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Interleukin-1 (IL-1) bioactivity and inhibition of IL-1 bioactivity in supernatant fluid from cultured microphthalmic (mi) mice teeth of different ages.

A functioning dental follicle and bone resorption are necessary for tooth eruption. In the microphthalmic (mi) mouse, bone resorption is defective and teeth fail to erupt. Local bone metabolism involves the production of cytokines such as interleukin-1 alpha (IL-1 alpha) and transforming growth factor-beta (TGF-beta). The production of these cytokines by dental tissues during eruption may be fundamental to tooth movement. Molars from mi mice were cultured and supernatants tested for the presence of these cytokines using bio-dot blotting and ELISA. A thymocyte bioassay was used to test supernatants for IL-1 bioactivity and IL-1 inhibition bioactivity. IL-1 alpha and TGF-beta were detected in all supernatants. Supernatants demonstrated no IL-1 bioactivity but inhibited IL-1 bioactivity which varied with concentration of supernatant, age and animal. This study demonstrated that cultured developing teeth secrete IL-1 alpha and TGF-beta however, concentrations varied in normal and pathological states. While IL-1 alpha was present in the supernatants, all demonstrated a variable ability to inhibit IL-1 bioactivity. This ability may influence local bone metabolism and hence tooth eruption.

Aging↗

The application of Moire magnification to high-resolution studies of human premolar eruption.

The optical phenomenon of Moire magnification can be used to provide real-time measurements of the position of an erupting human premolar, with a resolution of 0.1 micron or better. A new instrument for this purpose, which allows repeated measurements in the same individual, is described. Cyclic changes in the position of the erupting tooth in concert with the heartbeat, with a magnitude of 0.05-0.35 micron, can be discerned. An unusual cyclic rhythm, with a period of 20-50 s, was observed.

Bicuspid↗

Quantitative histological features and ultrastructure of opercula of human teeth showing normal and delayed eruption.

BACKGROUND: Failure of eruption of human permanent molars has been attributed to opercular lesions, although comparisons with specimens from normally erupting teeth are scarce. The aim of this study was to quantitatively analyse opercula associated with normal and delayed tooth eruption. METHOD: Twenty opercula covering permanent molars delayed in eruption were obtained from 13 patients aged 7.3-18.1 years. Six opercula from normally erupting molars of five 7.3-17.5-year-old subjects served as controls. Specimens were analysed light and electron microscopically and morphometrically. RESULTS: In addition to features recognized previously, prominent numbers of nerves, high endothelial-like venules and mast cells were observed. Ultrastructurally, large multinucleated cells did not reveal cell boundaries running between the nuclei, and mast cells seemed belonging to the MC(TC)-type. None of the features differed significantly between opercula from cases of delayed and normal tooth eruption. CONCLUSIONS: Disturbances of tooth eruption that are attributed to opercular lesions may represent retentions resulting from the failure of the eruption mechanism, rather than impactions because of a physical barrier.

Adolescent↗

Dental follicle cell-conditioned medium enhances the formation of osteoclast-like multinucleated cells.

An influx of mononuclear cells and the subsequent increase of osteoclasts around tooth germs suggests that the dental follicle (DF) regulates or influences bone resorption required for tooth eruption. In order to study the effects of DF cell products on osteoclast formation during tooth eruption, a conditioned medium (CM) was created in which DF cells were added to mouse bone marrow cultures. Tartrate-resistant acid phosphatase (TRAP)-positive osteoclast-like multinucleated cells were formed in the presence of 10 nM 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]. The CM, dose-dependently, stimulated the formation of TRAP-positive cells in the presence of 1,25(OH)2D3 for 14 days culture. The number of these cells decreased due to degradation in the control culture. A semi-solid methylcellulose assay in the presence of CM showed little expression of colony-stimulating activity. These results suggest that the DF cells of a developing tooth produce factor(s) that enhance osteoclast formation and bone resorption necessary for tooth eruption.

Acid Phosphatase↗

The periodontal enigma: eruption versus tooth support.

The response of the periodontal ligament is reviewed when single or repeated loads are applied to the tooth, as in mastication. A more nearly elastic recovery is produced with simulated chewing than is indicated by single semi-static applications of force. The resting position of the tooth between loadings changes with the time of day and recent loading history. An unstressed tooth extrudes at a variable rate. Soon after entry into the mouth, extrusion is a progressive feature, which manifests as eruption with consequent structural rearrangement of the periodontium. Rates of extrustion are substantially higher than eruption. Experimental evidence is presented that newly erupted teeth of monkey erupt in a similar manner to rodent incisors. Thus reduction in masticatory loads allows teeth to erupt faster than control teeth. It is concluded that the ligament is well constructed to withstand the large but short-acting forces which occur in mastication and which cause relatively small, long term effects, on the position of the tooth in the alveolus. When unstressed, mechanisms in the ligament of a tooth with a developing or fully formed root, generate a continuous net force in the order of a gram tending to cause extrusion. The position a tooth adopts is determined by the interplay of these opposing sets of greatly differing forces.

Animals↗

[Eruption times of permanent teeth in children and adolescents of Paderborn, Westphalia, Germany].

