Facial Profile Approximation A Simplified Technique

Transcription

1 Research Article Facial Profile Approximation A Simplified Technique Authors 1 Dr. Amit K Nayar, 2 Dr. Gagandeep Thind Address for Correspondence: 1 Professor& H.O.D, Dept. of Oral Pathology & Microbiology, Swami Devi Dyal Hospital & Dental College, Haryana, India 2 Post- Graduate Student, Dept. of Oral Pathology & Microbiology, Swami Devi Dyal Hospital & Dental College, Haryana, India Abstract: Forensic odontology, of late is gaining increasing importance in criminal investigation. There has been a lot of interest of the use of facial reconstruction as a means of identification when other evidence is insufficient. Several 2D and 3D manual or computer-aided facial reconstruction techniques have been developed. Facial reconstruction however, is a time consuming, tedious procedure, and is often impractical due to the lack of proper data base and cost factor. Aim: To develop a simplified manual technique using the soft tissue thickness as determined by Lateral cephalograms to reconstruct a likeliness having close resemblance to the actual face. Material & method: 30 lateral cephalograms (15 males, 15 females) of local population will be traced and soft tissue depth at predetermined anatomical points will be recorded. Using this facial reconstruction will be attempted manually using clay to give an outline to the skull. Results: The comparison of individual soft tissue points with the mean values of all soft tissue points using paired t test did not show any significant variation. (p>0.05). a variation however, was seen between soft tissue thicknesses at individual points between males and females. Discussion: The soft tissue depths determined in this manner could be used to reconstruct the profile of subjects where only the skull is available. However, we emphasize that this is only a pilot study and needs to be validated further with a larger sample size. ijars/ Vol.I / Issue II /Sept-Nov, 2012/218 1

2 Introduction: The definite establishment of identity of a victim of crime or disaster has been a challenging task. Forensic Investigations are often based on the comparisons of antemortem and post-mortem data. However, in certain circumstances when the identifying features are lost due to skeletonisation, decomposition etc, it may be impossible to establish any link by simple comparison. In such cases, facial reconstruction remains the only possible way to establish the identity of the missing or deceased 1. Cranio-Facial Reconstruction, as a branch of Forensic Odontology, has opened a new dimension in the field of identification from skeletal remains. However, Facial reconstruction is still in its infancy, and at best, is very time consuming and expensive, thus making its use very limited. Several 2D and 3D, manual as well as computer aided techniques have been developed for this purpose 2. Manual methods of facial reconstruction require a great deal of anatomic knowledge as well as artistic modelling expertise. In addition, it is highly subjective, and personal preferences might lead to an erroneous reconstruction in spite of great effort. Numerous 2D and 3D computer-aided techniques have attempted to simplify the technique and lessen the time required for the same. It has the added advantage of being objective and thus more accurate. Most of the computer aided studies have been performed using complex softwares. The current study is an attempt to propose a simplified technique for the facial approximation using a readily available data. Lateral Cephalograms have been used to produce computer generated and soft tissue profiles from linked straight line segments 3. Materials and method A record of the lateral cephalograms of patients coming to a local diagnostic centre was taken for the study.the soft tissue profiles of 30 subjects in the age group 16 to 26 years (Male : 15; Females 15) were traced from their Digital lateral Cephalograms on the computer with the help of Dolphin Imaging Software. Determination of soft tissue points A total of 10 soft tissue points along the midline were selected based on their use in other studies and they have proven to be reliable. Also, these points were easy to locate in a standardized way. The soft tissue depth was predetermined at 10 anatomical points along the midline for each of the subjects and a mean average was calculated for males and females separately. An imaginary soft tissue profile was drawn using the mean values. The similarity and proximity of these two lines was studied to predict the reliabilty of the technique. ijars/ Vol.I / Issue II /Sept-Nov, 2012/218 2

3 Fig 1: Determination of soft tissue thickness at 10 predetermined anatomical points along the midline. Fig 2: Soft tissue depth determination by marking 10 predetermined points on the midline in a female subject. ijars/ Vol.I / Issue II /Sept-Nov, 2012/218 3

4 Fig 3: comparison between profiles traced by marking mean soft tissue thickness with the actual profile in a female subject. Fig 4: Soft tissue depth determination by marking 10 predetermined points on the midline in a male subject. Fig 5: comparison between profile traced by marking mean soft tissue thickness with the actual profile in a male subject. Statistical analysis The data obtained was subjected to statistical analysis using SPSS software version***.paired t test was used to obtain the comparison between the soft tissue points in males and females ijars/ Vol.I / Issue II /Sept-Nov, 2012/218 4

5 Results The comparison of individual soft tissue points with the mean values of all soft tissue points using paired t test did not show any significant variation. (p>0.05) (Table 1&2). t- test for equality of means between males and females showed a significant difference with soft tissue profiles being more accurate at certain points namely, pronasale, subnasale, labrale superior,labrale inferior and throat.(p>0.05) (Table 3). Table-1 T-Test-Males Gender One-Sample Test t df Test Value = 0 Sig. (2- tailed) Mean 95% Confidence Interval of the Lower Upper M DIFFGLAB M DIFFNASION M DIFFPRONASALE M DIFFSUBNASALE M DIFFLABRALESUPERIOR M DIFFLABRALEINFERIOR M DIFFGNATHION M DIFFPROGONION M DIFFMENTON M DIFFTHROAT Table 1: Comparison of individual soft tissue points with the mean values for males Table-2 T-Test-Females Gender One-Sample Test t df Test Value = 0 Sig. (2- tailed) Mean 95% Confidence Interval of the F DIFFGLAB F DIFFNASION F DIFFPRONASALE F DIFFSUBNASALE F DIFFLABRALESUPERIOR F DIFFLABRALEINFERIOR F DIFFGNATHION F DIFFPROGONION F DIFFMENTON F DIFFTHROAT Table 2: Comparison of individual soft tissue points with the mean values for females ijars/ Vol.I / Issue II /Sept-Nov, 2012/218 5

