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At least 1,135 records · Page 63Linked to original sources

PubMed1999

Timp-1, -2 and -3 show coexpression with gelatinases A and B during mouse tooth morphogenesis.

Matrix metalloproteinases (MMPs) have been implicated in tissue remodelling and in regulation of cell-matrix interactions during organ development. The activity of MMPs is regulated by members of the TIMP (tissue inhibitors of metalloproteinase) family. We analyzed by in situ hybridization the expression of gelatinase A (MMP-2) and gelatinase B (MMP-9) as well as Timp-1, -2 and -3 during different stages of mouse tooth development. Gene expression was generally found in mesenchymal tissues except for Timp-3, which also was found in dental epithelial cells. During early tooth development, gelatinase A and Timp-2 were widely expressed in the branchial arch, while gelatinase B and Timp-1 and Timp-3 expression showed clear association with epithelial morphogenesis and was restricted to the mesenchyme at the tip of the growing tooth bud. Gelatinase A and Timp-1 showed transient expression in secretory odontoblasts at the time of basement membrane degradation, while Timp-2 expression continued throughout the dental papilla. At the time of tooth eruption, Timp-3 was expressed in most dental epithelial cells except secretory ameloblasts, and gelatinase B was intensely expressed in osteoclasts in the jaw bone. The exact co-localization of gelatinase A and Timp-1 in secretory odontoblasts, and the correlation between gelatinase B and Timp-3 during bone resorption may indicate interaction of the proteins during degradation of the basement membrane and in the control of ECM turnover in connection with tooth eruption.

Animals↗

PubMed1999

Messenger RNA level and protein localization of transforming growth factor-beta1 in experimental tooth movement in rats.

Transforming growth factor-beta1 (TGF-beta1) is known to be associated with local bone remodeling. We hypothesize that TGF-beta1 is induced in bone and regulates adaptive alveolar bone modeling during tooth movement. To test this hypothesis, we examined the steady-state mRNA level of TGF-beta1 and the protein localization of TGF-beta1 and its type II receptor (TbetaR-II) during experimental tooth movement. Maxillary right molars, M1, M2 and M3, of rats were moved palatally for 1, 3 and 7 d by a finger coil spring anchored to the upper incisors. The contralateral side was used as a control. After 3 d of tooth movement, intense immunostaining for TGF-beta1 and TbetaR-II was observed in cuboidally shaped osteoblasts in the tension zone, and in bone-resorbing osteoclasts in the compression zone. On the control side, few active osteoblasts and osteoclasts were observed. Reverse transcriptase-competitive polymerase chain reaction revealed significant increases in TGF-beta1 mRNA in alveolar bone cells on the tooth movement side on day 3 and day 7. Taken together, our data indicate that TGF-beta1 is induced during tooth movement and we propose that this may regulate adaptive alveolar bone modeling.

Alveolar Process↗

PubMed2000

Influence of previous restoration of the tooth on prognosis of crowns with dowels.

Due to extensive loss of tooth substance the restoration of endodontically treated tooth requires intracanal dowels to give an efficient strength for the crown. The aim of our study was to investigate whether the previous type of restoration of the tooth, i.e. composite restoration with screw post versus one-piece dowel crown, has an effect on the prognosis of crowns with dowels. The material consisted of 111 single crowns and as a previous restoration there were 83 composite restorations with screw posts and 28 one-piece dowel crowns. The mean follow-up time was 78 months (range 6--163 months). The cumulative survival was 87% for one-piece dowel crowns and 84% for composite resins with screw posts. There were six root fractures, four losses of cement retention and one tooth extraction due to caries in crowns with previous composite resin with screw posts. In one-piece dowel crowns as a previous restoration there were two root fractures and one tooth extraction for periodontal reasons. In conclusion, it seems that the previous restoration has no marked effect on the prognosis of crowns with dowels when studying a composite resin restoration with screw post and a one-piece dowel crown.

Adult↗

PubMed1998

Three-dimensional ultrasound evaluation of fetal tooth germs.

