Effects of Micro-osteoperforation Using a Lance Drill on the Rate of Tooth Movement During Lower Arch En-Masse Retraction in Class I Malocclusion With Bidental Proclination: A Comparative Study

Background and objectiveThe extended duration of fixed orthodontic treatment carries well-recognized risks, and microosteoperforation (MOP) has been proposed as a minimally invasive approach to accelerating orthodontic tooth movement.This study aimed to compare the rate of lower arch anterior en-masse retraction, assessed using three-dimensional (3D) digital models, between patients who received MOPs performed with a lance drill attached to a physiodispenser unit and those who underwent conventional retraction without MOP.The study also assessed associated pain and discomfort. Materials and methodsTwenty patients aged 12-18 years with Class I malocclusion and bidental proclination who were undergoing fixed appliance therapy involving extraction of the maxillary and mandibular first premolars and lower arch anterior en-masse retraction were enrolled in this prospective, two-group comparative observational study.Patients who underwent MOP as part of their retraction protocol formed the MOP group, whereas those treated with conventional retraction alone formed the comparison group.Group assignment was not randomized.During mini-implant-assisted en-masse retraction, patients in the MOP group received three MOPs in a linear distribution distal to the canine on each side using a lance drill attached to a physiodispenser unit.The procedure was repeated at each 28-day visit over three months.En-masse retraction was performed using nickel-titanium closed-coil springs delivering 150 g of force.The rate of enmasse retraction was measured using 3D digital models at the three-month follow-up, with the outcome assessor blinded to group allocation.Pain and discomfort were recorded using a 100-mm visual analogue scale (VAS) at 24 hours and 7, 14, and 28 days after each MOP procedure. ResultsSeven participants in the MOP group and nine in the comparison group completed follow-up.The mean rates of en-masse retraction were 1.38 ± 0.35 mm on the right and 1.31 ± 0.30 mm on the left in the comparison group, compared with 2.73 ± 0.91 mm on the right and 2.60 ± 0.64 mm on the left in the MOP group.After three months, the rate of en-masse retraction was significantly higher in the MOP group than in the comparison group (Mann-Whitney U test, p < 0.05 for both sides).Pain sensitivity was highest at 24 hours after the procedure and differed significantly across time points (Friedman's ANOVA, p ≤ 0.003).Following Bonferroni correction, pain at 24 hours was significantly higher than at 14 and 28 days during the first month only (Dunn's post hoc test, p < 0.05). ConclusionsPhysiodispenser-assisted MOP using a lance drill was associated with a significantly higher rate of lower arch en-masse retraction and transient pain that peaked at 24 hours after the procedure.These findings should be interpreted in light of the nonrandomized study design, single-center setting, small sample size, three-month follow-up period, and loss to follow-up associated with the COVID-19 pandemic, which may limit the generalizability and strength of the conclusions.Further multicenter studies involving larger samples and longer follow-up periods are needed to confirm these findings.