Sexual dimorphism of canine volume: A pilot study
Introduction
Sex assessment has a relevant importance in the reconstruction of the biological profile of human remains, and literature provide several methods for reaching a correct diagnosis on the base of different bodily districts, mainly the pubis and cranium [1]. However, both in the forensic practice and archaeological context as well it is not uncommon to recover human remains where these structures are no longer appreciable, for example because of extreme fragmentation or carbonization of the skeleton. In addition, in these cases genetic tests often are not able to produce a reliable profile because of high DNA degradation [2]. From this point of view teeth may provide a relevant contribution, not only to personal identification [3], but also to the diagnosis of sex, thanks to their dimorphism and resistance to taphonomic effects. In literature, canines are known to show the highest degree of dimorphism [4], as also confirmed by several studies performed on different populations [5], [6]: in human evolution, canine sexual dimorphism (CSD) has been already known, as it is critical for interpreting the developmental biology, socioecology and phylogenetic position of primate groups, since this phenomenon is absent to weak in extant prosimians [7]. From a forensic point of view, the dimorphism of canine may provide a help to diagnosis of sex, and several authors have analyzed and verified the statistically significant differences of linear metrical indications and ratios between males and females [4], [8], [9], [10], although the last ones proved to be less reliable than single measurements [4], [11], [12]. Very few studies deal with the area of teeth, and found that the relative dentin-pulp area of canines and first premolars shows high levels of sexual dimorphism [13]. At the moment, only two studies have so far taken into consideration the sexual dimorphism of teeth volume: the first one was performed on mandibular central incisors and on a sample of 5–6 year old children, where no statistically significant differences were found according to sex [14]. The second one by Tardivo et al. ascertained a sexual dimorphism of mandibular canine volumes and provided a formula for assessing age, given the volume of the tooth in mm3 [15]. However the authors do not provide a formula also for the upper canines.
In the last years more and more technologies have been introduced, able to record 3D volume of items and biological material as well: some examples are cone beam CT-scan [16] and laser scanner [17], which have begun in the last years to being applied also to the forensic scenario, although in other fields of research than the diagnosis of sex. Therefore the chances to improve new methods applicable to the forensic context and based on the analysis of teeth volume is worth being taken into consideration.
This study aims at confirming the existing data concerning sexual dimorphism of upper canine volumes, analyzing also other indices such as the pulp chamber volume and the ratio between pulp chamber and dental volume, in order to improve a novel method for the diagnosis of sex.
Section snippets
Materials and methods
A sample of 87 patients (41 males and 46 females, aged between 15 and 83 years) underwent to CBCT (cone beam computerized tomography) for clinical reasons not dependant upon the present study, using a i-Cat Next Generation (Imaging Sciences International, Hatfield, Pa) with the same settings for each subject (voxel size: 0.4 mm; scan time: 8.9 s; scan width: 23.2 cm; scan height: 17 cm). Exclusion criteria were the presence of oral pathologies, facial and oral deformities and systemic diseases. Once
Results
Data concerning dental volume and pulp chamber volume are shown in Table 1 and Fig. 2. The mean dental volume amounted to 0.745 cm3 (SD 0.126 cm3) in males, 0.551 cm3 (SD 0.130 cm3) in females; the mean pulp chamber volume was 0.029 cm3 (SD 0.011 cm3) in males, 0.022 cm3 (SD 0.012 cm3) in females. The mean percentage ratio between pulp chamber and tooth was the same in males and females (3.9%, with a standard deviation of 1.3% in males, 1.7% in females). Among all the measurements, only the dental
Discussion
Sexual dimorphism of teeth is a well known phenomenon, widely analyzed also from the genetic point of view. Literature report that Y chromosome influences dental growth by promoting both amelogenesis and dentinogenesis by enhancing mitotic activity in tooth germs with a consequent higher dentine thickness in males [18], [19]. Amelogenin genes, which is present on both X and Y chromosomes, is implicated in tooth size dimorphism [20], whereas modifications of sex hormones have a more limited
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