PM forensic dental examination

According to DVI guidelines the PM examination related to disasters is carried out by two forensic odontologists (FO’s), one being the examiner of the body, the other recording and verifying the findings [1]. At the PM dental examination (figure 1), a dental status is registered, including tooth status (primary, permanent, or missing), restorations (by surfaces and material), and other dental work such as crowns and implants. Additionally, all information of occlusion, tooth wear and abrasion, tooth position, morphological traits, anatomical anomalies and periodontal condition is gathered [8]. The use of diagnostic fibre light and UV light is recommended. Dental prothesis are described and photographed in situ as well as extra orally and subsequently replaced in situ. Any markings or labelling on dentures are checked and recorded [9][10].

Figur 1

PM-radiographs

The radiographic examination (figure 2) should always cover all alveolar bone regions, either with a panoramic radiograph supplemented with separate images of teeth with distinctive features such as root canal fillings or prosthetic restoration, or a full set of periapical images [1]. Impacted teeth, roots, abnormalities and pathologies in bone structure, precise details in the shape of dental restorations, parapulpal pins, screws, implants and other structural features are disclosed by thorough radiological documentation. PM radiographs enable a visual comparison of shapes and positions with AM data. Various conventional radiological methods can be applied. Full computed tomography (CT) scans are often useful for comparison; 3D overviews can be created, and data can be reformatted to simulate periapical and panoramic radiographs.

Figur 2

PM profile of an assumed individual or an unknown individual

For a PM profile all important dental information (figure 3) gathered in the PM examination is summarized in clear and straightforward writing that can be understood by police and other relevant stakeholders. The dental information is then integrated into the overall description of the unknown body to assist in the identification process. The detailed PM-data of an individual who remains unidentified is subsequently downloaded into internationally recognized software and transferred into a national «Missing persons/unidentified human remains» register. The police may pass the full PM profile, incl. dental, on to e.g. INTERPOL for scrutiny in relation to their international missing persons data base.

Figur 3

Collection and handling of AM dental data

The main source of dental AM data is from the dental clinics, but also hospitals, the military and other employers might have clinics or access to dental records. The collection of dental records is done in the Nordic countries by the police and often in close cooperation with FOs. Dental records contain confidential material and must be handled accordingly. Direct transfer of electronic records can be made through encrypted and secure internet systems but may create challenges since the health services and police are generally not on the same systems. Alternatively, electronic records can be copied to appropriate storage media and transported to the FO. It is important that such storage devices are handled with the same care as any other confidential material. Material from abroad may be obtained through INTERPOL or sometimes directly from the DVI-team in that country.

The complete dental records to be collected for identification consist of all available material: the written record, all radiographs, photos, casts, CBCT or CT scans and 3D photo scans. All radiographs should be collected even of poor quality – they might still contain useful information [23]. Electronic radiographs and photos are best collected in digital format. Casts, photos and intraoral 3D surface scans provide extremely important details of the dentition not documented in conventional records [8][9][14]. Occasionally, medical records from a hospital may contain information which are helpful in identifications e.g. following jaw fractures or radiographs of sinuses [24]. Smiling photographs may also assist in the identification [11][12].

Today, most dental records are electronic, but historic handwritten or typed AM record material is equally important for identification. The FO must interpret and import all AM dental information into a special identification record system (figure 4).

Figur 4

Comparison of AM and PM registrations

According to available guidelines quality assessment of both AM and PM data must be performed before the comparison process. To find the best possible matches between AM and PM data sets, it is helpful to prepare a list of special AM and PM markers. This way, only particularly noteworthy features of a missing person or body are recorded in a list. When several deceased individuals need identification a key marker list can be prepared for both the AM and PM subgroups.

The Nordic countries, as well as many other countries worldwide, use the INTERPOL adopted software DVI system (KMD PlassData DVI, Denmark) for recording, documentation and matching in DVI operations [1]it is also applicable for single cases. Special INTERPOL forms are used for digital registration of both AM and PM data which are imported into a structured database. The DVI software can suggest matches, and the FOs must evaluate these matches carefully to depict the most pertinent [25]. These must then be checked by individual comparison of the details in the AM missing persons file with the corresponding findings in the PM file (figure 5). Obviously special findings like prosthesis, implants, root canal fillings, special fillings or rare/striking morphological or anatomical features constitute important proof to the dental identification. However, also a sound inconspicuous dentition without any dental treatment may be identified with certainty when detailed AM dental data are available, e.g. high-quality regular BWs, and intraoral 3D surface scanning prior to orthodontic treatment. When comparing AM and PM data inconsistencies may occur. These may be explainable, i.e. as charting errors or misinterpretations (e.g. were 1^st or 2^nd premolars extracted o.c.). Incompatible inconsistencies are discrepancies where no explanation is possible, e.g. a restored tooth cannot turn into a sound tooth. The FO must consider all inconsistencies very carefully.

Figur 5

According to international guidelines the FO comparison analysis can result in identification established, rejection (non-identification), or the establishment of a possible or probable identity [1][26]. Insufficient evidence may also be a conclusion [26].

Since no useful data exist on the prevalence of all features that may be recorded in the human dentition no valid objective statistics can be applied to support the FO judgement of the identification level. For the same reason no evidence-based decision criteria based on the number of points of concordance can be established although efforts were made [27][28]). The clinical experience of the involved FOs in combination with thorough scrutiny of all the data by at least two independent FO colleagues result in a comparison report and finally an identification certificate in case identity can be established [2][25].

In DVI operations after mass disasters, an interdisciplinary reconciliation board will review and reconsider all proposed identification reports before a final identification report and certificate can be issued [1][25].

Conclusion

Forensic dental identification is a reliable method for establishing identity and has the advantage of being very fast. However, it relies on the availability of detailed AM dental data, trained forensic odontologists, and required equipment and facilities. In the Nordic countries, a substantial part of the population visits a dentist regularly, therefore AM dental records are commonly available when needed. Due to the rapid expansion of new diagnostic tools in dental clinics (e.g. CBCT-scanners and intraoral surface scanners), the amount of detailed AM dental data is growing and thus available for identification purposes. Forensic dental identification is likely to remain a highly relevant method despite trends towards improved dental health and fewer dental restoration characteristics in younger individuals.