Molar Development Research Articles

Magnetic Resonance Images for the Prediction of Chronological Age Using Maxillary Third Molar Teeth: An Observational Study.

Dental age estimation using third molars is a reliable method for estimating the age of individuals. Recently, magnetic resonance imaging (MRI) of the head and neck has been found to be applicable for age estimation of third molar teeth. In the present study, we aimed to apply the Modified Demirjian method of age estimation to magnetic resonance (MR) image sections for dental age estimation by determining the mineralization patterns of the maxillary third molars. MRI scans of the patients were performed using SIGNA™ 3.0Tesla MRI GE Healthcare (Chicago, USA) with a moving, multifunctional coil. Two expert radiologists with more than three years of experience independently analyzed the image sections using the open-source Digital Imaging and Communications in Medicine (DICOM) viewer software. The age and sex of the patients whose images were included in the study were recorded using a specially designed proforma. The stage of development of the maxillary third molars was determined using the modified Demirjian method. Inter observer agreement was calculated using the intra class correlation coefficient. Simple linear regression analysis was used to predict the actual age at the third molar development stage. There was excellent agreement between observers (ICC =0.99 (95% CI = 0.98-0.99)). There was also a significant association between the maxillary third molar tooth development stage and chronological age of the individual (P=0.001; B=1.54; 95% CI = 0.71-2.37). The findings from the present study establish that the Modified Demirjian method can also be reliably applied for dental age assessment in MR sections.

Region-specific gene expression profiling of early mouse mandible uncovered SATB2 as a key molecule for teeth patterning

Mammalian dentition exhibits distinct heterodonty, with more simple teeth located in the anterior area of the jaw and more complex teeth situated posteriorly. While some region-specific differences in signalling have been described previously, here we performed a comprehensive analysis of gene expression at the early stages of odontogenesis to obtain complete knowledge of the signalling pathways involved in early jaw patterning. Gene expression was analysed separately on anterior and posterior areas of the lower jaw at two early stages (E11.5 and E12.5) of odontogenesis. Gene expression profiling revealed distinct region-specific expression patterns in mouse mandibles, including several known BMP and FGF signalling members and we also identified several new molecules exhibiting significant differences in expression along the anterior–posterior axis, which potentially can play the role during incisor and molar specification. Next, we followed one of the anterior molecules, SATB2, which was expressed not only in the anterior mesenchyme where incisor germs are initiated, however, we uncovered a distinct SATB2-positive region in the mesenchyme closely surrounding molars. Satb2-deficient animals demonstrated defective incisor development confirming a crucial role of SATB2 in formation of anterior teeth. On the other hand, ectopic tooth germs were observed in the molar area indicating differential effect of Satb2-deficiency in individual jaw regions. In conclusion, our data provide a rich source of fundamental information, which can be used to determine molecular regulation driving early embryonic jaw patterning and serve for a deeper understanding of molecular signalling directed towards incisor and molar development.

Hypoxia-inducible factors in postnatal mouse molar dental pulp development: insights into expression patterns, localisation and metabolic pathways.

Hypoxia is relevant to several physiological and pathological processesand this also applies for the tooth. The adaptive response to lowering oxygen concentration is mediated by hypoxia-inducible factors (HIFs). Since HIFs were shown to participate in the promotion of angiogenesis, stem cell survival, odontoblast differentiation and dentin formation, they may play a beneficial role in the tooth reparative processes. Although some data were generated in vitro, little is known about the in vivo context of HIFs in tooth development. In order to contribute to this field, the mouse mandibular first molar was used as a model.The expression and in situ localisation of HIFs were examined at postnatal (P) days P0, P7, P14, using RT-PCR and immunostaining. The expression pattern of a broad spectrum of hypoxia-related genes was monitored by customised PCR Arrays. Metabolic aspects were evaluated by determination of the lactate level and mRNA expression of the mitochondrial marker Nd1.The results show constant high mRNA expression of Hif1a, increasing expression of Hif2a, and very low expression of Hif3a during early postnatal molar development. In the examined period the localisation of HIFs in the nuclei of odontoblasts and the subodontoblastic layer identified their presence during odontoblastic differentiation. Additionally, the lower lactate level and higher expression of mitochondrial Nd1 in advanced development points to decreasing glycolysis during differentiation. Postnatal nuclear localisation of HIFs indicates a hypoxic state in specific areas of dental pulp as oxygen demands depend on physiological events such as crown and root dentin mineralization.

