The inter-examiner variation in rating dental formation from radiographs

Root canal width 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 ratio of the root canal widths (RCW) of the mandibular first, second and third molars is a useful indicator of age.

METHODS

Nine hundred eighteen dental panoramic radiographs (DPT) were examined and the ratio of the mid-points of the distal roots of the left mandibular first, second and third molars assessed according to the RCW stages as described by Roberts (J Forensic Sci 62:351-354, 2017).

RESULTS

Individuals who had reached stages RCW-A and RCW-B were represented in a wide range of ages spanning the 18-year-old threshold. Individuals who had reached Stage RCW-C were all above the 18-year-old threshold. It was not possible to analyse a large number of DPTs for various reasons.

DISCUSSION

Individuals categorised as stage RCW-C may be deemed to have reached the 18-year-old threshold. These results are consistent with other published studies. Variation in root morphology and in the rate of development of the third molar limits the applicability of this method.

CONCLUSIONS

RCW staging is an accurate method of determining the 18-year-old threshold. Its limited applicability requires the use of substitute markers in a large number of cases.

Relationship between dental calcification of mandibular teeth and cervical vertebrae maturity in patients with unilateral complete cleft lip and palate

OBJECTIVE

The purpose of this study was to investigate the relationship between the dental calcification stage (DCS) of the mandibular teeth and the cervical vertebral maturation stage (CVMS) in patients with unilateral complete cleft lip and palate (UCLP).

METHODS

One hundred sixty-two UCLP patients (100 males and 62 females) between 8-16 years old were included in this study. The DCS was estimated by the Demirjian method and was converted to the dental age (DA). The CVMS was evaluated by the Baccetti method. The DA of mandibular teeth on two sides of the cleft were analyzed using a t-test. Spearman correlation was used to study the association between CVMS and DCS. The correlation coefficient between the two sides of the cleft was then compared.

RESULTS

The total DA was significantly smaller on the cleft side than on the noncleft side in males (p = 0.022). The Spearman rank correlation coefficient revealed a significant correlation between the DCS of each examined tooth and the CVMS (r = 0.627-0.793 in males and r = 0.806-0.899 in females). Additionally, the correlation of the two sides was not significantly different (p > 0.05). The DCS of the first premolar showed the strongest correlation with the CVMS.

CONCLUSION

The results confirm the utility of the DCS on both sides of the mandible in male UCLP patients as a simple first-level diagnostic test to evaluate growth and development. The findings also indicate that both the DCS and the CVMS should be assessed if the maturity stage of a growing UCLP patient is relevant to clinical practice.

Multi-factorial age estimation: A Bayesian approach combining dental and skeletal magnetic resonance imaging

PURPOSE

To study age estimation performance of combined magnetic resonance imaging (MRI) data of all four third molars, the left wrist and both clavicles in a reference population of females and males. To study the value of adding anthropometric and sexual maturation data.

MATERIALS AND METHODS

Three Tesla MRI of the three anatomical sites was prospectively conducted from March 2012 to May 2017 in 14- to 26-year-old healthy Caucasian volunteers (160 females, 138 males). Development was assessed by allocating stages, anthropometric measurements were taken, and self-reported sexual maturation data were collected. All data was incorporated in a continuation-ratio model to estimate age, applying Bayes' rule to calculate point and interval predictions. Two performance aspects were studied: (1) accuracy and uncertainty of the point prediction, and (2) diagnostic ability to discern minors from adults (≥18 years).

RESULTS

Combining information from different anatomical sites decreased the mean absolute error (MAE) compared to incorporating only one site (P<0.0001). By contrast, adding anthropometric and sexual maturation data did not further improve MAE (P=0.11). In females, combining all three anatomical sites rendered a MAE equal to 1.41 years, a mean width of the 95% prediction intervals of 5.91 years, 93% correctly classified adults and 91% correctly classified minors. In males, the corresponding results were 1.36 years, 5.49 years, 94%, and 90%, respectively.

CONCLUSION

All aspects of age estimation improve when multi-factorial MRI data of the three anatomical sites are incorporated. Anthropometric and sexual maturation data do not seem to add relevant information.

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.

