[Position of the upper incisor after orthodontic therapy with Tweed philosophy and mechanics: statistical study of average incisal variations in 3 Angle dento-skeletal classes, with and without extraction].

The skeletal characteristics of dento-alveolar malocclusions condition the orthodontic therapy plane and produce typical and recurrent variables in the final shape in "Tweed occlusion". The study effects with templates made out of cephalometric average values of treatment in the different dental malocclusions, shows direction and amount of therapeutics correction. The behaviour of upper and lower incisors to achieve the normal occlusion is in relation with the characteristics of Angle's Class and with the necessity of therapeutics dental extractions.