The advances in digital technology have evolved dental models into highly reliable tools for human identification. Addressing the limitations of traditional stone models and DNA analysis, it is now possible to utilise 3D digital palatal model to distinguish monozygotic (MZ) twins.
By Dr Botond Simon, Dr Ajang Armin Farid, Dr George Freedman, and Dr Janos Vag
The exponential growth of digital technology in dentistry is inherently accompanied by a significant expansion of 2D and 3D dental image records. Traditional stone models are impractical to keep long-term due to storage volume and fragility.
Comprehensive and accurate models offer an excellent record of the preoperative dentition for the complete restoration of a smile that matches the original (Renne, Evans et al. 2017, Revilla-Leon, Raney et al. 2020). The longer-term storage of dental models facilitates resolving legal cases, and might aid bite mark analysis in some criminal cases (Khatri, Daniel et al. 2013). Yet another application of dental models is for human identification.
In addition to DNA and fingerprints, dental examination is a primary tool for disaster victim identification (DVI) (Interpol, Tsokos, Lessig et al. 2006). Dental models that are discarded or lost may deprive biologically driven oral rehabilitation of historical tooth, bite, and bone reference points, and may hamper positive identification.
Population-wide databases for fingerprints (Peralta, Triguero et al. 2016, Thalesgroup.com 2021) and DNA (Smith 2006, Amankwaa and McCartney 2018) are limited and very fragmented. After the 2004 tsunami disaster in Thailand, 46% of the victims were identified by dental records, as compared to only 19% by DNA and 34% by fingerprints. The dental identification method is an analogous visual comparison of the ante- and post-mortem dental records (Miki, Muramatsu et al. 2017, Alsalamah and Nuzzolese 2020).
The basis of this concept is that dental treatments are always very specific and unique (Pretty and Sweet 2001, Ata-Ali and Ata-Ali 2014). To further complicate matters, teeth are continually impacted by abrasion, disease, trauma, and dental treatment. Thus, the available ante-mortem data might not correlate well to the post-mortem data. Furthermore, treatment notation and information are not standardised, and it is exceedingly difficult to run an automatic search in a large, fragmented database.
Identifying the victim’s dentist, or, at the very least, the area where the victim was treated, is a mandatory prerequisite for a DVI search. Antemortem dental records can be very challenging if no other victim information is available. In fact, younger patients may have only orthodontic records. The search process can be accelerated dramatically by accessing the ever-increasing number of digital scans and cloud-based data storage systems.
Digital dental records must be retained, depending on national regulations, from years to decades (Charangowda 2010, Devadiga 2014). With digital dental records, new pathways are open for DVI. The next logical step is to find oral cavity characteristics with universality, uniqueness, invariability (stable throughout the life), and ease of access.
Monozygotic (MZ) twins cannot be distinguished by DNA analysis (Bell and Spector 2011) and they look very similar (phenotypes). Hence, one way to prove the uniqueness of an identification method is its ability to reliably distinguish MZ twins. This is compounded by the recent revelation that palatal morphology (palatal vault and surface texture) can differentiate MZ twins through intraoral scans (Simon, Liptak et al. 2020).
Rugoscopy (also known as palatoscopy, calcorrugoscopy) is based on the difference in palatal rugae pattern, and can distinguish among ethnic and race groups, offering great assistance during DVI (Hermosilla Venegas, San Pedro Valenzuela et al. 2009, Bajracharya, Vaidya et al. 2013, Azab, Magdy et al. 2016, Suhartono, Syafitri et al. 2016, Kommalapati, Katuri et al. 2017, Saadeh, Ghafari et al. 2017, Barbo, Azeredo et al. 2018, Basman, Puspita et al. 2018).
The palate is more resistant to burn deformation injury when compared to the skin (Muthusubramanian, Limson et al. 2005). It is stable over time and varies little after orthodontic treatment (Bailey, Esmailnejad et al. 1996, Abdel-Aziz and Sabet 2001, Ali, Shaikh et al. 2016, Lanteri, Cossellu et al. 2020).
The aim of this pilot study was to compare teeth and palate uniqueness using the intraoral scans (IOS) of MZ twins.
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