Reliability of Third Molar Development for Age Estimation in a Texas Hispanic Population: A Comparison Study*

Abstract: Evaluating third molars from 950 Hispanic individuals aged 12–22 years using Demirjian’s schematic for crown and root formation found that Hispanic third molar development was 8–18 months faster than American Caucasians as reported by Mincer, Harris and Berryman in 1993. This represents a statistically significant increase. Earlier development was more apparent in the later stages F through H. Hispanic males reach developmental stages faster than Hispanic females and maxillary third molars reach developmental stages faster than mandibular third molars in both sexes. The earliest age observed for stages B–H (e.g., Stage H first observed at age 13.92 years in females) and the oldest age observed for Stages B–G were developed to facilitate age prediction of unknown individuals. Prediction tables for minimum and maximum age for an observed stage (e.g., if a female maxillary third molar is stage F it means she is older than 13 years) for each sex‐jaw group were calculated.     

Dental Age Estimation: Pattern Recognition of Root Canal Widths of Mandibular Molars. A Novel Mandibular Maturity Marker at the 18‐Year Threshold

The final stage of third molar development is used to assign a subject to above the 18‐year threshold. Some subjects exhibiting this final stage are less than 18 years. Radiographs from 1000 females and 1000 males age 16.00–25.99 years were examined. Each half‐year age band comprised 50 females and 50 males. Three categories of root canal widths (RCW) of the LL6, LL7, and LL8 [FDI 36, 37, and 38] were defined. Reproducibility was achieved by re‐assessing the same subjects 12 months apart. For females, the minimum value for RCW‐A was 16.33 years, RCW‐B 17.23 years, and RCW‐C 18.45 years. For males, the minimum values were RCW‐A 17.16 years, RCW‐B 18.29 years, and RCW‐C 18.16 years. The presence of RCW‐C in a female, and the presence of RCW‐B or RCW‐C in a male is compelling evidence that the subject is above the 18‐year threshold.     

Third molar development in a London population of White British and Black British or other Black ethnicity

Population differences in dental development between Black and White ethnic groups have been debated but not previously studied in the UK. Using inappropriate data for dental age estimation (DAE) could lead to erroneous results and injustice. Data were collected from dental panoramic radiographs of 5590 subjects aged 6–24 years in a teaching hospital archive. Demirjian stages were determined for left-sided teeth and third molars and data collected regarding hypodontia and third molar agenesis. Third molar development in self-assigned Black British, including other self-assigned Black ethnicity, was compared with that of self-assigned White British subjects. Data were compared for males and females in the two ethnic groups using T-tests for Demirjian Stages A–G of third molar development and Mann-Whitney tests for Stage H once a cut-off age at the maximum age for Stage G had been imposed. Third molar development occurred earlier in subjects of Black ancestry compared to those of White ancestry. While both ethnic groups showed large age ranges for every third molar stage, in female subjects these generally occurred at least 1.5 years earlier, and in males at least one year earlier. Hypodontia and third molar agenesis were more prevalent in White British, but the ethnic difference in third molar development persisted in subjects with complete dentitions. This is a large study that confirms ethnic differences in a London population, emphasises the difficulties of establishing the 18-year-old threshold using DAE, and confirms the risk of overestimating the age of individuals of Black ethnicity using White ethnic reference data.     

The Reliability of Chronological Age Determination by Means of Mandibular Third Molar Development in Subjects in Croatia*

Abstract: The aim of this study was to determine the development of the mandibular third molar and its relation to chronological age. The evaluated material consisted of 979 orthopantomograms of patients of Croatian Caucasian origin aged between 5.7 and 14.6 years. Third molar developmental stages were evaluated according to the stages proposed by Nolla. The frequencies of different stages of mineralization and the mean value of the mineralization of the mandibular third molars with regard to age, gender, and size of the mandible were determined and the coefficient of correlation determined between the age of the subject and the stage of development of the mandibular molars. Statistically significant correlation was determined between mineralization of the mandibular third molar and chronological age of the subjects (boys, mandibular left third molar r = 0.779, right third molar r = 0.793; girls, mandibular left third molar r = 0.746, right third molar r = 0.725). It can be concluded that the accuracy of age estimation based on Nolla’s method is applicable for Croatian children.     

