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| ORIGINAL ARTICLE |
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| Year : 2023 | Volume
: 12
| Issue : 1 | Page : 14 |
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Assessment of the effect of frequency of low-level laser therapy exposure at different intervals on orthodontic tooth movement – A systematic review and meta-analysis
Poornima R Jnaneshwar1, Keerthi Venkatesan2, Tsander Prince1, Vijayalakshmi Pethuraj1, Krishnaraj Rajaram1, Sachin Bhat1
1 Department of Orthodontics, SRM Dental College, Ramapuram, Tamil Nadu, India
2 Department of Orthodontics, Faculty of Dental Sciences, Sri Ramachandra Institute of Higher Education and Research, Porur, Chennai, Tamil Nadu, India
| Date of Submission | 23-Oct-2021 |
| Date of Decision | 29-Apr-2022 |
| Date of Acceptance | 20-Oct-2022 |
| Date of Web Publication | 18-Mar-2023 |
Correspondence Address:
Poornima R Jnaneshwar
Department of Orthodontics, SRM Dental College, Ramapuram - 89, Chennai, Tamil Nadu
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/jos.jos_182_21
OBJECTIVE: To assess the optimal intervals of exposure of low-level LASER therapy (LLLT) that would optimally accelerate orthodontic tooth movement. Second objective was to quantitatively analyze the difference in the time taken for alignment of anterior teeth with and without the application of LASER.
MATERIALS AND METHODS: PROSPERO database registry was done (CRD42020196472) and review was conducted based on PRISMA guidelines. A search was systematically conducted in five major electronic databases without restrictions up to June 2020 along with a hand search of selected journals. The quality of evidence was assessed using the Grading of Recommended Assessment, Development, and Evaluation tool, risk of bias using Cochrane risk of bias tool, and meta-analysis was carried out using RevMan 5.4 software.
RESULTS: Ten randomized controlled trials which met the inclusion criteria were evaluated and tabulated. A random-effects meta-analysis demonstrated that there is a statistically significant increase in the orthodontic tooth movement when patients were exposed to minimum of four intervals of LLLT in the first month, at P =0.03 by a standard mean difference of 0.46 mm with an overall heterogeneity of I2 = 0% at 95% confidence interval. There was a statistically highly significant reduction in the number of days taken for alignment of anterior teeth with the application of LASER (P < .00001).
CONCLUSION: Application of LLLT for minimum of four irradiations in the first month has yielded better results in accelerating orthodontic tooth movement than application of LLLT once a month.
Keywords: Accelerated orthodontic tooth movement, frequency of LLLT exposure, LASER, LLLT
How to cite this article:
Jnaneshwar PR, Venkatesan K, Prince T, Pethuraj V, Rajaram K, Bhat S. Assessment of the effect of frequency of low-level laser therapy exposure at different intervals on orthodontic tooth movement – A systematic review and meta-analysis. J Orthodont Sci 2023;12:14 |
How to cite this URL:
Jnaneshwar PR, Venkatesan K, Prince T, Pethuraj V, Rajaram K, Bhat S. Assessment of the effect of frequency of low-level laser therapy exposure at different intervals on orthodontic tooth movement – A systematic review and meta-analysis. J Orthodont Sci [serial online] 2023 [cited 2023 Oct 3];12:14. Available from: https://www.jorthodsci.org/text.asp?2023/12/1/14/371958 |
| Introduction | |  |
Orthodontic tooth movement (OTM) is defined as an adaptive biological response as the result of periodontal ligament remodeling during and after the application of forces which stimulates bone resorption on the compression site and bone deposition on the tension side, finally reorganizing the periodontal ligament.[1]
Numerous modalities have been used to accelerate OTM; few of them being mechanical vibration, corticotomy, piezocision, pharmacological adjutants, and low-level LASER therapy (LLLT).[2],[3] Literature shows that LLLT has been effective in inducing remodeling processes in both soft and hard tissue due to cellular absorption of LASER by the target tissue, which causes the intracellular signaling activation resulting in accelerated OTM and reduced orthodontic treatment duration.[4],[5],[6]
Although the use of LLLT to accelerate OTM has been assessed with regard to wavelength, an evaluation of the exposure at different time intervals has not been assessed qualitatively and quantitatively. There are studies proving the reduction in time duration taken for alignment of anterior teeth, yet the same has not been quantitatively analyzed. Therefore, the aim of this systematic review and meta-analysis is to evaluate the effect of variation in frequency of application of LASER on the rate of OTM and also to analyze the duration taken for alignment of anterior teeth in control and test group by means of a meta-analysis.
| Materials and Methods | | |
Protocol and registration
The study protocol for the systematic review was registered with PROSPERO (International Prospective Register of Systematic Reviews) REG NUMBER- CRD42020196472 and was carried out referring to the Cochrane Handbook for Systematic Reviews of Interventions.[7]
The methodology used in this systematic review was based on the PRISMA instructions, to identify the relevant article for review.[8]
A guiding question formulated was, “what is the effect of variation in the number of irradiation appointments of LLLT in accelerating OTM?”
