Stages Of Tooth Formation Research Articles

Evaluation of Dental Age in Nepali Children using Demirjian’s 7-Teeth Teeth Method

Introduction: Age estimation can be based on tooth formation stages seen on the radiographs. Demirjian’s method is widely used to assess age of individuals with developing dentition. There are not many documented studies of age estimation amongst Nepali population.Objective: To assess the applicability of Demirjian’s method for dental age estimation in Nepali children.Materials & Method: The sample of the study consisted of 186 subjects between 7-16 years of age. Dental age estimation was based on Demirjian’s method and scored by a single observer.Result: The mean and mean differences in chronological and dental ages were calculated, which revealed the overestimation in age groups of 7 and 9 years, whereas there were underestimations in other age groups. The mean differences in age groups 12-16 were highly significant (p-Value <0.05) whereas the mean difference in age groups 7-11 years were not statistically significant.Conclusion: Since there is underestimation range from 0.5 years to 1.23 years, the standards of dental maturity described by Demirjian may not be suitable for Nepali children.

Evaluation of characteristics of the craniofacial complex and dental maturity in girls with central precocious puberty.

To identify unique characteristics of the craniofacial complex and dental maturity in girls with central precocious puberty (CPP). This study included 34 Korean girls with idiopathic CPP (mean age, 8.6 ± .5 years) and 28 normal healthy girls of the same chronological age. An initial evaluation of the growth pattern of the craniofacial complex and dental maturity was conducted by analyzing lateral cephalometric and panoramic radiographs. The mandibular ramus height (44.4 ± 4.1 mm) and total mandibular length (10.8 ± 4.3 mm) ( P = .004 and .021, respectively) were greater and the lower anterior facial height was lesser (63.2 ± 2.4 mm) ( P = .040) in the CPP group than in the reference group. In addition, the gonial angle (12.9 ± 6.1°; P = .045) and the mandibular plane angle (34.9 ± 4.8°; P = .012) were smaller in girls with CPP than in normal healthy girls. All the mandibular teeth were more mature in girls with CPP ( P < .001). A strong positive correlation was observed between the mandibular tooth formation stages and the presence of CPP in girls ( r = .756 to .957; P < .001). CPP had an effect on the anteroposterior growth of the mandible in the craniofacial complex and the rotation of the mandibular plane angle. Early maturation of the mandibular teeth was observed in girls with CPP.

The WITS Atlas: A Black Southern African dental atlas for permanent tooth formation and emergence.

To develop a population-specific atlas of permanent tooth emergence and formation for age estimation of Black Southern Africans. Using data from a cross-sectional study of 642 school children aged 5-20 years, panoramic radiographs taken during routine dental examination in a mobile treatment van were analyzed using the Demirjian method of eight (A-H) tooth formation stages. Tables of the stages of tooth development for each tooth, including the third molars, were generated separately for age cohorts and by sex. The most frequently occurring (modal) stage of tooth formation was considered the signature developmental stage for the age. The relationship of the third molar occlusal surfaces with occlusal tables on the radiographs were checked and compared with the findings recorded during intra oral examination. Comparison with the London atlas shows that at age 9.5 years, the canine and premolar emergence are at least one year ahead and the third molar formation completes four years earlier in the WITS Atlas. Similarities in advancement in tooth formation and emergence across sub-Saharan Africa suggest that the WITS Atlas can be used for those populations as well.

DNA Methylation: A Frontier in Tooth Organogenesis and Developmental Dental Defects.

Tooth development relies on interactions between epithelial and mesenchymal tissues, which are controlled by sophisticated networks of conserved signaling. The signaling networks regulating odontogenesis have been well characterized, but the epigenetic mechanisms underlying remain to be elucidated. In this review, we describe current researches regarding the control of various genes expression by DNA methylation during odontogenesis, summarize genomic mapping of DNA methylation in various stages of tooth formation and diverse dental tissues by high-throughput approaches, and highlight the roles of DNA methylation in odontogenesis. Researches on mammals have revealed that the genomic methylation, which occurs on cytosine residues, regulates certain genes transcription. Consequently, DNA methylation plays a crucial role in spatiotemporal organization of signaling pathways, and is essential for organogenesis. Recently, mounting evidence proves that methylation of genomes contributes to the spatiotemporal gene dynamics during odontogenesis. With emerging new technologies of mapping cytosine modifications in global genome, investigators are seeking an overall view of DNA methylome dynamics that characterize genetic information to manifest across incredibly varied tooth development stages, dental tissues, and developmental dental defects.

