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PubMed1983

Effects of sympathetic nerve activity on changes in the position of the rabbit incisor tooth evoked by acute alterations in arterial blood pressure.

The influence of the sympathetic innervation of periodontal blood vessels on the responses of the upper incisor tooth to sudden changes in mean arterial pressure was studied in 15 anaesthetized rabbits. Changes in axial position of the tooth were measured by ultrasonic transit time technique. With intact sympathetic nerves, the tooth showed small, if any, intrusive movements in response to 6-42 mm Hg reductions in arterial pressure evoked by stimulation of the aortic baroreceptor nerve. When exposed to similar periods of hypovolaemic hypotension, the intrusions were, on an average, 1 micron larger (p less than 0.01). After bilateral sectioning of the cervical sympathetic nerves, tooth intrusions in response to both types of pressure reduction became more marked, as did the extrusive movements evoked by abrupt increases in aortic pressure (produced by inflation of intra-aortic balloon). After sympathectomy, a 19 +/- 6 mm Hg rise in pressure caused extrusions of 6 +/- 3 microns, or 2 microns more than before the sympathectomy (p less than 0.01). The results suggest that the activity in sympathetic nerves to periodontal blood vessels may be inhibited by central nervous mechanisms and that the sympathetic innervation of the periodontal vasculature serves to minimize changes in tooth position brought on by sudden alterations in arterial pressure.

Animals↗

PubMed1996

Stimulation of murine tooth development in organotypic culture by the neurotransmitter serotonin.

Serotonin (5-hydroxytryptamine; 5-HT) uptake sites are transiently expressed in craniofacial epithelia and mesenchyme, including the tooth germ, during mouse embryogenesis. Based on malformations and patterns of cell proliferation and death in cultured mouse embryos exposed to 5-HT uptake inhibitors, it has been hypothesized that 5-HT acts as a dose-dependent morphogenetic signal for craniofacial development. The present study was designed to investigate the effect of 5-HT on tooth-germ formation in serum-free mandibular explant cultures prepared from embryonic day-13 (plug day = embryonic day-1) mouse embryos. In the absence of serum or a 5-HT supplement, tooth germs develop only to the bud stage in these cultures. When explants were cultured for 8 days in a defined medium supplemented with 5-HT, late bell-stage tooth germs were stimulated to develop in a dose-dependent manner. This effect was reversed by addition of the 5-HT uptake inhibitor fluoxetine. Anti-5-HT immunocytochemistry demonstrated specific uptake of 5-HT by developing tooth germ and mandibular epithelium, which could also be blocked by fluoxetine. These results suggest that 5-HT may regulate dental differentiation, and that intracellular uptake is required for this action.

Animals↗

PubMed1987

Localization and quantitation of 125I-epidermal growth factor binding in mouse embryonic tooth and other embryonic tissues at different developmental stages.

We have shown earlier that epidermal growth factor (EGF) inhibits morphogenesis and cell differentiation in mouse embryonic teeth in organ culture. This inhibition depends on the stage of tooth development so that only teeth at early developmental stages respond to EGF (A-M. Partanen, P. Ekblom, and I. Thesleff (1985) Dev. Biol. 111, 84-94). We have now studied the quantity and pattern of EGF binding in teeth at various stages of development by incubating the dissected tooth germs with 125I-labeled EGF. Although the quantity of 125I-EGF binding per microgram DNA stays at the same level, localization of 125I-EGF binding by autoradiography reveals that the distribution of binding sites changes dramatically. In bud stage the epithelial tooth bud that is intruding into the underlying mesenchyme has binding sites for EGF, but the condensation of dental mesenchymal cells around the bud does not bind EGF. At the cap stage of development the dental mesenchyme binds EGF, but the dental epithelium shows no binding. This indicates that the dental mesenchyme is the primary target tissue for the inhibitory effect of EGF on tooth morphogenesis during early cap stage. During advanced morphogenesis the binding sites of EGF disappear also from the dental papilla mesenchyme, but the dental follicle which consists of condensed mesenchymal cells surrounding the tooth germ, binds EGF abundantly. We have also studied EGF binding during the development of other embryonic organs, kidney, salivary gland, lung, and skin, which are all formed by mesenchymal and epithelial components. The patterns of EGF binding in various tissues suggest that EGF may have a role in the organogenesis of epitheliomesenchymal organs as a stimulator of epithelial proliferation during initial epithelial bud formation and branching morphogenesis. The results of this study indicate that EGF stimulates or maintains proliferation of undifferentiated cells during embryonic development and that the expression of EGF receptors in different organs is not related to the age of the embryo, but is specific to the developmental stage of each organ.

