Stages Of Tooth Development Research Articles

Evaluation of electric pulp test thresholds and correct probe tip placement site in developing incisors: a clinical study in 1200 teeth.

Although electric pulp tests (EPT) may play a valuable diagnostic role in traumatized immature permanent teeth, the EPT threshold values which can be used as reference are not known. The aim of this study was to determine the average range of EPT threshold values in healthy permanent incisors according to their stage of root development. A total of 1200 permanent incisors were examined in 273 children (142 girls, 131 boys) aged 6-12years. Panoramic radiographs were used to group teeth according to the stage of root development. A digitest II pulp vitality tester (Parkell, Inc, Edgewood, NY) was used along with toothpaste as the conducting medium to determine sensibility on three different sites (incisal, middle and cervical third). In all teeth, mean EPT values showed a tendency to decrease along with advanced root development. Irrespective of the stage of root development, the lowest EPT values were obtained when measurements were made on the incisal third of the crown (p < 0.001). Mandibular incisors had lower mean response thresholds than their maxillary counterparts. The present findings provide reference EPT threshold values according to stage of tooth development to monitor the post traumatic pulp status of permanent incisors.

SURGICAL REMOVAL OF A RARE ODONTOGENIC TUMOR WITH AN IMPACTED CANINE FROM MAXILLA-A CASE REPORT AND REVIEW OF LITERATURE

Abstract: Odontogenic tumors exhibit different kind of histopathological features which are pertinent to the different stages of tooth development. The biologic behaviour of these lesions is varied from a hamartomatous lesion to a benign neoplasm or even to an aggressive malignant tumor. Ameloblastic fibro-odontomas (AFO) are benign mixed odontogenic tumor of the jaws. There are frequently considered together with ameloblastic fibroma because they appear to be slight variations of the same benign neoplastic process. A case of an ameloblastic fibro-odontoma of anterior maxilla is reported with relevant review of literature of clinicopathologic correlations.

Mesocrystalline Ordering and Phase Transformation of Iron Oxide Biominerals in the Ultrahard Teeth of Cryptochiton stelleri

Biological organisms naturally synthesize complex, hierarchical, multifunctional materials through mineralization processes at ambient conditions and under physiological pH. One such example is the ultrahard and wear‐resistant radular teeth found in mollusks, which are used to scape against the rock to feed on algae. Herein, the biologically controlled structural development of the hard, outer magnetite‐containing shell of the chitin teeth is revealed. Specifically, the formation of a series of mesocrystalline iron oxide phases, templated by chitin‐binding proteins, is identified. The initial domains, consisting of ferrihydrite mesocrystals with a spherulite‐like morphology, undergo a solid‐state phase transformation to form magnetite while maintaining mesocrystallinity, likely via a shear‐induced solid‐state reaction, without any noticeable architectural changes. Subsequent growth via Ostwald ripening leads to nearly single‐crystalline rod‐like elements. In addition, an interpenetrating organic matrix is identified that, at early stages of tooth development, potentially contains iron‐binding proteins that guide the self‐assembly of the mesocrystalline mineral and influence the preferred orientation of the later‐formed magnetite nanorods, which ultimately determines the mechanical behavior of the mature chiton teeth.

Pulse Oximetry and Three-Dimensional Analysis in Evaluating Immature Permanent Teeth Apexogenesis: Two Case Reports

Background: Apexogenesis is a vital pulp therapy that aims to preserve pulp vitality and maintain root formation in not-fully-formed permanent teeth with exposed pulp from trauma or caries. To achieve success, reliable diagnostic tools are required to assess the pulp health and tooth development stage, design an appropriate treatment plan and evaluation, and follow-up. Pulse oximetry is a non-invasive method for monitoring pulp oxygen saturation, which corresponds to pulp vitality. Case Presentation: This case report describes the successful apexogenesis of two pulp exposure-immature permanent teeth treated with acemannan, an implantable natural biomaterial extracted from aloe vera. Based on pulp oxygen saturation level, clinical evaluation, and radiographic examination, the teeth were asymptomatic with preserved pulp vitality and continued root development. Conclusion: Therefore, as an auxiliary tool, pulse oximetry could be useful for diagnosis, treatment, and follow-ups of apexogenesis therapy.

