This paper details for age determination of adult from single rooted theeth. The sample consisted of 100 Italians white Caucasioan patients (46 men, 54 womwn) aged between 18 and 72 years. The single rooted maxillary right canine was utilized in this preliminary study. Pulp/root ration, tooth length ratio, pulp/root area and pulp/root width ratios at three different levels were computed. Pearson's correlation coefficients between age and these variables showed that the ratio between pulp and tooth area correlated best with age (r2 = 0,85). Stepwise multiple regression models yielded a linear relationship between pulp/root width at mid-root level and chronological age and a linear relationship when pulp/tooth area was compared to age. Statistical analysis indicated that these two variables explain 84,9% of variations in estimated chronological age. The median of the absolute value of residual errors between actual and estimated ages was less than four years

CAMERIERE R.

FERRANTE L.

M. CINGOLANI

CINGOLANI, MARIANO

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J Forensic Sci, Mar. 2004, Vol. 49, No. 2Paper ID JFS2003259–492Available online at: www.astm.orgTECHNICAL NOTERoberto Cameriere,1 M.D.; Luigi Ferrante,2 Math.D.; and Mariano Cingolani,1 M.D.Variations in Pulp/Tooth Area Ratio as an Indicatorof Age: a Preliminary Study∗ABSTRACT: This paper details a method for age determination of adults from single rooted teeth. The sample consisted of 100 Italian whiteCaucasian patients (46 men, 54 women) aged between 18 and 72 years. The single rooted maxillary right canine was utilized in this preliminarystudy. Pulp/root ration, tooth length, pulp/tooth length ratio, pulp/tooth area and pulp/root width ratios at three different levels were computed.Pearson’s correlation coefficients between age and these variables showed that the ratio between pulp and tooth area correlated best with age(r2 = 0.85). Stepwise multiple regression models yielded a linear relationship between pulp/root width at mid-root level and chronological age anda linear relationship when pulp/tooth area was compared to age. Statistical analysis indicated that these two variables explain 84.9% of variationsin estimated chronological age. The median of the absolute value of residual errors between actual and estimated ages was less than four years.KEYWORDS: forensic science, age determination by teeth, forensic odontology, dental pulp, pulp/tooth area, stepwise linear regressionSeveral papers in the field of forensic odontology deal withestimating chronological age in humans (1–8). Although skeletalradiology is the most widespread method for age estimation in li-ving subjects, new techniques have allowed great improvements inthe X-ray processing of teeth. These techniques are better suitedfor age estimations than bones in adults (4,5). The most widelyused methods of age estimation depend upon subjective assessmentof tooth development. Inspection of radiographs (by magnifyingglass and caliper) and subsequent comparisons with radiographicimages, drawings and descriptions in charts yield “maturity scores”(1–3,7,8).Alternative approaches based on digitalization of panoramicradiographs and their computerized storage have recently becomeavailable (6). These procedures exploit image analysis to obtainnondestructive metric measurements of both pulp chambers andteeth. Forensic odontologists may now utilize these techniques thatare relatively precise and accurate (6). Computer-assisted imageanalysis avoids the bias inherent in observer subjectivity, improvesthe reliability and the statistical analysis of data.A number of statistical methods have been proposed for age deter-mination of adults. Most of these methods are based on establishingcorrelations between individual age (dependent variable) and somesignificant tooth parameters (predictors) obtained from digitizedradiographs (9). The most frequently used statistical technique forage estimation in forensic dentistry is multiple linear regression,although partial least-squares linear regression, polynomial regres-sion, and other robust regression methods have also been applied.1 Institute of Forensic Medicine, University of Macerata, Macerata, Italy.2 Institute of Biochemical Biotechnologies, Faculty of Medicine, Polytech-nical University of Marches, Ancona, Italy.∗ This work was funded by a grant to the Polytechnical University of Marches,MURST.Received 8 Oct. 2003; and in revised form 16 Nov. 2003; accepted 16 Nov.2003; published xxxx.The purpose of the present investigation is to present a method forassessing chronological age based on the relationship between ageand measurement of the pulp/tooth area ratio (AR) on single-rootedteeth. In an attempt to improve the precision and reliability of ageestimations, other dental features were also taken into account andthe different statistical models were compared.Materials and MethodsSubjects and MaterialsOrthopantomographs of 100 Italian white Caucasian patients(46 men, 54 women) aged between 18 and 72 years were analyzed(Table 1). X-rays were digitized using a scanner and images wererecorded in a computer file. Image analysis showed how canines,incisors and second premolars yield the clearest digital images.For this preliminary study, the right maxillary canine was selected,because it was always present and was the most suitable for mea-surement.Radiographic images of canines (RIC) were processed using acomputer-aided drafting program (AutoCAD2000, Install Shield3.0, 1997). Twenty points from each tooth outline and ten pointsfor each pulp outline were identified and used to evaluate toothand pulp areas. Measurements of the RIC yielded pulp and toothareas; tooth, pulp and root lengths; and pulp and root widths, at threedifferent levels. All RIC measurements were carried out by the sameobserver. To test intra-observer reproducibility, a random sample oftwenty RIC were re-examined after an interval of two weeks.Statistical AnalysesThe following morphological variables were recorded (9): p =pulp/root length; r = pulp/tooth length; a = pulp/root width atenamel-cementum junction (ECJ) level; c = pulp/root width at mid-root level; b = pulp/root width at midpoint level between ECJ levelCopyright C© 2004 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. 