Full operating parameter recording as an essential component of the reproducibility of laser-tissue interaction and treatments.

BACKGROUND: The number and diversity of published peer-reviewed studies in the discipline of laser dentistry have grown considerably during the past 10 years. OBJECTIVES: Within primary research, the development of protocols to guide and formulate clinical practice demands precision and ease of reproducibility. Errors in data acquisition and management may become amplified as the applied randomized clinical trials (RCTs) forge new levels of clinical diversity and predictability in the use of laser photonic energy in both ablative (surgical) and sub-ablative (photobiomodulation (PBM) or photodynamic therapy (PDT)) applications. MATERIAL AND METHODS: A comprehensive range of empirical and computational operating parameters must be included in published studies to facilitate the uniformity of powerand time-related values of laser irradiation. RESULTS: Choosing the correct "tissue irradiation parameters" is difficult and depends on the pathology and symptoms, the surface area to be treated, laser wavelength, the thermal relaxation time of each targeted tissue, and controlling penetration depth of the light into tissues. Therefore, to allow the reproducibility of the results, it is recommended that authors mention with the greatest care and clarity the irradiation parameters used in their study. CONCLUSION: This paper outlines the concerns felt regarding the general shortfalls and proposes a minimum range of laser operating parameters that should be represented in future peer-reviewed publications.

Photothermal Effects of High-Energy Photobiomodulation Therapies: An In Vitro Investigation.

The purpose of this study was to investigate photothermal aspects of photobiomodulation therapies (PBMT) in vitro to assist in the development of safe clinical parameters with respect to higher-power devices with large surface applicators. Laser wavelengths in the range of 650 nm-1064 nm were investigated using a thermal camera. Thermographic measures of surface and sub-surface temperature variations of similar lean porcine muscle tissue samples were recorded for a series of calibrated experiments. A thermal comparison was then made between Flat-top and Gaussian beam spatial distribution devices. Outcome data were subjected to statistical analysis using an ANOVA model. Results acquired at similar parameters of irradiance indicated that the application of the 980 nm wavelength was associated with the highest rise in temperature, which decreased with other wavelengths in the order 980 > 1064 ≈ 650 >>> 810 nm (p < 5 × 10-20). All wavelengths assessed were associated with a significant temperature increase, and with the exception of 810 nm, all exceeded the threshold of a 6 °C rise within the prescribed parameter limits. Optical scanning by movement of the applied source over a relevant area was found to offer effective mitigation of these temperature increases. An extended discussion is presented, analysing the clinical significance of the study outcomes. Recommendations are made within the limits of this in vitro study in order to assist future clinical investigations.

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.

Photobiomodulation Delivery Parameters in Dentistry: An Evidence-Based Approach.

Background: Dosimetry at a level of 2-8 J/cm2 at target cellular level has been accepted to represent the optimum range for the stimulatory benefits associated with photobiomodulation therapies. However, it has been proposed that a higher bracket of 10-30 J/cm2 at target tissue level may represent a good and effective range for analgesia, accompanied by at-distance regional anti-inflammatory effects. However, although this provides a useful guideline, transforming recommendations into a translatable and repeatable clinical skill have to date proven elusive. Methods: Based on prior publications of systematic reviews by the authors, key factors have been identified, associated with reported clinical and in vitro and in vivo animal studies that can support outcome success or null responses. Drawn from five recently published systematic reviews, an analysis of an extended published evidence base indicates that research methodology should embrace a mature understanding of terminology, a requirement for consistent metered energy delivery, and an appreciation of optical transport techniques. Results: Using models derived from orthodontics and oncology, evidence-based optimal delivery parameters and techniques are presented. Within the confines of the accepted inclusion criteria, a modified Cochrane risk of bias tool has been applied and the parameters extracted from the included studies were subjected to a meta-analysis. This demonstrated a low risk of bias from the studies included with a multivariate and/or univariate statistical analysis that supports the author's evidence-based determinations. The adoption of a surface optical spot size of >1 cm2 demonstrated a high degree of success in managing both superficial as well as subsurface pathologies in oral care. Also, the timing of the intervention with conditioning before or at the same time as a potentially traumatic cellular event was found to be a significant signal of outcome success. An extended commentary explores the benefits and disadvantages of scanning techniques. Conclusions: The extracted clinical data are cross-referenced to the mechanisms suggested for photobiomodulation therapies from the authors' own current in vitro research, and proposals are made for some possible lines of approach in future research and clinical trials.

