Human identification using dental techniques: A case report

Introduction

Dental techniques are often used in human identification.^1–4 The resilience of teeth and their supporting tissues to various insults is one of the features that accounts for this fact. In fact, dentition can withstand chemical insults, burning, burial, submersions and even severe head and neck trauma to such an extent that identification is possible.^1,5 In addition, teeth possess several features that allow discrimination between individuals. ⁶ These features relate to morphologic, pathological and therapeutic characteristics. If these particular features are registered in a dental record, a dental cast or an X-ray they can later be used in dental comparison. Once the postmortem examination is complete and all dental data are registered, a systematic and methodical comparison is made between ante-mortem and postmortem records. Following data comparison, a range of conclusions can be drawn ⁵ : (a) positive identification (ante-mortem and postmortem findings match in sufficient details, without any unexplainable discrepancy); (b) possible identification (ante-mortem findings may be consistent with postmortem findings, but a positive identification with certainty may not be established because of the poor quality of either the postmortem remains or ante-mortem dental records); (c) insufficient evidence (information in the ante-mortem and postmortem dental records are insufficient to draw a conclusion of any sort); (d) exclusion (ante-mortem and postmortem dental data are clearly inconsistent with respect to many features).

In this paper, we present a case in which a positive identification was made using dental techniques. We used the Interpol DVI forms for registering the collected data, ⁷ and the FDI (Fédération Dentaire Internationale) notation was used to classify teeth.

Case report

A nine-year-old female child was reported missing after she and her grandmother were caught by the sea. Her grandmother’s corpse was recovered the same day, and identification was confirmed by visual recognition.

Two weeks later, a corpse of a female child was recovered on a nearby beach, in a state of advanced decomposition; visual recognition was impossible but, due to the circumstances, it was thought that the child could be the missing girl.

Postmortem examination

Both the upper and lower jaws were complete and with teeth. Teeth 53, 12, 11, 21, 63, 73, 32, 31, 41, 42 and 83 were missing, and no bone remodelling was observed in any tooth socket, suggesting postmortem teeth loss. The body was in an advanced state of decomposition, and we found no evidence of ante-mortem injuries to the oral soft tissues, jaws or teeth.

The following dental findings were registered:

Missing postmortem: 53, 12, 11, 21, 63, 73, 32, 31, 41, 42 and 83.

A further finding included a paramolar tubercle, which was found on the buccal surface of both upper first deciduous molars (Figure 1). Note that the circled tubercle is not the normal pronounced mesio-buccal bulge, often referred to as the Tubercle of Zukerkandl, but an extra tubercle. OPEN IN VIEWER

No radiographs were taken. Supplementary information included photographs and image enhancement for better detail of the morphologic features. Age was estimated between 8 and 10 years old, by clinical estimation, using dental eruption.

Ante-mortem data

Dental records were obtained from a single dentist from a private practice who treated the alleged victim. The data consisted of dental records and a plaster cast from the upper jaw, made a year before (Figure 2). The dental records contained the following information:

Filled teeth: 16(O), 26(O), 36(O) and 46(O) – all of them with fissure sealants – and 11(MI) e 21(MI), both with mesioincisal composite resin.

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Figure 2.

Paramolar tubercle in the plaster cast.

Additionally, on the plaster cast, we were able to identify paramolar tubercles on the upper first deciduous molars.

Results

We were able to verify the following data:

Filled teeth: 16(O), 26(O), 36(O) and 46(O) – all of them with fissure sealants.

The upper central incisors were lost postmortem, and thus the composite resins could not be verified. The total number of verified features was 15.

Discussion

The analysis of comparative data is by far the most difficult part of a dental identification examination. In 1977, Keiser-Nielsen ⁸ stated that a minimum of 12 concordant points should be used in positive odontological identification. The basis for selecting this number of points was, however, not clearly explained. Since then, several authors have stated that single features can have a sufficient degree of individual specificity to allow positive identification.^9–12 According to Acharya and Taylor, ⁹ there appears to be no basis for defining a minimum number of concordant points necessary before a positive identification can be made on dental evidence. Rather, each case is unique and should be treated as such. This author stated that ‘the premise of Keiser-Nielsen’s argument that an ignorance of the frequency of occurrence of dental characteristics would undermine the value of a single unique feature cannot be justified, because the uniqueness of the human dentition is beyond doubt’. Even though, nowadays, this latest sentence can be an overstatement, ⁶ the truth is that the quality of the concordant points is undoubtedly more important than their number. Pretty and Sweet ¹ have stated that, in some cases, a single tooth can be used for identification if it contains sufficient features. Acharya and Taylor ⁹ reported that in 245 cases, 48 had an identity confirmed using between 1 and 11 concordant points, meaning that 19.6% of all confirmed cases were based on fewer than the 12 concordant points suggested by Keiser-Nielsen as a minimum for positive identification. ⁸

In this case, 15 concordant points were established: the four fissure sealants; the two paramolar tubercles in the first deciduous upper molars; and the presence of teeth 55, 54, 22, 64, 65, 75, 74, 84 and 85.

The presence of fissure sealants is not very discriminative, since, in the Portuguese National Dental Plan, the placement of sealant in permanent teeth has been prescribed for all children, free of charge, since 2002. ¹³

The presence of teeth 55, 54, 22, 64, 65, 75, 74, 84 and 85 is also not a very strong concordant point. According to the International Organization for Forensic Odontostomatology (IOFOS), the quality assurance guidelines in identification in single cases state that for establishing an identity, the expert should feel absolutely confident that the identity is correct. ¹¹ These features, though concordant, do not fit this degree of certainty.

On the other hand, the paramolar tubercle is a very distinctive feature. It was first described in 1916 by Professor Bolk.¹⁴ Later, Dahlberg referred to this structure as ‘parastyle’ when present in the upper molars and as ‘protostylid’ when present in the lower molars.¹⁵ This trait is a cingulum derivative expressed on the facial surface of the upper molars, most frequently found on the third molars, occasionally on the second molars and very rarely on the first molars. ¹⁶ This definition is not unanimous. Turner and Harris, ¹⁷ quoting the work of Dahlberg, stated that the paramolar tubercle is applied to a style or cusp of supernumerary character that is developed on the buccal or lingual surfaces of the upper and low premolars and molars. Rodríguez and Moreno ¹⁸ wrote that paramolar tubercles occur as accessory cusps located on the buccal or lingual surface of the primary and succedaneous teeth, involving both the maxillary or mandibular tooth types. Regarding their frequency, the paramolar tubercle is described by Rodríguez et al. ¹⁸ as a low-frequency trait and thus very important for human identification purposes. Ishida et al. ¹⁹ reported that paramolar tubercles have a 1.3% frequency rate in Japanese children. In another Japanese study, paramolar tubercles were referred as being more frequent in the primary dentition. ²⁰ Yet, these frequency values concern one single occurrence. In our case, bilateral occurrence was reported. Unfortunately, we were not able to find any frequency data regarding paramolar tubercles in the Portuguese population. According to Adams, ¹² the goal in dental comparisons is to remove subjective judgement calls, and this can be done using frequency information regarding the occurrence of specific dental patterns in the general population. In this manner, studies concerning the frequency of these traits in the general population should be conducted.

Conclusions

Positive identification based on 15 concordant points was achieved. However, even though ante-mortem and postmortem findings matched in sufficient detail and there were no unexplainable discrepancies, it was not the amount of concordant points that supported our conclusions, as many of those features had low discriminative capacity. Instead, it was the quality of fewer features, particularly the bilateral paramolar tubercle, described as a low-frequency trait.