6 Table-3 Comparison T-Test t df Independent Samples Test t-test for Equality of Means Sig. (2- tailed) Mean Std. Error 95% Confidence Interval of the Lower Upper GLABELLA NASION PRO NASALE ** SUB NASALE ** LABRALE SUPERIOR LABRALE INFERIOR ** ** POGONION GNATHION MENTON THROAT ** Table 3: Comparison of difference of mean soft tissue depth between males & females Discussion There have been attempts in the recent times to reconstruct the face digitally over an available skull. This is done by determining the soft tissue depths at various points on the face, of individuals in a particular community. These depths are then used as a guide to reconstruct the face. Traditionally, facial soft tissue depths have been measured using needle puncturing on cadavers. This was not an accurate method due to tissue deformation after post-mortem changes such as dehydration and shrinkage, as well as the deformation of tissue while puncturing 11. This was overcome by measuring the soft tissue depths at various points using Lateral cephalograms, Ultrasound 4, and CT scans 5. Maxime at al have recently attempted to reconstruct the face using 3D semi landmarks. The errors were minimized by reconstructing faces with ± 3 values. This is primarily possible because of the use of computers, as reconstruction of the face with ± values simply means entering a different value, and the reconstructed face with different values is available with almost no loss of time and capital. However, a cause for concern in this and other studies is the validity of the values of facial depths so obtained. We attempted to compare the soft tissue depths available on the lateral cephalogram and compare the mean so obtained with the actual soft tissue profile of the subject s photograph. As there was a significant similarity in the two profiles so compared, we suggested that the soft tissue depths determined in this manner could be used to reconstruct the profile of subjects where only the skull is available. However, we ijars/ Vol.I / Issue II /Sept-Nov, 2012/218 6

7 emphasize that this is only a pilot study and needs to be validated further with a larger sample size. Further, this may also assist studies of reconstruction of the entire face using soft tissue depths. Utsuno et al 6 reported significant differences in the soft tissue thickness between different skeletal malocclusions. They reported that the maximum difference was seen between class II and class III, with class I being intermediate. Furthermore, they suggested that mean values for different skeletal classes be used as required for more accurate results. The skeletal class of the skull can usually be determined on examination, and more accurately on the lateral cephalogram. Dumont reported Soft tissue thickness classified by dental occlusion only. Soft tissue depth variation with body weight and BMI was determined by Stabuck et al. Zacharias et al 7 have suggested that CBCT images can be used to derive accurate measurements that can form the basis for establishing a basis for soft tissue database for a certain population. Kim et al 8 performed a similar study with MRI. It is generally accepted that Facial reconstruction can be divided into four categories 1 (1) replacing and repositioning damaged or distorted soft tissues onto a skull; (2) the use of photographic transparencies and drawings in an identikit type system; (3) the technique of graphic, photographic or video superimposition; (4) plastic or 3-Dimensional reconstruction of a face over a skull, using modeling clay. It has also been pointed out that the term reproduction implies a perfect replication which cannot be a commitment. Facial approximation is perhaps a better description of the procedure but this term is not in general use. References: 1. Auslebrook WA, Iscan MY, Slabbert JH, Becker P, Superimposition and reconstruction in forensic facial reconstruction: a survey, Forensic Sci Int; 75 (2-3): 1995, Peter Claes, Dirk Vandermeulen, Sven De Greef, Guy Williams, John Gerald Clement, Paul Suetens, Computerized craniofacial reconstruction: Conceptual framework and review, Forensic Science International 201 (2010), G F Walker and C.J Kowalski., A two-dimensional coordinate method for the qualtification, description, analysis, prediction and simulation of craniofacial growth, Growth 35, 1971; Sven De Greef et al, Semi-automated Ultrasound facial soft tissue depth registration: method and validation, J Forensic Sci, Nov 2005, Vol 50 (6), Maxima Berar, Michel Desvignes, Gerard Bailly and Yohan Payan, 3D semi landmarks-based statistical reconstruction, Journal of Computing and Information Technology, 6. Utsuno et al, Pilot study of facial soft tissue thickness differences among 3 skeletal classes in Japanese population, Forensic Sci Int 195 (2010), 165.e1 165.e5. ijars/ Vol.I / Issue II /Sept-Nov, 2012/218 7

8 7. Zacharias Fourie, Janalt Damstra, Peter O. Gerritis, Yijin Ren, Accuracy and reliability of facial soft tissue depth measurements using cone beam computer tomography, Forensic Sci Int 199; 2010, D.K.Kim, A. Ruprecht, G. Wang, J.B.Lee, D.V. Dawson, M.W.Vannier, Accuracy of facial soft tissue thickness measurements in personal computer-based multiplanar reconstructed computed tomography images, Forensic Sci Int 155; 2005, ijars/ Vol.I / Issue II /Sept-Nov, 2012/218 8