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At least 937 records · Page 52Linked to original sources
PubMed1997

Changes in the shape and orientation of periodontal ligament fibroblasts in the continuously erupting rat incisor following removal of the occlusal load.

One of the main theories which attempts to explain the phenomenon of tooth eruption suggests that periodontal ligament (PDL) fibroblasts move actively and pull the tooth with them out of its socket. To find further support for this theory, we determined the changes in the shape and orientation of PDL fibroblasts induced by a transition from impeded to unimpeded eruption. We measured nuclear area, elongation (length-to-width ratio), and orientation (angulation in relation to the eruption axis) of PDL fibroblasts in impeded (functionally loaded) and unimpeded (hypoloaded) rat incisors. The mean cross-sectional nuclear area did not differ between fibroblasts in the two groups. In contrast, unimpeded eruption resulted in a marked increase in the mean nuclear elongation (from about 2 to 2.56) and a significant increase in the mean nuclear orientation (from 25.6 to 14.0 degrees). Bivariate analysis suggested that these changes occurred in the same cells. Analysis of nuclear elongation and orientation at various distances from the cementum toward the alveolar bone revealed a profile of both parameters, such that cells located 20 to 80 microns away from the cemental surface were more elongated and more frequently oriented toward the eruption axis, while cells at 0 to 20 and 80 to 100 microns were more round/oval and had a greater angulation with the eruption axis. These findings, together with other observations of changes in cell number, number of microtubules, and migration velocity which occur on the shift to unimpeded eruption, support the theory of active movement of PDL fibroblasts as an important component of tooth eruption.

Animals↗
PubMed1979

Structural alterations in proliferating, remodeling, and regressing tooth pulp arterioles.

In the continuously growing upper incisor of 100 g rats about 25 arterioles arise from an artery outside the tooth and pass through the apical foramen to run parallel to one another in the central part of the pulp, each supplying a well-defined sector of the migrating odontoblast layer. The arterioles pass through a cycle of proliferation, growth, remodeling, regression and decay, phase displaced in relation to each other. Proliferative and degenerative processes occur in the arteriole wall throughout the cycle, but vary considerably in intensity at different phases. Proliferation takes place by mitosis in the endothelium and the innermost smooth muscle cells. The degenerative process consists of reduction in size of smooth muscle cells by partial autodigestion and by cell death. When the odontoblasts reach the incisal extremity of the tooth, they die, and the associated regressed arteriole disappears. The system of pulpal arterioles has remarkable spatio-temporal features and each of its vessels appears to be in a state of sensitive structural equilibrium.

Animals↗
PubMed1979

Cell production in the normal and lathyrogenic rat periodontal ligament (PDL).

Thirty male albino rats weighing 200 g. each were separated into two groups. 15 rats received 0.2% 3-amino propionitrile fumarate (BAPN) in drinking water. 15 rats served as controls. Within three weeks eruption rate diminished by 50%. On the 22nd experimental day each rat received one dose of 1 microCi/g. body weight tritiated thymidine (1.9 Ci/mM). 5 rats of each group were then killed after 1 hour; 1 week and 2 weeks. The PDL cell migration rate was evaluated autoradiographically. It diminishes proportionally with the eruption rate. In the BAPN treated animals, the mean total periodontal ligament (PDL) cell count is 55.5% higher than that of the control.

Aminopropionitrile↗
PubMed1976

An autoradiographical study of [3H]thymidine incorporation into subcutaneously transplanted mouse molar teeth. Cell proliferation and migration in transplanted teeth.

Mice bearing either allografts or isografts of 10 day old molar teeth were injected with [3H]thymidine to identify proliferating and migrating cells within the graft and surrounding tissues. In isografts proliferating cells were found successively in the area underlying the cervix, in the cervical pulp and the coronal pulp. However, cells did not migrate from the cervical host tissue into the pulp, and it was concluded that donor cells are responsible for reparative processes in tooth isografts. Very few labelled cells were identified at any time in tooth allografts, which were not repaired. It is suggested that allografts are not repaired because allogeneic inhibition prevents the residual donor tissue from proliferating and differentiating. Inhibition of proliferation of residual cells may also account for the absence of a cell-mediated immune response to tooth allografts.