Animals↗

PubMed1991

Expression of syndecan gene is induced early, is transient, and correlates with changes in mesenchymal cell proliferation during tooth organogenesis.

Syndecan is an integral cell surface proteoglycan which contains an extracellular matrix-binding domain and a cytoskeleton-associated domain and may therefore transfer changes in the extracellular environment to cellular behavior. Changes in syndecan gene expression during embryonic and early postnatal mouse tooth development were analyzed by in situ hybridization and compared with the distribution of syndecan core protein and cell proliferation studied by immunohistochemistry. Syndecan RNA became accumulated in the condensing mesenchymal cells around the invaginating epithelial tooth bud during early development, and this accumulation became more intense when morphogenesis advanced to the cap stage. During the bell stage, when the cuspal pattern of the tooth is established, syndecan transcripts were lost, and RNA was not detected in the terminally differentiated or postmitotic odontoblasts. In the epithelium, syndecan RNA was intensely expressed in the invaginating epithelial bud, but the expression was reduced during the cap and bell stages. However, local stimulation in syndecan gene expression was observed in the epithelial preameloblasts immediately preceding their terminal differentiation into ameloblasts, which was accompanied by a complete loss of transcripts. There was a close correlation between the changes in syndecan transcripts and the distribution of syndecan core protein. Furthermore, analysis of cell proliferation by immunohistochemical detection of BrdU incorporation revealed that in the mesenchyme, but not in the epithelium, syndecan was intensely expressed by proliferating cells. The analysis of mRNA by Northern blot indicated that the transcripts in mesenchymal and epithelial cells were of similar size. In the slot-blot analysis the changes in syndecan transcripts correlated with the overall changes observed in the in situ hybridization analysis. The role of tissue interactions in the regulation of the syndecan gene was studied by using tissue recombination cultures of separated epithelial and mesenchymal components of the early tooth germ. The in situ hybridization and Northern blot analysis of these explants showed that the expression was increased in the mesenchyme cultured in contact with the epithelium. Our results indicate that syndecan gene expression in the embryonic tooth mesenchyme is induced by epithelial-mesenchymal interactions and thereafter expressed stage-dependently and transiently by the differentiating cells during organogenesis. The association of syndecan expression with mesenchymal cell proliferation raises the possibility that, in addition to behaving as a matrix receptor, syndecan may have a role in controlling growth and that syndecan may have different functions in epithelial and mesenchymal cells.

Animals↗

PubMed1990

A comparison of new and conventional methods for quantification of tooth color.

Tooth color is caused by volume reflection, that is, passage of incident light through the tooth followed by backward emergence. This passage is concurrent with sideward displacement of photons that, in effect, influences the result of usual instrumental methods of determining tooth color. This problem is overcome by the use of large-field illumination and small-field observation. A fiber-optics colorimeter based on this principle is described. The color observed through two holes in a double box was visually matched by subtractive adjustment of the illuminating color in one box, whereas the other box showed the central part of the tooth diffusely illuminated by illuminant C light. This colorimeter was tested on wet, extracted human incisors in the tooth arch of a phantom-head. Results were compared with a visual standard-strip method described previously and with a conventional spectrophotometer. It was concluded that the fiber-optics colorimeter is a promising instrument, although technical improvement is necessary.

Acrylic Resins↗

PubMed1985

Tooth discoloration induced by dental materials.

