Stages Of Tooth Development Research Articles

Relationship between inter-molar, inter-canine, and inter-gonion widths in children aged 6–9 years

The mixed dentition stage of tooth development is critical as it often involves changes in the inter-molar and inter-canine widths of the dental arch, which may affect the inter-gonion width. It was hypothesized that the relationship between the inter-molar, inter-canine, and inter-gonion widths could be used to estimate the width of the dental arch, thus allowing better treatment planning. This research aimed to determine the relationship between the inter-molar, inter-canine, and inter-gonion widths in children aged 6–9 years old. This cross-sectional study used 30 study models and panoramic radiographic images of pediatric patients in Teaching Dental Hospital, Faculty of Dentistry, Universitas Indonesia. The results showed that the inter-molar and inter-gonion widths and the inter-canine and inter-gonion widths exhibited weak correlations that were not statistically significant (r = 0.277, r = 0.032, respectively). However, the inter-molar and inter-canine widths demonstrated a strong, statistically significant correlation (r = 0.580).

Evaluation and Immunolocalization of BMP4 and FGF8 in Odontogenic Cyst and Tumors.

Growth factors like bone morphogenetic protein 4 (BMP4) and fibroblast growth factor 8 (FGF8) play a major role in organogenesis and specifically in odontogenesis. They are also believed to have a role in oncogenesis. Thus, any discrepancies in their standard behavior and activity would lead to serious abnormalities including odontogenic cyst and tumors. The present research work investigated the expression of BMP4 and FGF8 in odontogenic tumors (OT) and cyst as well as developing tooth germs to elucidate their roles. Dental organs of various odontogenic stages and 30 OTs including solid multicystic ameloblastomas (SMA, 10 cases), ameloblastic fibroma (AF, 10 cases), odontogenic myxoma (OM, 10 cases), and odontogenic cysts: odontogenic keratocyst (OKC, 10 cases) were evaluated in both epithelial and mesenchymal components for the expression of BMP4 and FGF8 using immunohistochemistry. The epithelial nuclear expression of BMP4 was highest in OKC (9 cases) while FGF8 was highest in SMA (10 cases). The mesenchymal nuclear expression of both BMP4 (8 cases) (p = 0.001) and FGF8 (9 cases) (p = 0.045) were significantly high in OMs among all OTs. Both growth factors were actively expressed in different stages of tooth development. The expression of BMP4 and FGF8 corelates well with the proliferative component of the pathologies, indicating a possible role in the pathogenesis and progression.

Ablation of Runx2 in Ameloblasts Suppresses Enamel Maturation in Tooth Development

Runt-related transcription factor 2 (Runx2) is involved in the early stage of tooth development. However, only few studies have reported the role of Runx2 in enamel development, which may be attributed to that Runx2 full knockout mice cannot survive after birth. In the present study, we successfully established a Runx2-deficient mouse model using a conditional knockout (cKO) method. We observed a significant reduction in the degree of mineralization and the decreased size of enamel rods in cKO mice. Histological analysis showed the retained enamel proteins in enamel layer at maturation stage in cKO molars. Further analysis by qRT-PCR revealed that the expressions of genes encoding enamel structure proteins, such as amelogenin (AMELX), ameloblastin (AMBN) and enamelin (ENAM), were increased in cKO enamel organs. On the other hand, the expression of kallikrein-related peptidase-4 (KLK4) at the mRNA and protein levels was dramatically decreased from late secretory stage to maturation stage in cKO enamel organs, while the expression of matrix metalloproteinase-20 (MMP-20) was not significantly altered. Finally, immunohistochemistry indicated that the uptake of amelogenins by ameloblasts was significantly decreased in cKO mice. Taken together, Runx2 played critical roles in controlling enamel maturation by increasing synthesis of KLK4 and decreasing synthesis of AMELX, AMBN and ENAM.

WNT10A mutation results in severe tooth agenesis in a family of three sisters.

