Validación de un modelo cefalométrico de predicción para el brote de los terceros molares / Validation of a cephalometric prediction model for third molar eruption

Introducción: La intervención temprana en el brote anormal de los terceros molares podría reducir la proporción de pacientes con las molestias asociadas y la aparición de alteraciones producto a la retención dentaria. Objetivo: Validar el modelo cefalométrico predictivo para el brote de los terceros molares desarrollado González Espangler. Métodos: Se realizó un estudio longitudinal, descriptivo, de corte transversal, en adolescentes del Instituto Preuniversitario "Rafael María de Mendive" de Santiago de Cuba durante el periodo comprendido entre enero del 2017 y marzo del 2020. Fueron empleadas dos muestras aleatorias de 21 estudiantes de 15-18 años y 29 profesionales de las ciencias de la salud. Se estudiaron variables como el sexo, color de la piel, localización, etapa de formación, espacio óseo posterior, angulación, diámetro mesiodistal, factores predictivos y tipo de brote de los terceros molares. Resultados: Predominó el tipo de brote anormal: 19,0 por ciento para la localización 1.8; 17,9 por ciento para la 2.8; 21,4 por ciento en la 3.8 y 20,2 por ciento en la posición 4.8. No existieron diferencias significativas entre las medidas promedios del espacio óseo posterior, angulación y diámetro mesiodistal con el estudio de referencia. La validación de modelo por criterio de expertos obtuvo una calificación global de concordancia entre ellos del 100 por ciento. Conclusiones: El modelo cefalométrico predictivo validado es viable en el proceso de predicción del brote de los terceros molares en la población(AU)

Introduction: Early intervention in the abnormal eruption of third molars could reduce the number of patients with associated discomfort and the appearance of alterations caused by dental retention. Objective: Validate the cephalometric prediction model for third molar eruption developed by González Espangler. Methods: A cross-sectional longitudinal descriptive study was conducted of adolescents from Rafael María de Mendive Senior High School in Santiago de Cuba from January 2017 to March 2020. The two random samples examined consisted of 21 students aged 15-18 years and 29 health sciences professionals. The variables considered were sex, skin color, location, training stage, posterior bony space, angulation, mesiodistal diameter, predictive factors and type of third molar eruption. Results: Abnormal eruption prevailed: 19.0 percent in location 1.8; 17.9 percent in 2.8; 21.4 percent in 3.8 and 20.2 percent in 4.8. Significant differences were not observed between average values for posterior bony space, angulation and mesiodistal diameter, and the study reference. Validation of the model by expert criteria obtained a global agreement score of 100 percent. Conclusions: The cephalometric prediction model validated in the study is viable for the prediction of third molar eruptions in the population(AU)

Comparison of the third molar maturity index (I3M) between left and right lower third molars to assess the age of majority: a multi-ethnic study sample.

The diagnostic accuracy of the I3M to assess the legal age of 18 years has already been tested in several specific-population samples. The left lower third molar has been extensively used for discriminating between minors and adults. This research aimed to compare the usefulness of lower third molar maturity indexes, from both left and right side (I3ML and I3MR), in samples originating from four distinct continents in order to examine possible differences in their accuracy values. For this purpose, a sample of 10,181 orthopantomograms (OPGs), from Europe, Africa, Asia and America, was analysed and previously scored in other studies. The samples included healthy subjects with no systemic disorders with both third molars and clear depicted root apices. Wilcoxon Signed Rank test for left and right asymmetry did not show any significant differences. Data about sensitivity, specificity, predictive values, likelihood ratio and accuracy were pooled together and showed similar results for I3ML and I3MR, respectively. In addition, all these quantities were high when only the I3MR was considered to discriminate between adults and minors. The present referable database was the first to pool third molar measurements using panoramic radiographs of subjects coming from different continents. The results highlighted that both I3ML and I3MR are reliable indicators for assessing the legal age of 18 years old in those jurisdictions where this legal threshold has been set as the age of majority.

Molecular and morphological findings in a sample of oral surgery patients: What can we learn for multivariate concepts for age estimation?

