Dr. Mathew Thomas MaliaelBDS

Contents- Introduction

Aim and objectives

Age estimation

Sex determination

Frontal sinus pattern as an aid in identification

3D facial reconstruction from CBCT data

Advantages

Limitations

Conclusion

References

Introduction

Computed tomography is revolutionary imaging modality invented by Godfrey Hounsfield in 1972.

Cone beam computed tomography is a modification of computed tomography introduced into clinical practice in the 1990s.

Cone beam computed tomography has become a popular and frequently used imaging modality.

The principal feature of CBCT is that multiple plane projections are acquired by rotational scan to produce a volumetric dataset from which inter-relational images can be generated

In a single rotation the region of interest is scanned by cone-shaped x ray beam.

Digitised information of objects in the region of interest such as shape and density is acquired from multiple plane angle.

The imaging data is then processed by special imaging software that reconstructs topographic images of the region of interest in multiple anatomic planes.

Aim and Objectives

This review highlights the importance and limitations of CBCT application in field of forensic science by examining the available evidence from clinical and scientific literature pertaining to forensic dentistry.

My paper will be limited to :-

1. Age estimation

2. Sex determination

3. Frontal sinus pattern as an aid in forensic identification

4. 3D Facial reconstruction

Age Estimation

Estimation of age is important in forensic sciences as a way to establish the identity of human remains.

Of the various parts of the body used in age estimation, teeth are the least affected by the taphonomic process. Their durability means that they are sometimes the only body part available for study.

Generally 2D radiographs are used to assess the age but the primary disadvantage of radiographs is that they are two-dimensional projections which are subject to considerable magnification and distortional errors.

CBCT helps to overcome this disadvantage by permitting a simultaneous assessment of the mesio-distal and bucco-lingual dimensions of teeth.

CBCT images can also be reformatted to conventional 2D radiographic views.

The major disadvantages are:-

CBCT images might be subject to artefacts due to the presence of metallic restorations or implants.

CBCT images are also susceptible to motion artefact.

REVIEW OF LITERATURE

N. Jagannathan et al conducted a study on 140 individuals (aged ten - 70 years). Cone beam computed tomography was used to measure pulp and tooth volumes of the study group. The age of the study group was estimated with a mean absolute error that was found to be 8.54 years.

Reformatted CBCT images can be used to estimate age using the method proposed by Kvaal et al. Studies conducted by Piyush G. Limdiwala and J.S. Shah revealed that the age could be assessed with an error of 8.3 years.

Shi et al, in their study, concluded that segmentation of individual vertebrae was possible using CBCT volumetric datasets. This helps in the visualization of cervical vertebral morphology and holds potential in skeletal age assessment.

Sex Determination Subsequent to drastic events such as natural disasters,

outbreak of wars or air traffic accidents, positive identification of victim’s gender becomes, perhaps, the most difficult task to encountered in forensics.

Sexual dimorphism can be evaluated from anthropometric measurements obtained from CBCT scan.

Bone measurements varies in different population hence further studies in different populations to further enhance the ability of this method.

REVIEW OF LITERATURE

Amin W et al conducted the Osteometric analysis of mastoids on 192 Jordanian adults .

The study identified four parameters that can be used to determine sex accurately – IMD , MS , MMCA , ML.

Based on the statistical analysis of these parameters the sex of the subject was determined with an accuracy 90.6%.

In another study conducted by Dilhan İlgüy et al on 161 adults , the sex was determined using craniometric measurements of the foramen magnum and mandible obtained from CBCT scans.

The study determined that the gonial angle (G-angle) , ramus length (Ramus-L), gonion–gnathion length (G–G-L) , bigonial breadth (BG-Br) and sagittal diameter of the foramen magnum could be used as reliable predictors of sex.

The sexes of the subjects was determined with an accuracy of 83.2%.

Frontal Sinus Pattern As An Aid In Identification

Human identification is not a difficult task, when it is about a live individual or a cadaver chronologically recent and intact. However, when there is not a complete skeleton, but a group of bones, the identification process becomes progressively harder and sometimes impossible to be accomplished.

The frontal sinuses can provide significant evidence for forensic identification.

The irregular forms of the frontal sinuses, initially observed in anterior-posterior radiographs have been extensively studied and it has been proven that there are not two people with the same frontal sinuses, even being monozygotic twins.

The comparison of frontal sinus images by cone-beam computed tomography can be used as an additional method in the identification process, providing the expert with a greater reliability .

Some shortcomings can be listed regarding this method:-

1. Subjectivity, dependence on the professional expertise .

2. Secondarily, the radiographic image can be significantly changed according to the incidence of the X-rays beam

REVIEW OF LITERATURE

A study conducted by Maria Priscilla David et al on a study group of 50 individuals determined that the frontal sinus had considerable individual variation and could serve as an adjunct in forensic identification.

A literature review by Jeidson Antonio Morais Marques et al concluded that the comparison of frontal sinus images by cone-beam computed tomography can be used as an additional method in the identification process, providing the expert with greater reliability.

3D facial reconstruction from CBCT data

3D imaging is becoming more relevant in all aspects of human life and substantial effort is spend for the models regarding the human body.