Accuracy of Identifying Juvenile/Adult Status from Third Molar Development using Prediction Probabilities Derived from Logistic Regression Analysis

The use of third molars in predicting juvenile/adult status (</≥ 18 years) has important legal ramifications. Third molar development was assessed using Köhler's grading on 268 orthopantomograms of Indian subjects. Logistic regression analysis was applied to determine allocation accuracy of juvenile/adult status and the level of probability that is “reliable” in predicting juvenile/adult status. Allocation accuracies ranged between 75.8% and 78.2% for the sexes combined, with minimal male‐female differences. Adults were categorized more accurately than juveniles, suggesting that Köhler's grading puts Indian juveniles at greater risk of unwarranted punishment. In both sexes, juvenile/adult status was “reliably” predicted when the probability was >80% using individual third molars (excepting the lower right third molar in males); combining upper and lower third molars on the left/right sides, “reliable” predictions were possible when the probability was >80% and >90% for females and males, respectively. Overall, “reliable” juvenile/adult status prediction was achieved in c. 36% of subjects.     

Third Molar Development: Evaluation of Nine Tooth Development Registration Techniques for Age Estimations

Multiple third molar development registration techniques exist. Therefore the aim of this study was to detect which third molar development registration technique was most promising to use as a tool for subadult age estimation. On a collection of 1199 panoramic radiographs the development of all present third molars was registered following nine different registration techniques [Gleiser, Hunt (GH); Haavikko (HV); Demirjian (DM); Raungpaka (RA); Gustafson, Koch (GK); Harris, Nortje (HN); Kullman (KU); Moorrees (MO); Cameriere (CA)]. Regression models with age as response and the third molar registration as predictor were developed for each registration technique separately. The MO technique disclosed highest R² (F 51%, M 45%) and lowest root mean squared error (F 3.42 years; M 3.67 years) values, but differences with other techniques were small in magnitude. The amount of stages utilized in the explored staging techniques slightly influenced the age predictions.     

Estimation of legal age using calcification stages of third molars in living individuals

The increased number of adolescents and young adults with unknown or inaccurately given date of birth is a current issue in justice and legal medicine. The objective of this study was to determine the extent to which third molar calcification stages assessed on panoramic X-rays could be useful as additional criteria for forensic age estimation in living individuals, focusing on the legally important ages 17 and 18.In a retrospective multi-center study, the developmental stage of each individual's third molar was analyzed using Demirjian's scale in 2360 cases. Additionally, sex, age and ancestry were assessed.Individuals with the lowest calcification stage of all present molars in stage H were ≥ 18 years with a likelihood of ≥ 99.05% in the female (n = 388), and ≥ 99.24% in the male (n = 482) population.The lowest calcification stage of all present third molars proved to be useful as an additional reliable criterion for the determination of an age ≥ 18 years.     

Age Estimation in Indians Using Demirjian’s 8‐teeth Method

Abstract: Demirjian’s grading of tooth calcification is widely used to assess age of individuals with developing dentitions. However, its application on numerous populations has resulted in wide variations in age estimates and consequent suggestions for the method’s adaptation to the local sample. Conventionally, Demirjian’s method utilized seven mandibular teeth on the left side. A recent modification incorporated the third molar with a view to apply the method on a wider age‐group. Moreover, the revised method developed regression formulas for assessing age. This paper tested the 8‐teeth method using 547 Indians (348 females, 199 males) aged 7–25 years. Demirjian’s formulas resulted in inferior age prediction in Indians (9.2% misclassification at 99% confidence interval vs. 0% misclassification in the original study); therefore, India‐specific regression formulas were developed, which gave better age estimates (mean absolute error, MAE = 0.87 years) than the original formulas (MAE = 1.29 years). This suggests that Demirjian’s 8‐teeth method also needs adaptation prior to use in diverse populations.     

Dental Age Estimation: A Test of the Reliability of Correctly Identifying a Subject Over 18 Years of Age Using the Gold Standard of Chronological Age as the Comparator

This study was designed to test the reliability of using the third molars to demarcate between child and adult status. A total of 2000 dental panoramic tomographs were used for assessment of the calculated age using the 8‐stage system of tooth development and applied to all four third molars. The LL8 was also assessed using this 8‐stage system. For each tooth development stage, the Normal distribution and percentile summary data were estimated. The calculated dental age compared with the chronological age was statistically significantly different (p < 0.001) for both females and males giving underestimates of the true age. Comparison of single tooth dental age and chronological age was only slightly different. The most important finding is that the assignment to above or below the 18‐year threshold, in the age range 17 years to 19 years, could be wrong on up to 50% of occasions.     

