3D evaluation of palatal rugae for human identification using digital study models

BACKGROUND: While there is literature suggesting that the palatal rugae could be used for human identification, most of these studies use two-dimensional (2D) approach. AIM: The aims of this study were to evaluate palatal ruga patterns using three-dimensional (3D) digital models; compare the most clinically relevant digital model conversion techniques for identification of the palatal rugae; develop a protocol for overlay registration; determine changes in palatal ruga individual patterns through time; and investigate the efficiency and accuracy of 3D matching processes between different individuals’ patterns. MATERIAL AND METHODS: Five cross sections in the anteroposterior dimension and four cross sections in the transverse dimension were computed which generated 18 2D variables. In addition, 13 3D variables were defined: The posterior point of incisive papilla (IP), and the most medial and lateral end points of the palatal rugae (R1MR, R1ML, R1LR, R1LL, R2MR, R2ML, R2LR, R2LL, R3MR, R3ML, R3LR, and R3LL). The deviation magnitude for each variable was statistically analyzed in this study. Five different data sets with the same 31 landmarks were evaluated in this study. RESULTS: The results demonstrated that 2D images and linear measurements in the anteroposterior and transverse dimensions were not sufficient for comparing different digital model conversion techniques using the palatal rugae. 3D digital models proved to be a highly effective tool in evaluating different palatal ruga patterns. The 3D landmarks showed no statistically significant mean differences over time or as a result of orthodontic treatment. No statistically significant mean differences were found between different digital model conversion techniques, that is, between OrthoCAD™ and Ortho Insight 3D™, and between Ortho Insight 3D™ and the iTero(®) scans, when using 12 3D palatal rugae landmarks for comparison. CONCLUSION: Although 12 palatal 3D landmarks could be used for human identification, certain landmarks were especially important in the matching process and were arranged by strength and importance. Proposed values for 3D palatal landmarks were introduced that could be useful in biometrics and forensic odontology for the verification of human identity.