Effects of the pulse frequency of low-level laser therapy on the tooth movement speed of rat molars

Clinical and preclinical evidence on the bioeffects and movement-related implications of photobiomodulation in the orthodontic tooth movement: A systematic review

Photobiomodulation (PBM) has been demonstrated as a non-invasive and painless technique with great potential to accelerate orthodontic tooth movement (OTM). However, there is a great inconsistency among PBM protocols and reported outcomes, probably due to the poor translatability of preclinical knowledge into early clinical practice. Hence, this review aims to fill this gap by establishing the state-of-the-art on both preclinical and clinical applications of PBM, and by comprehensively discussing the most suitable stimulation protocols described in the literature. This review was conducted according to PRISMA guidelines. A bibliographic search was carried out in the PubMed, Scopus and Cochrane databases using a combination of keywords. Only studies written in English were eligible and no time limit was applied. A total of 69 studies were selected for this review. The revised literature describes that PBM can effectively reduce orthodontic treatment time and produce analgesic and anti-inflammatory effects. We found that PBM of 640 ± 25, 830 ± 20 and 960 ± 20 nm, delivered at a minimum energy density per irradiation point of 5 J/cm2 daily or every other day sessions is robustly associated with increased tooth movement rate. Pain relief seems to be achieved with lower irradiation doses compared to those required for OTM acceleration. For the first time, the bioeffects induced by PBM for the acceleration of OTM are comprehensively discussed from a translational point of view. Collectively, the evidence from preclinical and clinical trials supports the use of PBM as a coadjuvant in orthodontics for enhancing tooth movement and managing treatment-associated discomfort. Overall, the revised studies indicate that optimal PBM parameters to stimulate tissue remodelling are wavelengths of 830 ± 20 nm and energy densities of 5-70 J/cm2 applied daily or every other day can maximize the OTM rate, while lower doses (up to 16 J/cm2 per session) delivered in non-consecutive days seem to be optimal for inducing analgesic effects. Future research should focus on optimizing laser parameters and treatment protocols customized for tooth and movement type. By fine-tuning laser parameters, clinicians can potentially reduce treatment times, improve patient comfort and achieve more predictable outcomes, making orthodontic care more efficient and patient-friendly, thus consolidating PBM usage in orthodontics.

Evaluation of the effects of diode laser application on experimental orthodontic tooth movements in rats. Histopathological analysis

Purpose:

To evaluate the effect of diode laser use on experimental orthodontic tooth movements.

Methods:

Thirty Rattus norvegicus albinus Wistar were divided into three equal groups (n = 10), two experimentals and one control. Applying 20 g orthodontic force were attached to the maxillary incisors of the rats in all groups. Low dose laser was applied to the surrounding tissues of the maxillary incisors of the rats in the experimental groups. Two exposure times for laser irradiation were used for seven days: t = 12 min (energy dose = 72 J) and t = 9 min (energy dose = 54 J) by a 0.1 W DEKA brand diode laser with wavelength of 980 nm.

Results:

Osteoclastic activation increased in the 72 J group when compared to control group and decreased in comparison to the 54 J group. Osteoblastic activation was decreased in the 72 J group when compared to the control group and increased in comparison to the 54 J group.

Conclusions:

Applying 54 J laser energy has been found effective to accelerate the orthodontic tooth movement.

The Effect of Low-Level Laser Therapy on the Acceleration of Orthodontic Tooth Movement

In clinical practice, low-level laser therapy (LLLT) is widely used. The main aim of this review is to assess the effectiveness of LLLT in accelerating tooth movement in human subjects. The PRISMA checklist was utilized as a guideline to carry out this systematic review. The electronic databases were searched from Google Scholar (2014-2018) and PubMed, and comprehensive research on this topic was also manually conducted. Therefore, 77 articles randomized clinical trials (RCTs) or controlled clinical trials (CCTs) were selected. After screening studies, consequently, eleven trials met the inclusion criteria. Eight out of 11 studies showed LLLT has a significant impact on the acceleration of orthodontic tooth movement, and there was no statistically significant difference in the rate of tooth movement between the laser group and the control group in the two remaining studies. Furthermore, five out of 11 articles showed that LLLT has no adverse effects. Although we have some degree of understanding from a cellular point of view to LLLT effects, we still do not know whether these cellular level changes have any effect on the clinical acceleration of orthodontic tooth movement. The results are inconclusive and cannot be generalized to the public community; therefore, well-structured studies are required.