Age estimation of Hispanic children in the United States: Development and validation of dental reference dataset based on two staging systems

Dental tissues follow a systematic pattern of development and several radiological methods have been developed and validated. This study aims to develop and validate a reference data set (RDS) for dental development of Hispanic children and to compare the mean age using the Demirjian and Moorrees tooth developmental stage (TDS) systems. A total of 600 Dental Panoramic Tomographs (DPTs) of Hispanic children aged 6 to 17 years were obtained and reference datasets (RDS) were developed by scoring all the maxillary and mandibular teeth in the left side of the arch according to the Demirjian (8 stage) and Moorrees (14 stage) scoring systems. To validate the RDS, 120 (DPTs) separate from the RDS were randomly selected, and dental ages were calculated from the RDS using unweighted and five weighted mean average methods. Statistical significance was set at p < 0.05, and a paired t-test was conducted to compare the difference between Chronological Age (CA) and Dental Age (DA) for each weighting method. For the 8-stage system, the mean (sd, se) difference between CA and DA for the unweighted method was 0.04 (0.51, 0.065) years for males, and 0.07 (0.41, 0.053) years for females. The difference was not statistically significant for all five weighting methods (p > 0.05). For the 14-stage system, CA-DA for the unweighted method was 0.17 (0.33, 0.042) years for males, and 0.13 (0.41, 0.053) years for females. The difference was statistically significant for most of the Moorrees methods (p < 0.05). Dental age derived from the unweighted average method using the reference dataset derived from Demirjian’s 8-stage system is recommended for dental age estimation in Hispanic children and adolescents.

Prevalence and distribution of selected developmental dental anomalies in Taif, Saudi population.

Background: Developmental dental anomalies are seen as abnormalities in tooth size, shape, position, and structure due to multiple reasons during various stages of tooth development. These anomalies can create disturbances in dental arch lengths and occlusions. Hence, it is very important to treat, recognise and perform proper treatment. The purpose of this study was to find out the prevalence and distribution of selected developmental anomalies in shape, size and position of teeth in the Saudi population of Taif Region.Design and Methods: The study was based on the clinical examination of 2481 adults who are Saudi nationals came for dental treatment from September 2019 to February 2020, at Taif University Dental Hospital, Saudi Arabia. These patients were examined clinically for developmental dental anomalies affecting shape, size and position.Results:We found that a total of 512 individuals (20.63%) had developmental anomalies and out of which 386 persons (15.56%) had at least one developmental dental anomaly. The frequency and distribution of anomalies of shape and size, number and position were 46.8%, 26.9% and 42.9% respectively. In the present study, 15.56% individuals exhibited at least one anomaly, 8.54% subjects had more than one anomaly and 79.36%.did not any developmental anomaly. On comparison, statistically significant results were seen between different groups of anomalies.Conclusions: The present study had varying results for the prevalence rate of selected dental anomalies. This variation in results might be due racial differences or discrepancy in sample size or/and diagnostic or inclusion criteria. Treatment of developmental anomalies necessitates a multidisciplinary approach and mostly may comprise of orthodontic correction or prosthetic replacement. Significance for public health The assessment of prevalence and distribution of dental anomalies in the Kingdom of Saudi Arabia is very much required. These dental anomalies are significant and show no symptoms, seen on careful examination. These mostly result in malocclusion, change in eruption, increased vulnerability to caries, compromised esthetics and problems in permanent teeth, difficulties in endodontic or surgical procedure of the affected tooth, so on. It is very essential to take care of these anomalies, if not can produce disturbances in maxillary and mandibular dental arch and occlusions. Further, these might pose complication in planning the orthodontic treatment. Hence to know the prevalence rate and distribution of such anomalies will help various dental faculties/specialists to identify and recognize prevailing dental anomalies early and perform proper treatment planning. There are no such studies in adult populations of Saudi Arabia. This study has indicated that about 20% of the participants had dental anomalies and was observed more in males of about 63.3%.

