analysis of 1202 orthopantograms ... - dental … · third molar were either missing due to...
TRANSCRIPT
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September 28, 2001 EUROPEAN JOURNAL OF MEDICAL RESEARCH
Eur J Med Res (2001) 6: 377-384
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ANALYSIS OF 1202 ORTHOPANTOGRAMS TO EVALUATE THE
POTENTIAL OF FORENSIC AGE DETERMINATION BASED ON THIRD MOLAR DEVELOPMENTAL STAGES
f•Gs B. Willershausen, N. Loffler, R. Schulze
Mainz, Germany So
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Abstract: A total of 1202 orthopantograms of young dental patients were analyzed to assess the correlation of third molar root development with chronological age. The investigated patients were treated at a university dental clinic on an outpa-tient basis, included a variety of demographic characteristics (600 males and 602 females, 28% of other than central European background), and were 15-24 years old when the radiographs were obtained. Radiographs in which more than one third molar were either missing due to agenesia or extraction, or not evaluable because of deep de-struction or marked tilting, were not included in the analysis. Our findings show that the growth patterns of third molars, based on seven defined stages of root development, did correlate with chronological age; age estimation when applied to a specific individual would involve a margin of error of ± 2-4 years. There were no significant differences between the left and right jaw seg-ments, but the stage of root development was gen-erally more advanced in the upper than in the lower third molars. Root development was also more advanced among boys than among girls of the same age. There were no apparent differences in growth patterns based on national/ethnic back-ground. While only 2.5% of 1.8-year-olds revealed fully developed third molars in all four quadrants, this percentage leaped to 38.4% among the 21-year-olds. To summarize, while the developmen-tal stage of third molars is not per se a highly use-ful indicator of chronological age in juveniles and young adults, it is nevertheless a valuable supple-mentary parameter given the scarcity of other available age indicators.
Key words: Develomental stages of third molars; chronological age
INTRODUCTION
The importance of determining the chronological age of juvenile offenders in the context of criminal proceedings has significantly increased in many European countries over the past few decades. This development reflects the growing influx of migrants into industrialized countries, which nat-
urally also involves greater numbers of foreign na-tionals for whom no clear documentation of age is available. Interest in determining the age of living persons, notably of adolescents for whom no birth records are available, is not a recent phe-nomenon but has a long history. In ancient Rome, for instance, adolescents were considered fit for military service as soon as their second molars had fully emerged [16].
An exemplary historical precedence of the use of tooth development as an indicator for chrono-logical age has been handed down from 19rh-centu-ry England [14]. English legislation at the time stipulated that children under seven were not pun-ishable for any crimes they committed. Since modern birth registers did not yet exist, it was often difficult to establish the age of children and thus protect them from punishment [17]. Age esti-mation was also important, however, in enforcing child labor regulations. In 1833, a strict ban was imposed on employing children under nine in spinning mills, and the working hours for up to 13-year-olds were limited to nine hours a day. As the only legal standard as to how the age of these children was to be determined, it was required that they should have the normal body strength and stature of a 9-year-old [13].
Today a number of criteria are available to de-termine the age of individuals [3, 9, 12, 18], usual-ly involving the expertise of radiologists, odontol-ogists or anthropologists [1]. If all medico-legal and ethical requirements are met, certain methods of age estimation are considered useful and are recommended [19]. The German Association of Forensic Odonto-Stomatology recommends phys-ical examination including anthropornetric meas-urements (body height - and weight, physique); evaluation of sexual maturity and any age-related developmental abnormalities; X-ray assessment of the left hand; as well as dental examination includ-ing dental status and radiography, usually in the form of orthopantography.
Age estimation based on tooth development mainly relies on patterns of tooth emergence and regularities in the transition from deciduous to permanent dentition. "Tooth age" has been postu-lated as an important criterion of physical matur-
378 EUROPEAN JOURNAL OF MEDICAL RESEARCH September 28, 2001
ity, as tooth development tends to be independent of environmental factors or systemic disease [16].
