Nazeer Khan* , Arham N. Chohan**
How to CITE:
J Pak Dent Assoc 2010;19(3): 180 -183
To find out the most suitable and reliable method for estimation of age of Saudi female children at the time of eruption of a permanent tooth.
The population used for this cross-sectional study was comprised of female schoolchildren from kindergarten to intermediate schools (pre-school to grade 9) of Riyadh, Saudi Arabia. A total of 4836 children were examined and only 1599 children showed at least one tooth ‘just’ erupted. Height and weight of the selected sample were recorded after the clinical examination. The demographic information was recorded from their personal files of the school record. Number of teeth present at the time of eruption of a new permanent tooth (Method 1) and linear regression (Method 2) were employed to estimate the calendar age.
On average time of 5 years and 9 months, two teeth are erupted in Saudi female children and about 13 years of age all the teeth except third molars are erupted. The regression equation of age (Y) with height(X1), weight(X2) and total number of teeth(X3) erupted was as follows:
Ŷ = -6.008 + 0.182 X1 + 0.096 X2 – 0.013 X3 R = 0.847;
Results showed that calendar age of 63% and 70.8% of the Saudi females can be estimated accurately within ± 1 year by Method 1 and Method 2, respectively. Furthermore, age of 38.5% and 39.4% of Saudi female children can be accurately estimated within ±0.5 years by these two methods, respectively.
Regression method showed better age estimation procedure than simply counting the number of teeth at the time eruption.
Saudi Arabia, Age estimation, time of eruption, regression analysis.
Introductionp>Number of teeth is commonly used as an indicator to determine the age of children at death or unknown skeletons to find out the concordance with the information of missing children. Furthermore, the age estimation can also be used of living children with unknown birth record. In many countries of Africa and Asia, especially in rural areas, proper birth records are not available of many children. Therefore, instances such as schooling, community health projects and job requirement, need estimation of age for the required procedures. Furthermore, the estimation of age becomes very important to the countries where different laws are implemented for different age groups, such as French law where different penal procedures are used for 13, 16 and 18 years old children.1
Different procedures are employed to estimate the calendar age, using certain developmental stages of primary and permanent teeth in the literature. Some of them are: the mean and median2,3,4 of eruption time; probit analysis3,5,6 on the number of teeth present; time of eruption of permanent teeth7,8,9, regression analysis with number of teeth present and germs of the 3rd molars1, estimation through the developments stages of the teeth10 and radiographic assessment 11,12 .These different methods were applied on the data of Asian3,4,5,8,13, African2,7,14, American and European1,8,9 children. However, as far as authors’ knowledge is concerned, the data of Saudi children have not been used to estimate the calendar age by any of the methods mentioned above. Therefore estimation of age was attempted on the data collected earlier for the studies on time of eruption of permanent teeth of Saudi Female children15,16. The objective of the study was to find out the most suitable and reliable method for estimation of calendar age for Saudi female children at time of eruption of permanent tooth. Two methods were applied: for the same Method1: number of teeth present at the time emergence of a new tooth, and Method 2: regression equation on number of teeth present at the time of emergence of a new tooth with height and weight of the children
The population used for this cross-sectional study comprised of female schoolchildren from kindergarten to intermediate schools (pre-school to grade 9) of Riyadh, Saudi Arabia. Eight government schools (4 primary and 4 intermediate) were randomly selected from four regions of Riyadh urban area. In addition, two private schools (one primary and one intermediate) were also randomly selected. All the children were Saudi national. Before the visits to schools, permission was taken from Directorate of Riyadh schools. The examiners were calibrated with a senior pedodontist, who is also the co-author (ANC), using clinical pictures before showing some cases in the pediatric clinics. No casts or subjects were used for inter or intra examiner calibration, because it is very easy to distinguish among the three different conditions; erupted, just erupted and unerupted tooth. Virtanen17 indicated that the criteria for tooth emergence are so clear that evaluation of the error of the method is not necessary. The detailed methodology is discussed in earlier publications.15,16 A total of 4836 children were examined and only 1599 children were found suitable for the study i.e. at least one tooth was just erupted. The data were collected in November and December of year 2005 and 2006.
The clinical dental examination was carried out under natural light by direct visual inspection and manual palpation by using gloves. Height and weight of the selected sample were recorded after the clinical examination. The demographic information about the children: such as age, educational level, date of birth, place of birth, and family name were recorded from their personal files of the school record.