OBJECTIVE: A total of 126 genetic syndromes are associated with oligodontia or anodontia. The most frequent of these are ectodermal dysplasias, all types of facial cleft and Down's syndrome. With the advent of three-dimensional ultrasonography, accurate assessment of many fetal abnormalities has become possible. The objective of this study was to determine the effectiveness of three-dimensional ultrasonography in the visualization of fetal tooth germs. DESIGN: We examined 45 women with singleton pregnancies between 16 and 36 gestational weeks who were undergoing routine ultrasound check-ups for fetal tooth germs with conventional two-dimensional ultrasonography, followed by three-dimensional ultrasonography using multiplanar reconstruction. RESULTS: In the 45 fetuses studied, fetal tooth germs were visualized at the first attempt in 36 cases (80%). In the group of fetuses aged between 19 and 36 weeks of gestation, the overall detection rate in both jaws was at least 86% for three-dimensional ultrasonography, compared to at least 56% for two-dimensional ultrasonography. CONCLUSIONS: Three-dimensional ultrasonography was clearly superior to conventional ultrasonography in the visualization and evaluation of fetal tooth germs. Three-dimensional ultrasonography therefore has a potential for enhanced visualization of fetal tooth germs and may aid in the antenatal detection of syndromes associated with oligodontia or anodontia.

Cleft Lip↗

PubMedDate not supplied

The cusp of evolution and development: a model of cichlid tooth shape diversity.

Tooth shape is a hallmark of repeated evolutionary radiations among cichlid fishes from East Africa. Cusp shape and number vary both within populations and among closely related species with different feeding behaviors and ecologies. Here, we use histology and scanning electron microscopy to chart the developmental trajectory of tooth shape differences in fishes from Lake Malawi. We demonstrate that species with bi- or tricuspid adult (replacement) teeth initially possess a first-generation unicuspid dentition. Notably, the timing of turnover from first-generation to replacement teeth differs among species and is correlated with feeding ecology. Next, we use field data for cichlid species with adult unicuspid, bicuspid, and tricuspid teeth to demonstrate a strong and positive relationship between the number of teeth in a row and tooth shape. We discuss cichlid tooth ontogeny in the context of morphogenetic models designed to explain the developmental basis of tooth shape variation in mammals. We suggest that the dramatic differences in cichlid dentitions can be explained by variation in the expression of common activators and inhibitors acting at multiple stages of odontogenesis.

Animals↗

PubMed2002

Alkaline phosphatase activity in gingival crevicular fluid during human orthodontic tooth movement.

Bone remodeling that occurs during orthodontic tooth movement is a biologic process involving an acute inflammatory response in periodontal tissues. A sequence characterized by periods of activation, resorption, reversal, and formation has been recently described as occurring in both tension and compression tooth sites during orthodontic tooth movement. We used a longitudinal design to investigate alkaline phosphatase (ALP) activity in gingival crevicular fluid (GCF) to assess whether it can serve as a diagnostic aid in orthodontics. Sixteen patients (mean age, 15.5 years) participated in the study. The maxillary first molars under treatment served as the test teeth (TT) in each patient; in particular, 1 first molar was to be retracted and hence was considered the distalized molar (DM), whereas the contralateral molar (CM) was included in the fixed orthodontic appliance but was not subjected to the distal forces. The DM antagonist first molar (AM), free from any orthodontic appliance, was used as the baseline control. The GCF around the experimental teeth was harvested from mesial and distal tooth sites immediately before appliance activation, 1 hour after, and weekly over the following 4 weeks. The clinical gingival condition was evaluated at the baseline and at the end of the experimental term. ALP activity was determined spectrophotometrically at 30 degrees C, and the results were expressed as total ALP activity (mUnits/sample). GCF ALP activity was significantly elevated in the DMs and the CMs as compared with the AMs at 1, 2, 3, and 4 weeks; conversely, in the AMs, GCF ALP activity remained at baseline levels throughout the experiment. Moreover, the enzyme activity in the DMs was significantly greater than in the CMs. In the DMs, a significantly greater ALP activity was observed in sites of tension compared with sites of compression. This difference was not seen with the CMs, in which the enzyme activity increased to the same extent in tension and compression sites. These results suggest that ALP activity in GCF reflects the biologic activity in the periodontium during orthodontic movement and therefore should be further investigated as a diagnostic tool for monitoring orthodontic tooth movement in clinical practice.

