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 Table of Contents  
ORIGINAL ARTICLE
Year : 2015  |  Volume : 27  |  Issue : 2  |  Page : 171-177

Phenotypic differences in teeth dimensions among Chennai population: An aid in sex determination


Department of Oral Medicine and Radiology, Saveetha Dental College and Hospital, Chennai, Tamil Nadu, India

Date of Submission03-Mar-2015
Date of Acceptance11-Dec-2015
Date of Web Publication21-Nov-2015

Correspondence Address:
Sreedevi Dharman
Department of Oral Medicine and Radiology, Saveetha Dental College, Poonamallee High Road, Vellappanchavadi, Chennai - 600 077, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0972-1363.170132

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   Abstract 

Objective: To investigate the presence of sexual dimorphism by studying the size of the teeth among males and females in Chennai population, which aids in sex determination. Materials and Methods: Incisocervical length, mesiodistal and buccolingual diameters were measured in teeth of 60 subjects (30 males, 30 females) in the age group of 18-22 years from Chennai population. The differences in the mean values of parameters in males and females were calculated using independent t-test. Discriminant functional analysis was performed to determine the accuracy of sex. Results: Significant differences were found in mean incisocervical length which were found to be larger in males with P < 0.05 in 11, 12, 14, 17, 21, 22, 24, 26, 27, 31, 32, 33, 34, 41, 43, and 45 and with P < 0.001 in 13, 23, 32, 42, 43, and 44, with the exception of 37 and 47 which were larger in females. Mean mesiodistal diameter was larger in males with P < 0.05 in 11, 12, and 21 and with P < 0.001 in 13, 23, 33, and 43. Mean buccolingual diameter was larger in males with P < 0.05 in 12, 21, 31, 33, and 41 and with P < 0.001 in 11, 13, 23, and 43. Accuracy rate of predicting sex based on incisocervical length (17, 23, 47) and mesiodistal diameter (13, 33) was 78.3% and based on buccolingual diameter (13) was 76.7%. Conclusion: Males showed greater sexual dimorphism than females. Application of incisocervical, mesiodistal, and buccolingual dimensional variability among males and females in the Chennai population can aid in sex determination in forensic odontology, as the results showed moderate extent of dimorphism with an overall accuracy rate of predicting sex to be 78%.

Keywords: Buccolingual diameter, incisocervical length, mesiodistal diameter, sex determination, sexual dimorphism


How to cite this article:
Dharman S, Gnanasundaram N, Gopal M, Muthukrishnan A. Phenotypic differences in teeth dimensions among Chennai population: An aid in sex determination. J Indian Acad Oral Med Radiol 2015;27:171-7

How to cite this URL:
Dharman S, Gnanasundaram N, Gopal M, Muthukrishnan A. Phenotypic differences in teeth dimensions among Chennai population: An aid in sex determination. J Indian Acad Oral Med Radiol [serial online] 2015 [cited 2019 Sep 18];27:171-7. Available from: http://www.jiaomr.in/text.asp?2015/27/2/171/170132


   Introduction Top


People are born with an identity and deserve the right to die with an identity. [1] An important initial step in identification of the dismembered remains of mass disaster victims is the separation of sexes. [2] Identification of human remains during mass disasters is hindered by the state of the soft tissue. With relevant expertise, it is carried out on bones and teeth. [3],[4] Forensic dentistry deals with the determination of age, sex, and identity of a person from dentition. [5] The dentition is considered as a useful adjunct in skeletal sex determination, particularly since teeth are resistant to postmortem destruction and fragmentation. [6] Today, dentists are respected widely as a source of valuable data that can be used to answer questions that arise during a death investigation, and forensic dentists can use these data to provide significant conclusions that can initiate, extend, and substantiate the work of coroners, medical examiners, and detectives. [7]

Although the morphology of the tooth structure is similar in males and females, the size of the tooth does not necessarily remain the same, as the tooth size is determined by cultural, environmental, racial and genetic factors. [8] Sexual dimorphism is more pronounced in the permanent dentition than in the deciduous teeth. [9] Mesiodistal and buccolingual diameters of the permanent tooth crown are the two most commonly used and researched features used in determining sex on the basis of dental measurements. [10] Sex dimorphism in tooth size and the accuracy of odontometric sex prediction are found to vary in different regions, and researchers have advocated the need for population-specific data. [11] With this background, the present work was undertaken to generate a standard value of size of teeth in all dimensions in the determination of gender in Chennai (South Indian) population for application in forensic science.


