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Dental Age Estimation in Living Individuals

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By: Andreas Olze, DDS, PhD; Bruce R. Pynn, DDS, MSc, FRCD(C), FICD and Andreas Schmeling, MD, MA, PhD
2008-11-01

Even in ancient times, age estimations of living adolescents were considered important. According to records in Ancient Rome adolescents were judged to be fit for service, as soon as the second molars had erupted completely (Müller 1990). In England a regulation from the year 1883 outlawed the employment of children less than nine years of age in spinning mills and restricted the working hours of children between nine and 13 years to nine hours a day (Loitz 1992). At that time the minimum age of criminal responsibility was seven years (Nortje 1983). It was mainly dentists who had to carry out age estimations. At a conference of the Munich Medical Society on April 1st, 1896, only one year after the discovery of X-rays, von Ranke came up with the idea that the age of children could also be examined with the help of an X-ray of the hand (Fendel 1976).

In those days the Polish court pianist Raoul Koczalski, who is said to have already given public concerts when he was only four years old and who had caused a sensation in Munich as a wunderkind, gave a performance in Munich. Von Ranke mistrusted the young court pianist and suspected that he was older than he had pretended. However, it is not known, if von Ranke verified his suspicion with an X-ray examination. A study of the ossification of the human hand published by Behrendsen in 1897 was followed in 1909 by a publication of the American pediatrician Rotch, who believed that it is possible to estimate a child's readiness for school using the roentgenologic skeletal age assessment. There is a great time interval between these early publications and the systematic examinations about the time course of the ossification of the hand. The most famous are the publications of Greulich and Pyle (1959), Schmid and Moll (1960) as well as Tanner et al (1975; 2001). However, these atlases of radiographic anatomy were mainly used to diagnose disorders in skeletal maturity and not to estimate the chronological age of an individual.

The reason for the increasing importance of forensic age estimation of living individuals today is cross-border migration, which led to an increasing rate of foreigners giving doubtful details about their age in numerous countries. The persons to whom forensic examination is to be applied are foreigners without valid identity documents who are suspected of making false statements about their age and whose genuine age needs to be ascertained in the course of criminal, civil, asylum or old-age pension proceedings (Schmeling et al. 2001). In many countries, the age thresholds relevant for criminal, civil, and asylum proceedings lie between 14 and 22 years of age.

According to the recommendations of the Study Group on Forensic Age Diagnostics (http://rechtsmedizin.klinikum.uni-muenster.de/agfad/index. htm), forensic age estimates in living subjects for purposes of medical jurisprudence should be based on the combined examination findings in three independent development systems. Physical maturity is thereby assessed based on an appraisal of anthropometric parameters, secondary sexual characteristics and relevant age-related developmental disorders. Dental development is assessed by means of a dental examination, which should include an inspection of the oral cavity and an analysis of an orthopantomogram. Skeletal maturity is evaluated by radiological analysis of the left hand. If the skeletal development of the hand is completed, a conventional radiological or computer tomographic examination of the clavicles should additionally be performed to augment the analytical spectrum (Schmeling et al. 2008).

The main criteria for dental age estimation in the relevant age group are eruption and mineralization of third molars.

Wisdom tooth eruption

Tooth eruption is a parameter of developmental morphology which, unlike tooth mineralization, can be determined in two ways: by clinical examination and/or by evaluation of dental X-rays. In the cases of teeth 1 to 7 (according to the FDI World Dental Federation notation), there is sufficient data on the emergence sequences of the permanent dentition to obtain reliable forensic age estimations in children and early adolescents (Wedl et al. 2002).

Only a few comparison studies on wisdom tooth eruption have been published so far, and these studies are limited to gingival eruption. Fanning (1962) investigated gingival third molar emergence in American white males (n=2370) and females (n=1053) from the Boston area (age: 13 to 22 years) and compared the data with that from a black African population described by Chagula (1960). The Americans' upper wisdom teeth emerged at a mean age of 20.5 years in both males and females, and the lower wisdom teeth emerged at mean ages of 19.8 years in males and 20.4 years in females. According to the figures published by Chagula (1960), dental development in Africans is faster: their upper and lower wisdom tooth erupted at the ages of 13-16 and 17-20 years, respectively, which is 2.5 and 1.25 years earlier than in their white American counterparts.

