Discussion

The frontal sinus is widely recognized in forensic literature for its morphological uniqueness among individuals, which makes it a valuable anatomical structure for human identification. Located in the frontal bone and developed through cranial pneumatization, this sinus exhibits significant variation in shape, thickness, size, and symmetry [14–17]. These individual characteristics allow its use in human identification [6–8, 18–20].Traditionally, frontal sinus analysis has been carried out through two-dimensional (2D) radiographs or axial slices from computed tomography (CT), despite inherent limitations regarding morphological fidelity and superimposition of adjacent structures [9–11]. In the present case, comparative examinations using 2D radiography and CT were performed. These proved decisive for the application of AM and PM 3D modeling techniques, enabling detailed analysis of the frontal sinus and direct comparison with postmortem findings.

With technological advances, especially in imaging sciences, 3D methods have been progressively incorporated into forensic practice [6, 12, 13, 21, 22]. Computed tomography, particularly in its cone-beam modality (CBCT), enables accurate volumetric reconstructions of the skull, including the paranasal sinuses. This 3D visualization significantly improves anatomical interpretation and reduces errors derived from planar projections. In addition, 3D models can be stored, digitally manipulated, and quantitatively analyzed, which facilitates standardization of procedures and validation of findings [12, 13, 23].

3D–3D superimposition techniques have gained prominence as robust tools for human identification. By allowing quantification of congruence between two anatomical models, this approach offers a higher degree of accuracy compared with 2D comparisons or even mixed superimpositions [10, 24]. Studies such as Beaini et al. (2015) have demonstrated the applicability of 3D–3D comparison in frontal sinus analysis, reporting promising results in terms of accuracy and reproducibility [25]. Recent systematic reviews support the effectiveness of this method, even in structures that are difficult to standardize, including palatal rugae and sphenoid sinuses [21, 24–27]. In the Brazilian forensic context, where high-end imaging technologies such as CT are not universally available in all Forensic Institutes, methodological innovation becomes crucial to ensure the effectiveness and accuracy of human identification processes [28–34]. This case illustrates a promising development in this scenario by successfully applying a 3D–2D superimposition approach. Although methodologically challenging, it opens new possibilities for IMLs with more limited infrastructure. The 3D–2D superimposition technique was successfully applied to compare AM and PM models of the frontal sinus, enabling detailed evaluation of morphological compatibility between structures and contributing significantly to the identification outcome, thus confirming the method’s effectiveness.

Traditionally, forensic identification based on imaging has evolved from two-dimensional (2D–2D) analyses, as exemplified by conventional radiographic comparison, to three-dimensional (3D–3D) methods using CT-based volumetric reconstructions [21, 22]. However, the absence of CT scanners in many Brazilian Forensic Institutes imposes the need for adaptation and creative solutions. The 3D–2D methodology, which consists of superimposing a three-dimensional model (obtained from an original antemortem CT) onto a two-dimensional image (such as a postmortem radiograph), emerges as a highly effective and low-cost solution.

One of the main advantages of this technique is the ability to generate a 3D reference model from AM data – as among which are volumetric reconstruction and segmentation of the frontal sinus from an AM CT scan - and virtually superimpose it onto a PM 2D image. This process, performed entirely using open-source software, requires no licensing costs, making it accessible to institutions with restricted budgets. Moreover, the flexibility to rotate and rescale the 3D model in real time within a virtual environment minimizes visual inconsistencies inherent in purely 2D–2D superimposition. In 2D–2D comparisons, minimal positioning variations can lead to inconsistencies or require multiple radiographic acquisitions through trial and error to “reproduce” the original image. With 3D–2D superimposition, real-time adjustment of the 3D model ensures accurate comparison even when PM examinations are less precise [13].

This technique not only optimizes the identification process but also serves as a powerful incentive for less-equipped Forensic Institutes. By demonstrating that effective and efficient results can be achieved without massive investment in CT equipment, the emphasis shifts toward workforce training. Expertise in 3D technology and forensic imaging thus becomes the most strategic asset, enabling professionals to maximize available resources, for instance volumetric reconstruction and segmentation of anatomical structures from original AM CT scans, even when the Forensic Institute does not have its own CT scanner for PM examinations. Therefore, 3D–2D methodology is not only a viable alternative but also a pathway to democratizing access to advanced forensic identification techniques in Brazil, promoting excellence and justice at all levels [29–31, 34].

The incorporation of 3D technology into forensic anthropology represents a significant advance in forensic science. The use of the frontal sinus as a comparative structure in 3D–2D modeling illustrates the potential of digital techniques for identifying individuals who cannot be identified by traditional methods. Furthermore, this methodology can be extended to other anatomical regions, such as the sphenoid sinus, palate, and dental structures, contributing to the consolidation of more objective, precise, and reproducible methods [21, 26, 27]. Although it remains a challenge, including protocol standardization and the interpretation of damaged images, continuous progress in artificial intelligence and computational modeling points to a promising future for human identification based on three-dimensional imaging [26, 27].

This case report highlights the importance of forensic anthropologists and forensic odontologists in human identification, particularly in cases involving frontal sinus analysis through CT imaging combined with 3D reconstruction. The use of 3D–2D superimposition technique proved to be a highly effective tool, enabling detailed morphological comparison between AM and PM examinations. The accuracy observed in this process demonstrates the potential of this methodology in obtaining objective, reliable, and reproducible results, even in complex contexts such as advanced decomposition. Thus, the combination of expertise in 3D technology, anatomical knowledge, forensic imaging, and quantitative methods reaffirms the value of forensic dentistry as an essential pillar of human identification.