Sex determination in mandibles in the first year of life by a quantitative approach/Determinacion del sexo en mandibulas en el primer ano de vida mediante una aproximacion cuantitativa.
The difficulty to determine sex of individuals in children bone remnants is a known problem that limits the anthropological investigations and forensic practice. Several methods have been described for sex diagnosis from postcranial skeleton, particularly the hip bone.
Merrot et al. (2001) used 500 x-ray images of the pelvis of stillborn fetuses and determined that the interischiatic tuberosity distance was a good indicator of sexual dimorphism from 26 week of intra-uterine life. In another study Holcomb & Konigsberg (1995) analyzed the greater isquiatic notch of human term fetuses and found sexual dimorphism in shape, but not in dimensions, so the usage of the quantitative parameter was questioned as an indicator of sex in fetuses. In contrast, Schutkowski (1993) has reported that men exhibited a greater isquiatic notch closer and deeper than women. These indicators, along with the more prominent chin and the width of dental arch allow to correctly classify 70-90% subjects between 0 and 5 years old.
The mesiodistal and bucolingual crown dimensions of teeth have also been studied for sex determination in subadults individuals. Cardoso (2008) indicates that, for both adult and subadults, the canines are the pieces that have greater sexual dimorphism. For Rosing (1983), the teeth are only one of the elements that are developed with the adult size and that his dimorphic morphological character is maintained over time.
The mandible also seems to be useful for sex classification in immature skeletons. Loth & Hennenberg (2001) described a simple, qualitative method for sex differentiation in subadults' mandibules through shape analysis of the mandibular body with 81% accuracy. These results were discussed by Coqueugniot et al. (2002), who performed a similar study obtaining lower accuracy levels. Subsequently, Suazo et al. (2008a) developed a study with a sample of Brazilian mandibles and reported accuracy levels between 57.5 and 60.5% for sex determination, with greater sensitivity for determining male, and conclude that it is necessary to carefully evaluate the methods of sex determination from subadults mandibles in specific populations.
Considering this background, the goal of this study is to determine several dimensions of mandibles in a sample of Brazilian children in the first year of life and analyze the reliability of these parameters in sex determination with forensic purposes.
MATERIAL AND METHOD
We used 32 mandibles of Brazilian children between 0 and 1 year-old, 20 males and 12 females. The mandibles belong to the Skull Museum collection of the Morphology and Genetics Department, Universidade Federal de Sao Paulo (UNIFESP), Brasil.
The mandibles were separated from the skull, without morphological alterations and no evidence of trauma. Using a digital caliper (0.01mm) the following measurements were taken:
- Bicondilar width: Distance between the lateral poles of the right and left mandibular head.
- Bigonial width: Distance between the right and left mandibular angle.
- Minimum width of the mandibular ramus: Minimum distance between the anterior and posterior edge of the mandibular ramus.
- Height of the mandibular ramus: distance between the deepest point of the mandibular incisure and the deepest part of the antegonial incisure, is measured in the right and left mandibular ramus.
- Gonion-gnation length: Distance between the mandibular angle and the lowest point of the mandibule in the anterior median line. It is measured from the right and left mandibular angle.
- Height of the mandible: Maximum length of the mandibular median line.
- Transverse dimension of the mandibular head: Distance between lateral pole and medial pole of the mandibular head. It is measured on the right and left side.
- Anteroposterior dimension of the mandibular head: maximum distance between the anterior and posterior face of the mandibular head, measured at right and left sides.
For some mandibles, difficult or doubtful measurements were excluded and only the data obtained were submitted to the t test for independent samples, p <0.05 and discriminant function analysis with SPSS 15.0.
The twelve linear dimensions were analyzed in a sample of 32 mandibles. Due to advanced erosion in one of the mandibles, it was not possible to obtain the measurement of the left mandibular ramus minimum width. In other three male mandibles it was not possible to determine the maximum anteroposterior diameter and the maximum transverse mandibular head.
Most of the measured dimensions were greater in male, except for the minimum width of the left and right mandibular ramus and maximum transverse diameter of the right mandibular. However, none of the differences was statistically significant, meaning that the discriminant analysis procedure was negative. This is verified by the high values of the Lambda Wilks statistics.
The analyzed parameters and statistic analysis are shown in Table I.
To determine the gender of immature skeletons, hip, mandible and teeth seem to be the most useful elements.
The dimorphic traits in children's mandibles, described by Loth & Henneberg, allow the correct classification of a large number of cases, but are likely to present a population-specific behavior, which may explain the lower accuracy of subsequent studies.