Dental Age Assessment Based on Developmental Stages and Maturity Index of Third Molars for Medico-Legal Purposes.

As results may vary depending on the method of examination, this paper analyzes methods of age estimation based on the maturation index of third molars (I3M) and Kohler's developmental stages in living individuals. A total of 1475 orthopantomograms were analyzed. The results showed that the development of third molars tended to be more advanced in males than in females. Regression equations that included the value of the developmental stage of the left third molar most accurately predicted chronologic age in males and females. Using the I3M method, there were no statistically significant bilateral differences between the mandibular right and left third molars. Overall, 82.92% of males and only 72.82% of females were correctly classified with the cut-off value (0.08) for the left mandibular third molar index. In addition, 81.97% of individuals were correctly classified as minors and adults using the Kohler method, while only 78.62% of individuals were correctly classified as minors and adults using the I3M method. Based on the misclassification of minors as adults, both methods should be used with caution and overestimation of age should be considered, especially for those close to 18 years of age.

Transcription factor activator protein 2C contribute to molar development in mice

Objective: Explore the expression pattern of transcription factor activator protein 2C (TFAP2C) and identify the roles of Tfap2c during tooth development. Methods: Real-time fluorescence quantitative PCR (RT-qPCR) was used to analyze the relative expression level of Tfap2c in various organs of embryonic day(E)14.5 mouse embryos and mouse molar germs at E12.5-E18.5 and postnatal day (P)0-P7. The expression position of Tfap2c in mouse molar germs was demonstrated by frozen section immunofluorescence staining. Cultured mandibular molar germs were transfected with control small interfering RNA (siRNA) or Tfap2c siRNA to evaluate the effect of Tfap2c on tooth molar germs development, and RT-qPCR was used to detect the relative expression level of genes related to odontoblast expression. Dental mesenchymal cells were isolated from E14.5 molar germs and transfected with control siRNA or Tfap2c siRNA, cell counting kit 8 (CCK-8) and scratch healing test were applied to detect dental mesenchymal cell viability and migration. Results: Tfap2c was highly expressed in the early development period of mouse molar germs. Tfap2c was expressed in the epithelial and mesenchymal tissues of E13.5 mouse molar germs and there was no significant difference of relative expression of Tfap2c between them (t=1.06, P=0.472). Tfap2c was expressed in mesenchymal tissues of E14.5 mouse molar germs and the relative expression of Tfap2c in mesenchymal tissues was significantly higher than epithelial tissues (t=37.29, P<0.0001). For molar germs transfected with Tfap2c siRNA, the relative height of cusps (0.708±0.171) and the ratio of cusp height and crown height (0.321±0.068) was significantly lower than control group (1.000±0.287 and 0.483±0.166) (t=2.79, P=0.012; t=2.85, P=0.015). But there was no significant difference in relative height (1.078±0.206, 0.993±0.254, t=0.83, P=0.419)and relative width (1.000±0.116, 0.999±0.122, t=0.01, P=0.992) of crowns between two groups. The relative expression level of genes related to odontoblast expression was decreased (Dspp: t=15.33, P<0.001; Dmp1: t=13.81, P<0.001). Tfap2c siRNA hinders cell migration in dental mesenchymal cells (t=29.86, P=0.001), but there was no significant difference in CCK-8 absorbance value between two groups. The relative expression level of genes related to odontoblast expression was also decreased in dental mesenchymal cells transfected with Tfap2c siRNA (Dspp: t=3.86, P=0.031; Dmp1; t=4.36, P=0.022). Conclusions: Tfap2c highly expressed in the early morphogenesis period of mouse molar germs, mainly in mesenchymal tissues. Tfap2c affected the cusps formation of mouse molar germs and migration of dental mesenchymal cells.

Vole genomics links determinate and indeterminate growth of teeth.

