Nature of relapse after surgical mandibular advancement

Pre-operative, post-operative and follow-up cephalometric records of 16 cases of mandibular retrognathia treated by surgical mandibular advancement were analysed retrospectively. The results showed good mean stability in the mandibular advancement with variable individual relapse. The pre-operative mandibular plane angle, magnitude of the advancement and post-operative increase in the posterior lower face height were the variables chiefly related to relapse. There appeared to be limited control over the posterior segment which was liable to distraction and rotation. The follow-up changes were time linked. Both mechanical and biological factors are postulated to explain the relapse.