To identify the genetic basis of severe tooth agenesis in a family of three affected sisters. A family of three sisters with severe tooth agenesis was recruited for whole-exome sequencing to identify potential genetic variation responsible for this penetrant phenotype. The unaffected father was tested for specific mutations using Sanger sequencing. Gene discovery was supplemented with in situ hybridization to localize gene expression during human tooth development. We report a nonsense heterozygous mutation in exon 2 of WNT10A c.321C>A[p.Cys107*] likely to be responsible for the severe tooth agenesis identified in this family through the creation of a premature stop codon, resulting in truncation of the amino acid sequence and therefore loss of protein function. In situ hybridization showed expression of WNT10A in odontogenic epithelium during the early and late stages of human primary tooth development. WNT10A has previously been associated with both syndromic and non-syndromic forms of tooth agenesis, and this report further expands our knowledge of genetic variation underlying non-syndromic forms of this condition. We also demonstrate expression of WNT10A in the epithelial compartment of human tooth germs during development.

The impact of premature birth on dental maturation in the permanent dentition

ObjectivesTo evaluate tooth development and calculate dental maturity score in prematurely born children and to compare the findings with full-term born children.Material and methodsNine-year-old preterm children were selected from the Swedish Medical Birth Register. One group consisted of 36 extremely preterm children (born before week 29), and the other included 38 very preterm children (born during weeks 29 to 32). Panoramic radiography was performed on each child and the preterm children were compared with 42 full-term born children. Five observers independently assessed the tooth development stages for all teeth in the left mandible (31–37) on the panoramic radiographs according to the method described by Demirjian et al. (Hum Biol 45:211–227, 1973). Data from tooth development stages were compiled and converted into a dental maturity score for each group. Kappa values were calculated for intra- and inter-observer agreement.ResultsWhen the different development stages for each individual tooth were compared, all observers presented a significant delay in the maturity of tooth 37 for the extremely preterm group (p ≤ 0.002). The extremely preterm group had a significantly lower dental maturity score than the full-term group, as assessed by each observer (p ≤ 0.006). Kappa values for inter-observer agreement varied between 0.31 and 0.71 depending on tooth and intra-observer agreement was between 0.16 and 1.0.ConclusionsAt age 9, the extremely preterm children had a general delay in tooth development.Clinical relevanceThe increased survival rate of extremely preterm babies adds a new group of children to society. Dental clinicians should be aware that the delay in tooth development could impact the timing of orthodontic diagnostics and potential treatment.

A radiographic assessment of the correlation between the calcification stages of the mandibular second molar and the middle phalanx of the third finger of 9\u201316 years old children

BackgroundHand-wrist radiographs and orthopantomographs are routinely used for assessing skeletal and dental maturation and analyzing skeletal morphology and growth patterns. Though minimal radiation is associated with a hand-wrist radiograph, it would be superlative to assess the growth stage without an additional radiograph.AimTo assess the correlation between the calcification stages of mandibular second molar and the modified middle phalanx of the third finger (modified MP3) of 9 to 16 year old children.DesignIn this cross-sectional observational study we assessed the dental calcification of the mandibular second molar on orthopantomograms using Demirjian’s tooth developmental stages and skeletal maturity of the middle phalanx of the third finger on hand-wrist radiographs using modified MP3 method proposed by Rajagopal and Kansal (J Clin Orthod 36(7):398, 2002) of 100 children (48 boys and 52 girls), aged between 9 and 16 years.ResultsA strong association was found between calcification stages of mandibular right second molar and the developmental stages of the modified middle phalanx of the third finger of right hand in both the gender. Spearman rank order correlation coefficients between the developmental stages of the modified MP3 of hand and the developmental stages of the mandibular second molar and found to be statistically significant positive in males (0.62) and females (0.41) when Demirjian’s Index (DI) and modified middle phalanx of the third finger stages were compared.ConclusionThere was a good concordance between the stages of modified middle phalanx of the third finger and the Demirjian’s tooth developmental stages. Demirjian’s second molar calcification stages can be a better choice for predicting skeletal maturity because of its simplicity and reliability.

