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PubMed2005

Retrospective analysis of factors influencing the eruption of delayed permanent incisors after supernumerary tooth removal.

AIM: This was to assess the predictability of eruption of delayed permanent incisors after supernumerary removal and creation of adequate space, in relation to: root maturity, degree of vertical impaction, and degree of angulation of impaction. METHODS: The dental records of children with supernumerary teeth delaying the eruption of permanent incisors were analysed. The type of a supernumerary tooth, its location and position were recorded, along with the stage of root maturation, angulation and vertical distance of impaction of the permanent incisor. At the initial surgery, the unerupted supernumerary tooth and any retained primary incisors were removed. The unerupted permanent incisor was not exposed. If necessary, the maxillary primary canines were removed to create sufficient space for eruption of the delayed permanent tooth. A secondary surgical procedure was planned after 18 months if there was no significant progress of the permanent tooth towards eruption. STATISTICS: All data were entered onto a Microsoft Excel spread sheet and analysed using Fisher's Exact Tests throughout due to the small numbers. RESULTS: Sixty-six supernumerary teeth were removed, 22 from boys and 44 from girls with ages ranging from 6 to 10 years 6 months at the time of surgery. Primary canines were extracted in 59.1% of cases. Spontaneous eruption occurred in 89.4% of delayed permanent teeth. The mean time to eruption was 9.2 months (median = 7 months). There was no statistically significant association between tooth eruption and root maturity or the degree of vertical impaction. There was an association between eruption and the degree of the angle of impaction of the permanent incisor (p<0.05). CONCLUSION: The majority of delayed permanent teeth erupt spontaneously if sufficient space is available or created at the time of removal of the unerupted supernumerary. The angulation of impaction of the permanent incisor is associated with a delay in eruption.

Child↗

PubMed2000

Effects of low-energy laser irradiation on bone remodeling during experimental tooth movement in rats.

BACKGROUND AND OBJECTIVE: Low-energy laser irradiation has many anabolic effects such as the acceleration of bone formation. However, its effects on tooth movement, performed by bone resorption and formation, have not been well characterized. STUDY DESIGN/MATERIALS AND METHODS: A total of 10 g of orthodontic force was applied to rat molars to cause experimental tooth movement. A Ga-Al-As diode laser was used to irradiate the area around the moved tooth, and after 12 days, the amount of tooth movement was measured. Calcein was injected subcutaneously to label the newly formed alveolar bone for quantitative analysis. Immunohistochemical staining of proliferating cell nuclear antigen was performed to evaluate cellular proliferation. TRAPase staining was also performed to facilitate the identification of osteoclasts. RESULTS: In the laser irradiation group, the amount of tooth movement was significantly greater (1. 3-fold) than that of the nonirradiation group in the end of the experiment. The amount of bone formation and rate of cellular proliferation in the tension side and the number of osteoclasts in the pressure side were all significantly increased in the irradiation group when compared with the nonirradiation group (P < 0. 01). CONCLUSION: These findings suggest that low-energy laser irradiation can accelerate tooth movement accompanied with alveolar bone remodeling.

Alveolar Process↗

PubMed1996

Integrin subunit expression associated with epithelial-mesenchymal interactions during murine tooth development.

The initial information for patterning of early tooth development resides in the epithelium. Later, this is shifted to the mesenchyme. The process is governed by multiple epithelial-mesenchymal interactions. Integrins are cell surface receptors for extracellular matrix components. Expression of the beta 5 integrin subunit alternates between epithelium and mesenchyme during early tooth development (Yamada et al. [1994] Int. J. Dev. Biol. 38: 553-556). By immunofluorescence and in situ hybridization we show here a remarkably similar oscillating expression pattern of the alpha v integrin subunit. This subunit is known to associate with beta 5, and we therefore suggest that integrin alpha v beta 5 is involved in epithelial-mesenchymal interactions during tooth development. We also demonstrate that the developing tooth epithelium expresses the alpha 6, beta 1 and beta 4 subunits. The laminin receptors alpha 6 beta 1 and alpha 6 beta 4 may thus in part mediate the effect of basement membranes on tooth epithelial development. Interestingly, the enamel knot region expressed very little alpha 6 integrin subunit, whereas some expression was seen transiently in the condensing mesenchyme. During early tooth development, integrins possessing the alpha 6 subunit might also be involved in cell-cell interactions independently of laminins.

