Role of dentomaxillofacial radiology in forensic dentistry

Abstract

Forensic dentistry is one of the important branches of forensic science and it is a branch which offers helpful information for the legal processes including identification of human remains along with age and sex determination. Dental forensic examination can involve the identification of a single individual or multiple individuals depending on the specific situation. Dentomaxillofacial radiology and radiological examination is a valuable tool for personal identification in forensic dentistry. Utilization of X-ray recordings are essential for many parameters related to identification since they shed light on many issues both in determining current conditions and in comparisons with the past. Comparing antemortem and postmortem radiographs taken from areas such as the skull or teeth is a reliable and objective method for identifying individuals. Radiographs and their proper preservation are crucial for present day assessments, historical comparisons and legal issues when necessary. While intraoral and extra oral radiographs were initially used in forensic dentistry, cone beam computed tomography application gained popularity in recent years. The use of radiology in forensic dentistry is not only necessary for identification, but also for age determination in mass casualties and disasters. The purpose of this mini-review is to provide information on the use of dental radiology in forensic dentistry.

Key Words: Dentomaxillofacial radiology; Forensic dentistry; Radiography; Diagnostic imaging; Dentistry

Core Tip: This paper discusses the basic concepts and approaches regarding dentomaxillofacial radiology in forensic dentistry. This article will shed light to applications and new trends regarding dentomaxillofacial radiology and its applications in this relatively important field of dentistry.

INTRODUCTION

Forensic odontology is the branch of dentistry that assists justice in identifying and establishing evidence, age determination and gender determination. In addition, it involves the medicolegal responsibilities of dentists by evaluating dental findings in forensic cases. Diagnostic and therapeutic examination and evaluation of injuries to the jaw, teeth, and soft oral tissues, along with injuries particularly in criminal investigations and/or mass disasters are within the scope of forensic dentistry. Moreover, identification, examination, and evaluation of bite marks, which are frequently seen in sexual assaults, child abuse cases, and self-defense situations are crucial for forensic odontological investigation[1,2]. Teeth are among the most resilient structures in the body and can maintain their structure for years by resisting numerous environmental factors. While dental characteristics can be decisive in identifying a person, the various metal and non-metal restorations and prosthetic conditions in the mouth are often important determinants of identity. Today, a wide variety of innovative radiologic equipment, chemical analysis of dental materials, and virtual simulations are crucial in identifying individuals[3]. Collection of X-ray data are essential for many parameters related to identification since they shed light on many issues both in determining current conditions and in comparisons with the past. The use of diagnostic imaging techniques in forensic dentistry is not only necessary for identification, but also for age determination in mass casualties and disasters for legal issues. However, reliability issues still exist in bite-mark analysis, reproducibility in radiologic evaluation, and in standardization of forensic imaging protocols for different tasks. Considering the wide variety of diagnostic imaging techniques and potential differences between these methods in terms of various tasks in forensic dentistry the purpose of this review is to provide information and critically analyze the role of dentomaxillofacial radiology in forensic dentistry[1-5].

IMAGING TECHNIQUES

Imaging techniques are important tools in forensic science. Radiologic applications date back to the early days of radiology and the discovery of X-rays by Röntgen in 1895. Their ability to reveal high anatomical detail and allow for multiparametric analysis of pathological changes significantly supports forensic investigations. With the development of medical devices and software in imaging technology, forensic radiology is becoming even more important. Many of the commonly used clinical imaging methods, including periapical and panoramic radiography, ultrasound imaging, multi-detector computed tomography (CT), cone-beam CT (CBCT), and magnetic resonance imaging (MRI), can be applied to forensic cases. Postmortem imaging applications have a wide range of applications and capabilities, from the simple localization of a radiopaque foreign body with a radiograph to the evaluation of a complex vascular injury with a postmortem angiogram[4,5].