Proteome response of dental pulp cells to exogenous FGF8

FGF8 specifies early tooth development by directing the migration of the early tooth founder cells to the site of tooth emergence. To date the effect of the FGF8 in adult dental pulp has not been studied. We have assessed the regenerative potential of FGF8 by evaluating changes in the proteome landscape of dental pulp following short- and long-term exposure to recombinant FGF8 protein. In addition, we carried out qRT PCR analysis to determine extracellular/adhesion gene marker expression and assessed cell proliferation and mineralization in response to FGF8 treatment. 2D and mass spectrometry data showed differential expression of proteins implicated in cytoskeleton/ECM remodeling and migration, cell proliferation and odontogenic differentiation as evidenced by the upregulation of gelsolin, moesin, LMNA, WDR1, PLOD2, COPS5 and downregulation of P4HB. qRT PCR showed downregulation of proteins involved in cell-matrix adhesion such as ADAMTS8, LAMB3 and ANOS1 and increased expression of the angiogenesis marker PECAM1. We have observed that, FGF8 treatment was able to boost dental pulp cell proliferation and to enhance dental pulp mineralization. Collectively, our data suggest that, FGF8 treatment could promote endogenous healing of the dental pulp via recruitment of dental pulp progenitors as well as by promoting their angiogenic and odontogenic differentiation. SignificanceDental pulp cells (DP) have been studied extensively for the purposes of mineralized tissue repair, particularly for the reconstruction of hard and soft tissue maxillofacial defects. Canonical FGF signaling has been implicated throughout multiple stages of tooth development by regulating cell proliferation, differentiation, survival as well as cellular migration. FGF8 expression is indispensible for normal tooth development and particularly for the migration of early tooth progenitors to the sites of tooth emergence. The present study provides proteome and qRT PCR data with regard to the future application and biological relevance of FGF8 in dental regenerative medicine. Authors with ORCIDRozaliya Tsikandelova - 0000-0003-0178-3767Zornitsa Mihaylova - 0000-0003-1748-4489Sébastien Planchon - 0000-0002-0455-0574Nikolay Ishkitiev - 0000-0002-4351-5579

Cell cycle of the enamel knot during tooth morphogenesis.

Enamel knot (EK) is known to be a central organ in tooth development, especially for cusp patterning. To trace the exact position and movement among the inner dental epithelium (IDE) and EK cells, and to monitor the relationship between the EK and cusp patterning, it is essential that we understand the cell cycle status of the EK in early stages of tooth development. In this study, thymidine analogous (IdU, BrdU) staining was used to evaluate the cell cycle phase of the primary EK at the early casp stage (E13.0) and the gerbil embryo (E19) in a developing mouse embryo. The centerpiece of this study was to describe the cell cycle phasing and sequencing during proliferation in the IDE according to the expression of IdU and BrdU following their injection at calculated time points. The interval time between IdU injection and BrdU injection was set at 4h. As a result, the cell cycle in the IDE of the mouse and gerbil was found to be synchronous. Conversely, the cell cycle in primary EKs of mice was much longer than that of the IDE. Therefore, the difference of cell cycle of the IDE and the EK is related to the diversity of cusp patterning and would provide a new insight into tooth morphogenesis.