Efficacy of compound topical anesthesia combined with photobiomodulation therapy in pain control for placement of orthodontic miniscrew: a double-blind, randomized clinical trial.

This study aims to investigate the effect of compound topical anesthetic (CTA) application combined with photobiomodulation therapy (PBMT) on the level of pain perceived during placement of miniscrews and 24 h post the procedure in the buccal side of the maxillary bone. This randomized, prospective, single-center, split-mouth, double-blinded study included 25 subjects (12 males and 13 females, aged 16 to 35). Two anesthetic techniques before implantation were performed including Profound gel +PBM with 980 nm diode laser and local anesthesia with 2% lidocaine hydrochloride. Then, the miniscrews with the size of 1.6 mm in diameter and 8 mm in length were placed with a hand driver in the buccal side of the maxillary bone. The pain immediately after miniscrew placement (T1), also 12 h (T2), and 24 h (T3) post the procedure were collected by visual analog scale (VAS). Data were analyzed by SPSS version 22. There were no statistically significant differences in mean VAS scores within or between CTA combined with PBMT or injection applications, immediately after miniscrew placement (P = 0.75), 12 h after miniscrew placement (P = 0.4), and 24 h after miniscrew placement (P = 1.0). Compound topical anesthetic combined with PBMT provided adequate local anesthesia for the placement of miniscrews in the buccal side of the maxillary bone.

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.

Photobiomodulation Dose Parameters in Dentistry: A Systematic Review and Meta-Analysis.

OBJECTIVE: This systematic review and meta-analysis of published randomized controlled trials examines a possible relationship between optical spot size at surface tissue, irradiance, radiant exposure, total energy delivered, operator technique and reported clinical outcomes. BACKGROUND: Clinical photobiomodulation (PBM) therapy has achieved a high level of evidence-based acceptance in the mitigation of oral mucositis associated with cancer radiotherapy and chemotherapy, and supportive clinical research in relation to orthodontic tooth movement, oral medical conditions, including burning mouth syndrome, xerostomia and lichen planus. Inconsistent outcomes have been reported not withstanding a substantial body of primary supportive research from clinical, in vitro and animal studies. MATERIALS AND METHODS: PubMed, Cochrane Database of Reviews and Google Scholar search engines were applied to identify human clinical trials of PBM therapy in clinical dentistry. A total of 766 articles between February 2009 and June 2020 were identified and following a full text evaluation, 38 papers with sufficient data to permit analyses are included in this investigation. RESULTS: Following a detailed assessment of potential factors that may have an influence in clinical outcome, a clear trend is apparent associating optical spot size to a positive or negative effect. Furthermore, there is a clear difference in the reported results in relation to total energy applied, delivery techniques and optical parameters, which merits further investigation. Factorial statistical analyses identified an association between smaller optical surface applications and an overall lower level of reported clinical success in treating superficial and deeper targets, and correspondingly sub-surface larger target tissues were found to be more responsive to therapy by use of a larger optical surface spot size. Moreover, use of multiple small diameter probe applications was found to provide inconsistent results. CONCLUSIONS: Many factors can confound clinical success including variations in anatomy, site location, clinical condition and subject individuality. To achieve higher levels of predictable outcome, a mature appreciation of these factors, plus an expanded understanding of laser parametry, tissue volume and target depth to deliver an adequate dose within current recommended guidelines, is essential.