An automated technique to stage lower third molar development on panoramic radiographs for age estimation: a pilot study

BACKGROUND

Automated methods to evaluate growth of hand and wrist bones on radiographs and magnetic resonance imaging have been developed. They can be applied to estimate age in children and subadults. Automated methods require the software to (1) recognise the region of interest in the image(s), (2) evaluate the degree of development and (3) correlate this to the age of the subject based on a reference population. For age estimation based on third molars an automated method for step (1) has been presented for 3D magnetic resonance imaging and is currently being optimised (Unterpirker et al. 2015).

AIM

To develop an automated method for step (2) based on lower third molars on panoramic radiographs.

MATERIALS AND METHODS

A modified Demirjian staging technique including ten developmental stages was developed. Twenty panoramic radiographs per stage per gender were retrospectively selected for FDI element 38. Two observers decided in consensus about the stages. When necessary, a third observer acted as a referee to establish the reference stage for the considered third molar. This set of radiographs was used as training data for machine learning algorithms for automated staging. First, image contrast settings were optimised to evaluate the third molar of interest and a rectangular bounding box was placed around it in a standardised way using Adobe Photoshop CC 2017 software. This bounding box indicated the region of interest for the next step. Second, several machine learning algorithms available in MATLAB R2017a software were applied for automated stage recognition. Third, the classification performance was evaluated in a 5-fold cross-validation scenario, using different validation metrics (accuracy, Rank-N recognition rate, mean absolute difference, linear kappa coefficient).

RESULTS

Transfer Learning as a type of Deep Learning Convolutional Neural Network approach outperformed all other tested approaches. Mean accuracy equalled 0.51, mean absolute difference was 0.6 stages and mean linearly weighted kappa was 0.82.

CONCLUSION

The overall performance of the presented automated pilot technique to stage lower third molar development on panoramic radiographs was similar to staging by human observers. It will be further optimised in future research, since it represents a necessary step to achieve a fully automated dental age estimation method, which to date is not available.

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.

Accuracy of Demirjian's 8 teeth method for age prediction in South Indian children: A comparative study

Introduction:

Demirjian's method of tooth development is most commonly used to assess age in individuals with emerging teeth. 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. Original Demirjian's method utilized seven mandibular teeth, to which recently third molar is added so that the method can be applied on a wider age group. Furthermore, the revised method developed regression formulas for assessing age. In Indians, as these formulas resulted in underestimation, India-specific regression formulas were developed recently. The purpose of this cross-sectional study was to evaluate the accuracy and applicability of original regression formulas (Chaillet and Demirjian 2004) and India-specific regression formulas (Acharya 2010) using Demirjian's 8 teeth method in South Indian children of age groups 9–20 years.

Methods:

The present study consisted of 660 randomly selected subjects (330 males and 330 females) were in the aged ranging from 9 to 20 years divided into 11 groups according to their age. Demirjian's 8 teeth method was used for staging of teeth.

Results:

Demirjian's method underestimated the dental age (DA) by 1.66 years for boys and 1.55 years for girls and 1.61 years in total. Acharya's method over estimated DA by 0.21 years for boys and 0.85 years for girls and 0.53 years in total. The absolute accuracy was better for Acharya's method compared with Demirjian method.

Conclusion:

This study concluded that both the Demirjian and Indian regression formulas were reliable in assessing age making Demirjian's 8 teeth method applicable for South Indians.

Dental maturation of unilateral cleft lip and palate

Cleft lip and palate (CLP) is the most common craniofacial abnormality and the fourth most common birth defect in Singapore. Many reports suggest that CLP children have delayed dental development and asymmetrical timing of tooth-pair formation. The aim of this study was to investigate the timing of development of permanent teeth in unilateral CLP (UCLP) children and to compare the findings with non-CLP children in Singapore. A total of 60 UCLP children aged between 5 and 9 years (mean 6.64 ± 0.90 years) and a non-CLP control group matched for age, gender, and race were investigated and compared. Dental records and radiographs were studied and the dental maturation was determined using the Demirjian's method (1973). The dental maturation of UCLP children were delayed compared with non-CLP children by a mean of 0.55 ± 0.75 years and the delay was statistically significant (P < 0.001). The UCLP group also had significantly higher risk of asymmetrically developing tooth pairs than the control group (P < 0.001). The most commonly delayed tooth in development was the maxillary cleft-sided lateral incisor. In conclusion, the UCLP children in Singapore demonstrated delayed dental maturation and a higher occurrence of asymmetrical tooth-pair formation than the non-CLP children.