An Orthopantomographic study of hypodontia in permanent teeth of Iraqi patients

The congenital lack of one or more permanent teeth is a common anomaly in man .By definition, congenitally missing teeth are those that fail to erupt in the oral cavity and remain invisible in a radiograph, which implies this caused by disturbance during the early stages of tooth development.389 orthopantomograms of healthy patients were used the number of males were 194 and the number of females were 195.The patients has visited the hospital of college of dentistry of Baghdad university between 2006 and 2008.Thy were aged between 13 and 27years at the time the OPGs were taken .All OPGs were analyzed by viewer .The congenitally missing teeth were identify first clinically and confirm by the OPGsThe hypodontia mostly seen in upper lateral incisors, and lower second premolar, flowed by lower central incisors, upper central incisors, and lastly the lower lateral incisor, there were gender difference in hypodontia, but both genders show high percentage of upper lateral incisors hypodontia, 60.31%for males, and 72.30%for females. The hypodontia of lower second premolar in males 18.56%,and in females 14.5%.The hypodontia of upper central incisors in males 2.577%,and 0%in females. The hypodontia for lower central incisor in males 12.89%, and 13.3%in females. The hypodontia for lower lateral incisors in males 5.67%, and in females 0%.From these percentages it was clear that there were difference in hypodontia of upper and lower arches.To evaluate the frequency of hypodontia and compare its appearance between males and females and between upper and lower jaw.

Primordial odontogenic tumor: Subepithelial expression of Syndecan-1 and Ki-67 suggests origin during early odontogenesis.

Primordial odontogenic tumor (POT) is composed of variably cellular myxoid connective tissue, surrounded by cuboidal to columnar odontogenic epithelium resembling the inner epithelium of the enamel organ, which often invaginates into the underlying connective tissue. The tumor is delimited at least partially by a thin fibrous capsule. It derives from the early stages of tooth development. Syndecan-1 is a heparan sulfate proteoglycan that has a physiological role in several cellular functions, including maintenance of the epithelial architecture, cell-to-cell adhesion and interaction of cells with extracellular matrix, and with diverse growth factors, stimulating cell proliferation. Ki-67 is considered the gold standard as a cell proliferation marker. The aim of this study was to examine the expression of Syndecan-1 and Ki-67 proliferation index in POT and normal tooth germs to better understand the biological behavior of this tumor. Results showed that Syndecan-1 was more intensely expressed in subepithelial mesenchymal areas of POT, in a pattern that resembles the early stages of tooth development. The cell proliferation index (4.1%) suggests that POT is a slow growing tumor. Syndecan-1 expression in tooth germs in late cap and early bell stages was similar to POT, showing immunopositivity in subepithelial mesenchymal condensed areas. The immunohistochemical findings showed a pattern in which the population of subepithelial mesenchymal cells exhibited greater proliferative activity than the central portion of the dental papilla.

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.

Gene expression profiles in dental follicles from patients with impacted canines

Animal studies suggest that the dental follicle (DF) plays a major role in tooth eruption. However, the role of the DF during tooth impaction and related root resorptions in adjacent teeth is not clear. The hypothesis for the present study is that expression of regulatory factors involved in the bone remodelling process necessary for tooth eruption may differ between dental follicles from teeth with different clinical situations. We have analysed the gene expression profiles in the DF obtained from impacted canines, with (N = 3) or without (N = 5) signs of root resorption, and from control teeth (normal erupting teeth, mesiodens) (N = 3). DF from 11 patients (mean age: 13 years) obtains at the time of surgical exposure of the tooth. Due to the surgical time point, all teeth were in a late developmental stage. Gene expression related to osteoblast activation/bone formation, osteoclast recruitment and activation was analysed by RTqPCR. Genes related to bone formation (RUNX2, OSX, ALP, OCN, CX43) were highly expressed in all the samples, but osteoclast recruitment/activation markers (OPG, RANKL, MCP-1, CSF-1) were negligible. No apparent patterns or significant differences in gene expression were found between impacted canines, with or without signs of root resorption, or when compared to control teeth. Our results suggest the DF regulation of osteoclastic activity is limited in the late pre-emergent stage of tooth development, irrespective if the tooth is normally erupting or impacted. We suggest that the follicle may have an important regulatory function for alveolar bone formation in the final eruption process and CX43-gap junction communication could be an important signalling pathway.

Combination of Runx2 and Cbfβ upregulates Amelotin gene expression in ameloblasts by directly interacting with cis‑enhancers during amelogenesis.

