Methods: Thirty patients (25 females, 5 males; mean age, 22.66 ± 3.27 years) who presented with moderate crowding of the upper labial segment and underwent extraction-based fixed appliance treatment were recruited. They were randomly allocated to receive adjunctive therapy with MOPs (n = 15) or treatment with fixed appliances only (control group; n = 15). EARR was measured from long-cone periapical radiographs taken at the start and the sixth month of treatment. A correction factor for the enlargement difference was used to calculate EARR. Data were analyzed with descriptive statistics and repeated-measures analysis of variance.

Results: The mean root lengths of 168 teeth were measured and showed no statistically significant difference (p > 0.05) after six months of fixed appliance treatment in the MOP (mean difference [MD] = 0.13 mm; 95% confidence interval [CI] = -0.10-0.35) and control group (MD = 0.14 mm; 95% CI = -0.10-0.37). Most of the roots in the MOP and control groups (42.86% and 52.38%, respectively) showed only mild resorption. Less than 8% of the roots in both groups (7.14% in the MOP group and 4.76% in the control group) showed moderate resorption.

METHODS: Thirty adult participants (25 females and 5 males; mean age, 22.66 ± 3.27 years) with moderate upper labial segment crowding were randomly assigned into intervention and control groups using block randomization. All participants had first premolar extractions, bonded conventional fixed appliances, and 0.014-in, followed by 0.018-in nickel-titanium archwire placement for initial alignment. The intervention group received a 3-mm deep MOPs procedure under local anesthesia using a Propel device (Propel Ortho Singapore, Pte, Ltd, Winstedt Rd, Singapore) on the labial attached gingivae of maxillary incisors at monthly visits until complete alignment. Little's irregularity index was used to assess the overall changes and measure the change of tooth alignment of the 6 maxillary anterior teeth. Assessor blinding was employed.

RESULTS: There was no statistically significant difference in the median overall alignment duration between MOPs and control groups (139 days [95% confidence interval, 115.32-161.83] vs 143 days [95% confidence interval, 107.12-179.74]; hazard ratio, 0.829; P = 0.467). The MOPs procedure had no significant effect on the alignment duration (P = 0.657) and no overall significant difference in alignment improvement percentage among 2 groups on the basis of time (F = 2.53; P = 0.124). No harm was encountered.

CONCLUSIONS: The application of MOPs is no more effective in accelerating initial orthodontic alignment than conventional treatment.

TRIAL REGISTRATION: This trial was registered at the ISRCTN registry with the study ID ISRCTN15080404.

PROTOCOL: https://doi.org/10.1186/ISRCTN15080404.