Effect of continuous versus intermittent orthodontic forces on root resorption: A microcomputed tomography study

ABSTRACT Objectives: To compare the extent of root resorption and the amount of tooth movement between continuous orthodontic force and intermittent orthodontic force that was activated in a similar way to a 4-week orthodontic adjustment period. Materials and Methods: Twenty-five patients who required the extraction of upper first premolars were recruited in this study. A buccally directed continuous force of 150 g was applied to the upper first premolar on one side for 15 weeks. A buccally directed intermittent force (28 days on, 7 days off) of the same magnitude was applied to the contralateral first premolar. The teeth were extracted at the end of the experimental period and processed for volumetric evaluations of resorption craters. The degree of tooth movement and rotation were measured on the study models. Results: Continuous force application displayed significantly higher root resorption volume than the intermittent force application (P < .05), particularly on the buccal and lingual surfaces (P < ...