The effect of micro-osteoperforation (MOP) in molar distalization treatments: an exploratory systematic review and meta-analysis of RCTs

Abstract

Objective

Molar distalization is a therapeutic approach commonly used for treating Class II malocclusions. However, the extended duration of this treatment often leads to its replacement with alternative methods that offer shorter treatment times. Micro-osteoperforation (MOP) has been introduced as a technique aimed at accelerating tooth movement and reducing treatment duration. The purpose of this study is to evaluate the impact of MOP on molar distalization outcomes to provide evidence for its effective and safe use.

Search methods

A comprehensive search was conducted across multiple databases, including MEDLINE, Web of Science, EMBASE, Scopus, and Cochrane’s CENTRAL, up to April 2024, without any language or date restrictions.

Selection criteria

Only randomized clinical trials (RCTs) that addressed the defined PICO question were included in the analysis. The risk of bias in the included studies was assessed using the Cochrane Risk of Bias 2.0 (RoB 2) tool.

Data collection and analysis

Relevant data were extracted using custom-designed forms, and a random-effects inverse variance meta-analysis was performed to synthesize the results. The primary outcomes analyzed were the rate and amount of molar distalization, while secondary outcomes included pain levels, root resorption, and periodontal health.

Results

Four RCTs, involving a total of 71 participants, were included in this exploratory review. Most studies were at low or some concerns risk of bias. The meta-analysis revealed no significant differences in the rate or amount of molar distalization between the MOP and control groups (mean difference [MD] = 0.1 mm/month and 0.01 mm, respectively, P > .05). However, the MOP group reported significantly higher pain levels on the day of the procedure (MD = 2, P = .01) on a 10-point visual analog scale (VAS) compared to the control group. This difference in pain perception was no longer significant seven days after the procedure (MD = 0.52, P = .52).

Conclusion

While MOP is associated with increased immediate postoperative pain, it does not significantly enhance the efficiency of molar distalization. Therefore, the use of MOP for distalization should be judiciously considered and reserved for cases that involve particularly challenging or prolonged movements, based on the specific needs and characteristics of each patient. Limitations of this review include the small number of available RCTs and variability in MOP protocols, which may limit the generalizability of the findings.

Registration

The protocol for this systematic review was registered at PROSPERO with the ID CRD42024589482

Introduction

The duration of orthodontic treatment has long been a concern for both clinicians and patients [1]. Extended treatment times not only affect patient satisfaction but also increase the likelihood of complications such as root resorption, periodontal issues, white spot lesions, oral hygiene problems, and even bracket debonding or wire fractures [2, 3]. Moreover, they can heighten the risk of alveolar bone remodeling complications and prolong the financial and logistical burdens on patients, who may need more frequent appointments and time off work or school [4]. In orthodontics, particularly in treatments involving molar distalization, the prolonged treatment period can negatively affect patient compliance and lead to increased discomfort and aesthetic concerns, which, in turn, can influence patients’ psychological well-being [5]. Consequently, many patients seek alternatives such as implants, veneers, or prosthetic treatments, which, while offering quicker aesthetic results, may lead to suboptimal functional outcomes [3].

Maxillary molar distalization is a technique commonly employed in non-extraction orthodontic treatments for the correction of Class II malocclusion. Traditional methods of molar distalization, such as headgear, distalizing arches, or intraoral appliances like the pendulum, have shown efficacy but are often time-consuming and rely heavily on patient compliance, particularly in the case of extraoral appliances [6, 7]. More recently, temporary anchorage devices (TADs)—including interradicular, palatal, and zygomatic miniscrews—have been employed to reduce the undesired reciprocal effects of molar distalization on anchorage teeth, and allowing for much more effective and efficient whole arch distalization [7]. Furthermore, clear aligners, alone or in combination with mini-screw anchorage, provide an aesthetically appealing option that may increase patient willingness to cooperate and have been proven to be as effective as fixed appliances for distalization [8]. However, because aligners still rely on consistent patient adherence, they perform similarly to extraoral appliances in this regard. Furthermore, both of these newer methods suffer from the same prolonged treatment times in patients as the old methods [9].