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.

Laser-Assisted aPDT Protocols in Randomized Controlled Clinical Trials in Dentistry: A Systematic Review.

BACKGROUND: Antimicrobial photodynamic therapy (aPDT) has been proposed as an effective alternative method for the adjunctive treatment of all classes of oral infections. The multifactorial nature of its mechanism of action correlates with various influencing factors, involving parameters concerning both the photosensitizer and the light delivery system. This study aims to critically evaluate the recorded parameters of aPDT applications that use lasers as the light source in randomized clinical trials in dentistry. METHODS: PubMed and Cochrane search engines were used to identify human clinical trials of aPDT therapy in dentistry. After applying specific keywords, additional filters, inclusion and exclusion criteria, the initial number of 7744 articles was reduced to 38. RESULTS: Almost one-half of the articles presented incomplete parameters, whilst the others had different protocols, even with the same photosensitizer and for the same field of application. CONCLUSIONS: No safe recommendation for aPDT protocols can be extrapolated for clinical use. Further research investigations should be performed with clear protocols, so that standardization for their potential dental applications can be achieved.

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.

Current Concepts of Laser-Oral Tissue Interaction.

Abstract: Fundamental to the adjunctive use of laser photonic energy for delivering therapy and tissue management, is the ability of the incident energy to be absorbed by target tissues. The aim of this review is to examine the differential performance of the separate components of oral hard and soft tissues when exposed to laser photonic irradiance of variable wavelengths and power values. Through an examination of peer-reviewed published data and materials, the interaction of laser photonic energy and target tissues are explored in detail. Varying laser wavelength emissions relative to anatomical structures explores the ability to optimise laser-tissue interactions, and also identifies possible risk scenarios as they apply to adjacent non-target structures. The concepts and practical aspects of laser photonic energy interactions with target oral tissues are clearly demonstrated. Emphasis was placed on optimising the minimum level of laser power delivery in order to achieve a desired tissue effect, whilst minimising the risk or outcome of collateral tissue damage.

Systematic Review of Orthodontic Treatment Management with Photobiomodulation Therapy.

Objective: This systematic review of published research evaluates the parameters and reported outcomes in photobiomodulation therapies (PBMTs) used in management of pain and accelerated tooth movement during orthodontic treatment. Background: Consequent to positive in vitro and animal studies, there has been considerable interest in the potential applications of PBMT to ameliorate pain and to accelerate orthodontic tooth movement. Due to the lack of consistency of wavelengths and parameters applied, there is as yet no consensus in respect of guidance for clinical use. Within the limitations of the reported literature, a digest of key outcomes and parameters is presented here to assist researchers and interested clinicians. Materials and methods: Search engines, PubMed, Google Scholar, and Cochrane, were applied to identify clinical investigations into the potential benefits of PBMTs in orthodontic management. Keywords used were "low-level laser therapy," "low-level light therapy," "photobiomodulation," "orthodontics," "pain," "tooth movement," and "randomized clinical trial ≥5 years." A total of 35 articles were identified, covering the 5-year period January 2013 to December 2018. Only human clinical trials were considered. Seventeen articles were included in this investigation and the reported parameters and outcomes were assessed and presented for comparison. Results: Seven of nine studies supported the effectiveness of PBMT to reduce or prevent pain. There was no consensus on choice of wavelength and a range of parameters were found beneficial. Of the seven tooth movement studies included, four of the seven were positive, of which two used a home-use light-emitting diode (LED) device, as opposed to a clinician-applied laser. A variety of wavelengths and parameters were found to be effective in accelerating tooth movement in the range of 20-40% compared with control. Conclusions: Due to a lack of consistency in approach, further studies are required to achieve a high level of acceptance. The clinical logistics associated with frequent applications supports the concept of patient home delivery use of LED devices, although there are insufficient studies at present to make an evidence-based determination of this type of appliance. To gain more general professional acceptance of the use of PBMT in orthodontics, a continued effort to extend the number of quality human clinical trials is required. Based on the current evidence base, further positive onward progression can be regarded as inevitable.

