High-power LED units currently available for dental resin-based materials—A review

polymers Review High-Power LED Units Currently Available for Dental Resin-Based Materials—A Review Rita Almeida 1, Patricia Manarte-Monteiro 2, Joana Domingues 2, Carlos Falcão2,3 , Mariano Herrero-Climent 3, Blanca Ríos-Carrasco 4,* and Bernardo Ferreira Lemos 2   Citation: Almeida, R.; Manarte-Monteiro, P.; Domingues, J.; Falcão, C.; Herrero-Climent, M.; Ríos-Carrasco, B.; Lemos, B.F. High-Power LED Units Currently Available for Dental Resin-Based Materials—A Review. Polymers 2021, 13, 2165. https://doi.org/10.3390/ polym13132165 Academic Editor: Haw-Ming Huang Received: 31 May 2021 Accepted: 26 June 2021 Published: 30 June 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1Faculty of Health Sciences, University Fernando Pessoa, 4200-150 Porto, Portugal; [email protected] 2Department of Dentistry and Medical Sciences, Faculty of Health Sciences, University Fernando Pessoa, 4200-150 Porto, Portugal; [email protected] (P.M.-M.); [email protected] (J.D.); [email protected] (C.F.); [email protected] (B.F.L.) 3Porto Dental Institute, 4150-518 Porto, Portugal; [email protected] 4Department of Periodontology, University of Seville, 41009 Seville, Spain *Correspondence: [email protected] Abstract: The pursuit of less time-consuming procedures led to the development of high-power light-curing-units (LCU) to light-cure dental-resin-based-materials. This review aims to describe high-power light-emitting-diode (LED)-LCUs, by a bibliometric systematization of in vitro and in vivo studies. The research-question, by PICO model, aimed to assess the current knowledge on dentistry-based high-power LED-LCUs by analyzing to what extent their use can promote adverse events on materials and patients’ oral condition when compared to low-power LED-LCUs, on daily dental practice. PubMed and B-on database search focused on high-power ( ≥ 2000 mW/cm 2 ) LED-LCUs outputs. Studies assessing performance of high-power LED-LCUs for light-curing dental-resin-based-materials were included. From 1822 screened articles, 21 fulfilled the inclusion criteria. Thirty-two marketed units with high levels of radiant emittance ( ≥ 2000 mW/cm 2 up to 6000 mW/cm 2 ) were identified. Most output values vary on 2000–3000 mW/cm 2 . The highest output found was 6000 mW/cm 2 , in FlashMax ™ P3. Reports suggest that light-curing protocols with lower emittance irradiance and longer exposure outperforms all other combination, however in some clinical procedures high-power LED-LCUs are advocated when compared to low-power LED-LCUs. Moreover, long time exposures and over-curing can be dangerous to the biological vital pulp, and other oral tissues. Evidence showing that high-power LCUs are the best clinical option is still very scarce. Keywords: dental curing units; LED curing-lights; composite resins; adverse events; dental materials 1. Introduction Light-curing units (LCU) and an efficient irradiation procedure is indispensable for the clinical success of resin-based dental materials; thus, being aware of this simple, perhaps important task is crucial. Clinicians have at their disposal an unprecedented variety of LCUs, so, in order to make informed decisions, dentists need to consider if the device they are operating is emitting optimal light parameters. The quantity and quality of light generated by a LCU is highly dependent on the radiant emittance, exposure time, and spectral emission, respectively, but also on the interactions between these variables and their compatibility with the monomeric properties of the restorative material [1]. Radiant emittance (expressed in units of mW/cm 2 ) describes the output from a curing light device and therefore is the power emitted by the light source divided by the area of the light tip. While irradiance—also referred to as intensity or power density—is the power incident on a surface and describes the quantity of light-energy that a resin-based Polymers 2021,13, 2165. https://doi.org/10.3390/polym13132165 https://www.mdpi.com/journal/polymers Polymers 2021,13, 2165 2 of 30 material receives (also expressed in units of mW/cm 2 ) [ 2 ]. The International Organization for Standardization (ISO) 4049:2000 considered an irradiance level of 300 mW/cm 2 as being enough to induce adequate polymerization of light-cured resin-based materials [1]. Spectral emission is designated by the wavelength range within the electromagnetic spectrum emitted. Most dental resin-based materials contain two-components: the photoinitiator, generally a camphorquinone (CQ) or other photo-initiator systems as diphenyl phosphine oxide (TPO) and as Ivocerin [ 3 ] which can absorb light directly, and a co-initiator, typically an amine, that does not absorb light but interacts with the activated photo-initiator to generate a reactive free radical and initiates resin-monomers polymerization. Efficient monomer polymerization occurs when corresponding wavelengths match the maximum absorption of the material’s photoinitiator system [4,5]. Nonetheless, the total delivered optical energy depends on the exposure time. The emission of light to a given surface over time is called radiant exposure (expressed in units of J/cm 2 ) [ 6 ]. Current light-emitting diode (LED)-LCUs may have multiple light modes with variation on light output emission and time protocol, allowing different radiant exposures. A critical feature of the light-cured composites and every resin-based dental material is their adequate polymerization. The degree of monomer polymerization is determined by the proportion of the remaining concentration of the double carbon bonds in a polymerized sample relative to the total number of double carbon bonds in the uncured material. The degree of conversion directly affects the chemical, physical, and mechanical properties of resin-based composites (RBC) and a higher degree of conversion indicates a greater amount of dental material monomer polymerization [7]. Since LED-LCUs were marketed and introduced, their use became increasingly popular for curing dental materials. Nevertheless, it was not before the 1990 s, when the first commercial LED-LCU became available, that LEDs were seriously considered by scientists or manufacturers of commercial LCUs as light sources to photopolymerize dental composites and other dental materials [ 8 ]. First generation LED’s radiant emittance ranged from 160 to 400 mW/cm 2 , implying less curing potential than conventional competitive types of LCUs. Later, in 2002, a second generation with a higher radiant emittance range of 500–1400 mW/cm 2 was introduced, being able to reach values up to 1500 mW/cm2[9,10] . Those versions emitted a similar narrow spectrum designed to match the absorption spectrum of CQ, the most common photoinitiator of resin-based dental materials composition [8] . Around 2004, the advances in LED technology enabled the development of higher power LED-based systems: the third generation of LED curing units [ 8 ]. The radiant emittance levels were increased, and those medical devices are now capable of delivering radiant emittance values up to 5000 mW/cm 2 [ 11 ]. Additionally, in order to address the mismatch between the emission spectrum and photoinitiators besides CQ, an additional emission peak was introduced in LED-LCUs, able to activate a wider range of photoinitiators. Those are equipped with multiple diodes, able to radiate both violet and blue light having an optimal spectral wavelength range within 400–500 nm (nanometers) [8,12]. Newer LED-LCUs are currently being introduced on the market, advocating a fourthgeneration technology. Among several enhancements, a wavelength scanning technology is the most significant improvement, allowing the clinician to select the appropriate output mode according to the material and the clinical condition [13]. Light-curing technology continues to evolve at a rapid pace. From the first generation of LED-LCUs that produced poor output, to the current third generation that became capable of delivering higher radiant emittance in short exposure time, these enhanced devices also became polywave, emitting multiple wavelengths bands [8,12]. High-powered LCUs have increased radiant emittance and claimed it could be used for shorter exposure time, thus reducing the curing time needed for dental resin-based materials. However, there is still insufficient research regarding the resin-based materials clinical survival rates and polymerization quality by the newly developed high-power Polymers 2021,13, 2165 3 of 30 LED-LCUs. Low rate of monomers-to-polymer degree of conversion is undesirable, and promotes low chemical, physical, and mechanical properties of resin-based materials in short- and mean-term clinical environments. Material deterioration and subsequent increasing water absorption, marginal wear, microleakage, discoloration, staining and [ 14 – 19 ] also monomer elution and leaching out of components to the pulp or gingival tissues and decrease in material biocompatibility may occur [ 15 ]. Also, data regarding clinical adverse events those LCUs may promote in dentin-pulp complex/biological tissues is another clinical condition to be addressed. The consecutive or prolonged light-curing mode emissions induce significant and cumulative temperature rise, leading to a potential damage of the dentin-pulp complex [ 20 – 22 ]. Symptoms such as hyperalgesia, hypersensitivity, and spontaneous pain, typical of acute pulpitis, suggest this damage [ 21 ]. As claimed by Rueggeberg et al. and Alasiri et al. other adverse events have been reported, such as burning sensation on the surrounding soft tissues and ocular hazard, when high levels of blue light are emitted [23,24]. Therefore, the aim of this review is to describe the current high-power LED-LCUs, including a bibliometric systematization of in vitro and in vivo studies of LED-LCU parameters and possible adverse events that can occur, both on resin-based dental materials and patients’ oral condition, while applying it to daily dental practice. 2. Materials and Methods This review was conducted in accordance with the guidelines of an integrative review and the research question, based on the PICO model, aimed to assess the current knowledge on dentistry-based high-power LED-LCU currently available (Problem) by analyzing to what extent their use (Intervention) can promote adverse events on materials and patients’ oral condition (Outcome), in in vitro and in vivo assays, when compared to low-power LED-LCU (Control), used in daily dental practice. 2.1. Inclusion and Exclusion Criteria Only studies that evaluated irradiation protocols with high-power output devices were included. In Vitro and in vivo studies assessing the performance parameters of high-power LED-LCU currently available and assessing any adverse events on materials and patients’ oral condition were included. Performance parameters of high-power LED-LCU were established to devices with radiant emittance values ≥ 2000 mW/cm 2 . Only articles written in the English language and published within the years 2010 to 2021 were contemplated for this review. Articles reporting exclusively halogen, plasma-arc, or argon-ion laser curing lights, light-cured materials polymerized with radiant emittance below 2000 mW/cm 2 or whose radiant emittance was not mentioned were excluded. The inclusion and exclusion criteria were established by a consensus reached from two examiners (RA and PMM) after discussion, considering the research question and the objectives of the study while aiming for an ample range of results to be provided from the search. 2.2. Search Strategy 2.2.1. Sources of Information An electronic search was made in PubMed and B-on electronic databases. The structured search strategy of the articles and data extraction were conducted by two calibrated examiners (RA and PMM) in order to identify all in vivo and in vitro studies on high-power LED light-curing units. To collect data of the commercially available LCUs used in dental offices an extensive on-line hand-search was conducted. The last search was performed in April 2020. Manufacturers were identified through the 2019 exhibitors’ manual of an international dental congress (Lisbon, Portugal). All manufacturers were assessed (online site) in order to identify all commercially available LED-LCUs with a claimed output ≥ 2000 mW/cm 2 . Ad- Polymers 2021,13, 2165 4 of 30 ditionally, two dental material manufacturer’s devices mentioned in the reviewed studies, that met the inclusion criteria, were retained for quality assessment. If any information was missing, the manufacturers were contacted via e-mail to supply the missing data. When manufacturers failed to provide an answer, the respective information was mentioned as “Not Found”. 2.2.2. Search Terms The search strategy included 5 Mesh (Medical Subjects Headings) terms: “Dental Curing Units”, “LED Dental Curing-Lights”, “Composite Resins”, “adverse events” “dental materials” and 11 uncontrolled descriptors: “LED dental curing-lights”, “dental curing lights“, “curing lights dental”, “high-power LED”, “high intensity LED”, “resin-based composite”, “dental resins”, “dental materials”. Boolean operators (“OR” and “AND”) were used to join search terms relevant to the search question (Table 1). The last search was performed in March 2021. Table 1. Search strategy used in each electronic database. Search field 1 (“LED dental curing-lights” OR “dental curing lights “ OR “curing lights dental” OR “high-power LED” OR “high intensity LED” AND Search field 2 (“resin-based composite resins” OR “dental resins” OR “dental materials”) 2.2.3. Study Selection Articles identified using the search terms were exported to Mendeley desktop 1.19.4 software to check for duplicates. A first screening of record titles and abstracts was carried out by two independent examiners according to the inclusion and exclusion criteria. The remaining studies were assessed for eligibility and qualitative synthesis by full-text screening. 