Helpful parameters in age estimation include mineralization processes of the crowns and roots of permanent teeth, anthropometric data in conjunc-tion with tabulated values, as well as the develop-ment of secondary sexual characteristics and of the apiphyseal/apophyseal joints. However, all of these growth processes will slow down over time, so that the parameters will become ever less accurate until they reach their definitive dimensions. Roughly speaking, in individuals who are past 25 all at-tempts at age estimation are doomed to failure [1].
In Germany there is a growing need for age esti-mation in juvenile offenders, the relevant age lim-its for criminal prosecution under German law being 14, 16, 18 and 21 years. S19 of the German Penal Code stipulates that individuals under 14 have no criminal responsibility. From that point on, two age categories are defined for juvenile of-fenders: those who, at the time of the offense, were 14 but not yet 18, and those who, at the time of the offense, were 18 but not yet 21 01,2 JGG). The provisions of juvenile criminal law are appli-cable if an individual who is between 14 and 18 years old commits an offense that is punishable under general regulations such as the German Penal Code or the Narcotics Act, or if an offender in the age range of 18-21, according to an overall personality assessment, had not passed the ethical and intellectual stage of the 14-18 range at the time of the offense, or if the offense, by the cir-cumstances or motives involved, was specifically juvenile in nature (§105 JGG).
MATERIALS AND METHODS
A total of 1202 orthopantograms (OPGs) of young male (n-600) and female (n=602) patients treated at a university dental clinic (Clinic and Policlinic for Dental, Oral and Jaw Pathologies at Johannes Gutenberg University, Mainz, Ger-many) on an outpatient basis were analyzed for the study. All patients were 15-24 years old when the OPG was made. Patient data included in the analysis were name, sex, date of birth, date of OPG, and nationality. The age of the patients was calculated from the date of OPG and the date of birth. The nationality was derived preferably from the OPG documentation or, wherever this was reasonable, from the name of the patient.
The radiographs were obtained using either a Siemens Orthophos 3 (208/230 V, max. 9 A) or a Siemens Orthophos CD (90 kV, 12 mA) system. OPGs in whom more than one third molar were agenetic or had been extracted were excluded. In addition, the third molars had to be positioned perpendicularly to the X-ray direction, i.e. teeth that were tilted in oral or vestibular direction were excluded.
The radiographs meeting these criteria were evaluated for the developmental progress of third molars based on a system by Kullxnan et al. [10] in which third molar root development is subdivided
into seven stages. Teeth hatwere not adequately evaluable due to deep destruction or marked tilt-ing were assigned stage "0". Kullman et al. origi-nally developed this staging system for mandibu-lar third molars but, for the purpose of the present study, we also used it for maxillary third molars. The seven stages are:
Stage 1 or Ri-R 1/4 Early root development; < 1/4 of expected de-finitive root length
Stage 2 or R1/4-R1/2 1/4 to 2/4 of expected definitive root length
Stage 3 or R1/2-R3/4 > 1/4 but < 3/4 of expected definitive root length
Stage 4 or R3/4-Rc > 3/4 but < 4/4 of expected definitive root length
Stage 5 or Rc-Aci Expected definitive root length reached, apical constriction yet to start
Stage 6 or Aci-Ac Apical constriction ongoing
Stage 7 or Ac Apex is closed, root development is complete
STATISTICAL ANALYSIS
Statistical data analysis was performed using SPSS for Windows (V 8.0) in collaboration with the Institute of Medical Statistics and Documentation at Johannes Gutenberg University, Mainz, Ger-many. Data were represented both as mean and as median values. The mean values calculated from the quantitative assessments were given with 95% confidence intervals_
RESULTS
In the present study, a total of 1202 OPGs of den-tal patients (male: n = 600, female: n = 602) were evaluated. They had been treated at a university clinic on an outpatient basis and were 15-24 years old when OPGs were made. Wherever the indica-tions of national and/or ethnic background were clear, patients were grouped into central Europeans, southern Europeans and Turks. The remaining cases (e.g. Asians, Africans or South Americans) were summarized in a separate group (Table 1). Turks as a separate category was a natu-ral choice since . people of Turkish background currently account for around 11% of the German population, so that a high percentage of patients at our clinic would also fall in this category.
