Dental maturity was studied with 9577 dental panoramic tomograms of healthy subjects from 8 countries, aged between 2 and 25 years of age. Demirjian's method based on 7 teeth was used for determining dental maturity scores, establishing gender-specific tables of maturity scores and development graphs. The aim of this study was to give dental maturity standards when the ethnic origin is unknown and to compare the efficiency and applicability of this method to forensic sciences and dental clinicians. The second aim was to compare the dental maturity of these different populations. We noted an high efficiency for International Demirjian's method at 99%CI (0.85% of misclassified and a mean accuracy between 2 to 18 years ± 2.15 years), which makes it useful for forensic purposes. Nevertheless, this international method is less accurate than Demirjian's method developed for a specific country, because of the inter-ethnic variability obtained by the addition of 8 countries in the dental database. There are inter-ethnic differences classified in three major groups. Australians have the fastest dental maturation and Koreans have the slowest.

Dental maturity was studied from 2213 dental panoramic radiographs of healthy ethnic Finns from southern Finland, aged between 2 and 19 years. The aim was to provide new Finnish maturity tables and curves and to compare the efficiency of Demirjian's method when differently weighted scores and polynomial regressions are used. The inter-ethnic variations lead us to calculate specific Finnish weighted scores. Demirjian's method gives maturity score as a function of age and seems better adapted for clinicians because, in their case, the maturity score is unknown. Polynomial functions give age as a function of maturity score and are statically adapted for age estimation studies. Finnish dental maturity tables and development curves are given for Demirjian's method and for polynomial functions. Sexual dimorphism is established for the same weighted score for girls and boys, and girls present a greater maturity than boys for all of age groups. Polynomial functions are highly reliable (0.19% of misclassifies) and the percentile method, using Finnish weighted scores, is very accurate (±1.95 years on average, between 2 and 18 years of age). This suggests that polynomial functions are most useful in forensic sciences, while Demirjian's method is most useful for dental health clinicians.

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 Demirjian's dental maturity method.

Summary:Chemo-and radiotherapy may have injurious effects on developing teeth. In this long-term follow-up study among poor-risk neuroblastoma (NBL) survivors our aims were: (1) to assess both the type and extent of the side-effects of the anticancer treatment on tooth development; and (2) to develop an index for expressing total damage to the permanent dentition. We studied the dental development from panoramic radiographs (PRG) of 18 long-term survivors treated under the age of 6 years with high-dose (HD) chemotherapy and autologous stem cell transplantation (ASCT) for poor-risk NBL. The myeloablative therapy was either HD chemotherapy and fractionated total body irradiation (TBI) of 10-12 Gy (TBI group, n = 10) or HD chemotherapy only (non-TBI group, n = 8). A defect index (DeI) was developed to describe the damage to the permanent dentition. The DeI was also tested in 18 healthy adolescents. All NBL patients had disturbances in dental development including short roots, arrested root development, microdontia and tooth aplasia. After TBI, 9/10 patients had very severe root defects, in contrast to none in the non-TBI group. All children in the TBI group had 2-12 (mean 6.6) missing permanent teeth, while 2/5 in the non-TBI group (3/8 excluded due to young age) had two and four missing permanent teeth, respectively. Microdontia was found at equal frequency in both groups. The mean value of the DeI was 70.0 (range 28-117) in the TBI group, 15.2 (range 4-34) in the non-TBI group (P Ͻ 0.001, Mann-Whitney U test) and 1.8 (range 0-15) in healthy adolescents. Disturbances in dental development may compromise occlusal function in poor-risk NBL patients after ASCT, especially when TBI is included in the conditioning regimen. Long-term dental follow-up and rehabilitation is required.

Overall dental maturity was studied semilongitudinally in a group of 248 healthy children born in Helsinki in 1968-73. In all, 738 orthopantomograms were taken of these children at ages of 2.5-16.5 years. Overall dental maturity was estimated by the method of Demirjian and Goldstein, which is based on the development of seven left mandibular permanent teeth. The aim of the study was to construct dental maturity curves for Finnish children and to compare their dental maturity with that of French-Canadian children studied by the same method. The Finnish children were more advanced in dental maturation than French-Canadian children (p less than 0.01). In boys the advancement was seen at the age of 5-10 years and in girls at the age of 4-12 years. These findings suggest differences in overall dental maturity among white population groups.

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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.

Development of teeth was studied from 2483 dental panoramic tomograms of 1651 healthy Finns ranging in age from 2 to 25 years. Dental maturity was assessed using a method based on developmental stages of 7 left mandibular teeth. We give sex-specific tables of maturity scores as a function of ages and of ages as a function of maturity scores. Also generated are percentile graphs for visual evaluations of dental maturity in children and adolescents. Since maturity scales do not tolerate any missing data, a great limitation for their use, we have developed linear regression models for predicting the formation stages of each of the 7 mandibular teeth. It was easiest to predict the formation stage of the mandibular first molars (correct in 87% within the study material) and most difficult to predict second molars and second premolars (correct in 69% and 70%, respectively). We expect the data and formulae presented in this study to prove useful in research and in clinical and forensic dentistry.