It has already been proposed that a combined use of different molecular and morphological markers of aging in multivariate models may result in a greater accuracy of age estimation. However, such an approach can be complex and expensive, and not every combination may be useful. The significance and usefulness of combined analyses of D-aspartic acid in dentine, pentosidine in dentine, DNA methylation in buccal swabs at five genomic regions (PDE4C, RPA2, ELOVL2, DDO, and EDARADD), and third molar mineralization were tested by investigating a sample of 90 oral surgery patients. Machine learning models for age estimation were trained and evaluated, and the contribution of each parameter to multivariate models was tested by assessment of the predictor importance. For models based on D-aspartic acid, pentosidine, and the combination of both, mean absolute errors (MAEs) of 2.93, 3.41, and 2.68 years were calculated, respectively. The additional inclusion of the five DNAm markers did not improve the results. The sole DNAm-based model revealed a MAE of 4.14 years. In individuals under 28 years of age, the combination of the DNAm markers with the third molar mineralization stages reduced the MAE from 3.85 to 2.81 years. Our findings confirm that the combination of parameters in multivariate models may be very useful for age estimation. However, the inclusion of many parameters does not necessarily lead to better results. It is a task for future research to identify the best selection of parameters for the different requirements in forensic practice.

Study of the ethnicity's influence on the third molar maturity index (I3M) for estimating age of majority in living juveniles and young adults.

Estimation of age of majority has important applications in the forensic daily practice because of the increasing demand for age estimates of unaccompanied minors. Diagnostic accuracy of I3M to assess legal adult age of 18 years has been already tested in several specific population samples. The aim of this work was to compare the available data about sensitivity and specificity of the third molar maturity index (I3M) from five different regional groups' radiographic samples to study possible ethnical difference. For this purpose, a sample of 6157 orthopantomograms (OPGs), coming from 15 countries, was analysed. Data about sensitivity and specificity were pooled using a bivariate modelling approach. The one-way MANOVA analysis was applied to assess the likelihood that sensitivity and specificity of the five regional groups are sampled from the same population. The result of the one-way MANOVA showed that both sensitivity and specificity did not depend from the regional groups. The obtained sensitivity was 84% (95% CI: 82% and 85%), and its specificity was 94% (95% CI: 93% and 95%). Based on these results, the I3M was a useful statistical tool to identify whether a subject has reached the legal age of 18 years old, regardless of his or her ethnicity.

Age estimation in the living: A scoping review of population data for skeletal and dental methods.

Age estimation of living individuals has become a crucial part of the forensic practice, especially due to the global increase in cross-border migration. The low rate of birth registration in many countries, hence of identification documents of migrants, especially in Africa and Asia, highlights the importance of reliable methods for age estimation of living individuals. Despite the fact that a number of skeletal and dental methods for age estimation have been developed, their main limitation is that they are based on specific reference samples and there is still no consensus among researchers on whether these methods can be applied to all populations. Though this issue remains still unsolved, population information at a glance could be useful for forensic practitioners dealing with such issues. This study aims at presenting a scoping review and mapping of the current situation concerning population data for skeletal (hand-wrist and clavicle) and dental methods (teeth eruption and third molar formation) for age estimation in the living. Two hundred studies on the rate of skeletal maturation and four hundred thirty-nine on the rate of dental maturation were found, covering the period from 1952 and 2020 for a total of ninety-eight countries. For most of the western and central African countries there are currently no data on the rate of skeletal and dental maturation. The same applies to the countries of the Middle East, as well as the eastern European countries, especially as regard the skeletal development.

Validation of Roberts' method using root canal width patterns as a mandibular maturity marker in determining the 18-year threshold.

The South African Bill of Rights and the Children's Act define a 'child' as a person under the age of 18 years. The age of 18 years is therefore significant for legal purposes in South Africa. The third molar is an important indicator in determining the 18-year threshold. Human biological growth markers are accepted indicators of a subject attaining the age of 18 years. A recent study by Roberts et al. suggested that the relative width of the distal root canals (RCW) of the lower left permanent molars (Fédération Dentaire Internationale notation 36, 37 and 38) as visualised on dental panoramic radiographs can be used as such a growth marker. This study aimed to validate this human biological growth marker in both black and white populations living in South Africa according to Roberts' method. The findings of this validation study were in agreement with this method which showed that individuals with Demirjian stage H left molars and category RCW-C were indeed over the 18-year threshold. Important aspects regarding the rationality and application of Roberts' method are discussed. The authors conclude that this method should not be used in isolation but as an adjunct with other age estimation methods.