12 JOURNAL OF FORENSIC SCIENCESTABLE 1—Age and gender distribution of study sample.Age No. of No. of(Years) Males Females Total18–29 11 12 2330–39 15 15 3040–49 9 15 2450–59 6 5 1160–69 5 5 1070–73 0 2 2Total 46 54 100and mid-root level; AR=pulp/tooth area ratio. These measurementswere normalized to allow for angulation distortion (9).The morphological variables, the age and the subjects’ genderwere entered in a Microsoft EXCEL R© spreadsheet for use as pre-dictive variables for age estimation. Unlike other methods (9), thet ratio (tooth/root length) in measured morphologic variables, be-cause it is functionally dependent on p and r (t = p/r) and thereforedoes not add information concerning dental age. The chronologi-cal age was calculated by subtracting date of birth from the dateof radiograph. Intra-observer reproducibility of measurements wasstudied using a paired t-test.Correlation coefficients were evaluated between age and predic-tive variables. A multiple linear regression model for age predictionwas developed by selecting those variables, which contributed sig-nificantly to age estimations using the stepwise selection method.Analysis of covariance (ANCOVA) was then applied to study pos-sible interactions between significant morphological variables andgender. Statistical analysis was performed with S-PLUS 6 statisticalprograms (S-PLUS R© 6.1 for Windows PROFESSIONAL EDITIONRelease 1). The significance threshold was set at 5%.ResultsThere were no statistically significant intra-observer differencesbetween the paired sets of measurements carried out on the RIC(p = 0.64).Pearson’s correlation coefficients between age and morpholog-ical variables (Table 2) showed that the ratios between lengthmeasurements correlated worst with age. In particular, the variablep (ratio between pulp and root length) was not significantly corre-lated with age and was therefore excluded from further statisticalanalysis.All other correlation coefficients between age and morphologi-cal variables were significant and negative. The subjects’ age wasmodeled as a linear function of the morphological variables (pre-dictors). A stepwise regression procedure was applied to optimizethe model. The results (Table 3) show that only variables AR and ccontributed significantly to the fit. The regression model utilizingAR and c, yielding the following linear regression formula:Age = 86.53 − 457.15 AR − 22.98 c (1)This model had the lowest AIC (Akaike Information Criterion)value (624.0) among the considered linear models. There was amodest improvement in model fit when all five predictors wereused. The full model explained 85.1 % of total variance, whereas themodel, with the AR and c variables explained 84.9% (r2 = 0.849).The median of the absolute values of residuals (observed ageminus predicted age) was 3.7 years, with a quartile deviation of4.3 years.TABLE 2—Correlation coefficients between age and predictivemorphological variables.RA p r a b c−0,92 0,11∗ −0,21† −0,31 −0,38 −0,42∗ No significance p < 0.05.† p = 0.04.TABLE 3—Stepwise regression analysis predicting chronological agefrom selected predictors.Regression StandardCoefficient Error t97;0.05 p-levelIntercept 86.53 2.26 38.26 <0.001RA −457.15 21.92 −20.86 <0.001c −22.98 11.17 −2.06 0.042TABLE 4—Summary table of ANCOVA.df SS MS F pIntercept 1 41219.17 41219.17 1433.59 <0.001RA 1 12439.44 12439.44 432.64 <0.001c 1 128.55 128.55 4.47 0.037Gender 1 11.67 11.67 0.41 0.526Error 96 2760.23 28.75Total 99 18374.91The residual plot (Fig. 1, left panel) shows no obvious pat-tern and only three observations appeared to be outside the ex-pected boundaries. The observed versus predicted plot (Fig. 1, rightpanel) shows that the regression model fits the trend of the datareasonably well. Hence, both diagnostic plots support the cho-sen model. Only a small increase in the residual could be seenwhen the simplest linear model with only AR as covariate was used(age = 84.31 − 473.86 AR). It should also be noted that, althoughit was not the best fit, this simple linear model explained 84.26%of total variance.To study the possible effect of gender on the linear regressionmodel, an analysis of covariance was performed (ANCOVA). Ac-cording to the previous analysis, covariates AR and c had a signif-icant influence on the age of subjects (Table 4). The small F-valuewhich accounts for gender (F = 0.406; p = 0.526) revealed thatgender does not significantly influence the regression model usedto estimate chronological age for both female and male groups.DiscussionThe need to estimate the age of living individuals is becomingincreasingly important in forensic odontology. There are increasingnumbers of immigrants (illegal or otherwise) who arrive in a coun-try without acceptable identification papers and, more generally,individuals with missing or uncertain birth data. The study of themorphological parameters of teeth on dental X-rays of adult humansis more reliable than most other methods for age estimation.Several studies show that morphological measurements can bereliably utilizing panoramic dental radiographs. These studies re-quire that some corrections are made to take into account individualvariability of tooth size, differences in magnification of radiographsand angulation between X-ray beam and film. Some studies (9,10)suggest using the ratio between pulp area and tooth, and the ratiosof length and width of the pulp/tooth area, instead of their directmeasurement. When area, length and width of pulp and tooth wereCAMERIERE ET AL.  