A double scanning procedure for visualisation of radiolucent objects in soft tissues: Application to oral implant surgery planning

A procedure for visualization of radiolucent objects in CT scan images is proposed and applied to endosseous oral implant surgery planning. Many of these patients have a removable prosthesis, and visualisation of this prosthesis proves to be advantageous during planning. Such a prosthesis is usually quite radiolucent and thus not distinguishable on CT. The technique glues small markers on the prosthesis, and then scans it, giving a first image set. A second image set of the patient with the intraoral marked prosthesis is then acquired. From the first set, a surface rendered model of the prosthesis can be constructed. From the second set, a surface model of the bone can be made, and the markers indicate the position of the prosthesis in the mouth of the patient. The prosthesis model is then orthogonally transformed so that it fits the bone model. The views obtained are clinically very relevant since they indicate where the teeth of a later fixed prosthesis will come, and the planner can orient the axes of the implants towards the occlusal plane of the teeth. This double scanning procedure is a low-cost technique that nevertheless has significant clinical benefits.