Treatment changes of hypo- and hyperdivergent Class II Herbst patients

Abstract

Objectives: To determine the relative effects of Herbst appliance therapy in hypo-and hyperdivergent patients. Materials and Methods: The treated group included 45 growing Class II, division 1, patients treated with stainless steel crown Herbst appliances, followed by fixed edgewise appliances. The untreated control group consisted of 45 Class II, division 1, subjects, matched to the treated sample based on Angle classification, age, sex, and pretreatment mandibular plane angle (MPA). Subjects were categorized as hypo-or hyperdivergent based on their MPAs. Pre-and posttreatment cephalograms were traced and superimposed on cranial base and mandibular structures. Results: The primary effect of the Herbst in terms of maxillomandibular correction was in the maxilla. It significantly restricted maxillary growth, producing a ''headgear effect.'' Mandibular treatment changes depended on divergence. Hyperdivergent patients experienced a deleterious backward true mandibular rotation with Herbst treatment. Hypodivergent patients, as well as untreated hypo-and hyperdivergent controls, underwent forward true mandibular rotation. However, hypodivergent chins did not advance any more than expected for untreated hypodivergent Class II patients. Conclusions: Hypo-and hyperdivergent patients benefit from the Herbst's headgear effect. While the mandibular growth of hypodivergent patients overcomes the negative rotational effects, hyperdivergent patients undergo a deleterious backward mandibular rotation and increases in facial height.

Influence of Vertical Facial Growth Pattern on Herbst Appliance Effects in Prepubertal Patients: A Retrospective Controlled Study

“…In fact, these authors observed that hypo-and hyperdivergent patients benefit from Herbst's headgear effect in the upper maxilla, while hyperdivergent patients exhibited a deleterious backward mandibular rotation. A possible explanation could be that cantilever Herbst appliance with full-coverage stainless steel crowns on the upper and lower first molars was used by Rogers et al [28], while in the present study, a total acrylic splint extending from the first lower molar to the first contralateral molar was used to reinforce the anchorage. Furthermore, another possible explanation for the rotational differences between subjects with different vertical growth patterns could be the orofacial musculature function as patients with weak jaw musculature could exhibit a backward mandibular rotation.…”

“…In a previous study, a significant difference of cranial base-mandibular angle was found between hypodivergent, normodivergent, and hyperdivergent patients [28], and the results showed that hypodivergent subjects tend to decrease this angle, while hyperdivergents tend to increase it. In fact, these authors observed that hypo-and hyperdivergent patients benefit from Herbst's headgear effect in the upper maxilla, while hyperdivergent patients exhibited a deleterious backward mandibular rotation.…”

“…In literature, a significant alteration was found in mandibular divergence at the end of the Herbst treatment in a limited number of studies [25][26][27], while other previous studies showed a significant change of SN/GoMe at the end of orthodontic therapy [28].…”

Ist die kieferorthopädische Korrektur einer wachsenden hyperdivergenten retrognathen Klasse II möglich?

“…Unbehandelt zeigen hyper-und hypodivergente Klasse-II-Patienten völlig unterschiedliche Wachstumsmuster [36]. Im Vergleich mit hypodivergenten Patienten, deren SNA-und SNB-Winkel im Lauf der Zeit immer größer werden, verkleinern sich die Winkel bei hyperdivergenten Individuen.…”

“…Studien, in denen unbehandelte Individuen mit Klasse I und Klasse II statistisch miteinander verglichen wurden, konnten eindeutig nachweisen, dass die Klasse II in erster Linie ein sagittales Unterkieferproblem ist [12]. Dabei [25,36]. Das Kinn bewegt sich hier weniger weit nach vorne und nach unten, weil der Unterkiefer eine echte Rotationsbewegung nach hinten ausführt, während er bei unbehandelten Fällen nach vorne rotiert.…”