Helen M. Liversidge

Brief Communication: The London Atlas of Human Tooth Development and Eruption

The aim of this study was to develop a comprehensive evidence-based atlas to estimate age using both tooth development and alveolar eruption for human individuals between 28 weeks in utero and 23 years. This was a cross-sectional, retrospective study of archived material with the sample aged 2 years and older having a uniform age and sex distribution. Developing teeth from 72 prenatal and 104 postnatal skeletal remains of known age-at-death were examined from collections held at the Royal College of Surgeons of England and the Natural History Museum, London, UK (M 91, F 72, unknown sex 13). Data were also collected from dental radiographs of living individuals (M 264, F 264). Median stage for tooth development and eruption for all age categories was used to construct the atlas. Tooth development was determined according to Moorrees et al. (J Dent Res 42 (1963a) 490-502; Am J Phys Anthropol 21 (1963b) 205-213) and eruption was assessed relative to the alveolar bone level. Intraexaminer reproducibility calculated using Kappa on 150 teeth was 0.90 for 15 skeletal remains of age <2 years, and 0.81 from 605 teeth (50 radiographs). Age categories were monthly in the last trimester, 2 weeks perinatally, 3-month intervals during the first year, and at every year thereafter. Results show that tooth formation is least variable in infancy and most variable after the age of 16 years for the development of the third molar.

