[Cervical headgear with angled outer arms. A biomechanically comprehensible system?].

When applying the angulated face bow, it doesn't seem possible to avoid vertical and transversal forces which occur in addition to the distalization force as moments. By varying the length and angulation of the outer bow, it is possible to influence the force components and the moments in the sagittal plane. In the clinical analysis of the force system it is assumed that the face bow is an ideal rigid system. Only under this presupposition is the assumption valid, that the product of the force and the perpendicular distance to the molar tube is responsible for the size of the moment. Under this assumption, however, all forces and moments created by the deflection of the headgear are not taken into consideration. An experimental analysis of the forces and turning moments which occur indicates that this simplifying geometric point of view does not always correspond to reality. It was evident, e.g., that there is no linear correlation between the force and moment in mesio-distal direction due to the deflection of the outer bow. This effect becomes the more obvious the longer the outer bow of the headgear is.