Application of dental stem cells in three-dimensional tissue regeneration.

Dental stem cells can differentiate into different types of cells. Dental pulp stem cells, stem cells from human exfoliated deciduous teeth, periodontal ligament stem cells, stem cells from apical papilla, and dental follicle progenitor cells are five different types of dental stem cells that have been identified during different stages of tooth development. The availability of dental stem cells from discarded or removed teeth makes them promising candidates for tissue engineering. In recent years, three-dimensional (3D) tissue scaffolds have been used to reconstruct and restore different anatomical defects. With rapid advances in 3D tissue engineering, dental stem cells have been used in the regeneration of 3D engineered tissue. This review presents an overview of different types of dental stem cells used in 3D tissue regeneration, which are currently the most common type of stem cells used to treat human tissue conditions.

Gas1 Regulates Patterning of the Murine and Human Dentitions through Sonic Hedgehog

The mammalian dentition is a serially homogeneous structure that exhibits wide numerical and morphological variation among multiple different species. Patterning of the dentition is achieved through complex reiterative molecular signaling interactions that occur throughout the process of odontogenesis. The secreted signaling molecule Sonic hedgehog (Shh) plays a key role in this process, and the Shh coreceptor growth arrest-specific 1 (Gas1) is expressed in odontogenic mesenchyme and epithelium during multiple stages of tooth development. We show that mice engineered with Gas1 loss-of-function mutation have variation in number, morphology, and size of teeth within their molar dentition. Specifically, supernumerary teeth with variable morphology are present mesial to the first molar with high penetrance, while molar teeth are characterized by the presence of both additional and absent cusps, combined with reduced dimensions and exacerbated by the presence of a supernumerary tooth. We demonstrate that the supernumerary tooth in Gas1 mutant mice arises through proliferation and survival of vestigial tooth germs and that Gas1 function in cranial neural crest cells is essential for the regulation of tooth number, acting to restrict Wnt and downstream FGF signaling in odontogenic epithelium through facilitation of Shh signal transduction. Moreover, regulation of tooth number is independent of the additional Hedgehog coreceptors Cdon and Boc, which are also expressed in multiple regions of the developing tooth germ. Interestingly, further reduction of Hedgehog pathway activity in Shhtm6Amc hypomorphic mice leads to fusion of the molar field and reduced prevalence of supernumerary teeth in a Gas1 mutant background. Finally, we demonstrate defective coronal morphology and reduced coronal dimensions in the molar dentition of human subjects identified with pathogenic mutations in GAS1 and SHH/GAS1, suggesting that regulation of Hedgehog signaling through GAS1 is also essential for normal patterning of the human dentition.

Dental disorders in patients recovered from malignant neoplasms in childhood

During the development of the bodyʼs homeostatic systems, anticancer drugs and radiation affect both tumor cells and healthy tissues. Damage to tissues with low potential for restorative functions, such as teeth, leads to a high probability of irreversible changes. The purpose of this literature review is to provide information on dental defects resulting from anticancer treatment. The most common anomalies in the development of teeth include a violation of the number, size, shape, mineralization of teeth, defects of dentin and enamel. The effect of a number of chemotherapeutic drugs has been studied in animal models and include a deficiency and thinning of the roots of the teeth. Irradiation leads to a wider spectrum of dental pathology: the integritation of the teeth changes, craniofacial dysmorphism, post-radiation mandibular hypomobility, damage to the salivary glands, the risk of developing osteoradionecrosis. The extent and severity of these effects depends from the child's age type of tumor and the radiation dose. The stage of tooth development is critical. Patients who received hematopoietic stem cell transplantation (HSCT) before the age of 3 have a higher risk of dental disorders and anomalies in the development and growth of the face. Radiation therapy plays a leading role in the formation of caries. The study of the long-term effects of radiation therapy, chemotherapy, HSCT on the development of dental complications is of interest to identify the most vulnerable groups of patients in order to ensure the possibility of early intervention and improve the quality of life.