Third molar growth patterns are illustrated in Figures 4-8 in the form of box and whisker plots for each quadrant. It is apparent that root devel-opment correlated with age in all third molars. The root mineralization process typically starts at age 15-16 (Fig. 1) and then continuously unfolds (Fig. 2) until the apex is completely closed and the root fully developed, which typically occurs at age 20-21 (Fig. 3).
Senternber 28, 2001 EUROPEAN JOURNAL OF MEDICAL RESEARCH 379
Table 1. Sex and national/ethnic distribution
males N
females N % N
total
Central European 405 33,7 460 38,3 865 77,0
Southern European 80 6,7 62 5,2 142 11,8
Turkish 77 6,4 43 3,6 120 10,0
other 38 3,2 37 3,1 75 6,2
Fig. 1. OPG of a 15.6-year-old girl of central European background.
Fig. 2. OPG of a 18.2-year-old girl of Turkish background.
Fig. 3. OPG of a 21-year-old woman of central European background.
26
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Thooth 18 - developmental stages
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380 EUROPEAN JOURNAL OF MEDICAL RESEARCH September 28, 2001
Fig. 4. Developmental stages of the right upper third molar (18) plotted against chronological age (in years) based on a sample of outpatients including both sexes.
Thooth 28 - developmental stages
Based on upper right third molars (Fig. 4) the mean age at stage Ri was 16.3 years, with lower and upper 95% confidence limits of 15.9 and 16.7 years, respectively. The youngest age at which mineralization was observed was 15.0 years, which is not a relevant finding as 15 years was the lower age limit for inclusion in the study. The oldest age at which mineralization was observed was 19.4 years, so that the overall span for stage Ri was 4.4 years. The mean age at stage R1/4 was 16.4 years, the 95% confidence interval being 16.3-17.1 years. The mean age at stage R3/4 was 17.4 years, the 95% confidence interval being 17.1-17.8 years, the total age range being 15.2-20.3 years (= span of 5.1 years). The defini-tive root length (stage Rc) was reached at a mean age of 18.0 years, the 95% confidence interval being 17.5-18.5 years, the total age range being 15.2-22.0 (= span of 6.8 years). The mean age at stage Aci was 18.4 years, the 95% confidence
Fig. 5. Developmental stages of the left upper third molar (28) plotted against chronological age (in years) based on a sample of outpatients including both sexes.
interval being 18.2-19.0 years. Apex closure was completed at a mean age of 21.0 years, the 95% confidence interval being 18.2-19.0 years, the total age range being 15.0-24.0 years (= span of 9 years).
The leap between growth stages Aci and Ac is due to the fact that the values for Ac are increas-ingly difficult to estimate, as there is no radio-graphic pattern to accurately define the point at which root development has been completed.
Comparative analysis of right and left third mo-lars did not reveal any statistically significant dif-ferences, i.e. the roots developed symmetrically. Nor do the box and whisker plots in Figures 4-8 reveal any marked differences between teeth 18 and 28 or between teeth 38 and 48.
The sex-specific distribution of growth patterns is outlined in Figure 8. Third molar roots started to develop earlier in life among the boys than among the girls: root mineralization of the maxil-
Fig. 6. Developmental stages of the left lower third molar (38) plotted against chronological age (in years) based on a sample of outpatients including both sexes.
Fig. 7. Developmental stages of the right lower third molar (48) plotted against chronological age (in years) based on a sample of outpatients including both sexes.
Fig. 8. Developmental stages of the right upper third molar (18) plotted against chronological age and sex distribution.
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Thooth 38 - developmental stages
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Thooth 18 - developmental stages
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September 28, 2001 EUROPEAN JOURNAL OF MEDICAL RESEARCH 381
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September 28,2001
EUROPEAN JOURNAL OF MEDICAL RESEARCH 381
Fig. 6. Developmental stages of the left lower third molar (38) plotted against chronological age (in years) based on a sample of outpatients including both sexes.
