Introduction
With the increase in crime, road accidents, and natural disasters, the use of forensic science has become essential to identify victims for moral reasons, to allow the family to mourn, and or for legal reasons (to establish the circumstances of the death and to define the rights of succession, insurance, inheritance)2.1, 2
The identification protocol generally includes two approaches (comparative and evaluative) depending on the nature of the ante-mortem and post-mortem elements.
In the absence of comparative data, identification is estimated or evaluative. It aims to define the person's biological profile by determining the victim's age, sex, stature, and biogeographical origin.
In terms of sex determination, DNA is the gold standard, with a sex prediction rate of up to 100%. However, its use may be limited in the case of heavily charred or fragmented skeletal remains and because of its high cost.
Morphoscopic (non-metric) and morphometric methods are used to predict sex. In the morphoscopic approach (visual assessment), the coxal bone is highly dimorphic due to the physiological changes that occur during childbirth in women, the forensic tool of choice. The skull, clavicle, and teeth are also used in its absence, with satisfactory results. Teeth show dimorphism about the size and morphology of the crown, especially in the canine.3, 4 Genetic factors, notably the Y chromosome, influence dental dimensions, which leads to a slower and longer enamel maturation process than the X chromosome.5 Environmental factors such as prenatal and postnatal diseases, diet, drugs used by the mother during pregnancy, and climatic differences also affect tooth morphology and structure.6
Brook and colleagues report that children with low birth weight had more enamel defects at a statistically significant level.7
Numerous studies of adults have shown that dental dimensions vary from one population to another and that teeth are sexually dimorphic.6, 7, 8
The forensic literature contains only a limited number of studies on dental dimensions in children.
The present study aimed to investigate tooth size and sexual dimorphism in the temporary dentition of Senegalese children.
Materials and methods
Materials
This descriptive study was carried out from March to July 2023 in the forensic odontology department of the Faculty of Medicine in Dakar. Two hundred dental casts were selected from 100 Senegalese children, including 50 boys and 50 girls aged between 4 and 10. An anonymization procedure was applied as soon as the sample was constituted. Only the sex of the participants was known. Subjects with severe crowding, caries, proximal wear, and restorations were excluded.
The dental casts selected were digitized in three dimensions using the Revopoint® 3D scanner (Figure 1).
In version 2022 of MeshLab, the mesio-distal and bucco-lingual diameters of the maxillary and mandibular canines and molars were measured.
Odontometric analysis
In MeshLab version 2022, measurements were taken on the mesiodistal and buccolingual diameters of the maxillary and mandibular canines and molars (Figure 2).
Measurements are taken on the diameters:
Mesiodistal diameter (MD) is defined as the most significant distance between the points of contact on the proximal surfaces of the dental crown
Buccolingual/palatal diameter (BL/BP) is the most significant distance between the crown's vestibular and lingual surfaces perpendicular to the tooth's mesiodistal diameter.
Intercanine distance is defined as the linear distance between the cusp tips of the canines on the right and left sides.
Statistical analysis
The data collected were recorded and processed in SPSS version 2019 software. A descriptive analysis was first performed. The relevance of certain factors was then tested using the Student's T-test. A significance level of P < 0.05 was used.9
Table 1
Mean and standard deviation mesiodistal and buccolingual/ palatal distance of the right and left maxillary canine.
Table 2
Mean and standard deviation of the mesiodistal and buccolingual distance of the maxillary and mandibular first molars, right and left.
Table 3
Mean and standard deviation mesiodistal and buccolingual distance of the maxillary and mandibular right and left second molar.
Mesio-distal (MD and bucco-lingual (VP; VL diameters)
Overall, the mean distances calculated were higher in boys than in girls. No significant difference was noted in the mesio-distal and buccolingual distances for the maxillary canines. However, a statistically significant difference was found for the mandibular canines for the buccolingual distance (Table 1).
Similarly, for the maxillary first temporary molar, the mean difference was more significant in the buccolingual distance (Table 2).
There was no statistically significant difference for the mandibular first temporary molar according to sex. All mesiodistal and buccolingual tooth diameters were found to be larger for boys than for girls (Table 3). Statistically significant differences were found between the sexes in the majority of teeth (except in the buccolingually distance).
Sexual dimorphism was better or more pronounced in the canines and the two-second molars.
Maxillary and mandibular inter-canine distance
In the maxilla, the mean value was 32.8 mm ± 2.81 in girls and 33.4 mm ± 2.80 in boys. There were no statistically significant differences.
The mean value of the mandibular inter-canine distance was 25.2 mm ± 2.48 in girls and 26.0 mm ± 2.52 in boys (Table 4).
Discussion
A person's biological profile is determined by age, stature, sex, and biogeographical origin. Determining the sex of a living person is pretty straightforward because of the development of secondary sexual characteristics. For a charred or skeletonized body, however, the task proves difficult. Morphometric and morphoscopic assessment of the skull, coxal bone, teeth, and even genetic analysis are necessary for sex determination.