Animals↗

PubMed1997

Expression patterns of bone morphogenetic proteins (Bmps) in the developing mouse tooth suggest roles in morphogenesis and cell differentiation.

Bone morphogenetic proteins (BMP) are secretory signal molecules which have a variety of regulatory functions during morphogenesis and cell differentiation. Teeth are typical examples of vertebrate organs in which development is controlled by sequential and reciprocal signaling between the epithelium and mesenchyme. In addition, tooth development is characterized by formation of mineralized tissues: the bone-like dentin and cementum as well as epithelially derived enamel. We have performed a comparative in situ hybridization analysis of the expression of six different Bmps (Bmp-2 to Bmp-7) starting from initiation of tooth development to completion of crown morphogenesis when dentine and enamel matrices are being deposited. Bmps-2, -4, and -7 were frequently codistributed and showed marked associations with epithelial-mesenchymal interactions. Their expression shifted between the epithelium and mesenchyme starting from the stage of tooth initiation. They were subsequently expressed in the enamel knot, the putative signaling center regulating tooth shape. Their expression domains prior to and during the differentiation of the dentine-forming odontoblasts and enamel-forming ameloblasts was in line with functions in regulation of cell differentiation and/or secretory activities of the cells. The expression of Bmp-3 was confined to mesenchymal cells, in particular to the dental follicle cells which give rise to the cementoblasts, forming the hard tissue covering the roots of teeth. Bmp-5 was expressed only in the epithelial ameloblasts. It was upregulated as the cells started to polarize and intense expression continued in the secretory ameloblasts. Bmp-6 was expressed only weakly in the dental mesenchyme during bud and cap stages. Our results are in line with regulatory functions of Bmps at all stages of tooth morphogenesis. Bmps-2, -4, and -7 are conceivably parts of signaling networks regulating tooth initiation and shape development. They as well as Bmp-5 may be involved in the induction and formation of dentine and enamel, and Bmp-3 in the development of cementum. The remarkable overlaps in the expression domains of different Bmp genes may implicate functional redundancy and/or formation of active heterodimers between different BMPs.

Animals↗

PubMed1999

Msx1 is required for the induction of Patched by Sonic hedgehog in the mammalian tooth germ.

We have used the mouse developing tooth germ as a model system to explore the transmission of Sonic hedgehog (Shh) signal in the induction of Patched (Ptc). In the early developing molar tooth germ, Shh is expressed in the dental epithelium, and the transcripts of Shh downstream target genes Ptc and Gli1 are expressed in dental epithelium as well as adjacent mesenchymal tissue. The homeobox gene Msx1 is also expressed in the dental mesenchyme of the molar tooth germ at this time. We show here that the expression of Ptc, but not Gli1, was downregulated in the dental mesenchyme of Msx1 mutants. In wild-type E11.0 molar tooth mesenchyme SHH-soaked beads induced the expression of Ptc and Gli1. However, in Msx1 mutant dental mesenchyme SHH-soaked beads were able to induce Gli1 but failed to induce Ptc expression, indicating a requirement for Msx1 in the induction of Ptc by SHH. Moreover, we show that another signaling molecule, BMP4, was able to induce Ptc expression in wild-type dental mesenchyme, but induced a distinct expression pattern of Ptc in the Msx1 mutant molar mesenchyme. We conclude that in the context of the tooth germ Msx1 is a component of the Shh signaling pathway that leads to Ptc induction. Our results also suggest that the precise pattern of Ptc expression in the prospective tooth-forming region is controlled and coordinated by at least two inductive signaling pathways.

Animals↗

PubMed1996

Molecular mechanisms of cell and tissue interactions during early tooth development.

