The Orthodontics Professors
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Can we increase mandibular growth in Class II patients with a Forsus appliance and skeletal anchorage?
BY TUNG T. NGUYEN
This study, published in the May 2015 issue of the Angle Orthodontist, evaluated 17 Class II children treated with a Forsus Fatigue Resistance Device (FRD) connected to mandibular symphysis miniplates. The sample consisted of 11 girls and 6 boys with a mean age of 11.96 years. The study was divided into 2 phases of equal length: an initial alignment phase and a FRD + miniplate phase. Cephalometric films were superimposed at three time points: before treatment, after the alignment phase, and after the FRD + miniplate phase.
The success rate for the miniplates was 91.5%. The authors reported a mean overjet correction of 5.11mm, with 74% of the correction from skeletal changes (1.16mm from maxillary restraint and 2.62mm from mandibular A-P growth). They did note an increased in retroclination of the maxillary incisors (8.9°).
WHAT THE PROFESSOR THINKS
The search for an appliance to grow the mandible is nothing new in our profession, but the use of skeletal anchorage provides a unique twist to this study. To compensate for the lack of a control group, the authors split the study into leveling stage and a FRD + miniplate phase, and their statistics showed that the skeletal changes from the FRD + miniplate was significantly greater than the leveling phase. That said, numerous growth studies have shown that the mandible does not grow at the constant rate, but in fact exhibits an increase in growth velocity during puberty.
This is one of the biggest confounders to this study. How can the authors be sure that growth during the FRD + miniplate phase was solely the result of the appliance rather than a natural peak in pubertal growth coinciding with this phase of treatment? Upon examination of the data, one can also see that the FRD + miniplate phase showed two-three times more growth of the vertical dimension (N-Me and S-Go) compared to the leveling phase, suggesting the FRD + miniplate phase might coincide with peak pubertal/ mandibular growth. As a side note, this professor believes that any study examining mandible growth as a result of a treatment method must always include a well-matched control group.
Interestingly, a previous study using Forsus FRD and miniscrews found no skeletal change for the mandible.(1) Furthermore, a recent systematic review evaluating the impact of skeletal anchorage with fixed functional appliances found no significant skeletal increase, but did note a decrease in mandible incisor proclination.(2)
Article Reviewed: Unal T, Celikoglu M, Candirli C. Evaluation of the effects of skeletal anchoraged Forsus FRD using miniplates inserted on mandibular symphysis: A new approach for the treatment of Class II malocclusion. Angle Orthod. 2015; 85:413–419.
Tate H. Jackson, DDS, MS