PULP/TOOTH AREA AS AN INDICATOR OF AGE 3FIG. 1—Plots of residuals against fitted values (left panel) and of observed versus predicted values (right panel), with regression model 1.measured on digitized images of canines, the paired t-test showedthat there were no significant intra-observer differences. It can beconcluded that the RIC technique can produce reliable and repro-ducible intra-observer measurements.In the sample of 100 individuals, the AR (pulp/tooth area ratio)of the right maxillary canine proved to be closely correlated withsubjects’ chronological age. The application of the RIC method forage estimation seems promising (10,11). Further study will includeapplying the RIC method to other single rooted teeth such as incisorsand second premolars.This preliminary study was limited to the right maxillary caninebecause it was always present and generally showed clearer imagesthan other single rooted teeth. Nevertheless, including other singlerooted teeth and their morphological parameters should provide abetter estimate of chronological age. Statistical analysis on regres-sion models shows that the RA is better correlated with chronolog-ical age than the linear measurement ratio, and the pulp/root ratio.Width is a better indicator of age than length.The RIC method yields a median of the absolute value of resi-dual error of less than 4 years, and a standard error of estimateof 5.35 years. It is therefore comparable to other age estimationmethods in adults. This method is reasonably accurate consideringthat only one canine was evaluated for each subject. Analysis ofcovariance showed that gender had no significant influence on ageestimation when only right maxillary canine measurements wereutilized. Gender was not included as a factor in the model equation.Repetitive measurements must be carried out by other independentobservers in order to verify inter-observer reproducibility (12). Alsothe determination of minority/majority age will be an important fieldof future application.In the future, image analysis programs which can recognize pulpoutlines in a radiographic images will be very useful in minimizinghuman manual measurement of morphological parameters, and willprobably reduce both inter- and intra-observer variability.Other planned studies include attempts to reduce the residualstandard error and a comparison of multiple linear regression mod-els for age estimation with other statistical methods such as partialleast-squares, robust regression methods, or other non-linear regres-sion procedures.References1. Demirjian A, Goldstain H, Tanner JM. A new system of dental ageassessment. Hum Biol 1973;45:221–7.2. Demirjian A, Goldstain H. New systems for dental maturity based onseven and four teeth. Ann Hum Biol 1976;3:411–21.3. Mincer HH, Harris EF, Berryman HE. The A.B.F.O. study of third molardevelopment and its use as an estimator of chronological age. J ForensicSci 1993;38:379–90.4. Liversidge HM, Herdeg B, Ro¨sing FW. Dental age estimation ofnon-adults: a review of methods and principals. In: Alt KW, Ro¨sing FW,Teschler-Nicola M, editors. Dental anthropology. Fundamentals, limitsand prospects. Vienna: Springer, 1998;420–42.5. Ro¨sing FW, Kvaal SI. Dental age in adults: a review of estima-tion methods. In: Alt KW, Ro¨sing FW, Teschler–Nicola M, editors.Dental anthropology. Fundamentals, limits and prospects. Vienna:Springer, 1998;443–68.6. Willems G. A review of the most commonly used dental age estimationtechniques. J Forensic Odontostomatol 2001;19:9–17.7. Teivens A, Mo¨rnstad H. A modification of the Demirjian method for ageestimation in children. J Forensic Odontostomatol 2001;19:26–30.8. Mesotten K, Gunst K, Carbonez A, Willems G. Dental age estimationand third molars: a preliminary study. Forensic Sci Int 2002;129:110–5.9. Kvaal SI, Kolveit KM, Thomsen IO, Solheim T. Age estimation of adultsfrom dental radiographs. Forensic Sci Int 1995;74:175–85.10. Kvaal SI, Solheim T. A non-destructive method for age estimation.J Forensic Odontostomatol 1994;12:6–11.11. Kolltveit KM, Solheim T, Kvaal SI. Methods of measuring morphologicalparameters in dental radiographs. Comparison between image analysisand manual measurements. Forensic Sci Int 1998;94:87–95.12. Willems G, Moulin–Romsee C, Solheim T. Non-destructive dental-agecalculation methods in adults: intra- and inter-observer effects. ForensicSci Int 2002;126:221–6.Additional information and reprint requests:Roberto Cameriere, M.D.Institute of Forensic Medicine—University of MacerataVia Don Minzoni n. 962100 Macerata (Italy)E-mail: rmaigret@libero.it

Variations in pulp/tooth area ratio as an indicator of age: a preliminary study

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