In adult patients, the challenge becomes even greater, as the rate of orthodontic tooth movement is slower compared to adolescents due to diminished bone remodeling capacity [10]. In such cases, the extended treatment duration often pushes clinicians toward alternative treatments, such as premolar extraction, which can have undesirable effects on the facial aesthetics of patients with retroclined incisors. Therefore, accelerating tooth movement, especially in these patients, holds significant importance for orthodontic specialists.

To address the challenge of reducing the total duration of orthodontic treatment, various methods have been employed, including self-ligating brackets, customized brackets and wires, the use of pharmaceuticals, local injections, low-level laser therapy, electromagnetic fields, mechanical vibrations, corticotomy with or without bone grafting, osteotomy, piezo-incision, and micro-osteoperforation (MOP) [11–14]. These techniques have been applied with varying degrees of success to expedite orthodontic treatment timelines. The MOP technique involves creating small perforations in the alveolar bone to stimulate the biological processes underlying bone remodeling [15]. MOP is believed to increase the expression of inflammatory markers such as cytokines, which in turn enhance the recruitment of osteoclasts to the site of tooth movement, accelerating the process [16]. Studies have suggested that MOP can significantly reduce treatment duration without the need for more invasive procedures such as corticotomies [16, 17].

However, while MOP has demonstrated potential in expediting orthodontic tooth movement, there remain concerns regarding its safety and long-term outcomes. Some research has indicated that MOP may lead to an increased risk of root resorption, particularly in areas such as the mesio-buccal root of the first maxillary molar during distalization [18]. Moreover, there is limited evidence on whether MOP consistently accelerates tooth movement across different clinical scenarios or whether the results are dependent on factors such as patient age, bone density, or the specific biomechanics of distalization. To date, no systematic review has comprehensively evaluated the effectiveness of MOP in this context, nor has there been an in-depth assessment of its potential risks. Therefore, the present systematic review aims to address this gap by critically assessing the available evidence on the use of micro-osteoperforation in patients needing molar distalization, compared with a non-MOP control group, with a focus on its efficacy in accelerating tooth movement, its impact on root resorption, and other associated risks.

Materials and methods

Study design and study protocol

We adhered to the recommendations provided in the Cochrane Handbook for Systematic Reviews of Interventions and followed the guidelines set by the PRISMA framework [19]. Furthermore, our study protocol was preemptively registered in the International Prospective Register of Systematic Reviews (PROSPERO) under the registration number #CRD42024589482.

Eligibility criteria

Study selection was based on the PICO model, focusing on orthodontic patients needing molar distalization (Population), evaluating the impact of micro-osteoperforation (MOP) (Intervention), and comparing outcomes with a control group of patients who did not receive MOP (Comparison). The key outcomes assessed included the degree of molar distalization, the speed of tooth movement, side effects such as pain and root resorption, as well as the periodontal health of the teeth (Outcome). We included all relevant clinical trials and cohort studies that met these PICO criteria, regardless of publication date or language, while excluding studies lacking a control group or MOP group. Additionally, studies were excluded if they focused on patients with craniofacial anomalies, those undergoing orthognathic surgery, or if they were conducted on non-human subjects.

Search strategy and data sources

Our literature search spanned various databases, including MEDLINE, Web of Science, EMBASE, Scopus, and Cochrane’s CENTRAL, covering all available records up to April 10, 2024. In addition to this, we manually searched top-tier Q1 orthodontic journals and reviewed reference lists from relevant studies. Online trial registries were also explored, and when necessary, we contacted original authors for additional insights. Conference proceedings and academic theses featuring the keywords ‘MOP’, ‘Micro-Osteoperforation’, and ‘Distalization’ were included. A detailed breakdown of the search strategies for each database can be found in Table 1.

Selection process for studies

Following the PICO framework, two reviewers (MG, EB) independently screened the study titles and abstracts. Any disagreements between the reviewers were resolved through discussion, and if consensus was not reached, a third author (HS) was consulted to make the final decision. Studies that did not meet the PICO criteria were excluded. Full-text versions of the selected studies were then obtained, and their eligibility was reassessed using the same PICO criteria.