BACKGROUND: Morphogenesis and cell differentiation during the development of all organs, including the tooth, are regulated by interactions between cells and tissues. The developing tooth is one of the organs in which the molecular mechanisms of such interactions are starting to be elucidated. RESULTS: Homotypic cell interactions take place between cells of the same developmental history, and they are a central mechanism in the formation of mesenchymal cell condensates during the bud stage of tooth development. Syndecan-1, a cell surface heparan sulfate proteoglycan, is transiently expressed in the dental mesenchyme and may regulate dental mesenchymal cell condensation. It binds tenascin, a matrix glycoprotein abundant in dental mesenchyme, suggesting involvement of cell-matrix interactions. Syndecan also binds growth factors, and its association with cell proliferation in the dental mesenchyme suggests roles in the regulation of cell number in the condensing cells. Inductive interactions between the epithelial and mesenchymal tissues regulate tooth development at all stages. In the early dental mesenchyme, the expression of several molecules, including syndecan and tenascin, are regulated by the epithelium. There is evidence that growth factors act as diffusible signals mediating these interactions. BMP-2 and BMP-4 (bone morphogenetic proteins), which belong to the TGF beta superfamily, are expressed in the early dental epithelium, and their effects on the dental mesenchyme mimic those of the epithelium. In particular, BMPs induce the expression of the homeobox-containing transcription factors Msx-1 and Msx-2 in the dental mesenchyme. CONCLUSIONS: Based on current knowledge about the molecular changes accompanying tooth development and the results of experimental studies, we present a model for molecular regulation of early tooth development.

Animals↗

PubMed2005

Longitudinal analysis of deciduous tooth emergence: IV. Covariate effects in Japanese children.

Emergence of the deciduous teeth is generally considered to be robust to moderate environmental insults, malnutrition, and disease. Consequently, deciduous tooth emergence has been used to assess growth and development and for age estimation in children. In this paper, we examine the way in which nutritional status and other covariates affect deciduous tooth emergence in a sample of 114 Japanese children born in Tokyo in 1914 and 1924. Parametric survival analysis was used to quantify the effects of nutritional status, breastfeeding behavior, and sex on the hazard of deciduous tooth emergence. Children of poor nutritional status exhibited significantly delayed emergence of all deciduous teeth, with effects that ranged from 14-29% increases in mean emergence times. Children of medium nutritional status exhibited increases in mean emergence times of 5-9% for the canines and lower molars, and 13-17% for the incisors. Partial breastfeeding had no effect on tooth emergence, but children who were not breastfed at all showed delayed emergence of the upper incisors. No significant sex differences in emergence were found. The findings contradict the idea that moderate malnutrition has little effect on deciduous tooth emergence. Furthermore, nutritional differences may account for some of the observed differences among populations in the timing of tooth emergence.

Breast Feeding↗

PubMed1978

Heritability of permanent tooth size.

The aim of this investigation was to quantify the relative contributions of genetic and environmental influences to the observed variability of permanent tooth size in a group of Australian Aboriginals. Tooth size data were obtained from dental casts of Aboriginals living at Yuendumu in the Northern Territory of Australia. The custom of polygyny practised by these people enabled the analysis of associations between full-siblings and half-siblings. Phenotypic variability of tooth size was partitioned into four variance components; between sides, between fathers, between mothers and between offspring. From these components, the relative genetic and environmental contributions were quantified and heritability estimates for tooth size derived. Additional estimates of heritability were obtained by regression analysis from a small sample of parent-offspring data. Results of the analyses suggested that about 64% of the total variability of permanent tooth size could be attributed to genetic factors, while a further 6% was due to common environment. Although the findings confirm a relatively strong genetic component, they emphasise the importance of non-genetic influences in the determination of tooth size variability.

Australia↗

PubMed1994

Differentiation of periodontal ligament fibroblasts into osteoblasts during socket healing after tooth extraction in the rat.

