ORIGINAL ARTICLE

Age estimation from fetus and infant toothand head measurements

Rukiye Dagalp & P. Sema Aka & Nergis Canturk &

Ipek Kedici

Received: 18 July 2013 /Accepted: 22 October 2013# Springer-Verlag Berlin Heidelberg 2013

Abstract Forensic identification comprises legal, social, eth-ical, and religious aspects where age detection is an importantfactor. When the case is a fetus or infant, recording variousmeasurements of the body, head, and teeth is essential. Theaim of this research is to evaluate the effects of different toothand body measurements and their implications on the ageestimation of fetuses and infants. This research was performedon 96 fetus and infant incisor teeth taken from 24 autopsycases (54 % males and 46 % females) where age of thesubjects were within the range of prenatal 16 weeks to post-natal 72 weeks. The data were statistically processed byregression analysis via curve estimations. According to theresults, growing patterns of the head circumference (HC) andthe upper central tooth measurements indicate a strong rela-tionship, where there is no significant difference for bothsexes. The growth patterns of all variables showed a linear

function to a certain age (approximately 56 weeks pre–pluspostnatal); the tooth height (TH) slightly increases until theclosure of the root apex, and the HC gradually stabilizes intime, therefore a log-linear relation was found considerable.The results revealed eight age estimation formulas, includingthe combination of HC with the labiolingual, mesiodistal(MD), crown height, and TH measurements. Among these,only MD can be applied to a living. In conclusion, tooth andhead measurements are found to be the main factors of ageestimation formulas.

Keywords Fetus teeth . Infant teeth . Human identification .

Age estimation . Forensic odontology

Introduction

Forensic identification is one of the most significant legalissues of the forensic sciences which is a basic right for aliving or a deceased individual without distinction of any kindand is required with regards to human rights, social, ethical,and religious aspects. Due to the universal declaration state-ment of human rights stating that “All human beings are equalbefore the law and are entitled without any discrimination toequal protection of the law,” it is also important to determinethe fetus' rights [1]. At that rate, it should be known if the bodywas viable at the time of birth. The inspection of viability mustindicate whether birth has occurred within the normal gesta-tional period and if the body is mature enough to live biolog-ically out of the uterus. It is imperative to determine if the fetuswas deceased at the time of birth or died afterward. For thispurpose, records of various head and body measurements aregenerally required during the examination of live individualsor the autopsy procedures which should be compared with thereference tables [2–7]. Age estimation is the most importantfactor of identification requiring attentive analysis where

Oral presentation presented at the 9th Anatolian Forensic ScienceCongress, 6–8 Nov. 2012 held in Zonguldak, Turkey.

R. DagalpDepartment of Statistics, Faculty of Science, University of Ankara,Ankara, Turkeye-mail: rukiyedagalp@gmail.com

P. S. AkaDepartment of Prosthodontics and Unit of Forensic Odontology,Faculty of Dentistry, University of Ankara, Angora Caddesi,Beysu-Park Sitesi, 2. Yamaç evler, C-Blok 215/1 Çayyolu,06800 Ankara, Turkeye-mail: akasema@gmail.com

N. Canturk (*)Department of Criminalistics, Institute of Forensic Sciences,University of Ankara, Ankara, Turkeye-mail: nergiscanturk@yahoo.com

I. KediciInternational Business, University of Birmingham, Finanskent Sitesi,A2 Blok, No: 37, Alibeyköy Eyüp, Istanbul, Turkeye-mail: ipek_kedici@hotmail.com