Adolescent↗

PubMed2002

Concomitant occurrence of canine malposition and tooth agenesis: evidence of orofacial genetic fields.

Certain discrete malpositions of the human canine tooth and agenesis of at least 1 tooth (hypodontia) are abnormalities known to occur together frequently. This study examines the specificity of tooth-agenesis sites associated with the occurrence of 3 unambiguous canine malpositions: palatally displaced canine (PDC; n = 58), mandibular lateral incisor-canine transposition (Mn.I2.C; n = 60), and maxillary canine-first premolar transposition (Mx.C.P1; n = 43). A fourth sample was formed from 4 cases of combined occurrence of PDC and Mn.I2.C, the only combination-phenotype noted among the 161 subjects. Oral panoramic radiographs were used to identify agenesis of at least 1 third molar (M3), mandibular second premolar (MnP2), and maxillary lateral incisor (MxI2)-the 3 most frequently absent tooth types among people of European descent. PDC and Mn.I2.C transposition appear to be associated with significantly increased M3 agenesis (P <.01), representing the posterior orofacial field, and Mx.C.P1 transposition appears to be associated with conspicuously elevated MxI2 agenesis (P <.001), representing the anterior orofacial field. MnP2 agenesis appears to represent an intermediate field, found in significantly elevated frequencies with all 3 canine positional anomalies. Coupling these new clinical findings with results from recent molecular studies, we suggest that transcription factors such as MSX1 and PAX9, which have been associated with agenesis of molars, might be involved in the genetic control of Mn.I2.C transposition and PDC, tooth malpositions connected here with the specific expression of posterior-field (M3) hypodontia.

Adolescent↗

PubMed2001

Tooth preparations for complete crowns: an art form based on scientific principles.

STATEMENT OF THE PROBLEM: No recent literature has reviewed the current scientific knowledge on complete coverage tooth preparations. PURPOSE: This article traces the historic evolution of complete coverage tooth preparations and identifies guidelines for scientific tooth preparations. MATERIAL AND METHODS: Literature covering 250 years of clinical practice was reviewed with emphasis on scientific data acquired during the last 50 years. Both a MEDLINE search and an extensive manual search were used to locate relevant articles written in English in the last 50 years. RESULTS: Teeth should be prepared so that they exhibit the following characteristics: 10 to 20 degrees of total occlusal convergence, a minimal occlusocervical dimension of 4 mm for molars and 3 mm for other teeth, and an occlusocervical-to-faciolingual dimension ratio of 0.4 or greater. Facioproximal and linguoproximal line angles should be preserved whenever possible. When the above features are missing, the teeth should be modified with auxiliary resistance features such as axial grooves or boxes, preferably on proximal surfaces. Finish line selection should be based on the type of crown/retainer, esthetic requirements, ease of formation, and personal experience. Expectations of enhanced marginal fit with certain finish lines could not be validated by recent research. Esthetic requirements and tooth conditions determine finish line locations relative to the gingiva, with a supragingival location being more acceptable. Line angles should be rounded, and a reasonable degree of surface smoothness is desired. CONCLUSIONS: Nine scientific principles have been developed that ensure mechanical, biologic, and esthetic success for tooth preparation of complete coverage restorations.

Bicuspid↗

PubMed2006

Continuous tooth generation in mouse is induced by activated epithelial Wnt/beta-catenin signaling.

The single replacement from milk teeth to permanent teeth makes mammalian teeth different from teeth of most nonmammalian vertebrates and other epithelial organs such as hair and feathers, whose continuous replacement has been linked to Wnt signaling. Here we show that mouse tooth buds expressing stabilized beta-catenin in epithelium give rise to dozens of teeth. The molar crowns, however, are typically simplified unicusped cones. We demonstrate that the supernumerary teeth develop by a renewal process where new signaling centers, the enamel knots, bud off from the existing dental epithelium. The basic aspects of the unlocked tooth renewal can be reproduced with a computer model on tooth development by increasing the intrinsic level of activator production, supporting the role of beta-catenin pathway as an upstream activator of enamel knot formation. These results may implicate Wnt signaling in tooth renewal, a capacity that was all but lost when mammals evolved progressively more complicated tooth shapes.

