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

Postmortem computed tomography assessment of skeletal and dental age in Polish children, adolescents, and young adults

This paper presents a retrospective analysis of postmortem computed tomography (PMCT) scans of secondary ossification centers in the medial clavicular epiphysis, iliac crest apophysis, proximal humeral epiphysis, distal femoral epiphysis, proximal tibial epiphysis, and distal tibial epiphysis. At the same time, we analyzed PMCT scans of the maxillary and mandibular incisors, canines, premolars, and molars. We assessed 203 corpses, whose age ranged from 2 to 30 years, including 156 males and 47 females. The purpose of our study was to compare the processes of secondary ossification center fusion and permanent tooth maturation. Our research hypothesis was that certain stages of skeletal and dental maturation occur along consistent timelines that can be related to the chronological age. Secondary ossification center fusion was evaluated based on Kreitner and also McKern and Steward's classifications. The process of permanent tooth maturation was evaluated with Demirjian's method. Spearman's correlation coefficients (Rho) were positive in all analyses, which indicates that epiphyseal fusion progresses with age. The strongest relationship between the age and the stages of ossification was observed in the proximal tibial epiphysis (p < 0.001; Rho = 0.93) in females and in the medial clavicular epiphysis (p < 0.001; Rho = 0.77) in males. Studies show the importance of concomitant analysis of skeletal and dental maturation with a subsequent comparison of the results to achieve a greater precision in age estimation. A comparison of the results obtained in the study population of Polish children, adolescents, and young adults with the results of other studies in populations of similar ages showed a number of similarities in the time windows of dental and skeletal maturation. These similarities may help in age estimation.

Evaluation of Third Molar Maturity Index by Cone Beam Computed Tomography in Legal Age Estimation: A Preliminary Study

ABSTRACT

This retrospective study aimed to evaluate the accuracy and applicability of the third molar maturity index (I 3M ) for discriminating Turkish minors from adults, and its relationship with chronological age using cone beam computed tomography (CBCT). A total of 122 CBCT scans of Turkish individuals (55 boys and 67 girls) aged 13 to 23 years were evaluated using the I 3M cutoff value. Chronological age gradually decreased as the I 3M value increased. The overall accuracy was 95.9%. The sensitivity and specificity of this test were 93.5% and 97.4%, respectively. Positive predictive value was 95.6%. The intraclass correlation coefficient values of the I 3M for the intraobserver and interobserver agreements were 0.998 and 0.996, respectively. This study showed relatively higher reproducibility of measurements on CBCT scans than on panoramic radiographs in the literature. Cone beam computed tomography may be advantageous and preferred over panoramic radiographs in distinguishing the legal age threshold of 18 years according to Cameriere's method when a more extensive investigation is needed to support the solution of challenging and uncertain cases in forensic medicine.

Dental age estimation of Malaysian children: A comparison of two-dimensional verses three-dimensional imaging analyses of the developing root apices

Aim: The current study compared the effectiveness of the three-dimensional (3D) cone beam computed tomography (CBCT) method of age estimation developed by Asif et al. (2020) with two-dimensional Cameriere's method.Subjects and methods: CBCT images belonging to 129 Malaysian Chinese and Malay ethnic groups aged 7 to 14 years were investigated and analysed.Results: The results indicated a strong correlation between chronological age and the predictor variables for both Cameriere's (r = 0.984) and Asif's (r = 0.988) methods of age estimation. Fisher Z-test analysis indicated no statistically significant difference in the correlation values between the two methods. Mean absolute error (MAE) value of 0.613 was observed for Cameriere's and 0.290 was observed for Asif's method.Conclusion: The results indicated that the methods of age estimation from both Asif et al. (2020) and Cameriere et al. (2006) are applicable on Malaysian children. However, Asif et al.'s (2020) 3D CBCT method of age estimation resulted in greater accuracy and reliability in estimating chronological age.

Accuracy of different dental age estimation methods for determining the legal majority of 18 years in the Turkish population

OBJECTIVES

Radiographic evaluation of the third molar maturation is used to estimate dental age, especially in adolescence. This study aimed to assess the application of three age estimation methods (Cameriere's third molar maturity index (I_3M), Demirjian's maturation stages, and The London Atlas) to determine whether an individual is 18 years or older (adult) or younger than 18 years (minor).

