The duration of extraction orthodontic treatment is 28 months on average, which is 5 months longer than non-extraction treatment [1]. Extended orthodontic treatment can lead to negative consequences such as external apical root resorption, enamel demineralization spots, dental caries, gingivitis, and periodontitis. In addition, patient cooperation decreases, which can directly affect the treatment outcome [2]. For these reasons, methods that accelerate orthodontic tooth movement (OTM) increase treatment efficiency and reduce the risk of adverse effects are of great importance [3].

Corticotomy is one of the oldest methods for accelerating orthodontic tooth movement. The first to apply this method in practice was Heinrich Köle in 1959 [4]. Although Köle’s method speeds up orthodontic tooth movement, it is invasive, as it requires lifting a mucoperiosteal flap, causing pain and discomfort for patients [5]. One of the more recent proposed methods is to use high-energy laser therapy (HELT) to perform corticotomy to trigger the regional acceleratory phenomenon (RAP). Erbium fiber lasers can remove both soft and hard tissues without physical contact with the bone, allowing the procedure to be performed without raising a mucoperiosteal flap [6]. The compact bone is cut with minimal thermal damage and healing after the procedure is faster than with bone drilling [6,7]. For these reasons, this method is considered one of the minimally invasive surgical approaches to accelerating OTM [8].

Despite the widespread use of HELT in medicine, few studies assess its effectiveness in corticotomy procedures aimed at accelerating tooth movement [9]. The only published systematic literature review, conducted by Shaadouh et al. [10], presented low to moderate quality evidence supporting the effectiveness of flapless laser corticotomy (FLC) in accelerating OTM, at least during the first two months. So far, no systematic literature reviews and meta-analysis have been conducted examining the effect of FLC on canine distalization after first premolar extraction.

This systematic review and meta-analysis aim to evaluate the effectiveness of flapless laser corticotomy in accelerating canine distalization during extraction-based orthodontic treatment.

Protocol and registration

The present study was registered conducted in accordance with the guidelines outlined in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 statement [11].

The protocol was at the International Prospective Registry of Systematic Reviews (PROSPERO) database (registration number: CRD420251055675) and conducted per protocol. The protocol can be accessed at: www.crd.york.ac.uk/PROSPERO/view/CRD420251055675.

Focus question

The focus question was structured using the Population, Intervention, Comparison, and Outcome (PICO) framework (Table 1): patients undergoing orthodontic treatment with maxillary first premolar extraction and canine distalization (P), laser-assisted corticotomy (I), comparison with conventional orthodontic treatment without corticotomy (C), and acceleration of maxillary canine distalization (O).

The focus question was: “Does laser corticotomy during orthodontic treatment accelerate maxillary canine distalization after first premolar extraction?”

Information sources

An electronic search was conducted using the databases PubMed, The Cochrane Library, ScienceDirect and Web of Science. Additionally, to ensure comprehensive coverage, the included literature’s reference list was manually searched, and sought through Google Scholar.

Search strategy

Keywords were used in various combinations with Boolean operators (AND, OR) to perform online searches: (Orthodontic Tooth Movement OR Movement OR Orthodontic Tooth OR tooth movement OR teeth movement OR canine retraction OR teeth retraction OR Tooth Displacement OR Accelerated Orthodontic Treatment OR Accelerated Orthodontic OR Rapid tooth movement) AND (Minimal invasive OR Laser corticotomy OR HELT OR high-energy laser OR laser-assisted flapless corticotomy OR lasercision). The databases were searched for English-language studies up to August 31, 2025, with no year restriction applied.

Selection of studies

Two reviewers (E.J. and M.V.) independently screened the titles and abstracts of the identified publications according to the eligibility criteria. Any discrepancies were resolved through discussion with the senior author (A.V.). Full texts of the selected studies were manually retrieved and assessed autonomously by the same two reviewers (E.J. and M.V.). For excluded studies, reasons for exclusion were recorded following group discussion. Any disagreements between the reviewers were resolved by consensus in consultation with a third reviewer (A.V.) who was not involved in the initial selection process. Publications that met the predefined inclusion criteria proceeded with data extraction.