Tooth discoloration after endodontic treatment is frequently attributed to drugs and filling materials. In this in vitro study the staining potential of various dental materials was investigated by means of a visual method to determine tooth color. Extracted human premolars were prepared, and the following materials were introduced into the pulp cavities: Cavit, Durelon, Dycal, Fletcher's cement, IRM, AH26-silver free, gutta-percha, Duo Percha, Fuji ionomer, and zinc phosphate cement. Before the materials were applied, the original tooth color was assessed on the external buccal tooth surfaces. Further color determinations were undertaken at regular intervals for 6 months after the materials were introduced. Durelon, Fuji ionomer, Fletcher's cement, and zinc phosphate cement did not induce measurable tooth discoloration. Cavit, Dycal, gutta-percha, and IRM caused a mild stain. For the teeth filled with AH26-silver free and Duo Percha, a moderate discoloration was recorded.

Color↗

PubMed1986

Tooth discoloration induced by endodontic sealers.

Endodontic therapy often results in discoloration of the tooth crown. The main causes are blood, necrotic pulp tissue, and endodontic materials. The staining potentials of various materials were examined in vitro by means of a visual method for tooth color determination. Extracted premolars were prepared, and the following sealers were introduced into the pulp cavities: Zinc oxide eugenol cement, Grossman's cement, AH26, Diaket, N2, Riebler's paste, Tubliseal, and Endomethasone. Before the sealers were applied, the original tooth colors were assessed on the external buccal tooth surfaces. Further color determinations were carried out at regular intervals up to 6 months after introduction of the sealers. Each material induced measurable tooth discoloration within 3 weeks. Riebler's paste caused the most severe discoloration while Diaket caused a mild stain. The other materials produced intermediate discolorations between those of Riebler and Diaket.

Administration, Topical↗

PubMed1993

Small primary tooth-crown size in low birthweight children.

As part of a longitudinal study of dental development in a group of low birthweight children (LBW), study models of 72 children at age 7 years were measured to determine the tooth-crown size of primary molars and canines and to compare the findings with equivalent measurements in 60 normal birthweight (NBW) controls. Mesiodistal (length) and buccolingual (width) dimensions were measured manually, using dial calipers. Primary canines and molars were smaller in the LBW than the controls, with significance values ranging from P < 0.001 for the mesiodistal dimension of maxillary and mandibular canine (> 4% difference) to a non-significant difference P < 0.2 for the buccolingual dimension mandibular first primary molar (1.8% difference). Within the LBW group there was a positive correlation between birthweight and mesiodistal tooth size. Small primary tooth size in LBW children may be influenced by both genetic and environmental factors. The shorter prenatal growth period and poor perinatal and early postnatal development may influence the developing deciduous dentition. Small primary tooth-crown size, associated with LBW, should be considered in all population studies of tooth size.

Child↗

PubMed1990

The accuracy of simple ordinal scoring of tooth attrition in age assessment.

Tooth wear is frequently used as a method of ageing skeletal remains. Fundamental to this method is the ability to measure the amount of tooth wear. The Brothwell chart based on the Miles method of ageing, uses simple ordinal scoring and is frequently used by archeologists. The purpose of the present investigation was to evaluate the accuracy of simple ordinal scoring in recording tooth wear and ageing skulls. A group of Chinese skulls of known age at death was used. The age range was from 16 to 60 years. A single score per molar tooth was used to record occlusal wear. The data were analysed by regression methods using BMDP statistical software. The results showed that molar tooth wear continues throughout the life of the individual. The first molar teeth wear significantly more quickly than do second molar teeth. Use of a simple ordinal score method for recording wear gives an inaccurate estimate of an individual skull's age at death with a very wide 95% confidence interval.

Adolescent↗

PubMed1989

Leukotrienes in orthodontic tooth movement.

