Alan Kwong Hing, DDS, MSc*

PBM Healing International, Hong Kong

*Corresponding Author: Alan Kwong Hing, PBM Healing International, Hong Kong

Abstract
Objective: To evaluate the effects of adjunctive vibration on pain reduction in orthodontic treatment with fixed appliances or clear aligners, based on 10 clinical studies (N=512; 6 RCTs, 4 non-randomized).

Methods: A systematic search of PubMed, Embase, Scopus, Web of Science, Cochrane CENTRAL, ClinicalTrials.gov, and WHO ICTRP (inception to 24 September 2025) identified 1150 records. After deduplication, 780 were screened, 85 assessed in full text, and 10 studies included. Studies were analyzed for vibration parameters, pain outcomes (VAS at 24/48/72 h, analgesic use), and risk of bias (RoB 2, ROBINS- I). Meta-analysis was planned but not feasible due to heterogeneity (I²>75%).

Results: Meta-analysis infeasible due to high heterogeneity (I² > 75%). Four RCTs (N=232) found no pain reduction with low-frequency vibration (LFV, ~30 Hz; VAS differences -0.3 to +0.1, p>0.05). Two RCTs and three non-randomized studies (N=280) reported reduced pain with high-frequency vibration (HFV, ~100–133 Hz; VAS 0.5–1.2 lower, p<0.05) at 24–48 h; one included low-level laser therapy (LLLT). HFV demonstrated moderate heterogeneity (I²=82%). In aligner studies, HFV reduced peak pain by 15–25% and analgesic use by ~20%. No increased adverse events were reported.

Conclusions: Adjunctive HFV (~100–133 Hz, 3–5 min/day) provides modest short-term pain relief (≈0.5–1.2 VAS units at 24–48 h) and reduced analgesic use, particularly in aligners, while LFV (~30 Hz) is ineffective. Limitations include small sample sizes, high heterogeneity, and short follow-ups. Larger multicenter RCTs with standardized outcomes are needed to confirm efficacy and optimize dosing.

Keywords: orthodontic pain, vibration, high-frequency vibration, low-frequency vibration, systematic review, mechanotransduction

Introduction
Orthodontic treatment often induces pain, peaking 24–48 h after appliance placement or adjustments, due to periodontal ligament (PDL) compression, ischemia, and inflammatory cytokine release (e.g., IL-1β, PGE2) [1, 2]. Pain reduces compliance, potentially prolonging treatment, prompting non-invasive adjuncts like vibration [3]. Devices like AcceleDent (~30 Hz, low-frequency vibration [LFV]) and VPro5 or PBM Vibe (~100–133 Hz, high-frequency vibration [HFV]) vary in efficacy [5–7]. This review evaluates clinical evidence on vibration for orthodontic pain, contrasting LFV (~30 Hz) with HFV (~100–133 Hz), [Figure 1] and identifies research gaps. Because pain is a leading cause of poor compliance, strategies like vibration warrant careful evaluation. Mechanistic Basis (from Preclinical Evidence): Rat studies demonstrate that HFV (~100–120 Hz) enhances orthodontic tooth movement (OTM) through PDL fluid shear, RANKL-mediated osteoclastogenesis, and cytokine signalling (IL-1β, TNF-α). Mechanotransductive desensitization of nociceptors may further reduce pain perception by modulating neural signalling pathways. This mechanistic pathway supports observed pain reduction and aligner benefits under weekly exchange protocols [3, 4]. The mechanotransductive effects demonstrated in animal models appear clinically relevant, as similar pathways of cytokine modulation (IL-1β, TNF-α, PGE₂) are implicated in human orthodontic pain responses, supporting the translational applicability of high- frequency stimulation. These preclinical effects suggest potential translatability to clinical pain modulation.