Comparison of different machine learning approaches to predict dental age using Demirjian's staging approach.

CONTEXT: Dental age, one of the indicators of biological age, is inferred by radiological methods. Two of the most commonly used methods are using Demirjian's radiographic stages of permanent teeth excluding the third molar (Demirjian's and Willems' method). The major drawbacks of these methods are that they are based on population-specific conversion tables and may tend to over- or underestimate dental age in other populations. Machine learning (ML) methods make it possible to create complex data schemas more simply while keeping the same annotation system. The objectives of this study are to compare (1) the capacity of ten machine learning algorithms to predict dental age in children using the seven left permanent mandibular teeth compared to reference methods and (2) the capacity of ten machine learning algorithms to predict dental age from childhood to young adulthood using the seven left permanent mandibular teeth and the four third molars. METHODS: Using a large radiological database of 3605 orthopantomograms (1734 females and 1871 males) of healthy French patients aged between 2 and 24 years, seven left permanent mandibular teeth and the 4 third molars were assessed using Demirjian's stages. Dental age estimation was then performed using Demirjian's reference method and various ML regression methods. Two analyses were performed: with the 7 left mandibular teeth without third molars for the under 16 age group and with the third molars for the entire study population. The different methods were compared using mean error, mean absolute error, root mean square error as metrics, and the Bland-Altman graph. RESULTS: All ML methods had a mean absolute error (MAE) under 0.811 years. With Demirjian's and Willems' methods, the MAE was 1.107 and 0.927 years, respectively. Except for the Bayesian ridge regression that gives poorer accuracy, there was no statistical difference between all ML tested. CONCLUSION: Compared to the two reference methods, all the ML methods based on the maturation stages defined by Demirjian were more accurate in estimating dental age. These results support the use of ML algorithms instead of using standard population tables.

A new model of classification of third molars development and its correlation with chronological age in a Brazilian subpopulation.

The present study correlated the mineralization of third molars to chronological age using a modified classification based on Demirjian's stages in a Brazilian subpopulation and compared with the original classification. A total of 1082 patients with age ranging from 6 to 26 years were included in the sample, with at least one third molar on panoramic radiographs. The third molars were classified according to the original Demirjian classification (8 stages) and a new model based on the Demirjian method, where the original stages were grouped into four stages: AB-enamel mineralization; CD-crown dentin mineralization; EFG-root formation; and H-complete development. Statistical analyses were performed by Kruskal-Wallis/Dunn tests (α = 0.05) and the multinomial logistic regression model. Data were analyzed according to percentiles for the probability of an individual being over 18 years old. The mean ages of the stages in both classifications did not present a significant difference between superior and inferior arches (p < 0.05). The differences in mean ages between all the stages of mineralization were statistically significant (p < 0.001) only for the 4-stage classification. Males attained root formation and complete formation earlier than females (p < 0.05) in the 4-stage classification. The modified classification system showed dependence between chronological age and mineralization stages of third molars, simplifying the age estimation process. At stage H, females present a 95.7% chance of being over 18, while for males, this probability is 89.6%. This modified classification system simplifies the dental age estimation process based on third molars and can be used as a reference for future studies.

Growth and development of the third permanent molar in Paranthropus robustus from Swartkrans, South Africa.