MATERIALS AND METHODS

The dental age was estimated using the I_3M, Demirjian's maturation stages, and The London Atlas methods on panoramic radiograms of a total of 500 Turkish individuals aged 14-22 years. A logistic model was derived with an individual's adult or minor status as the dependent variable, and each method and sex as predictive variables. The adult status was determined using dental age estimation methods and the performance of these methods in differentiating adults from minors was evaluated. The three methods were compared case-wise for their accuracy in predicting adult status.

RESULTS

Logistic regression analysis showed that sex and each estimation method were statistically significant in discriminating adults and minors (p < 0.05). In the case-wise comparison for estimate adulthood, both Demirjian's stages and I_3M methods tended to perform better than the London Atlas method, with this trend reaching statistical significance (p < 0.05).

CONCLUSIONS

Cameriere's I_3M and Demirjian's development stages are useful methods for adult age assessment in the tested population.

CLINICAL RELEVANCE

In forensic medicine and legal practices, Cameriere's I_3M and Demirjian's maturation stage methods based on the development of the third molar teeth can be used to determine whether an individual is a minor or an adult.

Sensitivity and Specificity of Mandibular Third Molar Calcification at Chronological Age and Hand Wrist Maturation Stage to Discriminate Between Female and Male at Pubertal Growth Period

Background:

The mandibular third molar is the last tooth that is not completely developed by the time pubertal growth has been finished. Maturation of the mandibular third molar is one of the physiological maturation indicators that can be used to determine the stage of pubertal growth.

Objective:

The aim of the study was to determine the sensitivity and specificity of mandibular third molar calcification at chronological age and hand wrist maturation stage to discriminate between female and male at pubertal growth period.

Methods:

It is a retrospective study with a cross-sectional approach using panoramic and hand-wrist digital radiographs of 279 females and 144 males, age 8-17 years, with a total of 423 panoramic radiographs and 423 hand-wrist radiographs. Statistical analysis was performed using Excel Mega Stat. ANOVA to analyze the differences between mandibular third molar calcification at chronological age and hand-wrist maturation stage, and t-test was used to analyze the differences between females and males. Spearman rank correlation was used for the analysis of the correlation between mandibular third molar calcification with chronological age and hand-wrist maturation stage; sensitivity and specificity were used to discriminate the pubertal growth period between mandibular third molar calcification and hand-wrist maturation stage.

Results:

There were significant differences found in mandibular third molar crown maturation stage B and C, but no significant difference was observed between mandibular third molar stage A, D, E, F, G and H, between females and males. The highest percentage of mandibular third molar crown formation in females was observed at stage D (6.68%) at MP3u, and in males, it was observed at stage D (8.83%) at SMI-4. The highest percentage of root formation in females was stage E (8.24%) at the SMI-10 stage, and males stage F (4.86%) at MP3u. The correlation was observed between mandibular third molar calcification with hand-wrist, females 0.22 and males 0.43, and chronological age 0.60 for females and 0.69 for males. The highest sensitivity of mandibular third molar calcification of 97.0% was observed in female at SMI-4 of hand-wrist maturation with specificity of 100%, while in male, a sensitivity of 94.5% was observed at SMI-2 stage with a specificity of 99.99%.

Conclusion:

There were significant differences found in mandibular third molar calcification between females and males except for stage B and stage C; weak correlation was observed between mandibular third molar calcification and hand-wrist, and moderate correlation was observed with chronological age. The sensitivity and specificity in females and males indicate that mandibular third molar calcification is only useful for diagnosing the pre-pubertal growth phase.

