The effect of dosage on the efficiency of LLLT in new bone formation at the expanded suture in rats

Osteoblastic differentiation and changes in the redox state in pulp stem cells by laser treatment

The aim of this study was to determine the effect of low-level laser therapy (LLLT) on cell proliferation, mitochondrial membrane potential changes (∆Ψm), reactive oxygen species (ROS), and osteoblast differentiation of human dental pulp stem cells (hDPSCs). These cells were irradiated with 660- and 940-nm lasers for 5 s, 50 s, and 180 s. Cell proliferation was assessed using the resazurin assay, cell differentiation by RUNX2 and BMP2 expression, and the presence of calcification nodules using alizarin-red S staining. ROS was determined by the dichlorofluorescein-diacetate technique and changes in ∆Ψm by the tetramethylrhodamine-ester assay. Data were analyzed by a Student's t-test and Mann-Whitney U test. The 940-nm wavelength for 5 and 50 s increased proliferation at 4 days postirradiation. After 8 days, a significant decrease in proliferation was observed in all groups. Calcification nodules were evident in all groups, with a greater staining intensity in cells treated with a 940-nm laser for 50 s, an effect that correlated with increased RUNX2 and BMP2 expression. ROS production and Δψm increased independently of irradiation time. In conclusion, photobiomodulation (PBM) with LLLT induced morphological changes and reduced cell proliferation rate, which was associated with osteoblastic differentiation and increased ROS and Δψm, independent of wavelength and time.

Is photobiomodulation effective during maxillary expansion? A systematic review and meta-analysis

We performed a systematic review on literature associated with meta-analyses to elucidate whether (I) low-level laser therapy (C) compared to placebo accelerates (O) bone neoformation in the region of the midpalatal suture in (P) patients undergoing transverse maxillary expansion. Two reviewers blindly performed targeted searches using the selection criteria (PICOS) in seven major databases and three grey literature databases, employing specific terms and their entrenchments. The RevMan® software (Review Manager, version 5.3, Cochrane Collaboration) was used to adapt the RoB summary illustration to the Cochrane 2.0 tool questions. Meta-analysis was performed using standardized mean difference (SMD) and Cohen's d calculation on random effects, tests for heterogeneity (I² ) and publication bias (Egger and Begg), and one-of-out sensitivity analysis. GRADE (Grading of Recommendations Assessment, Development and Evaluation) was used for evidence quality analysis. Among the five studies included in the qualitative synthesis, three were included in the meta-analysis. All analysed studies were prospective randomized clinical trials. The risk of bias was such that the Egger (P = .1991) and Begg (P = .024) tests showed no significant risk of publication bias. The meta-analysis showed high heterogeneity (I²  = 81%, P < .00001), and 3 months after the operation, there was no significant difference between the photobiomodulation (PBMT) group and control group (P = .850) or between the subgroups of the periods evaluated after 3 months (P = 0.490). GRADE showed an SMD of 0.62. Photobiomodulation as an adjuvant therapy in patients undergoing transverse maxillary expansion has few benefits and is limited in shape, as it contributes to bone healing in the midpalatal suture region after a period of 3 months.

Reducing relapse and accelerating osteogenesis in rapid maxillary expansion using an injectable mesoporous bioactive glass/fibrin glue composite hydrogel

Rapid maxillary expansion (RME), as a common treatment for craniomaxillofacial deformity, faces the challenge of high relapse rates and unsatisfactory therapeutic effects. In this study, a standardized Sprague-Dawley (SD) rat RME model was first established with a modified expander as well as retainer design and optimized anterior maxillary expanding force of 100 g which exerted the most synchronized mobility of mid-palatal suture and incisors. Via the standardized model, the high relapse rate was proven to be attributed to insufficient osteogenesis in expanded suture, requiring long-term retainer wearing in clinical situations. To reduce the relapse rate, mesoporous bioactive glass/fibrin glue (MBG/FG) composite hydrogels were developed for an in situ minimal invasive injection that enhance osteogenesis in the expanded palate. The component of 1 wt% MBG was adopted for enhanced mechanical strength, matched degradation rate and ion dissolution, excellent in vitro biocompatibility and osteoinductivity. Effects of 1%MBG/FG composite hydrogel on osteogenesis in expanded mid-palatal sutures with/without retention were evaluated in the standardized model. The results demonstrated that injection of 1%MBG/FG composite hydrogel significantly promoted bone formation within the expanded mid-palatal suture, inhibited osteoclastogenesis and benefited the balance of bone remodeling towards osteogenesis. Combination of retainer and injectable biomaterial was demonstrated as a promising treatment to reduce relapse rate and enhance osteogenesis after RME. The model establishment and the composite hydrogel development in this article might provide new insight to other craniomaxillofacial deformity treatment and design of bone-repairing biomaterials with higher regenerative efficiency.

