Photobiomodulation Effects on Periodontal Ligament Stem Cells: A Systematic Review of In Vitro Studies

BACKGROUND

Stem cell therapy has been considered to play a paramount role in the treatment modalities available for regenerative dentistry. The established beneficial effects of photobiomodulation (PBM) at the cellular level have led to the combined use of these two factors (PBM and stem cells). The main goal of this study was firstly to critically appraise the effects of PBM on periodontal ligament stem cells (PDLSCs), and secondly to explore the most effective PBM protocols applied.

METHODS

Pubmed, Cochrane, Scopus, Science Direct, and Google Scholar search engines were used to identify experimental in vitro studies in which PBM was applied to cultured PDLSCs. After applying specific keywords, additional filters, and inclusion/exclusion criteria, a preliminary number of 245 articles were narrowed down to 11 in which lasers and LEDs were used within the 630 - 1064 nm wavelength range. Selected articles were further assessed by three independent reviewers for strict compliance with PRISMA guidelines, and a modified Cochrane risk of bias to determine eligibility.

STATISTICAL ANALYSIS

The dataset analysed was extracted from the studies with sufficient and clearly presented PBM protocols. Simple univariate regression analysis was performed to explore the significance of contributions of potential quantitative predictor variables toward study outcomes, and a one-way ANOVA model was employed for testing differences between the laser or LED sources of the treatments. The significance level for testing was set at α = 0.05.

RESULTS

The proliferation rate, osteogenic differentiation, and expression of different indicative genes for osteogenesis and inflammation suppression were found to be positively affected by the application of various types of lasers and LEDs. With regard to the PBM protocol, only the wavelength variable appeared to affect the treatment outcome; indeed, the 940 nm wavelength parameter was found not to exert a favourable effect.

CONCLUSIONS

Photobiomodulation can enhance the stemness and differentiation capacities of periodontal ligament stem cells. Therefore, for PBM protocols, there remains no consensus amongst the scientific community. Statistical analyses performed here indicated that the employment of a near-infrared (NIR) wavelength of 940 nm may not yield a significant favourable outcome, although those within the 630 - 830 nm range did so. Concerning the fluence, it should not exceed 8 J/cm2 when therapy is applied by LED devices, and 4 J/cm2 when applied by lasers, respectively.

The influence of delivery power losses and full operating parametry on the effectiveness of diode visible-near infra-red (445-1064 nm) laser therapy in dentistry-a multi-centre investigation

The development of protocols for laser-assisted therapy demands strict compliance with comprehensive operating parametry. The purpose of this investigation was to examine the accuracy of correlation between laser control panel and fibre emission power values in a selection of diode dental lasers. Through retrospective analysis using successive systematic review and meta-analysis, it is clear that there is inconsistency in the details, and possible inaccuracies in laser power applied and associated computed data. Through a multi-centre investigation, 38 semi-conductor ("diode") dental laser units were chosen, with emission wavelengths ranging from 445 to 1064 nm. Each unit had been recently serviced according to manufacturer's recommendations, and delivery fibre assembly checked for patency and correct alignment with the parent laser unit. Subject to the output capacity of each laser, four average power values were chosen using the laser control panel-100 mW, 500 mW, 1.0 W, and 2.0 W. Using a calibrated power meter, the post-fibre emission power value was measured, and a percentage power loss calculated. For each emission, a series of six measurements were made and analysed to investigate sources of power losses along the delivery fibre, and to evaluate the precision of power loss determinations. Statistical analysis of a dataset comprising % deviations from power setting levels was performed using a factorial ANOVA model, and this demonstrated very highly significant differences between devices tested and emission power levels applied (p < 10-142 and < 10-52 respectively). The devices × emission power interaction effect was also markedly significant (p < 10-66), and this confirmed that differences observed in these deviations for each prior power setting parameter were dependent on the device employed for delivery. Power losses were found to be negatively related to power settings applied. Significant differences have emerged to recommend the need to standardize a minimum set of parameters that should form the basis of comparative research into laser-tissue interactions, both in vitro and in vivo.