Sexual dimorphism, pattern of third molar and mandibular second premolar agenesis in Indian paediatric orthodontic patients.

ObjectiveTo determine and compare the prevalence and pattern of agenesis of third molar and mandibular second premolar in paediatric orthodontic patients of age group 9–15 for sexual dimorphism.MethodsThe digital orthopantograph was obtained from the archive record of patients of age group 9–15 year. Radiographs of 301 patients were evaluated after taking exclusion criteria into account and were assessed for the presence/absence of third molars and mandibular second premolar. Tooth development evaluation followed the method of Demirjian et al., based on eight stages of tooth formation. The agenesis of third molar in maxilla and mandible between age groups and gender was compared using Chi-squared test.ResultsThe rate of agenesis of third molars was observed 36.8% in the present study. Twenty-four (24.3%) percentage of the study population showed agenesis of all the four third molars. The agenesis of third molars was found to be higher among males than females (p > 0.05). Prevalence of agenesis of mandibular second premolar was 4.7–5%.ConclusionsAgenesis of third molars was more commonly seen in the maxilla, having male predilection. Maxillary right third molar was the most commonly missing tooth irrespective of gender.

Telomerase Expression in Medaka (Oryzias melastigma) Pharyngeal Teeth

Nonmammalian vertebrates have the capacity of lifelong tooth replacement. In all vertebrates, tooth formation requires contact and interaction between the oral or pharyngeal epithelium and the underlying mesenchyme. To secure lifelong replacement, the presence of odontogenic stem cells has been postulated, particularly in the epithelial compartment. This study uses an advanced teleost fish species, the marine medaka Oryzias melastigma, a close relative to Oryzias latipes, to examine the expression and distribution of telomerase reverse transcriptase (Tert), the catalytic unit of telomerase, in developing pharyngeal teeth and to relate these data to the proliferative activity of the cells. The data are complemented by expression analysis of the pluripotency marker oct4 and bona fide stem cell marker lgr5. Tert distribution and tert expression in developing tooth germs show a dynamic spatiotemporal pattern. Tert is present first in the mesenchyme but is downregulated as the odontoblasts differentiate. In contrast, in the epithelial enamel organ, Tert is absent during early stages of tooth formation and upregulated first in ameloblasts. Later, Tert is expressed and immunolocalized throughout the entire inner enamel epithelium. The pattern of Tert distribution is largely mutually exclusive with that of proliferating cell nuclear antigen (PCNA) immunoreactivity: highly proliferative cells, as revealed by PCNA staining, are negative for Tert; conversely, PCNA-negative cells are Tert-positive. Only the early condensed mesenchyme is both Tert- and PCNA-positive. The absence of tert-positive cells in the epithelial compartment of early tooth germs is underscored by the absence of oct4- and lgr5-positive cells, suggesting ways other than stem cell involvement to secure continuous renewal.

Conservative Management of Unicystic Ameloblastoma in Young Patients: A Prospective Single-Center Trial and Review of Literature

The study intends to evaluate the clinical outcome of treating young patients of unicystic ameloblastoma, by various conservative treatment modalities such as marsupialization, enucleation with bone curettage and aid in establishing sound treatment guidelines. A case series of fifteen patients is presented of unicystic ameloblastoma, who presented to our Department over the past 6years (2010-2015) and conservative method of treatment elected in all the patients. Also, a methodical literature review of studies discussing treatment of unicystic ameloblastoma in young age group (<20years) patients over the last 15years from 2001 to 2015 is added. Faster osseous regeneration after conservative treatment was noted, owing to the young age and growth potential. Over a mean follow-up of 4years, uneventful secondary healing, no clinical or radiographic evidence of recurrence and no apparent deformity were noted in any of the cases. Unicystic ameloblastoma is a benign, locally invasive odontogenic neoplasm of young age which can develop during the stage of tooth formation and hence its early inception and vast proliferation is not uncommon in this age group, due to which it can grow into a huge lesion causing significant morbidity. Conservative surgical management may be a viable option to reduce morbidity and increase the probability of uneventful secondary healing and bone regeneration in the younger population.