Similarly, Garn et al. (1972), who investigated the eruption of permanent teeth in 953 black and 998 white Americans, found that upper wisdom teeth of black Americans emerged 3.7 years earlier and lower wisdom teeth 5.6 years earlier than in white Americans. In a review of the literature on growth and development in Japan, Kimura (1984) provided Japanese statistics on third molar emergence (mean age: 19.8 years in males and 21.0 years in females). After comparing his data with that of Fanning (1962) for white North Americans, Kimura concluded that the figures are in close agreement. Hassanali (1985) compared third molar eruption in 1343 Africans and 1092 Asians from Kenya. In the African subjects, the lower wisdom teeth emerged at a mean age of 17.6-18.3 years, and the upper wisdom teeth at 18.5-18.9 years. The corresponding ages in the Asian subjects were 19.9-20.3 years for the lower wisdom teeth and 20.7-21.0 years for the upper wisdom teeth. Accordingly, dental development in the African Kenyans occurred roughly two to three years faster. Hassanali therefore concluded that wisdom tooth eruption began at the age of 13 in the investigated African subjects, and that all four wisdom teeth had erupted in 50 percent of these subjects had by the age of 18.5 years. In the investigated Asian subjects, on the other hand, wisdom tooth eruption began at the age of 15, and all four wisdom teeth had erupted in 50 % of the group by the age of 21.5 years.

Olze et al. (2007) defined a stage classification of third molar eruption based on evidence from conventional orthopantomograms (Fig. 1):

Stage A: Occlusal plane covered with alveolar bone.

Stage B: Alveolar emergence; complete resorption of alveolar bone over occlusal plane.

Stage C: Gingival emergence; penetration of gingiva by at least one dental cusp.

Stage D: Complete emergence in occlusal plane.

Olze et al. (2007) analyzed and compared the chronological course of wisdom tooth eruption in German, Japanese, and South African populations, respectively. They found that the investigated German population has an intermediate rate of dental development as determined by comparing the different ages of third molar eruption. The defined eruption stages occurred at earlier ages in the investigated South African population, and at later ages in the Japanese population. Statistically significant population differences were observed in males at stages A and B. The South African males were a mean 3.0-3.2 years younger than the German males at these stages of development, and the Japanese males were a mean 3.1-4.2 years older than their South African counterparts (Fig. 2). The females exhibited statistically significant population differences at stages A, B and C. The South African women reached the target stages a mean 1.6-1.8 years earlier than the German women, whereas the Japanese women were a mean 0.9-3.3 years older than their German counterparts (Fig. 3). It was concluded that population-specific reference data should be used when evaluating wisdom tooth eruption for the purpose of forensic age estimation.

Wisdom tooth mineralization

Various classifications have been devised for evaluating tooth mineralization (Gleiser and Hunt 1955, Nolla 1960, Haavikko 1970, Liliequist and Lundberg 1971, Demirjian et al. 1973, Gustafson and Koch 1974, Nortje 1983, Harris and Nortje 1984, Kullman et al. 1992 and Köhler et al. 1994). They differ with regard to the number of stages, the definition of each stage and the presentation. Since the validity of an age estimate depends crucially on the classification method used, practitioners should select the most appropriate one. Olze et al. (2005) assessed the validity of five basic types of classification. They selected the methods by Gleiser and Hunt (1955), Demirjian et al. (1973), Gustafson and Koch (1974), Harris and Nortje (1984) and Kullman et al. (1992). Of these methods the most accurate results were obtained with Demirjian's classification system (Fig. 4):

Stage A: Cusp tips are mineralized but have not yet coalesced.

Stage B: Mineralized cusps are united so the mature coronal morphology is well-defined.

Stage C: The crown is about half formed; the pulp chamber is evident and dentinal deposition is occuring.

Stage D: Crown formation is complete to the dentinoenamel junction. The pulp chamber has a trapezoidal form.

Stage E: Formation of the inter-radicular bifurcation has begun. Root length is less than the crown length.

Stage F: Root length is at least as great as crown length. Roots have funnel-shaped endings.

Stage G: Root walls are parallel, but apices remain open.

Stage H: Apical ends of the roots are completely closed, and the periodontal membrane has a uniform width around the root.

Demirjian's classification performed best not only for observer agreement but also for the correlation between estimated and true age. It is argued that this is due to the fact that Demirjian's classification is based on a sufficient number of stages which are defined independently of speculative es timations of length. This leads to the conclusion that the method devised by Demirjian should be used for evaluating the mineralization of third molars for purposes of forensic age determination.

One question of major practical relevance to estimating age from a dental view is whether the reference data customarily used for forensic diagnosis, derived from white North Americans on the one hand and Central and Northern Europeans on the other, can also be applied to members of other ethnic groups.