Effect of different types of adhesive systems on the bond strength and marginal integrity of composite restorations in cavities prepared with the erbium laser-a systematic review

There are inconclusive results regarding etching and bonding protocol to achieve optimal bond strength and marginal integrity of adhesive composite resin restorations in erbium laser prepared cavities. This systematic review aimed to consider which adhesive system protocol may be optimal in achieving the bond strength and marginal integrity in erbium laser-prepared cavities, comparable to that obtained with conventional method of cavity preparation. This review was developed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement with literature search based on all publications during the period January1, 2000-October 10, 2020, in three databases: MEDLINE, Google Scholar and ScienceDirect. The necessary information was extracted by two independent authors. The search resulted in 139 articles from all databases, and a total of thirty-one articles met the inclusion criteria. The results indicated that the selection of adhesives depending on their pH and composition and the laser pulse duration and pulse energy used plays an important role in predicting the adhesion and marginal integrity. The 10-MDP containing moderate self-etch adhesives has demonstrated predictable outcomes. Longer pulse durations used for cavity preparations may indicate the use of etch-and-rinse (EnR) or moderate self-etch adhesives (SEA) to allow better resin infiltration in deep craters formed due to laser irradiation. However, further studies with more standardizations in relation to adhesives and laser parameters are needed.

A Spectrophotometric Study on Light Attenuation Properties of Dental Bleaching Gels: Potential Relevance to Irradiation Parameters

Background: During in-office bleaching, appropriate light sources are applied in order to enhance the activity of the bleaching gels applied onto teeth. For this method to be effective, a high absorption of light within the gel is necessary. Variation in the light attenuation capability of the gel, the duration of application and light activation can contribute towards safety hazards associated with this procedure. Methods: In this study, seven different gels and hydrogen peroxide have been evaluated for their optical properties by means of spectrophotometry (440–1000 nm). The transmitted light spectrum was used to estimate the intensity loss for each gel. The mean intensity decreases observed were statistically analysed using an analysis of variance (ANOVA). Results: The five more-pigmented gels tested indicated a very similar intensity loss of around 80%, whereas the remaining two gels showed significantly less attenuation (predominantly, p < 10⁻⁶). Conclusions: Throughout the spectrum of wavelengths examined, and according to the underlying studies evaluated, five of the gels assessed demonstrated an attenuation high enough to possibly avoid overheating of the underlying enamel dentine and pulp. An evaluation of appropriate irradiation parameters is proposed.

Laser Analgesia Associated with Restorative Dental Care: A Systematic Review of the Rationale, Techniques, and Energy Dose Considerations

It is a common experience amongst laser dentists and patients that mid-IR wavelength application in cavity preparation may be achieved without causing any associated pain. The erbium family of lasers (Er,Cr:YSGG 2780 nm and Er:YAG 2940 nm) are frequently used without employing injectable local anesthesia as an adjunct: the phenomenon arising from the application of these devices is known as laser analgesia. This review seeks to apply a systematic approach to the examination of appropriate published studies but also to highlight the need for much more structured clinical investigations that consolidate photonic dose and methodology. A search of published data using PRISMA criteria was carried out to examine clinical trials into laser analgesia in conjunction with restorative dentistry, applying inclusion and exclusion criteria. From this, 10 published articles were selected for analysis. Suitability assessment was carried out, using a modified Cochrane risk of bias methodology. In 8/10 of the included studies, laser-induced analgesia is claimed to be better and effective, while in 2/10 of the studies, no difference was exhibited compared to the control group. Statistical analysis of three split mouth studies concluded that only one of these investigations reviewed demonstrated a significant analgesic effect for laser treatment while the other two did not support this observation. From this data, it is inconclusive to assess the predictability of laser analgesia in cavity preparation. A possible rationale and laser operating parametry has been discussed. Successful implementation of this treatment modality remains technique sensitive and subject to further investigation.

Systematic Review of Post-Surgical Laser-Assisted Oral Soft Tissue Outcomes Using Surgical Wavelengths Outside the 650-1350 nm Optical Window