Types of publication

The present study included all human split-mouth randomized clinical trials (RCTs) that investigated the effect of laser-assisted corticotomy on the rate of maxillary canine distalization following first premolar extraction during fixed orthodontic treatment.

Types of studies

All studies published in English up to August 31, 2025 were included, without any year restrictions.

Types of participants

Patients treated with fixed orthodontic appliances after first premolar extraction and canine distalization, during which laser-assisted corticotomy was performed, without age restrictions.

Inclusion criteria

Studies were eligible for inclusion if they met the following conditions:

Exclusion criteria

Studies were excluded if they met any of the following conditions:

Sequential search strategy

The selection process comprised four stages:

Two authors (E.J. and M.V.) independently reviewed titles and abstracts, with inter-rater reliability verified on 10% of publications using Cohen’s kappa (κ).

Data extraction

A customized data extraction form was created and used to collect information from the selected studies. All relevant details were systematically extracted and documented by two reviewers (E.J. and M.V.).

Data items

Data from the included studies was collected and organized into the following categories:

Risk of bias assessment

The quality of the studies included was assessed by two reviewers (E.J. and M.V.) using the Cochrane risk of bias tool - RoB 2.0 (https://methods.cochrane.org/). Any disagreements were resolved through discussion involving a third author (A.V.). The RoB 2.0 [12] tool comprises five domains: bias related to randomization, bias resulting from deviations in intended interventions, bias due to missing outcome data, bias in outcome assessment, and bias in the selection of the reported result.

The included studies were categorised as: “low risk” (plausible bias unlikely to seriously alter the results), “unclear risk” (plausible bias that raises some doubt about the results) or “high risk” (plausible bias that seriously weakens confidence in the results). The overall risk of bias was assessed, and included studies were categorized according to: low risk of bias (low risk of bias in all key domains); unclear risk of bias (unclear risk of bias in one or more key domains); high risk of bias (high risk of bias in one or more key domains).

Strategy for data synthesis

The canine distalization distance (mm) was selected as the primary outcome for the meta-analysis. Studies were included if they measured canine distalization at the same time intervals and reported the mean canine distalization distance and standard deviation for each study group. Upper canine retraction was defined as the linear distance of canine movement relative to the anteroposterior plane. Separate meta-analyses were performed to assess the effects of FLC on canine rotation measured as the angle between the canine long axis and the midsagittal plane and on molar anchorage loss, defined as the change in distance between the molar and the anteroposterior plane during canine distalization.

Statistical analysis

The statistical examination was done using the Review Manager (RevMan) version 5.4. (The Cochrane Collaboration; Oxford, UK). Numerical values were presented as mean and standard deviation (M [SD]). The level of P-value considered statistically significant at P < 0.05.

Agreement between the two reviewers in selecting abstracts and full-text studies was assessed using Cohen’s kappa coefficient (κ).

Assessment of heterogeneity

Study heterogeneity was assessed using Cochran’s Q and I² tests. The I² test was used to determine the degree of heterogeneity among studies, with ɑ = 0.1. Based on the guidelines by Higgins et al. [13], I² values were interpreted as follows: 0 to 40% indicated negligible heterogeneity, 30 to 60% moderate, 50 to 90% substantial, and 75 to 100% considerable heterogeneity. The effect size was evaluated by calculating the odds ratio and 95% confidence intervals. The effect size was estimated using a random-effects model, and the studies were pooled using the inverse variance weighing method. Publication bias was not assessed.

Study selection

The initial search yielded 583 articles (Figure 1). After the removal of duplicates (n = 149), 434 unique abstracts were screened based on their titles and abstracts. Of these, 426 publications were excluded for not meeting the inclusion criteria, leaving 8 articles for full-text evaluation. Ultimately, 7 split-mouth studies were included in the qualitative analysis, and 4 were suitable for the quantitative analysis.

The agreement between the two reviewers (E.J. and M.V.) in selecting abstracts was very high, measured at κ = 0.95.

Exclusion of studies

One article was excluded for the following reason: 1 patient-centered study [14].

Study characteristics

Table 2 and 3 provide an overview of the attributes of the studies that were incorporated. The studies included in the analysis were all split-mouth RCTs designs [7-9,15-18]. The origin of the studies was widespread across different countries, including Iraq [7], Iran [8,16], Syria [9,15], Egypt [17] and India [18]. Most studies incorporated a sample of male and female participants [7-9,15-17]. The age distribution of the sample was between 15 and 30 years. Age and sex were not comparable between groups.

