Forensic radiology in dentistry.

Radiography can play an important part in forensic odontology, mainly to establish identification. This may take the precise form of comparison between antemortem and postmortem radiographs. Radiographs may also be taken to determine the age of a minor victim and even help in the assessment of the sex and ethnic group. Comparable radiographs are an essential factor to confirm identification in a mass disaster.

Forensic radiology has a long tradition in the forensic sciences. Its history started in 1895 when the first radiograph was made by Conrad Roentgen. Three years later, in 1898, postmortem radiographic examination was introduced. Forensic radiology, so far as depended almost exclusively on the X-ray and the static image captured on the roetgenogram.

Uses and utilization of radiology in forensic dentistry

Radiographs have helped to solve difficult cases in the forensic science.[123]

Identification of victims

Radiographs are helpful to determine the age of an individual by assessing the stage of eruption of teeth. Skull radiographs can be used in the identification by superimposing on antemortem radiograph or photograph. Since frontal sinuses are known for greatest normal variations among individuals, they are used for this purpose. Yoshino et al. have classified frontal sinuses based on size, bilateral asymmetry, superiority of side, outline of upper borders, presence of partial septa and supraorbital cells and reported a criminal case in which frontal sinus was used to identify a person.

Sassouni has suggested use of measurements in postero-anterior and lateral radiographs of the skull to match the ante and postmortem radiographs, which includes

Bigonial width

Cranial height (from mastoid to vertex)

Bimaxillary breadth

Height from bigonial width to temporal crest

Maximum cranial breadth

Frontal sinus breadth

Incisor height

Facial height.

Evidence in the identification of the suspect

Cases have been reported where suspects were identified because of fractured tooth parts of victims in the body of the suspects or fractured tooth of suspect in the victim as in the bite mark cases. Deliberate alteration in the shape of the teeth in suspects can be identified with radiographs in bite mark cases.

To determine the cause of death

Radiographs may provide evidence of bullets or foreign bodies in the soft tissues following firearm incidence and explosion. After air crash accidents, the cause of the crash may be elucidated by the presence of radio opaque objects in the soft tissues. This is due to contamination with molten aircraft metal producing irregular shaped radio opacity.

To find faulty charting of teeth

Sometimes, while charting postmortem data teeth may be wrongly numbered especially in cases where adjacent tooth migrate into the extraction space. This can be connected using radiographs.

Legal matters

Following injury or assault radiological imaging is commonly obtained by medical expert interpretation of these images may provide useful evidence in criminal and civil jurisdiction.

Body identification

Along with dental and DNA analysis, radiographic images are used in the unknown victims. This requires the securing of premortem examination e.g., Computed tomography (CT) scan or radiograph of the suspect individual and the matching of specific anatomical details with similar postmortem studies.

Postmortem examination

Nortje (1986) stated “radiographic appearance of teeth and bone of the face is a permanent record of these tissues even when teeth and sections of bone are removed for histopathologic examination.”

Nonaccidental injuries of children

Radiology places an important role in diagnosing child abuse. Accidental cranial fractures in infants are usually simple, linear and unilateral, affect the parietal bone and do not branch or cross sutures. Forensic radiologists suggest different techniques for specific head injury. CT is recommended for detection of subarachnoid hemorrhages while magnetic resonance imaging (MRI) is superior in revealing subdural hematomas, concussive injuries, and shear injuries. CT and MRI are equally efficient for demonstrative epidural hematoma, and CT advocated detection of fractures.

Forensic anthropology

Establishing biological age and identification of human remains are issues addressed by forensic anthropologists. The most common radiograph used for establishing age up to 16 years old are dental radiographs and hand radiographs. Postcranial radiographs of specific ossification centers depending on the reputed age of the individual are useful estimating older individual. Panoramic radiographs which visualize most structures of the jaws and related areas on a single radiograph, have been advocated for mass screening.

Record keeping

Careful record keeping, in medical facilities and private practices for as long as feasible, is extremely important. In most countries, radiographs pertaining to inactive patient's files are stored for at least 5 years. Radiographs are generally regarded as the property of the hospital or office in which they were produced although the law guarantees patient access to them.

Expert testimony

It is important to remember to present the biological data both in scientific and layman terms. Before submitting the data circumstances, the radiographs were produced. The expert should know if the radiograph is original or a copy and the whereabouts of the radiographs at all times.