Prostaglandins (PGs) and leukotrienes (LTs) are products of arachidonic acid conversion. PGs have an established role in mediating orthodontic tooth movement. The role of LTs in modulating or mediating orthodontic tooth movement was investigated in this study. One hundred thirty-two Sprague-Dawley rats were used; the animals weighed 300 to 400 gm with equal numbers of male and female rats. They were divided into five main groups of 24 animals each and a sham group of 12 animals. An orthodontic appliance was placed and activated on all the animals except the sham group; in this group the appliances were not active. Each main group was given one of the following treatments daily: distilled water, 5% gum arabic solution, PG synthesis inhibitor indomethacin, LT synthesis inhibitor AA861, and a combination of both drugs. Each group was divided into six subgroups of four animals; the animals were killed at either 1, 3, 5, 7, 10, or 14 days, and tooth movement measured. The three sham subgroups received distilled water and were killed at 1, 7, or 10 days. The first maxillary molar (the moved tooth) and surrounding tissues were removed from all animals in the sham group and the subgroups killed at 1, 7, and 10 days in the gum arabic solution group and the LT synthesis inhibitor group. Prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) were extracted, measured with radioimmunoassay (RIA), and standardized per milligram of protein in the sample. A significant inhibition of tooth movement occurred beginning on day 7 in the indomethacin, AA861, and combination groups; there was no significant difference among these groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

The effect of corticosteroid-induced osteoporosis on orthodontic tooth movement.

The purpose of this research was to study the effect of corticosteroid-induced osteoporosis on orthodontic tooth movement and relapse. Sixteen 3-month-old New Zealand white rabbits were divided into four equal groups, two treatment and two control. All treatment rabbits were administered daily injections of 15 mg/kg cortisone acetate for 4 days before and during the experimental period. An orthodontic appliance delivering a mesial force of 4 ounces was placed on the maxillary left first molar of all animals. For all groups, measurements of active tooth movement were made after 4, 7, 11, and 14 days. For two of the groups, appliances were removed on day 14, and additional measurements of relapse were made through day 21. With the use of radiodensitometric readings of the humerus bone and histology of the maxilla, osteoporosis was demonstrated in the treatment animals. Mean incremental and cumulative active tooth movement was three to four times greater (p < 0.0001) in the treatment rabbits than in the controls. The treatment group in which relapse was measured demonstrated 100% relapse on day 18, whereas the control group relapsed at a much lesser rate through day 21 and never achieved 100% relapse. Histologic findings appeared to support tooth movement results. In conclusion, the results of this study indicate that rabbits subjected to corticosteroid-induced osteoporosis undergo significantly more rapid orthodontic tooth movement and subsequent relapse than control animals.

Absorptiometry, Photon↗

PubMed2004

Optimum force magnitude for orthodontic tooth movement: a mathematic model.

The aim of this study was to develop a mathematic model to describe the relationship between magnitude of applied force and rate of orthodontic tooth movement. Initially, data were extracted from experimental studies in dogs (beagles), in which controlled, standardized forces were used to move mandibular second premolars distally. Curve-fitting by nonlinear regression analysis provided an equation describing the relationship between force magnitude and rate of tooth movement in beagles. A similar equation was subsequently used to analyze the limited available data from the literature on human canine retraction. The maximum rates of tooth movement in humans and dogs are very similar. A threshold for force magnitude that would switch on tooth movement could not be defined. The model showed that a wide range of forces can be identified, all of which lead to a maximum rate of tooth movement.

Animals↗

PubMed2004

Immunohistochemical localization of alphavbeta3 integrin receptor during experimental tooth movement.

During orthodontic treatment, multinucleated clast cells carry out the resorption of mineralized tissues. Adhesion of clast cells to the mineralized tissues is mediated by transmembrane cell-surface glycoproteins called integrins, specifically by the alphavbeta3 integrin, which plays an important role in the process of bone resorption. The role of the alphavbeta3 integrin in bone resorption leading to osteoporosis has been demonstrated, but its role in alveolar bone and root resorption during orthodontic tooth movement is unknown. This study examined the expression of the alphavbeta3 integrin during experimental tooth movement. Tooth movement was achieved in 16 male Sprague-Dawley rats (each weighing 120-200 g) with elastic bands between their maxillary first and second molars. The molar-bearing segments were dissected and processed for histologic and immunohistochemical examination. The expression of alphavbeta3 integrin was examined with 2 primary antibodies: a polyclonal anti-alphav integrin subunit antibody and a polyclonal anti-beta3 integrin subunit antibody. Negative controls were similarly processed but without incubation with primary antibodies. The alphavbeta3 integrin was expressed both by osteoclasts associated with alveolar bone resorption and by odontoclasts associated with root resorption during experimental tooth movement. Furthermore, the beta3 integrin subunit was expressed by the epithelial rests of Malassez in the periodontal ligament. Negative controls did not show immunolabeling. The alphavbeta3 integrin adhesion receptor is expressed during experimental tooth movement and might be involved in the process of mineralized tissue resorption and the functions of the epithelial rests of Malassez.

