Analysis of dental biometric methods in forensic dental identification

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INTRODUCTION

Today, escalating geopolitical tensions worldwide have resulted in open military conflicts and the emergence of new hotspots across multiple regions. The multifactorial destructive effects of modern weapons often complicate the subsequent forensic identification of service members and civilians because the remains may be partially or completely destroyed. Consequently, analyses of current identification practices have highlighted the need to systematize distinctive somatic characteristics based on the decedent’s morphofunctional, anthropometric, and other external features. Specialized knowledge in dental morphology has successfully supplemented efforts to identify systemic and structural classification elements that enhance the effectiveness of forensic identification.

Available evidence indicates multiple efforts to examine tooth contour characteristics and dental morphology in order to further develop existing theoretical models in dentistry [1]. Investigators have also reported experiments assessing correlations between crown height and mesiodistal dimensions of anterior teeth, taking sexual dimorphism into account, to support human identification. Specific dental morphometric studies have focused on measuring the distance from a set of occlusal surface points to the cementoenamel junction under normal conditions and in cases of enamel hypoplasia [2]. The methodology of odontometry has been most thoroughly developed in anthropological research and in studies of ethnic odontology. Earlier forensic dental investigations, including those evaluating dental radiographs using computer-based color densitometric decoding, have also contributed to the field [3]. Moreover, most studies on identification-related morphology rely on a limited set of odontometric techniques. Selection of these methods depends on the complexity of the forensic task and access to appropriate technical resources.

In light of these considerations, the modernization of existing personal identification methods and the integration of automated biometric systems into forensic dental identification—alongside orthodontics, dental radiology, and other advancing fields of dentistry—remain highly relevant.

This review aimed to analyze scientific sources addressing current issues in personal identification through the use of specialized data in dental morphology and biometrics.

SEARCH METHODOLOGY

We conducted a search and analysis of current scientific publications using major scholarly databases, including PubMed, PubMed Central, Scopus, eLIBRARY.RU, ResearchGate, and Google Scholar. Thirty international scientific sources formed the basis of this review.

SCIENTIFIC, PRACTICAL, AND THEORETICAL FOUNDATIONS OF IDENTIFICATION AMELOGLYPHICS

Contemporary research describes the use of various tools for forensic personal identification, including personal identification codes, photographs, iris scanning, fingerprint analysis, and DNA profiling. In military practice, personal identification of service members is traditionally ensured through mandatory identification tags—durable metal tokens bearing a unique service number. In addition to an identification number, tags worn on the neck may contain other personal data, including name, surname, unit affiliation, blood group, and religious preference. This supplementary information is intended to facilitate the identification of those killed or injured in combat. However, many researchers note that traditional identification methods often fail when modern weapons, military equipment, large-scale technological accidents, or mass disasters result in extensive destruction of human remains.

Forensic experts frequently encounter highly challenging situations in which the only material available for analysis consists of calcined tissue remnants, such as bone fragments or isolated teeth. In such cases, teeth become the only viable means of identification, and given the uniqueness of enamel surface patterns, their scientific and practical value increases considerably [4]. Sha et al. outlined the primary methods used to obtain enamel microrelief impressions and discussed their potential application in personal identification [5]. Citing specialized sources, the authors note the practical use of multiple methods of forensic dental identification, including comparison of postmortem and antemortem dental records, rugoscopy, cheiloscopy, denture marking, DNA analysis of dental pulp, bite mark assessment, and other available approaches. Collectively, these specialized techniques for evaluating the microtexture of dental enamel have evolved into an independent subfield of forensic dental identification known as ameloglyphics (from the Latin amelo, meaning enamel, and glypho, meaning carving). Furthermore, the term toothprint is commonly used to describe the qualitative characteristics of the enamel surface [6].