Spatiotemporal Changes in Transcriptome of Odontogenic and Non-odontogenic Regions in the Dental Arch of Mus musculus.

Over the past 40 years, studies on tooth regeneration have been conducted. These studies comprised two main flows: some focused on epithelial–mesenchymal interaction in the odontogenic region, whereas others focused on creating a supernumerary tooth in the non-odontogenic region. Recently, the scope of the research has moved from conventional gene modification and molecular therapy to genome and transcriptome sequencing analyses. However, these sequencing data have been produced only in the odontogenic region. We provide RNA-Seq data of not only the odontogenic region but also the non-odontogenic region, which loses tooth-forming capacity during development and remains a rudiment. Sequencing data were collected from mouse embryos at three different stages of tooth development. These data will expand our understanding of tooth development and will help in designing developmental and regenerative studies from a new perspective.

Long-term follow-up in lower right second premolar tooth with a dental follicle but no tooth bud: A case report

Aim: The patient was followed up in consultation with the orthodontist, and after a long-term follow-up, it was found that the dental germ developed, but the position of the tooth was horizontal. When the follow-ups were continued, it was observed that the position of the tooth also improved, and it progressed smoothly along the tooth eruption path.&#x0D; Methodology: In the panoramic radiography of an 8-year-old male patient who applied to the clinic complaining about the left upper first primary molar tooth, the right lower permanent second premolar tooth follicle developed, but there was no tooth development in the follicle.&#x0D; Results: When follicle formation is observed, only following the patients without directing them to orthodontic treatment, which is expensive and difficult, positively affects their dental structure. Following patients without affecting their lives can be significant.&#x0D; Conclusion: We emphasize the importance of long-term follow-up when follicle formation was observed. We predicted that this situation was caused by the disconnection in the interaction of transcription factors and signals in the tooth development stage.&#x0D; &#x0D; How to cite this article: Sukurica Y, Çakır A. Long-term follow-up in lower right second premolar tooth with a dental follicle but no tooth bud: A case report. Int Dent Res 2021;11(Suppl.1):312-5. https://doi.org/10.5577/10.5577/intdentres.2021.vol11.suppl1.47&#x0D; &#x0D; Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

Comparative transcriptional profiling of canine acanthomatous ameloblastoma and homology with human ameloblastoma

Ameloblastomas are odontogenic tumors that are rare in people but have a relatively high prevalence in dogs. Because canine acanthomatous ameloblastomas (CAA) have clinicopathologic and molecular features in common with human ameloblastomas (AM), spontaneous CAA can serve as a useful translational model of disease. However, the molecular basis of CAA and how it compares to AM are incompletely understood. In this study, we compared the global genomic expression profile of CAA with AM and evaluated its dental origin by using a bulk RNA-seq approach. For these studies, healthy gingiva and canine oral squamous cell carcinoma served as controls. We found that aberrant RAS signaling, and activation of the epithelial-to-mesenchymal transition cellular program are involved in the pathogenesis of CAA, and that CAA is enriched with genes known to be upregulated in AM including those expressed during the early stages of tooth development, suggesting a high level of molecular homology. These results support the model that domestic dogs with spontaneous CAA have potential for pre-clinical assessment of targeted therapeutic modalities against AM.

The Genetic, Epigenetic, and Environmental Factors of Dental Abnormalities Development: Literature Review

Proper anamnesis of clinical practice in giving clear diagnosis is important for specific possible dental care. Disturbance in tooth development by any aetiological factors result in dental anomalies. The variation aetiologies of the dental anomaly are diverse but mainly caused by three main factors which are genetic, epigenetic, and environmental. From genetic mechanisms, where parents or siblings have a specific pattern of tooth, a bigger probability for an individual to have the same tooth pattern with his relatives, included gender differences. Based on epigenetic mechanisms, environmental chemicals, pharmaceuticals, aging, and dietary intake are a few factors that made up a tooth pattern. Repeated signaling molecules which received by protein receptor and induced by transcription factors between epithelial and mesenchyme in tooth development stages are relayed to transcript continued process of tooth development and become tooth anomalies. Orthodontists can be the ones to first diagnose and aware of the etiology and related characteristics with dental anomalies and further can cause malocclusion. An optimal and efficient integrated treatment plan of these anomalies should include the genetic profile of an individual to understand the developmental process and the aetiological factors for specific possible dental care. This paper aims to inform about the genetic, epigenetic, and environmental factors that involve in dental abnormalities development.