Int J Legal MedDOI 10.1007/s00414-013-0935-3

current research has been conducted. However, literaturediscussing the fetus and infant age group is rare. Some re-searches compare skeletal age to dental age, which focuses onbone and dental age estimation [8, 9]. The human fetal agewas studied from the direct measurements of femur and inci-sor teeth, and strong correlations were found between fetalage, femoral, and teeth measurements [10, 11]. Forensic med-ical experts, obstetricians, and pediatricians generally usehead circumference (HC) measurement as an age estimationparameter [12–17]. The maturation of an infant head resultsfrom the changes which occur in the size, shape, and positionof the cranial bones and shows maximum linear increase untilthe end of first 3 years of age. Then it continues with a slowrate up to adolescence, which can be seen in the growth tablesand curves of the cited references [18–21]. During the fetusand infant period, teeth are also indicators of age, whichdevelops within the sockets of the alveolar bones in the upperand lower jaws. The crown and root size of the teeth developlinearly to a certain time, starting from the initiation of themineralization phase until the completion of the hard tissuesdue to the incremental deposition process of dentinal, enamel,and cementum matrices with certain rates. The completion oftooth growth for crowns of deciduous central incisors is 2–4 months after birth and for roots including the apex closure is

1–2 years [22–26]. In cases where fetal and newborn infantileteeth are present as evidences even the skull is disintegrateddue to decomposition, then measuring the teeth and the appli-cation of fetus- and infant-specific dental age estimation for-mula where age is correlated with all tooth dimensions of thedeciduous teeth will be beneficial to find the age of theindividual [27].

The aim of this research is to correlate all tooth dimensionswith the HC measurement of fetuses or infants to find outwhich parameter affects the age most and to propose new ageformula including headmeasurement and all tooth dimensionsto estimate the age of an unidentified fetus or infant case.

Method and materials

This research was performed as a pilot study on a total of 96developing (maxillary and mandibular) deciduous central in-cisors which were isolated from 24 fetus and infant autopsycases [n =13 (54 %) males and n =11 (46 %) females] andexamined under the legal and ethical permission of the Coun-cil of Forensic Medicine, Ministry of Justice (number anddate: B.03.1.ATK.0.01.00. 08/237, 30 May 2006) and Ethic

Table 1 Descriptive statistics of the age (in weeks) due to sex

Gender Malecases

Femalecases

Total

n =13(54 %)

n =11(46 %)

n =24(100 %)

Pre-/postnatal Pre Post Pre Post Pre Post

Number of teeth 6 20 4 18 10 38

Percentage of teeth 15 85 27 73 21 79

Minimum age (in weeks) 16 0.14 16 0.14 16 0.14

Maximum age (in weeks) 40 52 40 72 40 72

Fig. 1 LL width measured on the maximum dimension between thelabial and lingual surfaces and on the midsagittal location of thecemento-enamel junction

Fig. 2 MD width which is the maximum dimension between the mesialand distal surfaces

Fig. 3 CH which is the maximum measurement from incisal edge tocervical on the mid-sagittal line

Int J Legal Med

Committee of University of Ankara, Turkey (number anddate: 103-2692, 4 December 2006). The autopsies were per-formed at the Council of Forensic Medicine, Ankara GroupPresidency Morgue Department. The subjects of this researchwere healthy fetuses and infants whose manner of death wastraumatic as a result of traffic accidents or death of pregnantmother from stab or gunshot wounds. No pathological signscausing developmental defect or systemic disease were iden-tified. The gestation and/or birth times of each case examinedwere known [n =5 cases (21 %) prenatal fetus; n =19 cases(79 %) postnatal infant]. Ages of the subjects were within therange of 16 prenatal weeks to 72 postnatal weeks. Descriptivestatistics of the age (in weeks) due to sex is given in Table 1.

