Abstract

Growth Modifications Using a Bone-Anchored Herbst Appliance

by De Clerck Hugo

The forward projection of the chin is primarily achieved through the lengthening of the mandible. Although horizontal displacement of the glenoid fossa also contributes to chin displacement, its impact is relatively limited. Mandibular rotation, however, is a highly effective tool for increasing (anterior rotation) or decreasing (posterior rotation) chin projection. A prospective clinical trial was initiated to study growth modification using a Herbst appliance, which is bone-anchored in the mandible and tooth-supported in the upper jaw. The active treatment period was 10 months. A CBCT scan was taken at the start of the treatment and another two months after the removal of the Herbst appliance. Surface models were registered on the anterior cranial base and on the symphysis. More than 150 cases, with varying vertical growth patterns, involving patients aged between 12 and 20 years old, have been included. The use of direct skeletal anchorage with two patient-specific miniplates in the mandible not only eliminates all proclination of the lower incisors but results in retroclination. Additionally, it provides greater propulsion of the mandible over a longer period compared to conventional Herbst treatment. This leads to forward chin projections ranging from 4 to 8 mm within one year.

Learning Objectives

After this lecture, you will be able to analyze the difference between traditional Herbst and hybrid Herbst (tooth support in the maxilla and miniplate anchorage in the mandible) from a biomechanical standpoint.
After this lecture, you will be able to understand details on special design, patient-specific manufacturing, and the surgical insertion of bone anchorage required to withstand the significant forces exerted by the Herbst connectors.
After this lecture, you will be able to evaluate the differences in outcome between conventional Herbst and bone-anchored Herbst treatments: is the investment worthwhile?