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Angle Orthod. 2012 Jan;82(1):96-101. doi: 10.2319/032011-197.1. Epub 2011 Aug 1.

A comparison of two different techniques for early correction of Class III malocclusion.

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Orthodontics, Guy's and St Thomas NHS Foundation Trust, London, UK.



To compare the effectiveness of Reverse Twin-Block therapy (RTB) and protraction face mask treatment (PFM) with respect to an untreated control in the correction of developing Class III malocclusion.


A retrospective comparative study of subjects treated cases with either PFM (n  =  9) or RTB (n  =  13) and untreated matched controls (n  =  10) was performed. Both the PFM and control group samples were derived from a previously conducted clinical trial, and the RTB group was formed of consecutively treated cases. The main outcome variables assessed were skeletal and dental changes. Lateral cephalograms were taken at the start and end of treatment or during the observation period. Analysis of variance was used to compare changes in cephalometric variables arising during the study period in the lateral group. Linear regression analysis and an unpaired t-test were used to determine the impacts of treatment duration and gender, respectively.


Significantly greater skeletal changes arose with PFM therapy than with RTB therapy or in the control group (SNA, SNB, and ANB; P < .001). The dentoalveolar effects of RTB therapy exceeded those of PFM treatment, with significantly more maxillary incisor proclination (P < .001) and mandibular incisor retroclination (P < .006) arising with treatment.


Both appliances are capable of correction of Class III dental relationships; however, the relative skeletal and dental contributions differ. Skeletal effects, chiefly anterior maxillary translation, predominated with PFM therapy. The RTB appliance induced Class III correction, primarily as a result of dentoalveolar effects.

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