**4.2 Planning and preparation of the TMJ prosthesis**

As mentioned above, patient-fitted prostheses are always used for orthognathic surgery with TJR. These are prepared and produced in the following manner [15]:



After all steps have been approved, production of the prosthesis commences. The entire process of creating a prosthesis takes several weeks to months. Note 1: when planning mandibular advancement, it is important to realize the differences between sagittal osteotomy advancement and total replacement advancement. During sagittal osteotomy, the position of the distal fragment (part of the branch of the mandible with the muscular and articular process) remains in the same place. In contrast, in mandibular advancement with total joint replacement, the branch is completely shifted anteriorly. This shift can cause the coronoid process to come into contact with the posterior wall of the maxila (**Figure 4**), which will in turn result in reduced jaw mobility. This is resolved through a planned coronoidectomy.
