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The methods used for disaster victim identification is comparative postmortem profiling of dental and fingerprint data. Twelve dental concordant features are normally required for dental identification. The radiographic image of dental amalgam restorations has been shown to be highly significant for identification purposes. The aim of this study was to investigate the radiological morphology of standardized radio-opaque composite fillings in premolar teeth with regard to their discriminatory potential for identification purposes. Thirty lower first premolar teeth ("Typodont" acrylic teeth) that were filled with 3- surface fillings (MOD) radio-opaque composite resin (Z100) by 4th year dental students were used for this study. Bitewing radiographs were taken of all thirty fillings and labeled Set 1. A second set (Set 2) consisted of 10 randomly selected duplicate radiographs of Set 1, plus 2 other radiographic images not from Set 1. Instructions were given to 20 dentally trained examiners to match the 12 radiographic images of Set 2 with the 30 images of Set 1. The results showed that 18 of the 20 examiners correctly matched the 12 radiographic images, one scored 11 out of 12 and one scored 10 out of 12. This study shows that if the ante-mortem and post-mortem radiographs of a single composite filling have exactly the same morphology, this image is unique and 12 concordant features are not necessary for dental identification.

The standard dental bitewing radiograph is used to detect interproximal caries but it also provides a specific view of the dental restorations that can be duplicated for identification purposes. The antemortem and postmortem bitewing radiographs are often not at the same angle and result in distorted images of the restorations. The aim of this study was to investigate the progressive increase in angulations of a bitewing radiograph of the same restoration and to determine at what angle the image is distorted sufficiently as not to be recognized. Bitewing radiographs were taken of the same two restorations at 5 ̊, 10 ̊, 15 ̊ and 20 ̊ superior, inferior, mesial and distal to the original 0 ̊bitewing radiograph. Twenty examiners were required to determine at what angle the distortion prevented matching of the image with the original bitewing radiograph. The results showed that the image distortion at 15 ̊became suspect but at 20 ̊none of the images could be matched to the original bitewing radiograph.

The dental identification of human remains utilizes the matching of dental restorations. The radiographic images of amalgam restorations are paramount in this process. The compound amalgam restoration has a unique radiographic morphology and can be readily identified in both antemortem and postmortem data. To test the radiographic morphology of compound amalgam restorations, 10 out of 40 Typodont teeth, restored by students, were tested for their discriminatory potential by 12 examiners. The results showed that the radiographic morphology of compound amalgam restorations can be accurately matched by dentally trained personnel. This suggests that in cases where accurate radiographic material is used for dental comparison, less than 12 concordant features are necessary for positive dental identification. If the antemortem and postmortem radiographic images of a compound amalgam restoration are exactly the same then this feature is unique and identification can be achieved by a single concordant feature.

Part 1 of this two-part article dealt with mass disasters in general, their characteristics and the agencies involved in their management. This part looks at the specific role of the forensic dentist, as well as the general dentist, in a mass disaster as member of an 'away' or 'home' team.

In this article, the first of two on the involvement of dentists in a mass disaster, the focus is primarily on mass disasters in general, some common characteristics and types of disasters, those agencies or individuals involved in the management of a disaster, the different phases of a disaster and the position of the forensic dental identification team (FDIT). Part 2 will deal with the functions, responsibilities and jurisdiction of the FDIT during the various phases of a disaster and more specifically immediately after the disaster.

The composite resin, compomer and glass ionomer restorative materials used in modern dental practice are fire resistant and remain radiopaque. They shrink significantly and are likely to fall out of the cavities after being burnt, but they remain extremely important for identification purposes and it may be possible to identify the white filling materials used to restore teeth by their radiopacity and morphology. The radiographic density of these filling materials do not change significantly when exposed to heat and although they may be difficult to see with the naked eye, they will remain visible when radiographed. Furthermore, special care has to be taken when handling heated materials as their compressive strengths decrease significantly depending on temperature and time of exposure and damage is possible.