Third permanent molars (M3s) are the last tooth to form but have not been used to estimate age at dental maturation in early fossil hominins because direct histological evidence for the timing of their growth has been lacking. We investigated an isolated maxillary M3 (SK 835) from the 1.5 to 1.8-million-year-old (Mya) site of Swartkrans, South Africa, attributed to Paranthropus robustus. Tissue proportions of this specimen were assessed using 3D X-ray micro-tomography. Thin ground sections were used to image daily growth increments in enamel and dentine. Transmitted light microscopy and synchrotron X-ray fluorescence imaging revealed fluctuations in Ca concentration that coincide with daily growth increments. We used regional daily secretion rates and Sr marker-lines to reconstruct tooth growth along the enamel/dentine and then cementum/dentine boundaries. Cumulative growth curves for increasing enamel thickness and tooth height and age-of-attainment estimates for fractional stages of tooth formation differed from those in modern humans. These now provide additional means for assessing late maturation in early hominins. M3 formation took ≥ 7 years in SK 835 and completion of the roots would have occurred between 11 and 14 years of age. Estimated age at dental maturation in this fossil hominin compares well with what is known for living great apes.

Performance and comparison of the London Atlas technique and Cameriere's third molar maturity index (I3M) for allocating individuals below or above the threshold of 18 years.

Age estimation is an important procedure in the forensic practice, especially when it comes to the criminal imputability of juvenile offenders. This study aimed to compare two radiographic methods for dental age estimation in a population of subadults from Northeast Brazil considering their performance on allocating individuals below or above the age threshold of 18 years. A cross-sectional observational study was designed. The sample consisted of 1200 panoramic radiographs of Northeastern Brazilian females (n = 600) and males (n = 600) aged between 16 and 21 years. Dental age estimation was performed using the London Atas technique and Cameriere's third molar maturity index (I3M). Statistical tests were performed to assess the sensitivity, specificity and accuracy of the two methods on distinguishing individuals below or above the legal age threshold of 18 years. Considering the total sample, the London Atlas technique reached sensitivity of 92.3%, specificity of 56% and accuracy of 79.9%. I3M revealed sensitivity of 94.1%, specificity of 55.4% and accuracy of 79.8%. Specificity rates systematically decreased when the sample was progressively stratified based on age groups that narrowed close to 18 years. The methods performed very similar (0.878). The combination of methods did not improve the performance on dental age estimation. The London Atlas and the I3M methods similarly distinguished Brazilian individuals as minors or not. Their performance, however, was suboptimal because of the low rates of specificity that could negatively influence on Court decisions. In other words, the methods could wrongly classify minors into the age of legal majority (culminating in false positives). In practice, the misleading classification could restrict individual rights (in the civil scenario) or even support more severe penalties (in the criminal scenario).

Applicability of newly derived second and third molar maturity indices for indicating the legal age of 16 years in the Southern Chinese population.

In China, forensic age estimation in the living has become increasingly important in these few years. Due to increasing juvenile crimes, the age of 16 years has become the legal age threshold for determining whether the juvenile criminal law or adult criminal law applies to the citizen. This study aimed to assess new cut-off values of the third molar maturity index (I3M) and second molar maturity index (I2M) at the legal age threshold of 16 years in Southern Chinese population and then to compare the applicability of the cut-off values of I3M and I2M we set for discriminating whether a subject is ≥ 16 years. Orthopantomograms (OPGs) of 671 healthy Southern Chinese subjects (332 males and 339 females), aged between 10 and 20 years, were studied. Logistic regression analysis was performed with chronological age (below 16 years and over 16 years) as a dichotomous dependent variable and, I3M, I2M, and sex as predictive variables. The high p-value for sex (p = 0.861) reveals that this factor was not statistically significant in assessing the legal age of 16. The cut-off values of I3M < 0.38 and I2M < 0.03 were identified and used to distinguish between individuals who were or were not aged ≥ 16 years. Compared with a single predictor (I3M) alone, combining I3M and I2M can be more reliable for determining whether an individual is aged more than 16 years. We found that accuracy was 88.52% (95% confidence interval CI, 86.11-90.94%) and sensitivity and specificity were 77.96% (95% CI, 74.82-81.10%) and 97.28% (95% CI, 96.04-98.51%), respectively. The estimated Bayes post-test probability was 99.12% (95% CI, 98.41-99.83%). In conclusion, combining I3M and I2M may be useful in legal and forensic practices to determine the legal age of 16 years in Southern Chinese individuals.

