Comparison of the effects of Twin Block and activator treatment on the soft tissue profi le

Aesthetic improvement is highly valued by patients seeking orthodontic treatment ( Dann et al. , 1995 ). Subjects with a Class II malocclusion are a good example of patients who are referred to orthodontists primarily for aesthetic improvement ( Dann et al. , 1995 ). In growing patients, two-phase treatment of Class II skeletal malocclusions, which includes growth modifi cation with functional appliances followed by orthodontic treatment with fi xed appliances, has been advocated as an appropriate treatment approach ( Keeling et al. , 1998 ; Tulloch et al. , 2004 ). As with all orthodontic treatment modalities, the primary goals of growth modifi cation are both to correct the skeletal discrepancy and to achieve optimal facial aesthetics. One of the most widely used functional appliances for orthopaedic correction of Class II skeletal malocclusions is the activator, which was introduced by Andresen in 1935 ( Graber, 2005 ). The skeletal and dentoalveolar effects of activators have been well documented ( Harvold and Vargervik, 1971 ; Calvert, 1982 ; Pancherz, 1984 ; Vargervik and Harvold, 1985 ; Lux et al. , 2001 ; Ba ş çiftçi et al. , 2003 ). Another popular functional appliance is the Twin Block (TB). Due to its simple design and ease of use, the TB can be worn 24 hours a day and takes full advantage of all the functional forces applied to the dentition, including those of mastication. Another advantage of the TB is that it can be used with fi xed appliances ( Clark, 1982 , 2002 ). Comparison of the effects of Twin Block and activator treatment