The eruption times of permanent teeth and the sequence of tooth eruption were investigated in 1535 individuals aged 3 to 24 years. Wisdom teeth were excluded from the evaluation. All individuals were inhabitants of Paderborn, Westphalia, Germany. The results were compared to results of other German studies on tooth eruption of the 20th century. The teeth emerged symmetrically in each jaw. However, teeth erupted earlier in the mandible than in the maxilla. Teeth erupted earlier in females than in males. The sequence of emerging teeth in the maxilla is identical in both sexes: first molar, central incisor, lateral incisor, first premolar, and canine, second premolar, second molar. The sequence of tooth eruption of the mandible is identical in both sexes but differs from the maxillary sequence: first molar, central incisor, lateral incisor, canine, first premolar, second premolar, second molar. Since the fifties of the last century the acceleration of teeth emergence has not increased in German studies on this subject.

Adolescent↗

Longitudinal post-eruptive mandibular tooth movements of males and females.

Unbiased estimates of post-eruptive eruption and migration of the mandibular teeth for large representative samples are presently unavailable. The purpose of this study was to evaluate pure tooth movements of untreated children and adolescents longitudinally. Lateral cephalograms of 214 French-Canadians, followed bi-annually between 8 and 15 years of age, were traced, and the positions of the mandibular permanent central incisors and first molars were digitized. Temporal changes in tooth position were evaluated relative to naturally stable mandibular reference structures, using the mandibular reference line for orientation. The statistical analyses included t-tests to assess gender differences and Pearson product-moment correlations to evaluate associations. The results showed that the incisors proclined significantly more for males (6 degrees) than females (3 degrees). The incisor tips displayed early mesial movements that were countered by later distal movements. The incisor apex showed a consistent pattern of distal migration between 8 and 15 years. Mandibular arch length decreased over the 7-year observation period. Rates of mesial molar migration accelerated until 11 years of age and then decelerated. There was no significant change in the mandibular occlusal plane angle between 8 and 15 years of age. Incisor eruption showed the greatest rates during adolescence, attaining peaks at approximately 12 years for females and 14 years for males. The molars erupted approximately 5 mm between 8 and 15 years of age. The greatest gender differences occurred at the older ages, with males showing greater eruption potential than females. It was concluded that the mandibular teeth show significant migration and eruption during childhood and adolescence, with gender differences in the amount, direction, and timing of movement.

Adolescent↗

Orthodontic tooth movement in the mixed dentition. Histological study of a human specimen.

MATERIAL AND METHOD: We present a retrospective analysis of periodontal tissue reactions and clinically relevant phases of permanent tooth eruption and deciduous tooth resorption after half a year of orthodontic tooth movement in the upper and lower jaw of a deceased male (age 9 years 3 months). Specimens of the horizontal plane (lower jaw) and sagittal plane (upper jaw) were prepared by the ground microsection technique without prior decalcification. RESULTS: Histologically, reactions in the periodontal ligament presented as characteristic appositional/resorptive metaplastic processes in the areas of tension and pressure, with side effects such as root resorption and periodontal necrosis being only minor. In the upper jaw, an erupting permanent canine was closely associated with the tooth germ of the first premolar. Resorptive follicle activity had resulted in extensive erosion of the interradicular bone and root resorption in the area of the first premolars. CONCLUSION: These findings suggest that it might prove useful to take critical topographic findings as parameters for differential therapeutic decisions. Follicle-driven deciduous tooth resorption presenting partly as resorption lacunae and partly with linear characteristics was accompanied by resorptive/appositional remodeling of the alveolar socket as well as regressive changes in the supracrestal fibers of the marginal gingiva.

Child↗

Expression of type I and XII collagen during development of the periodontal ligament in the mouse.

The purpose (of this study) was to determine the temporal and spatial pattern of type XII collagen expression during murine tooth/root development. Using in situ hybridization techniques, expression of type XII collagen was compared with that of type I collagen, the most abundant collagen in periodontal tissues. Mouse first mandibular molars were examined at the following developmental periods: pre-root formation, early root formation, initial alignment of the periodontal ligament (PDL) fibres, and PDL maturation as the tooth erupted and attained occlusal function. Transcripts for type I collagen were identified in bone cells and odontoblasts at all times but not in the dental follicle before root formation. As root formation progressed, type I collagen expression became apparent within cells of the dental follicle and forming PDL. During early stages of tooth development, signal for type XII collagen was not observed in any cells/tissues. Type XII collagen expression was first detected in the dental follicle/PDL region during tooth eruption and increased in the PDL as the molar tooth erupted into the mouth and achieved occlusal contact. These findings suggest that type XII expression is timed with the alignment and organization of PDL fibres and is limited in tooth development to cells within the periodontal ligament.

Animals↗

X-ray diffraction of enamel of a freshly erupted human tooth.