2.2.4. Study Data Bibliometric analysis was performed recording the following variables: authors and year of publication. The methodology of analysis included the summary of aims, materials and methods and outputs of the included studies, by transcription of the following variables: study type, clinical procedure performed, high-power LED-LCU used, radiant emittance (by manufacturer and used in the study), exposure time, control LCU used and respective radiant emittance and exposure time, and lastly the irradiation technique employed. For the synthesis of outcomes, studies were categorized in terms of significant results found regarding the LCU used and/or the adverse events that occurred on resin-based dental materials and patients’ oral condition, by their use. Additionally, for the synthesis of identified high-power LED-LCUs currently and commercially available, manufacturer’s LCU Directions for Use (DFU) were assessed, and the following variables were transcribed: manufacturer, LED-LCU, high-power curing modes’ radiant emittance and exposure time, estimated wavelength range, incorporated (yes/no) light meter and link to DFU. 2.3. Quality Assessment The quality of the studies was assessed using the modified CONSORT checklist of items for reporting pre-clinical studies on dental materials/devices [ 25 ] and the CONSORT 2010 guidelines for reporting randomized clinical trials [26]. 3. Results 3.1. Study Selection and Flow Diagram A total of 1822 preliminary references related to dental articles were assessed ( Figure 1 ). Polymers 2021,13, 2165 5 of 30 Polymers 2021, 13, x FOR PEER REVIEW 5 of 32 2.3. Quality Assessment The quality of the studies was assessed using the modified CONSORT checklist of items for reporting pre-clinical studies on dental materials/devices [25] and the CONSORT 2010 guidelines for reporting randomized clinical trials [26]. 3. Results 3.1. Study Selection and Flow Diagram A total of 1822 preliminary references related to dental articles were assessed (Figure 1). Figure 1. Search flowchart according to PRISMA illustrating study inclusion. After excluding duplicates, the remaining articles were screened and 1727 were excluded by reading the title and/or abstract. The resulting 95 articles were examined at fulltext level, and out of these, 74 articles were excluded due to evaluation of intensities bellow 2000 mW/cm2 (n = 69), unmentioned light radiant emittance (n = 3), and description of other LCUs type (n = 2). 3.2. Study Characteristics 3.2.1. Study Design To evaluate the performance of LED-LCUs with radiant emittance ≥2000 mW/cm2 a total of 21 articles were considered: 17 in vitro and 3 in vivo studies. Additionally, 1 article presented both an in vitro and an in vivo setting. All reviewed studies are summarized in Table 2. 3.2.2. Clinical Procedure High-power LED-LCUs studied were assessed in several daily clinical procedures. They were analyzed to determine what extent their use can promote adverse events on Records identified through database searching B-on (n = 1743) PubMed (n = 68) Screened records (n = 1822) Studies included (n = 21) Full-text articles assessed for eligibility (n = 95) Additional records identified (n = 11) Articles excluded after full text analysis (n = 74) Records excluded by title and/or abstract (n = 1727) Studies evaluated intensities bellow 2000mW/cm2 (n = 69) Studies did not mention light radiant emittance (n = 3) Studies described other LCUs types (n = 2) Figure 1. Search flowchart according to PRISMA illustrating study inclusion. After excluding duplicates, the remaining articles were screened and 1727 were excluded by reading the title and/or abstract. The resulting 95 articles were examined at full-text level, and out of these, 74 articles were excluded due to evaluation of intensities bellow 2000 mW/cm 2 (n= 69), unmentioned light radiant emittance (n= 3), and description of other LCUs type (n= 2). 3.2. Study Characteristics 3.2.1. Study Design To evaluate the performance of LED-LCUs with radiant emittance ≥ 2000 mW/cm 2 a total of 21 articles were considered: 17 in vitro and 3 in vivo studies. Additionally, 1 article presented both an in vitro and an in vivo setting. All reviewed studies are summarized in Table 2. 3.2.2. Clinical Procedure High-power LED-LCUs studied were assessed in several daily clinical procedures. They were analyzed to determine what extent their use can promote adverse events on teeth submitted to irradiation protocols and on several dental resin-based materials such as resin cements, sealants, resin-based composites, and adhesive systems. 3.2.3. High-Power LED-LCUs High-power LED-LCUs evaluated ranged from commercially available to experimental devices. Radiant emittance of high-power curing modes according to the manufacturer and mean values measured in the studies were presented. Exposure time applied was also included. Polymers 2021,13, 2165 6 of 30 3.2.4. Control LCUs Quartz tungsten halogen LCUs, standard LED-LCUs or high-power LED-LCUs in standard mode were used to compare the results. Radiant emittance according to the manufacturer and exposure time applied were considered. 3.2.5. Irradiation Technique Only 14 studies mentioned the irradiation protocol used. One study stated it was followed the LCU manufacturer’s protocol without specifying the procedure [ 27 ]. Thirteen studies reported in detail the irradiation technique applied [10,11,14,16,17,21,22,28–33]. 3.3. Quality Assessment All in vitro studies analyzed with the modified CONSORT checklist (Table 3) presented a structured abstract (item 1) and an introduction which provided scientific background about light-curing in dentistry (item 2a) and clear objectives and hypotheses (item 2b). Description of methodology as well as of the variables studied was sufficiently clear to allow for replication in all studies (items 3 and 4), but the majority of them did not present a detailed report of the calculation of sample size or random allocation sequence (items 5–9). All studies indicated the statistical method used (item 10), but presented significance level as p values, and not confidence intervals (item 11). Discussions included a brief synopsis of the key findings, comparisons with relevant findings from other published studies and limitations of the studies (item 12). Sources of funding (if any) were indicated in the majority of studies (item 13), and indications for access to full trial protocols were obviated in all studies (item 14). The four in vivo studies analyzed