EFFECTS OF A LINGUAL ARCH AS MAXIMUM ANCHORAGE IN ORTHODONTICS

Abstract

Lingual arches are frequently used in orthodontic extraction treatment, with the intended purpose of achieving maximum anchorage in the mandibular arch; however, little evidence exists in the literature that supports this anchorage approach. The lingual arch is widely supported in the literature for space maintenance and sagittal correction. It has been proven effective at minimizing any decreases in arch depth and perimeter when there is early loss of primary teeth. Theoretically, the lingual arch as a passive maintenance appliance should exert no forces on the teeth, yet studies have shown both the molars and incisors to move. To examine its anchorage efficiency further, we compared incisor and molar position in extraction treatment with and without the use of a lingual arch. Pre and post-treatment cephalograms that included lower premolar extractions were recruited from a depository of images. Canine retraction with power chain or NiTi closing coils with or without the use of a lingual arch for maximum anchorage were compared for incisor and molar position. Angular and millimetric measurements for IMPA, L1-NB, L1-APog and molar mesialization were measured and compared using a t-test. The greatest difference between pre and post-treatment was the IMPA with 5.19° more uprighting of the incisors in the group with no lingual arch, followed by 4.38° more uprighting in the L1-APog measurement. However, none of the differences between the groups were significant: IMPA (p=0.129), L1-NB (angular p=0.161, millimetric p=0.205), L1-APog (angular p=0.197, millimetric p=0.196) and mesialization of the molar (p=0.308). The change in incisor and molar position does not significantly differ with or without the use of a lingual arch in extraction treatment. Clinically, this suggests that the lingual arch does not provide maximum anchorage. Another modality, such as TADs, may provide a better source of anchorage for space closure.