Dental effects of enzyme replacement therapy in case of childhood-type hypophosphatasia

BackgroundHypophosphatasia (HPP), a skeletal disease characterized by hypomineralization of bone and teeth, is caused by an ALPL gene mutation that leads to low activity of the tissue non-specific alkaline phosphatase enzyme. Although enzyme replacement therapy (ERT) was recently introduced for affected patients, no known studies have been reported regarding its dental effects related to permanent teeth and jaw bones. In the present study, we examined the dental effects of ERT in a case of childhood-type hypophosphatasia, including panoramic radiography findings used to estimate the dental age of permanent teeth and mandibular bone density. Furthermore, the effects of that therapy on the periodontal condition of the patient were evaluated by comparing periodontal pocket depth before and after initiation.Case presentationAn 11-year-1-month-old boy was referred to our clinic for consultation regarding oral management. Two primary incisors had spontaneously exfoliated at 1 year 8 months old and he had been diagnosed with childhood-type HPP at the age of 2 years 2 months. Obvious symptoms were localized in the dental region at the time of diagnosis, though later extended to other parts of the body such as bone pain. ERT was started at 11 years 7 months of age, after which bone pain disappeared, and motor functions and activities of daily living improved. We estimated dental age based on tooth development stage. The age gap between chronological and dental ages was expanded before treatment, and then showed a constant decrease after ERT initiation and finally disappeared. The index for mandibular bone density (mandibular cortical width / length from mesial buccal cusp to apex of first molar) was increased after ERT initiation. Furthermore, the periodontal condition for all teeth except those exfoliated was stable after starting therapy.ConclusionsERT resulted in improved tooth and mandibular bone mineralization, with notably good effects on teeth under formation. Acceleration of mineralization of roots associated with erupting teeth leads to stabilization of the periodontal condition. We concluded that ERT contributed to the improved dental condition seen in this patient.

Periostin in Periodontics: A Brief Insight

The prime objective of the periodontal treatment is to re-establish the lost periodontal tissue by forming new attachment of periodontal ligament, cementum and the alveolar bone. Periostin is a matricellular protein with its structure closely resembling to that of Drosophila fasciclin. It is expressed in the periodontal ligament, periosteum, alveolar bone, adipose tissue as well as skeletal tissue and has a key role in role in tooth development. This protein molecule has a striking similarity to the molecule beta ig-h3 which is induced by transforming growth factor beta (TGF-beta), promotes the adhesion and spreading of fibroblasts and aids in collagen formation. It is possibly involved in the post surgical regeneration of periodontal hard and soft tissues. Periostin is also linked to dental papilla cells and is associated with hard tissue formation stages of tooth development. This mini review focuses on the various aspects of periostin related to maintenance and development of collagen rich connective tissues around the teeth. Keywords: Periostin, Periodontal ligament, Periodontal regeneration, Alveolar bone.

Radiographic Examination of Third Molar Development for Biological Age Assessment in Java Population, Indonesia

Background: The individual age as documented in the birth certificate shall be authorized as a chronologicalage. In several countries, falsification of documents relating to an individual age is becoming a major problem,since it is correlated with monetary, marriage, and education matter. Forensic dentistry works to minimizethe possibility of individual age falsification by studying the tooth developmental stages. The objective ofthis study is to observe the applicability of the third molar development related to the biological age.Materials and Methods: A total of 93 OPG (orthopantomogram) of subjects (16 – 23 years old) from theJava population were involved in this study. Third molar developmental stages of the mandibular wereevaluated using the Demirjian et al. method. The statistical analysis was carried out using IBM® SPSS®Statistics version 23.0 (IBM, Armonk, NY, USA).Results and Conclusion: The result showed that the average Java population reached the final stage at anaverage age of 21 ± 1,39 years in females and 20 ± 1,9 years in males. The present study indicates that thedevelopment of mandibular third molar is slightly earlier in males than in females. Besides, Demirjian’smethod is considered as a reliable method for dental age estimation in the Java population.

