兽研Review began 10/18/2026 Review ended 10/25/2026 Published 10/29/2026 © Copyright 2026 G S et al. This is an open access article distributed under the terms of the Creative Commons Attribution License CC-BY 4.0., which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. DOI: 10.7759/cureus.118791 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 Neethu G S , Jacob John , Navin Oommen Thomas , Supriya Prabhakaran 1. Department of Orthodontics and Dentofacial Orthopedics, Sri Sankara Dental College - Varkala, Thiruvananthapuram, IND 2. Department of Orthodontics and Dentofacial Orthopedics, Pushpagiri College of Dental Sciences, Thiruvalla, IND 3. Department of Orthodontics and Dentofacial Orthopedics, Pushpagiri College Of Dental Sciences, Thiruvalla, IND 4. Department of Orthodontics and Dentofacial Orthopedics, Radiant Dental Studio, Kottayam, IND Corresponding author: Neethu G S, 2neethugs@gmail.com Abstract Background and objective The 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 methods Twenty 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. Results Seven 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). Conclusions Physiodispenser-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. Categories: Dentistry Keywords: accelerated orthodontics, en-masse retraction, micro-osteoperforation, regional acceleratory 1234 Open Access Original Article How to cite this article G S N, John J, Oommen Thomas N, et al. (October 29, 2026) 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. Cureus 18(10): e118791. DOI 10.7759/cureus.118791
phenomenon, three-dimensional digital models Introduction The extended duration of orthodontic treatment, particularly in adults, constitutes a considerable barrier to care. Comprehensive fixed appliance therapy generally requires approximately two years to complete [1]. Prolonged treatment duration is associated with an increased risk of root resorption [2], gingival inflammation, dental caries, enamel decalcification, and reduced patient compliance [3]. These potential adverse effects highlight the need for effective approaches to reduce treatment time and have prompted research into methods to accelerate orthodontic tooth movement (OTM). Various surgical and nonsurgical methods have been introduced to accelerate OTM. Nonsurgical methods include self-ligating brackets [4], electrical current stimulation [5], and the injection of pharmacological agents such as platelet-rich plasma [6]. Surgical methods include corticotomy [7], piezocision [8], and microosteoperforation (MOP) [9]. Surgical methods such as corticotomy have demonstrated substantial effects on the rate of OTM [10]. However, conventional corticotomy involving a mucoperiosteal flap is invasive, painful, and costly and often requires the involvement of an additional specialist. MOP is a newer, flapless, minimally invasive alternative that can be performed by the orthodontist [11]. Teixeira et al. proposed that limited cortical perforations could trigger the regional acceleratory phenomenon (RAP), thereby accelerating OTM [11]. However, subsequent studies have reported mixed results regarding its effectiveness [12]. Alikhani et al. reported that MOP could accelerate OTM by two- to threefold [9], whereas Alkebsi et al. found that MOP was not effective in accelerating OTM [13]. Systematic reviews have consistently highlighted the limited quantity and quality of the available clinical evidence [10]. Several biological and mechanical factors are known to influence OTM, including age, sex, study site, study design, magnitude of force, occlusal interference, and anchorage [14]. Most previous clinical studies investigating MOP have focused on the maxillary arch [9,13,15,16], despite the greater cortical thickness and density of the mandible, which may influence treatment outcomes. Furthermore, most studies have evaluated the effects of MOP during individual canine retraction or two-step retraction, with limited investigation of its application during en-masse retraction [9,13,15,16]. En-masse retraction has been reported to reduce treatment time and may decrease the risk of canine tipping and rotation [17]. Nevertheless, a considerable research gap remains regarding the efficacy of MOP in the mandibular arch during anterior en-masse retraction. The present study addresses this gap by evaluating a simplified, potentially cost-effective MOP technique using a lance drill attached to a physiodispenser unit during lower arch anterior en-masse retraction in patients with Class I malocclusion and bidental proclination. This approach aims to provide evidence relevant to contemporary orthodontic practice. Materials And Methods Study design This was a prospective, two-group, comparative observational study evaluating the rate of lower arch enmasse retraction in patients treated with and without MOP. The study is reported in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines. The Institutional Ethics Committee of Pushpagiri College of Dental Sciences approved the study (approval no. PCDS/IEC/M1/08/19) in September 2019. No important changes were made to the study methods after recruitment began. Participants and eligibility criteria Participants were selected from patients undergoing fixed appliance therapy who required extraction of the maxillary and mandibular first premolars and lower arch en-masse anterior retraction. The inclusion and exclusion criteria of the study are listed in Table 1. Participant rights were protected, and informed consent was obtained from parents or guardians, with assent from minors.