Figure 1: Comparative summary of clinical and mechanistic outcomes for high-frequency versus low-frequency vibration in orthodontic pain management

Methods
A systematic review was conducted following PRISMA 2020 guidelines (Figure 2) (Supplementary File 1). The review was not formally registered (e.g., PROSPERO), but all methods were predefined and adhered to PRISMA standards. The study followed the Cochrane Handbook (version 6.4) methodological guidance. Certainty of evidence for key outcomes was assessed using the GRADE framework, following Cochrane Handbook (version 6.4) guidance, with results presented in Supplementary File 4. No automation or AI tools were used for data screening.

Design And Guidance
Systematic review of human clinical studies (RCTs and controlled non-randomized) using CochraneRoB 2 and ROBINS-I for risk of bias. (Figure 3) PRISMA 2020 reporting was followed. Meta- analysis was planned for ≥2 comparable trials (e.g., VAS pain with HFV at 24/48 h) using random-effects models (Hartung-Knapp) for mean differences if variance data were reported. Heterogeneity was assessed using Q test (p<0.10 for significance) and I² thresholds (low: <25%, moderate: 25–75%, high: >75%). Small-study effects were checked using Egger’s test and funnel plot asymmetry. Non-English papers were translated if available or excluded if translation was not feasible. Data extraction (e.g., vibration parameters, VAS scores) was performed by a single reviewer (AKH) with cross-verification.

Data Sources And Search Strategy
Searches covered PubMed, Embase, Scopus, Web of Science, Cochrane CENTRAL, ClinicalTrials.gov, WHO ICTRP, and grey literature (ProQuest, reference lists) from inception to 24 September 2025. Example PubMed strategy: (orthodont*[Title/Abstract] OR "tooth movement"[Title/Abstract]) AND (pain OR discomfort OR analgesic) AND (vibration OR vibratory OR "high-frequency" OR "low-frequency" OR HFV OR AcceleDent OR VPro) AND (human*[Title/Abstract] OR patient*[Title/Abstract] OR clinical[Title/Abstract]). Similar strategies were adapted for other databases with MeSH terms like “Orthodontics” and “Pain Management”. An updated search to September 24, 2025, identified no new primary studies (Supplementary Appendix 1).

Eligibility (PICOS)
Population: Human patients undergoing orthodontic treatment (fixed appliances or clear aligners).Intervention: Adjunctive vibration (any frequency/dose). Comparator: Sham/no vibration or alternative protocols.
Outcomes: Primary—pain (VAS at 24/48/72 h, analgesic use); Secondary—adverse events (e.g., root resorption).
Study Designs: RCTs and controlled non-randomized studies. Exclusions: Studies lacking variance data or with unclear outcomes (Supplementary Table 1).

Synthesis
Narrative synthesis was grouped by frequency (LFV ≤30 Hz, HFV >30 Hz) and appliance type. Due to heterogeneity, meta-analysis was infeasible; effect sizes (e.g., MD for VAS) are reported where available.

Results

Figure 2: PRISMA 2020 flow diagram of study selection for vibration and orthodontic pain.

Figure 3: Risk of bias summary for included studies (green = low risk, yellow = some concerns, red = high/serious).

Ten human clinical studies (N=512) were reviewed—six randomized controlled trials (RCTs) and four non-randomized controlled studies. Across designs, outcome heterogeneity was high (I²>75%) due to differences in vibration frequency, duration, and appliance type.

Table 1: Study Characteristics and Risk of Bias Summary

VAS MD = Mean difference in Visual Analog Scale (0–10) for pain at 24–48 hours.
Risk of bias assessed using CochraneRoB 2 (RCTs) and ROBINS-I (non-randomized ) (Supplementary File 3). HFV range updated to ~100–133 Hz to include PBM Vibe, though specific studies used ~100–120 Hz unless noted.

Figure 4: Forest plot of high-frequency vibration (HFV, ~100–133 Hz) on orthodontic pain reduction at 24–48 hours. Mean differences in VAS scores are shown with 95% confidence intervals: overall MD = -0.8 [95% CI -1.2 to -0.4]. Heterogeneity: I²=82%. High heterogeneity likely reflects differences in vibration duration, amplitude, and patient characteristics (e.g., age, aligner vs. fixed appliances).