Estimation of the age of majority through radiographic evaluation of the third molar maturation degree

BACKGROUND: Although the third molar is the tooth with the greatest anatomical and developmental variability, some authors consider it important to estimate whether a subject is of legal age or not. The Demirjian's technique is the most widely used tool to estimate dental age and was therefore used in our study to assess possible correlation between the age of majority and the maturational degree of the lower third molars, evaluated through radiographic images. MATERIAL AND METHODS: This observational transversal study was conducted on 180 panoramic radiographs from consecutive patients. The degree of maturation of the lower third molar was independently classified by two observers, according to the Demirjian 's maturational stage method. RESULTS: A total of 180 patients - 65 men (36.12%) and 115 women (63.88%) - were included (mean age 21.6 years; standard deviation 5.2). The age range of our subjects corresponded to maturational stages D to H in the Demirjian's classification. A logistic regression analysis showed that subjects classified into the highest maturational stage H had a significantly higher probability of being considered of legal age by both observers, as compared with subjects in the lowest stage D. Inter-observer agreement was very high. Gender predictive capacity was not observed. CONCLUSIONS: Our results showed that subjects with the lower third molars in the highest maturational stage could be estimated to be older than 18 years and therefore considered of legal age, a finding also reported by other authors. The Demirjian's tooth maturational stage method, applied to the lower third molars, can be reliably used to estimate whether an individual is of legal age (18 years or older). High concordance between different observers using this method can be expected

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Towards fully automated third molar development staging in panoramic radiographs.

Staging third molar development is commonly used for age assessment in sub-adults. Current staging techniques are, at most, semi-automated and rely on manual interactions prone to operator variability. The aim of this study was to fully automate the staging process by employing the full potential of deep learning, using convolutional neural networks (CNNs) in every step of the procedure. The dataset used to train the CNNs consisted of 400 panoramic radiographs (OPGs), with 20 OPGs per developmental stage per sex, staged in consensus between three observers. The concepts of transfer learning, using pre-trained CNNs, and data augmentation were used to mitigate the issues when dealing with a limited dataset. In this work, a three-step procedure was proposed and the results were validated using fivefold cross-validation. First, a CNN localized the geometrical center of the lower left third molar, around which a square region of interest (ROI) was extracted. Second, another CNN segmented the third molar within the ROI. Third, a final CNN used both the ROI and the segmentation to classify the third molar into its developmental stage. The geometrical center of the third molar was found with an average Euclidean distance of 63 pixels. Third molars were segmented with an average Dice score of 93%. Finally, the developmental stages were classified with an accuracy of 54%, a mean absolute error of 0.69 stages, and a linear weighted Cohen's kappa coefficient of 0.79. The entire automated workflow on average took 2.72 s to compute, which is substantially faster than manual staging starting from the OPG. Taking into account the limited dataset size, this pilot study shows that the proposed fully automated approach shows promising results compared with manual staging.

Estimation of Age Using Third Molar Development: A Radiological Cross-Sectional Study.

OBJECTIVES: This study was carried out to correlate chronological age of the patients with dental age using to Demirjian's method and to evaluate if orthopantamogram examination of third molar development correlates with age estimation. STUDY DESIGN: The study was designed as a radiological cross sectional study. Simple random sampling method was used to obtain study subjects. METHODS: Total of 231 patients between the age group of 10 to 25 years, visiting the Department of Oral Medicine and Radiology were selected. The digital orthopantomogram was obtained for these patients. RESULTS: Our data showed that, in the maxilla, the stages of tooth developments A to E were reached earlier in men than in women, whereas stages F to H were reached earlier in women than men. In mandible stages B, C, E to F were reached earlier in men than women, whereas stages A and D were reached earlier by the female counterparts. There was a statistically significant difference noted between right and left third molar teeth in all the stages of tooth development. CONCLUSIONS: Our study showed that between the sexes in maxilla, men reached stages A to E earlier than women, whereas for stages F to H, women reached the stage earlier than men. For mandible, all stages except stage D were reached earlier by male subjects than female subjects. Our study showed that the third molar development can be affected positively by the chronological age of the patient, being developed either in maxilla or mandible, right or left side.