2026 G S et al. Cureus 18(10): e118791. DOI 10.7759/cureus.1187912 of 11
Inclusion criteriaExclusion criteria Age 12-18 yearsPrevious orthodontic treatment Angle Class I malocclusion with bidental proclinationSystemic disease Fully erupted permanent dentition (excluding third molars)Current or past periodontal disease Good oral hygieneGingivitis Ovoid lower arch formDental caries Minimal crowding (≤ 4 mm)Poor oral hygiene Mandibular plane angle of 22-32°Oral habits or abnormal perioral muscle activity Normal overbite (1-4 mm)Long-term medication use (especially NSAIDs) Adequate alveolar bone trough widthCanine root prominence TABLE 1: Inclusion and exclusion criteria Group assignment Participants were assigned to the MOP group or the comparison group according to their consent regarding the additional MOP procedure, on a non-randomized basis. The patients who consented to undergo MOP were included in the MOP group, whereas those who did not consent to the procedure were included in the comparison group. As group allocation was based on patient consent rather than randomization, the potential for selection bias was recognized. To limit confounding, strict and identical eligibility criteria were applied to both groups so that they were comparable for the principal known determinants of orthodontic tooth movement (age, occlusion, occlusal interference, periodontal status and anchorage), and baseline comparability between the groups was verified statistically. Sample size consideration The required sample size was estimated a priori using the mean and standard deviation of canine retraction rates with and without MOP reported by Feizbakhsh et al. [15], with a 95% confidence level and 80% power. The estimated requirement was 16 participants (8 per group) and increased to 20 (10 per group) to allow for an anticipated 20% dropout rate. Blinding of outcome assessment Blinding of participants and operators was not feasible given the nature of the MOP procedure. Outcome assessment, however, was blinded: numeric codes were assigned to the digital models so that the assessor was unaware of the group to which each participant belonged. Clinical procedures Before treatment, participants underwent periodontal screening and received oral hygiene instructions. All participants were banded on the first and second molars in both arches, and a transpalatal arch was used for anchorage reinforcement in the maxilla. Fixed appliances (0.022-inch slot MBT prescription, zero-degree torque canine brackets; Minimaster, American Orthodontics, Sheboygan, WI, USA) were bonded by a single operator. The arches were leveled, aligned, and coordinated using the MBT archwire sequence until a 0.019 × 0.025-inch stainless steel working archwire was reached. This archwire remained passive in the bracket slots for at least one month before retraction. Minor anterior spacing was consolidated using figure-of-eight ligatures. Mini-implants (1.5 mm in diameter and 8 mm in length; AbsoAnchor, Dentos, Daegu, South Korea) were placed between the mandibular first molar and second premolar by an orthodontist to provide absolute anchorage. Baseline alginate impressions were obtained before retraction commenced. Participants in the MOP group rinsed with 0.12% chlorhexidine gluconate solution twice for one minute each. Topical anesthesia was then administered using 2% lidocaine, followed by infiltration anesthesia with lidocaine containing adrenaline at a concentration of 1:80,000. An experienced orthodontist performed three linearly distributed MOPs (Figure 1) in the cortical bone, 3 mm distal to the mandibular canine on each side, using a 1.5-mm-diameter lance drill (GDT Implants, Tel Aviv, Israel) attached to a physiodispenser unit (W&H Implantmed, Burmoos, Austria). Each perforation was 1.5 mm wide and 6 mm deep, as determined using the drill's depth calibration. Lower arch anterior en-masse retraction was performed using 12-mm nickeltitanium closed-coil springs (Ormco, Orange, CA, USA), with the force standardized to 150 g per side using a Correx gauge. Retraction commenced immediately after each MOP procedure in the MOP group (Figure 1) and at the corresponding visit in the comparison group (Figure 2). Participants were reviewed every 28 days
2026 G S et al. Cureus 18(10): e118791. DOI 10.7759/cureus.1187913 of 11
for three months. Alginate impressions were obtained at each visit, and MOPs were repeated at each visit for participants in the MOP group. FIGURE 1: Micro-osteoperforation (MOP) group FIGURE 2: Comparison group (without micro-osteoperforation) Outcomes The primary outcome was the rate of lower arch en-masse retraction (mm) over three months. Dental stone models were scanned using a 3Shape R2000D 3D scanner (3Shape Dental Systems, Copenhagen, Denmark). The distance from the cusp tip of the mandibular canine to the buccal cusp tip of the mandibular second premolar was measured on the resulting standard tessellation language (STL) files (Figure 3) to the nearest 0.01 mm on each side using Blender v2.9.2 (Blender Foundation). The reduction in this distance was used as an indirect measure of extraction-space closure during the three-month observation period. To assess intraoperator reliability, 30% of the measurements were repeated after a two-week interval.