Animals↗

PubMed2005

Tooth loss and associated risk indicators in an adult urban population from south Brazil.

The aim of the present study was to assess the prevalence, extent, and risk indicators of tooth loss in a representative adult, urban population in the Brazilian state of Rio Grande do Sul. A sample of 974 subjects (ages 30 to 103 years, mean 48.7, SD 13.4) representative of the metropolitan area of Porto Alegre, Brazil was selected by a multi-stage probability cluster sampling strategy. In all, 94% of the subjects had experienced tooth loss. The mean tooth loss was 11.2 teeth, and varied between 5.5 and 20.2 teeth in the 30-39 and 60 + years age groups, respectively. The multivariable analysis, adjusted for age, showed that subjects who had lost 7-13 or > or = 14 teeth were more likely to be females (odds ratio (OR) = 1.4, 2.4), of low (OR = 2.8, 5.1) or middle socio-economic status (OR = 2.3, 3.4), and heavy smokers (OR= 2.0, 2.3) than those with 6 or fewer missing teeth. Furthermore, loss of > or = 14 teeth was associated with presence of > 50% teeth with attachment loss > or = 5 mm (OR= 5.7), and loss of 7-13 teeth was associated with presence of > 50% teeth with attachment loss > or = 5 mm (OR = 2.4) and having 15-30% or > 30% decayed-filled teeth (OR = 2.7 and 4.1). In conclusion, tooth loss is highly prevalent in this urban Brazilian population. Gender, socio-economic status, cigarette smoking, caries experience, and attachment loss are important risk indicators. A reduction in the population's tooth loss may be achieved by the implementation of community programs for the prevention and treatment of dental caries and periodontal diseases.

Adult↗

PubMed1999

Incidence of, and reasons for, tooth mortality among mentally retarded adults during a 10-year period.

The aim of the study was to investigate the reasons for, and incidence of, tooth mortality over a 10-year period in mentally retarded adults receiving regular dental care. The number of teeth present in 115 individuals (mean age in 1984 was 41.0, range 19-83 years) was registered in 1984 and 1994. The reasons for tooth mortality, medication utilization, frequency of dental care visits and cooperation during dental treatment were registered and related to tooth loss. The average incidence of tooth mortality was 3.72 teeth during the 10-year period. The mean number of dental care visits per year was 6.6. Most of the 428 teeth (58%) were lost due to periodontal disease. The preventive dental care given was not sufficient to arrest oral diseases. The data indicate, however, that achievement of cooperation in dental care situations not only makes dental treatment possible, but also leads to a decreased incidence of tooth mortality.

Adult↗

PubMed2002

Development of the vestigial tooth primordia as part of mouse odontogenesis.

The mouse functional dentition comprises one incisor separated from three molars by a toothless diastema in each dental quadrant. Between the incisor and molars, the embryonic tooth pattern also includes vestigial dental primordia, which undergo regression involving apoptosis in their epithelium. Apoptosis appears to play an important role in achieving the specific tooth pattern in the mouse. We documented similarities in the folding mechanism allowing the formation of the dental lamina in mice as well as in reptiles. While further budding on this dental lamina gives rise to many individual simple tooth primordia in crocodiles and lizards, budding morphogenesis of several simple tooth primordia appears to be integrated in the mouse, giving rise to enamel organs of a complex nature. The differentiation of a mammalian tooth germ during both ontogeny and phylogeny might thus include the concrescence (connation) of more primordia, putatively corresponding to simple teeth in mammalian ancestors.

Animals↗

PubMed1986

Lead concentration in deciduous teeth: variation related to tooth type and analytical technique.

A total of 245 newly shed deciduous incisors were obtained from 114 first-grade children who each contributed more than one tooth. Lead concentrations averaged about fivefold higher in circumpulpal dentin than in the whole tooth, but the two parameters showed little correlation. A considerable intraindividual variation in lead levels was partly related to tooth type. In particular, whole upper central incisors contained more lead than did other incisors, but the reverse applied to circumpulpal dentin lead concentration. As whole-tooth and circumpulpal lead concentrations may represent different compartments, tooth lead analyses must be interpreted accordingly. Lead levels in circumpulpal dentin would appear to be a meaningful indicator of long-term lead retention in population studies of children.