Comparison of two established 2D staging techniques to their appliance in 3D cone beam computer-tomography for dental age estimation

For medicolegal purposes, orthodontic or orthognathic treatment various stomatological staging technique for age estimation with appliance of conventional radiographic images have been published. It remains uninvestigated if cone beam computer-tomography delivers comparable staging results to the conventional radiographic stages of third molar analysis. We conducted a retrospective cross-sectional study of 312 patients aged 13–21 years. Dental age estimation staging technique, introduced by Nolla and Demirjian, were applied on the left lower third molar imaged by conventional panoramic radiographs and cone beam computer-tomography. It was investigated if 2D and 3D imaging presented different staging results for dental age estimation. In 21% the Demirjian’s staging differed by a single stage between 2 and 3D images. The greatest congruence (87%) between 2 and 3D images was revealed for stage 7 (G). In contrary, stage 5 (E) presented the lowest level of congruence with 47.4%. The categorization of Nolla revealed divergences in staging for than two categorical variables in Nolla’s stages 3, 4, 5 and 6. In general, the analysis of the data displayed the divergence for Nolla’s stages 4–8. The staging results for 2D and 3D imaging in accordance to the rules of Nolla and Demirjian showed significant differences. Individuals of 18 years may present immature third molars, thus merely an immature third molar cannot reject legal majority. Nolla’s and Demirjian’s 2D and 3D imaging present significantly different staging results.

Accurate age classification using manual method and deep convolutional neural network based on orthopantomogram images

Age estimation is an important challenge in many fields, including immigrant identification, legal requirements, and clinical treatments. Deep learning techniques have been applied for age estimation recently but lacking performance comparison between manual and machine learning methods based on a large sample of dental orthopantomograms (OPGs). In total, we collected 10,257 orthopantomograms for the study. We derived logistic regression linear models for each legal age threshold (14, 16, and 18 years old) for manual method and developed the end-to-end convolutional neural network (CNN) which classified the dental age directly to compare with the manual method. Both methods are based on left mandibular eight permanent teeth or the third molar separately. Our results show that compared with the manual methods (92.5%, 91.3%, and 91.8% for age thresholds of 14, 16, and 18, respectively), the end-to-end CNN models perform better (95.9%, 95.4%, and 92.3% for age thresholds of 14, 16, and 18, respectively). This work proves that CNN models can surpass humans in age classification, and the features extracted by machines may be different from that defined by human.

2D vs. 3D Radiological Methods for Dental Age Determination around 18 Years: A Systematic Review

The age of a living human being can be determined by applying a number of different methods; the most diffused are skeletal and dental methods, both principally based on X-rays examinations. This systematic review assesses the current evidence regarding the accuracy and reliability of Cone Beam Computed Tomography (CBCT) vs. Orthopantomography (OPG) in age determination. A computerized systematic literature search of studies published up to January 2020 was conducted without language restrictions in order to identify articles comparing CBCT vs. OPG in dental anatomy evaluation, articles evaluating the accuracy of dental methods for age estimation, both with CT and OPG exams, and articles comparing CBCT vs. OPG in terms of radiation dose. CBCT was found to be more accurate compared to OPG in dental anatomy evaluation. When analyzing young adults, an estimation error of two years is considered forensically acceptable. The radiation dose of a CBCT exam is higher compared to an OPG exam. However, the difference is not as marked with small Fields Of View (FOV) and low-resolution protocols. Final conclusion was that a small FOV CBCT centered on the mandibular angle of a young patient is an accurate and safe method for dental age estimation around the age of 18.

Three-dimensional image analysis of developing mandibular third molars apices for age estimation: A study using CBCT data enhanced with Mimics & 3-Matics software

Three-dimensional imaging has improved the method of analysis in many forensic science investigations. The study aimed to derive regression equation for age estimation by investigating the relationship between chronological age and surface area of the developing mandibular 3rd molars apices. Furthermore, other predictor variables: ethnicity (Malay and Chinese), gender and status of the root development completion (open/closed apices) were also investigated in terms of fit to the age estimation model. One hundred and twenty eight training and 55 validation samples of intact mandibular 3rd molars were selected from 183 CBCT scans. The samples comprised of 93 Malays and 90 Chinese, ranging in age from 13 to 24 years. Three-dimensional image modeling and surface area analysis of the developing mandibular 3rd molars apices were performed using Mimics and 3-Matics software. Multiple linear regression analysis was used to derive age estimation model using chronological age as a dependent variable and surface area of the apices, ethnicity, gender and status of the root development completion (open/closed apices) as predictor variables. A strong inverse correlation (r = 0.95, SD = 1.144) was observed between chronological age and all the predictor variables. The results showed that 89.6% of the variation in age can be explained by the predictor variables. Mean absolute error (MAE) value of 0.8223 was observed when the derived regression equation was tested on the independent validation sample. In conclusion, three-dimensional surface area analysis of the developing mandibular 3rd molars apices can be used as a reliable method for age estimation.