using the CONSORT 2010 guidelines (Table 4) were not identified as a randomized trial in the title (item 1a) but all provided a clear and detailed abstract (item 1b). In the introduction all the authors presented specific scientific background of the high-power LED-LCUs studied (item 2a) and established the purposes of the trial (item 2b). Details about the trial design and conceptual framework were not clearly described in all studies (item 3a) but information about the eligibility criteria (item 4a), settings and locations where the data were collected (item 4b) and intervention for each group (item 5) were included in all studies. No deviations from the protocol were made and reported during the course of the trials (item 3b an item 6b). Completely defined pre-specified primary and secondary outcome measures, including how and when they were assessed, were presented (item 6a). No interim analysis was performed (item 7b). One study failed to mention how sample size was determined but the remaining authors stated the ideal sample size for detecting clinical statistically significant results (item 7a), nevertheless, none of the studies presented a detailed report of the random allocation sequence and implementation (items 8a–11b). Both statistical methods and additional analyses (item 12a and item 12b) were shown in all studies. Although all studies reported for each group the number of participants who were randomly assigned, received intended treatment, and were analyzed for the primary outcome (item 16), no participant flow diagram was included for analysis (item 13a and 13b); none had a table presenting baseline demographic and clinical characteristics for each group (item 15). All of the studies included the periods of follow-up but two failed to report the dates of recruitment (item 14a). No decision to early stop the trial was reported in any study (item 14b). The results for each study group were reported in all studies but were carried out with pvalues as a measure of precision and not confidence intervals (item 17a and 17b). Moreover, no additional analyses of the same data were undertaken (item 18). The studies did not mention any unintended adverse effects each group may have suffered (item 19). Items referring to the discussion were fulfilled by all studies (items 20–22). Lastly, information as registration number and where the full trial protocol can be accessed were obviated in all cases (item 23 and 24) and sources of funding (if any) were described (item 25). Polymers 2021,13, 2165 7 of 30 Table 2. Summary of the reviewed studies. Author, Year Study Design Clinical/ Technical Procedure High-Power LED-LCU (Manufacturer) Radiant Emittance 1 (mW/cm2) Exposure Time 1 (s) Radiant Emittance Mean Value 2 (sd) (mW/cm2) Control LCU (Manufacturer) Radiant Emittance (mW/cm2) Exposure Time (s) Irradiation Technique Park, Roulet and Heintze, 2010 [22] In Vitro Maxillary premolar exposed to light curing units LEDexp2000 Prototype (Ivoclar Vivadent, Liechtenstein) LEDexp3000 Prototype (Ivoclar Vivadent, Liechtenstein) 2000 3000 60 60 Not reported Astralis®10 (Ivoclar Vivadent, Liechtenstein) Bluephase®16i (Ivoclar Vivadent, Liechtenstein) 1200 1600 30 60 The unprepared tooth was light cured from the buccal side 1 mm from the buccal surface. Flury et al., 2013 [10]In Vitro Light curing resin cements through glass ceramics VALO® (Ultradent, Utah, USA) 3200 18 3505 Elipar™ Freelight 2 (3M ESPE, Seefeld, Germany) VALO® (Ultradent, Utah, USA) 1200 1400 40 32 Light curing was performed either directly or through ceramics discs of 1.5 or 3 mm. Branchal et al., 2015 [31]In Vitro Light curing sealants VALO® (Ultradent, Utah, USA) Fusion® (DentLight Inc., Texas, USA) SmartLite® Max (Dentsply International, York, PA, USA) 3200 2700 2805 3, 6, 9 5, 10 10 3539 2773 2012 3M™XL 3000 (3M ESPE, Minn, USA) 450 40 The light tip was placed directly in contact with the surface. Gonulol, Ozer and Tunc, 2015 [16] In Vitro Polymerization of resin-based tooth-colored restorative materials VALO® (Ultradent, MO, USA) 3200 6 Not reported Elipar ™ S10 (3M ESPE, MN, USA) VALO® (Ultradent, MO, USA) 1200 1000 or 1400 10 20 or 12 The light guide was in contact with the top surface. Polymers 2021,13, 2165 8 of 30 Table 2. Cont. Author, Year Study Design Clinical/ Technical Procedure High-Power LED-LCU (Manufacturer) Radiant Emittance 1 (mW/cm2) Exposure Time 1 (s) Radiant Emittance Mean Value 2 (sd) (mW/cm2) Control LCU (Manufacturer) Radiant Emittance (mW/cm2) Exposure Time (s) Irradiation Technique Haenel et al., 2015 [17]In Vitro Light curing dental resins Bluephase®20i (Ivoclar Vivadent, Schaan, Liechtenstein) 2200 5, 20, 80 2222 Celalux®2 (VOCO, Cuxhaven, Germany) Bluephase®20i (Ivoclar Vivadent, Liechtenstein) 1000–1500 3 650 5, 20, 80 5, 20, 80 The light guide tips were placed directly over the center of the sample. Runnacles et al., 2015 [ 32 ] In Vivo Human premolars exposed to a light curing unit Bluephase®20i (Ivoclar Vivadent, Schaan, Liechtenstein) 2000 5 2204 (35) Bluephase®20i (Ivoclar Vivadent, Liechtenstein) 650 1200 10 10, 60 The LCU tip was placed against the buccal tooth surface with the lower edge of the light guide sheath just above the facial free gingiva. Ward et al., 2015 [34]In Vivo Brackets cured with a high-intensity LED VALO®Ortho (Ultradent, UT, USA) 3200 6 Not reported VALO®Ortho (Ultradent, UT, USA) 1200 20 Not reported Watanabe et al., 2015 [ 33 ] In Vitro Polymerization of dual-cured resin cement PenCure 2000 (Morita, Tokyo, Japan) VALO® (Ultradent, Utah, USA) 2000 3200 5, 10, 15, 20 5, 10, 15, 20 Not reported Jetlite 3000 (Morita, Tokyo, Japan) Demi™(Kerr, CA, USA) 400 1100 20, 40, 60, 80 20, 40, 60, 80 The tip of the curing unit was placed on the top of the ceramic plate. Armellin et al., 2016 [20]In Vitro Composite restorations in first molars VALO® (Ultradent, Utah, USA) 3200 3 1600 VALO® (Ultradent, Utah, USA) Starlight PRO (Mectron, Carasco, Italy) 1000 1000 20 20 Not reported Polymers 2021,13, 2165 9 of 30 Table 2. Cont. Author, Year Study Design Clinical/ Technical Procedure High-Power LED-LCU (Manufacturer) Radiant Emittance 1 (mW/cm2) Exposure Time 1 (s) Radiant Emittance Mean Value 2 (sd) (mW/cm2) Control LCU (Manufacturer) Radiant Emittance (mW/cm2) Exposure Time (s) Irradiation Technique Oz, Oz and Arici, 2016 [ 35 ] In Vivo/ In Vitro Metal brackets polymerized intraorally and, to extracted tooth VALO®Ortho (Ultradent, Utah, USA) 3200 3 Not reported Elipar ™ S10 (3M Unitek, Monrovia, Calif) 1600 10 Not reported Peutzfeldt, Lussi and Flury, 2016 [28] In Vitro Light curing resin cements VALO® (Ultradent, UT, USA) 3200 3 6 9 3162 (88.2) 3213 (110.9) 3299 (89.0) VALO® (Ultradent, UT, USA) 1000 1400 10, 20 8, 16 The tip end of the LCUwas placed at a distance of 0 mm. Bilgic et al., 2017 [27]In Vitro Curing of orthodontic adhesives VALO®Ortho (Ultradent, Utah, USA) 3200 3 Not reported VALO® (Ultradent, Utah, USA) 1400 3 According to the manufacturer’s instructions. Shimokawa et al., 2017 [ 15 ] In Vitro Polymerization of resin-based composites Single-peak high Prototype (Ultradent, UT, USA) Broadspectrum high Prototype (Ultradent, UT, USA) 3600 3600 5 5 3607 (16.6) 3612 (26.0) Single-peak standard Prototype (Ultradent, UT, USA) Broad-spectrum standard Prototype (Ultradent, UT, USA) 1200 1200 15 15 Not reported Udomthanaporn, Nisalak and Sawaengkit, 2017 [11] In Vitro Orthodontic brackets bonded to human premolars VALO® (Ultradent, UT, USA) FlashMax™P3 (CMS Dental, Copenhagen, Denmark) 3200 4000–6000 6 3Not reported Bluephase® (Ivoclar Vivadent Inc., Amherst, NY, USA) 1200 20 The tip of each curing unit was held about 1 mm away from the bracket-tooth interface. Polymers 2021,13, 2165 16 of 30 Table 6. Cont. Author, Year Clinical Procedure Tests Carried Out Outcomes Udomthanaporn, Nisalak and Sawaengkit, 2017 [11] Orthodontic brackets bonded to human premolars Determined evaluating shear bond strength values and the adhesive remnant index The SBS generated by VALO curing at 6 s was not significantly different from Bluephase curing at 20 s while FlashMax™P3 had significantly lowest mean SBS. Almeida, Martins and Martins, 2018 [18] Bracket bonding to human premolars Determined evaluating shear bond strength values and the adhesive remnant index Reducing exposure time from lead to significantly lower mean values of SBS, even with the use of a high-power LED-LCU. Reduction in time did not affect the amount of adhesive remnant. Park, Roulet and Heintze, 2010 [22] Maxillary premolar exposed to light curing units Measured with a K-type thermocouple Disparity in the intrapulpal peak temperature during the light-curing process and in the rate of temperature decrease in pulp after switching off the device between curing lights with different power densities was observed. Runnacles et al., 2015 [29] Human premolars exposed to a light curing unit Measured with type T thermocouple Exposing tooth to a polywave LED-LCU develops significant increase in pulp temperature. Most exposure modes led to variations in temperature lower than the potential damage threshold temperature increase of 5.5 ◦C, although some teeth exposed to high radiant exposures for 60 s exhibited pulp temperature rises above 5.5 ◦C. Armellin et al., 2016 [20] Composite restorations in first molars Measured with with a type J thermocouple Intrapulpal temperature increase during composite photocuring is related to the exothermic polymerization reaction, the energy from the light unit and time of exposure. Longer exposure times resulted in higher increase of pulp tissue temperature, although radiant emittance was lower. Vinagre et al., 2019 [21] Immediately extracted premolars submitted to light curing procedures Measuredwith with an Optical Fibber Bragg grating sensor A significant pulp temperature rise was detected when intact premolars were exposed to LED-LCUs. Curing modes emitting high energy densities produced pulp temperature variations around or above 5.5 ◦C and might be considered clinically relevant. Temperature changes in the pulp Gross et al., 2020 [29] First premolars requiring extraction exposed to a Polywave LED LCU Measured with a type T thermocouple Short exposure to high radiant emittance values were not different from those when teeth were exposed to longer exposure with lower radiant emittance values, given near-similar radiant exposure values. Also, increase values similar to or even higher than the threshold temperature increase of 5.5 ◦ C caused no noticeable histological changes in the pulp tissue. Polymers 2021,13, 2165 17 of 30 3.4.1. Degree of Conversion (DC) Analysis This property can be assessed by several methods. Five studies directly examined the degree of conversion (DC) of resin-based dental materials through Fourier transform infrared spectrometry (FT-IR). A study by Shimokawa et al. used a custom-designed LCUs—a Single-peak high Prototype and a Broad-spectrum high Prototype both emitting 3600 mW/cm 2 for 5 s and a Single-peak standard Prototype and a Broad-spectrum standard Prototype (Ultradent, UT, USA) equally emitting 1200 mW/cm 2 for 15 s—with the same light tip and construction allowing better standardization of the light conditions. The four emission conditions delivered similar radiant exposures. The authors reported that compared to 3600 mW/cm 2 , equivalent or higher DC values were achieved using 1200 mW/cm 2 radiant emittance [ 15 ]. In the Flury et al. study, VALO ® and Elipar ™ Freelight 2 LCUs were used, selecting light-curing times longer than the recommended by the manufacturers to achieve identical radiant exposures when polymerizing resin cements. Outputs of this study showed that a higher irradiance generally did not result in higher DC within a given resin cement. Similar DC were achieved, though at shorter curing times [ 10 ]. Haenel et al. studied Bluephase ® 20i and Celalux ® 2 LCUs, delivering an irradiance of 666 mW/cm 2 , 2222 mW/cm 2 , and 1264 mW/cm 2 for 5, 20, and 80 s respectively, to dental resins. The final DC after 3 min of measurement exhibited higher DC values for the Turbo mode (2222 mW/cm 2 ) than for the Low mode (666 mW/cm 2 ) specimens. For example, in the Turbo mode an exposure time of 5 s lead to a DC (3 min) of 62.5% while after 80 s a DC of 67.3% was reach. In the Low mode the corresponding DC (3 min) values were 54.2% and 65.2%, respectively [ 17 ]. Daugherty et al. compared different light-curing combinations on bulk-fill composites. S.P.E.C. ® 3 in 3smode and FlashMax ™ P3 were categorized as the high irradiance group (≥2000 mW/cm2) and S.P.E.C.™3 in main mode and Paradigm™ as the conventional irradiance group ( ≤ 2000 mW/cm 2 ). It also categorized Standard, a Short, and Ultra-short exposure times to be of 20 s, 9–10 s, and 3 s, respectively. The authors concluded that radiant exposure—the product of irradiance and exposure time—is more correlative to DC than the irradiance parameter itself, and that the polymerization protocol of bulk-fill composites with standard-irradiance & long-exposure time outperforms all other combinations [14]. Assessment of depth of cure and microhardness testing were also used to appraise the effect of different irradiance emittances. Depth of cure was evaluated by Daugherty et al. and results reveled that the curing combination of standard irradiance & exposure was not significantly different than the high irradiance & short exposure combination. However, the curing combination of standard irradiance & exposure significantly outperformed standard irradiation & short exposure and high irradiance & ultra-short exposure combinations [ 14 ]. The hardness (KHN value) parameter was examined in seven studies [ 15 – 17 , 27 , 28 , 31 , 