Basic principle used for postmortem radiograph

When a radiograph of postmortem remains is performed to compare with ante mortem radiograph “Identical projection” must be achieved with similar magnification, exposure factors, and angulations so as to reproduce the ante mortem radiograph like image. This is carried out using various angles of projection and by varying technical factors.[1234]

General considerations

Radiograph should be taken before and after head and neck autopsy. Whenever possible, radiograph should be made at the scene of accident or crime. They should be properly labeled with identification number, site, and date of examination for future reference.

All intra and extra oral projections including panoramic radiographs have to be taken as and when it is needed depending on the case and type of remains.

Intra oral radiographs

Intraoral radiographs are difficult to perform particularly when there is restricted mouth opening. It may be necessary to remove soft tissues from the floor of the mouth or cheeks to insert the film. A miniature intraoral X-ray source may be used.

Resected maxilla may be split through the midpalatal suture. The posterior mandible and maxilla are placed on occlusal film to produce an “enlarged bite-wing film.”

Whenever fragmented remains consisting teeth, restorations, bone pieces, appliances are recovered they have to be separated by the method proposed by Johanson.

Johanson's method

Place the debris on the plastic grid.

Place the film on a wire grid identical to the plastic grid.

From the resultant radiograph type of remaining can be identified.

Radiographic Techniques Used in Forensic Dentistry

Extra oral radiography

With the oblique – lateral technique, it is necessary to increase the anode – object distance in order to enlarge the field of irradiation. The minimum distance is 40 cm which will project onto the film a 10 cm diameter beam of X-rays. The exposure factors using high definition intensifying screens will be 55–60 kVp and 20 mAs [Table 1]. When using faster screens, the milliampere seconds is reduced.[4]

Table 1

Intensity of extra oral radiographs

Panoramic radiographs

The X-ray tube and film rotate around a stationary patient; specimens must be elevated in position, articulated, and oriented with the occlusal line or Frankfort plane parallel to the ground. A setting of 8 mA at 80 kVp is a good starting exposure; a previously exposed black film can be placed in the cassette against the unexposed film to reduce the effect of intensifying screen.

Investigatory Methods in Forensic Dentistry by Means of Various Radiographic Interventions

Bite marks

Radiographs may be used to assist in the identification by bite marks. The impressions are made with dental modeling wax and cut to size of an occlusal film. The resultant impression is then filled with radiopaque dental alloy and placed with occlusal surface downwards on film. The X-ray beam is directed centrally at right angles to the object and film. An anode – film distance of at least 40 cm is recommended to give more parallel beam.

Comparisons of antemortem and postmortem radiographs

Antemortem and postmortem radiographs are compared noting similarities and differences. The most current films are examined first because they will show the greatest similarity to the postmortem status of the teeth and jaws. Comparison is done on

Number and arrangement of teeth (missing teeth, rotated teeth, spacing, extra teeth, impacted teeth)

Caries and periodontal bone loss

Coronal restorations

Hidden restorations (posts, implants, root canal fillings)

Bony pathology

Dental anatomy

Trabecular bone pattern

Anatomic bony landmarks

Maxillary sinus and nasal aperture

Frontal sinus.

Age estimation of adults from dental radiograph

With the advancing age, the size of the dental pulp cavity is reduced as a result of secondary dentine deposit so that the measurements of this reduction can be used as an indicator of age.[56789]

Secondary dentine as also been measured indirectly on radiograph of extracted teeth. Such measurements were suggested use in nondestructive method to predict the age. The ratio between pulp and the root has also been used in age estimation as the size of the pulp is reduced with age. Radiographs of the middle phalanx of the third finger are taken to know the skeletal maturation status of the child.

Diversity of dental patterns in the orthopantomography for human identification

The comparison and antemortem and postmortem dental characteristics are a commonly applied method to perform personal identification. Orthopantomography is broadly applied standard method in dentistry. It provides the complete view of the teeth and both jaws and one image. Gustafson was the first to use orthopantomography in forensic practice for the purpose of identification, according to the theory proposed by Paatero, Rocca et al. considered orthopantomograms to be the most important antemortem source of information outside the written treatment records. The use of orthopantomography is practically applicable for the identification of victims of mass disasters as well as wars.[4]

Personal identification on the basis of antemortem and postmortem radiographs

There are many parts of the human skeleton, which because of their anatomical variability are very applicable to the identification process. The first authority to point this out was Schuller, who found that X-rays of the frontal sinuses are very good tool for identification.[1011]

Currently, there are three main comparison methods of personal identification used in Hungarian forensic practice:

Examination of dental records

Superimposition of photographs

Comparison of radiographs.

