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° twist was applied in the arch wire using 0.019 × 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/cm2 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 mm3) (P < .001) and percentage of root resorption by a mean difference of (0.33 ± 0.05 mm3) (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.