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The short- and long-term effects of the Herbst appliance on the facial profile were determined in 69 Class II, division 1 malocclusions treated for 7 months and followed for 5-10 years post-treatment. Forty-nine subjects exhibited a stable long-term treatment result, while 20 cases relapsed. Lateral cephalometric radiographs from before treatment, after treatment, 6 months post-treatment, and 5-10 years post-treatment were analysed. As a rule Herbst treatment resulted in a reduction of the facial hard and soft tissue profile convexity. In relation to the E-line, the upper lip became retrusive, while the lower lip remained, on average, unchanged. During the post-treatment period of 5-10 years the hard tissue profile convexity was, on average, reduced in both the stable and relapse groups. When excluding the nose in the soft tissue profile evaluation, the facial profile convexity was, on average, reduced in the stable group while it remained unchanged in the relapse group. When including the nose in the evaluation, an average increase in the profile convexity occurred in both examination groups. Furthermore, the upper and lower lips became retrusive in both groups. For all the variables, however, large individual variations existed. In conclusion, it can be said that the Herbst appliance improves the facial hard and soft tissue profiles. Due to post-treatment growth changes the long-term effects of therapy are, however, variable and unpredictable.

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The aim of this study was to analyse the influence of activator treatment on chewing efficiency. The subject material consisted of 60 children, adolescents and adults: Twelve children (ten years of age) with a Class II, Division 1 malocclusion were treated successfully with activators to a normal occlusion (16 years of age). Three normal occlusion samples, ten years (n = 12), 16 years (n = 12) and 29 years (n = 12) of age as well as an untreated Class II sample (n = 12), 16 years of age, served as control groups to the activator patients. The chewing ability was evaluated with the aid of a chewing efficiency test. The dental occlusion was appraised on dental casts. Recordings were made of number of erupted teeth, number of intermaxillary occlusal tooth contacts, overjet and overbite. The results revealed that chewing efficiency in activator patients was doubled from ten to 16 years of age. When comparing untreated subjects 16 years and ten years of age a greater chewing efficiency was seen in the older subjects. This was true for both Class II malocclusion and normal occlusion cases. Furthermore, in 16 year old subjects the chewing efficiency was comparable in treated and untreated normal occlusions as well as untreated Class II malocclusions. Thus, the investigation did not ascertain whether activator treatment per se resulted in an improved chewing efficiency. Furthermore, in the activator group no direct association existed between improvement in chewing efficiency and increased number of erupted teeth on one hand and increased number of intermaxillary occlusal tooth contacts, reduced overjet and overbite on the other. It is suggested that chewing efficiency is partly age related. The sagittal intermaxillary dental arch relationship doesn't seem to play an important role in determining chewing ability. However, harmonious interplay between the occluding teeth and the muscles influencing them (the muscles of mastication, the tongue-, lip- and cheek-musculature) is certainly of importance.