New horizons in forensic radiology – multislice computed tomography

Alternatives to classic autopsy to collect forensically relevant data the potential of multislice computed tomography can be used. With this modern method, the scan time for a full body examination with a gunshot wound to the head is approximately 60 s. This method is rapider, based on nondestructive documentation process and in some respects is more precise than the standard forensic autopsy.[121314]

Dental Computed Tomography Screening Tool for Dental Profiling

The newer CT imaging based software called Dentascan (GE Health care, UK) used for identification purpose. Using the Dentascan software, reformatted panoramic images could be reconstructed for each case that was compared to the antemortem dental periapical radiographs, bite-wing films, and panoramic radiograph.[15]

A reformated panoramic overview created by Dentascan delivers in a noninvasive way to overview jaws showing basic components of teeth, (enamel, dentin, pulp) anatomic structures of alveolar bone (mandibular nerve canal or floor of nasal cavity and maxillary sinus), pathology (caries, radiolucencies, radio-opacities, or position of third molars), and restorations.

The most important advantage of Dentascan in contrast to classical methods is that documentation can be made noninvasive and digital way without jaw resection, which is often performed to facilitate classical radiological documentation on decomposed, charred, and mutilated corpses.

Identification of skull by its suture patterns

The examination of 320 skulls collected at random revealed ectocranial suture patterns in them are highly individualistic and that no two skulls can ever have an identical pattern. The possibility of the suture patterns being recorded incidentally in routine diagnostic skull radiograph was verified by examining the skull skiagrams preserved in the radiology department and can be more effectively used in personal identification problems. A positive method of identification of the skull is suggested by the comparison of radiographic with visible skull suture pattern. The added advantage in the process of identification through suture pattern is that they cannot be altered or destroyed in case of finger ridges.[16]

Individual identification by means of conventional bite-wing film and subtraction radiography

The digital subtraction technique used in clinical trials for the evaluation of small tissue changes. It may, however, also be able to determine hard tissue similarities for use in forensic dentistry. Principle of digital subtraction included features for correction of variations in exposure geometry and density. Subtractions were performed between identical images (images of the same individual) and between nonidentical images (images of two different individuals).[1718]

Bite-wing radiography is considered as a good candidate for potential victim identification [Figure 1]. A quantitative analysis of subtraction images based on bite-wing radiographs as recently been reported. The subtraction images derived from identical photographs significantly more homogenous than those derived from nonidentical radiographs originating in individuals with and without simple dental restorations.

Figure 1

(a) Antemortem bite-wing radiographs (b) Postmortem lower bite-wing radiographs

Sex determination by lateral radiographic cephalometry

In general, male skulls are identifiable by being more robust. Female skull is characterized by weaker development of its super-structures. All bony ridges, crests, and processes are smaller and smoother in the female skull than in the male skull, especially true for the temporal line, mastoid processes, nuchal lines, external occipital protuberance, and superciliary arches. Sella to nasion, Frankfort horizontal place and basion to nasion as reference lines or planes are commonly used in lateral radiographic cephalometric analysis. Thus, morphometric traits of the skull super-structures and intracranial structures are easily assessed. This enables us to use them as morphometric variables.[19]

X-ray screening system at a mass disaster

A security scanning system known as line scan unit was used which allows screening where space may be limited. They operate on 105–125 VAC, and the X-ray voltage is 160 kVp.[20]

Summary and Conclusion

The radiological identification of individual human remains depends entirely on matching specific and unique visual findings or features on both ante mortem and postmortem radiological images of that person. Postmortem findings confirming the sex, age, stature, or race may be either confirmatory or exclusionary.

Dental identification is also scientific, relying on the patterns of missing, filled, and decayed teeth as well as anatomic variation of the teeth, jawbones, and sinuses. Teeth and bones are also durable, surviving decompositional and destructive forces.

The decedent's teeth are compared to ante mortem written records although the most accurate and reliable method is by comparison of ante mortem and postmortem records. Unlike subjective records, which lack detail and can include errors, radiographs supply objective data through precise recording of unique morphology of dental restorations and dento – osseous anatomy.