Animals↗
PubMed1991

The aged in dentistry.

Statistics show clearly the greying of our population and the profession must face the inevitable modifications to the delivery of dental care which will follow. We have spent many years fighting the high caries rate of youngsters and teenagers but, quite suddenly, that battle seems to be virtually won. Now we are faced with an ageing population who, with our help, have retained their teeth to an advanced age and they do not want to part with them. In fact, changing a patient to full dentures after the age of forty years is a very traumatic occurrence to both patient and operator. The profession now has two major problems to deal with in the area of restorative dentistry for the ageing patient. Firstly, teeth which have been retained but are heavily restored because of ongoing caries and bulk loss of tooth structure as a result of splitting or the application of careless restorative techniques. Secondly, the onset of root surface caries following migration of the epithelial attachment and exposure of root surfaces combined with a reduction in the efficacy of oral hygiene measures. Both problems are likely to appear after the age of sixty years and the patient may live for another twenty or thirty years in a gentle medical and physical decline. Maintenance of dental health presents a series of unique problems under these circumstances.

Aged↗
PubMed1991

[Furcation lesions in deciduous teeth].

The area of furcation of temporary molars constitutes a zone of exchanges and rearrangements relating to the evolution of the sub-adjacent permanent tooth. It is subjected to the eruption of the latter and to the physiological modifications of the temporary tooth. Moreover, this area is the site of above-mentioned inflammatory or infections conditions, maintained or aggravated by anatomical factors (accessory canals, thin pulpar floor, with little calcified dentine and broad tubuli), physiological factors (multiplication of accessory canals, decrease in the floor and migration of the epithelial attachment), endodontic factors (pulpal involvement and its complications) and periodontal factors (septum syndrome). The pathology of furcation is an evolving lesion. When discovered early it can be treated by endodontic therapy, while, in a later phase, it will require the extraction of the tooth. The assessment is made on the basis of a X-Ray examination which permits the temporary tooth to be situated in its stable or labile phase, the condition of the pulpal floor to be evaluated and the stage of sub-adjacent germ mineralisation to be estimated. A periodontal arrangement, by coronal reconstitution, conditions the reliability of the endodontic therapies.

Child↗
PubMed1990

[Effect of heavy metal ions on the cells derived from human periodontal ligament. Effects of Pb and Cd].

It has been thought that the incorporation of Pb and Cd into human body, especially calcified tissues including the tooth, has altered the physiological processes of development. But, the biochemical events that initiate this process remain quite unknown. The present study attempt to explore the effect of Pb and Cd on human periodontal ligament fibroblast-like cells of the permanent tooth (HPLF) and the deciduous tooth (HPLF-Y) with respect to the cell growth, ALPase activity and incorporation of 14C-amino acids. HPLF and HPLF-Y migrated from a explant and subcultured according to the previously described method of Saito were inoculated 1.25 x 10(4) cells/cm2 in D-MEM supplemented with 2 mg/ml FCSP, 50 micrograms/ml ascorbic acid and antibiotics. After 24 hrs, HPLF and HPLF-Y were treated every two days for 10 days with 0-200 microM Pb or 0-10 microM Cd. Protein contents, DNA contents and ALPase activity were determined by Bio-Rad protein assay, deaminobenzoic acid assay and p-nitrophenylphosphate (pH 10.15) assay respectively. At 6 days HPLF were incubated with 3H-thymidine (TdR 2.0 microCi/well) and then the incorporation of 3H-TdR into cold TCA precipitates was assayed by a liquid scintillation counter. And also, at 6 days HPLF and HPLF-Y were incubated with 14C-amino acids (2.0 microCi/60 mm dish) for 24 hrs. The cell layers labeled with 14C were extracted with 15 mM Tris-HCl buffer containing 7 M urea (pH 7.4) and applied to the gel permeation chromatography of HPLC system to separate the fractions according to molecular weight. The HPLF and HPLF-Y incubated with Pb and Cd were morphologically identical. Pb stimulated the protein contents of extracellular matrix of HPLF, but not HPLF-Y. Cd inhibited the protein contents of cell layers of HPLF and HPLF-Y. With increasing concentrations of Pb and Cd, the incorporation of 3H-TdR into HPLF was inhibited. On the other hand, Cd stimulated the ALPase activity per DNA content since the ALPase activity of HPLF and HPLF-Y was decreased by the addition of Pb. The distribution of 14C-labeled protein according to molecular weight did not alter the chromatographic pattern of HPLF incubated with Pb and Cd. But, that of HPLF-Y incubated with Pb was relatively shifted to low molecular size. Therefore, these responser concluded that HPLF were not completely identical with HPLF-Y. Pb and Cd not only had a toxic effect on cell growth, but also they may regulate the metabolic alteration.

