# The Use of a 3D Image Comparison Program for Dental Identification
## 1 Introduction
An intraoral scanner is small, easy to maneuver, and can be easily used on patients with small mouths, making it easy for dentits to operate. Therefore, its use in the examination room is also feasible. If STL data prepared by a dental clinic are available in advance, an intraoral scanner can be used at the time of identification to collect more accurate intraoral information than when information is collected by visual examination and then transcribed onto a dental chart for matching. As a result, the data obtained from a cadaver and the data stored in the dental clinic can be matched on a computer, which can improve the efficiency of the work. In addition, if the data are stored as digital data, it will be possible, in the future, to prevent the loss of data before death by storing the intraoral conditions in a place where there is little risk of loss, even in the event of a disaster. Currently, comparative studies of identification using 3D image data include evaluating bone anatomical features, such as the frontal sinus, sphenoid sinus, and cleft palate [15; 16; 17; 18]; superimposing 3D data on dental models of maxillary first and second molars [19]; evaluating from the morphology of anterior teeth [20; 21]; and implementing 3D data identification software studies [22; 23]. However, the comparison of 3D data is time-consuming due to the large number of feature points [23]; thus, the authors believe that its current use is not realistic considering its role as a screening tool for dental identity verification. Although comparing two-dimensional images can be thought of as comparing photographs, it is extremely difficult to compare two photographs. The position of the light source and the angle at which the camera was used can result in completely different photographs of the same subject [24]. The use of STL data makes it possible to store intraoral information under the same conditions, thus solving the problem of comparing photographs. If it becomes possible to compare anatomical features, such as the arrange ment of the dentition and tooth contours, this may be useful in cases where there are no treatment scars and features that were difficult to identify using conventional identification methods that cannot be extracted from medical records. When comparing STL data, which are three-dimensional, the number of feature points to be compared is enormous, and the computational load required for feature extraction and matching processes is extremely high, requiring long comparison times [25]. Therefore, in this study, the STL data were sectioned at a specific reference plane, and a cross-sectional image was created as the comparison image. By creating the comparison image at the reference plane, the same image can always be created from the STL data, and the authors believe that this is optimal for identification. In this paper, the authors report a new identification method using an image comparison program (AKAZE) [26; 27; 28; 29] and binarized images created from cross-sectional images of left unilateral STL data of the upper and lower jaws, obtained by using an intraoral scanner.