2026 G S et al. Cureus 18(10): e118791. DOI 10.7759/cureus.1187914 of 11
FIGURE 3: Rate of en-masse retraction The secondary outcome was pain intensity, measured using a 100-mm visual analogue scale (VAS; Figure 4), where 0 mm indicated no pain and 100 mm indicated the worst imaginable pain. Pain was assessed at 24 hours and 7, 14, and 28 days after each MOP procedure. Following oral instructions, participants marked the scale by hand. The scores were measured using a metric ruler with a precision of 0.5 mm and rounded to the nearest whole millimeter. For statistical analysis, the measurements were converted to a 0-10 scale by dividing the millimeter values by 10. FIGURE 4: Visual analogue scale (VAS) Statistical methods Data were entered into Microsoft Excel (Microsoft Corp., Redmond, WA, USA) and analyzed using IBM SPSS Statistics for Windows, Version 21.0 (Released 2012; IBM Corp., Armonk, NY, USA). Baseline age and preretraction extraction space were compared between groups using independent-samples t-tests, while sex distribution was compared using Pearson’s chi-square test to assess baseline comparability. For the chisquare analysis, the test statistic was reported with its degrees of freedom and sample size, and the phi coefficient (φ) was used as the effect size. Because some expected cell counts were below five, Fisher’s exact
2026 G S et al. Cureus 18(10): e118791. DOI 10.7759/cureus.1187915 of 11
test was also performed. The normality of the tooth-movement data was assessed using the Shapiro-Wilk test. As the data were not normally distributed, the Mann-Whitney U test was used to compare the rate of en-masse retraction between groups, with a 95% confidence interval. The effect size was calculated as r = |Z|/√N. Results were summarized as means and standard deviations. Pain-perception data were also nonnormally distributed. Differences across time points within the MOP group were assessed using Friedman’s test, with the test statistic reported as χ² with its degrees of freedom and Kendall’s coefficient of concordance (W) used as the effect size. Dunn’s post hoc test with Bonferroni adjustment was used for pairwise comparisons. Intra-operator reliability was assessed using the intraclass correlation coefficient (ICC) for the 30% of measurements repeated after a two-week interval. Statistical significance was set at p < 0.05. Results Participant flow Sixty-five patients were assessed for eligibility, of whom 45 were excluded: 28 did not meet the inclusion criteria, and 17 declined to participate. Twenty participants were enrolled, with 10 assigned to each group. Subsequently, one participant in the comparison group and three in the MOP group were lost to follow-up because of irregular attendance during the COVID-19 pandemic. No participants discontinued treatment. The final analysis included nine participants in the comparison group and seven in the MOP group. Baseline data Participants were aged 12-18 years and comprised 3 males (15%) and 17 females (85%). Baseline comparisons of age, sex distribution, and pre-retraction extraction space revealed no statistically significant differences between the groups (Table 2). Sex distribution did not differ significantly between the MOP group (one male and nine females) and the comparison group (two males and eight females) (χ²(1, N = 20) = 0.39, p = 0.531, φ = 0.14), indicating a small effect. Fisher’s exact test yielded a similar result (p = 1.000). ParametersMOP groupControl groupp-value Age (years)15.4 ± 1.9015.6 ± 1.900.816* Sex (percentage) Male, 10% Male, 20% 0.531