The timing of mandibular tooth formation in two African groups

Background: Ethnic differences in the timing of human tooth development are unclear.Aim: To describe similarities and differences in the timing of tooth formation in two groups of Sudanese children and young adults.Subjects and methods: The sample consisted of healthy individuals from Khartoum, Sudan, aged 2–23 years. The Northern group was of Arab origin (848 males, 802 females) and the Western group was of African origin (846 males, 402 females). Each mandibular left permanent tooth from first incisor to third molar was assessed from dental radiographs into one of 15 development stages. Mean ages at entry for 306 tooth stages were calculated using probit regression in males/females in each group and compared using a t-test.Results: Mean ages were not significantly different in most tooth stage comparisons between ethnic groups for both males (61/75) and females (56/76), despite a tendency of earlier mean ages in the Western group. Mean ages for most tooth stage comparisons between males and females (137/155) were not significantly different within ethnic groups suggesting low sexual dimorphism.Conclusion: The mean ages of most mandibular tooth formation stages were generally not significantly different between ethnic groups or between males and females in this study.

Effects of Usag-1 and Bmp7 deficiencies on murine tooth morphogenesis.

BackgroundWnt5a and Mrfzb1 genes are involved in the regulation of tooth size, and their expression levels are similar to that of Bmp7 during morphogenesis, including during the cap and early bell stages of tooth formation. We previously reported that Usag-1-deficient mice form supernumerary maxillary incisors. Thus, we hypothesized that BMP7 and USAG-1 signaling molecules may play important roles in tooth morphogenesis. In this study, we established double genetically modified mice to examine the in vivo inter-relationships between Bmp7 and Usag-1.ResultsWe measured the volume and cross-sectional areas of the mandibular incisors using micro-computed tomography (micro-CT) in adult Bmp7- and Usag-1-LacZ knock-in mice and their F2 generation upon interbreeding. The mandibular incisors of adult Bmp7+/− mice were significantly larger than those of wild-type (WT) mice. The mandibular incisors of adult Usag-1−/− mice were the largest of all genotypes examined. In the F2 generation, the effects of these genes were additive; Bmp7+/− was most strongly associated with the increase in tooth size using generalized linear models, and the total area of mandibular supernumerary incisors of Usag-1−/−Bmp7+/− mice was significantly larger than that of Usag-1−/−Bmp7 +/+ mice. At embryonic day 15 (E15), BrdU assays demonstrated that the labeling index of Bmp7+/− embryos was significantly higher than that of WT embryos in the cervical loop. Additionally, the labeling index of Usag-1−/− embryos was significantly the highest of all genotypes examined in dental papilla.ConclusionsBmp7 heterozygous mice exhibited significantly increased tooth sizes, suggesting that tooth size was controlled by specific gene expression. Our findings may be useful in applications of regenerative medicine and dentistry.Electronic supplementary materialThe online version of this article (doi:10.1186/s12861-016-0117-x) contains supplementary material, which is available to authorized users.

Role of Genes in Odontogenesis

With the discovery of the homeobox genes in craniofacial biology researchers across the globe have studied in depth the genetic patterning of the craniofacial region. With respect to craniofacial development ‐, Barx, Dlx, Gsc, Lim, Msx, Otx, Prx; part of the Hox cluster are important. Barx gene are strongly expressed only in the mesenchyme of the developing molars. Dlx gene expression is noted in the mandibular and maxillary arch ectomesenchyme. Msx genes are expressed in the area of epithelial mesenchymal interactions in the brachial arches in the area of future dentition and also expressed in the formation of skull, facial primordial and sense organs. Msx-1 is seen to be expressed in various stages of tooth formation i.e bud and cap stage of organogenesis. Lim genes which control morphogenesis of the first brachial arch, are expressed in the maxillo-mandibular ectomesenchyme. Prx gene expression is seen in the proximal portion of the mandibular arch. The role of hox genes in the morphogenesis of the jaws and the dentition is immense. Thus it has been proved beyond doubt that the genes have a major role in organogenesis than what human beings have ever envisaged. This review will give the scientific community an overview of all the genes affecting odontogenesis.

