnant women who take supplements are uncertain. Several studies show that fluoride supplements delivered in school-based programs effectively reduce dental caries, and benefits are greater to teeth that receive preeruptive exposure in addition to posteruptive exposure. Many parents who, for a variety of reasons, did not administer fluoride supplements at home will enroll their children in school-based fluoride tablet programs. Effectiveness of fluoride supplements today is undoubtedly smaller than observed previously because of dilution and diffusion effects from other fluoride sources; nevertheless, they still have the same potential efficacy. It is apparent that the current ADA dosage schedule is too high and requires modification; however, the availability of this known-to-be-effective regimen should not be eliminated or restricted.

Adolescent↗
PubMedDate not supplied

Oligodontia: a radiographic comparison of subjects with Down syndrome and normal subjects.

Panoramic radiographs and clinical records were used to investigate developmentally absent permanent teeth in 98 subjects with Down syndrome (trisomy-21). This retrospective study was based on the records and panoramic radiographs of subjects from approximately five years of age (the age at which mineralization of the permanent tooth germ could be identified) through to their most recent records. The time period covered by records ranged from 6 to 28 years. The majority of subjects with Down syndrome (63%) exhibited oligodontia, and many subjects were missing two or more teeth (53%). The most frequently absent teeth were the lower lateral incisors (23.3%), the upper second premolars (18.2%), the upper lateral incisors (16.5%), and the lower second premolars (15.3%). In general, the distribution of the developmentally absent teeth was similar for teeth in homologous positions (i.e., left and right canines, etc.) on either side of the midline or between the maxilla and the mandible. The only significant exceptions to this pattern were seen with the central incisors and the second molar. This study's findings suggest a high risk of oligodontia in subjects with Down syndrome.

Anodontia↗
PubMed1977

Effects of ionizing radiation on incisor development of the prenatal mouse.

The effects of 100 rad of X-irradiation of incisor development in CD1 mice were studied. 24 pregnant mice were irradiated on the 12th day post coitum and sacrificed from the 14th through the 20th gestational days. The 191 irradiated fetuses were smaller than those not irradiated, their crania and necks were malformed and their lower extremities were poorly developed. The developing incisors of the irradiated animals were retarded, the pulpal vessels were enlarged and the vessels walls did not maintain their structural integrity. The cells of the future pulp were necrotic, and the basement membranes appeared hyalinized. Ameloblasts and odontoblasts were abnormal in morphology and the formation of dental hard tissue was inhibited in places. Complete absence of incisor tooth germ was noted in three of the fetuses.

Animals↗
PubMed1984

Synthesis and secretion of the enamel matrix precursor by the kitten secretory ameloblast.

Secretory ameloblasts in kitten molar tooth germs were examined with an electron microscope to analyze the synthesis and secretion processes of the enamel matrix precursor. The contents of the secretion granule were identified as fine granular material, which observed in both the rough endoplasmic reticulum and the Golgi cisterns, accumulated in the dilated margins of the innermost Golgi cistern and formed condensing vacuoles. The same kind of condensing vacuoles was also produced from the GERL cisterns. During the secretion granule maturation processes in the Golgi region, the contents accumulated densely and the granules grew smaller. In addition, granule-limiting membranes acquired fine, bristle coats. The mature secretion granules then migrated, along microtubules, into the surfaces of the Tomes processes and finally released their contents by a process of exocytosis at the type 1 face which faces the enamel growth region.

Ameloblasts↗
PubMed1985

Ultrastructure of secretory ameloblasts in puppies.

Four about 4-week-old puppies were fixed by perfusion; the secretory ameloblasts of the first molar tooth germs were observed with an electron microscope. The morphology of the puppy secretory ameloblast closely resembles that of man. In addition, the primary cilia and a pair of basal bodies were observed close to Golgi apparatus of the secretory ameloblast. Cytoplasmic microtubules radiated from the basal bodies. It is suggested that a pair of basal bodies may be the microtubule-organizing center of the secretory ameloblast. Further, melanocytes were present in the intermediate cell layer and aggregated melanosomes were present in the cytoplasm of both stratum intermedium cells and secretory ameloblasts.

Ameloblasts↗