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A standardized rat RME model was established with optimized parameters.

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Sufficient osteogenesis was the prerequisite of reducing relapse ratio.

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Design of an injectable MBG/FG composite hydrogel for osteogenic enhancement.

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Combinatory treatment of injection and retention was developed for relapse reduction.

Effects of teriparatide on bone formation in rats with experimentally induced premaxillary expansion

Objective:

This study aimed to evaluate the effects of systemic teriparatide on sutural bone formation after premaxillary suture expansion in rats.

Material and Methods:

Twenty Wistar male rats (8-10 weeks old) were randomly divided into two groups, namely, control (C, n=10) and teriparatide (T, n=10). An expansion force was applied to the maxillary incisors using helical spring for a seven-day expansion period, for both groups. On the eighth day, the rats were kept for a seven-day consolidation period, and then 60 µg/kg teriparatide (once a day) was administered to group T subcutaneously for seven days. Then, all the rats were sacrificed, and histological sections were stained with hemotoxylin-eosin for examination. Anti-osteonectin, anti-osteocalcin, anti-Vascular endothelial growth factor (VEGF) and anti-transforming growth factor beta (TGF-β) were evaluated by immunohistochemical analysis in the midpalatal suture area.

Results:

Histologically, the newly formed bone tissue was observed to be larger in group T than in group C. The number of immunoreactive osteoblasts for osteonectin, osteocalcin and VEGF antibodies was significantly higher in group T than in group C (p = 0.0001). The TGF-β antibody showed a mild reaction in group T, but did not reach significance in comparison with group C (p ˃ 0.05).

Conclusion:

Systemic teriparatide application following the premaxillary expansion of the suture area may stimulate bone formation and add to the consolidation of the expansion in rats by regulating osteonectin, osteocalcin and VEGF.

Response of Gli1+ Suture Stem Cells to Mechanical Force Upon Suture Expansion

Normal development of craniofacial sutures is crucial for cranial and facial growth in all three dimensions. These sutures provide a unique niche for suture stem cells (SuSCs), which are indispensable for homeostasis, damage repair, as well as stress balance. Expansion appliances are now routinely used to treat underdevelopment of the skull and maxilla, stimulating the craniofacial sutures through distraction osteogenesis. However, various treatment challenges exist due to a lack of full understanding of the mechanism through which mechanical forces stimulate suture and bone remodeling. To address this issue, we first identified crucial steps in the cycle of suture and bone remodeling based on the established standard suture expansion model. Observed spatiotemporal morphological changes revealed that the remodeling cycle is approximately 3 to 4 weeks, with collagen restoration proceeding more rapidly. Next, we traced the fate of the Gli1⁺ SuSCs lineage upon application of tensile force in three dimensions. SuSCs were rapidly activated and greatly contributed to bone remodeling within 1 month. Furthermore, we confirmed the presence of Wnt activity within Gli1⁺ SuSCs based on the high co-expression ratio of Gli1⁺ cells and Axin2⁺ cells, which also indicated the homogeneity and heterogeneity of two cell groups. Because Wnt signaling in the sutures is highly upregulated upon tensile force loading, conditional knockout of β-catenin largely restricted the activation of Gli1⁺ SuSCs and suppressed bone remodeling under physiological and expansion conditions. Thus, we concluded that Gli1⁺ SuSCs play essential roles in suture and bone remodeling stimulated by mechanical force and that Wnt signaling is crucial to this process. © 2022 American Society for Bone and Mineral Research (ASBMR).