Alveolar Process↗

PubMed2006

Aspirin, acetaminophen, and ibuprofen: their effects on orthodontic tooth movement.

INTRODUCTION: Orthodontic patients often take analgesics for pain during treatment. But various analgesics have different capacities to inhibit prostaglandins, and these differences might affect tooth movement. The purposes of this study were to determine by direct measurement the effects that acetylsalicylic acid, ibuprofen, and acetaminophen have on orthodontic tooth movement in rats and to evaluate histologically the differences in bone resorption in the pressure area in rats treated with these analgesics. METHODS: Thirty-six adult male Wistar rats were divided in 4 groups of 9 each. Orthodontic appliances were placed on the rats' incisors. In the 3 experimental groups, analgesics were diluted in reverse osmosis water and delivered via a gastric tube: 100 mg/kg acetylsalicylic acid, or 30 mg/kg ibuprofen, or 200 mg/kg acetaminophen. Control animals received only the reverse osmosis water. At the end of the experimental period, the rats were killed and histological examinations were performed. RESULTS: Analysis of variance showed statistically significant differences between the control group, which was given reverse osmosis water, and the groups given aspirin and ibuprofen. There were also statistically significant differences between the acetaminophen group and the ibuprofen and aspirin groups, respectively. There was no significant difference between the acetaminophen group and the control group, or between the aspirin and ibuprofen groups. Tooth movement was similar in the groups. CONCLUSIONS: The results indicate that nonsteroidal anti-inflammatory analgesics such as aspirin and ibuprofen diminish the number of osteoclasts, probably by inhibiting the secretion of prostaglandins, thereby reducing orthodontic tooth movement. Acetaminophen did not affect orthodontic tooth movement in rats, and it might be the analgesic of choice for treating pain associated with orthodontic treatment.

Acetaminophen↗

PubMed2006

Levels of matrix metalloproteinases 1 and 2 in human gingival crevicular fluid during initial tooth movement.

INTRODUCTION: During orthodontic treatment, the early response of periodontal tissues to mechanical stress involves several metabolic changes that allow tooth movement. Many studies have evaluated these modifications through the analysis of various metabolites released into gingival crevicular fluid (GCF). The purpose of this investigation was to evaluate matrix metalloproteinase (MMP)-1 and MMP-2 in the GCF of human teeth exposed to orthodontic force on both the tension and compression sides in the initial phase of orthodontic tooth movement. METHODS: GCF samples were obtained from 11 healthy orthodontic patients (8 girls, 3 boys; age, 13-15 years; mean, 13.9 years) who needed their 4 first premolars extracted for orthodontic reasons. In each patient, the left maxillary canine having the fixed orthodontic appliance was used as the test tooth, and its antagonist, with no appliance, was the control tooth. Orthodontic force was applied by using a Sentalloy coil-spring (GAC International, Bohemia, NY) of 150 g. The GCF sampling on the mesiobuccal and distobuccal aspects of each experimental and control tooth was performed at specific times up to 8 hours with paper strips. Processing was carried out with western blot analysis to detect MMP-1 and MMP-2 levels on the compression and tension sides. RESULTS: Compression force induced a significant increase of MMP-1 protein after 1 hour; the increase lasted until the third hour of force application and disappeared thereafter. The tension force induced significantly increased levels of the MMP-1 protein after just 1 hour of force application. MMP-2 protein was induced by compression and increased significantly in a time-dependent fashion, reaching a peak after 8 hours of force application. On the tension side, MMP-2 was significantly increased after 1 hour but gradually returned to basal levels within 8 hours. CONCLUSIONS: Orthodontic forces affect both MMP-1 and MMP-2 protein levels on the compression and the tension sides, although to different extents, whereas MMP-1 and MMP-2 protein levels change in a time-dependent fashion.