CT and MR imaging used in age estimation: a systematic review

Computer Tomography (CT) and Magnetic Resonance Imaging (MRI) may be useful tools in assessment of age of an individual. This article presents a review of published studies using CT or MRI in dental age estimation. They were published between July 2004 and September 2017 investigating different types of teeth, methods and formulae for age estimation. Twenty-seven articles were included. The different studies show good results, and it seems that a combination of different types of teeth, methods (depending on the degree of root formation) and cooperation between different disciplines in the same study gives a higher accuracy.

Effect of demineralization time on the mineral composition and mechanical properties of remineralized dentin

The aim of this study was to determine whether recovery of mineral levels restored the mechanical properties of dentin subjected to different durations of demineralization. Dentin at the floor of class 1 cavities (n = 12) was demineralized for 1, 2, and 3 weeks. Half the demineralized cavity floor was coated (control side), and a Fuji IX restoration was placed. The remaining half was therefore in contact with the Fuji IX restoration (test side). Simulated dentin tubular fluid was then supplied to each pulp chamber for 6 weeks. After remineralization, the teeth were detached from the system and sectioned. Concentrations of calcium, phosphorus, fluorine, and strontium and mechanical properties (hardness and Young's modulus) of the test and control sides were determined by electron probe microanalysis and nano-indentation, respectively. For remineralized dentin demineralized for 1 week, the substantial uptake of mineral elements restored hardness and Young's modulus at depths of 50 to 200 μm from the lesion front. For longer periods of demineralization (2 and 3 weeks), structural damage to the demineralized dentin was severe and impeded recovery of mechanical properties, despite mineral uptake.

Forensic age estimation based on development of third molars: a staging technique for magnetic resonance imaging

BACKGROUND

The development of third molars can be evaluated with medical imaging to estimate age in subadults. The appearance of third molars on magnetic resonance imaging (MRI) differs greatly from that on radiographs. Therefore a specific staging technique is necessary to classify third molar development on MRI and to apply it for age estimation.

AIM

To develop a specific staging technique to register third molar development on MRI and to evaluate its performance for age estimation in subadults.

MATERIALS AND METHODS

Using 3T MRI in three planes, all third molars were evaluated in 309 healthy Caucasian participants from 14 to 26 years old. According to the appearance of the developing third molars on MRI, descriptive criteria and schematic representations were established to define a specific staging technique. Two observers, with different levels of experience, staged all third molars independently with the developed technique. Intra- and inter-observer agreement were calculated. The data were imported in a Bayesian model for age estimation as described by Fieuws et al. (2016). This approach adequately handles correlation between age indicators and missing age indicators. It was used to calculate a point estimate and a prediction interval of the estimated age. Observed age minus predicted age was calculated, reflecting the error of the estimate.

RESULTS

One-hundred and sixty-six third molars were agenetic. Five percent (51/1096) of upper third molars and 7% (70/1044) of lower third molars were not assessable. Kappa for inter-observer agreement ranged from 0.76 to 0.80. For intra-observer agreement kappa ranged from 0.80 to 0.89. However, two stage differences between observers or between staging sessions occurred in up to 2.2% (20/899) of assessments, probably due to a learning effect. Using the Bayesian model for age estimation, a mean absolute error of 2.0 years in females and 1.7 years in males was obtained. Root mean squared error equalled 2.38 years and 2.06 years respectively. The performance to discern minors from adults was better for males than for females, with specificities of 96% and 73% respectively.

CONCLUSION

Age estimations based on the proposed staging method for third molars on MRI showed comparable reproducibility and performance as the established methods based on radiographs.