UNIQUE FEATURES OF TOOTH ENAMEL MICROSTRUCTURE

Enamel undergoes a complete developmental cycle, and any alterations within its matrix should be regarded as defects of structural organization. The morphology of enamel prisms reflects the morphology of ameloblasts in a species-specific manner. As an ectodermal product of ameloblast activity, enamel is the hardest tissue in the human body [7]. Researchers emphasize several histologic characteristics of enamel that arise from changes in the direction of enamel prism bundles and are visible on longitudinal ground sections. These include alternating regions of enamel with longitudinally and transversely oriented prisms, forming the so-called parazones and diazones. When examined under reflected light, longitudinal enamel sections reveal these zones as alternating light and dark bands oriented perpendicular to the enamel surface, approximately 100 µm in width, corresponding to 10–13 enamel prisms [8]. These bands resemble fingerprint patterns and are referred to as Hunter–Schreger bands [9]. In addition, ground enamel sections demonstrate incremental growth lines associated with the periodicity of mineralization and organic matrix deposition, known as striae of Retzius. On longitudinal sections, they appear as symmetrical yellow-brown arcs running obliquely from the enamel surface toward the dentinoenamel junction; on transverse sections, they form concentric circles or rings. Striae of Retzius are most clearly expressed on the enamel surface of permanent teeth, whereas they are less pronounced in the enamel of primary teeth, formed during both prenatal and postnatal periods. In any disturbances of amelogenesis, including those related to systemic disease, the number of striae of Retzius typically increases.

The fundamental structural and functional unit of enamel is the enamel prism, which traverses the full thickness of enamel in curved bundles oriented perpendicular to the dentinoenamel junction. In the cervical and central regions of the crown, prisms may assume a horizontal orientation; near the incisal edge and the slopes of cusps, they run obliquely; and toward the incisal edge or the cusp apex, they become nearly vertical.

In cross-section, enamel prisms exhibit an oval configuration resembling an arched vault, with a diameter of 3–5 µm that increases from the dentinoenamel junction toward the enamel surface. Each prism consists of tightly packed hydroxyapatite crystals and other minerals, with a calcium content ranging from 6 to 14 atoms. The highly ordered crystal arrangement aligns parallel to the prism’s long axis, forming a wider “head” region and a narrower “tail,” where crystals fan outward. The cross-striated appearance of prisms reflects variations in enamel mineralization, producing alternating light and dark bands. The peripheral zone of each enamel prism forms an organic sheath characterized by reduced crystal density, heterogeneous crystal orientation, and increased protein content.

The spatial grouping of enamel prisms ultimately generates a characteristic surface texture known as perikymata. These histologic features manifest clinically as unique micro-patterns formed by the terminal portions of enamel prisms on the tooth surface.

EVALUATION OF METHODS FOR OBTAINING ENAMEL SURFACE IMPRESSIONS

Extensive data indicate a wide range of contemporary identification techniques, including analysis of photographs, passwords, lip prints, dental patterns, and DNA profiling. Among these, biometric verification methods, such as fingerprint analysis, iris scanning, and facial recognition, hold particular prominence. According to Christopher et al., methods that rely on teeth as a reliable evidentiary basis, depending on the status of the deceased, are gaining increasing significance [10].

The traditional approach to reproducing enamel prism surface patterns involves using cellulose acetate sheets and various impression materials, primarily elastomeric. Researchers highlight the practical effectiveness of the three sequential stages used to reproduce the enamel prism microrelief in ameloglyphic analysis for personal identification: acid etching, acetate peel production, and automated biometrics [11]. A characteristic feature of acid etching is the uneven dissolution of surface enamel and partial removal of the mineral component of the prism sheath. The depth of this effect depends on several factors, including the type and concentration of the acid, etching and rinsing time, as well as the chemical composition and degree of enamel mineralization. In vivo studies most commonly employ a 10% phosphoric acid gel. Published data describe typical enamel etching patterns, including preferential dissolution of the prism core or prism periphery, as well as disruption of prism structure [12].

The peel technique is a simple, rapid method for producing replicas of acid-etched hard tissue surfaces on acetate film. Originally adopted from paleobotany—where it was used to examine the texture and structure of carbonate rocks and fossilized plants—this method has been successfully modified for microscopic examination of tooth hard tissues under reflected and transmitted light [13].

Reports also describe the use of biometric processing of enamel impression photomicrographs with VeriFinger SDK software (Neurotechnology, Lithuania), versions 5.0 and 6.5. This software entered the biometric system integrator market in 1998. The term biometrics (from the Greek βίος, meaning life, and μετρέω, meaning to measure) refers to automated recognition of individuals based on their biological and behavioral traits. Biometric systems digitally authenticate individuals using characteristic physical or behavioral features such as three-dimensional facial and body images, voice samples, fingerprints, hand vein patterns, blood group, or specialized corneal imaging. Specialists view the application of biometrics for automated recognition as a subset of biostatistics, distinguished by high reliability and strong predictive value for positive identification. Available publications indicate that digital analysis of biometric data is a unique tool for identifying any individual and can be performed in a wide range of settings without the need for preparatory training of the subject or operator [14].