On the other hand, the literature generally assumes that the objective assessment of the skeletal remnants through metric comparisons allows us to obtain better statistical standards of accuracy for age determination and sex diagnosis in forensic and anthropological sciences.
The present study analyzed a series of linear dimensions in children's mandibles and concluded that, despite certain differences, no precise dimorphism could be verified concerning mandible size in the analyzed sample. These findings are consistent with those reported by Franklin et al. (2007), who have used geometric morphometry method on 38 landmarks and have concluded that no sexual dimorphism can be determined in subadults mandibles.
Much higher accuracy indexes (70-90% accuracy) were obtained by Schutkowski, who has conducted a combined metric analysis from different parts of the skeleton, including the mandible. However, whenever the skeleton remains are not complete and assessment must be made from the mandible only, our results recommend the use of a non-metric or qualitative analysis for the diagnosis of sex in subadults, this is also applied when specific populations' skeletal remainders exist or in those that one suspects of nutritional alterations (Suazo et al., 2008b, 2008c).
In conclusion, mandibles in the first year of life present little sexual dimorphism and is a quantitative approach seems not to be the best tool for sex identification with forensic purposes.
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Suazo, G. I. C.; Zavando, M. D. A. & Smith, R. L. Evaluating accuracy and precision in Morphologic traits for sexual dimorphism in malnutrition human skull: A comparative study. Int. J. Morphol., 26(4):876-83, 2008b.
Suazo, G. I. C.; Zavando, M. D. A. & Smith, R. L. Sex determination using mastoid process measurements in Brazilian skulls. Int. J. Morphol., 26(4):941-4, 2008c.
*, ** Ivan Claudio Suazo Galdames; ** Daniela Alejandra Zavando Matamala & ** Ricardo Luiz Smith
* Departamento de Anatomia Normal, Universidad de Talca, Chile
** Departamento de Morfologia y Genetica. Universidade Federal de Sao Paulo, Brasil.
Correspondence to: Prof. Dr. Ivan Suazo Galdames
Departamento de Anatomia Normal
Universidad de Talca
Avenida Lircay s/n. Oficina No 104
Table 1. Descriptive statistics, and p value of Wilks' lambda of the linear dimensions analyzed in 32 mandibles of children aged between 0 and 1 year old of the collection of UNIFESP. Sex n Mean SD * B icondilar width Male 20 63.1350 6.92755 Female 12 63.1275 8.27786 * B igonial width Male 20 50.4790 6.83989 Female 12 49.1158 6.57738 * H eight of the right mandibular Male 20 19.2510 3.96959 ramus Female 12 18.2325 3.26029 * H eight of the left mandibular Male 20 18.8530 3.84045 ramus Female 12 18.0408 3.28720 * M inimum width of the right Male 19 16.9611 2.38965 mandibular ramus Female 12 17.1700 2.56457 * M inimum width of the left Male 19 17.1247 2.31920 mandibular ramus Female 12 17.2933 2.35827 * R ight gonion-gnation Male 20 40.1245 5.37346 Female 12 38.5642 5.60068 * L eft gonion-gnation Male 20 38.9930 5.37810 Female 12 38.2550 5.33035 * T ransverse dimension of the Male 19 9.0995 1.46108 rigth mandibular head Female 12 9.2633 1.34999 * T ransverse dimension of the Male 20 9.2180 1.60052 left mandibular head Female 12 9.0008 1.21001 * A nteroposterior dimension of Male 18 5.4917 .77062 the right mandibular head Female 12 5.4425 .77879 * A nteroposterior dimension of Male 19 5.8226 .74800 the left mandibular head Female 12 5.5325 .83567 * H eight of the mandible Male 20 13.678 2.6423 Female 12 12.991 2.6479 Wilks' Sex Sig. lambda * B icondilar width Male Female .998 .999 * B igonial width Male Female .584 .994 * H eight of the right mandibular Male ramus Female .460 .978 * H eight of the left mandibular Male ramus Female .547 .990 * M inimum width of the right Male mandibular ramus Female .819 .996 * M inimum width of the left Male mandibular ramus Female .846 .998 * R ight gonion-gnation Male Female .440 .986 * L eft gonion-gnation Male Female .709 .997 * T ransverse dimension of the Male rigth mandibular head Female .757 .993 * T ransverse dimension of the Male left mandibular head Female .689 .999 * A nteroposterior dimension of Male the right mandibular head Female .866 .999 * A nteroposterior dimension of Male the left mandibular head Female .323 .973 * H eight of the mandible Male Female .482 .990