The Region of Interest in Boundary Calibration for Palatal Rugae Image of Forensic Identification

Objective To examine the method of least-square fitting for calibrating the palatal rugae boundary. Methods According to the distribution of the teeth, the feature points were selected; when they were fit, the boundary of the palatal rugae area was created, thereby constructing a mask. The mask was used to remove the part located outside the boundary and filter out the interference. Three samples were utilized for the experiments and analyses to come. Results To evaluate the quantitative results of the fitting curves, the correlation coefficients （r） of the samples and the relationship between the actual mean value and ideal mean value was obtained through six fitting processes. The differences between the actual mean and ideal mean were found to be significantly small （from 0.285 7 to 2.500 0） in the six fitting processes, with the range of r close to 1 （from 0.989 6 to 0.999 5）. Conclusion The effect of the cubic polynomial fitting method adopted in this study was stable.The proposed boundary calibration method can effectively locate the palatal rugae boundary and remove the interference area, further promoting the practice of forensic identification.