Facial approximation: Soft tissue thickness values for Caucasian males using cone beam computer tomography

Global facial soft tissue thicknesses for craniofacial identification (2023): a review of 140 years of data since Welcker's first study

This year (2023) marks 140 years since the first publication of a facial soft tissue thickness (FSTT) study. Since 1883, a total of 139 studies have been published, collectively tallying > 220,000 tissue thickness measurements of > 19,500 adults. In just the last 5-years, 33 FSTT studies have been conducted. Herein, we add these data (plus an additional 20 studies) to the 2018 T-Table to provide an update of > 81,000 new datapoints to the global tallied facial soft tissue depths table. In contrast to the original 2008 T-Table, some notable changes are as follows: increased FSTTs by 3 mm at infra second molar (ecm2-iM2'), 2.5 mm at gonion (go-go'), 2 mm at mid-ramus (mr-mr'), and 1.5 mm at zygion (zy-zy'). Rolling grand means indicate that stable values have been attained for all nine median FSTT landmarks, while six out of nine bilateral landmarks continue to show ongoing fluctuations, indicating further data collection at these landmarks holds value. When used as point estimators for individuals with known values across 24 landmarks (i.e., C-Table data), the updated grand means produce slightly less estimation error than the 2018 T-Table means (3.5 mm versus 3.6 mm, respectively). Future efforts to produce less noisy datasets (i.e., reduce measurement and sampling errors as much as possible between studies) would be useful.

Facial soft tissue thickness measurement method and relationship with BMI, age and sex

INTRODUCTION

Facial aesthetics results from the harmony of various components of the craniofacial region, a structure whose physiognomy and topography are determined by a set of hard and soft tissues. Few works in the literature have investigated the relationship between the variables of sex, age, BMI and soft tissue thickness and have considered how these variables may influence operative outcomes. The purpose of this study is to increase the pre-operative knowledge of the thickness of the soft tissues of the face through an analysis of their measurement conducted on cone beam computed tomography (CBCT) and to investigate the impact that the variables of gender, age and BMI have on their determination.

MATERIALS AND METHODS

For this study 82 patients were recruited between January 2020 and January 2021 in the Department of Maxillofacial Surgery of the University of Naples "Federico II". A descriptive analysis of the sample was carried out on the selected sample, calculating averages and standard deviations for the individual variables analyzed.

RESULTS

BMI has a predominant role on some craniometric points while age and sex have a more marginal role. Our analysis shows that some points are affected by only one variable, BMI (G' N' PR' ID' SM' GN' PG' MIO' ACP' GO' ZY' SC' IC' ECMS' and MMB'); some points are affected by both BMI and gender (MP' and MR'); while only two (RHI' and MSO') are influenced by all the three variables.

CONCLUSION

A priori knowledge through CBCT of the thickness of the soft tissues of the face and a comparison with the data we propose could provide the surgeon with advance notice of the characteristics of the tissues which she/he will encounter.

Facial soft tissue thickness in forensic facial reconstruction: Impact of regional differences in Brazil

Forensic facial reconstruction aims to assemble and provide the appearance of a face over a skull, in order to lead to recognition of that individual, making possible the application of primary identification methods. The scientific literature presents facial soft tissue thickness (FSTT) tables for reference from a range of different geographic regions. However, the consensus on its importance or on how to use specific population data related to FSTT is not unanimous. Brazil is formed by geographic regions with diverse populations, which are reflected in facial features. This paper aimed to measure and compare FSTT of distinct Brazilian samples to ascertain the need for specific data sets for different regions. A specific protocol for cone beam computed tomography was used to standardize measurement, and it was applied in a sample of 101 subjects. The FSTT measurements of a Brazilian population from the Midwest Region was compared to a previous sample from Southeast, which was collected using the same protocol. High compatibility was observed when comparing the averages of FSTT among samples of these two different geographic regions. Regarding age groups, notable differences on the medium and inferior face were observed in females. Minor variances found are unlikely to affect the practice of forensic facial reconstruction. Facial features, such as eyes, lips, nose, and skin may also be relevant in the differentiation of people from these two areas in Brazil. Therefore, concerning the Southeast and Midwest Brazilian regions, the need to apply different data sets is unnecessary.

The development and testing of Thai facial soft tissue thickness data in three-dimensional computerized forensic facial reconstruction

Forensic facial reconstruction is a useful tool to assist the public in recognizing human remains, leading to positive forensic investigation outcomes. To reproduce a virtual face, facial soft tissue thickness is one of the major guidelines to reach the accuracy and reliability for three-dimensional computerized facial reconstruction, a method that is making a significant contribution to improving forensic investigation and identification. This study aimed to develop a facial soft tissue thickness dataset for a Thai population, and test its reliability in the context of facial reconstruction. Three-dimensional facial reconstruction was conducted on four skulls (2 males and 2 females, with ages ranging between 51 to 60 years). Two main tools of three-dimensional computer animation and modeling software-Blender and Autodesk Maya-were used to rebuild the three-dimensional virtual face. The three-dimensional coordinate (x, y, z) cutaneous landmarks on the mesh templates were aligned homologous to the facial soft tissue thickness markers on the three-dimensional skull model. The final three-dimensional virtual face was compared to the target frontal photograph using face pool comparison. Four three-dimensional virtual faces were matched at low to moderate levels, ranging from 30% to 70% accuracy. These results demonstrate that the facial soft tissue thickness database of a Thai population applied in this study could be useful for three-dimensional computerized facial reconstruction purposes.