Quality assessment of the included studies

Out of the total 7 studies, two RCTs were determined to have a low risk of bias [9,17], three studies were identified as having some concerns [8,15,16] and two studies were assessed as having a high risk of bias [7,18].

The primary factors contributing to the high risk and some concerns were related to the allocation sequence randomization and its concealment in the randomization procedure D1. None of the studies could uphold a double-blind study design because of the inherent character of the investigation. The evaluations of the subjects’ risk of bias are illustrated in Figure 2.

Results of individual studies

Maxillary canine retraction

Jaber et al. [15] reported statistically significant difference in the rate of canine retraction between the experimental and control groups during the baseline to first-week interval (P < 0.001), and the movement velocity on the experimental side was approximately 2.5 times greater than that of the control. Significant differences were observed between the two groups at subsequent intervals (weeks 1 to 2 and 2 to 4), with the experimental group demonstrating a retraction velocity approximately 1.8 times faster than the control (P < 0.001). Similarly, Salman et al. [7], Alfawal et al. [9] and Toodehzaeim et al. [16], reported that upper canine retraction was significantly greater on the experimental side (FLC) than on the control side (P < 0.05, P < 0.001, P < 0.05, respectively) (Table 2 and 3).

In contrast, Mahmoudzadeh et al. [8] and Bakr et al. [17] found no statistically significant differences in canine retraction between the FLC and control groups at the one month time point (P > 0.05, P = 0.19). At two months post-treatment, Alfawal et al. [9], Jaber et al. [15] and Toodehzaeim et al. [16] reported a statistically significant increase in the canine retraction rate in favour of the FLC group compared to the control group (P < 0.05, P < 0.001, P < 0.05). Conversely, Bakr et al. [17] reported no significant difference in canine retraction between the laser and control groups at the same time point (P = 0.66).

By the three month mark, Alfawal et al. [9], Jaber et al. [15], Toodehzaeim et al. [16] and Bakr et al. [17] concluded that there were no statistically significant differences in canine retraction distance between the FLC and control groups (P > 0.05, P = 0.427, P = 0.29, P = 0.16, respectively). Furthermore, Toodehzaeim et al. [16] and Alfawal et al. [9] extended these findings by reporting no significant difference at the four month follow-up (P = 0.29, P > 0.05).

In terms of the duration required for complete canine distalization, Chauhan et al. [18] found that the mean (SD) period of complete distalization was 4.9 (SD 0.57) months on the laser side and 5.9 (SD 0.61) months on the control side. Complete distalization took significantly longer on the control side than on the laser side (P < 0.001). Similarly, Alfawal et al. [9] reported significantly shorter duration of canine retraction on the experimental side compared with the control side, with a mean difference of 1.05 months (P ≤ 0.001).

Maxillary canine rotation angle

Alfawal et al. [9], Toodehzaeim et al. [16] and Bakr et al. [17] reported no statistically significant differences in canine rotation between the FLC and control groups one month after treatment (P = 0.17, P = 0.29, P = 0.51, respectively). In contrast, Mahmoudzadeh et al. [8] found a statistically significant difference in the angle index between the FLC and control groups at the one month mark, with a mean difference of -3.12 (SD 1.34) and a P-value of 0.02 compared to baseline. Furthermore, Alfawal et al. [9], Toodehzaeim et al. [16] and Bakr et al. [17] concluded that there were no statistically significant differences in canine rotation between the FLC and control groups at two and three months post-treatment (P = 0.544 and P = 0.517, P = 0.39 and P = 0.39, P = 0.65 and P = 0.44, respectively). Additionally, Alfawal et al. [9] and Toodehzaeim et al. [16] extended these findings by reporting no statistically significant difference at the four month mark (P = 0.316; P = 0.67).