Alkaline Phosphatase↗
PubMed1999

Expression of VLA-integrins and their related basement membrane ligands in gingiva from patients of various periodontitis categories.

Periodontitis is characterized by destruction of dento-gingival fibers and apical migration of the junctional epithelium. Tissue destruction may be associated with altered interactions between epithelium and connective tissue mediated by integrins localized in the basement membrane zone. We examined the expression of alpha2beta1, alpha3beta1, alpha4/alpha5/beta1, alpha6beta4 and their related extracellular matrix (ECM) ligands: laminin-1, laminin-5, and collagen type IV in untreated periodontitis sites of various categories. The expression and location of ECM proteins along the basement membrane were found to be similar between clinically healthy and periodontitis affected tissues. However, ECM proteins were more diffusely distributed in connective tissue (CT) of periodontitis tissues as streak-like/ fibrillar/granular stainings, particularly beneath the pocket epithelium (PE) and around the blood vessels. This may reflect an increase in inflammatory cell migration. The more widespread distribution of integrins alpha2beta1, alpha3beta1 in PE of periodontitis specimens may be related to disease activity and increased rate of keratinocyte proliferation and migration. Moreover, the weaker expression of alpha6beta4 in junctional epithelium (JE) of periodontitis affected tissues may be related to the epithelial detachment from the tooth surface. Clarification of expressions of integrins and their ligands in relation to known clinical disease susceptibility factors may provide information on the onset and progression mechanisms of periodontal disease destruction.

Adolescent↗
PubMed1982

[Neurocristopathic classification of dental abnormalities].

The neural crest of the vertebrae provides the odontoblasts, which by migrating in the stomodeal epithelium induce in the latter the formation of predamantoblasts (enamel cell). The odontoblasts are then the point of departure of tissue interactions (ectodermal and neurectodermal) which characterise dental organogenesis. An analytical neurocristopathic classification of this organogenesis based upon the developmental properties of the odontoblast is suggested: --abnormalities of formation (anodontism, hypodontism); --abnormalities of migration (ectopism); --abnormalities of cell differentiation and multiplication (hypodontism, microdontism and macrodontism, disturbances in odontogenesis and their combinations, disturbances in amelogenesis). "No odontoblast, no tooth". The dental organ is an indicator of the developmental biological activity of the neural crest as well as its neurulation. Abnormalities in dental organogenesis are of predictive value in terms of other abnormalities of cephalogenesis, those related to the differentiation of the other cells of the neural crest (bone, muscle, cartilage) and those related to the neural tube with which they are territorialised: these are dysneurulations. This classification covers the clinical features of dental abnormalities seen in pediatric stomatology.

Humans↗
PubMed2005

Maxillary canine transposition to incisor site: a rare condition.