Infrared Light-Emitting Diode (LED) Effects on Orthodontic Tooth Movement

The present study aimed to analyze the effect of LED phototherapy on the presence of hyalinization and root resorption during orthodontic tooth movement (OTM) in rats and to measure the amount of tooth movement. Eighty rats were allocated into two groups: LED and control (CON), where the LED rats were irradiated with infrared LED (850 nm, 30 mW) for 5 min during the first five days of OTM and where controls were not irradiated. Both groups were subdivided into four subgroups (n=10) according to the date of euthanasia (4, 7, 14 and 21 days). Five out of ten LED21 and five of ten CON21 rats were submitted to micro-computed tomography (μCT); μCT scans were taken on days 0, 7, 14 and 21. For histological study, maxillae were processed to light microscopy using Hematoxylin-Eosin (HE) and Tartrate-Resistant Acid Phosphatase (TRAP) histochemistry. The amount of tooth movement did not differ between LED and CON. Hyalinization was observed at the pressure areas in both groups, and it did not show a statistically significant difference between the groups. Root resorption was also observed in both groups after 7 days and it did not represent any differences between the two groups. LED phototherapy was not able to increase the amount of OTM. Similar characteristics of hyalinization and root resorption were observed in both groups.

Phototherapy is unable to exert beneficial effects on orthodontic tooth movement in rat molars

OBJECTIVES

To investigate the effects of irradiation lasers and light-emitting diode (LED) light on root resorption in rat molars during orthodontic tooth movement (OTM).

MATERIALS AND METHODS

Twenty-one 12-week-old Wistar male rats were divided into three groups: OTM only (control [CG]), OTM and LED irradiation (DG), and OTM and low laser irradiation therapy (LG). The distance between the first and second molars was used to evaluate the amount of tooth movement. The mesial surfaces of the distopalatal roots were analyzed by scanning electron microscopy, and the area of the resorption was calculated.

RESULTS

Statistical analysis showed a decreased amount of tooth movement in the exposed DG or LG compared with CG, which was statistically significant (P = .031 and P = .004, respectively). However, when the DG and LG groups were compared, no statistically significant differences were found (P = .504). The root resorption areas were similar between CG and DG. However, statistically significant differences were found between LG and CG (P = .014) and LG and DG (P = .038).

CONCLUSIONS

Phototherapy did not enhance tooth movement, while infrared laser irradiation did increase root resorption.

Effects of Different Parameters of Diode Laser on Acceleration of Orthodontic Tooth Movement and Its Effect on Relapse: An Experimental Animal Study

AIM

Recent studies have demonstrated that low-level laser therapy (LLLT) can accelerate orthodontic tooth movement. However, there is still controversy about the optimum parameters that can cause acceleration. The present study was designed to examine two different doses of LLLT in the acceleration of orthodontic tooth movement and their effect on relapse.

METHODS

An orthodontic appliance was designed to induce tooth movement on lower incisors of rabbits. The in-al-as diode laser was used to radiate different groups of rabbits according to a specific protocol. The amount of tooth movement was measured for 21 days, and then the orthodontic appliance was removed, and the relapse was measured till day 28.

RESULTS

The amount of tooth movement was significantly greater in the group with irradiation of low dose in comparison with the high dose group and the control group. The relapse was greatest in the group of low dose irradiation and least in the control group.

CONCLUSION

The findings suggest that LLLT with a low dose accelerate the orthodontic tooth movement while LLLT with a high dose was not able to have the same effect. LLLT had a reverse effect on relapse tendency; an increase in the relapse tendency was seen with low dose irradiation.

Effect of Low-level Laser Therapy on Orthodontic Movement of Human Canine: a Systematic Review and Meta-analysis of Randomized Clinical Trials

Background:

Low-level Laser Therapy (LLLT) is a noninvasive method of accelerating tooth movement. Herein, this meta-analysis was aimed to assess the efficacy of LLLT in accelerating orthodontic tooth movement of human maxilla or mandible canine.

Methods:

Five databases including Web of Science, Scopus, PubMed, ScienceDirect, and Cochrane Library were used for searching the studies. Studies on LLLT for orthodontic tooth movement of human canine, randomized clinical trial (RCT), and outcome variables such as distance or speed of the tooth movement in treatment duration were considered for the final analysis. RevMan 5.3 was used for calculating the mean difference (MD) and 95% confidence intervals (CIs) on random-effects model.

Results:

Out of 275 studies retrieved from five databases, six RCTs were included and analyzed in this meta-analysis. The results showed that the orthodontic movement of canine was statistically increased in the LLLT group compared with the control group in 21 days (MD: 0.74; 95%CI: 0.17, 1.31; P = 0.01), one month (MD: 0.40; 95%CI: 0.10, 0.69; P = 0.008), 1.5 months (MD: 0.72; 95%CI: 0.51, 0.93; P < 00001), two months (MD: 0.84; 95%CI: 0.23, 1.44; P = 0.006) three months (MD: 0.92; 95%CI: 0.06, 1.78; P = 0.04), and 4.5 months (MD: 1.53; 95%CI: 0.92, 2.14; P < 0.00001).