Child↗

PubMed1996

Effects of a doubled orthodontic force magnitude on tooth movement and root resorptions. An inter-individual study in adolescents.

The aim of this clinical and histological study was to compare the effects of two controlled, continuous forces of 50 cN (approximately 50 g) and 100 cN (approximately 100 g) on tooth movement and root resorptions. The patients, consisting of 32 individuals, 14 boys and 18 girls (mean age 13.1 years), were divided into four groups of eight individuals. The experimental periods were 4 and 7 weeks. In this investigation, designed as an inter-individual study, only the maxillary first premolar on the right side was utilized. The test tooth was buccally moved by means of a fixed orthodontic appliance. A continuous, weekly controlled force of 50 cN was applied to 16 premolars and a force of 100 cN to the remaining 16 test teeth. The force declined on average 22 per cent during the first week when 50 cN was applied and 27 per cent when 100 cN was applied. Tooth movements were studied on dental casts using a coordinate measuring machine. After 4 and 7 weeks, the tooth movements ranged between 0.5 and 3.4 mm (4 weeks) and 2.7 and 7.1 mm (7 weeks) for 50 cN and between 1.0 and 2.9 mm (4 weeks) and 2.2 and 8.3 mm (7 weeks) for 100 cN, with no significant difference when the force magnitude was doubled. Root resorptions were registered in histological sections in all experimental teeth, more frequently after application of 50 cN compared with 100 cN after 7 weeks. However, the severity of root resorption (extension and depth of resorbed root contour and size of root area on histological sections) did not differ significantly when the applied force was doubled to 100 cN. Great individual variations were noted regarding both the magnitude of tooth movement and amount of root resorption.

Adolescent↗

PubMed2003

Compensatory bone formation in young and old rats during tooth movement.

The aim of this study was to investigate compensatory lingual alveolar bone formation during tooth movement in young and old rats, using the vital bone marker tetracycline. Wistar male rats were separated into the following groups: 13-week-old rats without appliances (13C: control, n = 5), 60-week-old rats without appliances (60C: control, n = 5), 13-week-old rats with appliances (13E: experimental, n = 10), and 60-week-old rats with appliances (60E: experimental, n = 10). The upper first molars of the 13E and 60E groups were moved lingually using fixed appliances. On the third day of tooth movement, tetracycline (TC) was intra-peritoneally injected in all animals including the controls. On the 21st day of tooth movement, the animals were killed and unfixed, and undecalcified, 5-microm frozen frontal sections of the rat first molar areas in both control and experimental groups were examined under light and fluorescent microscopes. In the 13C group without tooth movement, tetracycline labelling lines were obvious in the alveolar crest, apical areas, and interradicular septum, indicating vertical alveolar bone growth. However, in the 60C control group, tetracycline labelling was almost undetectable throughout the alveolar bone. Although the lingual alveolar crest was resorbed from the periodontal side after lingual tooth movement, the sharp, bright labelling lines were still present from the crest to the lingual periosteal alveolar bone in the 13E group. In the 60E group the lines appeared in the lingual periosteal alveolar bone containing the crest, indicating considerable new bone formation. The results indicate that compensatory bone formation occurs in the alveolar crest area and, consequently, alveolar bone height is maintained, even in aged rats.

Aging↗

PubMed2005

Relationship between substance P and interleukin-1beta in gingival crevicular fluid during orthodontic tooth movement in adults.

