Effect of low-intensity pulsed ultrasound on orthodontically induced root resorption caused by torque: A prospective, double-blind, controlled clinical trial

Objectives: To evaluate the effects of low-intensity pulsed ultrasound (LIPUS) on orthodontically induced tooth root resorption caused by torque in human subjects. Materials and Methods: Ten healthy patients (12-35 years of age) who required extraction of all first premolars as a part of their routine orthodontic treatment were recruited. A 15 degrees twist was applied in the arch wire using 0.019 x 0.025-inch TMA in a 0.022-inch bracket system (Synergy R) that produced a buccal root torque of approximately 5 N/mm at the bracket level. Using a split mouth design, randomization, and blinding, one side of the arch received LIPUS for 20 minutes per day for 4 weeks at an incident intensity of 30 mW/cm(2) of the transducers' surface area. The other side served as a self-control, which received a sham transducer. After 4 weeks, all first premolars were extracted and micro-computed tomographic analysis was performed on these extracted teeth. A linear mixed-model statistical analysis was used. Results: LIPUS-treated teeth showed significantly less total volume of resorption lacunae compared to control teeth by a mean difference of (0.54 +/- 0.09 mm(3)) (P < .001) and percentage of root resorption by a mean difference of (0.33 +/- 0.05 mm(3)) (P < .001). In addition, significantly fewer resorption lacunae were found on all root surfaces in the LIPUS group compared to the control except in the instance of the distal surface. Limitations: This study was performed on limited number of cases during a 4-week period. Conclusions: LIPUS minimizes root resorption when applied during torque tooth movement over a 4-week period.