Accuracy of population-specific Demirjian curves in the estimation of dental age of Saudi children

BACKGROUND

The Demirjian eight-stage method is one of the principal methods used to quantify the degree of maturity from age 3 to 17. Aim.  The objective of this study was to compare the accuracy of dental age of different population-specific curves, derived using the Demirjian method, to the chronological age of Saudi children aged between 4 and 14.

DESIGN

Panoramic radiographic records of 176 children (91 boys and 85 girls), without any history of systemic disease, were assessed using the Demirjian method, and the dental age was calculated using curves designed for French-Canadian, Belgian, Kuwaiti, and Saudi children. The difference from chronological age (DA-CA) for each curve was then statistically compared using ANOVA, and each of the curves was compared to the chronological age using multinomial regression modelling.

RESULTS

The results suggest that although population-specific curves are more accurate in the prediction of age, a considerable variation within each population still exists.

CONCLUSIONS

The Demirjian method offers great scope in fields that require the study of the pattern of growth rather than the accuracy of age estimation.

Correlation between dental maturation and chronological age in patients with cerebral palsy, mental retardation, and Down syndrome

Determining a child's chronological age and stage of maturation is particularly important in fields such as paediatrics, orthopaedics, and orthodontics, as well as in forensic and anthropological studies. Some systemic conditions can cause abnormal physiological maturation, and skeletal maturation is usually more delayed than dental maturation. The aim of this study was to determine dental age in a group of patients with the most prevalent congenital or perinatally occurring physical and mental disabilities. The study group comprised 155 white Spanish children aged 3-17 years (35 with cerebral palsy, 83 with mental retardation and no associated syndromes or systemic conditions, and 37 with Down syndrome). The dental maturation indices described by Nolla and Demirjian were used to generate regression lines for the dental age of individuals in a control group (688 white Spanish children aged 3-17 years) and the formulae were then used to determine the dental age of patients in the study group. No significant differences were found between dental and chronological age in boys with cerebral palsy, mental retardation, or Down syndrome. In contrast, dental age (calculated from the linear regression model that included values for the Demirjian index) was significantly delayed compared with chronological age in girls with cerebral palsy or Down syndrome.

Age estimation in Indians using Demirjian's 8-teeth method

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 in Central Poland

Precise evaluation of the developmental stage of a child is an integral part of both diagnosis and treatment of pediatric patients; it is also essential in forensic medicine and dentistry. Among radiological methods for dental age estimation in children the Demirjian's method is widely used, however original standards elaborated for the French-Canadian population are mostly not suitable for other populations. The aim of the study was to compare the dental age of children from the region of Mazovia (Central Poland) with the developmental standards presented by Demirjian, to analyse sexual dimorphism of dental age in the studied group and to estimate validity of the Demirjian's standards for the studied Polish population. The material consisted of clinical files and panoramic X-ray images of 994 children aged from 6 to 16 in good general health, without development impairments. Chronological ages of the patients were established. Next dental ages were estimated by means of the Demirjian method based on developmental maturity of seven left mandibular permanent teeth. It was found that the standards were significantly different from the chronological ages in the studied population, which means that dental development was considerably accelerated. The most significant acceleration was observed in girls aged 11 and 12, as well as in 13-year-old boys; in both groups a considerable acceleration of the dental age was seen in 6-year-olds. No statistically significant differences between dental ages of girls and boys were observed in particular age groups. There were devised gender-specific equations allowing for adaptation of original Demirjian's scores for estimation of dental age in the population of Mazovia (Central Poland). In conclusion, the developmental standards used by Demirjian are not suitable in the case of the population of children of Central Poland. Therefore, it is necessary to establish new tables for this population.