BACKGROUND: The entire socket after tooth extraction is filled with new bone formed by osteoblasts (Obs), but the origin of these Obs remains unknown. Thus, the proliferation and migration of paravascular and endosteal fibroblastic cells and periodontal ligament (PDL) fibroblasts (Fbs) and their differentiation into Obs during socket healing after extraction of the first maxillary molars of the rat were investigated. METHODS: The proliferative activity and migration of these cells in the sockets after tooth extraction were studied using radioautography and immunohistochemistry after injection of 3H-thymidine and 5-bromo-2'-deoxyuridine (BrdU), respectively. Their morphological changes during differentiation was investigated by transmission electron microscopy. RESULTS: One day after tooth extraction, PDL Fbs were the major cell type in the PDL remnant of the socket. Proliferation was low (labeling index (LI) = approximately 2%) until 16 h after tooth extraction but dramatically increased to a maximum level 1 day postextraction (LI = 23%). Between 1 and 2 days, numerous PDL Fbs in the PDL remnant actively migrated into the coagulum and continued to proliferate. On the basis of the high proliferative activity and small number of cellular organelles responsible for procollagen synthesis, these cells appear immature. At 3 days, Fbs contained more cellular organelles and deposited more collagen fibers as they replaced the coagulum with dense connective tissue and the LI declined. At 4 and 5 days, some of the Fbs began to differentiate into Obs, and the proliferation of Fbs dramatically decreased to baseline values. The migration of PDL Fbs and their differentiation into Obs were investigated by labeling with 3H-thymidine or BrdU 1 day after tooth extraction. Heavily labeled Fbs were observed in the PDL remnant at 1 day, in the coagulum at 2 days, and in the dense connective tissue at 3 days. Labeled Obs associated with new bone were seen 4 days after injection. Endosteal and paravascular Fbs also proliferated, but at a lower level and at later time periods than the PDL Fbs. Surprisingly, endosteal and paravascular Fbs contributed only a small population of Fbs to socket healing. CONCLUSIONS: These results indicate that PDL Fbs after tooth extraction actively proliferative, migrate into the coagulum, form dense connective tissue, and differentiate into Obs which form new bone during socket healing.

Animals↗

PubMed2004

Cellular expression of eve1 suggests its requirement for the differentiation of the ameloblasts and for the initiation and morphogenesis of the first tooth in the zebrafish (Danio rerio).

even-skipped-related (evx) genes encode homeodomain-containing transcription factors that are involved in a series of developmental processes such as posterior body patterning and neurodifferentiation. Although evx1 and evx2 were not reported to be expressed during mammalian tooth development, we present here evidence that eve1, the closest paralog of evx1 in the actinopterygian lineage, is expressed during pharyngeal tooth formation in the zebrafish, Danio rerio. We have performed whole-mount in situ hybridization on zebrafish embryos and larvae ranging from 24 to 192 hours postfertilization (hpf). A detailed analysis of serial sections through the pharyngeal region of whole-mount hybridized and control specimens indicates that only dental epithelial cells express eve1. eve1 transcription was activated at 48 hpf, in the placode of the first tooth (i.e., the initiation site of tooth 4V(1)), and maintained in the dental epithelium throughout morphogenesis. Then, by 72 hpf, eve1 expression was restricted to the differentiating ameloblasts of the enamel organ during early differentiation stage, and this expression decreased as soon as matrix was deposited. In subsequent primary teeth (3 V(1) and 5 V(1)) as well as in their successors (replacement teeth 4V(2), 3V(2), and 5V(2)), eve1 expression was restricted to the differentiating ameloblasts and, again, disappeared when matrix was deposited. Therefore, in the zebrafish, eve1 expression in the pharyngeal region is correlated with two key steps of tooth development: initiation and morphogenesis of the first tooth, and ameloblast differentiation of all developing teeth.

Adaptor Proteins, Signal Transducing↗

PubMed2003

A survey of the correspondence between abrasions and tooth brushing habits in Erzurum, Turkey.

AIM: To determine whether there is a correlation between dental abrasions and the frequency and technique of tooth brushing, as well as to examine the prevalence of dental abrasion according to age and gender. MATERIALS AND METHODS: This study was carried out on 428 adults (242 female, 186 male) 20 years of age and older, who attended the Department of Operative Dentistry, Department of Oral Diagnosis and Oral Radiology Faculty of Dentistry, Atatürk University. RESULTS: The study revealed a statistically significant relationship between abrasive lesions and age groups as well as between abrasive lesions and gender. A statistically significant difference was determined between abrasions and tooth brushing frequency, while there was no statistically significant relation between abrasions and tooth brushing technique (p>0.05). CONCLUSION: The prevalence of tooth brushing abrasions increases with age, and lesions are seen more frequently in males than in females. Also, tooth brushing technique is not important to the presence of abrasions, but increased tooth brushing frequency results in an increase in the number of abrasions.