Conclusion:

The LLLT can speed up the rate of tooth movement of human canine and consequently decrease the treatment time. LLLT represents a proper adjuvant therapy for fixed orthodontic treatment.

Effect of Pulsed Wave Low-Level Laser Therapy on Tibial Complete Osteotomy Model of Fracture Healing With an Intramedullary Fixation

Background:

Fractures pose a major worldwide challenge to public health, causing tremendous disability for the society and families. According to recent studies, many in vivo and in vitro experiments have shown the positive effects of PW LLLT on osseous tissue.

Objectives:

The aim of this study was to evaluate the outcome of infrared pulsed wave low-level laser therapy (PW LLLT) on the fracture healing process in a complete tibial osteotomy in a rat model, which was stabilized by an intramedullary pin.

Materials and Methods:

This experimental study was conducted at Shahid Beheshti University of Medical Sciences in Tehran, Iran. We performed complete tibial osteotomies in the right tibias for the population of 15 female rats. The rats were divided randomly into three different groups: I) Control rats with untreated bone defects; II) Rats irradiated by a 0.972 J/cm² PW LLLT; and III) Rats irradiated by a 1.5 J/cm² PW LLLT. The right tibias were collected six weeks following the surgery and a three-point bending test was performed to gather results. Immediately after biomechanical examination, the fractured bones were prepared for histological examinations. Slides were examined using stereological method.

Results:

PW LLLT significantly caused an increase in maximum force (N) of biomechanical repair properties for osteotomized tibias in the first and second laser groups (30.0 ± 15.9 and 32.4 ± 13.8 respectively) compared to the control group (8.6 ± 4.5) LSD test, P = 0.019, P = 0.011 respectively). There was a significant increase in the osteoblast count of the first and second laser groups (0.53 ± 0.06, 0.41 ± 0.06 respectively) compared to control group (0.31 ± 0.04) (LSD test, P = 0001, P = 0.007 respectively).

Conclusions:

This study confirmed the efficacy of PW LLLT on biomechanical strength, trabecular bone volume, callus volume, and osteoblast number of repairing callus in a complete tibial osteotomy animal model at a relatively late stage of the bone healing process.

Evaluation of the effects of LLLT on biomechanical properties of tibial diaphysis in two rat models of experimental osteoporosis by a three point bending test

Osteoporosis (OP) is a disease which causes bone loss and fractures, leading to severe pain and deformity. This study has aimed to assess the effects of pulsed wave low-level laser therapy (PW LLLT) on cortical bone in two experimental models of OP in rats. There were four ovariectomized (OVX-d) groups and four dexamethasone-treated groups. The healthy group were considered for baseline evaluations. At 14 weeks following ovariectomy, the OVX-d rats were further subdivided into the following: control rats with OP, OVX-d rats that received alendronate (1 mg/kg), OVX-d rats treated with LLLT, and OVX-d rats treated with alendronate and LLLT. The remaining rats received dexamethasone for 5 weeks and were divided into four groups: control, alendronate-treated rats (1 mg/kg), laser-treated rats, and laser-treated rats with concomitant administration of alendronate. The rats received alendronate for 30 days. LLLT (890 nm, 80 Hz, 0.972 J/cm(2)) was performed on the tibias three times per week for 8 weeks. After 8 weeks, tibias were extracted and submitted to a three-point bending test. PW LLLT did not increase the biomechanical parameters of osteoporotic bones compared to controls and healthy rats. PW LLLT associated with alendronate treatment significantly increased stress high load in OVX-d rats compared to the healthy group. PW LLLT at the current study parameters failed to cause beneficial biomechanical effects in the examined osteoporotic cortical bones. PW LLLT associated with alendronate treatment produced a more remarkable effect on bone strength in the ovariectomized induced OP rat model.

The effect of light-emitting diode and laser on mandibular growth in rats

OBJECTIVE

To evaluate the effect of a light-emitting diode (LED) and/or low-level laser (LLL) with or without the use of anterior bite jumping appliances (also known as functional appliances [FAs]) on mandibular growth in rats.

MATERIALS AND METHODS

Thirty-six 8-week-old male Sprague-Dawley rats weighing 200 g were obtained from Charles River Canada (St. Constant, QC, Canada) and were divided into six groups of six animals each. Groups were as follows: group 1: LLL; group 2: LLL + FA; group 3: LED; group 4: LED + FA; group 5: FA; and group 6: control (no treatment). Mandibular growth was evaluated by histomorphometric and micro computed tomographic (microCT) analyses.

RESULTS

The LED and LED + FA groups showed an increase in all condylar tissue parameters compared with other groups.

CONCLUSION

The LED-treated groups showed more mandibular growth stimulation compared with the laser groups.