Forensic Age Estimation Using Thin‐Slice Multidetector CT of the Clavicular Epiphyses Among Adolescent Western Chinese

Reaching the age of 18 years is the most significant step for criminal proceedings in China. In this study, a population of 752 individuals was recruited to clarify how strong the chronological age relates to clavicular ossification status revealed by CT scans with 1 mm slice thickness in the West China Han population. Finally, the epiphysis was observed to commence fusion in females at 16.28 years and 16.74 years in males and be fully ossified by 25.97 years in females and 25.81 years in males. These findings suggested that ossification of medial clavicular epiphyseal cartilage can be used in age estimation for West China Han population with the age threshold of 18 years. By comparison with previous German studies, our results suggested that the pace of ossification of medial clavicular epiphyseal cartilage may be potentially affected by socioeconomic status.     

The Reliability of the Greulich and Pyle Atlas When Applied to a Modern Scottish Population

This study examines the reliability of age estimation utilizing the Greulich and Pyle atlas in relation to a modern Scottish population. A total of 406 left‐hand/wrist radiographs (157 females and 249 males) were age‐assessed using the Greulich and Pyle atlas. Analysis showed that there was a strong correlation between chronological age and estimated age (females R² = 0.939, males R² = 0.940). When age groups were broken down into year cohorts, the atlas over‐aged females from birth until 13 years of age. The pattern for males showed that the atlas under‐estimated age until 13 years of age after which point it consistently over‐aged boys between 13 and 17 years of age. This study showed that the Greulich and Pyle atlas can be applied to a modern population but would recommend that any analysis takes into account the potential for over‐ and under‐aging shown in this study.     

The accuracy and precision of third molar development as an indicator of chronological age in Hispanics

The accuracy and precision of chronological age estimation based on the stages of third molar tooth development was studied in a sample of 679 radiographs from individuals of Hispanic origin. The age range was 14.0 to 25.0 years. Eight raters from the University of Texas Health Science Center at Houston Dental Branch evaluated the radiographs according to Demirjian's schematic definitions of crown and root formation. The objective of this study was to evaluate the chronology of third molar development in Hispanics following the protocol of a previous study. Within the Hispanic population, the rate of male third molar development is greater than that of female third molar development for ten stages of crown-root formation. Also within this Hispanic population sample, the rate of maxillary third molar development is ahead of mandibular third molar development. The mean absolute difference between chronological age and estimated age was +/-3.0 years in females and +/- 2.6 years in males.     

Mineralization of mandibular third molars can estimate chronological age--Brazilian indices

Forensic age estimation is an important element of anthropological research, as it produces one of the primary sources of data that researchers use to establish the identity of a person living or the identity of unknown bodily remains. The aim of this study was to determine if the chronology of third molar mineralization could be an accurate indicator of estimated age in a sample Brazilian population. If so, mineralization could determine the probability of an individual being 18 years or older. The study evaluated 407 panoramic radiographs of males and females from the past 5 years in order to assess the mineralization status of the mandibular third molars. The evaluation was carried out using an adaptation of Demirjian's system. The results indicated a strong correlation between chronological age and the mineralization of the mandibular third molars. The results indicated that modern Brazilian generation tends to demonstrate an earlier mandibular third molar mineralization than older Brazilian generation and people of other nationalities. Males reached developmental stages slightly earlier than females, but statistically significant differences between the sex were not found. The probability that an individual with third molar mineralization stage H had reached an age of 18 years or older was 96.8-98.6% for males and females, respectively.     

Morphometric analysis of third molar root development by an experimental method using digital orthopantomographs

Abstract:  The aim of the study was to conduct a morphometric analysis of the root development of the third molar, with the purpose of overcoming the limits of an exclusively morphological analysis. The study was divided in two phases. The first one was the verification of the existence of a constant crown-root (C/R) ratio on a sample of 100 third molars, characterized by a complete root development. The value obtained was used in the second phase to predict the final root's length, knowing the crown height. So we have calculated, on a sample of 322 third molars with developing roots, the final ratios between incomplete roots and complete roots. Statistical analysis was then made with 90%, 95%, and 99% confidence intervals. The results showed a significant difference according to the age of the subject and the limit values, lower and upper, for subjects aged 16 and 17 years versus those aged 18 and 19. For each analysis, the width of the class of tolerance and other statistical indicators were calculated. The results we obtained support the advantage of a morphometric study as opposed to an exclusively morphological study, but all the techniques used to determine the age of a living subject can provide only indications of the biological age, but no certainties as regards chronological age.     