The development and refinement of ameloglyphic methods, which are steadily gaining recognition in the scientific community as an effective tool for personal identification, appear particularly promising. It should be emphasized that the uniqueness of enamel microtexture patterns can serve as reliable evidentiary material during forensic investigations, especially when combined with other identification approaches. Researchers propose creating archival databases of dental records for specific social and professional groups who face increased risks to life and health or who are deployed to regions with political instability. They also note the need for regular updates of these databases to account for enamel wear and to maintain the clinical relevance of the information [15]. When comparing fingerprint analysis with ameloglyphics, experts note that fingerprint patterns have a relatively simple structure composed of a limited set of elements—loops, whorls, and arches. In contrast, toothprints exhibit a more complex combined architecture that includes a wide array of principal authentication elements and their subpatterns.

Manjunath et al. evaluated the effectiveness of various techniques used to record enamel prism microrelief with the aim of optimizing personal identification procedures [16]. Their comparative study examined methods for obtaining enamel surface impressions using cellulose acetate film, cellophane tape, and elastomeric impression materials.

Earlier, Füsun et al. reported attempts to apply the acetate peel method for three-dimensional visualization and analysis of dental morphological features, avoiding the need for routine manual preparation and specimen processing of dental materials [17].

Manjunath et al. also used experimental modifications of cellulose acetate techniques for personal identification purposes [18]. Referring to data from Gupta et al. [15, 19], the authors emphasize not only the uniqueness of enamel prism microrelief among individuals, but also the significant variability of enamel prints obtained from the same person. Moreover, in discussing the potential of dental identification, investigators note the relative resistance of modern restorative dental materials to postmortem destruction compared with human soft tissues and organs.

The cellophane tape technique involved placing a fragment of cellophane tape onto a pre-etched enamel surface, followed by adaptation to the tooth surface through manual pressure applied with a cotton cloth placed over the tape. The tape was then transferred onto a glass slide for light microscopic examination and for obtaining photomicrographs of the impressions. For the experiment, investigators used a microscope with ×40 magnification and a digital camera with 1.4× magnification. The impression technique, in turn, required the use of an elastomeric impression material with a low-viscosity wash to reproduce fine enamel microstructures. After the material set, the impression was examined under a stereomicroscope. Unlike methods employing a light microscope, the use of a stereomicroscope in this setting was necessary because the impression material lacks translucency. Preparation of the photomicrographs for all methods consisted of cropping the image centrally using the Picture Manager software (Microsoft, USA) to achieve a final resolution of 2000 × 1500 pixels [18]. Photomicrographs of enamel prism impressions were analyzed using VeriFinger SDK v. 5.0. Ramenzoni et al. were among the first to attempt automated biometric analysis of Hunter–Schreger bands on enamel surfaces using this software for the purpose of personal identification [20]. Later, several other researchers also confirmed the effectiveness of VeriFinger SDK v. 5.0 as a reliable biometric tool for evaluating enamel prism microrelief. The software authenticates patterns formed by the tail regions of enamel prisms, which appear as multidirectional groups of lines on enamel impressions. The extracted data are automatically stored in the system’s electronic database as sets of small points (minutiae), each assigned a unique identification number to enable subsequent verification. Each set of virtual points corresponds to specific morphologic microfeatures on the enamel surface and may be visualized as discrete dots, depressions, short lines, empty spaces between lines, as well as bifurcations and branching patterns.

Experimental results [20] demonstrated that enamel surface identification was most accurate when cellulose acetate film was used to obtain the impressions. Notably, the enamel surfaces corresponded precisely to the analyzed impressions, without voids, discontinuities, or smearing of the microrelief. During repeated comparison of data obtained from identical enamel surfaces, the VeriFinger SDK software detected matches between the evaluated parameters and the original identification numbers stored in the database. These findings demonstrate that coordinate-based authentication of minutiae clusters accurately reflects the spatial arrangement of the analyzed enamel microstructures.