Response of osteoblastic cells to low-level laser treatment: a systematic review

Low-level laser therapy (LLLT)-induced photobiomodulation (PBM) stimulates bone tissue regeneration by inducing osteoblast differentiation and mitochondrial activation. However, the role of reactive oxygen species (ROS) in this process remains controversial. The aim of this systematic review was to collect and analyze the available literature on the cellular and molecular effects of LLLT on osteoblasts and the role of ROS in this process. A search was conducted in PubMed, ScienceDirect, Scopus, and Web of Science. Studies published in English over the past 15 years were selected. Fourteen articles were included with moderate (n = 9) and low risk of bias (n = 5). Thirteen studies reported the use of diode lasers with wavelengths (λ) between 635 and 980 nm. One study used an Nd:YAG laser (λ1064 nm). The most commonly used λ values were 808 and 635 nm. The energy densities ranged from 0.378 to 78.75 J/cm², and irradiation times from 1.5 to 300 s. Most studies found increases in proliferation, ATP synthesis, mitochondrial activity, and osteoblastic differentiation related to moderate and dose-dependent increases in intracellular ROS levels. Only two studies reported no significant changes. The data presented heterogeneity owing to the variety of LLLT protocols. Although several studies have shown a positive role of ROS in the induction of proliferation, migration, and differentiation of different cell types, further research is required to determine the specific role of ROS in the osteoblastic cell response and the molecular mechanisms involved in triggering previously reported cellular events.

The Effect of Photobiomodulation Therapy in Different Doses on Bone Repair of Critical Size Defects in Rats: A Histomorphometric Study

Introduction: Photobiomodulation therapy (PBM) appears to induce osteogenesis and stimulate fracture repair; because of its capacity, it is considered a promising treatment, but the characteristics of response to different radiation doses must be investigated through in vivo studies to establish their safety and effectiveness. Thus, this paper aims to analyze the effects of the PBM at different doses on the repair of critical bone defects through histological and histomorphometric analyses. Methods: Sixty 90-day-old adult rats (Rattus norvegicus, albinus, Wistar) weighing approximately 300 g were used. Critical bone defects of 5 mm in diameter were performed in their calvaria. The animals were randomly separated into 5 groups: C-Blood clot, L15-PBM 15J/cm², L30-PBM 30 J/ cm², L45-PBM 45 J/cm², L60-PBM 60 J/cm². Each group was subdivided according to observation periods of 30 and 60 days with 6 rats in each subgroup. Low-level gallium aluminum arsenide (GaAlAs) lasers were used at a 660 nm wavelength, 30 mW and 0.04 cm² in area. The PBM was applied over 5 points; 4 points of application were distributed on the edges while one point of application was located in the center of the bone defect. PBM occurred right after the procedure. In 30 and 60 days, the animals were euthanized by anesthesia overdose and the analyses were performed. The data were analyzed statistically by the ANOVA, together with the Tukey test, whose significance level was 5%. Results: As regards the treatment factor, the highest percentage of bone neoformation was achieved by group L45-60. The group with the highest closure, despite not having a statistically significant difference with the other doses, was 45 J with only 0.49 mm between edges. Conclusion: Thus, the present study allowed concluding that the highest percentage of bone neoformation area was achieved at 45 J/cm² in 60 days; that is, it was significantly effective in comparison with other doses.

In vivo efficacy of low-level laser therapy on bone regeneration

PURPOSE

In clinical use of low-level laser therapy for bone regeneration (LLLT), application protocol (dose, duration, and repetitions) has not been established. This study aimed to depict a reliable dosage of LLLT by evaluating the efficacy of different dosing of LLLT (diode) on the healing of rabbit cranial defects.

METHODS

Critical size defects were prepared in calvarias of 26 New Zealand White Rabbits in such each animal containing both test and control groups. Test groups were irradiated with 4 Joule/cm² (j/cm²), 6 j/cm², and 8 j/cm². The rabbits were subjected to six times of laser treatments in 10 days. At the end of the second week, 5 rabbits were sacrificed for histopathological and immunohistochemical analyses. At the 4th and 8th weeks, 20 rabbits (10 each) were sacrificed for micro-CT and histopathological analyses.

RESULTS

Micro-CT evaluation revealed improved new bone formation in all test groups compared to the control group. 6 j/cm² group demonstrated the highest bone formation. The highest bone morphogenic protein -2 levels were found in the 4 j/cm² group. Osteocalcin expression was significantly higher in 4 j/cm² group.

CONCLUSIONS

Our findings indicate that LLLT have a positive effect on new bone formation. The high efficacy of doses of 4 j/cm² and 6 j/cm² is promising to promote early bone healing.

