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University of São Paulo: Research investigates regional differences to improve forensic facial reconstruction

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Forensic facial reconstruction is a method used to perform human identification in adverse situations, such as comparing the face before and after death. The technique consists of estimating the face of an individual, through dental characteristics replicated manually with modeling material or digitally through software, so that it can be recognized. “In both techniques, we use measurements of soft tissue thickness, obtained at specific points on the face, to outline the face, in addition to pre-established references of other facial attributes, such as eyes, nose, mouth and ears”, explains Deisy Satie. Moritsugui, Master in Forensic Dentistry and Public Health by the Postgraduate Program in Dental Sciences at FO.

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The different environmental characteristics of the Brazilian regions together with the different genetic formations of the population can influence the physical characteristics of each individual. Factors such as regional climate and heredity can lead to specific phenotypic formations, such as the structure of the face. To verify possible differences in facial soft tissue thickness (muscles, skin, blood vessels and any other structures that cover the skull) between populations in the Midwest and Southeast, a study by the Faculty of Dentistry (FO) of USP analyzed samples of these two Brazilian regions. The article, published in the scientific journal Plos One, concluded that – in this case – there is no need to apply different measures for the population of the analyzed regions, as no significant differences were found.

The objective of the study was to evaluate possible differences in facial soft tissue thickness in the Midwest and Southeast regions, to verify the need to use specific measures for each region. “We compared the thickness of the soft tissue of the face of samples obtained in the two regions and found many similarities between them”, says Deisy. Thickness is an important indicator to aid in the manual reconstruction of the face, showing the amount of soft tissue present at specific points. These measurements, in addition to pre-established references of other facial structures, are responsible for giving the face contour in the reconstruction.

Forensic anthropological examination

The facial soft tissue thickness measurements used are selected from a table of mean values. The choice of table to be used in face reconstruction is based on an anthropological examination, which investigates the characteristics related to the craniofacial biotype, age estimation and determination of the biological sex of the analyzed face. “For the Midwest and Southeast regions, the use of a single table can be used, since the comparison revealed great compatibility between the measures”, explains Deisy.

In addition to comparing the two regions, age groups (18 to 30 years old, 31 to 40 years old and over 41 years old) and biological sex (male and female) were also analyzed. The research found a trend towards greater soft tissue thicknesses in male samples, as well as greater stability over the years. In females, there was a gradual decrease in measurements with advancing age.

The samples were obtained from databases of two radiology institutes in the Midwest region. The tests analyzed were initially performed by the participants for different clinical purposes; therefore, they were anonymized in order to preserve the confidentiality of the information.

The methodology used in the research consisted of a protocol for measuring the soft tissues of the face at craniometric points by means of cone-beam computed tomography. The study demonstrated that the protocol used is a highly reproducible tool and that it helps to standardize measurements of facial soft tissue thickness.

The work was carried out by the research group of the Laboratory of Anthropology and Forensic Dentistry at FO, whose coordinator is Professor Rodolfo Francisco Haltenhoff Melani, PhD in Forensic Dentistry and Deontology from the State University of Campinas (Unicamp).