Three-dimensional analysis of third molar development to estimate age of majority

Third molars are one of the few biological markers available for age estimation in undocumented juveniles close the legal age of majority, assuming an age of 18years as the most frequent legal demarcation between child and adult status. To obtain more accurate visualization and evaluation of third molar mineralization patterns from computed tomography images, a new software application, DentaVol©, was developed. Third molar mineralization according to qualitative (Demirjian's maturational stage) and quantitative parameters (third molar volume) of dental development was assessed in multi-slice helical computed tomography images of both maxillary arches displayed by DentaVol© from 135 individuals (62 females and 73 males) aged between 14 and 23years. Intra- and inter-observer agreement values were remarkably high for both evaluation procedures and for all third molars. A linear correlation between third molar mineralization and chronological age was found, with third molar maturity occurring earlier in males than in females. Assessment of dental development with both procedures, by using DentaVol© software, can be considered a good indicator of age of majority (18years or older) in all third molars. Our results indicated that virtual computed tomography imaging can be considered a valid alternative to orthopantomography for evaluations of third molar mineralization, and therefore a complementary tool for determining the age of majority.

Staging of third molar development in relation to chronological age of 5-16 year old Indian children

BACKGROUND

The usefulness of the developmental status of the third molar has been studied in assessment of the chronological age of adolescents in whom the development of the other permanent teeth is nearly complete. However, little is known about the timing and pattern of third-molar development in the Indian population.

AIM

This study aimed to stage the third molar development in relation to chronological age of 5-16year old Indian children.

DESIGN

In this cross-sectional observational study, the status of third molar development in relation to chronological age of 1139 Indian children aged 5-16 years was evaluated radiographically, using Orhan's modification of Demirjian's method.

RESULTS

The frequency of occurrence of the third molars varied from 47% to 70%. Crypt formation, crown completion and root completion occurred as early as 5.4, 8.7 and 15.0 years, respectively. No significant differences based on gender or side were observed in third-molar development (p>0.05). For most stages, maxillary third molars were slightly more advanced than their mandibular counterparts (p>0.05).

CONCLUSION

Considering the high degree of variability observed in third molar genesis and development, the usefulness of this tooth in age determination studies may be very limited in the age group studied.

Radiographic evaluation of third molar development in 6- to 24-year-olds

Purpose

This study investigated the developmental stages of third molars in relation to chronological age and compared third molar development according to location and gender.

Materials and Methods

A retrospective analysis of panoramic radiographs of 2490 patients aged between 6 and 24 years was conducted, and the developmental stages of the third molars were evaluated using the modified Demirjian's classification. The mean age, standard deviation, minimal and maximal age, and percentile distributions were recorded for each stage of development. A Mann-Whitney U test was performed to test the developmental differences in the third molars between the maxillary and mandibular arches and between genders. A linear regression analysis was used for assessing the correlation between the third molar development and chronological age.

Results

The developmental stages of the third molars were more advanced in the maxillary arch than the mandibular arch. Males reached the developmental stages earlier than females. The average age of the initial mineralization of the third molars was 8.57 years, and the average age at apex closure was 21.96 years. The mean age of crown completion was 14.52 and 15.04 years for the maxillary and the mandibular third molars, respectively.

Conclusion

The developmental stages of the third molars clearly showed a strong correlation with age. The third molars developed earlier in the upper arch than the lower arch; further, they developed earlier in males than in females.

The chronology of third molar root mineralization in south Indian population

The aim of present study was to determine the chronology of third molar root mineralization and to establish south Indian reference data. Therefore, a cross-sectional study was undertaken by evaluating 192 intraoral periapical radiographs in order to assess the root mineralization status of the mandibular third molar of south Indian individuals (101 males and 91 females) between the age of 13 and 25. The evaluation was carried out using the seven-stage developmental scheme of Kullman et al. (1992). The range, mean age, standard deviation, Student t test and percentile distributions are presented for each stage of mineralization. Statistically significant differences between males and females were not found. All individuals from this study with mature third molar roots were at least 18 years of age. For medicolegal purposes, the likelihood of whether a south Indian individual is older than 18 years or not was determined.