In forensic odontology, dimensions are often used to assess sex. Studies carried out on permanent and temporary dentition confirm the existence of sexual dimorphism. Canines and molars are considered to be the most dimorphic teeth.10, 11
This dental study evaluated 200 dental casts of children aged between 4 and 10 years, scanned in 3D with the Revopoint Scanner.
The mesodistal and buccolingual diameters of the molars and temporary canines were measured, as were the distances between the canines.
The sample size used in this study (100 children) is within the average of studies in this field. Liu HH et al. and Yuen KK et al. worked with samples of 90 and 112 children, respectively.12, 13
Sex determination from teeth is essential at prepubertal age, as other sexual characteristics are not yet well developed. During this period, the crowns of the temporary teeth are fully formed.14 Overall, boys showed higher values than girls for all the distances measured. The mean value for the mesiodistal diameter of the right mandibular canine was 5.87 mm ± 0.376 in boys and 5.82 mm ± 0.428 in girls. In the buccolingual diameter, the mean diameter was 5.80 mm ± 0.409 in boys and 5.61 mm ± 0.404 in girls. T-test showed a significant difference in the buccolingual diameter (p < 0.041)
In contrast, on the left side, a statistically significant difference was found only in the mesiodistal diameter (P < 0.039).buccopalatal diameters.
The results of the study conducted by Singh et al. confirm the present study's findings. However, in their work, significant differences were found in the mesiodistal diameters of all temporary canines.15 The sexual dimorphism of the right mandibular canine has also been confirmed by research by Guemas J et al. Ingaleshwar P et al. have mainly highlighted a dimorphism in the mesiodistal and vestibule-lingual diameters with a significant difference for the maxillary and mandibular canines.16
For the mesiodistal diameter of the the mean value was 7.02 mm ± 0.474 in boys and 6.98 mm ± 0.486 in girls. In the buccolingual direction, the mean diameter was 8.73 mm ± 0.444 in boys and 8.47 mm ± 0.587 in girls. The only significant difference was in the buccomolar, the mean value of the mesiodistal diameter was 8.17 mm ± 0.504 in boys and 8.00 mm ± 0.569 in girls. In the buccolingual direction, the mean diameter was 7.37 mm ± 0.471 in boys and 7.25 mm ± 0.485 in girls. However, there was no significant difference between the mesiodistal and buccolingual diameters.For the right mandibular first molar, the mean mesiodistal diameter was 8.20 mm ± 0.572 in boys and 8.03 mm ± 0.526 in girls. In the buccolingual direction, the mean diameter was 7.30 mm ± 0.479 in boys and 7.31 mm ± 0.412 in girls. There was no significant difference between the sexes for these measurements.
Studies by J. Viciano et al. and Singh et al. confirm the results of the present study.17, 18 The results of the study by Shankar S et al. differ from ours, as they found a statistically significant difference for the mesiodistal diameter of the maxillary right first molar.18
Boys had higher mean values for the maxillary and mandibular second molars than girls. The mean mesiodistal diameter of the right maxillary molar was 9.28 mm ± 0.608 in boys and 9.06 mm ± 0.573 in girls. In the buccolingual direction, the mean diameter was 9.89 mm ± 0.552 in boys and 9.57 mm ± 0.652 in girls. There was a significant difference in buccolingual measurements (P < 0.001) but not in mesio-distal measurements.
For the upper left second molar the mean mesiodistal diameter was 9.27 mm ± 0.570 in boys and 8.99 mm ± 0.573 in girls. In the buccolingual direction, the mean diameter was 9.73 mm ± 0.477 in boys and 9.59 mm ± 0.60 in girls. mesiodistal and buccolingual diameters were more considerable in boys, with a significant difference in mesiodistal measurements (P < 0.033) but not in buccolingual measurements. In girls, the mean mesiodistal diameter of the left mandibular second molar was 10.01 mm ± 0.553, whereas it was 10.53 mm ± 0.570 in boys. In the buccolingual direction, the mean diameter was 9.06 mm ± 0.461 in girls and 9.17 mm ± 0.411 in boys. The mesiodistal and buccolingual diameters were larger in boys, with a significant difference in the mesiodistal measurements (P < 0.001), but not in the buccolingual measurements.molar was 10.36 mm ± 0.508 in boys and 9.87 mm ± 0.566 in girls. In the buccolingual direction, the mean diameter was 9.22 mm ± 0.471 in boys and 8.98 mm ± 0.461 in girls. The mesio-distal and vestibulo-lingual diameters were larger in boys, with a significant difference for mesio-distal (P < 0.001) and buccolingual (P < 0.013) measurements.
These results agree with those of S. Kondo et al., who showed that the mesiodistal and buccolingual diameters of the maxillary and mandibular second molars were higher in boys than in girls.19 The work of Margetts B et al. and Singh A et al. also confirms the results of this study.15, 20 There was no statistically significant difference between maxillary and mandibular inter-canine distance. Boys had a maxillary inter-canine distance of 33.4 mm ± 2.80 and girls 32.8 mm ± 2.81. The mean value of the mandibular inter-canine distance was 26.0 ± 2.52 in boys and 25.2 ± 2.48 in girls. Abu Alhaija et al., also obtained similar results for maxillary and mandibular inter-canine distance, which were greater in boys than in girls.21.