Moreover, experts emphasize that the use of cellophane tape and elastomeric impression materials produced low-quality images of enamel prism texture, which resulted in unsuccessful identification of the examined teeth [21]. The analysis demonstrated partial voids and graphic fragmentation of the obtained impressions, with displacement of gaps into adjacent areas during repeated examination of the same surfaces. As a result, the spatial distribution of minutiae varied substantially, and their identification numbers no longer matched the original values. In other words, the VeriFinger SDK software failed to authenticate the enamel prism patterns because it could not correlate the prism configuration of the examined tooth with the identification number assigned during the initial analysis. However, when impression materials are used for identification purposes, investigators note the need for experimental selection of materials with optimal viscosity and defined physicochemical properties [22]. In addition, cellophane tape contains a thin layer of adhesive on one side, and its high viscosity further interferes with accurate reproduction of enamel microrelief. In contrast, acetone acts as a solvent and removes the cellulose acetate film layer, causing targeted deposition of dissolved particles along surface irregularities of enamel and thereby improving the accuracy of the resulting impression.

According to specialists, cellulose acetate film remains a simple, precise, relatively rapid, and cost-effective method for recording the tail regions of enamel prisms. However, several limitations persist, including difficulty capturing a complete “enamel landscape” of prism patterns when applying the film to an uneven tooth surface [22].

Thus, analysis of experimental outcomes [23] demonstrated the advantage of cellulose acetate for obtaining enamel impressions because it preserves a substantially greater number of microrelief minutiae than alternative methods. Consequently, the informational richness and precision of the prism-tail images obtained using cellulose acetate film allow this technique to be recommended for forensic identification. Building on this conclusion, specialists propose further optimization of the concept through the introduction of fiber-optic laser scanning technology into identification research [23]. They suggest that the use of modern digital technologies and specialized software will enable simultaneous acquisition of impressions from the entire dentition and support advanced computational analysis of enamel microrelief. Such developments would facilitate continued research into familial, population-based, and ethnographic differences in enamel prism microrelief patterns.

Specialists conducted an in vitro evaluation of the terminal portions of enamel prisms in anterior primary teeth using automated biometric technology to assess the feasibility of identification. The authors maintain that information derived from enamel prism microtexture may serve as an analog to fingerprinting, although a more reliable and accurate one [24]. Few studies have examined enamel prism impressions, and no experimental investigations of primary teeth have been reported.

To record impressions of intact anterior primary teeth, investigators used the cellulose acetate peel technique followed by biometric processing of photomicrographs [24]. Analysis was performed with VeriFinger SDK v. 6.5. The teeth were first cleaned in a 10% formalin solution and then etched on the middle third of the vestibular surface with 37% phosphoric acid for 20 seconds. After rinsing and drying, a drop of acetone was applied to the etched surface, which was then covered with a cellulose acetate film for 20 minutes. Partial dissolution of the film allowed deposition of the solution along the enamel surface irregularities, after which the film was transferred onto a glass slide for light microscopic analysis. The resulting photomicrographs were subjected to biometric processing to recognize, analyze, and capture enamel microrelief patterns as sequences of multidirectional lines. Notably, the results were evaluated independently by two experts.

The investigators analyzed the microtexture of terminal enamel prism segments based on previously established classifications. Six fundamental prism-end patterns were identified and documented: wavy branched (WB), linear branched (LB), linear unbranched (LUB), whorl (W), loop (L), and spindle-shaped (SL) [25]. The wavy branched pattern was the only type consistently predominant across all samples, and all branched variants were categorized as distinct subpatterns. The remaining pattern types did not occur in isolation but appeared in combination with others, most commonly with the branched wavy and linear forms [25, 26].

Leading experts draw clinicians’ attention to fingerprint analysis, informally regarded as the benchmark for identification because of its exceptional simplicity, accuracy, and practical convenience. In this method, biometric software extracts a set of key parameters—so-called minutiae—from fingerprint impressions. Morphologically, minutiae represent local ridge breaks and ridge endings, depressions, clusters of points, and bifurcations, which appear as distinct dark lines [27]. This similarity has prompted experimental use of fingerprint biometric software as a test platform for analyzing toothprints in forensic identification. Researchers also emphasize the positive correlation between fingerprint patterns and enamel surfaces, a finding indirectly supported by their shared ectodermal origin [28].