Data extraction

Data extraction from the included studies was conducted using a pre-designed form, which was initially pilot-tested on two studies. The extraction process was carried out independently by two reviewers (EB and MG), who addressed any discrepancies through collaborative discussion. The extracted information covered several important aspects, such as the publication year, study design, participant demographics, treatment duration, number and placement of MOPs, the type of device used for MOP (e.g. mini-screw or PROPEL system), depth of MOP, frequency of application, and the intervals between treatments. We also evaluated the methods for molar distalization (e.g. TAD or Pendulum), measurement techniques (e.g. digital scans or casts), and various outcomes, including distalization distance and rate, root resorption, pain levels, and periodontal health indicators. For cases where data were incomplete, we actively sought clarification from the original study authors.

Risk of bias and quality assessment

Since all the studies included in our review were randomized controlled trials, we utilized the ROB 2 tool (Cochrane’s Risk of Bias Tool) to assess potential biases [20]. This tool examines five key areas: the process of randomization, deviations from the planned interventions, missing outcome data, the measurement of outcomes, and the selection of reported results. Each of these areas is rated as Low risk, Some concerns, or High risk. This assessment was carried out independently by two reviewers (EB and MG).

For studies classified under ‘some concerns’, we noted issues such as incomplete details on the randomization sequence, unclear allocation concealment methods, lack of a previously registered protocol for a study or unspecified blinding procedures for outcome assessors. Such ambiguities can introduce a moderate risk of bias, even if the clinical findings remain robust.

Furthermore, we evaluated the quality and reliability of the evidence using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) system. GRADE assesses evidence quality based on several criteria, including study design (randomized vs. non-randomized), risk of bias, inconsistencies in results, indirectness of the evidence (relevance to the outcome), imprecision (t risk of measurement error), and additional factors such as publication bias, differences between groups, dose-response relationships, and confounding variables. The system classifies the evidence into four categories: high, moderate, low, and very low.

Data integration and analysis

For the meta-analysis, we selected studies with comparable therapeutic interventions and outcome measures. We primarily focused on the degree of molar distalization achieved using various distalization devices, both with and without the application of micro-osteoperforation (MOP). Additionally, we evaluated secondary outcomes including the rate of distalization and pain intensity. Distalization was measured as the amount of molar movement in millimeters throughout the treatment duration, with the rate of tooth movement assessed as the distalization achieved after one month. Pain was quantified using a 10-point Visual Analogue Scale (VAS).

Given the continuous nature of our outcomes, we calculated the Mean Difference (MD) and utilized a random-effects inverse variance meta-analysis to accommodate variability among the studies. We assessed heterogeneity with the Chi-squared Q test and the I² statistic, interpreting values below 30% as indicating low heterogeneity, values between 30% and 60% as reflecting moderate heterogeneity, and values above 60% as suggesting high heterogeneity. All analyses were performed using STATA software (version 17, STATA Corp, College Station, TX, USA), with a 95% confidence interval (CI) and a P value threshold of less than 0.05 to determine statistical significance.

Results

Study selection

After conducting a comprehensive search across online databases, we initially identified 809 studies. Following the removal of duplicates, 628 unique studies were available for evaluation based on their titles and abstracts. Using the PICO criteria for inclusion and exclusion, we discarded 602 studies. This included 95 studies involving animals or laboratories, cross-sectional studies, and surveys; 97 review articles or book chapters; 146 studies unrelated to orthodontics; and 86 case reports or case series. Furthermore, 178 clinical studies were excluded for various reasons: 105 investigated MOP unrelated to dental distalization, 37 concentrated on distalization without MOP, and 36 were not relevant to either MOP or distalization.

A detailed review of the remaining 26 studies, supplemented by 7 additional studies found through gray literature, manual reference searches, and key orthodontic journals, led to the selection of four studies that met our inclusion criteria. Consequently, our exploratory systematic review and meta-analysis focused on the research by Gulduren et al., Bahaa El-Din et al., Alkassaby et al., and Ellaithy et al. [18, 21–23]. The study selection process is illustrated in Fig. 1.

