Evaluation of fasial tissue thickness with computerized tomography in Turkish population

Introduction: Forensic Facial Reconstruction is a method used in the recreation of the facial appearance of unidentifiable bodies, which are extremely deformed and cannot be identified with common identification methods or individuals who have been missing for a long time. The aim of the three-dimensional facial reconstruction is to recreate the facial topography according to the differences in facial soft tissue thickness in specific anatomical reference points by considering factors such as gender, age and race. Moreover, facial soft tissue thickness values are expected to be accurate in order to achieve results with the highest resemblance to the actual face image while studies revealed that there are significant differences in facial soft tissue thickness between races. However, there is no standard facial soft tissue thickness table to increase the reliability of results in our country. Moreover, the tables of facial soft tissue measurement reference points employed in our country and in the world include various limitations. Through technological developments, recent methods such as cephalogram, ultrasonography, magnetic resonance and computarized tomography techniques have been employed for facial soft tissue thickness measurement. The measurement of facial soft tissue thickness by computarized tomography stands out as a reliable method because the result of a computarized tomography is as accurate as the ultrasonography and computarized tomography face images are transfered onto film as long term records for any remeasurement. In this study, it is aimed to contribute to the quantitative data pool and possible scale for facial reconstruction studies through determining facial soft tissue thickness of Turkish population measuring 20 anatomical reference points by computarized tomography and analyzing the features of individuals. Method: In addition to the approval of Bezmialem Vakıf University Ethical Committee For Non-invasive Clinical Studies dated 12/09/2017, no. 16/231, all procedures of this study were performed in accordance with the 1964 Helsinki Declaration and its later amendments. Sample group of this study was comprised of the subjects who applied to the Department of Radiology in Bezmialem Vakıf University Medical Faculty Health Practice and Research Center between 01/06/2017 and 31/12/2018 for a computed scan of the head and neck areas including the lower jaw. In the first step, 401 people were selected and contacted through the phone for their detailed individual features. The exclusion criteria were as follows: (1) age below 18 and above 70 (2) Body mass index out of the range of 20-25, (3) no chronic diseases resulting in any structural changes in facial tissue and (4) no history of trauma-operation. The subjects were carefully selected to comprise age groups with an even distribution and categorized into a total of 5 groups with the 1st group between ages 18-29, the second between 30-39, the third between 40-49, the forth between 50-59 and the fifth between 60-69. Because the hometown context is not a certain definition and it does not provide an accurate classification for the origin of race, the subjects were evaluated according to their hometowns just in the light of the information obtained on the phone, and categorised into separate groups based on seven geographical regions of Turkiye. The computarized tomography films of the 210 subjects (97 females, 113 males) conforming with the determined inclusion criteria of this study were retrospectively measured using Synapse system based on 20 anatomical reference points (Supraglabella, Glabella, Nasion, Rhinion, Mid-philtrum, Supradentale, Infradentale, Supramentale, Pogonion, Menton, Eminentia Frontalis, Margo Supraobitalis, Margo infraorbitalis, Orbitofrontalis lateralis, Arcus zygomaticus, Tuberculum supraglenoidale, Based on Gonion, Supra M2, Curvatura occlusalis, Supra M2) on the facial soft tissue. The data acquired through measurements were saved in the 2013 Microsoft Office Excel program. The data were transferred to IBM SPSS 20.0 (Statistical Package for Social Sciences, USA) software for the necessary analyzes. Mann-Whitney U, Kruskal-Wallis, Post-hoc test Dunn, non-parametric correlation tests and Z test were used in addition to the descriptive statistical analzes for the comparison the valid data. Statistical significance value was regarded as p<0.05. Findings: The comparison of the measurements based on the gender variable revealed that the 17 of the 20 reference points were statistically significant and the facial soft tissue thicknesses of the male subjects were higher than the female subjects at 18 of the points. The measurements were higher at the remaining two reference points (Orbitofrontalis lateralis, Arcus zygomaticus) in the female subjects, which was not statistically significant. The evaluation based on the age variable revealed that the tissue thicknesses increased with age together at five points in the male subjects; at eight points in the female subjects; decreased at one point in the male subjects; and at one point (Mid-philtrum), it was noted that the tissue thickness in the female subjects decreased with age between 18-29, 30-39 age groups and 60-69 age group, which was statistically significant. The results revealed that the body mass index was correlated with all of the points with the least correlated point being mid-philtrum; there was no significant difference between the hometowns in the groups and our results were similar to the other studies in Turkey even though there were some significant differences between specific reference points, and there were significant differences between more than half of the reference points compared to the measurements obtained in Brasil, Taiwan and white America populations. Result; In this study, it has been determined that (1) the facial soft tissue thickness in the male subjects was higher compared to the female subjects, (2) changes on the topographical distribution of the facial soft tissue thickness occurred due to aging and total mean value could be interpreted to indicate the increase of facial soft tissue thickness due to aging despite the low number of reference points increasing together and weak statistical data support, (3) the body mass index and the facial soft tissue thickness were positively correlated, (4) the races could cause differences in facial soft tissue thicknesses, (5) the geographic regions could influence facial soft tissue thicknesses altough it could not proved statistically.