An analysis of third molar mineralization in Brazilian patients with cleft lip and palate.

Purpose: This study investigated the third molar mineralization in patients with cleft lip and palate.Materials and methods: From a total of 253 digital panoramic radiographs from patients with cleft lip and palate within the age range of 7-21 years, 97 radiographs were selected (cleft group). A control group was formed from same sex individuals, without malformation and chronological age matched within 30 days. The analysis of third molar mineralization was carried out by three calibrated examiners using Demirjian's and Nolla's methods. McNemar and Wilcoxon test for paired samples were used for pairwise comparisons between the groups. The Likelihood Ratio test was used to check for an association between the type of cleft and tooth calcification.Results: In both methods, the mineralization means were smaller in the case group than in the control, with significant differences for all third molars (p < .05). The type of cleft affected dental mineralization. There was no significant difference when comparing the left or right sides, but maxillary molars showed earlier mineralization.Conclusions: A significant delay in third molar mineralization was observed in patients with cleft lip and palate according to Demirjian's and Nolla's methods.

Validation of the third molar maturity index cut-off value of <0.08 for indicating legal age of 18 years in Eastern Chinese region.

Having a reliable, inexpensive and simple method to estimate 18 years of age would be of help in the forensic field. This study aimed to test the accuracy of the third molar maturity index (I3M) in indicating the legal adult age of 18 years. This retrospective cross-sectional study analysed 450 digital panoramic images of Eastern Chinese children and young adults (226 females and 224 males) aged between 14 and 22 years. A cut-off value of I3M < 0.08 was tested in discriminating adults from minors for both sex. For females, the sensitivity of the test (Se) was 75.0%, with a 95% confidence interval (95%CI) of 67.5% to 82.5%. The specificity of the test (Sp) was 100%. The proportion accurately classified (Ac) individuals was 85.8% (95%CI, 81.3% to 90.4%). The Bayes post-test probability was 100% (93.6% to 100%). For males, Se, Sp and Ac were 91.9% (95%CI, 87.1% to 96.7%), 92.0%(95%CI, 86.7% to 97.3%) and 92% (95%CI, 88.4% to 95.5%), respectively. The Bayes post-test probabilities was 92% (95%CI, 88.4% to 95.5%). Males were ahead in the development of third molars comparing to females according to I3M. A stepwise logistic regression analysis showed that both I3M and sex contribute to the regression model to discriminate adults (≥18 years) from minors (<18 years), while a receiver operating curve (ROC) analysis indicated some better accuracy of I3M < 0.12 in females, without statistically significant difference when compared to I3M < 0.08. The results of this study show that the cut-off value of I3M < 0.08 may help to discriminate Eastern Chinese adults from minors. However, further study should evaluate the usefulness and possible variability of I3M cut-off value in a specific population before used for legal and forensic procedures.

Transition analysis applied to third molar development in a Danish population.

INTRODUCTION: Age assessment based on dental development is often requested in order to assess whether an individual is older or younger than 18 years of age. There are several statistical approaches to estimate age based upon third molar development. The aim of this study was to apply the principles of transition analysis (TA) to a Danish reference material and to evaluate whether it was indicated to include a model that allows for logistic non-linearity as opposed to applying a model only allowing for logistic linearity. For this we chose to use the generalized additive model (gam) and the generalized linear model (glm), respectively. MATERIAL AND METHOD: A cross-sectional sample comprising 1302 panoramic radiographs of Danish subjects in the chronological age range of 13-25 years was included. All present third molars had been scored according to the 10-stage method of Gleiser and Hunt. Each transition from one stage to the subsequent stage was analyzed according to the statistical approach of TA and fitted with both the generalized linear model (glm) and the generalized additive model (gam). In order to assess whether gam or glm was more parsimonious for each transition individually, the Akaikon information criterion (AIC) was applied. RESULTS: The results emphasized the importance of applying a statistical model that sufficiently captures the spread of the age estimate. The AIC values showed that some transitions were sufficiently described by glm whereas for others the gam curves fitted significantly better. CONCLUSION: We recommend that for an age assessment tool based on TA, both a fitting allowing for non-linearity and one allowing only for linearity should be included.

