In vivo dental implant micro-movements measuring with 3D digital image correlation method

Abstract

Implant stability is one of the principal factors in the clinical success of implant therapy. Different methods to measure implant stability have been proposed but, so far, there is no clinical method available to directly measure implants micro-movements. Tridimensional Digital Image Correlation (3D DIC) method is a noncontact optical measurement system that can track an object’s surface displacement field in a series of images. This system uses the digital image of two high speed photographic cameras and the principles of optics to stereo-triangulate the tridimensional surface full-field contour of an object. 3D DIC requires a gray value pattern on the object surface. Then an algorithm defines a field of small neighborhoods called subsets which are small N × N pixels boxes with an array of pixel gray-scale values. 3D DIC uses a matching advanced algorithm allows to determine translation, rotation and deformation of these subsets in a series of images with relation to a reference image of fixed subsets. Thereby, the method tracks these subsets on the object surface during deformation which is the principle of digital image correlation. The result is a time history of the objects surface displacements field by video correlation between the initial image (referenceimage) and the subsequent images. 3D DIC has been used to measure implant micro-movements In Vitro, and despite not being a clinical method, it should be capable of direct objective implant micro-movement measuring, useful for clinical studies.