Micro-osteoperforation Versus Photobiomodulation Therapy for Accelerating Maxillary Canine Retraction

Background:

Maxillary canine retraction following first premolar extraction represents the most time-consuming phase of fixed orthodontic therapy, often requiring five to eight months under conventional mechanics. Prolonged treatment duration is associated with increased risks of root resorption, periodontal deterioration, white spot lesions, and reduced patient compliance. Several adjunctive techniques have been proposed to accelerate orthodontic tooth movement (OTM), of which micro-osteoperforation (MOP) and photobiomodulation therapy (PBMT) have demonstrated the most consistent clinical evidence. However, no randomized controlled trial has directly compared these two modalities against each other and against a conventional control under standardized conditions.

Rationale for study design:

A three-arm parallel-group randomized controlled clinical trial (RCT) design was selected in preference to a split-mouth design. Although split-mouth designs offer statistical efficiency, the comparison of MOP and PBMT in a split-mouth model is methodologically inappropriate due to: (1) the risk of contralateral biological cross-contamination from the Regional Acceleratory Phenomenon (RAP) induced by MOP; (2) the potential for sub-therapeutic photon scatter from LLLT irradiation reaching contralateral tissues; and (3) the ethical concern of exposing individual patients to two mechanistically distinct and invasive/non-invasive interventions simultaneously. A parallel-arm design with a true control group eliminates these confounders and allows independent evaluation of each intervention's efficacy.

Objectives:

Primary: To compare the rate of maxillary canine retraction (mm/month) at one month and among patients receiving MOP, PBMT/LLLT, or conventional orthodontic treatment alone.

Secondary: To compare total space-closure duration (months)

Participants:

Seventy-five systemically healthy adults (aged 18-40 years) requiring bilateral maxillary first premolar extraction and fixed orthodontic therapy will be recruited from the Department of Orthodontics. Participants will be equally randomized to one of three groups (n = 25 each) using a computer-generated randomization sequence stratified by age (≤25 / >25 years) and sex.

Interventions:

Group A - MOP: Micro-osteoperforations will be performed under local anesthesia using a PROPEL device (or equivalent). Three perforations of 3 mm depth will be placed mesial and three distal to each maxillary canine (six total per side) at baseline and repeated every four weeks until space closure.

Group B - PBMT/LLLT: A 976 nm diode laser (Woodpecker LX16 Plus or equivalent) will be applied at 8 J/cm², 0.13 W, continuous-wave mode at six mucosal sites per canine (three buccal, three palatal) on days 0, 3, 7, and 14, then every two weeks until space closure.

Group C - Control: Standard orthodontic canine retraction using identical elastomeric power chain force (150 g) without any adjunctive intervention.

All groups will use standardized elastomeric power chain force of 150 g, recalibrated at each monthly visit. Teeth will be retracted on 0.019 × 0.025-inch stainless steel archwires with maximum anchorage (skeletal anchorage via miniscrews or equivalent).

Outcome measurement:

The primary outcome (canine movement in mm) will be measured by a single blinded examiner using a digital Vernier caliper (±0.01 mm precision) on dental study models obtained at baseline, one month, and at space-closure completion.

Sample size:

Based on a weighted mean difference of 0.40 mm in canine movement between MOP/LLLT and control groups, a pooled standard deviation of 0.50 mm, α = 0.05, and 80% power for a one-way ANOVA comparison, 21 participants per group are required. Rounding up to 25 per group accommodates a 20% dropout rate, giving a total sample of 75 participants.

Statistical analysis:

One-way ANOVA with post-hoc Tukey's test for continuous normally distributed outcomes; Kruskal-Wallis test for non-normal outcomes; repeated-measures ANOVA for time-dependent data; Pearson or Spearman correlation for age and sex analyses. Significance set at p ≤ 0.05. Intention-to-treat analysis will be the primary analysis, with per-protocol analysis as a sensitivity check.

Ethics and registration:

Ethical approval obtained from the Institutional Review Board before recruitment. Written informed consent will be obtained from all participants. The trial is prospectively registered on ClinicalTrials.gov prior to enrollment of the first participant, in compliance with ICMJE guidelines and publication requirements.

Inclusion criteria

• Age 18 to 40 years at the time of enrollment
• Systemically healthy with no chronic medical conditions affecting bone metabolism or wound healing
• Requiring bilateral maxillary first premolar extraction as part of a comprehensive fixed orthodontic treatment plan
• Class I or mild Class II malocclusion requiring maximum anchorage canine retraction
• Fully erupted maxillary permanent dentition with no missing teeth other than planned extraction teeth
• Good oral hygiene (Plaque Index ≤ 1) and healthy periodontal status (probing depth ≤ 3 mm, no bleeding on probing)
• No previous orthodontic treatment
• Willing to attend all scheduled appointments and comply with study protocol
• Able to provide written informed consent

Exclusion criteria

• Systemic diseases affecting bone metabolism including osteoporosis, osteopenia, diabetes mellitus, thyroid disorders, or autoimmune conditions
• Current use of medications affecting bone remodeling including corticosteroids, bisphosphonates, non-steroidal anti-inflammatory drugs (NSAIDs), or vitamin D supplements
• Current or recent smokers (within the past 6 months)
• Pregnant or breastfeeding women
• History of head and neck radiation therapy
• Periodontal disease or active dental infection at the time of enrollment
• Skeletal Class III malocclusion or severe Class II requiring surgical intervention
• Previous orthodontic treatment or orthognathic surgery
• Craniofacial syndromes or cleft lip and palate
• Photosensitivity disorders or use of photosensitizing medications (relevant to LLLT group)
• Coagulation disorders or anticoagulant therapy (relevant to MOP group)
• Uncooperative patients or those unable to maintain adequate oral hygiene throughout treatment
• Parafunctional habits such as severe bruxism or tongue thrusting'