Continuously growing teeth are an important innovation in mammalian evolution, yet genetic regulation of continuous growth by stem cells remains incompletely understood. Dental stem cells responsible for tooth crown growth are lost at the onset of tooth root formation. Genetic signaling that initiates this loss is difficult to study with the ever-growing incisor and rooted molars of mice, the most common mammalian dental model species, because signals for root formation overlap with signals that pattern tooth size and shape (i.e., cusp patterns). Different species of voles (Cricetidae, Rodentia, Glires) have evolved rooted and unrooted molars that have similar size and shape, providing alternative models for studying roots. We assembled a de novo genome of Myodes glareolus, a vole with high-crowned, rooted molars, and performed genomic and transcriptomic analyses in a broad phylogenetic context of Glires (rodents and lagomorphs) to assess differential selection and evolution in tooth forming genes. We identified 15 dental genes with changing synteny relationships and six dental genes undergoing positive selection across Glires, two of which were undergoing positive selection in species with unrooted molars, Dspp and Aqp1. Decreased expression of both genes in prairie voles with unrooted molars compared to bank voles supports the presence of positive selection and may underlie differences in root formation. Bulk transcriptomics analyses of embryonic molar development in bank voles also demonstrated conserved patterns of dental gene expression compared to mice, with species-specific variation likely related to developmental timing and morphological differences between mouse and vole molars. Our results support ongoing evolution of dental genes across Glires, revealing the complex evolutionary background of convergent evolution for ever-growing molars.

A fully automated classification of third molar development stages using deep learning

Accurate classification of tooth development stages from orthopantomograms (OPG) is crucial for dental diagnosis, treatment planning, age assessment, and forensic applications. This study aims to develop an automated method for classifying third molar development stages using OPGs. Initially, our data consisted of 3422 OPG images, each classified and curated by expert evaluators. The dataset includes images from both Q3 (lower jaw left side) and Q4 (lower right side) regions extracted from panoramic images, resulting in a total of 6624 images for analysis. Following data collection, the methodology employs region of interest extraction, pre-filtering, and extensive data augmentation techniques to enhance classification accuracy. The deep neural network model, including architectures such as EfficientNet, EfficientNetV2, MobileNet Large, MobileNet Small, ResNet18, and ShuffleNet, is optimized for this task. Our findings indicate that EfficientNet achieved the highest classification accuracy at 83.7%. Other architectures achieved accuracies ranging from 71.57 to 82.03%. The variation in performance across architectures highlights the influence of model complexity and task-specific features on classification accuracy. This research introduces a novel machine learning model designed to accurately estimate the development stages of lower wisdom teeth in OPG images, contributing to the fields of dental diagnostics and treatment planning.

Prevalence of mandibular asymmetries in the pediatric population of Jazan: A radiographic analytical study

BackgroundFacial asymmetry results from variation in mandibular linear and angular dimensions on the right and left sides of the face. Mandibular asymmetry is of great significance to oral surgeons and orthodontists as it directly impacts the facial profile of an individual. AimThe present study aimed to measure the prevalence of mandibular asymmetry and its fluctuations during the mixed dentition growth phase in healthy children aged 6–8 years in the Jazan region of Saudi Arabia. MethodThis retrospective observational study was conducted by measuring linear asymmetrical measurements of mandible on orthopantomograms of 390 healthy children (182 boys and 208 girls, aged 6–8 years) with mixed dentition. Linear measurements from orthopantomograms were obtained using a standardized digitizer. Two sets of mandibular measurements were recorded, alongside subjective assessments of mandibular first molar development. An independent t-test was employed to assess the significance between measurements on both sides, while one-way ANOVA was used to demonstrate facial asymmetry significance among different age groups. ResultThe result of this study revealed a significant statistical difference (p-value≤ 0.05) for both sides of the mandible across two dimensions: condylar and ramus height (p value = 0.03) and mandibular length (p value = 0.04). The asymmetry index resulted in no asymmetry among most of the included subjects. However, compared to the other three linear measurements, many seven-year-old participants possess mandibular asymmetry on condylar height (54.5 %). ConclusionWithin the limitation it could be concluded that children in growing age have a significant mandibular asymmetry (mainly 7 years), which, however, is only seldom clinically significant. Hence, treatment plan should be cautiously planned.