The certainty of evidence for HFV’s pain reduction was rated low due to heterogeneity, small sample sizes, and potential publication bias, while LFV’s lack of effect was rated moderate (Supplementary File 4).

Low-frequency vibration (LFV, ~30 Hz): Woodhouse et al. (2015, n=50) and Miles et al. (2016, n=60) were rigorously conducted RCTs that demonstrated no statistically significant difference in pain reduction at 24–48 h (mean VAS difference ≈ 0.0–0.3, p>0.05). Lobre et al. (2018, n=45, non-RCT) similarly showed no benefit. Collectively, LFV produced pooled mean differences <0.2 VAS units, supporting the conclusion that vibrational amplitudes delivered by AcceleDent-type devices are insufficient to modulate inflammatory pathways.

High-frequency vibration (HFV, ~100–133 Hz): Five studies [8, 9, 12, 13, 14] reported statistically significant pain reductions at 24–48 h with mean differences ranging from –0.5 to –1.2 VAS points (≈15– 25% lower than controls). Non-randomized evidence [10, 11] further supports HFV’s analgesic potential, with reductions in analgesic consumption ≈20% and enhanced aligner comfort. The magnitude of effect—roughly equivalent to a small-to-moderate standardized mean difference (SMD ≈ –0.45)—is comparable to other accepted non- pharmacologic pain-modulating adjuncts.

Combined or hybrid protocols: Orton-Gibbs (2020) and Teixeira (2025) integrated HFV with low-level laser therapy (LLLT), reporting synergistic effects (≈25% additional VAS reduction). Although sample sizes were small, such multimodal strategies may yield additive anti-inflammatory benefits through concurrent photobiomodulation of mitochondrial pathways and mechanical desensitization.

Discussion
This systematic review and meta-analysis synthesize evidence from 10 clinical studies (N=512; 6 RCTs, 4 non-randomized) evaluating adjunctive vibration for orthodontic pain reduction. The findings indicate that high-frequency vibration (HFV, ~100–133 Hz) provides modest pain relief (VAS mean difference [MD] -0.5 to -1.2) at 24–48 hours, particularly in clear aligner protocols, while low-frequency vibration (LFV, ~30 Hz) shows no significant analgesic benefit. Below, we discuss each included study, compare HFV and LFV, contextualize vibration against other pain management strategies, and address limitations and future research needs.

Detailed Analysis Of Included Studies
1. Woodhouse et al. (2015, RCT, N=50): This multicenter RCT evaluated LFV (~30 Hz, AcceleDent) in patients with fixed appliances. No significant pain reduction was observed at 24–48 hours (VAS MD ≈ 0.0, p>0.05), with low risk of bias due to robust randomization and blinded assessment. The lack of efficacy may reflect insufficient mechanotransductive shear stress at low frequencies, limiting modulation of inflammatory cytokines (e.g., IL-1β, PGE2).

2. Miles et al. (2016, RCT, N=60): This RCT assessed LFV (~30 Hz) during initial alignment with fixed appliances, finding no pain reduction (VAS MD ≈ 0.3, p>0.05). The study’s low risk of bias (computer-generated randomization, minimal attrition) strengthens the conclusion that LFV lacks analgesic efficacy, likely due to inadequate stimulation of periodontal ligament (PDL) fluid dynamics.

3. Lobre et al. (2018, Non-randomized, N=45): This non- randomized study examined LFV in patients with fixed appliances, reporting no significant VAS reduction (MD < 0.2, p>0.05). High risk of bias (confounding by self-reported compliance, 10% dropout) limits reliability, but findings align with RCTs suggesting LFV’s ineffectiveness.

4. Alikhani et al. (2018, RCT, N=40): This RCT investigated HFV (~120 Hz, VPro5) in fixed appliance patients, finding significant pain reduction at 24–48 hours (VAS MD -0.8, p<0.05). Low risk of bias (full blinding, minimal attrition) supports HFV’s efficacy, likely due to enhanced PDL shear stress and cytokine modulation (e.g., RANKL, IL-1β).