33 ]. In accordance with DC values, equivalent or higher degree of microhardness values of resin composites were achieved when 1200 mW/cm 2 was used compared to 3600 mW/cm 2 [ 15 ]. Gonulol et al. light-cured a microhybrid composite resin, a giomer-based composite resin, a compomer and a resin-modified glass ionomer cement with different irradiance emittances (Standard—1200 mW/cm 2 ;High-power—1400 mW/cm 2 ;Extra-power—3200 mW/cm 2 ) of VALO ® and used Elipar ™ S10 LCU as control. VALO ® used in Extra-power mode for 6 s did not achieve sufficient polymerization of the restorative material, however when applied for 12 s the High-power mode achieved microhardness values similar to those obtained with the VALO ® in Standard mode and Elipar ™ S10. Authors concluded that High-power mode of the VALO ® can be recommended for clinical applications as it can shorten the time required to properly polymerize resin-based restorative materials [ 16 ]. In the study by Haenel et al., when using the Bluephase ® 20i and Celalux ® 2 for 5 s the mean hardness value of the surface of dental resins increased with exposure time [ 17 ]. Branchal et al. light-cured three sealants (opaque-unfilled, opaque-filled, and clear-filled). The shortest exposure time recommended by the manufacturers (VALO ® for 3 s; Fusion ® for 5 s; SmartLite ® Max for 10 s) was doubled or tripled, without exceeding the manufacturer’s longest exposure limit. A halogen LCU was used for 40 s, as control. The authors reported that opaque-filled and Polymers 2021,13, 2165 18 of 30 clear-filled sealants hardness values were statistically equivalent or better when light-cured with VALO ® for 6 or 9 s than the control LCU, at a depth of 1.5 mm. Fusion ® LCU for 10 s did not adequately cure the three sealants beyond 1 mm. SmartLite ® LCU for 15 s did not adequately cure the sealants beyond 0.5 mm [ 31 ]. Bilgic et al. evaluated the effects on orthodontic adhesives when applying 1400 mW/cm 2 or 3200 mW/cm 2 with VALO ® . Higher hardness values were achieved in the adhesives cured with 3200 mW/cm 2 for 3 s. KHN increased as the irradiation time was extended in the Watanabe et al. study. The authors concluded that when polymerizing dual-cured resin cements, through ceramic material, high-intensity LED units required a shorter irradiation period than halogen and standard LED-LCU to obtain KHN similar to those observed during direct irradiation [ 33 ]. Peutzfeld et al. also studied the impact on KHN of resin cements. Three dual-curing resin cements and a flowable resin composite were light-cured with VALO ® in Standard mode (1000 mW/cm 2 ), High power mode (1400 mW/cm 2 ), or Xtra power mode (3200 mW/cm 2 ). Distinct exposure times were set to obtain two or three levels of radiant exposure, in each light-curing mode. Authors concluded that high irradiance light-curing modes do not impact polymerization of resin-based materials [28]. 3.4.2. Diametral Tensile Strength (DTS) Analysis Only one study focused on this subject [ 19 ]. Specimens of packable composite resin were cured with FlashMax ™ P3 and Ledmax ™ 450 LCUs. The group of specimens that received a high amount of total light energy had high DTS, while the group receiving low total light energy showed lower DTS. The group cured with Ledmax ™ 450 for 20 s had the highest DTS compared to the two other groups cured with FlashMax ™ P3 for 1 and for 3 s. The authors concluded that the curing modes influence the DTS of packable composite resin [19]. 3.4.3. Elastic Modulus (EM) Analysis Bilgic et al. studied the elastic modulus of adhesives in orthodontics and reported higher elastic modulus values when VALO ® was applied at 3200 mW/cm 2 mode for 3 s than when applied at 1400 mW/cm2for 3 s [27]. 3.4.4. Bond Strength (BS) Analysis In order to determine BS, clinical bond failure rates were examined in two in vivo studies [ 34 , 35 ]. Ward et al. selected 34 patients and a total of 680 brackets were bonded using a randomized split-mouth design. In this study two different settings of VALO Ortho ® were used. In 17 participants the maxillary right and mandibular left quadrants were cured with 3200 mW/cm 2 setting for 6 s per tooth while the maxillary left and mandibular right quadrants were cured for 20 s with 1200 mW/cm 2 . On the other 17 patients the quadrants were inverted. All participants were observed for a minimum period of 6 months. The brackets bond failure rate was 1.18% for both curing methods. The authors concluded that 6 s curing time per tooth with a high-power curing light is sufficient to produce clinically adequate bond failure rates, that are comparable to brackets cured with a standard LEDLCU for 20 s [ 34 ]. In Oz et al. clinical trial, 40 participants were included, and a split-mouth design was applied. In group 1, the adhesive was cured for 10 s (1600 mW/cm 2 ) with Elipar S10 ™ and in group 2 for 3 s (3200 mW/cm 2 ) with VALO Ortho ® . Bond failure rate at 12 th month were 2.90% and 3.16%, respectively, allowing to conclude that bracket bonding can be safely accomplished with the two LED-LCUs [35]. Additionally, in vitro bond strength was determined evaluating shear bond strength (SBS) values [ 11 , 18 , 35 ] and the adhesive remnant index (ARI) [ 11 ]. Oz et al. compared the performance of Elipar S10 ™ and VALO Ortho ® LCUs by bonding brackets to extracted premolars, using the same curing times. No significant difference on bond strengths ( 9.8 ±4.27 MPa and 11.43 ± 3.56 MPa) and ARI score were found between groups [ 35 ]. When comparing two exposure times while applying the same LED-LCU and the same radiant emittance, Almeida et al. achieved a significantly higher SBS using a 6 s inter- Polymers 2021,13, 2165 19 of 30 val instead of 3 s interval, concluding that time significantly affected SBS values. The 3 s interval produced an average SBS of 15.79 MPa while the 6 s interval produced an average of 21.57 MPa. The use of high-power LED reducing the curing time from 6 to 3 s decreased the bond strength. [ 18 ]. Udomthanaporn et al. light-cured adhesives with Bluephase ® (1200 mW/cm 2 for 20 s), VALO ® (3200 mW/cm 2 for 6 s) and FlashMax ™ P3 ( 4000–6000 mW/cm2for 3 s ). Similar mean SBS was found for Bluephase ® (21.80 ± 2.85 MPa) and VALO ® (21.04 ± 2.87 MPa); significant lowest mean SBS (4.75 ± 2.82 MPa) was found for FlashMax™P3, despite the highest radiant emittance [11]. 