Adult↗

PubMed2003

Preservation of the negative image of tooth enamel with dental impression material enhances morphometric measurements of gingival overgrowth.

Gingival overgrowth is a common health problem caused by genetic and environmental risk factors. Animal models for quantitative histological studies are needed to uncover genetic predisposition and dose-response data that might put individuals at increased risk for gingival disease. Gingival height, thickness, inflammation, and the degree of encroachment of gingiva over the tooth, are clinical measures of overgrowth; most of these parameters can be measured histologically, but in order to quantify gingival coverage of the tooth, the image of the crown must be present. Tooth and bone typically require decalcification for histology; thus, the tooth crown, a critical landmark, is lost. We describe a method for imaging the crown histologically, using impression materials applied to dissected mouse mandibles. Four dental alginates, three polyvinyl siloxanes, and one polyether and gelatin were used. The impression-material/mandibular tissue blocks were processed routinely. Polyvinyl siloxanes were incompatible with embedding resin; alginates, polyether and gelatin could be fixed, decalcified, embedded, and sectioned. Alginates and gelatin could be stained. Success in imaging the tooth crown varied with the preparation, but the alginates, polyether, and gelatin permitted a useful degree of measurement of exposed crown and enamel thickness, along with other morphometric parameters such as thickness of the dentin, lateral mandibular ramus, rete pegs, height of the gingiva, and volume density of vessels and inflammatory cells in the lamina propria. In conclusion, this new application for impression materials allows gingival coverage of tooth crown, as well as numerous other parameters to be measured for comparison with clinical data.

Alginates↗

PubMed1995

Sonographic depiction of fetal tooth germs.

Recently, sonography of the fetal face has gained increasing importance in prenatal diagnosis. It is not yet clear whether sonographic depiction of fetal tooth germs would have an influence on the prenatal diagnosis of ectodermal dysplasia syndromes. During routine malformation screening, horizontal sections of fetal jaws were visualized and examined for tooth germs in 124 pregnant women following sonographic 'facing'. Histological jaw sections of fetuses that had died in utero at various gestational ages were produced in order to examine the degree of correspondence between the sonographic and histological findings. At least four tooth germs were found in the jaws of all fetuses between 19 and 34 gestational weeks (n = 104). Although jaw visualization was possible between 14 and 18 gestational weeks (n = 20), the exact number and location of the tooth germs could not be determined. Assessment of tooth germs may become increasingly important, as aplasia of the tooth germs is one of the principal signs of various hereditary ectodermal diseases.

Anodontia↗

PubMed1994

Evidence for a neural influence on tooth germ generation in a polyphyodont species.

It has been suggested that nerve endings emanating from the dental nerve plexus of the jaw might be involved in the formation of tooth germs. In the present study we examine the effect of unilateral denervation on the formation of tooth germs in the lower jaw of a polyphyodont teleost--the cichild Tilapia mariae. Repeated inspection of the lower jaw dentition in normal animals over a period of about 300 days showed that the functional time of an average individual tooth is 101 days. In operated animals, the functional time was normal on the unoperated side, but on the denervated side tooth turnover ceased about 100 days after surgery. Radiographic plates from lower jaw specimens revealed that mineralized replacement teeth were present on the unoperated side, but not on the denervated side, 300 days after denervation. Light microscopic examination of semi-thin transverse sections from decalcified plastic-embedded lower jaws showed that soft-tissue tooth primordia and nerves were lacking on the denervated side, while present within the undisturbed half-jaw. It is concluded that the local presence of mandibular nerve branches is necessary for the formation of tooth germs in the lower jaw of the cichlid T. mariae.

Animals↗

PubMed1988

Fluoride-induced changes in the tooth glycosaminoglycans: an in vivo study in the rabbit.

