THE INITIAL EFFECTS OF THE TREATMENT OF CLASS-II, DIVISION-1 MALOCCLUSIONS WITH THE VAN-BEEK ACTIVATOR COMPARED WITH THE EFFECTS OF THE HERREN ACTIVATOR AND AN ACTIVATOR-HEADGEAR COMBINATION

The effects of the van Beek activator in the correction of Class II, d ivision 1 malocclusions were studied in 39 children, aged 9-13 years ( median 11 years), and compared with the effects of treatment with an a ctivator according to Herren and with those of an activator-headgear c ombination. Profile cephalograms were made before treatment and at the attainment of a Class I molar relationship (median observation time 9 months). The median improvement of the overjet was 4.7 mm and of the molar relationship 3.6 mm. This was largely achieved skeletally by an increase in mandibular prognathism while the skeletal effect on the ma xilla was clinically insignificant. The maxillary incisors retroclined and the mandibular incisors proclined moderately. In general, no intr usion of the maxillary incisors was found and the eruption of the mola rs could not be stopped. The effects differed partly between the sexes , with a larger mandibular skeletal and molar reaction in boys, and a larger maxillary molar movement in girls. The larger mandibular reacti on in the boys might have been due to the on average 4.5 months longer treatment time. The skeletal effects of the treatment were si mi tar with all th ree activator types. The control of the incisors was, howe ver, superior with the van Beek activator, especially when compared wi th the Herren activator.