Tooth transposition is defined as positional interchange of 2 adjacent teeth within the same quadrant. The incidence has been reported as about 0.4%, and the maxillary permanent canine has been reported as the tooth most frequently involved. Several etiologic factors like genetics, interchange in position of the developing tooth buds, trauma, mechanical interferences, and early loss of incisors have been associated with tooth transposition. Articles in the literature report various kinds of transpositions, but there are only a few reported cases of transposition of the maxillary canine to central incisor site. This kind of transposition has been suggested as resulting primarily by opportunistic canine migration into the space left from an early lost central incisor. However, there are only 2 long-term roentgenographic follow-up studies documenting maxillary canine migration and substantiating this hypothesis. This report shows 2 cases of this rare condition, with 1 of them documented with long-term records.

Adult↗
PubMed1995

Sinonasal teeth.

Ectopic eruption of the teeth in the sinonasal tract and the migration of a displaced dental fragment from the maxillary sinus to the nose are two rare phenomena. This paper reports three cases: an asymptomatic ectopic tooth within the nasal septum, an ectopic maxillary sinus tooth causing repeated attacks of sinusitis, and a dental root that reached the nose through the maxillary antrum associated with Aspergillus sinusitis. The etiology, diagnosis, complications, and treatment of simonasal teeth are discussed.

Adult↗
PubMed1984

Bioelectric perturbations of bone. Research directions and clinical applications.

Bioelectric perturbation of living hard tissue produces clinically useful effects. It is being used effectively in the treatment of intractable orthopedic problems such as nonunion and avascular necrosis. Dental applications of this phenomenon are still in the early stages of research and development. Barring untoward circumstances, this form of local growth control may be used as an adjunct to localized bone induction therapy such as in the treatment of periodontal diseases, bone grafting or implantation of biocompatible products. It also appears to show promise in enhancing the rate of tooth movement or the stability of anchor teeth. The mechanism for these perturbation-induced changes in cells has not been explained. This is an active area of research with many implications for helping the clinician understand the molecular biology of hard-tissue cell proliferation, migration and differentiation.

Animals↗
PubMed2002

Controlled orthodontic extrusion to create gingival papilla: a case report.

Prosthetic dental restorations alone do not produce esthetics. They must be in harmony with the surrounding gingiva, especially the gingival papilla. This case report describes the enhancement of the gingival papilla between an implant replacing the maxillary left central incisor and a provisional crown on the maxillary left lateral incisor. Esthetic harmony was disrupted by the absence of an interproximal papilla. First, provisional crowns on the implant and adjacent tooth were used in an attempt to remodel the interproximal gingival tissue, but the esthetic result was not satisfactory. The second attempt involved orthodontic extrusion of the lateral incisor in an incisal direction. The gingival tissue migrated incisally, thus restoring the deficient papilla and establishing restorative and gingival harmony. Both the implant and the lateral incisor were restored with ceramic crowns.

Crowns↗
PubMed1997

Expression of reelin, the gene responsible for the reeler mutation, in embryonic development and adulthood in the mouse.

reelin has recently been isolated as a candidate gene, the mutation of which gives rise to the reeler phenotype in mice. In this study, we analyzed the expression of reelin during embryonic development in the mouse and in adult mouse tissues, by in situ hybridization. reelin transcripts were present on embryonic day (E) 8.5 in the somite, foregut, yolk sac, and unclosed neural plate. reelin was expressed in the brain, spinal cord, liver, and kidney throughout embryonic development, and transiently in many developing organs such as the optic cup, blood vessels, precartilage, stomach, pituitary, vibrissae, tooth germ, and in cells along growing nerve fibers. These observations indicate a role for reelin in development of organs in addition to that in neuronal migration. Furthermore, we demonstrated the existence of reelin mRNA and its cellular distribution in the adult brain, spinal cord, liver, kidney, testis, and ovary, suggesting additional roles for reelin in stabilizing the cyto-architecture and in remolding in adult organs. However, we detected no obvious phenotype of the reelin-expressing organs except for the brain in the reeler mouse, indicating the functional redundancy of this gene during the development of these organs.

Animals↗