Effect of high fluoride ingestion on the tooth matrix glycosaminoglycans was studied in rabbits administered 10 mg NaF/kg body weight orally at 24-h intervals for a period of 9 months. Fluoride-treated tooth showed a significant reduction in glycosaminoglycan content as compared to the normal tooth. Sephadex G-75 chromatography and DEAE-cellulose ion exchange chromatography revealed the presence of small molecular weight glycosaminoglycan molecules and an increase in the charge density heterogeneity in the sulphated glycosaminoglycans of the fluoride-treated rabbit tooth as compared to the controls. These changes may be related to the dedifferentiated tooth matrix and an increase in the dermatan sulphate content in the fluoride-treated tooth matrix reported earlier.

Animals↗

PubMed2003

The divergent expression of periostin mRNA in the periodontal ligament during experimental tooth movement.

A novel 90-kDa protein named periostin, which is preferentially expressed in the periosteum and the periodontal ligament (PDL), may play a role in bone metabolism and remodeling. However, the precise role of periostin in the PDL remains unclear. Therefore, we examined the expression of periostin mRNA during experimental tooth movement. Experimental tooth movement was achieved in 7-week-old male Sprague-Dawley rats. In control specimens without tooth movement, the expression of periostin mRNA was uniformly observed in the PDL surrounding the mesial and distal roots of the upper molars and was weak in the PDL of the root furcation area. The periostin mRNA-expressing cells were mainly fibroblastic cells in the PDL and osteoblastic cells on the alveolar bone surfaces. The divergent expression of periostin mRNA in the PDL began to be observed at 3 h and continued up to 96 h after tooth movement. The maximum changes, which showed stronger staining in the pressure sites than in the tension sites, were observed at 24 h. The expression of periostin mRNA in the PDL 168 h after tooth movement exhibited a similar distribution to that of the control specimens. These results suggest that periostin is one of the local contributing factors in bone and periodontal tissue remodeling following mechanical stress during experimental tooth movement.

Animals↗

PubMed2004

Osteoclastogenesis during mouse tooth germ development is mediated by receptor activator of NFKappa-B ligand (RANKL).

To accommodate developing tooth germ in the alveolar bone, active bone resorption and the recruitment of numerous osteoclasts are essential. Recently, the signaling of receptor activator of nuclear factor-KappaB (RANK) and its ligand (RANKL) was reported to play a pivotal role in osteoclast formation and activation. The aim of this study was to examine the expression of RANKL and the contribution of RANK-RANKL signaling to the process of tooth germ and alveolar bone development. In situ hybridization showed RANKL was expressed in dental follicle cells and osteoblasts on the alveolar bone surface surrounding developing tooth germs. To elucidate the function of RANKL, mouse mandibular explants on embryonic day 14 were subjected to organ culture with osteoprotegerin (OPG), an inhibitor of RANK-RANKL signaling as a decoy receptor of RANKL. Many tooth germs were compressed with the surrounding bone tissue in the OPG-treated explants, whereas these abnormalities were not seen in untreated explants. The numbers of tartrate-resistant acid phosphatase (TRAP)-positive osteoclastic cells aligning on the alveolar bone surface were significantly decreased in OPG-treated explants compared with untreated explants. Moreover, TRAP-positive osteoclastic cells were not observed along the alveolar bone surfaces depressing tooth germs. These observations suggest that osteoclastogenesis in the alveolar bone, which is essential for the accommodation of normal tooth development, is mediated by RANK-RANKL signaling.

Acid Phosphatase↗

PubMed1982

The effects of sympathetic trunk stimulation on the position and mobility of the canine tooth of the cat.

The effects of cervical sympathetic trunk stimulation on the position of the maxillary canine tooth and its movements in response to mechanical loading were studied using an ultrasonic transit time technique. Stimulation of the ipsilateral sympathetic trunk for 10-60s and frequencies between 1 and 20 Hz caused both longitudinal and transverse movements of the tooth. Bilateral carotid occlusion caused negligible movements in either direction. When a controlled force was applied in the palatal direction, sympathetic stimulation caused a labial shift of the tip of the tooth and usually an increase in the load-induced palatal displacement; i.e. the mobility of the tooth was increased and appeared to be dependent on the amount of labial shift of the tooth. It is concluded that interference with the vascular component has little, if any, direct effect on the tooth mobility.

Animals↗