Development of a Software Program for the Automatic Calculation of the Tooth-Pulp Volume Ratio on the Cone-Beam Computed Tomogram

Abstract

Tooth is one of the most valuable tissues for the forensic purpose because of its mechanical, chemical and physiological stability over time comparing other forensic specimen. Its own physical and biological properties have been used for identification or age estimation in living individuals as well as dead bodies, while its hard tissue provides a protective shell for DNA inside of it in the body from harsh environment. The decrease of pulp cavity of the tooth by deposition of secondary dentin with aging is one of the properties of the tooth tested the most frequently for age estimation. Various methods using tooth-pulp ratio have been developed and presented based on sectional specimen or two-dimensional or three-dimensional radiographic images. However the results are not consistent yet in its validity, reliability, and usability as an age-estimation method. In this study, we developed and introduced a software to extract the volume of tooth and pulp automatically from the cone-beam computed tomography (CBCT) that can guarantee the more objective, reproducible, and timesaving way to measure the tooth-pulp volume ratio. Once the threshold density between the tooth, pulp cavity, and bone are defined using an automated tool integrated in the developed software on one cross-sectional CBCT image, regions of interest (ROI) are extracted automatically in the rest of the cross-sectional images to navigate the three dimensional volume of the tooth and pulp cavity and the tooth-pulp volume ratio is finally calculated. This process is done automatically by just indicating the center of the pulp cavity and the area where the tooth is located. The software tracks the change of density from the point pointed at the center of the pulp cavity to the boundary drown to indicate the area where the tooth is located so as to find the border of each structure, which can exclude the any possibility of subjective judgment by the examiner. Of course, the result can be corrected, if necessary, by the examiner as well as by changing the threshold of density of hard tissue. In further studies based on a large-scale sample, the most proper threshold to present the most significant relationship between age and tooth/pulp volume ratio and the tooth correlated with age the most will be explored. If the software can be improved to use whole CBCT data set rather than just sectional images and to detect pulp canal in the original 3D images generated by CBCT software itself, it will be more promising in practical uses.