Fig. 7. Developmental stages of the right lower third molar (48) plotted against chronological age (in years) based on a sample of outpatients including both sexes.
Fig. 8. Developmental stages of the right upper third molar (18) plotted against chronological age and sex distribution.
26
16"
Ac1 Ac
382 EUROPEAN JOURNAL OF MEDICAL RESEARCH
September 28, 2001
Thooth 18 - developmental stages
lary third molars started 0.8 years earlier, the sub-sequent developmental stages started up to 1.4 years (R4/4) earlier. In overall terms, the boys were ahead of the girls by a mean of 0.7 years.
The population-specific distribution of growth patterns is outlined in figure 9 based on tooth 18. Ages are given as median (MED) and mean (MN) values to facilitate comparison of data. The num-ber of investigated patients (N) and standard devi-ations (SD) are also shown. For the sake of com-pleteness, age distributions for the southern. European and Turkish subsets as well as for the subset including "other" national/ethnic back-grounds are given as well, even though the case numbers involved are too small to generalize these data.
Adequate sample sizes for all groups are only available for stage Ac. It emerges that the root de-velopment of tooth 18 was first completed among the Turkish population (mean age: 20.6 years ± 2.1 SD), followed by "Other" (mean age: 20.7 years ± 2.0 SD). By comparison, the central European subpopulation (mean age: 20.9 years ± 1.9 SD) reached stage Ac 0.3 years later than the Turkish population and 0.2 years later than "Other". All in all, the age differences were so small that the root development of tooth 18 was completed around age 21, at a standard deviation of around 2 years, in all analyzed groups.
DISCUSSION
The purpose of the present study was to explore ways to identify the age limits for criminal prose-cution between 14 and 21 years based on radio-graphic assessment of third molar root develop-ment by analyzing a large number of orthopanto-grams on record for non-adult dental patients. In addition to breaking these patients up into male or female, they were also investigated against their national/ethnic backgrounds, considering that a
Fig. 9. Developmental stages of the right upper third molar (18) plotted against chronolical and population groups.
relatively high proportion of the German popula-tion are not of central European descent. This was true of 28% of analyzed patients, a percentage that reflects the demographics of 15-24-year-olds in the German population in a representative man-ner.
Our results demonstrate a pattern of third molar root development that is less uniform than in other teeth. Root calcification in the lower third molars started at a mean age of 16.0 years, which is well within the ranges given by other au-thors. By comparison, Johanson [8] reported a mean age at onset of third molar root develop-ment of 15.8 years, Levesque et al. [11] of 12.6-16.8 years, Nortje [17] of 16.5 years, and Thorson and Flagg [20] of 14.0 years. All those au-thors used different techniques of estimation and almost invariably confined their observations to the lower third molars.
According to our own findings, stage R1/4, where around one-fourth of the root of the third molar is calcified, was reached at a mean age of 16.9 years, compared to a mean of 17.5 years given by Nortje [17], 15.4 years by Thorson and Hagg [20], and 16.4 years by Loitz [1992]. Stage R1/2, where the root is mineralized over half of its ex-pected definitive length, was reached at a mean age of 17.2 years, compared to 17.2 years given by Harris and Nortje [7], 17.0 years by Thorson and Hagg [20], 16.9 years by Kullmann et al. [10], and 17.7 year by Mincer et al. [15].
Stage R3/4, where the root of the third molar is calcified over three-fourth of its expected defini-tive length, was reached at a mean age of 17.7 years, compared to 17.8 years given by Nortje [17], 17.8 years by Harris and Nortje [7] (based on two-thirds of the root), 17.9 years by Loitz [13], and 17.3 years by Kullman et al. [10].
Stage Rc, where the root has reached its defini-tive length while apical constriction has not yet begun, was reached at a mean age of 18.2 years,
September 28, 2001 EUROPEAN JOURNAL OF MEDICAL RESEARCH 383
compared to 18.5 years according to both Engstrom [2] and Harris and Nortje [7], while Loitz [13] gave a slightly different mean age of 19.7 years.