   Materials and Methods Top


Sixty subjects divided into Group A with 30 males and Group B with 30 females, in the age group of 18-22 years, with power 90% at P < 0.05, were selected from Saveetha Dental College and Hospital, Chennai.

Selection criteria

The subjects having complete set of fully erupted teeth up to second molars, who were periodontally healthy and having non-carious, non-attrited teeth free from morphological and structural abnormality, and intact and satisfactorily aligned maxillary and mandibular teeth with no history of orthodontic treatment and crown restorations were included in the study. Informed consent was obtained from all the patients who were willing to participate in the study.

Incisocervical length was measured intraorally; mesiodistal and buccolingual diameters were measured in models. The models of complete permanent dentition were prepared by taking alginate impressions and pouring immediately with dental stone. A digital Vernier caliper (General Ultratech, General Tools and Instruments, New York, USA, with a resolution of 0.01 mm) was used.

Incisocervical length

The occlusal reference point for incisors and canines was the incisal edge and for premolars it was the cuspal tip. Incisocervical length was measured from the reference point to the gingival margin [Figure 1]. The long axis for all the teeth up to second premolar was the vertical reference plane. For molars, the developmental groove between the mesiobuccal and distobuccal cusps was identified and a line parallel to it running from the mesiobuccal cusp to the gingival margin was measured.
Figure 1: Measurement of incisocervical length intraorally

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Mesiodistal diameter

The greatest mesiodistal dimension between the contact points of teeth taken at maximum convexity of the tooth measured parallel to the occlusal plane and a plane parallel to the vestibular surface was measured as the mesiodistal diameter [Figure 2].
Figure 2: Measurement of mesiodistal diameter in study models

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Buccolingual diameter

The greatest distance between the buccal and lingual surfaces of the crown, taken at right angles to the plane in which the mesiodistal diameter was taken was measured as the buccolingual diameter [Figure 3].
Figure 3: Measurement of buccolingual diameter in study models

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Statistical analysis

Using the statistical program SPSS for Windows, descriptive statistics were calculated for each group independently. The statistical significance of the difference in mean in incisocervical, mesiodistal, and buccolingual diameters between males and females was calculated using the t-test for independent samples with P < 0.05. Discriminant function statistics was performed, where data were analyzed stepwise for all the three dimensions of teeth, to determine the accuracy of sex prediction. Jackknife statistics were used to assess accuracy of the results on a presumable, unknown sample.


   Results Top


[Table 1] and [Table 2] show the mean values and standard deviation of incisocervical length, mesiodistal and buccolingual dimensions in male and female groups.
Table 1: Mean incisocervical, mesiodistal, buccolingual dimensions of teeth in the maxillary arch among male and female groups

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Table 2: Mean Incisocervical, mesiodistal, and buccolingual dimensions of teeth in the mandibular arch among male and female groups

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Incisocervical length in maxillary and mandibular teeth

All the maxillary and mandibular incisors (11, 12, 21, 22, 31, 32, 41, 42) showed significant difference (P < 0.05) between male and female groups, of which 32 and 42 exhibited higher difference (P < 0.001). Maxillary and mandibular canines (13, 23, 33, 43) showed significant difference (P < 0.05), of which 13, 23, and 43 exhibited higher difference (P < 0.001). Maxillary and mandibular premolars (14, 24, 34, 44, 45) showed significant difference (P < 0.05), of which 44 exhibited higher difference (P < 0.001). Maxillary and mandibular molars (17, 26, 27) showed significant difference (P < 0.05) between male and female groups. The incisocervical lengths of all the teeth were greater in males than in females, with the exception of 37 and 47, in which the length was found to be greater in females when compared to males, though the difference was not statistically significant.

Mesiodistal diameter in maxillary and mandibular teeth

The maxillary anteriors (11, 12, 21) showed significant difference (P < 0.05) between male and female groups. All maxillary and mandibular canines (13, 23, 33, 43) exhibited higher significant difference (P < 0.001). Mandibular molars (36, 47) showed significant difference (P < 0.05) between male and female groups. The mesiodistal diameter of maxillary and mandibular teeth was greater in males than in females.