Reproducibility of radiographic stage assessment of third molars

The aim of this study was to determine intra- and inter-observer variability of the developing third molar from panoramic radiographs. Formation of third molars was assessed according to stages described by modified Demirjian et al.'s methods: Moorrees et al. [C.F.A. Moorrees, E.A. Fanning, E.E. Hunt, Age variation of formation stages for ten permanent teeth, J. Dent. Res. 42 (1963) 1490-1502] and Solari and Abramovitch [A.C. Solari, K. Abramovitch, The accuracy and precision of third molar development as an indicator of chronological age in Hispanics, J. Forensic Sci. 47 (2002) 531-535]; in addition, data were also analysed unmodified, i.e. Haavikko [K. Haavikko, The formation and alveolar and clinical eruption of the permanent teeth, an orthopantomograph study, Proc. Finn. Dent. Soc. 66 (1970) 104-170] and Demirjian et al. [A. Demirjian, H. Goldstein, J.M. Tanner, A new system of dental age assessment, Hum. Biol. 45 (1973) 211-227]. The sample was a random selection of 73 panoramic radiographs from patients aged 8-24 years. After training, the left maxillary and mandibular third molars were scored on two separate occasions without knowledge of previous scores. Cohen's Kappa and percentage agreement were calculated for each method, for maxillary, for mandibular third molars and combined. Percentage agreement for stages was also calculated. Intra-observer agreement was greater for mandibular third molars compared to maxillary third molars, and better for methods with fewer stages. Kappa values indicated good agreement for most methods; the best was Demirjian et al.'s method for mandibular third molar with very good agreement (K = 0.80) for the first author, good agreement for the second author (K = 0.75) and good agreement between observers (K = 0.75). The stages with best agreement were Demirjian's stage E [A. Demirjian, H. Goldstein, J.M. Tanner, A new system of dental age assessment, Hum. Biol. 45 (1973) 211-227] and Moorrees et al.'s stage Cc and R1/4 [C.F.A. Moorrees, E.A. Fanning, E.E. Hunt, Age variation of formation stages for ten permanent teeth, J. Dent. Res. 42 (1963) 1490-1502].

CONCLUSIONS

Having clearly defined stages and fewer stages allowed better reproducibility of third molar formation.

The influence of jaw innervation on the dental maturation pattern in the mandible

OBJECTIVES

To explore the relationship between mandibular dental maturation and the pattern of jaw innervation.

SETTING AND SAMPLE POPULATION

The sample included 365 panoramic radiographs taken in the period 1965-1969 in a Danish municipality.

DESIGN

For assessing dental maturity, the seven left mandibular teeth (M2, M1, P2, P1, C, I2, I1) were given a dental maturity score according to a method introduced by Demirjian. Spearman correlation coefficients between the maturity score of an index tooth (one of each teeth) and the maturity score of the 6 other teeth was calculated and illustrated.

RESULTS

All the correlation coefficients were larger than 0.5 indicating a rather high level of association between the development of mandibular teeth in the same individual. Thus, associations between the pattern of dental maturation and jaw innervation were not obvious.

CONCLUSION

When the correlation between the dental maturity stages was analysed, no significant relation was found between dental maturation and jaw innervation in the mandible. This is interesting considering the results presented in a recent study, which showed that the clinical observed tooth eruption was closely related to the pattern of jaw innervation. Those authors suggested that the factors influencing the eruption might be associated with jaw innervation. In our study, the stepwise dental maturation process, however, is not equally associated with jaw innervation.

Dental maturity of children in Perth, Western Australia, and its application in forensic age estimation

The dental maturity of 1450 healthy children from Perth, Western Australia, was determined in a cross-sectional study. Orthopantomographs of 690 males and 760 females aged 4-16 years old, were randomly selected from various dental practices and hospitals in the Perth metropolitan area. Dental maturity was determined by the method of Demirjian and Goldstein based on the development of four permanent mandibular teeth. Curves were constructed for the Perth children and then compared to that of Demirjian and other studies using the same method. Girls were more advanced dentally than boys. Perth boys showed more advanced dental maturation than French-Canadian boys for ages 6-10 years. Perth girls showed advancement over French-Canadian girls for ages 5-11 years. The same pattern was seen with Hong Kong Chinese children. London and Finnish children, however, were more advanced for the older age groups, 10-16 years, compared to Perth children. Dental age as determined from maturity scores using this method revealed a highly significant correlation with chronological age. From our results we conclude that the method devised by Demirjian and Goldstein is accurate and reliable for forensic age determination within the Perth population, but variations do exist between different population groups.