In this research, the HC and deciduous central teeth mea-surements of the subjects were taken, among which, HC wasdetermined by the circular measurement passing over theglabella and the external occipital protuberance with a non-elastic metric tape in centimeters [2] and the tooth dimensions;labiolingual (LL), mesiodistal (MD), crown height (CH), androot height (RH) were taken in millimeters as follows: LLwidth, which is measured on the maximum dimension be-tween the labial and lingual surfaces and on the midsagittallocation of the cementoenamel junction (Fig. 1); MD width,which is the maximum dimension between the mesial and

distal surfaces (Fig. 2); CH, which is the maximum measure-ment from incisal edge to cervical on the midsagittal line(Fig. 3); and RH between the cervical line and the edge ofthe developing root on the midsagittal line of the labial rootsurface (Fig. 4). All four dimensions were taken with a digitalVernier compass (Mitutoyo 7117057, Japan). Additionally,CH and the RH were added to find the total tooth height(TH), [TH=CH+RH] (Fig. 5). Initially, two nonmeasurablecases were excludedwhichwere due to the beginning phase oftooth mineralization and to increase the reliability of the study;the data was produced from the arithmetical average of therepeated HC and tooth measurements of the cases.

The units of the measurements were not converted, as instatistical analysis correlation coefficient has not been affectedby the units. The data were processed by the computerizedstatistic program SPSS (Statistical Package for the Social Sci-ences) 16.0 software and statistically log-linear regression andcorrelation analysis were used to find the relation between theage with the head and tooth measurements. In addition to theeffects of head and toothmeasurements mentioned above, theirimplications on age were also statistically evaluated by regres-sion analysis. Log-linear combinations of the variables wereexamined to predict the age. Variables providing the highestcorrelation with age were chosen to produce the best models.

Results

The results of the statistical analyses showed that the bestmodels for age estimation were related with the head and thetooth dimensions according to R2 (The coefficient of determi-nation is the proportion of variability in the age which wasaccounted for the statistical regression model with the relateddimensions). In the case where all tooth dimensions were

Fig. 4 RH between the cervical line and the edge of the developing rooton the mid-sagittal line of the labial root surface

Fig. 5 CH and the RH were added to find the total tooth height

Age in weeks12010080604020

Hea

d C

ircu

mfe

ren

ce in

cm

50

45

40

35

30

25

Fig. 6 The growth pattern of HC with age (p <0.001) and the inversemodel [1/age=0.068−0.001 HC] (R2=0.988)

Int J Legal Med

correlated with the HC dimension, the best results were ob-tained between upper tooth values, which were found effectivefor age estimation and used for the statistical analysis with HC.

The growing pattern of the HC showed a linear feature atthe initiation phase which turns to a curve due to the slowing ofthe growth rate. The growth pattern of HC according to ageincluding the pre- and postnatal periods is determined with theregression model for age estimation according to HC andfound to be in a log-linear relation where:[Log (age)=2.046+0.05 HC], (p <0.001), R2=0.97 or can also be explained withan inverse model [1/age=0.068−0.001 HC] (p <0.001), whereR2=0.988 which is seen in Fig. 6.

The relation of age with all types of combinations of HCand tooth dimensions was analyzed according to sex; howev-er, no remarkable statistical difference was found except theinitial mineralization phase of the tooth germs where thefemales initiate slightly earlier (p >0.05).

When the correlation values between age and tooth mea-surements were examined, MD, LL, CH, and TH values werefound more significant than other tooth dimensions and theregression models were found for these variables. These re-sults and the log-linear regression formula are given in Table 2;their R2 and error variability (S2) values are shown in Table 3.The growth patterns of these tooth measurements are shown inFigs. 7, 8, and 9.

It is evident that tooth growth seems linear in all directionsto a certain age (approximately 56 weeks pre–plus postnatalwhich means 4 months postnatal) similar to the head growthpattern for the same age group. When compared to all toothmeasurements, HC shows a more concordant growth formwith TH shown in Fig. 10. A pairwise relationship betweenvariables is also shown as a scatter matrix in Fig. 11. Ageestimation applications on randomly selected reference mea-surements, using eight age estimation formulae, which areseen in Table 2, are given in Table 4.