Amelotin (Amtn) is a recently identified enamel protein secreted by ameloblasts at late stage of enamel development. Runt‑related transcription factor 2 (Runx2) in combination with the coactivator core‑binding factor β (Cbfβ) regulates the early stages of tooth development. The aim of the present study was to investigate the role of Runx2 in the regulation of Amtn gene expression in ameloblasts. Immunohistochemistry was performed and the results revealed that Runx2 protein was predominantly expressed in the nuclei of ameloblasts during the transition stage and the maturation stage of enamel development, whereas Cbfβ was expressed in ameloblasts from the secretory stage to the maturation stage. Reverse transcription‑quantitative polymerase chain reaction results demonstrated that Runx2 knockdown decreased Amtn expression in ameloblast‑lineage cells and co‑expression of Runx2 and Cbfβ in ameloblast lineage cells induced an upregulation in Amtn gene expression. Two putative Runx2‑binding sites within the Amtn promoter were identified using bioinformatics analysis. Results of an electrophoretic mobility shift assay and chromatin immunoprecipitation indicated that Runx2/Cbfβ bound to specific DNA sequences. Site‑directed mutagenesis of the Runx2 binding sites within the Amtn promoter resulted in decreased basal promoter activity and did not affect the overexpressed Runx2/Cbfβ. The results of the present study suggest that Runx2 upregulates Amtn gene expression via binding directly to Runx2 sites within the Amtn promoter during amelogenesis.

Zebrafish sp7 mutants show tooth cycling independent of attachment, eruption and poor differentiation of teeth

The capacity to fully replace teeth continuously makes zebrafish an attractive model to explore regeneration and tooth development. The requirement of attachment bone for the appearance of replacement teeth has been hypothesized but not yet investigated. The transcription factor sp7 (osterix) is known in mammals to play an important role during odontoblast differentiation and root formation. Here we study tooth replacement in the absence of attachment bone using sp7 zebrafish mutants. We analysed the pattern of tooth replacement at different stages of development and demonstrated that in zebrafish lacking sp7, attachment bone is never present, independent of the stage of tooth development or fish age, yet replacement is not interrupted. Without bone of attachment we observed abnormal orientation of teeth, and abnormal connection of pulp cavities of predecessor and replacement teeth. Mutants lacking sp7 show arrested dentinogenesis, with non-polarization of odontoblasts and only a thin layer of dentin deposited. Osteoclast activity was observed in sp7 mutants; due to the lack of bone of attachment, remodelling was diminished but nevertheless present along the pharyngeal bone. We conclude that tooth replacement is ongoing in the sp7 mutant despite poor differentiation and defective attachment. Without bone of attachment tooth orientation and pulp organization are compromised.

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.

Fascin in tooth germs: an immunohistochemical analysis

Development of a tooth is a complex process that involves three stages namely bud, cap and bell which results from the interaction of cells of oral mucosa and neural crest. During this process, oral and neural crest cells undergo various changes resulting in proliferation, apoptosis, morphological, and cyto-differentiation, which in turn would have changes in the cytoskeletal framework of the cell that includes actin and tubulin. Fascin is an actin-bundling protein that cross-links individual actin filaments into straight, compact, stiff bundles, which are crucial for the formation of finger-like membrane protrusions and aids in cell migration but is less explored in tooth germs. The aim of this study was analyze the expression and distribution of fascin in various stages of human tooth germs. Twenty human tooth germs were stained with hematoxylin and eosin and with immunohistochemical staining for fascin. Strong membranous expression for fascin was observed in various stages with decreased expression in stellate reticulum from cap stage to bell stage. Also, outer enamel epithelial cells had a weak fascin expression. Although cells of dental papilla did not express fascin in early cap stage of tooth development, strong expression of fascin was observed in later bell stages. It was also observed the inner enamel epithelium close to areas of calcification showed a decreased expression. Thus, the expression of fascin in various stages of tooth development being site and time specific may play an important role in cell remodulation.

