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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.

INTRODUCTION

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.

RESULTS

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.

DISCUSSION

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.

REFERENCES

Cardoso, H. F. Sample-specific (universal) metric approaches for determining the sex of immature human skeletal remains using permanent tooth dimensions. J. Archaeol. Sci., 35:158-68, 2008.

Coqueugniot, H.; Giacobini, G. & Malerba, G. L'utilisation de caracteres morphologiques dans la diagnose sexuelle des mandibules d'enfants: application a la collection osteologique de Turin (Italie). Bull. mem. Soc. Anthropol. Paris, 14(1-2):131-9, 2002.

Franklin, D.; Oxnard, C. E.; O'Higgins, P. & Dadour, I. Sexual dimorphism in the subadult mandible: quantification using geometric morphometrics. J. Forensic Sci., 52:6-10, 2007.

Holcomb, S. M. & Konigsberg, L. W. Statistical study of sexual dimorphism in the human fetal sciatic notch. Am. J. Phys. Anthropol., 97:113-25, 1995.

Loth, S. R. & Henneberg, M. Sexually dimorphic mandibular morphology in the first few years of life. Am. J. Phys. Anthropol., 115:179-86, 2001.

Merrot, T.; Panuel, M.; Bourliere, B.; Kathia, C.; Philip, N. & Dutour, O. Expression of sexual dimorphism in the fetal pelvic girdle. C. R. Acad. Sci., 324:137-41, 2001.

Rosing, F. W. Sexing immature human skeletons. J. Hum. Evol., 12:149-55, 1983.

Schutkowski, H. Sex determination of infant and juvenile skeletons: I. Morphognostic features. Am. J. Phys. Anthropol., 90:199-205, 1993.

Suazo, G. I. C.; Zavando, M. D. A. & Smith, R. L. Blind test of mandibular morphology with sex indicator in subadult mandibles. Int. J. Morphol, 26(4):845-8, 2008a.

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

Talca--CHILE

Email: isuazo@utalca.cl

Received: 12-12-2008

Accepted: 08-01-2009
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
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Article Details
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Author:Galdames, Ivan Claudio Suazo; Matamala, Daniela Alejandra Zavando; Smith, Ricardo Luiz
Publication:International Journal of Morphology
Date:Mar 1, 2009
Words:1783
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