Age estimation from root development of mandibular third molars in comparison with skeletal age of wrist joint

Identification of the living person and the dead is of paramount importance for variety of reasons in forensic practice routinely. Age estimation is one of the prime factors employed to establish identity. Estimating age from teeth is generally reliable as they are naturally preserved long after all the tissues and even bones have disintegrated. A study was done to determine the age by root developmental changes, using the intraoral periapical radiographs of the mandibular third molars, adopting the Leif Kullman et al method. Three hundred forty-six girls and 389 boys of the age range 15-25 years, among the South Indian population of young adults from various schools and colleges in the vicinity of Dakshina Kannada and Udupi Districts and also among the patients visiting the outpatient department of Oral Medicine and Radiology, College of Dental Surgery, Manipal, were considered for this study. The subjects were roentgenographically examined to determine the age from the 7 stages of root development of the left mandibular third molar. Depending on the exact stage of root development as seen in the radiograph, the chronologic age was determined. This method sheds a new light on determining the ages of 15, 16, and 18 years, which has an immense medicolegal bearing.     

Age estimation and the developing third molar tooth: an analysis of an Australian population using computed tomography

The third molar tooth is one of the few anatomical sites available for age estimation of unknown age individuals in the late adolescent years. Computed tomography (CT) images were assessed in an Australian population aged from 15 to 25 years for development trends, particularly concerning age estimation at the child/adult transition point of 18 years. The CT images were also compared to conventional radiographs to assess the developmental scoring agreement between the two and it was found that agreement of Demirjian scores between the two imaging modalities was excellent. The relatively wide age ranges (mean ± 2SD) indicate that the third molar is not a precise tool for age estimation (age ranges of 3-8 years) but is, however, a useful tool for discriminating the adult/child transition age of 18 years. In the current study 100% of females and 96% of males with completed roots were over 18 years of age.     

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.     

Cone‐beam Computed Tomography for Analyzing Variations in Inferior Alveolar Canal Location in Adults in Relation to Age and Sex*

Abstract: Previous studies have indicated that the relative position of the inferior alveolar canal and its mental and mandibular foramina in adults vary with age and show sexual dimorphism. Conceivably, these purported differences could be of forensic value for determining identity of human remains. This study was designed to determine the influence of age and sex on the relative position of inferior alveolar canal and its foramina in cone‐beam computed tomography (CBCT) studies of adults. Existing CBCT studies of the maxillofacial region from dentate adult patients selected at random and ranging in age from 18 to 80 years (110 women and 55 men) were acquired, and the location of the inferior alveolar canal was assessed at three points: the mandibular foramen in axial view, the inferior alveolar canal in coronal view, and the mental foramen in coronal view. Measurements were also expressed for the mental foramen as the percentile position from the nearest superior bony crest to the inferior border; corresponding position of the mandibular foramen from the anterior to the posterior border of the mandibular ramus; and for the inferior alveolar canal at the level of first permanent molar from the nearest buccal bony surface to the lingual surface and from the superior alveolar crest to the inferior border. Regression analyses were performed on the variables with regard to the effects of age and sex. Most analyses resulted in no statistical significance (p < 0.05). A few of the sex‐specific traits demonstrated near‐statistically significant effects; however, these characterizations generally resulted in a 1% or less change per age decade. Overall, the results demonstrated that the relative location of the inferior alveolar canal and associated foramina in adults remain fairly constant without regard to age and sex.     

Third molar development according to chronological age in populations from Spanish and Magrebian origin

Spain is frequently the entrance country into the European Union for undocumented immigrants, especially those from the Magreb (Northern Africa). Forensic age estimates for these persons are difficult because systematic studies of dental maturity are lacking. Three different populations were analyzed to determine the pattern of development of third molars as a tool for age estimation in people of different ethnic and geographic origin. Orthopantomograms from two different populations of Spanish origin (Galicia in northwestern continental Spain, and Ceuta, a Spanish province in Northern Africa) were compared to radiographs of molars from a Magrebian population (Northern Africa) resident in Ceuta. Orthopantomograms were obtained from a private dental clinic (n=344) in Galicia and from the Public Oral Health Services (n=228) in Ceuta. We looked for differences in third molar mineralization (determined with the Demirjian scale) that might serve as age indicators (older versus younger than 18 years). Differences in maturation patterns were found between sexes and populations of origin. Mineralization of tooth 38 was more advanced in males than females among subjects 18 years of age and older in all three populations. Moreover, mineralization of tooth 38 in subjects aged 18 years and older was significantly slower in the Spanish-Galicia population than in the Magrebian-Ceuta population. We found no significant differences between Magrebian and Spanish individuals from Ceuta. We conclude that differences in tooth 38 mineralization may be related more with socio-geographical than ethnic origin (ancestry), and thus constitute evidence of the relevance of socio-geographic rather than genetic factors in third molar development. We used ROC analysis to determine the accuracy of the examiner's ability to correctly estimate age as younger or older than 18 years. The results suggest that Demirjian stage for tooth 38 can be considered a good indicator of age in all three populations.