Discussion

In forensic medical practice, the age of a fetus or an infant canbe calculated from various methods. Fetus age can be com-puted during pregnancy from the first day of the last menstru-ation period if known, which may be uncertain because ofmenstrual irregularity or calendar errors [28–30]. Estimationof fetus age can also be determined from the prenatal ultra-sound records (US), which is a hypothetical method, wherethe measurements of an image in two dimensions are convert-ed to three-dimension measurements. Generally, head circum-ference, birth weight, and length are commonly used param-eters for age estimation and growth assessment of newborn

Table 2 Regression formulas of age with tooth variables LL, MD, CH, TH, and HC

Formulas Tooth variables Age estimation regression formulas

Age 1 LL Log (age)=2.149+0.051×HC−0.154×LL+0.003×HC×LLAge 2 MD Log (age)=2.178+0.049×HC−0.104×MD+0.002×HC×MD

Age 3 CH Log (age)=2.25+0.039×HC−0.066×CH+0.003×HC×CH

Age 4 TH Log (age)=2.235+0.031×HC+0.071×TH

Age 5 LL, MD Log (age)=2.057+0.057×HC−0.417×LL+0.197×MD+0.013×HC×LL−0.008×HC×MD

Age 6 LL, CH Log (age)=2.087+0.05×HC−0.326×LL+0.156×CH+0.008×HC×LL−0.004×HC×CHAge 7 MD, CH Log (age)=2.061+0.052×HC−0.63×MD+0.559×CH+0.017×HC×MD−0.016×HC×CHAge 8 MD, TH Log (age)=2.177+0.037×HC+0.052×MD+0.02×TH−0.002×HC×MD+0.001×HC×TH

Table 3 Regression values forage estimation formulas Formulas Selected variables R2 S2 Standard error of

predicted valueError of log (age) estimationin weeks (with 95 % confidence)

1 HC, LL 0.984 0.006 0.00537 ±0.0105

2 HC, MD 0.981 0.007 0.00639 ±0.0125

3 HC, CH 0.979 0.008 0.00689 ±0.0135

4 HC, TH 0.993 0.002 0.00370 ±0.0073

5 HC, LL, MD 0.986 0.005 0.00715 ±0.0140

6 HC, LL, CH 0.987 0.005 0.00791 ±0.0155

7 HC, MD, CH 0.990 0.004 0.00575 ±0.0113

8 HC, MD, TH 0.994 0.002 0.00410 ±0.0080

Int J Legal Med

infants and the fetuses [31, 32]. Teeth are major factors in ageestimation of fetuses or infants which starts growth during theprenatal embryonic period and have several advantages overskeletal aging since they exhibit less variability than bonesand are more durable against external influences because of itshardness [27, 33]. The hardness of teeth is approximately 5,whereas the bone hardness is 2–3, according to Mohs hard-ness scale, which is the hardest tissue in the body [34–36].Therefore, dental age estimation studies attracted researchers'attention; however, most of them were performed on adultteeth. Among these adult pulp/tooth area ratio was used,where the age error was ±2.5–5 years [37]. Significant corre-lation was found between two rooted maxillary adult teeth andage [38]. The radiographs of the central and lateral incisor

teeth of cases older than 12 years were studied where errorwas found at 1.2–5.08 years [39].

There are also some researches on deciduous teeth. Ageestimation from tooth length of the deciduous dental re-mains of known age showed a confidence interval of 95 %and ±0.1 years of study error [40]. Crown height was foundas an important parameter for age estimation [41]. Refer-ence tables on fetal and infant age estimation from toothmeasurements are still required, especially for forensicscientists. Regarding the fact that the age estimation stud-ies of Turkish children (aged 7–13) by Nolla's, Haavikko's,and Demirjian's methods were not found suitable for Turk-ish children, these charts should also be created for allpopulations [42].