Objective: To explore via systematic review the validation of uneventful post-surgical healing, associated with shorter and longer laser wavelength applications in minor oral surgery procedures. Methods: From April 28 to May 11, 2020, PubMed, Cochrane Database of Systemic Reviews, and Google Scholar search engines were applied to identify human clinical trials of photobiomodulation (PBM) therapy in clinical dentistry. The searches were carried out with reference to (1) dental laser wavelengths shorter than 650 nm; (2) wavelengths localized within the 2780-2940 nm; and (3) the 9300-10,600 nm range. Selected articles were further assessed by three independent reviewers for strict compliance with PRISMA guidelines and modified Cochrane Risk of Bias to determine eligibility. Results: Using selection filters of randomized clinical trials, moderate/low risk of bias, and the applied period, and following PRISMA guidelines, 25 articles were selected and examined. A risk of bias was completed, where 11 out of 25 publications were classified as low risk of bias, and 14 out of 25 were classified as medium risk status. In total, 6 out of 13 (46% of) studies comparing the examined laser wavelengths with scalpel-based treatment showed positive results, whereas 6 out of 13 (46%) showed no difference, and only 1 out of 13 (7.7%) presented a negative outcome. In addition, 5 out of 6 (83% of) studies comparing the examined laser wavelengths with other diodes (808-980 nm) showed positive results, whereas 1 out of 6 (17%) had negative outcomes. Conclusions: A detailed and blinded examination of published studies has been undertaken, applying strict criteria to demonstrate research outcome data, which suggests positive or at worst neutral comparatives when a given laser wavelength system is used against an alternative control therapy. As such, substantiated evidence for laser surgery in delivering uneventful healing and analgesic effects, as an expression of a PBM-like (quasi-PBM) influence, has been shown.

Do Lasers Have an Adjunctive Role in Initial Non-Surgical Periodontal Therapy? A Systematic Review

(1) Background: dental lasers have numerous applications for periodontal therapy which include surgical procedures of soft tissue and osseous structures, and non-surgical treatments such as pathogen reduction, removal of surface accretions, and photobiomodulation. The aim of this review was to evaluate the scientific literature to ascertain whether lasers have a beneficial role when used adjunctively in initial non-surgical periodontal therapy. (2) Methods: A PubMed search was performed specifically for randomized clinical trials where a dental laser was used adjunctively for initial periodontal therapy on human patients published from January 2010–April 2020. The first search identified 1294 eligible studies. After additional criteria and filters were applied, 20 manuscripts were included in this review. (3) Results: The chosen manuscripts reported on investigations into initial therapy for patients diagnosed with chronic periodontitis. After periodontal charting, conventional instrumentation such as hand and ultrasonic scaling was performed on all patients in the studies, and then a test group or groups of patients were treated adjunctively with a laser. That adjunctive laser group’s periodontal findings showed various degrees of improved health compared to the group treated with only conventional methods. (4) Conclusion: This systematic review found that 70% of the included studies reported significantly better outcomes in certain clinical parameters, but no improvement in others. The remaining 30% of the manuscripts reported no significant difference in any of the measurements. With consideration to correct parametry, lasers have an adjunctive role in initial non-surgical periodontal therapy.

Photobiomodulation and Oral Mucositis: A Systematic Review

Oral mucositis (OM) is a debilitating complication of chemotherapy, and head and neck radiotherapy. In an effort to offer the best possible advice within the limitations of published research, a systematic review with an extended discussion and commentary on dosimetry and dose delivery is presented. Using keywords as listed, Pubmed, Google Scholar and Cochrane databases were searched during a period extending from 1995 to 2019. A total of 782 abstracts were identified. A total of 50 papers were analysed, and of these, 29 satisfied criteria required for systematic review in accordance with an optimized PRISMA statement. Clinical outcome as reported was subject to analysis with respect to time of intervention, incidence and severity of oral mucositis, and pain amelioration, and a comprehensive combined univariate and multivariate statistical analysis of the methods employed was performed. Recommendations are made with respect to the timing of the intervention. Moreover, there is an extended discussion available on the treatment care rationale of photobiomodulation (PBM), and its adjunctive association with OM. In conclusion, early prophylactic application offers clear advantages in clinical management. The many studies and associated variables and covariables assessed here revealed a choice of delivery techniques, associated wavelengths and many further indices to consider with regard to the accomplishment of optical parameters. It is therefore our recommendation that clinicians use PBM as a therapy with a full and proper understanding and training in order to optimise the clinical effects achievable.

Adjunctive Use of Lasers in Peri-Implant Mucositis and Peri-Implantitis Treatment: A Systematic Review

BACKGROUND

The aim of this systematic review is to compare the effectiveness of lasers in the treatment of implant mucositis and peri-implantitis compared to conventional treatment (non-surgical or surgical: resective or regenerative).