Third molar eruption in dental panoramic radiographs as a feature for forensic age assessment – new reference data from a German population

Forensic age assessment in the living can provide legal certainty when an individual’s chronological age is unknown or when age-related information is questionable. An established method involves assessing the eruption of mandibular third molars through dental panoramic radiographs (PAN). In age assessment procedures, the respective findings are compared to reference data. The objective of this study was to generate new reference data in line with the required standards for mandibular third molar eruption within a German population. For this purpose, 605 PANs from 302 females and 303 males aged 15.04 to 25.99 years were examined. The PANs were acquired between 2013 and 2020, and the development of the mandibular third molars was rated independently by two experienced examiners using the Olze et al. staging scale from 2012. In case of disagreement in the assigned ratings, a consensus was reached through arbitration. While the mean, median and minimum ages were observed to increase with each stage of mandibular third molar eruption according to the Olze method, there was considerable overlap in the distribution of age between the stages. The minimum age for stage D, which corresponds to complete tooth eruption, was 16.1 years for females and 17.1 years for males. Thus, the completion of mandibular third molar eruption was found in both sexes before reaching the age of 18. In all individuals who had at least one tooth with completed eruption and who were younger than 17.4 years of age (n = 10), mineralization of the teeth in question was not complete. Based on our findings, the feature of assessing mandibular third molar eruption in PAN cannot be relied upon for determining age of majority.

Age estimation using the Demirjian method in third molars on cone beam computed tomography images

The study aimed to estimate the chronologic age of individuals and whether they were aged under or over 18 years by using the Demirjian method on cone beam computed tomography (CBCT) images. The developmental stages of the third molars in the maxilla and mandible of 445 individuals aged between 9 and 26 years were evaluated as eight stages from A to H according to the Demirjian method. The association of these eight stages with chronologic age according to the age of 18 years, which is accepted as the threshold value, and the distribution of the stages was statistically analyzed. There was no significant difference in the mean age at which developmental stages (A–H) were seen between the sexes (p > .05). Stage A was observed up to the age of 15 years in females and 14 years in males, and stage H was observed at the age of 16 at the earliest in both sexes. Stages A and B were not seen in individuals aged 18 years and over. The age of individuals and whether they are below or above 18 years can be estimated by evaluating the development of third molars according to the Demirjian method.

Effect of impaction on third molar development and age estimation – A study in a female black South African population

The impact of impaction on the development of third molars remains a subject of debate within the scientific literature, given the lack of consensus. Simultaneously, there has been a call for dental age estimation studies to consider population-specific factors. This research was conducted with the objective of examining the influence of impaction on the formation of third molars in a cohort of female individuals of black South African descent. The study population comprised 428 panoramic radiographs, focusing on females within the age range of 15 to 23.9 years. Within this sample, mandibular third molars were categorized based on their positioning into two groups: non-impacted and impacted. Dental development stages were assessed and classified according to Demirjian’s 8-level staging system. Descriptive statistics were performed. The outcomes of the independent t-test revealed statistically significant differences in developmental stages, specifically stage G for tooth #38 and stage F for tooth #48, suggesting that impaction had an impact on dental development, albeit not consistently across all developmental stages. Nonetheless, it's noteworthy that the minimum and mean ages across all developmental stages were higher among impacted teeth. In summary, our findings support the conclusion that mineralization of impacted mandibular third molars in South African female subjects proceeds at a slower pace compared to their non-impacted counterparts. Consequently, when estimating dental age in the context of South African females, it is advisable to prioritize non-impacted third molars whenever feasible.

The Early Iron Age elite grave from the Kapiteljska njiva barrow cemetery (Novo mesto, Slovenia): an approach to dental profiling through non-invasive and minimally-invasive techniques.

