Study On Forensic Identification By The Morphological Changes Of Palatal Rugae Following Orthodontic Treatment

Objective:As a mark of forensic medicine, the palate rugae play an important role in forensic dentistry medicine. This study is to identify the individuality of the palate morphology by using the model analysis and Rugae Image Identification System(RIIS),and to assess the uniqueness and the stability of the palatal rugae following orthodontic treatment, in order to explore the significance of palatal rugae morphology in forensic identification, to study the influence of the morphological changes of palate in identification application after orthodontic treatment,and evaluate the Rugae Image Identification System(RIIS).Materials and methods:70 orthodontic patients were randomly selected from The Hospital of Stomatology of Shanxi Medical University. Their maxillary casts and digital pictures of rugae patterns of pre- treatment and post-treatment( in standard conditions) were retrieved forthe morphometric analysis.By using casts analysis and the digital information recognition system of the palate rugae in palatal winkle database, this study analyzed the morphological changes. Ten observers were selected to test individuality by matching the pre-and post- samples.The average correct percentages(each observer) of matching results were calculated and analyzed by using paired t-test. The results obtained from the model analysis were compared with the results obtained through the Rugae Image Identification System(RIIS).All data were inputted to the computer, using SPSS22.0 software.Results:(1) The incidence of palatal rugae morphological changes showed the following results: changes related to the displacement of lateral ends in the anteroposteriordirection(45.7%); changes related to the displacement of lateral ends in the mediolateral direction(40%);changes related to the displacement of medial ends in the anteroposterior direction(32.9%); changes related to the displacement of medial ends in the mediolateral direction(17.1%); changes in length of palatal rugae( 28.6%); changes in the number(segmentation)(4.3%),(unification)(2.9%); changes in the orientation(1.4%);changes in the shape(1.4%).(2) The palatal rugae patterns were highly individualized without any identical patterns in the study. Individual characteristic tests of the palate rugae reached the correct matching rate of 100 percent in the digital information recognition system.(3) The mean percentage of correct matches between the post-treatment casts and their duplicates(post-treatment)is significantly higher(99.05%),compared with the matches between pre-and post-casts(92.19%).Similarly, the mean percentage of correct matches between the post-treatment pictures and the others(post-treatment)is obviously higher(100%),compared with the matches between pre- and post- pictures(95.67%).(4) By comparing the results obtained from the model analysis with the results obtained by the Rugae Image Identification System(RIIS), the difference(P<0.05) was statistically significant. The mean percentage of correct matches of palate(pre- and post-)is higher with the Rugae Image Identification System(RIIS).Conclusion:Palatal rugae are unique to every individual.Orthodontic treatment induces various morphometric changes to palatal rugae patterns.Although they have limited influence on the individuality of palatal rugae,human identification seems potentially complicated based on it. The Rugae Image Identification System(RIIS) has more advantages than the traditional recognition method in the application of identification of the palate following orthodontics.