Selection criteria
The studies which satisfied the following eligibility criteria were included in the systematic review:
- Participants: Orthodontic patients exposed to low-level LASER for the purpose of accelerating tooth movement.
- Intervention/exposure: LLLT during orthodontic mechanotherapy/space closure.
- Comparison: Similar group/quadrant without application of LASER.
- Outcome measures: Difference/acceleration in tooth movement with variation in exposure intervals of LLLT.
- Study design: Randomized control trial (RCT).
Exclusion criteria
- Nonrandomized trials.
- Animal studies.
- High-level LASER and light emitting diode.
- Articles, reviews, case reports, opinions, columns in publications, letters, abstracts, and pilot study.
- Study without adequate data.
- Any studies which used other interventions along with LLLT (e.g., LLLT after corticision).
Information source and search strategy
Based on PRISMA guidelines, a search was conducted in the following major five electronic databases: PubMed, Scopus, SciELO, Cochrane, and Google scholar using the strategy given in [Table 1]. Grey literature was sought from Greynet and Ovid. The search was conducted till June 2020, did not have any language restrictions, and unpublished data were not taken into consideration for the review.
Study selection
Initially, all the references were exported to Zotero Desktop 5.0.87 software, to track potential duplicate records. Subsequently, titles and abstracts were read in detail to exclude articles which were out of the scope of research. At this stage, literature reviews, case reports, and experimental surveys with animals were also excluded. Full-text analysis of articles, whose title and abstract did not present sufficient information, were downloaded and analyzed to decide their eligibility for inclusion. Full texts of all the selected articles were downloaded and the details were tabulated in a PRISMA flowchart [Figure 1].
Data extraction and synthesis
Data were independently collected by five reviewers and basic details about articles such as type of LASER, its characteristics, clinical findings, and outcome of study were done using a data collection form.[9],[10],[11],[12],[13],[14],[15],[16],[17],[18] Finally, all the data were compared for accuracy and any conflict was resolved through re-examination of the original study and discussion among all the reviewers until consensus and a study characteristics table was tabulated [Table 2].
Quality assessment
Quality assessment of the selected articles for a systematic review was performed using the Grading of Recommended Assessment, Development, and Evaluation tool[19] [Table 2].
Risk of bias in individual studies
Finalized articles were thoroughly evaluated for their quality and potential risk of bias based on an evaluation adopted from Cochrane risk-of-bias tool for randomized trial RoB-2 tool.[20]
To evaluate the overall risk of bias, the analysis of each criterion was combined or the final assessment was given [Table 3]. For each criterion, the low, unclear, or high risk of bias was awarded.
Summary measures and approach to synthesis
Random-effects meta-analysis of the mean difference in the rate of canine retraction during LLLT exposure at two different intervals was carried out using Review Manager (RevMan) version 5.4. Four randomized clinical trials were statistically evaluated separately with a subgroup analysis and significance established at P <.05.[13],[14],[17],[18] Results of the analyses are presented graphically with forest plot after comparison of the study design and methodology to evaluate the clinical heterogeneity of the studies [Figure 2]. | Figure 2: (Meta-analysis) Forest plot of orthodontic tooth movement in intermittent versus long-term interval exposure of LLLT
Click here to view |
Two randomized clinical trials were statistically analyzed, and significance established at P < .05.[9],[11] Results of the analyses are presented graphically with forest plot after study design and methodology heterogeneity were checked [Figure 3]. | Figure 3: (Meta-analysis) Forest plot of duration of time taken for anterior alignment using LLLT versus controls
Click here to view |
| Results | | |
Study selection and characteristics
The literature search done is given in [Table 1]. Of four electronic databases, a total of 268 articles were evaluated, from which 64 full-text articles were examined in detail. Finally, 10 studies that satisfied the eligibility criteria were taken for final reviewing and quality analysis; and four RCTs were selected for quantitative data extraction to assess the rate of canine retraction and two RCTs were selected for quantitative data extraction to analyze the reduction in duration of alignment of anterior teeth [Figure 1].
In this study, 10 experimental studies involving LLLT were evaluated and tabulated with different aspects like type of LASER used, their wavelength, power output, and point of irradiation and interval [Table 4].
Risk of bias within studies
Risk of bias for each study is presented in [Table 3]. Of the 10 studies, five studies were found to have low risk and five studies had moderate risk of bias.
| Results of Individual Studies and Meta-Analysis | | |
Of the 10 studies which were evaluated for evidence, eight studies showed accelerated tooth movement with LLLT [Table 2]; an increased frequency of application with many intervals of exposure showed reduced treatment time than the control group. Thus, the result showed that LLLT can be effectively used in accelerating the OTM and reduce the treatment time effectively.
