Thirty-two-year follow-up study of Herbst therapy

In the article of Dr Pancherz et al (Pancherz H, Bjerklin K, Lindskog-Stokland B, Hansen K. Thirty-two-year follow-up study of Herbst therapy: a biometric dental cast analysis. Am J Orthod Dentofacial Orthop 2014;145:15-27), the authors analyzed the long-term effects of Herbst treatment on tooth position and occlusion in 14 patients treated in 1977 and 1978. The description of the results is already per se an extraordinary accomplishment. Recruiting 14 patients from an original sample of 22 patients, 32 years after treatment, is worth highlighting in the scientific community. However, a specific fact attracted our attention and motivated us to express our opinion: 3 patients in the sample had been treated with fixed appliances before the posttreatment evaluation, and 2 of them had 4 premolars extracted. At first, this might seem a rather small number, but it represents 21% of the sample and may exert a significant influence on the results.

According to the authors, “multibracket treatment after the Herbst phase was not aimed to change the occlusion but only to align the teeth.” Nevertheless, we believe that tooth alignment is 1 characteristic of normal occlusion. The definition of normal occlusion by Strang, for instance, includes the description of correct interproximal contact points between the teeth: ie, correct alignment of the teeth.

As mentioned by the authors, at the end of Herbst therapy, “the sagittal lateral occlusion and overjet are overcorrected, and the vertical lateral occlusion has an open-bite tendency, with the incisors in an edge-to-edge position. During the first year after treatment … the occlusion generally settles into a Class I relationship.” By using fixed appliances, though, we believe that such characteristics were lost because the teeth were moved into more favorable positions by the orthodontic mechanics, particularly in the 2 extraction patients, in whom extensive tooth movements were required.

Closing the extraction spaces might have also influenced the arch perimeter changes between the pretreatment and posttreatment evaluations, particularly in relation to patient 8X, who had reductions of about 19 mm in the maxilla and 13 mm in the mandible, according to the data shown in the study.

In patient 8X, the extreme values of overjet and overbite before treatment probably motivated the extraction of 4 premolars, which required extensive tooth movements and contributed to the increase of the mean of these variables of treatment changes (T1-T2), compromising, once again, the behavior of the sample.

Finally, the irregularity index showed an average value of 3.0 mm in the posttreatment evaluation. However, by using fixed appliances, this index may be 0 mm, because they permit total control over tooth positioning. According to the data provided in the study, the elimination of the 3 patients treated with fixed appliance would imply an increase of the irregularity index during treatment. Thus, the mean decrease of 0.5 mm between the pretreatment and posttreatment evaluations does not describe the behavior of the anteroinferior teeth during the Herbst therapy.

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Apr 6, 2017 | Posted by in Orthodontics | Comments Off on Thirty-two-year follow-up study of Herbst therapy
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