Timing of Demirjian's tooth formation stages

Background: Global differences in Demirjian et al.s method of assessing dental maturity are thought to be due to population differences. Aim: The aim of this study was to investigate the timing of individual tooth formation stages in children from eight countries. Research design: This was a meta-analysis of previously published data from retrospective cross-sectional studies of dental maturity. Method: Data of mandibular permanent developing teeth from panoramic radiographs (Demirjians stages) were combined from Australia, Belgium, Canada, England, Finland, France, South Korea and Sweden (n = 9002, ages 2–16.99 years). Age-of-attainment was calculated using logistic regression for each group by sex and meta-analysis of the total. Overlapping 95% confidence intervals of the means was interpreted as no significant difference. Results: Mean ages for each group and total were significantly different in 65 out of 509 comparisons (p < 0.05). Some of these were of small sample size but there was no consistent pattern. Apex closure of the first molar was significantly later in children from Quebec and this might explain differences found in the dental maturity score. Conclusions: These results suggest no major differences in the timing of tooth formation stages between these children. This fails to explain previous findings of differences using Demirjians dental maturity method. Résumé.Arrière plan: On pense que les différences globales dans la méthode de Demirjian et al. d’appréciation de la maturité dentaire sont dues à des différences entre populations. Objectif: Cette étude a pour objet d’observer la chronologie individuelle des stades de formation de la dent chez des enfants de huit nations. Type de recherche: Il s’agit d’une méta-analyse de données d’enquêtes transversales rétrospectives de maturité dentaire déjà publiées Méthode: Des données de radiographie panoramique de dents permanentes mandibulaires en voie de développement (stades de Demirjian) ont été recueillies en Autriche, Belgique, Canada, Angleterre, Finlande, France, Corée du Sud et Suède (n = 9002, âges de 2 à 16,99 ans). L’âge d’atteinte a été calculé au moyen de régressions logistiques pour chaque groupe par sexe et par méta-analyse de la totalité. Résultats: Les ages moyens de chaque groupe et de l’ensemble sont significativement différents dans 65 comparaisons sur 509 (p <0,05). Quelques différences sont de faible ampleur, mais sans qu’on puisse leur attribuer une signification particulière. La fermeture de l’apex de la première molaire est significativement plus Tardif chez les enfants du Québec, ce qui pourrait expliquer les differences observées dans les scores de maturité dentaire. Conclusion: Ces résultats suggèrent qu’il n’existe pas de différence majeure entre ces enfants dans la chronologie des stades de formation dentaire. Il n’est donc pas possible d’expliquer les différences trouvées dans des études antérieures par la méthode de maturité dentaire de Demirjian. Zusammenfassung.Hintergrund: Globale Unterschiede bei der Methode nach Demirjian et al. zur Bestimmung der Zahnreife werden ethnischen Unterschieden zugeschrieben. Ziel: Das Ziel dieser Studie war, die zeitliche Abfolge der individuellen Zahnentwicklung bei Kindern aus acht Ländern zu untersuchen. Untersuchungsaufbau: Dies war eine Meta-Analyse früher publizierter Daten aus retrospektiven Querschnittsuntersuchungen zur Zahnreife. Methode: Es wurden Daten aus Australien, Belgien, Kanada, England, Finnland, Frankreich, Südkorea und Schweden von Panorama-Röntgenaufnahmen der unteren bleibenden Zähne (Demirjian-Stadien) (n = 9002, Alter 2–16,99 Jahre) zusammengefasst. Das Alter zum Zeitpunkt des Zahndurchbruchs wurde unter Verwendung einer logistischen Regression geschlechtsspezifisch für jede Gruppe gerechnet und eine Meta-Analyse des gesamten Datensatzes vorgenommen. Überlappungen der 95%-Vertrauensintervalle von Mittelwerten wurden im Sinne nicht-signifikanter Unterschiede gedeutet. Ergebnisse: Mittleres Alter für jede Gruppe und insgesamt waren bei 65 von 509 Vergleichen signifikant unterschiedlich (p < 0,05). Einige Stichproben waren klein, aber es gab hier kein durchgehendes Muster. Der Zahnschluss der ersten Molaren war bei Kindern aus Quebec signifikant später, und dies könnte die beobachteten Unterschiede im Zahnreifungs-Score erklären. Zusammenfassung: Diese Ergebnisse legen nahe, dass es keine wesentlichen Unterschiede in der zeitlichen Abfolge der Zahnentwicklung dieser Kinder gibt. Damit wurden früher beobachtete Unterschiede bei Anwendung der Zahnreifebestimmungsmethode nach Demirjian nicht bestätigt. Resumen. Antecedentes: Se cree que las diferencias globales en el método de Demirjian et al. para estimar la madurez dental son debidas a diferencias poblacionales. Objetivo: El objetivo de este estudio fue investigar el momento de aparición de los estadios de formación dental individual en niños de ocho países. Diseño de la investigación: La investigación consistió en un meta-análisis de datos previamente publicados procedentes de estudios transversales retrospectivos de madurez dental. Método: Se combinaron datos de dientes permanentes en desarrollo de la mandíbula, a partir de radiografías panorámicas (estadios de Demirjian) procedentes de Australia, Bélgica, Canadá, Inglaterra, Finlandia, Francia, Corea del Sur y Suecia (n = 9.002, edades de 2,00--16,99 años). La edad de finalización se calculó utilizando una regresión logística para cada grupo y sexo y un meta-análisis del total. Un solapamiento del 95% de los intervalos de confianza de las medias se interpretó como que no existía ninguna diferencia significativa. Resultados: Las edades medias para cada grupo y para el total fueron significativamente diferentes en 65 de las 509 comparaciones (p <0,05). Algunas de éstas fueron de pequeño tamaño muestral, pero no existía un patrón consistente. El cierre apical del primer molar fue significativamente más tardío en los niños de Québec y esto podría explicar las diferencias encontradas en la puntuación de la madurez dental. Conclusiones: Estos resultados sugieren la no existencia de diferencias importantes en el momento de aparición de las etapas de la formación del diente entre estos niños. Esto no permite explicar los resultados previos sobre las diferencias observadas cuando se usa el método de la madurez dental de Demirjian.

Timing of human mandibular third molar formation

Background: Population differences in tooth formation using radiographs can be determined if the entire developmental sequence of a single tooth is studied. The only developing tooth visible radiographically from initiation to root completion is the third molar or wisdom tooth. Aim: The timing of mandibular third molar formation was documented for two groups of children in England and two in South Africa. Subjects and methods: Panoramic radiographs of White and Bangladeshi children from London and Black African and Cape Coloured children from South Africa were examined (age 5–24). Mean age of entering third molar stages (crypt appearance to root completion) was calculated using logistic regression and compared between sex and group using a t-test. Results: Average age of third molar stages was significantly (p < 0.001) later in three groups for almost all stages of the third molar compared to Black children. The average age of entering initial mineralization ranged from 7.97 to 9.74 years while average age of apex closed was 19.27–20.88. Conclusion: These results show for the first time a significant difference in the timing of maturation of the mandibular third molar between groups with South African Black children being earlier than other groups.

The accuracy of three methods of age estimation using radiographic measurements of developing teeth.