Cameriere's third molar maturity index in assessing age of majority: a study of a French sample.

Forensic age estimation is a challenging field in forensic sciences because of the increase of migratory flows. Medicolegal age assessment is a key point because it has many implications for authorities. Dental age estimation is an essential part of the global age assessment. The aim of this study was to evaluate and test the accuracy of Cameriere's cutoff values of the third molar maturity index (I3M) in assessing legal adult age of 18 years in a French population. The sample was constituted of 431 orthopantomograms performed between January 2014 and August 2017 on patients aged between 14 and 22 years. The reproducibility and repeatability of the method were high. Age distribution gradually decreases as I3M increases in both sexes. 0.08 seemed to be the best I3M cutoff. For females, the sensitivity and specificity of the test were 74.51% and 88.23%, respectively. The sensitivity and specificity for males were 92.19% and 88.35%, respectively. The accuracies were 80.74% for female, 90.57% for male. Estimated post-test probabilities were 0.879 for female and 0.899 for male. To conclude, the specific cutoff value of I3M ˂ 0.08 may be a useful additional tool in discriminating adults and minors in French population.

Root Pulp Visibility as a mandibular maturity marker at the 18-year threshold in the Maltese population.

INTRODUCTION: The determination of age of majority (the 18-year-old threshold) using the popular Demirjian tooth staging method is unreliable, so other maturity markers are required. This study examines whether the Root Pulp Visibility (RPV) of the mandibular third molar is a useful indicator of age. METHODS: One thousand six dental panoramic radiographs (DPTs) were examined and the left mandibular third molar assessed according to the RPV stages using the method of Olze et al. (Int J Legal Med 124:183-186, 2010) as modified by Lucas et al. (Forensic Sci Int 270:98-102, 2017). Six hundred sixty-two DPTs, 288 males and 374 females, satisfied the inclusion criteria. RESULTS: Individuals who had reached stages RPV-A and RPV-B were represented in a wide range of ages spanning the 18-year-old threshold. Individuals who had reached stages RPV-C and RPV-D were all above the 18-year-old threshold. It was not possible to analyse a large number of DPTs for various reasons. DISCUSSION: Individuals whose mandibular third molar exhibited stages RPV-C and RPV-D may be deemed to have reached the age of majority. These results are consistent with other published studies. Variation in the rate of development of the third molar limits the applicability of this method. CONCLUSIONS: RPV staging is an accurate method of determining the 18-year-old threshold. Substitute methods are required in a large number of cases.

Effect of Lower Third Molar Segmentations on Automated Tooth Development Staging using a Convolutional Neural Network.

Staging third molar development is commonly used for age estimation in subadults. Automated developmental stage allocation to the mandibular left third molar in panoramic radiographs has been examined in a pilot study. This method used an AlexNet Deep Convolutional Neural Network (CNN) approach to stage lower left third molars, which had been selected by manually drawn bounding boxes around them. This method (bounding box AlexNet = BA) still contained parts of surrounding structures which may have affected the automated stage allocation performance. We hypothesize that segmenting only the third molar could further improve the automated stage allocation performance. Therefore, the current study aimed to determine and validate the effect of lower third molar segmentations on automated tooth development staging. Retrospectively, 400 panoramic radiographs were collected, processed and segmented in three ways: bounding box (BB), rough (RS), and full (FS) tooth segmentation. A DenseNet201 CNN was used for automated stage allocation. Automated staging results were compared with reference stages - allocated by human observers - overall and per stage. FS rendered the best results with a stage allocation accuracy of 0.61, a mean absolute difference of 0.53 stages and a Cohen's linear κ of 0.84. Misallocated stages were mostly neighboring stages, and DenseNet201 rendered better results than AlexNet by increasing the percentage of correctly allocated stages by 3% (BA compared to BB). FS increased the percentage of correctly allocated stages by 7% compared to BB. In conclusion, full tooth segmentation and a DenseNet CNN optimize automated dental stage allocation for age estimation.