Age estimation in fossil hominins: comparing dental development in early Homo with modern humans

Background: Previous studies have used molar tooth eruption as a comparative marker of maturation in early fossil hominins. However, tooth eruption and tooth formation are independent maturational processes.Aim: To determine whether estimates of age for entering a stage of dental development in three early hominin fossils fell within the distribution of a modern human sample.Methods: This study used a comparative model of dental development to identify the stages of dental development most likely to provide information about length of the growth period in early fossil hominins. Age estimates for stages of dental development in fossils were superimposed onto a normal distribution of the same radiographically defined stages derived from a sample of 6540 children of diverse geographical origin.Results: Both within the dentition of S7–37, from Sangiran, Java, but also for stages of two other specimens (KNM-WT 15000 from Kenya and StW 151 from South Africa), all age estimates for later stages of tooth formation fell within the modern sample range.Conclusions: A pattern appears to exist in early Homo where, both within and between developing dentitions, age estimates for stages of P4, M2 and M3 tooth formation fell consistently among the more advanced individuals of the modern human sample.

Dental age estimation standards for a Western Australian population

Age estimation in the juvenile skeleton primarily relies on the assessment of the degree of dental and skeletal development relative to full maturity. The timing of the mineralization and eruption of the teeth is a sequential process that, compared to skeletal growth and development, is less affected by extrinsic influences such as nutrition and/or chronic illness. Accordingly, radiographic visualization and analysis of different tooth formation stages are the foundation for a number of widely applied age estimation standards. Presently, however, there is a relative paucity of contemporary dental age estimation standards for a Western Australian population. To that end, the aim of the present study is to develop statistically quantified radiographic age estimation standards for a Western Australian juvenile population.A total of 392 digital orthopantomograms (202 male and 190 female) of Western Australian individuals are analyzed. Following, Moorrees et al. (J. Dent. Res. 42 (1963a) 490–502; Am. J. Phys. Anthropol. 21 (1963) 205–213), dental development and root resorption was assessed. Alveolar eruption was analyzed following Bengston (Northwest Univ. Bull. 35 (1935) 3–9). Stages of dental development were used to formulate a series of age estimation polynomial regression models; prediction accuracy (±0.998 to 2.183 years) is further validated using a cross-validation (holdout) sample of 30 film orthopantomograms. A visual atlas of dental development and eruption was subsequently designed for the pooled sex sample. The standards presented here represent a non-invasive and statistically quantified approach for accurate dental age estimation in Western Australian juvenile individuals.

Tissue Interactions Regulating Tooth Development and Renewal.

Reciprocal interactions between epithelial and mesenchymal tissues play a fundamental role in the morphogenesis of teeth and regulate all aspects of tooth development. Extensive studies on mouse tooth development over the past 25 years have uncovered the molecular details of the signaling networks mediating these interactions (reviewed by Jussila & Thesleff, 2012; Lan, Jia, & Jiang, 2014). Five conserved signaling pathways, namely, the Wnt, BMP, FGF, Shh, and Eda, are involved in the mediation of the successive reciprocal epithelial-mesenchymal cross talk which follows the general principle of morphogenetic interactions (Davidson, 1993). The pathways regulate the expression of transcription factors which confer the identity of dental epithelium and mesenchyme. The signals and transcription factors are integrated in complex signaling networks whose fine-tuning allows the generation of the variation in tooth morphologies. In this review, we describe the principles and molecular mechanisms of the epithelial-mesenchymal interactions regulating successive stages of tooth formation: (i) the initiation of tooth development, with special reference to the shift of tooth-forming potential from epithelium to mesenchyme; (ii) the morphogenesis of the tooth crown, focusing on the roles of epithelial signaling centers; (iii) the differentiation of odontoblasts and ameloblasts, which produce dentin and enamel, respectively; and (iv) the maintenance of dental stem cells, which support the continuous growth of teeth.

Formation and development of maxillary first molars with delayed eruption.