UTILIZATION OF IMAGING IN FORENSIC DENTISTRY

Comparative identification of premortem and postmortem specimens using dental radiographs is a widely used method. When identification is necessary, it is important to examine antemortem radiographs for quality, type, content, and time of acquisition to create radiographs that mimic the areas of interest observed in antemortem images by using similar image geometry, appropriate exposure factors, and archival processing methods. This requires systematic labeling and positioning of images so that their identification as either postmortem or antemortem images is readily apparent. It is necessary to tabulate points of agreement by visually analyzing radiographs, taking into account ancillary information such as dental chart notes, dental models, and photographs. It is also important to identify points of disagreement between antemortem and postmortem radiographic examinations. The final stage of systematic evaluation is to determine whether the expert can make a positive or probable identification, or a negative assessment (i.e., no identification) based on the data obtained. Radiographic data provides objective evidence of anatomical conditions and past dental treatment performed on an individual. Radiographic evidence from dental restorations, root canal fillings, crowns, bridges, implants, extractions, etc., is used as common diagnostic points in the vast majority of comparative diagnostic cases[6]. If there is no evidence of dental work on the teeth, common anatomical structures are evaluated in ante-mortem and post-mortem radiographic examinations. This includes crown and root morphology, crown-root size and curvature, pulp morphology, and the spatial relationship between the teeth. Radiological evaluation on two-dimensional dental radiographs can be affected by factors such as projection geometry, magnification, and distortion. Small changes in horizontal or vertical irradiation angles can lead to significant differences. It is also important to remember that some anatomical structures may change over time. A technique comparing spatial relationships of dental structures in superimposed antemortem and postmortem radiographs was developed. Authors proposed a positioning device suitable for reproducing antemortem radiographic image geometry. Authors found that horizontal angular deviations approximately 5 degrees made identification difficult, whereas changes in vertical angulation had no effect. This procedure, and the positioning device used to accurately replicate antemortem image geometry was found to be a cost-effective method supporting dental identification[7].

Facial reconstruction is a technique based on skull interpretation that aims to reproduce individual facial features in order to describe the pre-mortem state. In cases where a skull reassembly is necessary it allows the contours of the soft tissues on the skull to be reconstructed, creating a face and increasing the likelihood of facial recognition. Computerized craniofacial forensic reconstructions have the advantages of improved visualization tools and transparency adjustments for displaying bone and skin. With advancements in medical imaging, digitizing the skull and transferring it to a computer used to be done with laser scanners, can now be performed with CT scanners and CBCT scanners. In traditional CT and MRI techniques, imaging is obtained in a supine position, which results in deformation of the facial soft tissue due to gravity. CBCT scanners, on the other hand, allow imaging in an upright position (standing), thus eliminating the negative effects of gravity[8,9].

In some cases, the skull is unrecognizable or cannot be visualized as a single piece, making it impossible to assess these structures. The frontal sinuses can be used in such cases because they tend to resist trauma. CT and CBCT scans provide images in axial, coronal, sagittal, and oblique directions, providing three-dimensional (3D) information about anatomical structures, and can also be used for 3D reconstruction. These reconstructions contribute to qualitative and quantitative morphological analysis, while volume and linear measurements of the sinuses can also be made. The imaging dose of CBCT is less than that of medical CT, making CBCT the preferred imaging modality for forensic evaluation of living individuals. Frontal sinus volume measurements have been found to be applicable to sex determination with reasonable accuracy. The use of the frontal sinus as a sex indicator complements other sex assessment methods, particularly in forensic studies where a relatively small portion of the skeleton can be examined[10].

Prenatal, neonatal, and postnatal age determination is achieved by prenatal radiographic evaluation of the jawbones and examination of tooth germs, which appear as radiolucent areas on premineralized radiographs. Age estimation methods such as the Kraus and Jordan technique, the Schour and Masseler method, the Mooree method, the Demirjian method, the Nolla technique, the Kvaal method, the Harris and Nortje method, and the Van Heerden method are well-established and widely accepted techniques that have been in use for a long time. Odontological age estimation methods are generally based on developmental, morphological, and biochemical dental changes. Analysis of dental development is particularly helpful in age determination in children and adolescents. Age determination in forensic medicine is important not only for identifying the deceased but also for living individuals. In living adults, skeletal development and dental maturation are complete. Therefore, the variety and applicability of age estimation methods are decreasing. Maxillofacial imaging for forensic age estimation in living adolescents and young adults remains a matter of debate[11-15]. In many studies, statistically significant inter-observer and intra-observer consistency has been reported, regardless of the method and measurement software used. This result demonstrates that using any of the methods is reproducible and applicable after adequate training. The use of dental radiology in age determination is feasible and yields valid results. Periapical or panoramic imaging may be the preferred radiological technique. The quality of the radiological technique does not affect the accuracy of the measurements, as long as the observer clearly observes the boundaries of the root canal and tooth surface. Therefore, whichever periapical or panoramic image meets the necessary conditions for measurement can be chosen[14,15]. Alignment and projection geometry issues in periapical and panoramic radiographs may have a negative impact on forensic evaluation. Researchers, clinically validated the use of a modified image receptor-holding device for the bitewing technique in order to repeat image alignment and obtain accurate radiographs. They introduced an innovative modified device which may be more comfortable and has the potential to reduce the proximal surface overlap than the traditional technique, especially in the premolar region[16]. The authors of another study produced a device with a simple design using commonly available commercial materials. The device can be easily installed on existing panoramic radiography equipment and provides superior radiographic quality by eliminating anatomical differences between antemortem and postmortem conditions. The widespread and effective use of the proposed skull positioning and fixation device and fabrication process in forensic odontological studies could increase the efficiency and accuracy of identification for unidentified deceased individuals[17].