Small slices were cut from enamel prepared from the labial surface of a freshly erupted human premolar. Consecutive slices (200 micrometers thick) were taken at distances 500 micrometers apart from each other. X-ray diffractograms were obtained from each slice in a Guinier camera. Only the slices cut from the outer 500 micrometers of human enamel resulted in distinct reflections. Typical lattice parameters were a = 9.462 A and c = 6.898 A for one slice and a = 9.457 A and c = 6.890 A for another slice of outer enamel. Non-apatitic reflections could not be detected. The line-broadening occurring in deeper layers was shown to be due either to intracrystalline strain or to inhomogeneities on the crystalline level. Theoretical models and submicroscopical findings of other authors are discussed in relation to the present findings.

Apatites↗

Characteristics of mastication in the anodontic mouse.

Teeth and periodontal mechanoreceptors play important roles in regulating jaw movements during mastication. However, little is known concerning how jaw movements develop without tooth eruption. To answer this question, we studied masticatory behavior in the osteopetrotic mouse, where tooth eruption does not occur and periodontal mechanoreceptors are missing. A masticatory sequence of the osteopetrotic mouse was divided into two stages: incision and chewing. Incision is characterized by small amplitude and rapid (7 Hz) open-close jaw movements, while slow (5 Hz) and large amplitude open-close jaw movements characterize chewing. The frequency and properties of jaw movements were comparable with those in the normal mouse, though the osteopetrotic mouse had a higher cycle number during incision than did the normal mouse. These results indicate that conversion from sucking to mastication occurs in the anodontic mouse, and the central pattern generator producing the masticatory rhythm develops almost normally without tooth eruption.

Animals↗

Oral streptococcal colonization of infants.

The objective of this study was to determine the prevalence and proportions of different streptococcal species among the streptococcal flora during infancy. A total of 60 oral samples were collected by oral swabbing of the buccal mucosa and alveolar ridges of 18 infants before tooth eruption and from buccal and lingual surfaces of teeth after tooth eruption. A total of 549 isolates on mitis salivarius agar were speciated, principally by recently revised biochemical criteria of Kilian et al. Streptococcus mitis biovar 1 predominated, both in prevalence (89%) and proportion of oral streptococci recovered in each sample (median = 87% of streptococcal flora). Streptococcus salivarius was also prevalent (94%) but generally represented a small percentage of the total streptococcal flora (median = 3%). Streptococcus oralis and Streptococcus anginosus strains were detected in approximately one third of predentate and dentate infants in the first year of life. Streptococcus sanguis strains were not detected before tooth eruption, but could be detected in 7/14 of the infants with teeth. Thus, S. mitis constitutes the major component of the initially colonizing streptococcal microbiota of the young infant.

Alveolar Process↗

Fenestrated capillaries in the periodontal ligaments of the erupting and erupted rat molar.

Quantitative ultrastructural studies were conducted on eight rats (four aged 21 days and four aged 8 weeks) using the periodontal tissues around the mesial root of the mandibular first molar. The periodontal ligament of the erupting tooth contained significantly more capillary fenestrations than the erupted tooth, both in terms of the number per unit area of endothelium (2.2/microns2) and in terms of total number per cubic millimetre of tissue (30.5 X 10(6)/mm3). Differences were also discerned with respect to the percentage of capillaries in the tissue. Thus, the periodontal vasculature demonstrates marked morphological changes which may be related to the eruptive phase of the tooth.

Animals↗

Bilateral eruption sequestra: report of case.

A case report of bilateral eruption sequestra was presented. The eruption sequestrum must be included in the differential diagnosis of pain during eruption. Although previously thought to have little clinical significance, the eruption sequestrum may retain plaque in close association with the newly erupting tooth. The retained eruption sequestrum may lead to pericoronitis or pit and fissure caries. While many spontaneously resorb or exfoliate, some, as in this case, may need surgical removal.

Bone and Bones↗

Eruption of tooth-like structure following the exfoliation of natal tooth: report of case.

Natal teeth, defined as those that are the mouth at birth, are rare: one case in 2,000 to 3,500 births. In this case, that of a nine-month-old Japanese boy, it is reasonable to infer that the tooth-like structure, described as a hard-tissue conglomerate with a bone-like appearance, originated in the remnant of the dental papilla and Hertwig's sheath of the natal tooth. Both dentin and root formation were thereby induced.

Dental Enamel Hypoplasia↗

In vitro development of lower first molars from the osteopetrotic microphthalmic (mi) mouse.

While the precise mechanism of tooth eruption remains unknown it has been established that for tooth eruption to occur a functioning dental follicle is essential and normal bone resorption is required. In the osteopetrotic microphthalmic (mi) mouse, teeth fail to erupt and development is affected. In the present study, an organ culture technique was established to culture successfully lower first molars from normal and affected mi mice so as to determine if developmental defects were intrinsic to the dental tissue or whether such defects were a result of local environmental factors. Tissue was cultured for up to 13 days and development assessed morphologically at varying time intervals using standard light microscopy. Teeth developed similarly in both animal groups studied. The only variation in the appearance of cultured tissue occurred in the cervical loop region with more curling evident in dental tissue from the affected animals. The results of this study therefore showed that dental tissue from both normal and affected mi mice can be cultured for up to 13 days and that there is no difference in their development. It would appear that these teeth have the same ability to develop and consequently erupt, however the local environment influences tooth development and alters the eruption potential.

Ameloblasts↗