Lip morphology estimation models based on three-dimensional images in a modern adult population from China

Lips are the main part of the lower facial soft tissue and are vital to forensic facial approximation (FFA). Facial soft tissue thickness (FSTT) and linear measurements in three dimensions are used in the quantitative analysis of lip morphology. With most FSTT analysis methods, the surface of soft tissue is unexplicit. Our study aimed to determine FSTT and explore the relationship between the hard and soft tissues of lips in different skeletal occlusions based on cone-beam CT (CBCT) and 3dMD images in a Chinese population. The FSTT of 11 landmarks in CBCT and 29 lip measurements in CBCT and 3dMD of 180 healthy Chinese individuals (90 males, 90 females) between 18 and 30 years were analyzed. The subjects were randomly divided into two groups with different skeletal occlusions distributed equally: 156 subjects in the experimental group to establish the prediction regression formulae of lip morphology and 24 subjects in the test group to assess the accuracy of the formulae. The results indicated that FSTT in the lower lip region varied among different skeletal occlusions. Furthermore, sex discrepancy was noted in the FSTT in midline landmarks and linear measurements. Measurements showing the highest correlation between soft and hard tissues were between total upper lip height and Ns-Pr (0.563 in males, 0.651 in females). The stepwise multiple regression equations were verified to be reliable with an average error of 1.246 mm. The method of combining CBCT with 3dMD provides a new perspective in predicting lip morphology and expands the database for FFA.

Facial soft tissue depth measurements in cone-beam computed tomography: A study of a Brazilian sample

Forensic facial reconstruction (approximation) (FFR) is an aid to human identification when no presumed identity is available. It is based on average soft tissue thickness (STT) applied onto a skull. These averages vary at each landmark according to sex, ancestry, and Facial Growth Patterns (FGP). To obtain the reference, there are different protocols and conditions, such as needles in cadavers, ultrasound, magnetic resonance, and computer tomography. Using cone-beam computed tomography (CBCT), landmark placement and direction of measurement are critical. The purpose of this article is to detailly describe a method for STT measurement in CBCT DICOM files and to test it in the analysis of a multi-ancestral Brazilian sample, subdivided into sex, age and FGP. A sample of 100 (50 male and 50 female) CBCT exams were selected and the volume was primarily been repositioned to cephalometric standards. A detailed description of the location and measurement direction of 32 landmarks was provided and granted good reproducibility of the measurements. The averages were assessed by sex, age, and FGP. There were significant differences between males and females. The CBCT measuring protocol provided standardization of measurements and is a method to be used in future researches. Advantages of CBCT, such as the subject's upright position and adjustable volume positioning, also justify its usage. Limited differences of STT were related to age and FGP. The updated Brazilian soft tissue thickness chart is a reliable source of data for forensic and clinical purposes.

Soft-tissue thickness values using cone beam computed tomography: A literature review

When human remains are found, with no evidence of identity, facial approximation can be a useful technique to employ. The reconstruction of the ante-mortem appearance can reproduce the likely features of the face, starting from the skull, based on the overlying soft-tissue thickness. Over the years, many techniques have been developed to achieve soft-tissue thickness measurements, one of which is based on the use of cone beam computed tomography. This study aimed to review the status of this technique and to evaluate heterogeneity among studies undertaken in this field, with particular regard to determination of landmarks, sex and body mass index.

Soft Tissue Thickness Variations of the Nose: A Radiological Study

BACKGROUND

Soft tissue thickness (STT) is a major factor affecting the outcome in rhinoplasty. However, limited information is found in the literature on the age- and gender-related variations of the nasal STT.

OBJECTIVES

The purpose of this study was to measure STT at various landmarks over the nasal framework and compare the age- and gender-related differences.

METHODS

STT measurements were made at 11 landmarks in 325 patients by employing magnetic resonance imaging. Patients were divided into subgroups to compare the STT differences between female and male and between the age groups as young, middle age, and elderly.

RESULTS

Soft tissue was thickest at the nasion and thinnest at the rhinion. The soft tissue coverage was significantly thicker in the male population at the supratip, tip, nasal bones, upper lateral cartilages, and alar lobules, whereas it is thicker in females at the rhinion. Average thickness of the soft tissues over the entire nasal framework increases with age except the rhinion.

CONCLUSIONS

The STT is variable over different parts of the osteocartilaginous framework. Gender and age influence the STT. The soft tissue is thicker at the distal half of the nose in male patients, and these areas become gradually thicker with age, whereas the soft tissue over the midvault becomes thinner. Increasing age presents a particular challenge to achieve predictable results in rhinoplasty, and an understanding of the soft tissue envelope allows for improved aesthetic outcome.

LEVEL OF EVIDENCE 2