Interpreting group differences using Demirjian's dental maturity method

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Abstract

Although Demirjian's 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 [2]. 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 Demirjian's 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. Demirjian's 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.

Introduction

Demirjian's dental maturity method [1], [2], [3] is a useful tool to assess dental maturity for the individual child. Numerous researchers have applied this method to groups of children in various parts of the world and the significant differences between most groups and the reference have been interpreted as either a true population difference or a secular trend. Many authors have used this to justify the need for population specific dental maturity scores, however, there is growing evidence that this is probably unnecessary. The aim of this paper were to describe the variation in (1) dental maturity score by age groups and (2) age by maturity score categories using a large database [4], [5] and discuss the adapted scores for boys from published studies from different world regions in the light of this variation.

Section snippets

Materials and methods

The data were from a large collaborative database of cross-sectional, retrospective dental radiographs set up by Chaillet et al. of children of European origin in Australia, Belgium, Canada, England, Finland, France, and Sweden with a small group from South Korea [4]. Dental maturity and the variation in age of individual tooth stages have been documented [5], [6]. The sample for this study consisted of radiographic data of individuals aged 2–18 (N = 4710 males, N = 4661 females). For the first

Results

The variation of dental maturity score and age is illustrated in Fig. 1, Fig. 2, Fig. 3. Mean maturity score, standard deviation, standard error of mean and 95% confidence interval (CI) by 6-month and 1-year age groups is shown in Fig. 2, Fig. 3 and Table 1, Table 2. The age groups with the highest standard deviation are from 5 to 8 years of age in males and 4 to 7 in females. This corresponds to the section of the maturity curve with the steepest slope. For instance a boy aged from 7.00 to

Discussion

Demirjian's method is designed to assess the developing dentition of an individual child. The formation stages of the left mandibular teeth (excluding third molar) are assessed, the individual scores for each of the seven stages are summed and this is converted to a single dental age which represents the average age of a child for that score. The clinical interpretation of this indicates if the child is dentally advanced, average or delayed compared to the reference. It is clear from Fig. 1,

Conclusions

The numerous significant differences in Demirjian's dental maturity method in different groups, interpreted incorrectly as population differences, are at odds with the available evidence of the similarity in maturity of individual tooth formation stages between world groups. Possible explanations for differences in average dental age and known age using Demirjian's method include the weighted scores, complex equations and the inclusion of mature individuals. Demirjian's method remains a useful,

Acknowledgements

I am grateful to Nils Chaillet (CHU Sainte-Justine Research Centre, University of Montreal, Montreal, Quebec, Canada) who organised the collaboration for this database and to Marjatta Nyström, Hakan Mörnstad, Kian Rowlings, Jane Taylor, Guy Willems and their co-authors for sharing data. The views in this paper are my own and do not represent any of these collaborators.

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