Age determination by schour and massler method: A forensic study

Introduction: Age determination can be done by assessing the developmental and eruption status of dentition in the oral cavity. Schour and Massler studied the development of human dentition radiographically and histologically and put forward a chart explaining the stages of both deciduous and permanent teeth development in 21 stages. This chart is used in this study to estimate the age in the study population. Aim: The aim of the study was to check the efficacy of Schour and Massler method in determining the age of the study population using Schour and Massler chart of teeth development. Methodology: This study comprised of 62 panoramic images, taken from the department of oral medicine and radiology archives. Age was assessed by comparing the tooth developmental stages on panoramic radiographs with the standards using Schour and Massler chart. To check the accuracy of the present method, the actual age of the samples was matched with the dental age (DA) estimated by Schour and Massler method. Results: Data were statistically analyzed using paired t-test and correlation was done. It showed a strong correlation between the actual age and DA by Schour and Massler method. Conclusion: Schour and Massler method is a reliable method for age estimation in the study population.

Efficiency analysis of the improved method for the assessment of morphological stage of tooth development by the rentgenological signs

Efficiency analysis of the improved method for the assessment of morphological stage of tooth development by the rentgenological signs

Early Determination of the Periodontal Domain by the Wnt-Antagonist Frzb/Sfrp3.

Odontogenesis results from the continuous and reciprocal interaction between cells of the oral epithelium and cranial neural crest-derived mesenchyme. The canonical Wnt signaling pathway plays a fundamental role in mediating these interactions from the earliest stages of tooth development. Here we analyze by in situ hybridization the expression patterns of the extracellular Wnt antagonist Frzb/Sfrp3. Although Frzb is expressed in dental mesenchymal cells from the earliest stages of odontogenesis, its expression is absent from a tiny population of mesenchymal cells immediately adjacent to the invaginating dental epithelium. Cell proliferation studies using BrdU showed that the Frzb expressing and Frzb non-expressing cell populations display different proliferative behavior during the initial stages of odontogenesis. DiI-mediated cell-fate tracing studies demonstrated that the Frzb expressing cells contribute to the formation of the dental follicle, the future periodontium. In contrast, the Frzb non-expressing cells give rise to the dental pulp. The present results indicate that Frzb is discriminating the presumptive periodontal territory from the rest of the dental mesenchyme from the very beginning of odontogenesis, where it might act as a barrier for the diffusion of Wnt molecules, thus regulating the activation of Wnt-dependent transcription within dental tissues.

Three-dimensional mammalian tooth development using diceCT

ObjectiveThis study aims to develop the Diffusible Iodine-based Contrast-Enhanced CT (diceCT) method for non-destructive imaging of both soft and mineralised tissues. We sought to document the 3D spatio-temporal pattern of mammalian tooth development including multiple tooth classes and generations, using the tammar wallaby (Macropus eugenii) as a model species. DesignWe took microCT scans of developing fetuses and pouch young stained using Lugol’s Iodine (I2KI) contrast agent. Stained versus unstained specimen comparisons were then made to investigate whether staining had improved visualisation of structures. Scan slices were compared to histological sections to confirm the identity of tissues and structures. Tissue layers were digitally segmented to create 3D models. ResultsDiceCT dramatically enhanced visual contrast of soft tissues, allowing differentiation between epithelial and mesenchymal layers. Subvolume scans at higher magnification achieved single-cell layer resolution within relatively large intact heads. We observed in-situ initiating teeth, which progressed through major stages of tooth development including morphogenesis and mineralisation. In addition, we traced the development of other mineralized and unmineralised tissues, such as the cranial bones and the brain, eye and olfactory system. ConclusionsDiceCT was time- and cost-effective in producing complex 3D models of the entire dentition of the tammar wallaby at each developmental stage with tissue-level resolution. The 3D view of soft and mineralised tooth structures allowed us to define tooth class and generation from a developmental perspective. Additionally, the development of other organs can also be documented using the same scans, demonstrating the efficiency and versatility of this technique.