Effects of LLLT on accelerated OTM were drawn based on the criteria for assessing study quality. While comparing the parameters of the LASER used in different studies, majority of the studies commonly used Ga-Al-As LASER in a continuous wave mode and with the wavelength ranging from 618 nm to 980 nm which is infrared in nature [Table 2].
LASER's power output between 20 and 150 mW gave a positive result, whereas anything lower or higher had no effect on tooth movement, which points that a very high-power output could be the reason for a negative outcome in the other two studies that showed insignificant OTM when exposed to LLLT.[12],[17]
As far as number of irradiation points are concerned majority of the studies used 8-10 irradiation points based on a root morphology, which shows that for effective acceleration the delivery of LASER needs to be distributed to many points rather than one. Hence, uniform LASER irradiation from all the sides showed better results than increasing the magnitude of the irradiation. Irradiation intervals also varied in different studies; studies with positive results had almost more than 10 exposure per month, whereas studies with 1-3 exposures failed to give positive results.[21],[22]
Four studies were included in quantitative analysis after considering the clinical homogeneity of the studies with respect to their methodology (i.e., wavelength in the range of 800-860 nm, RCT studies which had premolars extracted comparing the rate of canine retraction under LLLT exposure with a control group).[13],[14],[17],[18]
[Figure 2] shows a forest plot comparing the standard mean difference in the rate of canine retraction between two subgroups, intermittent frequency/weekly interval of LLLT exposure, and long-term frequency/monthly interval of LLLT exposure.
When comparing the two subgroups, there was a statistical significance of P =0.01 in the rate of tooth movement for the intermittent interval LLLT exposure subgroup which showed Standard Mean Difference (SMD) = 0.72 mm; 95% confidence interval (CI), I2 = 0% when compared to the monthly/long-term interval LLLT subgroup which showed a less statistical significance in the rate of tooth movement of P =0.53 at SMD = 0.19 mm, 95% CI, I2 = 0%. [Figure 2]
When considering the total overall effect in the rate of canine retraction, there is a statistically significant increase in the rate of canine retraction which favors intermittent exposure of LLLT (SMD = 0.46 mm; 95% CI; P = 0.03) and level of heterogeneity is low (I2 = 0%). [Figure 2]
Two studies were selected for quantitative assessment of time duration for alignment [Figure 3][9],[11] which shows the forest plot comparing the mean number of days taken for achieving alignment of anterior teeth with and without LASER application. Heterogeneity level was very low and the meta-analysis performed indicated a statistically highly significant reduction in the number of days taken for aligning anterior teeth in the test group (SMD = -25.58 days; 95% CI; P <.00001) and level of heterogeneity is I2 = 0%.
| Discussion | | |
Summary of evidence
Adult patients seeking orthodontic treatment warrant a reduction in duration of fixed mechanotherapy. Acceleration of OTM has been attempted by numerous methods and the most promising noninvasive is the application of LLLT.[2],[3] Several authors have evaluated the effect of LLLT on OTM but there is less clarity on the difference in rate of tooth movement with a varied interval of application of LASER, number of irradiation points necessary to achieve optimal acceleration in tooth movement.[9],[10],[11],[12],[13],[14],[15],[16],[17],[18] Hence, the aim of the systematic review was to quantitatively analyze the effect of variation in the frequency of application of LASER on the rate of OTM and analyze the difference in the time taken for alignment of anterior teeth.
Mechanism of bone remodeling brought about by photobiomodulation are listed below[23],[24],[25]:
- LASER light energy increases the metabolic activity and bone turnover by increasing the amount of ATP (Adenosine Triphosphate) in osteogenic cells.
- Sensitivity of osteoblast and osteoclast to low intensity LASER light is used to augment cell proliferation and function.
- Fujita et al.[25] reported that LLLT increases the rate of tooth movement by enhancing the expression of RANK (receptor activator for nuclear factor kappa) and RANKL (Receptor activator for nuclear factor kappa ligand).
Systematic data search yielded two RCTs that had studied the duration taken for alignment of lower anterior teeth with and without the application of low-level LASER in patients who did not require premolar extraction for orthodontic alignment.[9],[10] Both the studies reported a statistically significant reduction in duration required for alignment of teeth in the test group.
Alsayed Hasan et al.[11] studied the duration taken for alignment of anterior teeth with and without the application of LLLT.[11] LASER was applied at 1, 3, 7, and 14 days, followed by application every 15 days till alignment and leveling were completed. They found that there was a 26% reduction in the overall treatment time in the test group when compared to control.