Adolescent↗

PubMed2005

The 3rd international intercomparison on EPR tooth dosimetry: Part 1, general analysis.

The objective of the 3rd International Intercomparison on Electron Paramagnetic Resonance (EPR) Tooth Dosimetry was the evaluation of laboratories performing tooth enamel dosimetry below 300 mGy. Participants had to reconstruct the absorbed dose in tooth enamel from 11 molars, which were cut into two halves. One half of each tooth was irradiated in a 60Co beam to doses in the ranges of 30-100 mGy (5 samples), 100-300 mGy (5 samples), and 300-900 mGy (1 sample). Fourteen international laboratories participated in this intercomparison programme. A first analysis of the results and an overview of the essential features of methods applied in different laboratories are presented. The relative standard deviation of results of all methods was better than 27% for applied doses in the range of 79-704 mGy. In the analysis of the unirradiated tooth halves 8% of the samples were identified as outliers with additional absorbed dose above background dose.

Benchmarking↗

PubMed2004

Origin and developmental fate of vestigial tooth primordia in the upper diastema of the field vole (Microtus agrestis, Rodentia).

OBJECTIVE: Odontogenesis in voles is a convenient model to test hypotheses on tooth development generated from investigations in the mouse. Similar to other rodents, the functional dentition of the vole includes a toothless diastema. At its mesial end, a vestigial tooth bud has been found in the upper jaw of vole embryos. The aim of this study was to analyse the developmental dynamics of vestigial tooth structures in the upper diastema of the field vole and to compare it with the situation in the mouse. DESIGN: The development of odontogenic structures in the upper diastema of the field vole was investigated using serial histological sections and three-dimensional (3D) computer-aided reconstruction. RESULTS: A transient continuous dental lamina in the upper diastema of the field vole extended mesially to the first molar primordium, but was not continuous with the dental lamina in the incisor region. At its mesial limit, a large vestigial tooth primordium was regularly present. A further distinct vestigial bud was located mesially to the first molar primordium. The segmentation of the dental lamina suggested a potential to give rise to further vestiges in the upper diastema of the vole. CONCLUSIONS: In the prospective diastema of the vole exists as in the mouse a continuous dental lamina. Beside the prominent vestigial tooth bud in the mesial diastema, a further large bud was transiently located in front of the molars. The incorporation of dental epithelium into the first upper molar (M(1)) primordium in the vole differs from that in the mouse.

Animals↗

PubMed2004

The expression pattern of hyaluronan synthase during human tooth development.

In previous studies, hyaluronan (HA) and its major cell surface receptor CD44 have been suggested to play an important role during tooth development. HA synthases (HASs) are the enzymes that polymerize hyaluronan. Data on the expression pattern of HASs during tooth development is lacking and the aim of the present study was to investigate the localisation of HAS by immunohistochemistry in human tooth germs from different developmental stages. The distribution pattern of HAS in the various tissues of the "bell stage" tooth primordia corresponded to that of hyaluronan in most locations: positive HAS immunoreactivity was observed in the dental lamina cells, inner- and outer-enamel epithelium. On the stellate reticulum cells, moderate HAS signal was observed, similar to the layers of the oral epithelium, where faint HAS immunoreactivity was detected. At the early phase of dental hard tissues mineralization, strong HAS immunoreactivity was detected in the odontoblasts and their processes, as well as in the secretory ameloblasts and their apical processes and also, the pulpal mesenchymal cells. The HAS signals observed in odontoblasts and ameloblasts gradually decreased with age. Our results demonstrate that hyaluronan synthesised locally by different dental cells and these results provide additional indirect support to the suggestion that HA may contribute both to the regulation of tooth morphogenesis and dental hard tissue formation.

Ameloblasts↗