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.

Feeling the Heat: Evolutionary and Microbial Basis for the Analgesic Mechanisms of Photobiomodulation Therapy.

Background: The clinical therapeutic benefits of Photobiomodulation (PBM) therapy have been well established in many clinical scenarios. However, we are far from having developed a complete understanding of the underlying mechanisms of photon-biological tissue interactions. Concurrent to ongoing PBM studies, there are several parallel fields with evidences from cell and tissue physiology such as evolutionary biology, photobiology, and microbiology among others. Objective: This review is focused on extrapolating evidences from an expanded range of studies that may contribute to a better understanding of PBM mechanisms especially focusing on analgesia. Further, the choice of a PBM device source and relevant dosimetry with regards to specific mechanisms are discussed to enable broader clinical use of PBM therapies. Materials and methods: This discussion article is referenced from an expanded range of peer reviewed publications, including literature associated with evolutionary biology, microbiology, oncology, and photo-optical imaging technology, amongst others. Results and discussion: Materials drawn from many disparate disciplines is described. By inference from the current evidence base, a novel theory is offered to partially explain the cellular basis of PBM-induced analgesia. It is proposed that this may involve the activity of a class of transmembrane proteins known as uncoupling proteins. Furthermore, it is proposed that this may activate the heat stress protein response and that intracellur microthermal inclines may be of significance in PBM analgesia. It is suggested that the PBM dose response as a simple binary model of PBM effects as represented by the Arndt-Schulz law is clinically less useful than a multiphasic biological response. Finally, comments are made concerning the nature of photon to tissue interaction that can have significance in regard to the effective choice and delivery of dose to clinical target. Conclusions: It is suggested that a re-evaluation of phototransduction pathways may lead to an improvement in outcome in phototheraphy. An enhanced knowledge of safe parameters and a better knowledge of the mechanics of action at target level will permit more reliable and predictable clinical gain and assist the acceptance of PBM therapy within the wider medical community.

The Adjunctive Use of the Erbium, Chromium: Yttrium Scandium Gallium Garnet Laser in Closed Flap Periodontal Therapy. A Retrospective Cohort Study.

OBJECTIVES: The current periodontal literature has been inconsistent in finding an added advantage to using lasers in periodontal therapy. The aim of this study was to compare treatment outcomes following root surface instrumentation alone (NL group), or with adjunctive use of Erbium, Chromium: Yttrium Scandium Gallium Garnet (Er,Cr:YSGG) laser (L group). MATERIAL AND METHODS: Patients diagnosed with generalized chronic periodontitis, having a minimum of 1 year follow up were selected by a blinded party for inclusion in a retrospective analysis from patients treated prior to and after integration of laser in a single clinic setting. Probing depths (PD) of all sites ≥5 mm and full mouth bleeding scores were analyzed. Further analysis was carried out on the treatment outcomes of only the molar teeth and of pockets >6mm. RESULTS: 53 patients were included (25 NL,28 L). There was no significant difference between baseline PDs (NL=6.19mm, L=6.27mm, range 5-11mm). The mean PD after one year was 2.83mm (NL) 2.45mm (L), with the mean PD reductions being 3.35mm (NL) and 3.82mm (L) (p<0.002). The mean PD reduction for the molars were 3.32mm (NL) and 3.86mm (L) (p< 0.007), and for ≥7mm group were 4.75mm (NL) compared to 5.14mm (L) (p< 0.009). There was significantly less bleeding on probing in the laser group after one year (p<0.001). CONCLUSION: Both treatment modalities were effective in treating chronic periodontitis, but the added use of laser may have advantages, particularly in molar tooth sites and deeper pockets. Further research with RCTs is needed to test this hypothesis further.