A method for segmentation of dental implants and crestal bone

Purpose   Medical imaging and in particular digital radiographic images offer a great deal of information to dentists in the clinical diagnosis and treatment processes on a daily basis. This paper presents a new method aimed to produce an accurate segmentation of dental implants and the crestal bone line in radiographic images. With this, it is possible computing several measures to biomechanical and clinical evaluation of dental implants positioning and evolution. Methods   The proposed segmentation method includes two major steps: (1) the preprocessing that combine denoising filters, morphological operations and histogram threshold techniques and (2) the final segmentation involving made-to-measure adjusted and trained active shape models for detecting the precise location of the intended structures. Results   Resulting measurements were compared to manual measurements made by experts on representative radiographs from patients. The calculated intraclass correlation coefficient was 0.75 and showed good reliability of the method, and the Bland-Altman analysis showed 95 % of the values within the limits of agreement. The mean of the differences between the manual and method-driven measurements was 0.049 mm (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$-0.137; -0.040$$\end{document}) 95 % CI, inferior to the established limit (0.15mm). Conclusions   It was demonstrated that the method achieved a precise segmentation of the intended structures. The validation process on standardized periapical radiographs showed good agreement between the manual measurements and the ones produced by the new method. Future work will be focused on making the method more robust to densitometry changes and to validate the method on non-standardized radiographs.