Age in weeks10080604020

Mes

io D

ista

l in

mm

7

6

5

4

3

Fig. 7 The growth pattern of MD measurement of upper central toothaccording to age (p<0.001) and the inverse model [1/age=0.072−0.009MD] (R2=0.884)

Age in weeks10080604020

Lab

io L

ing

ual

in m

m

6

5

4

3

2

Fig. 8 The growth pattern of LL measurement of upper central toothaccording to age (p <0.001) and the inverse model [1/age=0.065−0.01LL] (R2=0.91)

Age in weeks12010080604020

To

oth

Hei

gh

t in

mm

12,5

10,0

7,5

5,0

2,5

Fig. 9 The growth pattern of TH measurement of upper central toothaccording to age (p <0.001) and the logarithmic model in (age)=2.881+0.142 TH (R2=0.97). [TH=the sum of CH and RH]

Tooth Height in mm14,012,010,08,06,04,0

Hea

d C

ircu

mfe

ren

ce in

cm

50

45

40

35

30

25

Fig. 10 The growth pattern of TH measurement of upper central toothaccording to HC (p <0.001) and the logarithmic model HC=6.196+16.504 in (TH) (R2=0.945)

Int J Legal Med

This study showed the strongest correlation and least timeerror for age estimation of fetuses and infants between the HCand tooth variables. Although HC measurement is usuallypreferred by medical and forensic researchers for age estima-tion, in this research age estimation just using HC gaveR2=0.97 with an age estimation error of ±1.13 weeks; how-ever, when age was estimated with the combination of HCand tooth measurements, this R 2 value increases up to0.996 with a lower error of age estimation at ±0–1 week.Therefore, the proposed age estimation formulae (1–8) ofthis research use both the head circumference with fourtooth dimensions (MD, LL, CH, and TH). These formulaecan be applied for various situations such as for livinginfants in clinics, for corpses at autopsy, or for humanremains between ages prenatal 16 weeks to postnatal72 weeks, which gives the age estimation error within ±0–1 week, and shows a better age estimation than using onlythe tooth measurements [27]. However, in cases where fetaland newborn infantile teeth are present as evidences, eventhe skull is disintegrated due to decomposition, then mea-suring the teeth and the application of fetus and infant-specific ATA dental age estimation formulae where age iscorrelated with all tooth dimensions of the deciduous teethwill be beneficial to find the age of the individual [27].

This research revealed that HC and three dimensions oftooth (LL, MD, and TH) are the essential factors for fetusand infant age estimation processes which are fundamentalfactors for forensic odontologists and forensic medical experts.Among these formulas, LL dimension was used in Age Esti-mation Formula 1 , which can be measured beneath the gingi-va, should be preferred for corpses where the tooth can bemeasured in situ and the compass can be situated properlyunder the soft tissue, with a short incision from labial andlingual gingivawhen required at autopsy (R2=0.984with errorof age estimation=±0.0105 week). When LL is combined withthe data of another dimension as MD, which is given in AgeEstimation Formula 5 , a slight increase was found in R2 (R2=0.986with error of age estimation=±0.0140week), but if LL iscalculated with CH dimension as in Age Estimation Formula6 , R2 gets higher one by per thousand (R2=0.987 with error ofage estimation=±0.0155 week). However, the error of ageestimation also gets higher slightly because of the interactionbetween the independent variables.

The MD dimension of tooth, which is used in Age Esti-mation Formula 2 with HC, can be applied safely andnoninvasively for a living infant as the central tooth islocated forefront and can be easily accessed. The mesiodistalcan be measured with a compass in the mouth without givingany harm to their gingival soft tissues or on a plaster dentalmodel obtained from the mouth (R2=0.981 with error of ageestimation=±0.0125 week). If the case is a living individual,then Age Estimation Formula 2 can be preferred as it isnoninvasive and found quite reliable.