Study characteristics

Out of the reviewed literature, four studies were chosen for our systematic review and meta-analysis, all conducted between 2022 and 2024 using a randomized clinical trial methodology. These studies are summarized in Table 2. Alkasaby [18] and Ellaithy [21] used a split-mouth design, whereas Bahaa El-Din [23] and Gulduren [22] employed a parallel-group design. The participant count in these studies ranged from 10 to 27, all consisting of adults with completed growth.

In the studies, Bahaa El-Din and Gulduren [22, 23] utilized six MOPs placed in three locations: two between the first premolar and first molar, two between the first and second molars, and two distal to the second molar. Ellaithy [21] placed three MOPs in two areas: distal to the upper first and second molars. Alkasaby [18] employed three MOPs in one area: distal to the upper first molar. MOPs were applied using mini-screws in the studies by Alkasaby, Bahaa El-Din, and Gulduren [18, 22, 23], while Ellaithy [21] used the PROPEL device.

All four of the included studies employed TADs as the anchorage method ensure stable distalization mechanics.Distalization methods included the Fast Back Distalizer in Alkasaby’s study [18], the Distal Jet in Bahaa El-Din and Gulduren’s studies [22, 23], and the BAPA (Bone-Anchored Pendulum Appliance) in Ellaithy’s study [21]. All four of the appliances in the studies used palatal miniscrews. Alksaby, Bahaa El-Din, and Ellaithy et al. used two miniscrews inserted on either side of the anterior paramedian region of the palate, whereas Gulduren used two miniscrews anterior and posterior in the anterior midpalate. The assessments covered tooth movement amount and rate, pain levels, root resorption, and periodontal status.

Risk of bias within studies

The studies included in our review were assessed using the Cochrane ROB 2.0 tool. Out of these, two studies [21, 22] raised ‘some concerns’ regarding overall bias, while the remaining two [18, 23] were classified as having a low risk of bias.

Regarding randomization procedures, Gulduren’s study [22] mentioned that the intervention was randomly assigned to one side of the mouth but did not specify the details of the randomization process or allocation concealment. Conversely, other studies provided comprehensive details on their randomization and allocation concealment techniques.

In terms of deviations from intended interventions, blinding of participants or practitioners was not feasible due to the nature of the treatments. Nonetheless, because the primary outcomes were measured using objective methods, the risk of bias in this area was considered low. For missing outcome data, the studies either reported no dropouts in any groups as in Alkasaby and Ellaithy’s studies [18, 21], or had similar dropout rates with stated reasons across all groups as in Bahaa El-Din and Gulduren’s studies [22, 23].

Regarding the selection of reported results, Alkasaby and Bahaa El-Din [18, 23] had pre-registered protocols available, and no deviations from the planned objectives were noted. However, registered protocols for Gulduren and Ellaithy [21, 22] were not found. A summary of the bias assessment results is provided in Fig. 2.

Synthesis of results

Root resorption and periodontal status

Although no meta-analysis could be performed for root resorption and periodontal parameters since there was not enough studies to do so, there is some correlation between MOP and mild root resorption reported by at least one study. Alkasaby et al. [18] reported a slight but statistically significant reduction (0.2 mm) in the mesiobuccal root length of the maxillary first molar in the MOP group, alongside decreased bone density in the second and third layers around In contrast, Gulduren et al. [22] discovered no significant differences in plaque index, gingival index, pocket depth, or bleeding on probing between the MOP and control groups, indicating that MOP had no negative effect on periodontal parameters during molar distalization in their study. These divergent findings underscore the potential influence of local biological factors, though sample sizes remain small.

Amount and rate of distalization

The meta-analysis, encompassing three studies with 70 participants, examined both the amount and rate of molar distalization. The analysis revealed no significant difference in the amount of distalization between the MOP and control groups (MD = 0.01 mm, 95% CI = −0.13–0.15, P = .9), with moderate heterogeneity (I² = 42%) (Fig. 3a). Although the MOP group demonstrated a marginally faster rate of distalization, this difference was neither statistically nor clinically significant (MD = 0.1 mm/month, 95% CI = −0.02–0.22, P = .11). The studies exhibited moderate heterogeneity in this aspect as well (I² = 56%) (Fig. 3b).

