Apical root resorption of upper first molars as related to anchorage system.

Night-time use of extra-oral traction for anchorage may cause jiggling, rotational and extrusional forces. The purpose of the study was to test the hypothesis that headgear forces in an anchorage system may increase the risk of radiographically detectable root resorptions on molar teeth. Twenty-one patients were selected among patients planned for orthodontic treatment, in which there was a need of anchorage in a full-bond appliance during a period of at least 6 months. An experimental group of 11 patients was given reinforcement anchorage in the maxilla with an extra-oral traction (cervical-pull) during night. Ten patients in a control group was given anchorage by a Goshgarian palatal bar, or by Class II-elastics. Periapical radiographs were taken of the upper first molars according to a standardised technique at the start of treatment, and at 3 and 6 months. Recordings included also patient compliance, force evaluation and the measurement of tooth movement. Significant reduction of root length was shown for some roots already after 3 months. However, mean root resorption after 6 months did not exceed 0.6 millimeter in any upper first molar root of the present sample. The degree of root resorption was similar in the experimental and the control groups. The hypothesis of a significant effect on root resorption of upper first molars by night-time use of extra-oral traction for a 6 month period was rejected. It is concluded that patients given anchorage by night-time use of extra-oral traction will show similar degrees of root resorption of the upper molars as those in which anchorage is given by a Goshgarian bar or Class II elastics.