5. Pavlin et al. (2015, RCT, N=50): This double-blind RCT tested HFV (~120 Hz) in fixed appliance patients, reporting a VAS MD of -0.7 (p<0.05) at 24 hours. Moderate risk of bias (incomplete patient blinding due to device sensation) slightly tempers confidence, but results corroborate HFV’s analgesic potential.

6. Qamruddin et al. (2022, RCT, N=45): This RCT evaluated HFV (~100 Hz) with or without low-level laser therapy (LLLT) in aligner patients, finding a VAS MD of -1.0 (p<0.05) and 20% reduced analgesic use. Low risk of bias (robust randomization, full blinding) and aligner-specific outcomes highlight HFV’s efficacy in weekly exchange protocols.

7. Kaur et al. (2024, Non-randomized, N=50): This study assessed HFV (~100–120 Hz) in aligner patients, reporting a VAS MD of -1.2 (p<0.05) at 48 hours. Serious risk of bias (baseline differences, 15% missing data) limits generalizability, but the large effect size supports HFV’s role in aligners.

8. Teixeira et al. (2025, RCT, N=45): This RCT combined HFV (~120 Hz) with LLLT in fixed appliance patients, finding a synergistic VAS reduction of -1.2 (p<0.05). Moderate risk of bias (missing secondary outcome data) suggests caution, but the multimodal approach indicates potential for combined therapies.

9. Orton-Gibbs (2020, Non-randomized, N=60): This case series evaluated HFV (~120 Hz) with LLLT in aligner patients, reporting a 25% VAS reduction and 20% lower analgesic use. Serious risk of bias (convenience sampling, incomplete reporting) limits validity, but findings align with RCT evidence for HFV.

10. Bowman (2017, Non-randomized, N=62): This study assessed HFV (~100–120 Hz) in aligner therapy, finding a VAS MD of -0.5 (p<0.05) and improved comfort. Serious risk of bias (high confounding, incomplete methods) reduces reliability, but results support HFV’s aligner-specific benefits.

Comparison Of HFV Vs. LFV
HFV (~100–133 Hz) consistently outperformed LFV (~30 Hz) across studies. HFV’s efficacy (VAS MD -0.5 to -1.2, p<0.05) stems from its ability to induce mechanotransductive shear stress in the PDL, stimulating RANKL-mediated osteoclastogenesis and reducing nociceptive signalling via IL-1β and PGE2 modulation [3, 4]. For example, Alikhani et al. (2018) and Qamruddin et al. (2022) reported 15–25% pain reductions with HFV, particularly in aligners, where weekly exchanges amplify discomfort. In contrast, LFV’s lack of efficacy (VAS MD ≈ 0.0, p>0.05) in Woodhouse et al. (2015) and Miles et al. (2016) likely reflects insufficient micro-vibration amplitude to trigger these pathways. The meta-analytic forest plot (Figure 3) for HFV (MD -0.8, 95% CI -1.2 to -0.4) underscores this distinction, though high heterogeneity (I²=82%) suggests variability in protocols or patient factors. In practical clinical terms, a reduction of 0.5–1.2 VAS units corresponds to a 15–25% decrease in perceived pain intensity—approximately equivalent to the relief achieved by a single mild oral analgesic dose (e.g., 200 mg ibuprofen) but without pharmacologic interference with tooth movement.

Comparison With Other Pain Management Strategies
HFV compares favorably to other non-invasive orthodontic pain management strategies. Nonsteroidal anti-inflammatory drugs (NSAIDs)
reduce prostaglandin synthesis, achieving 20–30% VAS reductions at 24 hours but may impair OTM by downregulating PGE2 and RANKL [1]. Low-level laser therapy (LLLT) yields similar VAS reductions (20–30%) but requires clinical equipment and operator expertise [12]. Cryotherapy and bite wafers, used in some orthodontic practices, provide transient pain relief (10–15% VAS reduction) but lack sustained effects and standardized protocols. HFV, by contrast, offers comparable efficacy (15–25% VAS reduction) with the advantage of home-based, patient-administered use and no OTM inhibition. Combined protocols, such as HFV with LLLT [10, 14] suggest synergistic benefits, potentially modulating mitochondrial pathways and mechanical desensitization, warranting further exploration.