METHODS

Sources of PubMed, Cochrane and Google Scholar search engines were used on articles published from 1997 to 2020 in English, with selected keyword criteria applied. Nine randomized controlled trials (RCTs) were selected.

RESULTS

All included studies were considered of "high quality" according to the quality assessment scale. The comparative assessment of the RCTs was done twice for each RCT based on the type of treatment and according to wavelength. There is strong scientific evidence that, regarding non-surgical treatment, adjunct laser application can provide better results only in the short term (three months). Regarding the surgical approach, the method of decontamination plays a subordinate role. All wavelengths/applications presented similar results.

CONCLUSION

Within the limitations of this study, the adjunctive use of lasers in the treatment of peri-implant inflammation is effective for up to three months; there is no strong evidence regarding the long term benefit compared to conventional treatment.

Systematic Review of Delivery Parameters Used in Dental Photobiomodulation Therapy

Objective: This systematic review of published data critically appraises the consistency in the reported delivery parameters used in photobiomodulation (PBM) therapies research within clinical dentistry and makes reporting recommendations for future clinical protocols. Background: Key to the standardization of randomized clinical trials and associated peer-reviewed articles is the disclosure of all laser and light-emitting diode operating parameters. The current status shows a lack of full parameters and significantly impacts on the ability to integrate published data with current and future investigation into clinical PBM therapy. Materials and methods: Search engines, PubMed, Google Scholar, and Cochrane, were scanned for investigation into the effects of PBM therapy research within clinical dentistry. Key words "Low-Level-Laser," "PBM," "Photobiomodulation," "Oral" and "Therapy" were used and a total of 754 articles identified, spanning a period of 9 years and 1 month between February 2009 and March 2018. Only human clinical trials were considered. Fifty-two articles were included in this investigation and the reported basic delivery parameters used in PBM therapies research were considered for each clinical trial. Results: The overall reported basic delivery parameters used in PBM therapies research were too inadequate to be able to be replicated in further studies. These included parameters related to the power meter, beam cross-sectional dynamics, fluence, and wider aspects of dosimetry. Conclusions: The delivery parameters used in PBM therapy research within clinical dentistry, investigated in this study, presented a wide variation in their recording or nonrecording of all significant elements needed to have scientific validity. A constant inconsistency in delivering valid, reliable, PBM therapy doses, to target tissues was also identified. The lack of consensus in delivering a sound protocol for PBM therapy, is partly due to the lack of adequate reported materials and methods, which are essential for replication of individual studies. One way to resolve this problem is for Journals to insist on all comprehensive parameter records, used in PBM therapies, to be part of author guidelines in submitting articles of studies on PBM therapy in clinical dentistry.

Immunohistochemical and immunocytochemical study of bladder carcinomas using the epithelium-specific, tumour-associated monoclonal antibodies HMFG1 and AUA1

The antigenic expression of normal bladder epithelium and transitional carcinomas has been studied using the epithelium-specific, tumour-associated monoclonal antibodies HMFG1 and AUA1. Tissues from 79 cases of bladder carcinoma and 11 cases of non-neoplastic bladder tissues were stained with both the haematoxylin-eosin (H/E) and the indirect two-stage immunoperoxidase methods using the monoclonal antibodies (MAbs) HMFG1 and AUA1 at a concentration of 25 micrograms ml-1. Positive and negative controls were also used. Moreover, 46 urine smears prepared after cytocentrifugation were stained with both the Papanicolaou and the indirect two-stage immunoperoxidase methods. The results showed that HMFG1 reacted with the majority of cases of grade III carcinomas and carcinomas in situ and with a subset only of low-grade (I and II) carcinomas. The pattern of staining showed the following characteristics: (1) the epithelial surface membrane stained both in normal bladder and bladder carcinomas (surface of the papillae), (2) a variant number of cancer cells, increasing with the degree of malignancy, showed membrane and/or cytoplasmic staining, (3) tumours of the same histological grade showed antigenic heterogeneity. The MAb AUA1 was not widely expressed. The immunocytochemical study confirmed the reaction of HMFG1 with a variant number of malignant urothelial cells exfoliated in urine. Their reaction with AUA1 was much more limited. The immunocytochemical staining seemed to be more sensitive in the detection of malignant cells in some cases which had been characterized as negative or suspicious for malignancy by the Papanicolaou examination. The intravesical treatment with chemotherapeutic agents did not seem to influence the antigenic expression of malignant urothelial cells.