Kapiteljska njiva is a prehistoric cemetery located in the town of Novo mesto in southern Slovenia. There is a long history of archaeological research at this site, as the first investigations date back to the end of the 19th century. In 2004, an Early Iron Age barrow XVI was investigated. The oldest surviving grave in the barrow is the central grave, numbered XVI/34, which according to its position and the richness of the grave goods, belongs to a woman of higher status. Most likely, she was the first member or initiator of a family that continued to bury its dead in the barrow for the next 300 years. There were no preserved skeletal elements; however, in the head part of the grave, remains of human teeth, mostly the tooth crowns and the shells of enamel from the tooth crowns, were found among the scattered amber beads of a necklace. Moreover, these tooth remains are one of the few human biological materials (mostly fragments of skull and long limb bones) unearthed in this cemetery, reflecting the influence of acidic soil from the burial site. This study aimed to create a dental profile of the deceased in a similar way as during a forensic investigation. The remains were examined macroscopically and stereo-microscopically. The morphological traits were scored following the ASUDAS protocol. Ancestry was estimated by entering these scores into a beta version of the web-based application rASUDAS. Brothwell's system was used for age at death estimation from occlusal attrition. Identification of sex was based on the analysis of sex-specific amelogenin isoforms in dental enamel by nanoflow liquid chromatography tandem mass spectrometry (nanoLC-MS/MS). The present study reveals that the dental remains from Kapiteljska njiva belong to the permanent dentition of a single individual and that only the right upper central incisor and third molar are completely absent. The remains of teeth exhibit a simple external morphology, characterised by the absence of morphological dental traits, with a notable exception of the two-rooted left lower canine. The probability of assigning this individual to the Western Eurasian ancestry group is 98%. According to the degree of dentine exposure on the occlusal surfaces of molars, the estimated age range is 17-25 years. Another line of evidence comes from the observation that the first signs of approximal attrition are present in lower third molars but absent in the only preserved upper counterpart, indicating that the age at which the lower third molars entered into occlusion represents a proxy of the individual's age at death. Data on the chronology of the lower third molar development and eruption in present-day European populations from forensic literature (Brkić et al. 2011; Olze et al. 2008; Selmanagić et al. 2013) and The London Atlas confirm the above age-range estimate. Caution is, however, needed in the interpretation of results, because reference data are not based on the population of the individual's origin. Proteomic analysis classified the individual as a female, which is in line with the archaeological evidence. No pathological lesions or indicators of systemic stress were identified; however, the absence of approximal attrition facets in upper anterior teeth indicates interdental spacing. The results of dental profiling are discussed in the context of historical background, today's clinical knowledge, and epidemiological data.

Age Estimation Based on Cone-Beam Computed Tomography of the Spheno-Occipital Synchondrosis and Demirjian Method in an Iranian Population

Background: Spheno-occipital synchondrosis is a growth center that is involved in craniofacial development. Since osteogenesis of this synchondrosis occurs relatively later than other synchondroses, it has been taken into account for age estimation in forensics. This study aimed to evaluate spheno-occipital synchondrosis using Cone-Beam Computed Tomography (CBCT) in an Iranian population. Methods: In this cross-sectional study, 148 CBCT images (76 women and 72 men) of patients aged 7-25 years, with a mean age of 19.92±6.3 years, were assessed by two radiologists to analyze the spheno-occipital synchondrosis fusion degree using a four-stage system. In addition, the third molar development degree (Demirjian index) was assessed in panoramic and cross-sectional views of CBCT images. The correlation between spheno-occipital synchondrosis fusion degree and age was obtained. Multiple regression analysis was used for age estimation using spheno-occipital synchondrosis fusion degree and third molar development degree (Demirjian index). Intra-observer and inter-observer coefficients of agreements were also measured. IBM SPSS Statistics 20.0 was used. Results: There was a positive correlation between spheno-occipital synchondrosis fusion degree and age (r=0.75, p&lt;0.001). The multiple regression model provides a more robust model than when each age marker is utilized individually. The kappa coefficient was 0.53 for inter-observer agreement and 0.77-0.92 for intra-observer agreement. Conclusion: Assessing the four-stage spheno-occipital synchondrosis fusion degree was not a robust method; however, combined with the third molar development (Demirjian index), it could be considered as an appropriate marker for age estimation in 7-25-year-old Iranian population.

Mandibulotomy Technique and Permanent Molar Injury After Mandibular Distraction Osteogenesis in Infants.

The risk that mandibular distraction osteogenesis (MDO) poses to the developing mandibular dentition is well-known; however, less is understood about how the choice of instrumentation used for mandibular osteotomy might affect the development of permanent molars. Retrospective chart review examining infants with micrognathia who underwent MDO from 2010 to 2018 at a single tertiary care children's hospital using external, multivector devices. The first and second permanent mandibular molars were radiographically examined years after surgery to determine whether osteotomy cutting techniques affect the risk of injury to the permanent dentition. Thirty-seven infants and children underwent MDO from 2010 to 2018. Follow-up dental radiographs were available for 17 patients; 6 patients were excluded based on the use of preoperative computed tomography, utilization of virtual surgical planning technology, use of buried internal distractors, or older age at the time of distraction surgery. This yielded a total of 11 patients who underwent MDO with external hardware without virtual surgical planning representing 22 osteotomies. Sixteen osteotomies were performed using a side-cutting burr and 6 with a piezoelectric saw. The median age at distraction surgery was 3 weeks. The rate of an abnormal permanent first or second mandibular molar finding per osteotomy was 88% (14/16) in the side-cutting group versus 17% (1/6) with the piezoelectric technique (P = 0.004). Mandibular distraction osteogenesis risks injury to the mandibular molars; however, this study suggests a significant risk reduction in molar injury if the piezoelectric device is utilized.

