1. On-site evidence recovery

2. Postmortem dental examination and radiography

3. Obtaining dental records

4. Comparing post– and antemortem data

5. Preparing the identification report and conclusion

On-site evidence recovery

To begin with, it is essential to collect all dental evidence from the dead body (Haglund and Morton, 1994). This may require the dentist’s presence at the site where the dead body is recovered (Brown, 1984). Dental evidence present at the site where the body was found may be overlooked and not recovered—decomposition and skeletonization often leads to loosening of teeth and the anterior teeth, which have conical roots, may get dislodged. Oliveira and associates (2000) and Duric and coworkers (2004) have reported that incisors, especially maxillary, are most prone to getting lost postmortem. Incinerated bodies have fragile bones and teeth, which can easily be mishandled by an untrained individual; trauma may result in scattering of dental evidence around a large area. Acharya and Taylor (2003) have found that the inability to recover complete and intact postmortem dental data can undermine successful identification. Therefore, to maximize success, one must try to recover all dental evidence that may be present at the site. Hence, care must be taken to document and photograph the scene at which the body is recovered; a forensic odontologist should be present to ensure proper search and recovery of all material of dental significance needed for identification.

Postmortem dental examination and radiography

The postmortem dental examination is usually conducted in a mortuary. Case numbers allotted to the body should be verified and entered in the modified Interpol postmortem dental odontograph, also referred to as the ‘pink form’ (Figure 1) before the commencement of examination. A visual appraisal of the body may enable preliminary assessment of the ethnicity, gender and approximate age of the victim. The body bag used to transport the deceased should be thoroughly searched for dislodged teeth or dental appliances. Postmortem dental examination is similar to routine examination of the oral cavity. All oral and dental features, including intact and missing teeth, caries and other pathology, restorations, attrited and rotated teeth should be carefully charted on the postmortem form. This will be the basis for later comparison and verification. Brown (1984) suggests that postmortem examination should be undertaken by dentists working in pairs—one examining and the other recording. The roles are then reversed and the procedure repeated ‘as an added check’. Any dental evidence missing should be reported to the forensic pathologist or accompanying law enforcement personnel. Subsequent dental evidence recovered must be labeled properly.

The dental examination must be complemented with postmortem dental radiography as this will reveal what cannot be observed clinically. Radiographic films may be stabilized in the mouth using readily available materials such as gauze or cotton rolls. Whenever possible, postmortem radiographs should be taken to replicate the type and angle of the antemortem radiographs (Goldstein et al, 1998). According to these authors, if the difference in horizontal angulation between the ante- and postmortem radiographs is more than 10°, comparison will not facilitate identification. However, changes in the vertical angulation or the focal point-film distance do not affect the outcome of comparison. Pretty and Sweet (2001) have suggested that ante- and postmortem radiographs could be marked using a rubber-dam punch to differentiate the two—‘one hole for antemortem films and two holes for postmortem films’. The exposure time may need to be increased or decreased respectively in bloated bodies recovered following drowning and in skeletal remains.

Obtaining dental records

Dental records contain information on treatment and dental status of a person during life. These antemortem records can be obtained from the local dentist, specialist or hospital records. Whenever possible, the original records should be examined. Records include hand-written dental charts, radiographs, study casts and photographs. An individual may have visited more than one dentist for therapy and multiple dental records may exist. Relevant information from the dental records should be transcribed onto the modified Interpol antemortem odontograph (the ‘yellow form’) (Figure 2).

Contribution of dental records in successful identification depends on the availability of original records, their completeness and quality (Acharya and Taylor, 2003). By maintaining good dental records, dentists reflect their awareness and responsibility to forensic identification (note: quality dental records are also important as a counter to malpractice lawsuits). It is also important that these records are relatively recent—records made for a 6-year-old child may not be useful 20 years later in adulthood.

Comparing the dental data

The comparison of known antemortem data with the obtained postmortem data is called comparative identification. Sholl and Moody (2001) have stated that ‘the basic principle of any method of identification is to determine that individual characteristics observed postmortem are congruent with those known to have been present in life’. Once the postmortem findings and antemortem records are available, the data can be compared. Comparison should be qualitative rather than quantitative in nature; it must also be systematic and methodical. Features compared include dental restorations, pathology, crown, root and pulp anatomy, associated bony structures, artifacts and dental anomalies. An individual with multiple dental treatment and uncommon dental features has a better probability of being identified than someone with no extraordinary dental characteristics.

Identification report and conclusion

Subject to the availability of adequate postmortem data and quality antemortem records, Haglund and Morton (1994) have stated that ‘the comparison and eventual dental identification are straightforward and routine’. These authors believe that the quality and quantity of information required for establishing positive dental identification has not been established. In fingerprinting, differences in the ante- and postmortem data rule out a positive match. This concept, however, does not apply to dental identification as long as the inconsistencies are explainable. For example, the postmortem data may reveal a restoration on a tooth but the dental records indicate that the same tooth is intact. This difference, however, can be explained since the restoration may have been placed on a date after the last available dental record. On the other hand, if the postmortem data shows an intact tooth but the same tooth is indicated as being restored in the dental record, this would probably suggest a mismatch. Having compared the ante- and postmortem data, one should address whether the similarities are significant and the differences can be explained. Based on this, a range of conclusions can be reached which have been modified below from McKenna (1986), Silverstein (1995) and Acharya and Taylor (2003).

Crown

Muller and associates (1998) have undertaken one of the few detailed works on changes that teeth undergo when exposed to high temperatures. They observed that enamel shows crazing (fine surface cracks) at 150°C but retained its normal color although at 200°C, enamel loses its gloss. Further increase in temperature causes more crazing— initially over the neck, then more coronally—followed by a few frank cracks.

Initial separation of enamel from dentin occurs at 400°C and the enamel shell separates totally at 450°C. At 500°C, Harsányi (1975) has observed deep longitudinal furrows on the crown which almost divide it into several pieces. At this temperature, the pulp chamber and root canal are preserved and not narrowed. Above 500°C, the crown undergoes fragmentation and consistently becomes smaller with further rise in temperature. The narrowed cavities of the pulp chamber and root canal are recognizable even at 1,100°C.

The coronal dentin is exposed at 450°C (following total separation of the enamel shell). Cracks appear at 600°C with disintegration from 800°C onward. While enamel is converted to powder, dentin is not. This has been attributed to hypermineralized pretubular zone of the dentin. Myers and colleagues (1999) believe that the mineral content of dentin, located within its organic matrix composed of type I collagen, helps stabilize the collagen against thermal denaturation and shrinkage. The color changes in the crown and root at different temperatures has been demonstrated by Muller and associates (1998) (Table 1). However, these authors have cautioned that in real-life scenarios, it may be much more difficult to observe the color changes since teeth found at the site of fire need to be carefully cleaned. They added that ‘the presence of a superficial metallic layer, resulting from the dry distillation of organic matter, can lead to observational errors’.