Aim: A clinical trial to assess he effects of fifteen months therapy with Twin Block (TB) and Dynamax (Dx) appliances.
Objectives: To compare the hard and soft tissues effects of treatment and immediatly post treatment using cephalograms and 3d surface laser scanning.
Design: A Randomised Clinical Trial
Method and Materials: One hundred and fifty subjects with Class II division I malocclusion aged 10-14. Data from an untreated control group over one year was available for forty patients aged 10-14. Cephalometric records were taken strictly on the day the appliances were fitted and withdrawn and 3 months later.
Statistical analysis using analysis of covariance.
Results: One hundred and twenty-nine subjects were available for analysis. The TB was found to produce more antero-posterior change in the soft tissue pogonion than the Dx (TB m = 5.7mm, Dx m = 1.7mm; p=0.00), with significant changes also in the lower sulcus (TB m = 5.6mm, Dx m = 2.3mm; p=0.00). 3d scans found mandibular length increases TB m = 9.6mm, compared with Dx m = 7.0mm (p = 0.5).
Skeletally, anterior facial height changes were significant (TB m = Dx m = p=0.02). The hard tissue cephalometric changes were mainly in mandibular length (TB m = 7.0mm, Dx m = 3.7mm; p=0.02)..
Conclusions: Full time appliance wear for fifteen months is associated with increased dimensional changes with the TB, compared to the Dx. The changes are clinically significant particularly in the vertical. Lateral cephalometry underestimates the soft tissue changes compared with laser scanning.