Maxillary molar anchorage loss

Mahmoudzadeh et al. [8], Alfawal et al. [9], Toodehzaeim et al. [16] and Bakr et al. [17] concluded that there was no statistically significant difference in molar anchorage loss between the FLC and control groups one month after treatment (P = 0.891, P > 0.05, P = 0.76, P = 0.24, respectively). Furthermore, there were no significant difference of two months post-treatment [8,9,16,17]. Conversely, Bakr et al. [17] observed that, three months after treatment, the control group exhibited a statistically significantly greater loss of anchorage in the upper arches compared to the FLC group, with a mean difference of 0.3 mm (P = 0.023). However, Alfawal et al. [9] and Toodehzaeim et al. [16] reported no significant difference at the three month mark (P > 0.05, P = 0.65). Additionally, Alfawal et al. [9] and Toodehzaeim et al. [16] extended these findings by reporting no significant difference at the four month mark (P > 0.05, P = 0.86).

Meta-analysis

Certain studies were excluded from meta-analysis based on predefined criteria - one study with incompatible measurement method [15], and two studies due to methodological heterogeneity that precluded quantitative synthesis [7,18].

Canine retraction rate

Four split-mouth RCTs involving 55 patients met the inclusion criteria for the meta-analysis [8,9,16,17]. Two of the studies were assessed as having a low risk of bias [9,17], while the remaining two were judged to have some concerns regarding risk of bias [8,16].

A random-effects model was employed to analyse the canine retraction rate during the first, second and third months. While a fixed-effects model was applied for the fourth month.

In the first month, four studies [8,9,16,17] reported that FLC significantly accelerated canine distalization (55 patients; mean difference [MD] = 0.83; 95% confidence interval [CI] = 0.3 to 1.35; P = 0.002). However, substantial heterogeneity was observed among the studies (I² = 97%, P < 0.00001) (Figure 3).

During the second month, three studies [9,16,17] indicated a significantly higher rate of canine distalization in the intervention group (43 patients; MD = 0.44; 95% CI = 0.09 to 0.79; P = 0.01), with considerable heterogeneity (I² = 77%, P = 0.03) (Figure 4).

In the third month, three studies [9,16,17] found no statistically significant difference between the groups (43 patients; MD = 0.03; 95% CI = -0.18 to 0.24; P = 0.79), with moderate heterogeneity noted (I² = 52%, P = 0.12) (Figure 5).

In the fourth month, two studies [9,16] also showed no statistically significant difference between the groups (29 patients; MD = -0.04; 95% CI = -0.13 to 0.05; P = 0.37), and low heterogeneity was observed (I² = 3%, P = 0.31) (Figure 6).

Canine rotation

Three split-mouth RCTs with a total of 43 patients were included in the meta-analysis on posterior anchorage loss [8,9,17]. Two of the studies were assessed as having a low risk of bias [9,17], whereas the third presented some concerns [8,16].

An analysis of canine rotation at the one month mark was conducted using a random-effects model.

No statistically significant difference was found between the intervention and control groups (43 patients; MD = 1.2; 95% CI = -1.03 to 3.42; P = 0.29). However, significant heterogeneity was observed among the studies (I² = 87%, P < 0.0001) (Figure 7).

Molar anchorage loss

Three split-mouth RCTs involving 43 patients met the inclusion criteria for the canine rotation meta-analysis [8,9,17]. A low risk of bias was identified in two of the trials [9,17], whereas some concerns were noted in the remaining one [8].

A fixed-effects model was used to analyse molar anchorage loss after one month.

In the FLC group, molar anchorage loss was significantly lower than in the control group (43 patients; MD = -0.1, 95% CI = -0.19 to -0.01; P = 0.03). Heterogeneity among studies was negligible (I² = 0%, P = 0.91) (Figure 8).

Summary of evidence

The present review reduced variability in biomechanics and tooth type, by limiting inclusion to split-mouth RCTs in canine retraction [7-9,15-18]. Salman et al. [7] in 2014 presented the very first human study on laser-assisted flapless corticotomy, assessing its effectiveness in accelerating tooth movement and its impact on tooth vitality and surrounding structures. The results supported their hypothesis: canines on the laser side moved 67% of the total retraction distance, compared to only 33% on the control side. The effectiveness of this innovative surgical technique in accelerating orthodontic tooth movement has contributed to its wider adoption in clinical practice today. To the best of our knowledge, current systematic review and meta-analysis is the first to specifically investigate the effectiveness of high-energy laser therapy in combination with flapless corticotomy for accelerating canine retraction following first maxillary premolar extraction. The only previously published systematic review, by Shaadouh et al. [10], examined the application of HELT with flapless corticotomy for accelerating orthodontic tooth movement in general, without a specific focus on canine retraction. They reported significant acceleration during the first two months, but noted substantial heterogeneity in protocols, small sample sizes, and a decline in effect thereafter.