Quantitative evaluation of the duration taken for achieving alignment and leveling was done using data from two studies.[9],[11] It was found that there was a highly significant reduction in the number of days required to achieve alignment and leveling in the test group [Figure 3].
LASER irradiation in most of the studies was done on specific regions around the tooth that was intended to move rapidly, called irradiation points. Point irradiation varied for different studies from as low as 4 points to maximum of 10 points. A study by Caccianiga et al.[10] divided oral cavity into segments instead of specific points. Studies by Nahas et al.[9] and Ekizer et al.[15] used light emitting diode device which did not have point irradiation or segments, instead just exposure of light from buccal aspect of the teeth. Irradiation points were specifically used in researches that studied the rate of canine retraction in extraction cases; Üretürk et al.[17] chose 10 points in their study, of which five were on buccal and five were on a palatal aspect. Studies with a greater number of irradiation points claimed an increased acceleration of OTM.[11],[13],[16] By increasing the number of point irradiation with small time interval of 10-15 seconds, adequate LASER energy is delivered to the cells and also reduces the chance of heat damage to surrounding tissues.
Frequency of interval between LASER exposure usually was carried out once in 3-4 weeks in majority of the studies; such exposure is common in patients requiring an increase in rate of tooth movement.[10],[11],[12],[17] After initial leveling and alignment application of LLLT once in 3 weeks showed a considerable decrease in the time period needed for space closure.[10],[11],[14],[17] Research by Nahas et al.[9] and Caccianiga et al.[10] showed 10 exposures per month in a nonextraction case that had significant changes in accelerated OTM in comparison to study where lesser duration of exposure was present.[15]
Four RCTs qualified for quantitative evaluation of the difference in the rate of OTM when LASER was applied at different time intervals because LASER used was in a narrow range of LASER (800-860 nm). When the frequency of LASER application was compared, two studies have applied LASER in intermittent manner: 0, 3, 7, 14 days, and every 15th day till canine retraction was completed and 0, 3, 7, 14, 21, 30, 33, 37, 60, 63 days, and 67th day.[14],[17] Alternatively, LASER was applied every four weeks by Mistry et al.[18] and first three days followed by once a month for 4 months by Limpanichkul et al.[13]
Meta-analysis was done by subgrouping the studies into intermittent interval and long interval LASER exposure studies to compare their effects with control [Figure 2]. It was found that intermittent exposure to LASER of minimum four applications in the first month produced a statistically significant increase in rate of tooth movement when compared to control (P =0.01), in contrast to the long interval studies in which there was no difference between the two groups (P =0.53) in the rate of canine retraction [Figure 2]. Test for overall effect yielded a statistically significant value of P =.03 which denotes that there is a statistically significant increase in the rate of OTM when LLLT was applied at intermittent intervals than long intervals of once a month.
Doshi-Mehta et al.[14] studied the rate of canine retraction in 20 orthodontic patients with application of LASER and they found that there was a statistically significant increase in the rate of OTM of 56% at the test site when compared to control at the end of 3 months. This positive effect could be due to the low intensity of the LASER used with a power output of 0.25 mW, but as per the result of the meta-analysis performed, it can be inferred that there is a definitive effect due to the variation in the number of applications of LASER in the first month.
When the studies of Limpanichkul et al. and Mistry et al. were compared, it was found that both the studies used similar energy intensity of LASER but there was a variation in the frequency of application of LASER when compared to Doshi-Mehtha et al. and Uretruk et al.[13],[14],[17],[18] In the intermittent group, there is minimum application of four times in the first month 0, 3, 7, and 14 days in the first month and 0, 3, 7, 14, 21, and 30 days, respectively.[14],[17] In the long interval group, Mistry et al. have applied LASER on 0, 28, and 56 days and Limpanichkul et al. have applied on the first three days which was repeated in the subsequent months.[13],[18] Therefore, it is clear from the results of meta-analysis that there is a definitive positive effect on the rate of OTM when LASER irradiation was given for minimum four applications in the first month.
There is possibly an increased initial impetus to OTM provided by the periodically spaced LASER application in the first month of canine retraction by Doshi-Mehta et al. and Uretruk et al.[14],[17] The biological mechanism behind this initial impetus is an area for future research.
Limitations
Parameters of LASER used like optimal wavelength, energy intensity, effects of change in the number of irradiation points, time spacing between LASER applications, etc., need more clarity and are areas of future research.
| Conclusion | | |
LLLT can be suggested as an adjuvant promising procedure with potential to accelerate OTM considering the following points of the study:
- Meta-analysis shows that frequent application of LLLT for a minimum of four times in the first month of canine retraction produced a statistically significant increase in rate of OTM.
- There was a statistically significant reduction in the duration taken for alignment of anterior teeth with LLLT.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4]
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