The accuracy of age estimation using three quantitative methods of developing permanent teeth was investigated. These were Mörnstad et al. [Scand. J. Dent. Res. 102 (1994) 137], Liversidge and Molleson [J. For. Sci. 44 (1999) 917] and Carels et al. [J. Biol. Bucc. 19 (1991) 297]. The sample consisted of 145 white Caucasian children (75 girls, 70 boys) aged between 8 and 13 years. Tooth length and apex width of mandibular canine, premolars and first and second molars were measured from orthopantomographs using a digitiser. These data were substituted into equations from the three methods and estimated age was calculated and compared to chronological age. Age was under-estimated in boys and girls using all the three methods; the mean difference between chronological and estimated ages for method I was -0.83 (standard deviation +/-0.96) years for boys and -0.67 (+/-0.76) years for girls; method II -0.79 (+/-0.93) and -0.63 (+/-0.92); method III -1.03 (+/-1.48) and -1.35 (+/-1.11) for boys and girls, respectively. Further analysis of age cohorts, found the most accurate method to be method I for the age group 8.00-8.99 years where age could be predicted to 0.14+/-0.44 years (boys) and 0.10+/-0.32 years (girls). Accuracy was greater for younger children compared to older children and this decreased with age.

Bias and Accuracy of Age Estimation Using Developing Teeth in 946 Children

Developing teeth are used to assess maturity and estimate age in several disciplines. The aim of the study was to determine which of the most well known dental age estimation methods was best at estimating age. The target sample of dental radiographs (N = 946, ages 3–16) was described by Maber et al. (Forensic Sci Int 159 (2006) S68–S73). Seven mandibular permanent teeth (I1–M2) were assessed, and dental age was calculated using four dental maturity scales and fifteen methods that use data for individual teeth. The mean difference between dental age and real age was calculated (bias) as well as several other measures of accuracy (mean/median absolute difference, percentage aged to within six months and to within 10% of real age). Most methods estimated age with significant bias and standard deviation of bias ranged from 0.86 to 1.03 years. Analysis by age group showed most methods over-aged younger children, and considerably under-aged older children. The method that performed best was the dental maturity scale of Willems et al. (J Forensic Sci 46 (2001) 893–895) with bias of −0.14 ± 0.86 years (N = 827), mean absolute difference of 0.66 years, 71% aged to 10% or less of age, and 49% aged to within six months. Two individual teeth, P2 and M2, estimated age with bias not significantly different to zero for most formation stages using methods based on a large reference sample (L9a Demirjian stages) and a uniform age distribution (N25a Moorrees stages). Standard deviation of bias was least for early crown stages and most for late root stages. Methods that average ages for individual teeth improve if schedules for ‘mean age entering a stage’ are adjusted for prediction. Methods that directly calculate ‘mean age within stage’ can be improved by drawing from a uniform age distribution.

Developing permanent tooth length as an estimate of age.

Developing teeth are widely used to predict age in archaeology and forensic science. Regression equations of tooth length for age is a direct method, however, data for permanent teeth is incomplete. The aims of this study were: (a) to calculate regression equations predicting age from tooth length of all permanent teeth from birth to maturity, and (b) to evaluate the difference between radiographic and actual tooth length. The sample studied (N = 76, age range 0 to 19 years) was the Spitalfields juveniles of recorded age-at-death. Tooth length was measured from incisal tip to developing edge of crown or root of 354 dissected teeth. Data for upper and lower teeth were combined except for the lateral incisor. The least squares regression method was used to analyze the data for each tooth type; age being regressed against tooth length for prediction. For most tooth types, growth followed an S-shaped (polynomial) curve with initial fast growth and a further growth spurt around the time of mid root formation. No difference was found between radiographic and true tooth length. These regression equations provide an easy method of predicting age from any developing permanent tooth by measuring tooth length from isolated teeth or from unmagnified, undistorted radiographs.

Accuracy of dental age estimation charts: Schour and Massler, Ubelaker and the London Atlas

Dental age estimation charts are frequently used to assess maturity and estimate age. The aim of this study was to assess the accuracy of estimating age of three dental development charts (Schour and Massler, Ubelaker, and the London Atlas). The test sample was skeletal remains and dental radiographs of known-age individuals (N = 1,506, prenatal to 23.94 years). Dental age was estimated using charts of Schour and Massler, Ubelaker, and The London Atlas. Dental and chronological ages were compared using a paired t-test for the three methods. The absolute mean difference between dental and chronological age was calculated. Results show that all three methods under-estimated age but the London Atlas performed better than Schour and Massler and Ubelaker in all measures. The mean difference for Schour and Massler and Ubelaker was -0.76 and -0.80 years (SD 1.27 year, N = 1,227) respectively and for the London Atlas was -0.10 year (SD 0.97 year, N = 1,429). Further analysis by age category showed similar accuracy for all three methods for individuals younger than 1 year. For ages 1-18, the mean difference between dental and chronological ages was significant (P < 0.05) for Schour and Massler and Ubelaker and not significant (P > 0.05) for the London Atlas for most age categories. These findings show that the London Atlas performs better than Schour and Massler and Ubelaker and represents a substantial improvement in accuracy of dental age estimation from developing teeth.

