LONG-TERM EFFECT OF TREATMENT WITH THE HEADGEAR-HERBST APPLIANCE IN THE EARLY MIXED DENTITION - STABILITY OR RELAPSE

In this investigation of the long-term effect of mandibular protrusive function in children with severe Class II malocclusions, a group of c hildren age 8 years 8 months were initially treated for 5 months with a headgear-Herbst appliance followed by a 3- to 5-year period of activ ator retention. The patients were studied out of retention at the mean age of 17 years 4 months and compared with an untreated control group . Part of the sagittal correction relapsed. As compared with the contr ol group, the average 3.9 mm protrusive effect of treatment on the man dible decreased to a nonsignificant 1.5 mm out of retention. The signi ficant 2.0 mm therapeutic increase of the condylion-gnathion distance decreased to 1.3 mm and was not significantly different from control v alues at age 17 years 4 months. However, the 1.5 mm posterior effect o f treatment on the maxilla continued to increase during activator rete ntion and the difference compared with the control group was 2.3 mm po stretention. This effect on the maxilla partly compensated the relapse tendency observed in the mandible so that 3.8 mm of the 5.4 mm posttr eatment sagittal improvement still remained out of retention. Because of the sample size and individual variability, the results should be i nterpreted cautiously, but the findings indicate that maxillary sutura l remodeling might be more receptive long-term to orthopedic treatment than the mandibular condylar growth process.