Decrease in volume occurs due to the continued deposition of secondary dentin in the pulp space after tooth eruption. Secondary dentin deposition is an important morphological criterion for age estimation in adults. Panoramic and periapical radiographs are commonly used to calculate this ratio by using the pulp/tooth area ratio method. The main disadvantage of these traditional radiography techniques is that they introduce significant measurement errors due to projection geometry. With the widespread use of 3D images in clinical dentistry, the potential relationship between age and the ratio of pulp volume to total tooth volume has been investigated. CBCT provides true 3D imaging of teeth with submillimeter accuracy. A high correlation between the pulp-to-total tooth volume ratio and age in CBCT scans has been found in both sexes, particularly in the maxillary central incisors and maxillary lateral incisors[18,19]. Studies applying machine learning and artificial intelligence (AI) algorithms to develop optimized age estimation methods by using CBCT images are popular. In order to develop AI algorithms for age classification in forensic cases, it is suggested to examine different parameters derived from different measurement techniques in the data obtained from CBCT images[20].

Sexual dimorphism can be assessed by using anthropometric measurements on mandibular images obtained with CBCT. Six measurements (ramus length, gonion-gnathion length, minimum ramus width, gonial angle, bicondylar width, and bigonial width) are preferably used. Three of the six mandibular measurements were found to have higher mean values in male than in female: (1) Bicondylar width; (2) Gonial angle; and (3) Minimum ramus width[21].

In forensic odontology, anatomical models obtained through 3D modeling can be used as evidence collection, crime analysis, and research tools. One of the most important applications of 3D modeling in forensic odontology is bite mark analysis. Time is a crucial factor in bite mark evaluations. In human bites, healing can lead to distortion and loss of valuable information. Traditional bite mark analysis involves taking photographs to preserve the marks and using a plaster cast to record the bite mark's appearance. This method can cause tooth marks to become distorted due to external pressure. Using digital scanners to document bite marks eliminates any external pressure and the tendency for distortion. Digital scanning can be used to reconstruct entire bite marks using 3D printing. Digital scanning can be utilized for recording, documentation, and analysis in areas where reliable measurements cannot be obtained using traditional methods such as lip print patterns, tongue print patterns, palatal rugae patterns, fingerprints, and footprints. Bite marks can now be turned into more consistent evidence with CBCT. In addition, modern dentistry has made dental implants extremely important, unique identifiers for forensic evidence for human identification. The specialized designs of dental implants, such as holes, grooves, superstructures, and teeth visible only at specific rotations or angles, make them a unique forensic identification tool[22,23].

The greatest advantage of 3D printing is that it enables the non-invasive reconstruction of detailed anatomical structures, which can be used to conduct critical analysis by thoroughly evaluating cases and to provide high-quality education and training. 3D-printed bone and tooth models are invaluable to forensic odontologists, both in terms of analysis and facilitating communication in the courtroom. As increased resolution, better software becomes available, and cost-effectiveness increases, this technology will be adopted by more physicians across all disciplines. It is undeniable that 3D printing will play an increasingly important role in forensic odontology. The 3D printing technique has yielded accurate and reproducible results compared to computerized techniques using digital images and measurements. Further work is needed to standardize the use of digitized and printed 3D measurements. Reconstructing 3D evidence can be an important tool for investigators and experts, providing detailed data on the causes of events in a crime. The findings revealed that 3D-printed replica teeth were accurate to within 0.5 mm compared to real teeth. The results, based on digital comparison and ease of use, suggest that 3D printing has strong potential applications in forensic odontology[24,25]. Table 1 demonstrates features of basic diagnostic techniques which are utilized for forensic dentistry applications[26,27].

