3D Evaluation of Palatal Rugae for Human Identification

Palatal rugae, also known as plicae palatinae transversae and rugae palatine, are situated in the anterior third of the hard mucosal palate in the roof of the mouth. While there is literature suggesting that the palatal rugae could be used for human identification, most of these studies use two-dimensional (2D) approach. Scanning three-dimensional (3D) technology could facilitate the computerized matching of palatal rugae patterns in a manner comparable to the current gold standard for assessing fingerprints. The aims of this study were to evaluate palatal rugae patterns using three-dimensional (3D) digital models; to compare the most clinically relevant digital model conversion techniques for identification of the palatal rugae; to develop a protocol for overlay registration; to determine changes in palatal rugae individual patterns through time and following orthodontic treatment; and to investigate the efficiency and accuracy of 3D matching processes between different individuals’ patterns. Initially, the palatal rugae area for each digital impression was isolated as a separate 3D image, and two impressions were registered by manual alignment followed by global registration. Five cross sections in the anteroposterior dimension and four cross sections in the transverse dimension were computed which generated eighteen 2D variables. In addition, thirteen 3D variables were defined using the annotation function in the software: 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 thirty one different landmarks were evaluated in this study. The results demonstrated that two-dimensional (2D) images and linear measurements in anteroposterior and transverse dimension 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 rugae patterns. The 3D landmarks showed no statistically mean differences over time and as a result of orthodontic treatment. No statistically mean difference was found between different digital model conversion techniques, between OrthoCAD™ and Ortho Insight 3D™ and between Ortho Insight 3D™ and the iTero® scans, when using twelve 3D palatal rugae landmarks for comparison. Although all twelve palatal 3D landmarks could be used for human identification over time, certain landmarks showed more significant impact on the matching process and were arranged by strength and importance. In this study, a three-dimensional (3D) approach was developed and utilized for human verification and identification using the palatal rugae pattern. Proposed values for 3D palatal landmarks were introduced that could be useful in biometrics and forensic odontology for human verification or identification in cases of traffic accidents, in mass casualty incidents such as aviation and natural disasters, industrial explosions, or acts of terrorism. This new method corresponds with the latest trend of routine use of 3D digital study models in dentistry and orthodontists for diagnosis and treatment planning. Nowadays, those models are integrated in the personal electronic health record and can be easily requested and accessed by forensic institutes.