The data were then entered into the computer utilizing the Statistical Package for Social Science (SPSS) program version 10. Number of permanent teeth present at the time of eruption of a new permanent tooth (Method 1) and linear regression procedure (Method 2) were employed to estimate the age. Number of permanent teeth present at the eruption time of a new tooth, height and weight of the children were the independent variables in regression analysis. The error in estimation was calculated at ±0.5 years, ±1.0 years, ±1.5 years, ±2.0 years > 2.0 years and < -2.0 years for both the methods
The mean (±SD) age of 1599 female children was 9.6(±2.6) years (R: 4.6 to 16.1 years). The mean (±SD) of height and weight of the children were 134.7(±14.1) cm and 33.4(±12.7) kg respectively (Table1).
Table 1: Descriptive Statistics of demographic variables and total number of teeth erupted
The estimation of age by Method 1 is discussed in Table 2
Table 2: Mean eruption time of number of teeth erupted
On average time of 5 years and 9 months, two teeth were erupted in Saudi female children and about 13 years of age all the teeth, except third molars were erupted. The correlation of age with height, weight and total number of teeth erupted were 0.88, 0.71 and 0.88 respectively. All the three correlations were statistically significant (p<0.001)
weight and total number of teeth erupted at the eruption time of a new tooth was as follows:
Where, Y = age;
X1= Total teeth erupted,
The sequence of entry of independent variables in the 2 equation was X1, then X2 and then X3. R value describes that 84.7% of the variation among calendar age was explained by these three independent factors. The authors also used the squared term of number of teeth present in the equation. Even though that term was statistically significant in the regression equation, but the adjusted R2 did not change. That means, the contribution of this term in the equation was negligible. Therefore, the regression equation with the squared term is not reported here.
Table 4: Error in estimation by regression method and number of teeth present
Table 4 shows the frequency of residual computed from the data using these two methods of estimation. It showed that the calendar age of the Saudi females can be estimated within ± 1 year with 63% and 70.8% of accuracy by Method 1 and Method 2, respectively. Furthermore, the calendar age of Saudi female children can be accurately estimated within ±0.5 years with 38.5% and 39.4% by these two methods, respectively. It should also be noted that the error percentages were decreasing a very systematic way in Method 2 as compared to Method 1
One of the important chapters in forensic anthropology is the determination of age, using different procedures. Odontology helps in this regard for different age groups and gender. Demirjian method18,19 of determining the age, using four or seven teeth, are established reference procedures. However, as indicated by Fori et al1, these methods have several limitations: (1) age can not be precisely evaluated after 16 years of age; (2) it is based on observations derived from radiographs; (3) the appreciation of developmental stages is difficult because the choice of tooth development stage is quite subjective; and (4) it proved to be applicable in Canadian children but not reliable if applied to other populations20,21. Other teeth development stage, like time of eruption is also used for estimation of age2,3,4,,6,7,8,9,22,23 .However, Towlson and Peck24 indicated their reservation in the reliability of age estimation in counting of teeth at the time of eruption. Few studies3,7 have used probit analysis25 on number of teeth at the time of eruption. However, Gillett7 showed that this procedure is quite inferior than number of teeth present at the time of a tooth eruption and regression analysis. Therefore, the two more reliable methods were applied to estimate the calendar age for this study. Regression procedure (Method 2) showed better estimation procedure than simply counting the number of teeth at the time eruption (Method 1). Gillett7 showed the accuracy of 39% using Method 1 and 38.5% using the Method 2 with the error of ±0.5 years.These results were almost the same obtained from this study. For the accuracy of ±1.0 years, the results of Gillett7 also showed almost the same accuracy of 67.5% and 69% of these two methods, respectively. Furthermore, it should also be noted that 84.7% variability of estimation is counted by only three variables; number of teeth present at the time of a tooth eruption, height and weight of the child. Therefore, the estimation of age by regression method is reliable and superior than the method depends only upon counting of teeth at the time of eruption of a permanent tooth. Foti et al1 also showed that regressive models are superior than counting the number teeth at the time of eruption and Demirjian methods19 and concluded that regressive model proved to be reliable estimations of the real age. It should be noted that this data were obtained from only female school children. Because all the data collecting investigators were female dentists and according to the school regulations of Saudi Arabia male doctors/dentists can not visit female schools. Therefore, the model should be applied with caution. It is recommended that same type of study should be conducted for male Saudi children to make a general model for Saudi children
The dentists of Saudi Arabia can estimate the age of Saudi Female children, using only height, weight and total number of teeth at the time of eruption of any tooth by 71% of accuracy of within ±1 year
The authors are grateful to Drs. Faten Al-Nasser, Dalal Al-Sharani, Rana Al-Jorais, Reem Al-Salehi, Tagreed Al-Yousef, Lina Al- Nahedh, Mashael bin Hassan, Nora Al-Sufyani, Mona Al-Motairy and Shreen Al-Selouly for data collection. We are also thankful to Ministry of Health, Riyadh region for giving me the permission to conduct this study. We are also indebted to the administration of all the participating schools for allowing us to screen their schoolchildren
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