Metabolism by peptidases plays an important role in modulating the levels of biologically-active neuropeptides, while that of substance P (SP), a component of gingival crevicular fluid (GCF), may potentiate the inflammatory process in orthodontic tooth movement. The aim of this study was two-fold: (1) to investigate GCF levels of SP and interleukin-1beta (IL-1beta) during human orthodontic tooth movement, and (2) to determine the correlation coefficients between SP and IL-1beta levels in the GCF. The subjects were 3 males, with a mean age of 21.3 +/- 2.8 years old, and 6 females, with a mean age of 23.1 +/- 2.4 years, undergoing orthodontic movement of a single tooth, with the contralateral tooth used as the control. GCF was sampled at the control and treatment (compression) sites before and 1, 4, 8, 24, 72, 120, and 168 hours after initiation of orthodontic treatment. Prevention of plaque-induced inflammation allowed assessment of the dynamics of mechanically stimulated SP and IL-1beta levels in the GCF, which were determined using enzyme-linked immunosorbent assay (ELISA) kits. GCF levels of SP and IL-1beta for the treated teeth were significantly higher (P < 0.001) than for the corresponding control teeth from 8 to 72 hours, and peaked at 24 hours. These results show that the amounts of SP and IL-1beta in GCF increase with orthodontic tooth movement, and indicate that such increases may be involved in inflammation in response to mechanical stress.

Adult↗

PubMed2006

The tissue, cellular, and molecular regulation of orthodontic tooth movement: 100 years after Carl Sandstedt.

The first experimental investigation of orthodontic tooth movement was published by Sandstedt in 1904-1905. After 100 years, there is a good understanding of the sequence of events at both tissue and cellular levels and now the current focus of research is at the molecular level. The techniques of reverse transcription-polymerase chain reaction and in situ hybridization to detect mRNAs of interest have revolutionized tooth movement studies and an expanding list of antibodies and enzyme-linked immunosorbent assays directed against human and animal proteins will facilitate their identification in tissue sections and/or culture supernatants. Nevertheless, although this technology has greatly simplified research for the clinical and laboratory investigator, message is not always translated into protein, and the presence of a protein does not necessarily mean it is biologically active. In vivo and in vitro methods have been widely used in tooth movement studies. However, data from in vitro models, in which the mechanical stimulus can be carefully controlled (tension versus compression; intermittent versus continuous), should be correlated with in vivo data from animal models. The current evidence suggests that downstream from the initial mechanotransduction event at focal adhesions which link the extracellular matrix to the cytoskeleton, mechanically induced remodelling is mediated by a complex feedback mechanism involving the synthesis of cytokines such as interleukin-1 (IL-1), IL-6, and receptor activator of nuclear factor k B ligand by cells of the osteoblast and/or fibroblast lineages. These in turn act in an autocrine/paracrine fashion to regulate the expression of transcription factors, cytokines, growth factors, enzymes, and structural molecules involved in the differentiation, proliferation, and function of mesenchymal and other cell types. Contrary to the impression gained from the literature, tooth movement is not confined to events within the periodontal ligament. Orthodontic tooth movement involves two interrelated processes: (1) deflection or bending of the alveolar bone and (2) remodelling of the periodontal tissues.

Alveolar Process↗

PubMed2001

A validated finite element method study of orthodontic tooth movement in the human subject.

The aim of the study was to develop a 3D computer model of the movement of a maxillary incisor tooth when subjected to an orthodontic load. A novel method was to be developed to directly and accurately measure orthodontic tooth movement in a group of human volunteers. This was to be used to validate the finite element-based computer model. The design took the form of a prospective experiment at a laboratory at the University of Wales in 1996/7. A laser apparatus was used to sample tooth movement every 0.01 seconds over a 1-minute cycle for 10 healthy volunteers, whilst a constant 0.39 N load was applied. This process was repeated on eight separate occasions and the most consistent five readings taken for each subject. Data were used to calculate the physical properties of the periodontal ligament (PDL). The data gleaned by this method were used to validate the 3D FEM model. This was formed of 15,000 four-noded tetrahedral elements. Tooth displacements ranged from 0.012 to 0.133 mm. An appropriate elastic modulus of 1 N/mm(2) and Poisson's Ratio of 0.45 was derived for the PDL. Strain analysis, using the model, suggested that a maximum PDL strain of 4.77 x 10(-3) was recorded at the alveolar crest, while the largest apical strain recorded was 1.55 x 10(-3). The maximum strains recorded in the surrounding alveolar bone were 35 times less than for the PDL. A novel method for direct measurement of PDL physical properties in the human subject has been developed. The validated FEM model lends further evidence that the PDL is the main mediator of orthodontic tooth movement.

Adult↗