Characterization of Wolf‐Hirschhorn Syndrome Candidate 1 ( Whsc1 ) in Pitx2 ‐ miR‐23/24 ‐mediated Tooth Development

Objective Wolf-Hirschhorn syndrome (WHS) is a developmental disorder attributed to a partial deletion on the short arm of chromosome 4. WHS patients suffer from oral manifestations including cleft lip and palate (CLP), hypodontia and taurodontism. However, the causative factors and underlying mechanisms of these oral anomalies are relatively unknown. Wolf-Hirschhorn syndrome candidate 1 (WHSC1) is a H3K36-specific methyltransferase that is frequently deleted in WHS. This gene has been associated with craniofacial defects including CLP and defects in occipital ossification. In our study, we aim to understand the role of WHSC1 in tooth development. Methods To characterize the role of Whsc1 in tooth development, we profiled the Whsc1 expression pattern during mouse tooth development by immunofluorescence staining (IF). To investigate the regulatory effects between Whsc1 and Pitx2, we overexpressed either Whsc1 or Pitx2 in oral epithelial cell line LS8 and detected their expression. Then, ChIP-PCR and luciferase assays were performed to confirm the binding on the promoter regions. To determine the negative regulation of Whsc1 by miR-23-3p and miR-24-3p, miRs were inhibited by our Plasmid-based microRNA inhibition system in PMIS-miR-23-27-24 embryos and LS8 cells followed by detecting the mRNA and protein level of Whsc1. Luciferase assays were also conducted to confirm the direct binding between miRs and Whsc1 3’UTR. Results Whsc1 expresses from early stage of tooth development and restricts to stem cell niches in homeostatic tooth germ. Whsc1 and Pitx2 reciprocally activate each other's expression through chromosomal and transcriptional regulation. miR-23-3p and miR-24-3p, two miRs that regulated by Pitx2, directly inhibit Whsc1. Conclusion Whsc1 expresses in the developing tooth germ and participates the Whsc1-Pitx2-miR23/24 regulatory network in oral epithelium cells. Our observations provide new insights into the potential role of Whsc1 in regulating tooth development and a possible causer of the dental defects in WHS.

Dental age estimation: Development and validation of a reference data set for Kuwaiti children, adolescents, and young adults

ObjectivesThis study was designed to establish a Reference Data Set for Dental Age Estimation of young Kuwaiti subjects. DesignDental Panoramic Tomographs of 1393 Kuwaiti children, adolescents, and young adults aged between 3 and 26 years were re-used to establish a Reference Data Set. The Tooth Development Stages described by Demirjian et al. in 1973 was used to assess all the teeth on the left side of the Maxilla and the Mandible. The Accuracy and Precision of Dental Age Estimation for Kuwaiti children and adolescents was investigated by calculating the age of children using 50 females and 50 males of known age separate from the main study sample. This was the Validation Sample. Summary data for the individual Tooth Development Stages, comprising the number, mean, and standard deviation were used to estimate the age of the subjects in the Validation Sample using the Simple Average Method to calculate the Dental Age. ResultsThere was no statistically significant difference between the Chronological Age and the Dental Age in males with a mean difference of 0.14 years (1.75 months). The difference in females was significant at −0.33 years (−4.1 months). ConclusionsThese data demonstrate that estimated Dental Age in Kuwaiti females is close, just over 4 months, and is very close, in males within 1.75 months of the Chronologic Age.