Cases of congenitally missing and delayed eruption of the maxillary first molar are rare. However, in recent years, we have experienced cases of suspected delayed eruption of or congenitally missing first molars. The purpose of this study was to analyze the formation of delayed erupted maxillary first molars (M1) (>2 standard deviations), which play important roles in occlusion, and normal eruption of the maxillary first molars (U6). The frequency of M1 among patients born between 1974 and 1994 in one institution with a clear total patient number and personal oral histories was 1.55 % [80 % bilateral eruption in 8 of 806 male patients (0.99 %) and 23 of 1195 female patients (1.92 %)]. To evaluate the formation and eruption of M1 according to Moorrees's tooth formation stages, panoramic X-ray films were obtained every year for 73 patients with M1 from 3 institutions (20 male and 53 female patients, total 131 M1s) without systematic histories or genetic disorders. The development/growth curve of M1 was fitted to both the logistic curve and U6 curve. The M1 development/growth curve was started behind with U6 curve; however, the straight part of the M1 curve exhibited steep inclination compared with the straight part of the U6 curve. The curve of the eruption pathway of M1 also exhibited a sigmoid S shape. These results indicate that the development and migration speed of M1 are faster than that of U6, excluding the delayed start point. These results may help orthodontists in treatment planning for patients with M1.

Malnutrition Has No Effect on the Timing of Human Tooth Formation

The effect of nutrition on the timing of human tooth formation is poorly understood. Delays and advancements in dental maturation have all been reported as well as no effect. We investigated the effect of severe malnutrition on the timing of human tooth formation in a large representative sample of North Sudanese children. The sample (1102 males, 1013 females) consisted of stratified randomly selected healthy individuals in Khartoum, Sudan, aged 2-22 years using a cross-sectional design following the STROBE statement. Nutritional status was defined using WHO criteria of height and weight. Body mass index Z-scores and height for age Z-scores of ≤−2 (cut-off) were used to identify the malnourished group (N = 474) while the normal was defined by Z-scores of ≥0 (N = 799). Clinical and radiographic examination of individuals, with known ages of birth was performed including height and weight measurements. Mandibular left permanent teeth were assessed using eight crown and seven root established tooth formation stages. Mean age at entry and mean age within tooth stages were calculated for each available tooth stage in each group and compared using a t-test. Results show the mean age at entry and mean age within tooth stages were not significantly different between groups affected by severe malnutrition and normal children (p>0.05). This remarkable finding was evident across the span of dental development. We demonstrate that there is little measurable effect of sustained malnutrition on the average timing of tooth formation. This noteworthy finding supports the notion that teeth have substantial biological stability and are insulated from extreme nutritional conditions compared to other maturing body systems.

Estimating ages by third molars: Stages of development in Brazilian young adults

The purpose of this study was to estimate age through the analysis of third molar stages of development in Brazilian young adults. A cross-sectional study was conducted by analyzing 659 panoramic X-rays. Two techniques were used to establish the stages: Modified Scoring (MST) and Demirjian (DT). Regression formulas were calculated. Statistical analyses were conducted by t, Kappa tests, and simple and multiple linear regressions (5% level of significance). Out of the participants, 40.7% were female and 59.3% were male, with ages from 15–22 years. The Kappa test showed good results for intra-observer (0.84 for MST and 0.95 for DT) and inter-observer examination (0.81 for MST and 0.92 for DT). Differences were found in the stages of tooth formation between male and female, but differences were not observed between the left and right sides. We found that both DT and MST underestimated the ages in about 6 months, depending on the used classification and number of teeth. These methods are appropriate for assessing the ages of young Brazilians, although the DT showed better reproducibility.

Genetic basis for tooth malformations: from mice to men and back again

Teeth arise from sequential and reciprocal interactions between the oral epithelium and the cranial neural crest-derived mesenchyme. Their formation involves a precisely orchestrated series of molecular and morphogenetic events. Numerous regulatory genes that have been primarily found in organisms such as Drosophila, zebrafish, xenopus and mouse are associated with all stages of tooth formation (patterning, morphogenesis, cytodifferentiation and mineralization). Most of these genes belong to evolutionary conserved signaling pathways that regulate communication between epithelium and mesenchyme during embryonic development. These signaling molecules together with specific transcription factors constitute a unique molecular imprint for odontogenesis and contribute to the generation of teeth with various and function-specific shapes. Mutations in several genes involved in tooth formation cause developmental absence and/or defects of teeth in mice. In humans, the odontogenic molecular program is not as well known as that of mice. However, some insight can be obtained from the study of mutations in regulatory genes, which lead to tooth agenesis and/or the formation of defective dental tissues.

