The Orthodontics Professors
the latest in contemporary & evidence-based orthodontics
BY TATE H. JACKSON & LORNE KOROLUK
Data on the long-term stability of orthodontic treatment is often very difficult to obtain, but a group from Germany has managed to recall 20 Class II, Division 2 adolescent patients – all of whom completed treatment with the Herbst appliance more than 15 years earlier. The patients were selected based on pre-treatment characteristics and treatment protocol, not on treatment outcome.
In this retrospective study, the average age of the patients at the start of treatment was 14.4 years. All patients were nearly full cusp Class II at the molar, had at least two retroclined maxillary incisors (Div.2), and had a deep bite (average OB 5.3mm).
14 of the 20 patients were decompensated (incisors were proclined to allow advancement of the mandible) for an average of 8.6 months before Herbst delivery.
All patients were then treated non-extraction with a Herbst appliance + bonded brackets. The Herbst was advanced to an edge to edge incisor relationship and remained in place for 7.7 +/- 1.7 months. After removal, full fixed appliance therapy continued for a total of 24.9 +/- 6.9 months of overall treatment. Multiple bracket types were used.
At recall, the average patient age was 33.9 +/- 2.7 years. 11 of the 20 patients had no retainers at recall; of the other 9 patients: 8 had a bonded mandibular canine to canine retainer and 1 had a bonded maxillary retainer only.
Results were compared to a historic Class I growth study cohort who had no treatment.
At the end of treatment and at long-term recall, all Class II, Div. 2 patients had a Class I molar relationship with 2mm OJ. The bite deepened from the end of treatment to recall by 1mm.
Compared to the untreated control group, the Class II, Div. 2 patients had less OJ and a lower PAR score at long-term recall, but were otherwise statistically no different.
WHAT THE PROFESSORS THINK
This study falls victim to the same issues as any retrospective study in terms of heterogeneity of the patient pool and treatment, as well as the use of a historic growth study Class I control group – rather than a randomized design.
Importantly, no cephalograms were available at recall, and examiners were not blinded as to whether the casts they examined were from the end of treatment or long-term recall.
Nonetheless, for the practicing orthodontist who is concerned about the stability of the occlusal correction obtained with a Herbst, this study provides one more piece of evidence, based on a relatively-standardized treatment protocol.
The patient population is of particular interest in terms of stability because all of these patients had:
Additionally, more than half of the patients had no retainers at recall. So, the results in terms of stability might better reflect “real life” conditions where patients lose retainers over time.
Based on these data, the anterior-posterior correction to Class I was maintained long-term to an acceptable level, as was the overbite and overjet correction.
What’s the bottom line for a clinical orthodontist?
In growing patients with a Class II, Division 2 malocclusion for whom correction to dental Class I is a major priority, Herbst plus fixed appliance treatment can be quite stable into adulthood, even without long-term retention.
This study does not suggest that retention is not needed - nor does it dive into the details of incisor alignment and relapse.
But for those of us who fear a higher risk of anterior-posterior relapse with Herbst treatment because of incisor proclination or posturing of the mandible, this study suggests that might not always be the case in the long-term, at least when it comes to Angle Classification and OJ.
Article Reviewed: Bock NC, et al. Outcome quality and long-term (≥15 years) stability after Class II:2 Herbst-multibracket appliance treatment in comparison to untreated Class I controls. Eur J Orthod. Online early December 2017.