3.4.5. Temperature Changes in Pulp Tissue Analysis The increase of temperature in pulp tissue during the light-curing process was assessed in five studies, by Optical Fibber Bragg grating sensors [ 21 ] or different types of thermocouples [ 20 , 22 , 29 ] inserted into the pulp chamber of extracted teeth, or intraorally but requiring tooth extraction after. Runnacles et al. performed an in vivo study in eight volunteers with well-controlled health conditions requiring extraction of healthy, intact, non-carious, non-restored, fully erupted, upper right and left premolars that were sequentially exposed for 10 s in low intensity (656 mW/cm 2 ), 10 s in high intensity (1244 mW/cm 2 ), 60 s in high intensity (1244 mW/cm 2 ) and 5 s in turbo intensity (2204 mW/cm 2 ), with Bluephase 20i ® . The lowest variation in pulp temperature was reveled for 10 s in low intensity (656 mW/cm 2 ) mode; on the other hand, 60 s in high intensity (1244 mW/cm 2 ) mode resulted in the highest peak and variation in temperature, with some pulp chambers exhibiting a temperature rise above 5.5 ◦ C. No significant difference for the peak pulp temperature was observed for 5s/turbo intensity (2204 mW/cm 2 ) and 10 s/high intensity (1244 mW/cm 2 ) modes [ 32 ]. Armellin et al. showed that longer exposure times (20 s in 1000 mW/cm 2 ) resulted in higher increase of pulp tissue temperature, when comparing to 3 s in 3200 mW/cm 2 , although radiant emittance was lower [ 20 ]. Park et al. registered a temperature increase from 41.0 ◦ C to 53.7 ◦ C depending on the LCU used. Considering 34 ◦ C as the temperature of pulp tissue, an increase of 17 ◦ C and of 19 ◦ C, occurred after 60 s of exposure to the LED exp2000 Prototype and the LED exp3000 Prototype LCU, respectively. Intra-pulpal temperature increased more than 5 ◦ C when the exposure time was longer for more than 10 s with the LED exp2000 Prototype and the LED exp3000 Prototype [ 22 ]. Vinagre et al. concluded that high-energy-level curing modes produced pulp temperature variations around or above 5.5 ◦ C [ 21 ]. Gross et al. compared specific scenarios that represented near similar radiant exposures (10 s with 1231 mW/cm 2 by Bluephase 20i ® and 1 s with 10,000 mW/cm 2 by the experimental LED-LCU—12.3 and 10.0 J/cm 2 , respectively—and 20 s with 1231 mW/cm 2 by Bluephase 20i ® and 2 s with 10,000 mW/cm 2 by the experimental LED-LCU—24.6 and 20.0 J/cm 2 , respectively). The authors concluded that there is no significant difference in pulp temperature changes between 20s/20i and 2s/EXP groups which in turn exhibited significantly higher temperature changes values than 1s/EXP and 10s/EXP [29]. Temperature pulp changes after LED-LCU emission were also observed. Runnacles et al. study revealed that the pulp temperature still remains increased for a few seconds, and then slowly decreases to the pre-exposure baseline value, taking approximately 4 to 5 min to this condition [ 32 ]. According to Park et al., the subsequent decrease in pulp temperature was 0.16 ◦ C/seconds and 0.24 ◦ C/seconds, after turning off the 30 s exposure time with LED exp2000 Prototype and LED exp3000 Prototype, respectively [ 22 ]. Vinagre et al. evaluated the pulp temperature changes after four consecutive exposure modes. During the 30 s rest periods between light emissions, pulp temperature did not recover to baseline levels. Instead, pulp temperature continued to increase until a plateau was reached about halfway through each rest period. Afterwards, pulp temperature decreased approximately 1 ◦ C until a new light emission started [ 21 ]. Similar behavior was noticed in the study by Gross et al. where the pulp temperature kept increasing after the curing light shut off, followed by a rapid drop and slower decrease until the baseline pulp temperature was reestablished. Polymers 2021,13, 2165 20 of 30 3.4.6. High-Power LED-LCUs Commercially Available Thirty-two marketed LED-LCU with high power radiant emittance were identified and their technical details described in Table 7. The manufacturers BA International (Northampton, UK), Clarben (Madrid, Spain), Coltene Iberia S.L. (Madrid, Spain), DiaDent Europe (Almere, The Netherlands), Morita Europe (Dietzenbach, Germany) and MyRay (Bologna, Italy) commercialize each, only one high-power LED-LCU. On the other hand, Bader (Nigrán, Spain) developed distinct high-power units. Aiming to incorporate particular features (i.e., broader emission spectrum or heads with different diameters) Acteon (Merignac, France), CMS Dental (Copenhagen, Denmark), DentLight (Dorset, UK), Ivoclar Vivadent Inc. (Schaan, Liechtenstein), Premium Plus UK Ltd. (Dorset, UK), Ultradent Products Inc. (Utah, UT, USA) and Woodpecker (Guangxi, China) offers different versions of their standard unit. Optional curing modes are available in every LED-LCU, allowing dental professional control over the diverse clinical applications. Manufacturers have assigned a wide range of trade names to the high-power display modes, such as “High Power”, “Boost”, “Quick”, “Xtra Power”, “Turbo”, and others, all consisting in a high radiant emittance and short-curing time light-setting of the LCU. Most of LED-LCU had radiant emittance values between 2000–3000 mW/cm 2 . The highest stated radiant emittance found was 6000 mW/cm2in FlashMax™P3 LCU. Automatic exposure times are typically set, however adjustable time options are available in Be Light LED ® , LED Light Curing ® , and LED Clear ® . These devices allow setting the desired time in the chosen work mode (i.e., 15 to 30 s). Seventeen LED-LCUs are able to radiate multiple wavelengths compatible with different photoinitiators, and the additional fifteen are monowave. Regular LCU check and light emission quality is essential. Eleven LCUs have light meters built into the charging base: MiniLED ® Standard, MiniLED ® Supercharged and MiniLED ® Ortho 2, Bluephase ® Power Cure and T-LED have an incorporated radiometer while Be Light LED ® , D-Lux+ ® , C01-D ™ , C02-D ™ , C01-S ™ , and C02-S ™ have light intensity sensors not specified by the manufacturers. The light output can rarely be reliably measured by a commercial dental radiometer. Also, a single irradiance value cannot completely describe the output of an LCU. To overcome these limitations, calibrated spectrometerbased systems can be used. Since those devices are not generally available in dental offices, manufacturers should provide accurate information about the distribution of the radiant emittance and spectral emission across the light tip in all available settings [2]. Polymers 2021,13, 2165 21 of 30 Table 7. High-power LED-LCUs commercially available and technical details: manufacturer, LED-LCU, radiant emittance and exposure time of high-power curing modes, estimated wavelength range, incorporated light meter, and directions for use (DFU). Manufacturer LED-LCU (Ref. Number) High-Power Curing Modes Radiant Emittance (mW/cm2) Exposure Time (s) Wavelength Range (nm) Light Meter Built in DFU ACTEON, France MINILED STANDARD® (F02530) Fast 2000 6 or 12 420–480 Yes Available at <https://www.acteongroup.com/es/ uploads/media/default/0001/01/444188 825e19cff843cf686925b79f3efb247df5.pdf> (accessed on 19 February 2020) MINILED SUPERCHARGED® (F05217) Fast-Cure 2000 (7.5 mm light tip) 3000 (5.5 mm light tip) 3, 4, 5 or 10 420–480 Yes Available