PubMed · 3482089
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R P Howe. 1987. Removable plastic Herbst retainer.. https://pubmed.ncbi.nlm.nih.gov/3482089/
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A bimaxillary device is effective only if the therapeutic position of the mandible is maintained for as long a period as possible by day and night, i.e. the lower jaw cannot "drop" from the construction bite position. One simple means of preventing the mandible from dropping out of the bimaxillary appliance during sleep and thus of ensuring adaptation of the muscles and of the joint structures during the night without impairing active adaptation during daytime functions (speaking, swallowing) is being used at Wuerzburg University Department of Orthodontics: In connection with anterior traction, which anchors the bimaxillary appliance to the maxilla, attachments are fixed to the mandibular canines or first premolars, so that the mandible is kept in the therapeutic position during the night by means of elastics. Besides the description of this method, the results of a clinical study on its effectiveness are presented in this paper. In the experimental group (20 Class II/1 patients) treated with the combination of bionator with anterior extraoral traction and up-and-down elastics, the increase of the SNB angle and accordingly of the ANB angle was twice as great as in a control group treated only with bionator and extraoral traction without additional securing of the mandible.
The aim of this study was to examine the skeletal changes produced by Class III activator during the treatment of patients with skeletal Class III malocclusions and to characterize the stability of these changes in the years after treatment. The samples consisted of 19 girls and 9 boys. Their mean age was 9.6 +/- 1.4 years at the beginning of the treatment. The average treatment time was 1 +/- 0.5 years. Measurements were obtained from cephalometric head films taken before treatment, at the end of treatment, and 6.6 +/- 2.1 years after the end of activator treatment. During the treatment, the Class III activator produced a statistically significant increase in the ANB angle, and this change remained through the postactivator period. The gonial angle exhibited a compensatory decline during the postactivator period. The skeletal profile was improved with treatment and was not lost during the posttreatment period despite significant increase in maxillomandibular differential. This study indicates that Class III activator may be a viable mode for the initial stage of skeletal Class III treatment, in conjunction with the period of postfunctional fixed or removable appliance therapy to improve the occlusion.
The mode of action of the activator appliance is still unclear. Apart from a possible mandibular growth enhancing effect, some investigators believe that orthopedic forces may be applied to the maxilla, contributing to Class II correction by inhibition of maxillary growth. In addition, orthodontic forces may arise that produce dentoalveolar changes. The purpose of this study was to measure the magnitude of anteroposterior intermaxillary forces during wear of the activator appliance. Ten consecutive patients with Class II dental and skeletal relationships were treated with a modified activator appliance. The appliance had maxillary and mandibular segments that could be detached from each other during the measuring session. A force transducer was placed at the anterior part of the maxillary segment, and the anteroposterior force exerted by the mandibular segment was measured. Measurements were taken in the upright and reclined position at every patient visit for a period of 6 months. Results indicated that intermaxillary forces were generally in the orthodontic range (median values of 100 gf at the upright position and 123 gf at the reclined position). A wide variation in force levels was noted, both between patients and for the same patient during the experimental period. No statistically significant change in force levels was observed during the 6 month period and no difference was noted between upright and reclined posture.