Table 1 Features of different imaging techniques utilized in forensic odontology.

Radiological technique	Forensic odontology and anthropology	Advantages	Disadvantages	Radiation dose
Periapical intraoral imaging	Individual identification by using shape, size and placement of restoration	Low radiation exposure	Only a small area is covered. Projection geometry errors	1-8 μSv
Panoramic imaging	Individual identification (using antemortem and postmortem panoramic). Age determination in young adults from dentition and its eruption sequence	Regular dental identification is possible	Distortion, magnification and overlapping of teeth. Only two-dimensional. No information in the 3rd dimension	4-30 μSv
Cone-beam CT	Generated panoramic image without distortion	Accurate, single tooth evaluation and panoramic image skull volumes	Metallic artifact	19-368 μSv
Multislice CT - medical CT	Skeletal findings examination	Digital autopsy	Three-dimensional virtual models	Lower jaw 1320 μSv upper jaw 1400 μSv bimaxillary 2100 μSv
Magnetic resonance imaging	Valuable supplement to postmortem CT for the detection of wound channel and soft tissue injuries	Evaluation of soft tissue injuries	Metal alloy artifacts	No ionizing radiation

CT: Computed tomography.

Virtopsy is a non-invasive autopsy method which uses advanced instruments. This method is combined with 3D body surface imaging techniques. The 3D shape analysis is performed by using CT/MRI data. Post-mortem CT data allows for the assessment of decompressed or injured bodies by examining the detailed hard tissue skeleton at different cross-sections. MRI allows for the visualization of soft tissue organs, while contrast-enhanced MRI allows the examination of living victims of abuse-related events such as strangulation. Magnetic resonance spectroscopy is useful in estimating time of death by determining the relative concentration of metabolites in tissues. Magnetic resonance microscopy allows for the visualization of subtler soft tissue injuries, and micro tomography is used to analyze the resulting injury patterns. There are several advantages of this technique such as; high accuracy, minimal risk of infection, and high accuracy. However, high cost, lack of artifact detection and absence of touch sensation are drawbacks of the method[27,28].

AI is increasingly being used in forensic dentistry. AI-based technologies used in forensic dentistry include deep neural networks, artificial neural networks, machine learning, and computer technologies. AI can be used in various ways to improve forensic dentistry, including tooth identification, matching individuals based on their teeth and jaws, estimation of the age and gender of individuals, creation of 3D models for use in facial reconstruction of unknown remains and bite mark analysis. In addition, AI can help identify individuals by searching and matching dental data in databases and AI-powered chatbots can be used to ask questions and provide information about forensic dentistry. Task automation can be provided for certain tasks, such as dental image analysis, reducing the need for manual work and increasing identification speed and accuracy. AI is still an emerging technology in forensic dentistry, and its uses and applications depend on the specific situation and application. Furthermore, appropriate regulations and controls are crucial to ensure that AI systems are safe, effective, and ethical[29,30].

CONCLUSION

The demand for forensic dentists is expected to increase significantly. Forensic odontology aids in the identification of individuals in cases involving extensively damaged remains and is indispensable in forensic investigations. Teeth, due to their durability and uniqueness, serve as critical forensic structures. Additionally, they are needed in age determination, bite mark analysis, and legal disputes related to dental malpractice. Widely accepted basic forensic dentistry techniques include comparative dental analysis, radiographic imaging, and DNA extraction from teeth that resist environmental degradation. Furthermore, forensic odontology collaborates with anthropology, botany, and entomology to enhance identification processes. Technological advancements such as digital forensic applications, 3D imaging and 3D printing, the integration of AI, and advanced DNA analysis have increased the accuracy of forensic dentistry identification. Bite mark analysis, while controversial, utilizes computer-aided comparisons. Forensic dentists are increasingly involved in legal cases requiring specialized knowledge, particularly dental malpractice disputes. Forensic odontology continues to evolve with the help of innovative technologies to increase accuracy and efficiency. Future research will focus on improving identification methods, utilizing AI-assisted forensic analysis, and addressing ethical concerns surrounding the use of DNA. Expanding and developing the expertise of forensic dentistry in both clinical and legal contexts is vital for the discipline to maintain its role in forensic science[31,32].