Binary decisions of artificial intelligence to classify third molar development around the legal age thresholds of 14, 16 and 18 years

Third molar development is used for dental age estimation when all the other teeth are fully mature. In most medicolegal facilities, dental age estimation is an operator-dependent procedure. During the examination of unaccompanied and undocumented minors, this procedure may lead to binary decisions around age thresholds of legal interest, namely the ages of 14, 16 and 18 years. This study aimed to test the performance of artificial intelligence to classify individuals below and above the legal age thresholds of 14, 16 and 18 years using third molar development. The sample consisted of 11,640 panoramic radiographs (9680 used for training and 1960 used for validation) of males (n = 5400) and females (n = 6240) between 6 and 22.9 years. Computer-based image annotation was performed with V7 software (V7labs, London, UK). The region of interest was the mandibular left third molar (T38) outlined with a semi-automated contour. DenseNet121 was the Convolutional Neural Network (CNN) of choice and was used with Transfer Learning. After Receiver-operating characteristic curves, the area under the curve (AUC) was 0.87 and 0.86 to classify males and females below and above the age of 14, respectively. For the age threshold of 16, the AUC values were 0.88 (males) and 0.83 (females), while for the age of 18, AUC were 0.94 (males) and 0.83 (females). Specificity rates were always between 0.80 and 0.92. Artificial intelligence was able to classify male and females below and above the legal age thresholds of 14, 16 and 18 years with high accuracy.

Developmental process of the modern house shrew's molars: implications for the evolution of the tribosphenic molar in Mesozoic mammals.

Phylogenetically, the tribosphenic molars-prototypes of multi-cusped cheek teeth in marsupial and placental mammals-are derived from the single-cusped conical teeth of reptiles through the addition of cusps. Ontogenetically, mammalian molars are formed through the interface between the dental epithelium and mesenchyme (future enamel-dentin junction), becoming geometrically complex by adding epithelial signaling centers, called enamel knots, which determine future cusp positions. To reevaluate cusp homologies in Mesozoic mammals from an ontogenetic perspective, this study tracked molar development in a living placental mammal species, the house shrew (Suncus murinus), whose molars are morphologically the least derived from tribosphenic prototypes. The development of shrew molars proceeded as if it replayed the evolutionary process of tribosphenic molars. The first formed enamel knots gave rise to the evolutionarily oldest cusps-upper paracone and lower protoconid. The order of formation of other enamel knots and their location in development seemed to trace the order of cusp appearance in evolution. The parallel relationship between ontogeny and phylogeny of mammalian molars, if any, suggests that a change in the timing between developmental events rather than a change in the morphogenetic mechanism itself, should have been a major causal factor for the evolutionary transformation of tooth morphology.

Estimation of Mandibular Third Molar Development Using the Correlation in Dental Developmental Stages

This study aims to confirm the average chronologic age according to the developmental stages of the mandibular canine (L3), first and second premolars (L4, L5), and second and third molars (L7, L8) in children and adolescents, and to confirm the developmental stage of L3, L4, L5, and L7, which can estimate the development of L8. A total of 1,956 digital panoramic radiographs of healthy individuals aged between 6 and 15 years who visited Seoul National University Dental Hospital from January 2019 to December 2020 were selected. The developmental stages of L3, L4, L5, L7, and L8 on both sides were evaluated using the dental maturity scoring system proposed by Demirjian and Goldstein. The average age at which the follicle of L8 was first observed was around 9.34 ± 1.35 years and varied from 6 to 12 years. The possibility of agenesis of L8 was high when no traces of L8 were observed after the following stages: L3, L4, and L5 at the developmental stage F and L7 at the developmental stage E; the age was about 10 years. In estimating the development of L8, when only one tooth was considered, estimation accuracy with L5 was the highest, and there was no significant difference when all four teeth were included. This study showed the age distribution according to the developmental stages of L3, L4, L5, L7, and L8 in children and adolescents and confirmed the developmental stages of L3, L4, L5, and L7, which can be used to estimate the development of L8.