Pain levels

A separate meta-analysis of two studies involving 36 patients was performed to assess pain levels, given the low heterogeneity. On the day of the procedure, the MOP group reported significantly higher pain levels compared to the control group (MD = 2, 95% CI = 0.43–3.57, P = .01), with no observed heterogeneity between the studies (I² = 0%) (Fig. 4a). However, this difference in pain levels was not significant seven days after the procedure (MD = 0.52, 95% CI = −1.05–2.08, P = .52, I² = 10%) (Fig. 4b).

Risk of bias across studies

The quality of evidence and certainty of outcomes were assessed using the GRADE system. The evidence related to the amount and rate of tooth movement was classified as moderate, largely due to the presence of heterogeneity and the moderate risk of bias in the included studies. Similarly, the evidence for pain levels received a moderate rating, primarily due to the limited number of studies and the moderate risk of bias. The GRADE ratings are summarized in Supplementary Table 1.

Discussion

Summary of results

In this exploratory meta-analysis we evaluate the rate and extent of tooth movement, side effects such as pain and root resorption, and periodontal health. The analysis revealed no significant differences in the rate or amount of distalization between the MOP and control group. However, patients in the MOP group reported significantly higher pain levels, with a 2-point difference on a 10-point VAS on the day of the procedure. This pain difference became negligible after seven days.

These findings indicate that while MOP increases pain during the distalization process, it does not offer any clear advantage in terms of the amount or rate of tooth movement. The extent of distalization is typically influenced by factors like treatment design and the extraction of second or third molars, so it was not expected that MOP would significantly impact this aspect. Although acceleratory interventions like MOP were anticipated to enhance the rate of distalization, our meta-analysis demonstrated that the increase was neither statistically nor clinically significant, casting doubt on MOP’s effectiveness for this purpose.

The role of MOP in accelerating tooth movement has been widely debated. Early studies and systematic reviews suggested that MOP could significantly speed up tooth movement [17, 24], sparking optimism about its potential to reduce treatment time and improve outcomes. However, more recent studies have provided less compelling evidence [25]. Similar to our study, current findings suggest that the benefits of MOP may not be as substantial as initially believed. For instance, Dos Santos et al. [26] found no significant acceleration of tooth movement when MOPs were performed with the Propel system, nor did they observe increased risk for root resorption, anchorage loss, or heightened patient discomfort [26]. Similarly, other reviews (e.g. Fu et al. [27],; Shahabee et al., 2019; Sivarajan et al. [28],) reported that, while MOP may produce a modest initial enhancement in tooth movement, it often fails to achieve clinically meaningful acceleration when evaluated over longer follow-up periods [26–30]. Based on this evidence, it is recommended that MOP be reserved for complex cases requiring difficult tooth movements where other methods have proven inadequate. This selective use would maximize the potential benefits of MOP while minimizing unnecessary patient discomfort.

In conclusion, the results of this meta-analysis suggest that while MOP may increase patient discomfort, it does not significantly improve the efficiency of distalization and is therefore not recommended for routine distalization cases. Some studies have proposed that MOP may influence anchorage requirements, which could be advantageous in distalization treatments utilizing dental anchorage [31, 32]. However, until more targeted research is conducted on MOP’s effects on anchorage, its role in distalization remains uncertain.

Factors affecting the outcome and other considerations

Several factors can influence the outcomes observed in studies evaluating MOP in molar distalization. All included studies employed temporary anchorage devices (TADs) to support anchorage during the distalization process. The insertion of TADs themselves may trigger local trauma that affects bone metabolism, potentially masking the independent effects of MOP. However, Gulduren et al. [22] found no significant difference in tooth movement on the contralateral arch between the MOP and control groups, indicating that the stimulatory effect of MOP is localized to a specific area. Consequently, TADs positioned bilaterally near the palatal raphe may not substantially influence distalization rates, as the impact of MOP seems to be region-specific.