Effect of different low-level intensity laser therapy (LLLT) irradiation protocols on the osseointegration of implants placed in grafted areas

OBJECTIVE

To evaluate the effect of different protocols of low-level intensity laser therapy (LLLT) irradiation on the osseointegration of implants placed in grafted areas.

METHODOLOGY

84 rats were randomly allocated into six groups: DBB: defect filled with deproteinized bovine bone; HA/TCP: defect filled with biphasic ceramic of hydroxyapatite/β-tricalcium phosphate ; DBB-LI: defect filled with DBB and treated with LLLT after implant placement; HA/TCP-LI: defect filled with HA/TCP and treated with LLLT after implant placement; DBB-LIB: defect filled with DBB and treated with LLLT after graft procedure and implant placement; and HA/TCP-LIB: defect filled HA/TCP and treated with LLLT after graft procedure and implant placement. The bone defects were made in the tibia and they were grafted. After 60 days, the implants were placed. The rats were subsequently subjected to euthanasia 15 and 45 days after implant placement. The pattern of osseointegration and bone repair in the grafted area was evaluated by biomechanical, microtomographic, and histometric analyses. Furthermore, the expression of bone biomarker proteins was assessed.

RESULTS

The LLLT groups presented higher removal torque, mineralized tissue volume, and a greater degree of osseointegration, especially when LLLT was performed only after implant placement, and these findings were associated with higher expression of BMP2 and alkaline phosphatase.

CONCLUSION

LLLT performed on implants placed in grafted areas enhances the osseointegration process.

Effect of Photobiomodulation on Relapse in an Experimental Rapid Maxillary Expansion Model in Rat

Rapid maxillary expansion (RME) is performed on transversely deficient maxilla. As all orthodontic treatments, retention is important in maintaining therapeutic outcomes. Fixed /removable retainers are used post-RME causing hygiene and compliance problems. Given photobiomodulation's positive effects on the quantity and quality of bone regeneration, its effect on post-RME relapse was studied. Thirty Sprague Dawley rats were randomly divided into group R, non-irradiated RME-treated (n = 12), group P, irradiated RME-treated (n = 12) and group C, non-RME non-irradiated (n = 6). A 1.5 mm metal ring inserted between maxillary incisors at days 0 and 15 was expanded until 1.5 mm space was obtained at day 30. In group P, Ga-Al-As diode laser (810 nm, 100 mW, 4J/cm² , 30 secs) was applied on days 0, 2, 4, 6, 8, 10, 12 and 14 as predictor variable. The relapse was measured as the space lost between incisors for 30 days after appliance removal (primary outcome variable) and compared with t-test. In week 2, space loss in group P was significantly lower (P < 0.05) than all other groups. The relapse during weeks 2 and 3 was significantly lower in group P than group R. However, no significant difference in relapse amount was found between groups during first and fourth week. There was a significant difference (P < 0.05) between groups in relapse rates (secondary outcome variable) but not in total relapse after 4 weeks. Photobiomodulation proved beneficial in resisting relapse in our study, and it is suggested to be continued until the end of expansion.

Low-Level Laser Light Therapy Dosage Variables vs Treatment Efficacy of Neuromusculoskeletal Conditions: A Scoping Review

OBJECTIVE

The purpose of this scoping review was to identify and synthesize literature on dosage variables on the efficacy of low-level laser therapy (LLLT) for neuromusculoskeletal conditions.

METHODS

A scoping literature review was conducted by searching the following databases: the Cochrane Library, the Cumulative Index to Nursing and Allied Health Literature, Medline, the Physiotherapy Evidence Database, the Index to Chiropractic Literature, manufacturer websites, and online guidelines. The search was modeled after STARLITE criteria. The reporting used Preferred Reporting Items for Systematic Reviews and Meta-analyses Extension for Scoping Reviews (PRISMA-ScR). Articles were included if LLLT was used in any treatment group for a neuromusculoskeletal complaint with dosage and effectiveness reported. This was tabulated by source, dosage variables, conditions, outcome measures, and conclusions. Data were charted in Excel format. Frequency counts were performed on ordinal data. Descriptive statistics were computed for the continuous data.

RESULTS

A total of 86 articles were included in the review. They revealed a broad range of musculoskeletal conditions and diverse dosage parameters. Seven individual parameters were found that would alter the dosage. Although duration of application is an independent clinical factor, the negative-outcome studies were inconsistent in duration. There was lack of statistical difference between the studies with improved vs unimproved outcomes. No statistical differences were noted between the dosage parameters and efficacy.