Stage Rc, where the root has reached its defini-tive length and apical constriction is ongoing, was reached at a mean age of 19.7 years, compared to 18.5 years according to Nortje [17], 19.2 years ac-cording to Kullmann et al. [10] and 21.3 years ac-cording to Loitz [13].
Stage Ac, where the apex is closed and root de-velopment thus completed, was reached at a mean age of 21.3 years, compared to 19.0 years accord-ing to both Engstrom [2] and Nortje [17], 19.2 years according to both Harris and Nortje [7] and Thorson and Fagg [20], 23.2 years according to Loitz [13], and 20.2 years according to Mincer et al. [15]. The reason for the especially great vari-ability of reported ages for this specific stage is that this result heavily depends on the age catego-ry of the analyzed population.
Our comparative analysis of maxillary versus mandibular third molars showed synchronous de-velopmental stages in 68% of cases. In 16% the maxillary third molars were one stage ahead, and in 6% they were two stages ahead_ The stage of root calcification (stage Ri) was often observed in the mandibular third molars before their maxil-lary counterparts entered this stage. In all subse-quent stages, the third molar roots generally de-veloped at a faster pace in the maxilla than in the mandible. These results indicate a longer phase of growth for mandibular than for maxillary third molars,
Regarding the sex distribution, our results indi-cate a delayed development of both the upper and lower third molars in girls as compared to boys by a mean of 0.7 years.
Whether the various national/ethnic groups in-cluded in our study were characterized by differ-ent growth patterns could not be clearly an-swered, since the southern European, Turkish and "Other" subsets were too small to address this question. A sufficient number of cases were only available for stage Ac (marking the final stage of third molar root development), according to which the root development in tooth 18 was com-pleted first among the Turkish population (mean age: 20.6 years) and last among the southern European population (21.1 years), the central European and "Other" populations taking an intermediate position. The fact that the process of third molar development was completed within half a year in all patients suggests that there are no significant developmental differences between the national/demographic groups investigated.
Most previous investigators either did not in-vestigate different population groups, or they ne-glected any observed differences in growth pat-terns because their sample sizes were too small. Garn et al. [4], Harris et al. [6] and Gravely [5]re-ported noticeable differences in third molar devel-opment between black and white Americans. Both groups found that the third molars of black
Americans developed and emerged faster than chose of white Americans. Mincer et al, [15] did could not confirm these results but attributed their failure to observe differences in third molar growth between black and white Americans to the small sample size.
Both our own results and the findings reported by other authors point to a number of factors to be considered because they may otherwise distort the results of age estimation based on radiographic assessment of third molar development. As the single most important of these factors, third mo-lars show a less uniform growth pattern than all other teeth. The growth variability in the various stages of third molar development considerably adds to the difficulty of age estimation. Mincer et al. [15] suggested that the estimated age would al-ways be within 4.8 years of the actual age after ap-plying the 95% confidence interval. In our own study, the estimated and actual ages were not more than 1.1 years apart after applying the 95% confidence interval, while the overall variability including all outliers was substantially higher. Therefore the presented approach to age estima-tion can only perform in a satisfactory manner when additional parameters are used. In order to obtain more accurate results, the upper and lower third molars should be assessed on a separate basis, and the sex factor should also be included.
To summarize, age estimation in non-adults based on third molar development is only a realis-tic option when it is embedded in a broader con-text. Obviously enough, hoWever, the main rea-son why this parameter is used after all lies in. the scarcity of alternative methods to determine the age of individuals in this age category.
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Received: July 2, 2001 /Accepted: September 6, 2001
Address for correspondence: Prof. Dr. Dr. Brita Willershausen Clinic for Restorative Dentistry Dr. R. Schulze Dep. of Oral Surgery Augustusplatz 2 55131 Mainz Tel. 06131/177246 Fax 06131/173406 e-mail willersh©mail.uni-mainz.de