Moreover, two out of the three studies that assessed distalization rates performed MOP only once, at the beginning of the treatment [18, 21]. It has been suggested that the acceleratory effects of MOP are transient and most effective in the short term, requiring repeated applications throughout the treatment to sustain their benefits [33]. In contrast, Gulduren et al. [22], who employed multiple MOP applications, reported significant differences in tooth movement between the MOP and control group during the distalization process. Further research is required to clarify whether repeated MOP applications could be a viable strategy to enhance molar distalization effectively. Despite the observed increase in distalization rate with repeated MOP in Gulduren et al.’s study [22], the improvement was only around 20%, suggesting a modest clinical effect.

Previous research has recommended applying two to three MOPs per interdental space for optimal results [34]. However, the number of MOPs varied significantly among the studies included in our review. For instance, Alkasaby et al. [18] applied three MOPs distal to the first molar, while Bahaa El-Din et al. [23] utilized twelve MOPs on both buccal and palatal aspects in the interdental spaces between the second premolar, first molar, second molar, and the distal side of the second molar in one of the intervention groups. Although earlier studies did not conclusively demonstrate a significant effect of the number of MOPs on treatment outcomes, increasing the number of MOPs could potentially enhance their effectiveness [29, 35]. Nonetheless, Bahaa El-Din et al. [23] reported that performing six or twelve MOPs did not significantly affect the pain levels experienced by patients undergoing the intervention.

Another critical factor that can impact the rate and amount of distalization is the extraction or presence of second or third molars. Studies have indicated that third molar extraction facilitates faster molar distalization with less tipping [36]. Extracting the second molar also plays a significant role in enhancing distalization rates and can even lead to molar movement and malocclusion correction without auxiliary appliances in mild to moderate Class II cases [37]. Additionally, distalization in patients without erupted third molars is associated with an increased risk of molar impaction [38].

Among the studies reviewed, none had a standardized protocol for second or third molar extraction as part of their intervention. However, Gulduren et al. [22] included patients with missing or extracted third molars as part of their inclusion criteria, while Alkasaby et al. [18] required the presence of the third molar for patient eligibility. Interestingly, Gulduren et al. observed a higher distalization rate compared to Alkasaby et al., even though both studies reported similar rates of tooth movement between the MOP and control groups. Based on previous studies, it might be advisable to include third molar extraction in distalization protocols when using MOPs [36].

Distalization generally leads to molar tipping and extrusion [39]. When dental anchorage is employed for distalization, there is also a risk of mesial tipping and extrusion of the anchoring teeth [39]. However, since all the studies reviewed utilized skeletal anchorage, it was not possible to assess the effects of MOP on anchorage stability or the movement of opposing teeth. Ellaithy et al. [21] compared vertical and sagittal displacement, as well as tipping of central incisors, premolars, and molars between the MOP and control groups. These movements followed predictable patterns seen in earlier distalization studies [40], showing similar displacement and tipping for most teeth in both groups, except for the central incisors. In the control group, the central incisors tended to move labially, while in the MOP group, they moved palatally. This difference was attributed to less anchorage loss on the MOP side, but this explanation does not fully account for the variations observed, considering the distalizer design and skeletal anchorage.

Surgical acceleratory techniques like corticotomy, piezocision, and MOP stimulate the Regional Acceleratory Phenomenon (RAP), enhancing bone remodeling and osteoclast activity in the treated area [41–43]. This increased osteoclast presence can contribute to a higher risk of root resorption [44]. While some studies have suggested that MOP might increase the likelihood of external apical root resorption (EARR) [45, 46], others have not found a significant correlation [47, 48]. A systematic review by Mosayebi et al. [49] highlighted limited evidence suggesting that MOP may slightly elevate the risk of EARR. Alkasaby et al. [18] evaluated root length and bone density around the roots of the maxillary first molar before and after distalization with and without MOP. They found a slight but statistically significant reduction (0.2 mm) in root length for mesiobuccal roots and decreased bone density around the molar roots in the MOP group, suggesting a potential for mild root resorption.