Our findings are parallel with those of Shaadouh et al. [10], that show significant acceleration of canine distalization in the first one to two months [7-9,15,16], followed by convergence with conventional mechanics by months three and four [9,15-17].

Animal studies support this time-limited effect. Studies on rabbits have demonstrated that erbium laser–assisted corticotomy can accelerate orthodontic tooth movement without compromising the healing of either soft or hard tissues [19].

This acceleration can be explained by the RAP phenomenon. Originally described by Frost [20] in 1983, the RAP refers to a cascade of biological events marked by elevated bone turnover in response to a noxious stimulus.

The RAP is considered the biological basis of orthodontic tooth movement [21,22], and surgical stimulation of the RAP has been shown to clinically enhance tooth movement. Various surgical approaches have been proposed to trigger this phenomenon, thereby reducing orthodontic treatment time [23-25]. The first technique based on the RAP included reflection of full‐arch, full‐thickness flaps, and extensive cortical penetrations using a rotary bur [22]. However, its invasiveness raised significant concerns for both clinicians and patients [26], prompting the emergence of less invasive alternatives such as FLC [19].

Laser-assisted corticotomy is minimally invasive method, designed to activate the RAP while reducing alveolar bone resistance to movement [20,23]. The targeted removal of small amounts of alveolar bone by laser energy elevates inflammatory markers and cytokine levels, stimulating osteoclast activity and thereby promoting bone remodeling and accelerated tooth movement [27,28]. According to Wilcko et al. [23,29], the RAP response begins within days after the surgical stimulus, reaches its maximum between four and eight weeks, and subsides within two to four months. This transient biological activity likely explains the acceleration observed during the first two months in the included studies, followed by a gradual reduction in retraction speed thereafter.

In addition to its potential for accelerating tooth movement, current evidence suggests that FLC does not negatively impact periodontal or pulpal health. Regarding pulp vitality, both Toodehzaeim et al. [16] and Bakr et al. [17] reported no statistically significant differences between FLC-treated and control canines at baseline or during follow-up periods of up to three months. Similarly, gingival health, as measured by the gingival index and width of attached gingiva, remained stable across intervention and control groups in studies by Mahmoudzadeh et al. [8] and Bakr et al. [17].

Potential adverse effects on tooth structure also appear minimal. Although Bakr et al. [17] reported evidence of root resorption, with both the control and FLC groups demonstrating a statistically significant reduction in canine root length. However, no statistically significant differences were found between the FLC and control sides in either the upper or lower canines at baseline or after three months of retraction in terms of root resorption

In terms of pain and discomfort, visual analogue scale (VAS) scores were comparable between groups in the studies by Toodehzaeim et al. [16] and Mahmoudzadeh et al. [8], with Jaber et al. [15] further reporting rapid pain reduction after the initial postoperative period.

Limitations

This study has certain limitations that need to be addressed. Firstly, the number of studies included in this systematic review and meta-analysis is the main limitation. A lack of large, high-quality studies investigating FLC in the acceleration of canine retraction rate is evident. Altogether, some of the included studies had a high or moderate risk of bias and relatively small sample sizes. Long-term follow-up of the response to these interventions was also lacking among the included studies. Additionally, further well-designed studies with larger sample sizes and standardized methodologies are necessary to validate its clinical effectiveness in enhancing orthodontic tooth movement.

Considering both qualitative and quantitative findings, flapless laser corticotomy may be regarded as a supplementary technique for accelerating canine orthodontic tooth movement, particularly during the first two months of treatment.

However, the effect appears to be transient, as several studies have reported no statistically significant differences in retraction distance between flapless laser corticotomy and control groups by the third and fourth months. Due to variability in the results across studies, it remains challenging to establish a definitive conclusion regarding the long-term efficacy of flapless laser corticotomy.