Juneja et al. experimentally demonstrated that toothprints remain highly informative for forensic analysis even after exposure to acids and extreme temperatures [29]. Furthermore, comparative studies evaluating the effects of extremely high temperatures—up to 1000 °C—on teeth from individuals of various age groups showed greater thermal resistance in primary teeth compared with permanent teeth [30]. Reports also highlight specific histologic features of primary teeth compared with permanent teeth, which support their potential use as a reliable source of information for the forensic identification of children [31]. Characteristic features contributing to the thermal stability of primary teeth include differences in thermal expansion coefficients, higher enamel prism density, and increased prism diameter, especially near the dentinoenamel junction [32, 33]. A unique morphological feature of primary teeth is the parallel orientation of hydroxyapatite crystals, which produces a uniform enamel thickness. This arrangement contributes to homogeneous thermal expansion under heat exposure and reduces the likelihood of tissue destruction. However, investigators acknowledge that the main limitation of the study was the absence of information regarding the sex and ethnicity of the individuals whose teeth were examined [33]. Therefore, further research is needed to determine potential associations between these factors and the quality of enamel impressions. Additional priorities include identifying intergroup and intragroup similarities in enamel prism-end patterns across populations and comparing their frequencies in primary and permanent teeth. In permanent teeth, the general spatial orientation of enamel prisms is perpendicular to the dentin surface; in the cervical region, prisms deviate toward the root or extend outward. In primary teeth, prisms in the cervical and middle thirds of the crown run horizontally, gradually becoming more vertical in the occlusal third [34].

Analysis of enamel pattern morphology has allowed investigators to distinguish several classes, defined by the configuration of their characteristic whorl structures. These classes and subclasses include branched and unbranched wavy patterns, branched and unbranched linear patterns, open and closed whorls, loop patterns, and spindle-shaped forms [35].

Summarizing these findings, investigators emphasize the priority of using dental evidence as the method of choice for establishing identity—particularly in cases involving severe fragmentation, decomposition, burning, or skeletonization of human remains [36]. Available evidence confirms the widespread use of teeth as a reliable tool for forensic dental identification, as well as the growing role of ameloglyphics as an effective method of biometric analysis [37, 38]. Teeth become especially valuable when alternative biological material is limited or entirely unavailable, or when other avenues of forensic examination cannot be pursued.

CONCLUSION

Leading experts consider ameloglyphics a highly promising independent scientific discipline in the development and application of methods for personal identification. Priority directions for advancing this innovative field include the creation of digital techniques for reproducing, editing, and analyzing precise enamel impressions, as well as the development of specialized software capable of intelligent processing, storage, and rapid use of these data. Addressing the relevance of this emerging discipline, researchers highlight the need for continued scientific investigation to identify practical opportunities for integrating core concepts of dental identification into neural network–based and artificial intelligence platforms. Formulating such forward-looking objectives provides a strong impetus for further development of a fundamental methodological framework at the intersection of modern dental science, forensic investigation, and computational technologies to optimize current personal identification tasks.

ADDITIONAL INFORMATION

Author contributions: A.E. Verkhovskiy: resources, writing—original draft, writing—review & editing; S.V. Apresyan: supervision, conceptualization, formal analysis, writing—review & editing; A.G. Stepanov: methodology, conceptualization, data curation, formal analysis, writing—review & editing. All the authors approved the version of the manuscript to be published and agreed to be accountable for all aspects of the work, ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Funding sources: No funding.

Disclosure of interests: The authors declare no relationships, activities, or interests (personal, professional, or financial) with third parties (for-profit, not-for-profit, or private entities) whose interests may be affected by the content of this article. The authors also report no other relevant relationships, activities, or interests within the past three years.

Statement of originality: In preparing this review, the authors used previously published information (textual data available electronically on the Internet). References to all sources used are provided in the reference list.

Data availability statement: The editorial policy regarding data sharing does not apply to this work, as no new data was collected or created.

Generative AI: No generative artificial intelligence technologies were used to prepare this article.

Provenance and peer review: This paper was submitted unsolicited and reviewed following the fast-track procedure. The peer review process involved two external reviewers, a member of the editorial board, and the in-house scientific editor.

About the authors

Andrey E. Verkhovskiy

Smolensk State Medical University

Author for correspondence.
Email: a.verhovskii@mail.ru
ORCID iD: 0000-0002-1627-9099
SPIN-code: 7617-8166

MD, Cand. Sci (Medicine), Associate Professor

Russian Federation, 2 Kashena st, Smolensk, 214012

Samvel V. Apresyan

Peoples’ Friendship University of Russia

Email: apresyan@rudn.ru
ORCID iD: 0000-0002-3281-707X
SPIN-code: 6317-9002

MD, Dr. Sci. (Medicine), Professor

Russian Federation, Moscow

Alexandr G. Stepanov

Peoples’ Friendship University of Russia

Email: stepanovmd@list.ru
ORCID iD: 0000-0002-6543-0998
SPIN-code: 5848-6077

MD, Dr. Sci. (Medicine), Professor

Russian Federation, Moscow

References

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