Age estimation based on pulp cavity to tooth volume ratio using postmortem computed tomography images

Pulp cavity size is known to decrease with age and can therefore serve as an indicator for age estimation. Here, we evaluated whether reconstructed images of multidetector-row computed tomography (MDCT) acquired before forensic autopsy are useful for estimating age at death. Images of 136 mandibular first premolars obtained from bodies of known age at death were analyzed, and the volume of the regions corresponding to pulp cavity and that of the whole tooth were determined using a voxel counting function. The pulp cavity was clearly distinguishable from dental hard tissue on the reconstructed images when using a cutoff value of 1400 Hounsfield units. Regression analysis adjusted for sex showed that estimated age correlated significantly with the pulp cavity to tooth volume ratio (r = 0.76). MDCT is gaining more widespread use in forensic medicine, and analyzing dental images to obtain parameters for age prediction is a practical approach for postmortem identification.

Radiological age estimation: based on third molar mineralization and eruption in Turkish children and young adults

Radiographic evaluation of mineralization and eruption stages of third molars using dental panoramic radiographies can be an efficient tool for chronological age estimation in both forensic sciences and legal medicine. The third molar tooth is utilized for dental age estimation about the age span of 15-23 years because it represents the only tooth still in development. The aim of this study is to obtain and analyze data regarding third molar development and eruption in Turkish population for dental age estimation. A total of 744 dental panoramic radiographies of 394 female and 350 male subjects aged between 8 and 22 years were examined. Third molar development was determined according to the Nolla classification system, and eruption was assessed relative to the alveolar bone level. Mandibular and maxillary third molars were generally found at similar stages of development on both sides. Nolla stage 6 (completed crown calcification) was reached at around the age of 15 in both maxillary and mandibular third molars in both sexes. Alveolar emergence was at around the age of 16 in males and around age of 17 in females. Although third molars' eruption shows greater variability than development of third molars, data which were obtained from this study about eruption of these teeth can be supportive to development data for age estimation.

Radiographic analysis of epiphyseal fusion at knee joint to assess likelihood of having attained 18 years of age

Radiological analysis of the epiphyses of the knee joint provides new valuable information, which may be used in combination with these well-established techniques in order to maximise the accuracy in the assessment of age of 18 years. A total of 215 antero-posterior radiographs of the knee was reviewed retrospectively in patients aged between 14 and 24 years old (99 boys, 116 girls). Fusion was scored as stage 1, epiphysis not fused; stage 2, epiphysis is fully ossified and epiphyseal scar is visible; and stage 3, epiphysis is fully ossified and epiphyseal scar is not visible. Scores of 0, 1 and 2 were assigned to stages 1, 2 and 3, respectively. Lastly, the score related to epiphyseal fusion at the knee joint was obtained by adding the three scores of the distal femur, proximal tibia and proximal fibula. Age distribution gradually increased with each score, for both genders. The mean age (±standard error) in each score category varied between genders, but the differences were not significant (p > 0.11). Five tests were performed to discriminate between individuals who were or were not at age 18 years or more, according to the receiver operating curve. For boys, the highest value of accuracy was obtained with score 3, with high sensitivity (Se = 93.33 %) and specificity (Sp = 89.29 %). For girls, it was obtained with score 4, with high accuracy (Acc = 85.86 %). These results indicate that radiographic analysis of the knee is a valuable alternative as a non-invasive method of estimation of 18 years of age.

The incidence of asymmetrical left/right skeletal and dental development in an Australian population and the effect of this on forensic age estimations

The prevalence of developmental asymmetry between left and right sides of the body in the third molar tooth and medial clavicular epiphysis is examined in a contemporary Australian population (92% Caucasian). The contention that differences between left and right side developmental timing is statistically insignificant, and can therefore be ignored in forensic age estimation procedures, is questioned. It was found that of a population sample of 604 individuals, 177 displayed asymmetrical timing in development between antimeres of the third molar, the medial clavicle or both. There was no correlation found between the third molar tooth and medial clavicular epiphysis in terms of left/right synchronicity. For those individuals differing in development by two or more developmental stages in either age marker or one stage in both age markers, the effect upon the accuracy of forensic age estimations can be significant. Differences in age estimates for each side were as much as 3.1 years. Age estimations based on one side only may not provide the best estimate for an individual, and more accurate results can be achieved if both sides are taken into consideration. A protocol for dealing with asymmetrical development is discussed with reference to the multifactorial age estimation method proposed by the same authors in previous research.