Researchers from the University of Alberta, Edmonton, found that low-intensity pulsed ultrasound (LIPUS) minimized orthodontically induced tooth root resorption when applied during torque tooth movement over a 4-week period.

The study, published in The Angle Orthodontist, looked at 10 healthy patients, aged 12 to 35, who required extraction of all first premolars as part of their routine orthodontic treatment. A 15-degree twist was applied in the archwire using 0.019 x 0.025-inch TMA in a 0.022-inch bracket system that produced a buccal root torque of approximately 5 N/mm at the bracket level. The researchers used a split mouth design, randomization, and blinding, where 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 transducer’s surface area. The other side served as a 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.

According to the researchers, 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.