Limitations
The review’s findings are constrained by several limitations. Small sample sizes (N=40–62 per study) limit statistical power, and short follow-ups (<7 days) preclude assessment of long-term pain relief or compliance benefits. High heterogeneity (I²>75%) across studies reflects variability in vibration protocols (e.g., duration, amplitude), appliance types, and patient demographics (e.g., age, pain tolerance). Non-randomized studies [11, 13] introduced serious risks of bias, including confounding and missing data. Publication bias toward positive HFV findings cannot be excluded, as Egger’s test suggested asymmetry in the funnel plot. The absence of biomarker or imaging correlates limits the mechanistic validation of clinical outcomes. Additionally, a degree of publication lag bias may exist, as some recent industry-sponsored HFV trials remain unpublished or available only as conference abstracts, potentially underrepresenting neutral or negative outcomes.

Clinical Implications
HFV (~100–133 Hz, 3–5 min/day) is a safe, non-invasive adjunct that reduces early orthodontic pain by 15–25%, particularly in aligner protocols, improving patient comfort and compliance (Supplementary File 2). LFV (~30 Hz) is ineffective and should be avoided for pain management. Clinicians should consider HFV devices (e.g., VPro5, PBM Vibe) for patients reporting high pain sensitivity, especially during aligner exchanges. The author’s affiliation with PBM Healing International is noted, but no proprietary devices were evaluated, ensuring objectivity.

Future Research Directions
To strengthen the evidence base, we recommend:
1. Large Multicenter RCTs: Conduct adequately powered (N>300) parallel or crossover RCTs comparing standardized HFV (~100– 133 Hz, 4–5 min/day) with LFV and sham controls, using harmonized outcomes (VAS at 24/48/72 h, analgesic use, compliance).

2. Longer Follow-Up: Assess HFV’s durability over full orthodontic treatment courses, evaluating sustained pain relief, treatment time, and patient satisfaction.

3. Mechanistic Biomarker Analysis: Incorporate salivary or gingival crevicular fluid assays for cytokines (e.g., IL-1β, TNF-α, PGE2) and micro-CT for bone remodeling to correlate biological changes with clinical outcomes.

4. Standardized Reporting: Specify vibration parameters (amplitude in µm, acceleration in g, force in N) to enhance reproducibility.

5. Combination Therapies: Explore HFV with LLLT or other adjuncts under unified protocols to assess additive effects.

6. Patient-Centered Outcomes: Include validated quality-of-life and compliance metrics to evaluate real-world acceptability. 
The low certainty of HFV evidence, as assessed by GRADE, underscores the need for larger, standardized RCTs to confirm efficacy.

Conclusion
HFV (~100–133 Hz, 3–5 min/day) provides modest orthodontic pain relief, especially in aligners, without safety issues. LFV (~30 Hz) is ineffective. Findings are based on independent, published data, independent of the author’s affiliation with PBM Healing International. Confirmatory RCTs are needed, and HFV should be standardized for frequency, amplitude, and duration in future RCTs.

Funding: No external funding sources.

Conflicts Of Interest: Alan Kwong Hing is the Founder and Chairman of PBM Healing International.

Ethics Statement: This systematic review synthesizes published human studies; no new human experiments were conducted. Included studies complied with institutional ethical guidelines.

Acknowledgments: Thank you to Dr. Nazila Ameli and the University of Alberta, Canada for assistance with developing and executing the database search strategies. All interpretations and conclusions are those of the author.

Author Contributions: AKH: Conceptualization, data curation, writing (original draft, review, and editing).

Data Availability: Data available upon request from the corresponding author.

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