Post-treatment effects of the Herbst appliance. A radiographic, clinical and biometric investigation.

The treatment effects of continuous bite jumping with the Herbst appliance in the correction of Class II malocclusions have been analysed in previous investigations. The purpose of this study was to investigate the post-treatment effects of the appliance as well as to compare various mandibular anchorage systems. The total patient sample consisted of 108 malocclusion cases treated with the Herbst appliance. The subjects in the various parts of this study were selected from the total sample according to different criteria. The study included analyses of lateral cephalometric radiographs in centric occlusion and with the mouth wide open, lateral tomograms of the temporomandibular joints, growth records and dental casts. A clinical examination of the patients and a questionnaire at the time of follow-up was also included. During Herbst appliance therapy, all subjects were treated to a Class I or overcorrected Class I relationship. During the post-treatment period of 12 months, the occlusion settled into Class I, mainly as a result of relapsing (recovering) maxillary and mandibular tooth movements. Ninety per cent of the dental changes occurred during the first 6 months post treatment. The anterior movement (proclination) of the mandibular teeth during treatment could not be prevented even if the anchorage system was increased by incorporating more dental units. In the long-term perspective (5-10 years after treatment), it was found that Herbst treatment improved the sagittal jaw base relationship but without normalising it. The sagittal dental arch relationship, on the other hand, was almost normalised. The growth period in which the subjects were treated did not seem to have any impact on the long-term result. Furthermore, Herbst appliance therapy did not seem to have any long-term adverse effects on the craniomandibular system.