The impact of MOP on periodontal parameters during distalization was also investigated by Gulduren et al. [22], who found no significant differences between the MOP and control group in terms of plaque index, gingival index, pocket depth, or bleeding on probing. These findings are consistent with previous studies that examined MOP for canine retraction and incisor alignment [50, 51].

Patient-reported outcome measures (PROMs) are a vital aspect of orthodontic treatments but are sometimes overlooked in clinical research [52]. Considering the extended duration of orthodontic treatments, addressing patient comfort and overall experience is crucial [52]. Mousa et al. [53] observed that in minimally invasive surgical procedures like MOP and piezocision, mild to moderate swelling, functional impairment, pain, and discomfort were noticeable on the first day, but these effects subsided within a week. Similarly, our meta-analysis revealed comparable pain levels on the first day and a week following MOP application. Gulduren et al. [22] also assessed other aspects like discomfort, difficulty eating, and speech problems, with no significant differences observed between the MOP and control groups.

In conclusion, utilizing MOP in distalization treatment appears to increase pain and root resorption without significantly enhancing the rate or amount of tooth movement. Given these outcomes, MOP should be reserved for cases that require particularly complex or prolonged orthodontic movements Specific cases where MOP might be beneficial include patients who exhibit very slow or refractory tooth movement due to high bone density or those unwilling to undergo more invasive procedures (e.g. corticotomies). In such scenarios, the transient spike in discomfort may be outweighed by the potential modest acceleration of tooth movement. However, this approach should be individualized based on patient-specific factors, such as overall health status, age, and bone quality.

Strengths, limitations, and recommendations for future research

A major strength of this review is its focus on randomized controlled trials (RCTs), which provide a high level of evidence and contribute to the reliability and credibility of the findings. The meta-analysis also includes a comprehensive examination of the effects of MOP on molar distalization, considering multiple relevant outcomes, such as the rate and extent of tooth movement, pain levels, root resorption, and periodontal health. Emphasizing patient-reported outcome measures (PROMs) underscores the importance of patient comfort and experience during orthodontic treatment, a critical consideration given the typically extended treatment durations.

However, there are several limitations to note. The small number of studies included in the meta-analysis restricts the generalizability of the results, potentially limiting their applicability across broader clinical settings. Moreover, there was considerable heterogeneity among the studies regarding intervention protocols, such as the number and placement of MOPs and the outcomes evaluated, which complicates drawing clear, definitive conclusions.

Future research should prioritize developing standardized protocols for MOP and tooth extraction methods to enhance comparability across studies. Although our meta-analysis is exploratory in nature, its findings—aligned with previous systematic reviews—indicate that MOP does not produce clinically significant increases in the rate of tooth movement compared to control groups. Moreover, it appears that MOP may be associated with higher levels of patient discomfort or pain. Given these observations, further large-scale investigations focused exclusively on distalization with MOP may not be strictly necessary to establish efficacy. Instead, future efforts could concentrate on clarifying potential movements that might benefit from MOPs and evaluating MOPs’ broader effects, including their potential impact on root resorption, periodontal health, and anchorage management. They could also explore whether repeated MOP procedures might offer advantages in select cases.

Conclusion

Based on the findings of this exploratory systematic review and meta-analysis, there was no significant difference in the rate or amount of molar distalization between the MOP and control groups. However, patients in the MOP groups experienced notably higher levels of pain, with a 2-point increase on the Visual Analog Scale (VAS) on the day of the procedure. This increase in pain was not significant seven days post-procedure. These results suggest that MOP may elevate immediate post-operative discomfort but does not significantly enhance the efficiency of molar distalization. Therefore, the application of MOP should be carefully evaluated and is best reserved for complex or refractory tooth movements where other methods have proven inadequate or when slightly faster movement is prioritized over patient comfort concerns.

Acknowledgements

None to report.

Conflict of interest

None to declare.

Funding

This study was self-funded.

Data availability

The data supporting the findings of this study are available upon reasonable request from the corresponding author.

References