Few comparative studies are available on the subject of wisdom tooth mineralization. Gorgani et al. (1990) examined 229 black and 221 white US citizens aged 6-14 years. Among the black subjects crown mineralization of the third molars was completed 1 year earlier. Harris and McKee (1990) studied 655 white and 335 black US citizens aged 3.5-13 years. Whereas the black subjects reached the earlier stages of wisdom tooth mineralization about one year earlier, the gap appeared to narrow for later stages. This trend is confirmed by the work of Mincer et al. (1993). They examined 823 US citizens (80% white, 19% black) aged 14-25 years but did not establish any significant differences in the time frame for wisdom tooth mineralization. Daito et al. (1992) addressed wisdom tooth mineralization in 9111 Japanese youngsters aged 7-16 years and compared their data with the values provided by Gravely (1965), Rantanen (1967) and Haavikko (1970) for Caucasoid populations. No significant differences were discovered. These studies only lend themselves to limited comparison due to small sample sizes, varying methods and assessment by different observers. A further problem lies in the fact that the age data for subjects of black African origin often was not verified. Moreover, most available studies focus on the earlier stages of mineralization.

A comparative study of wisdom tooth mineralization (Olze et al. 2004) was carried out on three population samples: one German, one Japanese and one South African. To this end, 3652 conventional orthopantomograms were evaluated on the basis of Demirjian's stages. Statistically significant differences between the samples investigated were established for the age at which stages D-G of third molar mineralization were achieved. Significant differences between German and Japanese males were noted for stages D-G of mineralization (Fig. 5). Significant differences between Japanese and German females were observed for stages D-F (Fig. 6). According to these findings, Japanese males and females were approx. 1-2 years older than their German counterparts when they reached stages DF. Significant age differences between South African and German males applied to stages D-E. Significant age differences between South African and German females were observed for stages E and G. The South African subjects were approx. 1-2 years younger than the German subjects upon achieving these stages of mineralization. Significant age differences between the South African and Japanese samples were ascertained for both genders at stages D-G. The South African subjects were approx. 1-4 years younger than the Japanese subjects upon reaching these stages.

The population differences observed here may be due to differences in palatal dimensions between the ethnic groups surveyed. The largest palatal dimensions are observed in Africans and the smallest in Mongoloids, with Caucasoids assuming the middle rank (Byers et al. 1997). Inadequate space in the maxillary crest causes delay in wisdom tooth eruption, if not retention (Fanning 1962). In turn, retained wisdom teeth mineralize later than teeth whose eruption has not been impeded (Köhler et al. 1994). This would explain why Caucasoid populations occupy the middle position in relative terms when it comes to wisdom tooth mineralization, while Mongoloid populations display a comparative delay and African populations a relative acceleration.

Conclusions

All forensic age estimates should be based on the findings of a physical examination, an X-ray of the left hand, and a dental examination including dentition status and orthopantomogram evaluation. If the skeletal development of the hand is completed, a conventional radiological or computer tomographic examination of the clavicles should additionally be performed to augment the analytical spectrum.

The main criteria for dental age estimation in the relevant age group are eruption and mineralization of third molars.

For the assessment of third molar mineralization Demirjian's stage classification should be used.

Because of ethnic differences in the time course of eruption and mineralization of third molars the use of population-specific reference data is recommended for dental age estimations.

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Dr. Olze, Institute of Legal Medicine, Berlin, Germany.

Dr. Schmeling is a Forensic Pathologist, Institute of Legal Medicine, Münster, Germany.

Bruce R. Pynn practices oral and maxillofacial surgery and maintains a private practice in Thunder Bay, ON. He is on staff at Thunder Bay Regional Health Services Centre.

Oral Health welcomes this original article.

References

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In many countries, the age thresholds relevant for criminal, civil, and asylum proceedings lie between 14 and 22 years of age

Photos

Figure 1--Stages of wisdom tooth eruption.
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Caption: Figure 1--Stages of wisdom tooth eruption.
Figure 2--Boxplots for the time course of wisdom tooth eruption for males (tooth 18).
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Caption: Figure 2--Boxplots for the time course of wisdom tooth ...
Figure 3--Boxplots for the time course of wisdom tooth eruption for females (tooth 18).
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Caption: Figure 3--Boxplots for the time course of wisdom tooth ...
Figure 4--Demirjian's stages of wisdom tooth mineralization.
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Caption: Figure 4--Demirjian's stages of wisdom tooth mineraliza...
Figure 5--Boxplots for the time course of wisdom tooth mineralization for males (tooth 48).
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Caption: Figure 5--Boxplots for the time course of wisdom tooth ...
Figure 6--Boxplots for the time course of wisdom tooth mineralization for females (tooth 48).
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File size: 33.8 KB (300px X 219px)
Caption: Figure 6--Boxplots for the time course of wisdom tooth ...




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