The usefulness of dental and cervical maturation stages in New Zealand children for Disaster Victim Identification

Age estimation of young victims of natural and un-natural disasters remains a crucial and challenging task during the process of Disaster Victim Identification (DVI). The purpose of this study was to compare dental maturity using the Demirjian and Cameriere methods and to explore the relationship between dental age and cervical vertebral maturity (CVM) using the Hassel and Farman method for a group of New Zealand children. The study used lateral cephalometric and panoramic radiographs of 200 orthodontic patients aged 7-17 years. Dental age was calculated from mandibular tooth formation stages using the Demirjian and Cameriere methods by calculating the ratio of tooth length to apex width for these teeth. CVM was assessed using stages from Hassel and Farman. Reliability of maturity from reassessment of 20 radiographs showed good agreement for the three methods. Chronological and dental ages were compared using a mixed model. Descriptive statistics of dental ages by CVM stage were calculated. The results show that both dental methods were similar in assessing maturity. A disadvantage of using the Cameriere method was that all seven teeth reached maturity at 13.69 and 14.06 years in females and males respectively, compared to age 16 using the Dermijian method. Females reached CVM stages at earlier chronological and dental ages than males. Mean chronological age for CVM stages 2-5 is about 1 year earlier in females than males. The Demirjian and Cameriere methods of dental maturity and CVM are reliable and useful in assessing dental and skeletal maturity. Ideally in a DVI situation, both the methods of Demirjian and Cameriere, together with CVM, should be employed in the ageing of individuals suspected of being between 7 and 16 years.

Interpreting group differences using Demirjian's dental maturity method

Although Demirjian's method is designed to assess dental maturity at the individual level, significant differences between average dental age and real age for groups have been interpreted as population differences. The aim of this study was to describe the variation in maturity score for age and age for maturity score from a large collaborative database of children and discuss methods adapted for groups in light of this. Tooth stages from radiographs of 4710 males and 4661 females (age 2–18) were used and dental maturity scores calculated using Demirjian and Goldstein [2]. The mean, standard deviation, standard error and 95% confidence intervals of maturity score by age group (6 and 12 months groups) and age by maturity score (5 points) groups were calculated. Adapted maturity curves from 13 published studies of boys from Europe, Middle East, Africa, India, China and South America were compared to the database. Most adapted curves at the 50th percentile from world regions fell within the 95% confidence intervals. Those that did not, were hampered by small sample size or poorly fitting curves. This is complicates by the inclusion of mature individuals. Few studies adapting Demirjian's method provide sufficient or appropriate statistics to compare maturation of individual teeth. The wide 95% confidence intervals for maturity score by age, age by maturity score, age of individual tooth stages and large number of sequences suggest that the significant differences in dental maturity score do not reflect any biological difference in the timing of tooth formation stages at the population level. Demirjian's dental maturity method is inappropriate to assess population differences in dental maturity and adapting scores for age or age for scores for different groups of children is probably unnecessary.

Reiterative pattern of sonic hedgehog expression in the catshark dentition reveals a phylogenetic template for jawed vertebrates.

For a dentition representing the most basal extant gnathostomes, that of the shark can provide us with key insights into the evolution of vertebrate dentitions. To detail the pattern of odontogenesis, we have profiled the expression of sonic hedgehog, a key regulator of tooth induction. We find in the catshark (Scyliorhinus canicula) that intense shh expression first occurs in a bilaterally symmetrical pattern restricted to broad regions in each half of the dentition in the embryo jaw. As in the mouse, there follows a changing temporal pattern of shh spatial restriction corresponding to epithelial bands of left and right dental fields, but also a subfield for symphyseal teeth. Then, intense shh expression is restricted to loci coincident with a temporal series of teeth in iterative jaw positions. The developmental expression of shh reveals previously undetected timing within epithelial stages of tooth formation. Each locus at alternate, even then odd, jaw positions establishes precise sequential timing for successive replacement within each tooth family. Shh appears first in the central cusp, iteratively along the jaw, then reiteratively within each tooth for secondary cusps. This progressive, sequential restriction of shh is shared by toothed gnathostomes and conserved through 500 million years of evolution.