CBCT scan data is usually preferred for 3D reconstruction in dentistry.

Using the data obtained from CBCT

The reconstructed image can be used for forensic identification.

This method is still under perfection trials and research to improve its efficiency and accuracy.

►One of the major disadvantages with this technique is noisiness of scanned image owing to its low radiation dose

►Another major drawback is the introduction of artefacts due to the presence of metallic restorations this results in resolution and detail deficiencies.

►Motion artefact also creates problems in the images.

REVIEW OF LITERATURE

A study conducted by IEEE members tried different algorithms to overcome the drawbacks of CBCT images and to obtain an efficient and feasible method to develop 3D reconstructed models.

Advantages Forensically relevant information could be recorded rapidly

either within a specialist mortuary or in a temporary mobile mortuary at a disaster scene.

Practical advantages include relatively small size, portability, and low cost. Technical advantages include good spatial resolution and metal artefact reduction.

The digital data could be sent electronically to odontologists remote from the scene for examination and archiving.

Conventional radiographic images could be reformatted from the CBCT data set for comparison with ante-mortem records.

Reduced body contact would be required with the potential to eliminate direct examination of the oral cavity.

The need for surgical resection of the jaws to facilitate dental examination in cases of body deterioration would be reduced

CBCT is a non invasive technique in forensic dentistry as compared with other techniques used in forensic dentistry.

Most CBCT machines allow operator to select the desired region of interest (FOV).

CBCT images can be acquired in few seconds .

Images are seen in multiplanar format. Three-dimensional reconstruction can be obtained with display from any angle.

Images are dimensionally accurate.

Limitations

CBCT is more expensive than conventional radiologic investigations .

CBCT images suffer from increased noise from radiation scattered in many directions.

Introduction of artefacts due to the beam getting scattered by metallic restorations and implants.

CBCT suffers from motion artefact when a patient moves during the scanning process .( It can be avoided by using head stabilizing devices but any movement affects the whole data set and the whole image rather than just one part).

Limitations include limited field size and limited soft tissue contrast .

Inconsistent quality due various factors.

Conclusion

Forensic odontologists are referred to for clarification by the judiciary on forensic matters . As crimes are become increasingly sophisticated , forensic methodology must keep up to the pace in the technology race. CBCT imaging can provide the much-needed 3D perspective in certain cases that require more information that is beyond the scope of the traditional methods. The use of this technology is yet limited owing to it’s recent introduction. There is a need for forensic odontologists to better understand the role and scope of this imaging modality in the practice. CBCT in future will prove to be a great tool and asset to the practice of forensic odontology.

REFERENCES- White S.C and Pharaoh M. J Oral Radiology 6th Edition.

N. Jagannathan et al ;AGE ESTIMATION IN AN INDIAN POPULATION USING PULP/TOOTH VOLUME RATIO OF MANDIBULAR CANINES OBTAINED FROM CONE BEAM COMPUTED TOMOGRAPHY ; (J Forensic Odontostomatol 2011;29:1:1-6)

3D Reconstruction from CBCT data- IEEE 978-1-4799-6821-3/14

Moazzam Jawaid et al ; THE ROLE OF CBCT IN FORENSIC DENTISTRY: A REVIEW ; / International Journal Of Advances In Case Reports, 2014;1(4):179-183

Amin W et al ;Osteometric Assessment of the Mastoids for Gender Determination in Jordanians by Discriminant Function Analysis; American Journal of Medical and Biological Research, 2015, Vol. 3, No. 4, 117-123

Jeidson Antonio Morais Marques et al ;Cone-beam Computed Tomography Analysis of the Frontal Sinus in Forensic Investigation; Int. J. Morphol., 32(2):660-665, 2014.

AS Forrest; Collection and recording of radiological information for forensic purposes ; Australian Dental Journal 2012; 57:(1 Suppl): 24–32

REFERENCES- Dilhan İlgüy et al ; Measurements of the Foramen Magnum and Mandible in Relation to Sex Using CBCT ; J

Forensic Sci, May 2014, Vol. 59, No. 3 doi: 10.1111/1556-4029.12376

Maria Priscilla David et al ; Use of frontal sinus and nasal septum patterns as an aid in personal identification: A digital radiographic pilot study ; Journal of Forensic Dental Sciences / July-December 2010 / Vol 2 / Issue 2

Piyush G. Limdiwala and J.S. Shah ; Age estimation by using dental radiographs ; Journal of Forensic Dental Sciences / July-December 2013 / Vol 5 /Issue 2

Michael Murphy et al ; Accuracy and Reliability of Cone Beam Computed Tomography of the Jaws for

Comparative Forensic Identification; J Forensic Sci, July 2012, Vol. 57, No. 4 doi: 10.1111/j.1556-4029.2012.02076.x

Bianaca S. Krus; 3D CBCT ANALYSIS OF THE FRONTAL SINUS AND ITS RELATIONSHIP TO FORENSIC IDENTIFICATION

Tanya Khaitan et al; Cone Beam Computed Tomography: A New Era in Maxillofacial Imaging; Int J Oral Health Med Res MAY- JUNE 2015 VOL 2

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