Validity of the Demirjian method for dental age estimation when applied to Norwegian children

Dental age was studied in a sample of 261 Norwegian children by using the maturity standards of Demirjian & Goldstein (1976) to examine the applicability of these standards as a reference for overall dental maturity in a Norwegian population. The sample comprised 128 boys and 133 girls included in 'the Oslo Growth Material', from whom orthopantomograms (total, 783) had been longitudinally obtained, with intervals of about 3 years and covering 3 age spans (5.5-6.5 years, 8.5-9.5 years, and 11.5-12.5 years), each divided into 3 half-year age groups. Reliability was analyzed by repeated assessments of 134 of the radiographs, and the overall mean difference between duplicate dental age determinations was 0.5 months for intra- and 1.8 months for inter-examiner comparisons. The Norwegian children were generally somewhat advanced in dental maturity compared with the French-Canadian reference sample. Among the boys the mean difference between dental age and chronologic age varied in the different age groups from 1.5 to 4.0 months. Among the girls the difference increased with age, varying from 0 to 3.5 months in the younger age groups (5.5 to 9.0 years) and from 4.5 to 7.5 months in the age groups 9.5 years and above. The variability in individual dental age was marked and increased with age. For the older age groups 95% of the individual age estimates were within +/-2 years of the real age. The applied standards appear to be adequate for studying dental age in groups of children from a Norwegian population. Given the considerable individual variation in dental maturity, estimation of chronologic age in individual children should be supplemented by other indicators of biologic maturity.

Methods of reducing observer variation in age estimation from panoramic radiographs

OBJECTIVE

To compare inter- and intra-observer variation in age estimation using subjective and objective methods.

METHODS

Fifty-six panoramic radiographs of patients aged 13 to 25 years were assessed subjectively twice by four observers for the stage of root development of the lower third molars on a seven-point scale. Two of the observers were calibrated before the first evaluation, and the other two before the second. The same observers also digitized predefined reference points in a subsample of the third molars ten times by means of a computer-based digitizer system. Observer variation in classifying different root stages and in digitizing coordinates and measuring root lengths were studied.

RESULTS

Significant systematic differences existed between two of the observers in the subjective assessment. One non-pre-calibrated observer changed her pattern most. Scattergrams from the digitizer measurements showed a good precision within and between observers with no significant differences in calculating root lengths. When, however, the teeth were analysed separately, some significant differences were found.

CONCLUSIONS

The overall observer agreement was best using the objective method on several teeth. With only one tooth there were some significant differences. Subjective evaluation was improved by prior calibration.

Comparisons of dental maturity between the rural community of Kuhmo in northeastern Finland and the city of Helsinki

The aim of the study was to check whether dental maturity charts made in southern Finland can be used without modifications in other parts of the country. For this reason the dental maturity of 90 children living in the sparsely populated areas of Kuhmo in northeastern Finland was compared with that of a larger sample of Helsinki children. Most of the Kuhmo children were 7.0-8.5 and 10.5-12.5 yr of age. The method of Demirjian and associates was used to estimate dental maturity. The means of dental maturity scores were greater in Kuhmo in most half-year groups in both sexes. The median dental maturity scores of Kuhmo children were between the 50th and 84th percentile curves of Helsinki children. A referent of the same age and sex was chosen for each Kuhmo child from the Helsinki children. The paired t-test was based on the difference in dental age. The dental age of the Kuhmo children was higher (P less than 0.05). These findings suggest differences in dental maturity within a fairly homogeneous population, which should be considered when national charts are used.

Sexual dimorphism in the development, emergence, and agenesis of the mandibular third molar

Bilateral agenesis was encountered in about 9% of the cases, with no significant sexual difference. The right and left mandibular third molars had the same pattern of development and emergence. The slight advance of girls over boys at the crown-completion stage was similar to previous observations on other mandibular teeth, particularly the second molar. The root development course of the third molar was faster in males than in females; this sexual dimorphism was much greater for retarded cases than for advanced cases. At the apex closure, the difference between median ages of males and females was 1.5 yr. Alveolar emergence tended to occur at a lower developmental stage in advanced cases compared with retarded cases.