The CH dimension, which increases until the initiation ofroot formation (postnatal, 2–4 months), showed relativelylower R2 in Age Estimation Formula 3 (R2=0.979 with errorof age estimation=±0.0135 week). Although, the R2 for CHwas slightly lower than the other formulas in this research, it isstill regarded as an important parameter as claimed byVolchansky and Cleaton [41]. But if CH is combined withthe data of MD as in Age Estimation Formula 7 , R2 becomesmore trustworthy with a smaller error (R2=0.990 with error ofage estimation=±0.0113 week). However, after the start ofroot formation, the sum of crown and root height makes theTH dimension as seen in Age Estimation Formula 4 providesa higher reliability where the error is the least (R2=0.993 witherror of age estimation=±0.0073 week). This result confirmsCordoso's study on age estimation from tooth length of the

THCHMDLLHCAge

TH

CH

MD

LL

HC

Ag

e

Fig. 11 Scatter matrix which shows pairwise relationship betweenvariables

Table 4 Age estimation for selected cases according to 8 age estimation formulas

Case Sex Age Age 1 Age 2 Age 3 Age 4 Age 5 Age 6 Age 7 Age 8

1 M 32.14 33.35 32.71 34.61 32.19 34.08 32.86 31.77 32.26

2 F 28 26.31 26.18 27.44 27.78 26.74 26.47 27,30 27.73

M male, F female, AGE known age, AGE 1–8 calculated ages using formulae 1–8

Int J Legal Med

deciduous teeth [40]. The TH dimension gave better resultsfor age estimation among the other formulas and when thisdimension is computed with MD as in Age Estimation For-mula 8 , the derived result was the best with a very small error(R2=0.994 with error of age estimation=±0.0080 week). Theformulas 4 and 8 are found confidential which can be used forautopsy cases since they need an invasive tooth extractionapplication for root measurement.

Conclusion

This research has disclosed the following facts about the ageestimation method:

1. Age estimation from regional measurement has impor-tance since inmass disasters and inmass graves, the bonesmay be commingled and sometimes only the skull can beobtained without the mandible which is more resistant topostmortem alterations. In these situations, it is beneficialto use one of the suitable age formulas examined in thisarticle which includes head and tooth dimensions.

2. The HC and the upper tooth dimensions (LL, MD, andTH) showed high correlation to define the age.

3. If the case is a living individual, then Age EstimationFormula 2 comprising MD dimension is advised to use.Considering all issues, it is a noninvasive, reliable, andpractical measuring technique which can be easily mea-sured in the mouth with a caliper or on a plaster dentalmodel. This is also a useful and an acceptable methodwhen compared to the hazardous radiographic age esti-mation techniques.

4. Among various tooth measurements, the LL, MD, CH,and TH were the essential ones. The log-linear regressionmodels of all tooth variables fit the best (p <0.001), withR2 ranges between 0.979 and 0.994 and the error of ageestimation in weeks between ±0.0073 and ±0.0155 (with95 % confidence). Among all regression formulas, equa-tions 4 and 8 including TH represented the best withhighest R2 and lowest time error for age estimation. Thedisadvantage of using the TH variable is its obligation tobe applied only in postmortem cases because it requirestooth extraction.

5. The growth patterns of HC, LL, MD, CH, and TH mea-surements showed a linear function to a certain age (ap-proximately 56weeks pre–plus postnatal), then TH slight-ly increases until the closure of the root apex but thegrowth of HC gradually stabilizes in time.

6. The sex has noteless influence on these formulas.7. The small sample size limitation of this research was due

to limited legal permission; therefore, the regression mod-el was applied to tooth and head measurements for ageestimation within the range of prenatal 16 weeks to

postnatal 72 weeks. It is suggested that further extensiveresearch should be conducted with a larger sample size,which can be expanded beyond the infant age period ofpostnatal 72 weeks.

Acknowledgments We are thankful to our precious colleague Mrs.Virginia Lynch, who is a pioneer of forensic nursing in the USA, fromColorado Springs, Colorado, for her review of the English language inthis article, to autopsy technician Mr. Kadir Turkmetin for his valuableassistance during oral autopsies, and to Gulseren Salini for providing aconvenient situation for this research.

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