A controlled cephalometric evaluation of single-arch cervical traction therapy.

E xtensive use of cervical traction in recent years has caused controversy among orthodontists concerning its effect on the craniofacial skeleton of a growing child, This has led to several cephalometric studies. It generally has been established that the normal forward growth of the maxilla can be inhibited by the judicious use of extraoral traction. 4s *, I12 13, I53 I9 Reductions in the XNA angle show that growth of the apical base was retarded or actually moved distally.2y 3, 8s gl 111 I47 I53 I9 A downward tipping of the anterior palate is another result of cervical therapy.3l gv I49 I52 I9 The occlusal plane remained stable in three cervical traction studie& *, g but tipped downward anteriorly in studies made by others analyzing the effects of this type of extraoral attachment.14s I5 Tipping of the occlusal plane is thought to be due to an extrusion of the maxillary incisors and a distal tipping of the maxillary mo1ars.7, I6 Several investigators report distal tipping of the maxillary first molar with cervical traction.*1 4l Q, 12% I41 I9 A study of the maxillary first molar by Klein9 showed that the molar can extrude as a result of growth, cervical treatment, or both. Schudy” described the effects of excessive extrusion of the maxillary molars to be a clockwise rotation of the mandible with a reduction in the SNB angle and increases in the FMA angle and anterior facial dimension. Other investigations of cervical traction indicated a significant extrusion of the maxillary first molar with a simultaneous lack of anterior pogonial movement.8’ lgB1ueher3 and Sandusky,15 analyzing the use of cervical appliances to treat Class II, Division 1 malocclusion, demonstrated no significant change in point B during treatment. To understand the effects of the cervical face-bow on the dentofacial skeleton of the growing child, it is necessary to examine the forces applied by the device. In addition to the major distal component of force, other force vectors are present which may tip and extrude the maxillary first molar. Thurowl* stated that the center of rotation of a tooth lies within the area of the root. When an applied force passes through the rotational point of the tooth, it moves bodily; when the force passes above or below the rotational point, the tooth tips. Gould6