The combination of restorative procedures, developmental or acquired defects, or abnormalities of teeth enables the forensic dentist to make a meaningful comparison of ante- and postmortem data in search of the identity of a person. Dental records are not always sufficiently accurate to supply 12 concordant points from which a positive identification can be made. Under certain circumstances a single feature may be so extraordinary or unique that it alone can be sufficient to make a positive identification. Two cases of identification in which only one unique feature was used are reported.

This is a case report in which the bite patterns of two suspects were compared to a bitemark on the breast of a murder victim. Each suspect had sufficient concordant features to have been found guilty of producing the bitemark. The irony in this case is that the bitemark was not inflicted by the murderer.

The skeletonized remains of an American hitch-hiker were recovered from a forest near Knysna in the Cape. There were no recognizable features except the presence of dental restorations. The use of the "fax" to transmit dental records while being a speedy means of communication does have its limitations. Electrical faults on the telephone line can cause the document to become illegible and subsequent duplication of this document aggravates the problem. An appeal is made to standardize the notation of teeth by using the FDI code and to adopt a 2 digit code for restoration morphology.

Forensic dentistry has become an integral part of forensic medicine over the past 100 years. This has been due to the dedication of people like Amoedo, Gustafson, Sognaes, Keiser-Nielsen and Suzuki, to name but a few. They established the essential role which forensic dentistry plays mainly in the identification of human remains. Dental hard tissues are extremely resistant to fire and are usually the only remains after an extended period of burial. If antemortem dental records are available for an individual then dental identification is as certain as those of fingerprints. In South Africa forensic dentistry had its beginning in 1969 during the Windhoek air disaster. Since then there have been several cases of interest throughout the country, one of which was the crash of the Helderberg off the coast of Mauritius. Other aspects of forensic dentistry are the examination of bite marks and the recognition of facial trauma especially in cases of child abuse; the determination of age, sex and race of skeletal remains; dental ethics and jurisprudence as well as malpractice also form part of the duties of the forensic dentist. The five dental schools in South Africa each have a forensic team which is consulted on a regular basis by forensic pathologists and district surgeons. Forensic dentists are active members of the medicolegal team and should be consulted on a regular basis especially in cases where identification is concerned.

The exhumation of two victims of a light aircraft accident was performed in February 1991 at Oudtshoorn, Cape. The exhumation was ordered by the magistrate on request of the parents of one of the victims who suspected that their son had been wrongly identified at the postmortem examination. At the pre-burial autopsy all the victims were positively identified, but the identity of two of the victims was subsequently reconsidered and reversed because one of them wore a silver bracelet. Burial then took place. The exhumation was ordered one month after the accident at which stage the bodies were in an advanced state of decomposition. Oral autopsies were performed on each of the victims, the jaws were radiographed and postmortem dental records drawn up. Dental records were obtained from the dentists who treated them and the information from these records was used to draw up ante-mortem dental records. A comparison between the postmortem and ante-mortem records showed that the victims were incorrectly identified and reburial in the correct graves was subsquently carried out. This case again emphasies the importance of dental identification in cases of severe burning, multilation or decomposition in order to avoid mistaken identity and incorrect burial in the future.

Twelve concordant characteristics are used in fingerprint identification. The South African courts of law are prepared to accept 7 concordant characteristics as being "beyond reasonable doubt" in the case of finger, hand and foot prints. In cases of identification by dental means, 12 concordant features have been advocated. In South Africa, with its mixed population in which a large majority have dental formulae containing normal decayed and missing teeth, these patterns show duplication and triplication. It is feasible to submit 7 concordant dental characteristics as positive identification in a mouth containing dental restorations, but in a mouth which features only missing teeth, pattern duplication demands more than 12 concordant characteristics for positive identification. Seven concordant dental characteristics have not been tested in the South African courts to date.