CONCLUSION

Although many articles were found on LLLT for neuromusculoskeletal conditions, the studies had amorphous parameters. A heterogeneity of reported doses precluded the synthesis of sufficient evidence to correlate dosage variables with improved or unimproved outcomes. Therefore, based on the current literature, dosage variables for the efficacy of LLLT for neuromusculoskeletal conditions are uncertain at this time.

The effect of low-level laser therapy on orthodontically induced root resorption: a pilot double blind randomized controlled trial

Background

The effect of low-level laser therapy (LLLT) on accelerating orthodontic tooth movement has been extensively studied; however, there is limited knowledge on the use of LLLT on orthodontic root resorption.

Objective

To investigate the effect of LLLT on orthodontically induced inflammatory root resorption (OIIRR) and to compare the difference between pulsed and continuous LLLT on OIIRR.

Trial design

Double-blind, single-centre 3-arm parallel split-mouth randomized controlled trial.

Participants

Twenty adolescent patients who required bilateral maxillary first premolar (MFP) orthodontic extractions were recruited from the Sydney Dental Hospital between October 2014 and December 2014.

Intervention

All MFPs were tipped buccally for 28 days to induce OIIRR. The experimental premolars (n = 20) received LLLT and the control premolars (n = 20) received placebo-laser on days 0, 1, 2, 3, 7, 14, and 21. Ten experimental premolars received LLLT via continuous delivery and 10 received pulsed delivery.

Laser parameter

AlGaAs diode laser of 808 nm wavelength, 0.18 W power, 1.6 J per point, and duration of 9s for continuous mode and 4.5 s for pulsed mode.

Outcome

The difference in root resorption crater volume between LLLT and placebo-laser and continuous or pulsed laser delivery after 28 days.

Randomization

Randomization was computer-generated, with allocation concealment by opaque sequentially numbered sealed envelopes.

Blinding

The participants and operator were blinded.

Results

Eighty-eight patients were screened and 20 patients were randomized. Forty premolars were analysed. LLLT resulted in 23 per cent less root resorption compared to the placebo (P = 0.026). Pulsed laser delivery resulted in 5 per cent less root resorption than continuous; however, this was not statistically significant (P = 0.823). No harm was observed.

Conclusion

Teeth treated with LLLT had less total root resorption than placebo-laser. Furthermore, there was minimal difference between pulsed or continuous delivery of LLLT.

Trial Registration

Clinical Trials Registry (ACTRN12616000829415).

Protocol

The protocol was not published before trial commencement.

The effects of low-level laser therapy on orthodontically induced root resorption

The aim of this study was to evaluate the preventive and/or reparative effects of low-level laser therapy (LLLT) on orthodontically induced inflammatory root resorption (OIIRR) in rats. Thirty rats were divided into four groups (short-term control (SC), short-term laser (SL), long-term control (LC), long-term laser (LL)). In all groups, the left first molar was moved mesially for 11 days. At the end of this period, the rats in groups SC and SL were killed in order to observe the resorption lacunas and to evaluate whether LLLT had any positive effect on root resorption. The groups LC and LL were remained for a healing period of 14 days in order to observe spontaneous repair of the resorption areas and investigate whether LLLT had reparative effects on root resorption. A Ga-Al-As diode laser (Doris, CTL-1106MX, Warsaw, Poland) with a wavelength of 820 nm was used. In SL group, the first molars were irradiated with the dose of 4.8 J/cm2 (50 mW, 12 s, 0.6 J) on every other day during force application. In LL group, the irradiation period was started on the day of appliance removal and the first molars were irradiated with the dose of 4.8 J/cm2 on every other day for the next 14 days. LLLT significantly increased the number of osteoblasts and fibroblasts, and inflammatory response in SL group in comparison with SC group (P = .001). The amount of resorption did not represent any difference between the two groups (P = .16). In LL group, LLLT significantly increased the number of fibroblasts and decreased the amount of resorption in comparison with LC group (P = .001; P = .02). Both parameters indicating the reparative and the resorptive processes were found to be increased by LLLT applied during orthodontic force load. LLLT applied after termination of the orthodontic force significantly alleyed resorption and enhanced/accelerated the healing of OIIRR. LLLT has significant reparative effects on OIIRR while it is not possible to say that it definitely has a preventive effect.