Buccolingual diameter in maxillary and mandibular teeth

The maxillary and mandibular anteriors (11, 12, 21, 31, 41) showed significant difference (P < 0.05) between male and female groups, of which 11 and 21 exhibited higher difference (P < 0.001). All maxillary and mandibular canines (13, 23, 33, 43) exhibited higher significant difference (P < 0.001). Maxillary and mandibular premolars (14, 15, 24, 25, 34, 44, 45) showed significant difference (P < 0.05). Maxillary and mandibular molars (16, 17, 26) showed significant difference (P < 0.05). The buccolingual diameters of maxillary and mandibular teeth were greater in males than in females.

Canonical discriminant function analysis

Males showed greater incisocervical, mesiodistal, and buccolingual dimensions of teeth in comparison to females. Based on this, three different functions were established [Table 3]. The functions developed were as follows:
Table 3: Canonical discriminant function coeffi cients

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Function 1: Incisocervical measurements of all variables.

Function 2: Mesiodistal measurements of all variables.

Function 3: Buccolingual measurements of all variables.

Incisocervical length (17, 23, 47), mesiodistal diameter (13, 33), and buccolingual diameter (13) contributed to discriminant analysis. Several stepwise discriminant function statistics have been used to develop formulae to determine sex. Discriminant function statistics provides coefficients and sectioning points for each function to determine sex. The group centroids indicate the average discriminant scores for each sex. Sectioning point is the average of male and female group centroids. The sectioning point for all the three dimensions was calculated to be 0.0. Raw coefficients are the discriminant function coefficients used to calculate the discriminant score.

Jackknife statistics were used to assess accuracy of the results on a presumable, unknown sample. To assess the sex, tooth dimensions were multiplied with the respective unstandardized coefficients and added to the constant. If the values thus obtained were greater than the sectioning point, the individual was considered as male, and if they were lesser, then the individual was considered as female.

Thus, y = a + b (p1) + b (m 2 ),

where a = constant of each particular function and b = unstandardized coefficient for that particular tooth. For function 1, a = −10.001, for function 2, a = −19.391, and for function 3, a = −14.672 and y = constant of raw coefficient of a particular dimension plus unstandardized coefficient of that particular tooth multiplied by (tooth measurement in centimeters) plus unstandardized coefficient of that particular tooth multiplied by (tooth measurement in centimeters).

For example, for function 1,

If −10.001 + (0.903 × T17 + 1.215 × T23 - 1.054 × T47) < 0, then the measurements indicate that it is from a female.

If −10.001 + (0.903 × T17 + 1.215 × T23 - 1.054 × T47) > 0, then the measurements indicate that it is from a male.

Correct classification of sex

Based on incisocervical and mesiodistal dimensions, 76.7% of males were correctly classified and 23.3% were misclassified; 80% of females were correctly classified and 20% were misclassified. Based on buccolingual diameter, 73.3% of males were correctly classified and 26.7% were misclassified; 80% of females were correctly classified and 20% were misclassified. Thus, the accuracy rate of correct classification of sex was found to be 78.3% for incisocervical length (17, 23, 47) and mesiodistal diameter (13, 33); 76.7% of cases were correctly classified based on buccolingual diameter (13) [Table 4] and [Table 5].
Table 4: Accuracy rate of predicting sex in incisocervical (17, 23, 47) and mesiodistal (13, 33) dimensions

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Table 5: Accuracy rate of predicting sex in buccolingual diameter 13

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   Discussion Top


Although the DNA profile gives accurate results, measurement of linear dimensions such as anthropometric or odontometric parameters can be used for determination of sex in a large population because they are simple, reliable, inexpensive, and easy to measure. Considering the fact that there are differences in odontometric features in specific populations, it is necessary to determine their values in order to make identification possible on the basis of dental measurements. [10] This study was intended to analyze the sexual dimorphism in all the maxillary and mandibular teeth among males and females in Chennai population.