Malnutrition has no effect on the timing of human tooth formation.

The effect of nutrition on the timing of human tooth formation is poorly understood. Delays and advancements in dental maturation have all been reported as well as no effect. We investigated the effect of severe malnutrition on the timing of human tooth formation in a large representative sample of North Sudanese children. The sample (1102 males, 1013 females) consisted of stratified randomly selected healthy individuals in Khartoum, Sudan, aged 2-22 years using a cross-sectional design following the STROBE statement. Nutritional status was defined using WHO criteria of height and weight. Body mass index Z-scores and height for age Z-scores of ≤−2 (cut-off) were used to identify the malnourished group (N = 474) while the normal was defined by Z-scores of ≥0 (N = 799). Clinical and radiographic examination of individuals, with known ages of birth was performed including height and weight measurements. Mandibular left permanent teeth were assessed using eight crown and seven root established tooth formation stages. Mean age at entry and mean age within tooth stages were calculated for each available tooth stage in each group and compared using a t-test. Results show the mean age at entry and mean age within tooth stages were not significantly different between groups affected by severe malnutrition and normal children (p>0.05). This remarkable finding was evident across the span of dental development. We demonstrate that there is little measurable effect of sustained malnutrition on the average timing of tooth formation. This noteworthy finding supports the notion that teeth have substantial biological stability and are insulated from extreme nutritional conditions compared to other maturing body systems.

Interpreting group differences using Demirjian's dental maturity method

Although Demirjians method is designed to assess dental maturity at the individual level, significant differences between average dental age and real age for groups have been interpreted as population differences. The aim of this study was to describe the variation in maturity score for age and age for maturity score from a large collaborative database of children and discuss methods adapted for groups in light of this. Tooth stages from radiographs of 4710 males and 4661 females (age 2-18) were used and dental maturity scores calculated using Demirjian and Goldstein. The mean, standard deviation, standard error and 95% confidence intervals of maturity score by age group (6 and 12 months groups) and age by maturity score (5 points) groups were calculated. Adapted maturity curves from 13 published studies of boys from Europe, Middle East, Africa, India, China and South America were compared to the database. Most adapted curves at the 50th percentile from world regions fell within the 95% confidence intervals. Those that did not, were hampered by small sample size or poorly fitting curves. This is complicates by the inclusion of mature individuals. Few studies adapting Demirjians method provide sufficient or appropriate statistics to compare maturation of individual teeth. The wide 95% confidence intervals for maturity score by age, age by maturity score, age of individual tooth stages and large number of sequences suggest that the significant differences in dental maturity score do not reflect any biological difference in the timing of tooth formation stages at the population level. Demirjians dental maturity method is inappropriate to assess population differences in dental maturity and adapting scores for age or age for scores for different groups of children is probably unnecessary.

The assessment and interpretation of Demirjian, Goldstein and Tanner's dental maturity

Background: A frequently reported advancement in dental maturity compared with the 50th percentile of Demirjian, Goldstein and Tanner (1973, Hum Biol 45:211–27) has been interpreted as a population difference. Aim: To review the assessment and interpretation of Demirjian et al.s dental maturity. Subjects and methods: Dental maturity of boys from published reports was compared as maturity curves and difference to the 50th percentile in terms of chronological age and score. Dental maturity, as well as maturity of individual teeth, was compared in the fastest and slowest maturing groups of boys from the Chaillet database. Results: Maturity curves from published reports by age category were broadly similar and differences occurred at the steepest part of the curve. These reduced when expressed as score rather than age. Many studies report a higher than expected score for chronological age and the database contained more than expected children with scores>97th percentile. Revised scores for chronological age from this database were calculated (4072 males, 3958 females, aged 2.1–17.9). Conclusion: Most published reports were similar to the database smoothed maturity curve. This method of dental maturity is designed to assess maturity for a single child and is unsuitable to compare groups.