Distinct tooth regeneration systems deploy a conserved battery of genes

BackgroundVertebrate teeth exhibit a wide range of regenerative systems. Many species, including most mammals, reptiles, and amphibians, form replacement teeth at a histologically distinct location called the successional dental lamina, while other species do not employ such a system. Notably, a ‘lamina-less’ tooth replacement condition is found in a paraphyletic array of ray-finned fishes, such as stickleback, trout, cod, medaka, and bichir. Furthermore, the position, renewal potential, and latency times appear to vary drastically across different vertebrate tooth regeneration systems. The progenitor cells underlying tooth regeneration thus present highly divergent arrangements and potentials. Given the spectrum of regeneration systems present in vertebrates, it is unclear if morphologically divergent tooth regeneration systems deploy an overlapping battery of genes in their naïve dental tissues.ResultsIn the present work, we aimed to determine whether or not tooth progenitor epithelia could be composed of a conserved cell type between vertebrate dentitions with divergent regeneration systems. To address this question, we compared the pharyngeal tooth regeneration processes in two ray-finned fishes: zebrafish (Danio rerio) and threespine stickleback (Gasterosteus aculeatus). These two teleost species diverged approximately 250 million years ago and demonstrate some stark differences in dental morphology and regeneration. Here, we find that the naïve successional dental lamina in zebrafish expresses a battery of nine genes (bmpr1aa, bmp6, cd34, gli1, igfbp5a, lgr4, lgr6, nfatc1, and pitx2), while active Wnt signaling and Lef1 expression occur during early morphogenesis stages of tooth development. We also find that, despite the absence of a histologically distinct successional dental lamina in stickleback tooth fields, the same battery of nine genes (Bmpr1a, Bmp6, CD34, Gli1, Igfbp5a, Lgr4, Lgr6, Nfatc1, and Pitx2) are expressed in the basalmost endodermal cell layer, which is the region most closely associated with replacement tooth germs. Like zebrafish, stickleback replacement tooth germs additionally express Lef1 and exhibit active Wnt signaling. Thus, two fish systems that either have an organized successional dental lamina (zebrafish) or lack a morphologically distinct successional dental lamina (sticklebacks) deploy similar genetic programs during tooth regeneration.ConclusionsWe propose that the expression domains described here delineate a highly conserved “successional dental epithelium” (SDE). Furthermore, a set of orthologous genes is known to mark hair follicle epithelial stem cells in mice, suggesting that regenerative systems in other epithelial appendages may utilize a related epithelial progenitor cell type, despite the highly derived nature of the resulting functional organs.

Assessment of maturation indicators in individuals with different skeletal malocclusion.

The aim of this study was to comparatively evaluate hand-wrist bones, cervical vertebrae and tooth development stages according to skeletal classification. The orthodontic initial records of 297patients were used and separated into three groups according to the skeletal malocclusion. Three groups including 99people each were sampled representing malocclusions with Angle classesI, II and III, respectively. The panoramic, cephalometric and hand-wrist radiographs of all patients included in this study were used to compare dental and skeletal maturation indicators. Calcification of teeth was rated according to the system of Demirjian. To evaluate the stage of skeletal maturation hand-wrist radiographs were analyzed according to the Grave and Brown method. Also, Hassel and the Farman method was used to classifying vertebral developmental stages. Spearman rank correlation tests, as well as Fisher exact χ2 tests with r×c tables, were used for the comparison of categorical variables. Hand-wrist, vertebral and dental development stages showed astatistically significant relationship (p < 0.01) for both genders and in all malocclusions. The association between the different maturation indicators used in this study and the type of malocclusion was also statistically significant for both genders. It was observed that the peak period of skeletal maturation according to the hand-wrist radiograph findings correlated with the cervical vertebrae stage C3 in girls (63.2%) and C2-C3 in boys (43.5-43.5%). The weakest correlation was seen between the dental development stages and the skeletal developmental stages in the classII group (r = 0.443-0.220 [girls]; r = 0.604-0.410 [boys]). The use of the dental development stage as areliable indicator of maturation was limited. According to the Demirjian method, the calcification stage of the second molar might indicate that the individual is in the pubertal peak period.