Developmental roles of glomerular epithelial protein-1 in mice molar morphogenesis.

Glomerular epithelial protein-1 (Glepp1), a R3 subtype family of receptor-type protein tyrosine phosphatases, plays important role in the activation of Src family kinases and regulates cellular processes such as cell proliferation, differentiation, and apoptosis. In this study, we firstly examined the functional evaluation of Glepp1 in tooth development and morphogenesis. The precise expression level and developmental function of Glepp1 were examined by RT-qPCR, in situ hybridization, and loss and gain of functional study using a range of in vitro organ cultivation methods. Expression of Glepp1 was detected in the developing tooth germs in cap and bell stage of tooth development. Knocking down Glepp1 at E13 for 2days showed the altered expression levels of tooth development-related signaling molecules, including Bmps, Dspp, Fgf4, Lef1, and Shh. Moreover, transient knock down of Glepp1 revealed alterations in cellular physiology, examined by the localization patterns of Ki67 and E-cadherin. Similarly, knocking down of Glepp1 showed disrupted enamel rod and interrod formation in 3-week renal transplanted teeth. In addition, due to attrition of odontoblastic layers, the expression signals of Dspp and the localization of NESTIN were almost not detected after knock down of Glepp1; however, their expressions were increased after Glepp1 overexpression. Thus, our results suggested that Glepp1 plays modulating roles during odontogenesis by regulating the expression levels of signaling molecules and cellular events to achieve the proper structural formation of hard tissue matrices in mice molar development.

Applying artificial intelligence to determination of legal age of majority from radiographic data

Forensic odontologists use biological patterns to estimate chronological age for the judicial system. The age of majority is a legally significant period with a limited set of reliable oral landmarks. Currently, experts rely on the questionable development of third molars to assess whether litigants can be prosecuted as legal adults. Identification of new and novel patterns may illuminate features more dependably indicative of chronological age, which have, until now, remained unseen. Unfortunately, biased perceptions and limited cognitive capacity compromise the ability of researchers to notice new patterns. The present study demonstrates how artificial intelligence can break through identification barriers and generate new estimation modalities. A convolutional neural network was trained with 4003 panoramic-radiographs to sort subjects into 'under-18' and 'over-18' age categories. The resultant architecture identified legal adults with a high predictive accuracy equally balanced between precision, specificity and recall. Moving forward, AI-based methods could improve courtroom efficiency, stand as automated assessment methods and contribute to our understanding of biological ageing.

Wolf-Hirschhorn syndrome candidate 1 (Whsc1) methyltransferase signals via a Pitx2-miR-23/24 axis to effect tooth development

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, hypodontia, and taurodontism. WHS candidate 1 (WHSC1) gene is a H3K36-specific methyltransferase that is deleted in every reported case of WHS. Mutation in this gene also results in tooth anomalies in patients. However, the correlation between genetic abnormalities and the tooth anomalies has remained controversial. In our study, we aimed to clarify the role of WHSC1 in tooth development. We profiled the Whsc1 expression pattern during mouse incisor and molar development by immunofluorescence staining and found Whsc1 expression is reduced as tooth development proceeds. Using real-time quantitative reverse transcription PCR, Western blot, chromatin immunoprecipitation, and luciferase assays, we determined that Whsc1 and Pitx2, the initial transcription factor involved in tooth development, positively and reciprocally regulate each other through their gene promoters. miRNAs are known to regulate gene expression posttranscriptionally during development. We previously reported miR-23a/b and miR-24-1/2 were highly expressed in the mature tooth germ. Interestingly, we demonstrate here that these two miRs directly target Whsc1 and repress its expression. Additionally, this miR cluster is also negatively regulated by Pitx2. We show the expression of these two miRs and Whsc1 are inversely correlated during mouse mandibular development. Taken together, our results provide new insights into the potential role of Whsc1 in regulating tooth development and a possible molecular mechanism underlying the dental defects in WHS.