Complications in orthognathic surgery related to both T.M. Joint and dental occlusion could be arrested by going through the several complications which individually occurs in these two important functional areas of the gnathic system but that goes beyond a presentation such as this. So, the aim of this paper will be to review those complications in which both of these structures are responsible together in building or explaining the bad result that the treatment team need to face.

The main complication we face is skeletal/dental instability, which need to be clearly separated from skeletal/dental relapse. Instability could be seen both in the short and/or in a long term follow up and are related to either a postural or and structural mandibular condyle problem. Occlusal instability related to a mandibular condyle position usually appears right during surgery or in the immediate post operative period. Structural changes in the condylar head will be seen in the medial or long post operative follow up and usually related to a known or to a new structural condylar problem which causes condylar size and/or volume progressive changes either due to a resorption with lost of skeletal posterior vertical support or to an enlarged condylar head which continuously push the mandible toward the opposite side causing occlusal instability due to a condylar hyperplasia. This paper will briefly review these postural and structural condylar changes which end in skeletal/occlusal instability and will show the author’s algorithms to deal with these problems.