Doris et al. [12] have indicated that the early permanent dentitions provide the best sample for tooth size measurements because early adulthood dentition has less mutilation and less attrition in most individuals. Thus, subjects in the 18-22 years age group only were included in the study sample. In our study, males exhibited larger-sized teeth than females based on incisocervical, mesiodistal, and labiolingual measurements of maxillary and mandibular teeth, which is in accordance with Garn et al., [9] Saunders et al., [13] Schwartz and Dean, [14] Alvesalo et al., [15] and Richardson. [16]

All the maxillary and mandibular canines were found to be more statistically significant for sexual dimorphism in our study, which is in accordance with the studies of Işcan and Kedici,[10] Khangura et al., [17] Hattab et al., [18] and Lund and Mörnstad [19] who studied 58 dental casts of Swedish subjects and found the canines to be most dimorphic of all the teeth. Minzuno [20] reported that maxillary canine showed a higher degree of sexual dimorphism compared to mandibular canine in a Japanese population. Otuyemi and Noar [21] showed dimorphism in maxillary canine bilaterally. Garn et al. [8] found that mandibular canine exhibited a greater degree of sexual dimorphism than the maxillary canine in mesiodistal dimension. Thus, a controversy exists regarding the degree of sexual dimorphism between mandibular and maxillary canine teeth in different ethnic groups.

In our study, mandibular canine was more dimorphic, followed by maxillary canine and maxillary central incisors in all the three dimensions, whereas studies by Acharya and Mainali, [22] Kondo et al., [23] Kondo and Townsend, [24] and Ling and Wong [25] indicate that the mandibular canine is the tooth that presents greater dimorphism, followed by the first and second maxillary molars. In their study, Zorba et al. [26] determined sex in modern Greeks using diagonal measurements of molar teeth and showed that males have larger molars than females (P < 0.05). The present study shows that the maxillary molars, 16, 17, and 26 in buccolingual dimensions, and 17, 26, and 27 in occlusocervical dimensions were larger in males than in females. Khangura et al. [17] and Howe et al.[27] found that mesiodistal dimensions of male dentition are greater than those of females, which is consistent with our study.

In accordance with our study, Işcan and Kedici[10] studied buccolingual breadths which revealed that males exceeded females significantly in dimensions and found sexual dimorphism only in maxillary left canine. In our study, all the canines exhibited greater sexual dimorphism in buccolingual dimensions. In our study, buccolingual dimensions of permanent teeth were statistically higher than mesiodistal dimensions. Similarly, Staley and Hoag [28] described the presence of sexual dimorphism in mesiodistal diameter of permanent teeth among Caucasians and dimorphism percentage was higher in terms of buccolingual dimensions. The study by Prabhu and Acharya [11] differs from our study in the fact that maxillary first and second molars in buccolingual dimensions exhibited more dimorphism than canines. Also, nine tooth variables exhibited reverse dimorphism, i.e. female dimensions were larger than those of males. In our study, occlusocervical length was greater in females than in males in 37 and 47. Acharya and Mainali [22] found reverse dimorphism in the mesiodistal dimension of mandibular second premolar in the Nepalese population. The finding could be attributed to evolution resulting in a reduction in sexual dimorphism, causing an overlap of tooth dimension in modern males and females.

Harris et al.[29] found the contribution of various tissues in sexual dimorphism of tooth size. They found that males typically have significantly larger dentine and pulp dimensions than females, while marginal enamel thickness was similar in both sexes. Moss and Moss-Salentijn [30] suggested that dimorphism is related to an absolutely longer period of amelogenesis for both deciduous and permanent dentition. The accuracy rate of correct classification of sex was 78.3% for incisocervical length (17, 23, 47) and mesiodistal diameter (13, 33). Also, 76.7% of cases were correctly classified based on buccolingual diameter (13), which is similar to the study conducted by Işşcan and Kedici[10] on Turks. Acharya and Mainali have quoted that Kieser et al. tested posterior teeth of South African Whites and obtained an accuracy of 87% in the classification of sex. [22] The variation in the magnitude of dimorphism can be a result of various factors. It may be due to the environmental influences on tooth size, such as variation in food resources exploited by different populations, or due to the interference of cultural factors with biological forces. [17] On the whole, sexual dimorphism of teeth is population specific and males have larger tooth dimensions when compared to females, which can aid in sex determination in forensic science.


   Conclusion Top


Identification of a deceased person is one of the responsibilities of forensic dentist. Sex determination is an important element in the analysis of biological evidence submitted to forensic laboratories. In the present study, males showed greater sexual dimorphism than females in all the three dimensions. Application of incisocervical, mesiodistal, and buccolingual dimensional variability among males and females in the Chennai population can aid in sex determination in forensic odontology, as the results showed moderate magnitude of dimorphism with an overall accuracy rate of predicting sex to be 78%.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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