at <https: //www.acteongroup.com/es/uploads/ media/default/0001/01/45de84dd04184 927973481ea27a32bd5b126e089.pdf/> (accessed on 19 February 2020) MINILED ORTHO 2® (F05220) Fast Cure 3000 4, 8, 12 or 32 420–480 Yes Available at <https://www.acteongroup.com/us/ uploads/media/default/0001/01/d57b6f0 c62b68188932a263f44a400fe9b383d76.pdf> (accessed on 19 February 2020) BA INTERNATIONAL, UK ULTIMATE BASE290 (BA110200) Power Level 3 Power Level 4 2000 3000 1, 3 or 5 1, 3 or 5 380–500 No Available at <https://www.bainternational. com/pub/media/kuki/download/50 /BASE290-IFU-FINAL.pdf> (accessed on 20 February 2020). BADER, Spain BE LIGHT LED® (09070004) NF12000 15 to 30 (adjustable) 420–480 Yes Available at <http://www.bader.es/gb/ index.php?controller=attachment&id_ attachment=69> (accessed on 21 April 2020) LED LIGHT CURING® (090770008) NF12000 5 to 40 (adjustable) 420–480 No Available at <http://www.bader.es/gb/ index.php?controller=attachment&id_ attachment=70> (accessed on 21 April 2020) ONE LED LIGHT® (09070088) NF12300 1, 5 or 10 385–515 No NF http://www.bader.es/gb/clinicequipment/1243-one-led-light-bader. html?search_query=one+light&results=35 (accessed on 21 April 2020) Polymers 2021,13, 2165 22 of 30 Table 7. Cont. Manufacturer LED-LCU (Ref. Number) High-Power Curing Modes Radiant Emittance (mW/cm2) Exposure Time (s) Wavelength Range (nm) Light Meter Built in DFU CLARBEN, Spain LED CLEAR® (09–080) Bright Light 2000 5 to 40 (adjustable) 420–480 No Available at <https://clarben.com/_files/20000033 0-3a62b3b5bd/FT-SGC15.01%2 0LAMPARA%20LED%20CLEAR.pdf> (accessed on 21 April 2020) CMS DENTAL, Denmark FLASHMAX™P3 (100400) Green Orange Red 5000 to 6000 1 or 3 1 or 3 (two activations with 0.5 s pause) 1 or 3 (repetitive cycles with 0.5 s pause) 440–480 No NF https://www.cmsdental.com/?id= 422&c=Technic%20Flash&ulang=2 (accessed on 21 April 2020) FLASHMAX™P3 WIDE SPECTRUM (100403) Green Orange Red 5000 to 6000 2 or 4 2 or 4 (two activations with 0.5 s pause) 2 or 4 (repetitive cycles with 0.5 s pause) 390–480 No NF https://www.cmsdental.com/?id= 422&c=Technic%20Flash&ulang=2 (accessed on 21 April 2020) FLASHMAX™P3 ORTHO (NF)1 Green Orange Red 5000 to 6000 1 or 3 1 or 3 (two activations with 0.5 s pause) 1 or 3 (repetitive cycles with 0.5 s pause) 440–480 No NF https://www.cmsdental.com/?id= 422&c=Technic%20Flash&ulang=2 (accessed on 21 April 2020) COLTENE, Spain S.P.E.C.®3 (60013942) 3K Ortho 3000 3000 1, 2 or 3 1, 2 or 3 430–490 No Available at <https://www.coltene. com/pim/DOC/IFU/docifu4000137 8g-spec3-ifu-multisallaindv1.pdf> (accessed on 18 November 2019) Polymers 2021,13, 2165 23 of 30 Table 7. Cont. Manufacturer LED-LCU (Ref. Number) High-Power Curing Modes Radiant Emittance (mW/cm2) Exposure Time (s) Wavelength Range (nm) Light Meter Built in DFU DENTLIGHT, UK FUSION 5™ (7800080) Pulse Plasma 2000 4000 3, 5, 10, 20 or 60 3420–490 No Available at < http://www.dentlight.com///////// /////wp-content/uploads/2019/07/ FUSION5-Platform-IFU.pdf> (accessed on 22 April 2020) FUSION GRAND™ (7830060) Pulse Plasma 2000 4000 3, 5, 10, 20 or 60 3385–490 No Available at < http://www.dentlight.com///////// /////wp-content/uploads/2019/07/ FUSION5-Platform-IFU.pdf> (accessed on 22 April 2020) Available at < http://www.dentlight.com///////// /////wp-content/uploads/2019/07/ FUSION5-Platform-IFU.pdf> (accessed on 22 April 2020) FUSION PLUS™ (7820060) Pulse Plasma 2000 4000 3, 5, 10, 20 or 60 3385–490 No NF http://www.diadenteurope.com/ producten/small-equipment/dluxplus-cordless-curing-light (accessed on 22 April 2020) Available at <http: //downloads.ivoclarvivadent.com/ zoolu-website/media/document/4680 6/Bluephase+PowerCure> (accessed on 20 November 2019) DIADENT, The Netherlands D-LUX+® (4008–1110) Max Power 2400 1, 2 or 3 385–515 Yes Available at <http: //downloads.ivoclarvivadent.com/ zoolu-website/media/document/3948 3/Bluephase+Style+20i+-+en%2C+ de%2C+fr%2C+it%2C+es%2C+pt> (accessed on 18 November 2019) Polymers 2021,13, 2165 24 of 30 Table 7. Cont. Manufacturer LED-LCU (Ref. Number) High-Power Curing Modes Radiant Emittance (mW/cm2) Exposure Time (s) Wavelength Range (nm) Light Meter Built in DFU IVOCLAR VIVADENT, Liechtenstein BLUEPHASE POWER CURE® (667092) 3sCure Turbo 3000 2000 3 5385–515 Yes NF https://www.jmoritaeurope.de/en/ products/handpieces-and- instruments/curing-light/pencure/ (accessed on 22 April 2020) BLUEPHASE STYLE 20i® (682110) Turbo 2000 5 385–515 No NF https://www.myray.it/en/myray/ (accessed on 22 April 2020) NF https://www.premiumplusuk.com/ product/c01-d-led-curing- (accessed on 22 April 2020) MORITA, Germany PENCURE 2000 (NF) 1High Power 2000 2 or 3 380–430 No light-with-fibre-optic-light-guide/ (accessed on 15 November 2019) NF https://www.premiumplusuk.com/ product/c02-d-led-curing- (accessed on 15 November 2019) MYRAY, Italy T-LED (70140020) Standard Quick 2400 (5 mm light tip) 2200 (8 mm light tip) 3780 (5 mm light tip) 1, 2 or 3 1, 2 or 3 430–490 Yes light-90-right-angle-direct-light- source-head/ (accessed on 15 November 2019) PREMIUM PLUS, UK C01-DUAL RANGE™ (NF) 1 Turbo 30+ 30 2000 2000 4 3 (two activations with 1 s pause) 390–480 Yes NF https://www.premiumplusuk.com/ product/c01-s-led-curing-light-with- fibre-optic-light-guide/ (accessed on 15 November 2019) C02-DUAL RANGE™ (NF) 1 Turbo 30+ 30 2500 2000 3 3 (two activations with 1 s pause) 390–480 Yes Available at <https://www. acteongroup.com/es/uploads/media/ default/0001/01/444188825e19cff843 cf686925b79f3efb247df5.pdf> (accessed on 19 February 2020) Polymers 2021,13, 2165 25 of 30 Table 7. Cont. Manufacturer LED-LCU (Ref. Number) High-Power Curing Modes Radiant Emittance (mW/cm2) Exposure Time (s) Wavelength Range (nm) Light Meter Built in DFU C01-SUPER POWER™ (NF)1 Turbo 30+ 30 2000 2000 4 3 (two activations with 1 s pause) 440–480 Yes Available at <https://www. acteongroup.com/es/uploads/media/ default/0001/01/45de84dd041849279 73481ea27a32bd5b126e089.pdf> (accessed on 19 February 2020) C02-SUPER POWER™ (NF) 1 Turbo 30+ 30 2500 2000 3 3 (two activations with 1s pause) 440–480 Yes Available at <https://www. acteongroup.com/us/uploads/media/ default/0001/01/d57b6f0c62b6818893 2a263f44a400fe9b383d76.pdf> (accessed on 19 February 2020) ULTRADENT, USA VALO® (5941) Xtra Power 3200 (8 mm light tip) 3 395–480 No NF https://www.premiumplusuk.com/ product/c02-s-led-curing-light-90 -right-angle-direct-light-source-head/ (accessed on 15 November 2019) VALO GRAND® (5972) Xtra Power 3200 (12 mm light tip) 3 385–515 No NF https://www.ultradent.com/ products/procedures/restorative/ class-I-II-III-IV-composite-restoration/ curing-lights/valo-cordless (accessed on 23 April 2020) VALO ORTHO® (5942) Xtra Power Xtra Power Q 3200 3200 1, 2 or 3 3 (five activations with 2 s pause) 395–480 No NF http://www.glwoodpecker.com/ index.php?m=content&c=index&a= show&catid=36&id=197 (accessed in 23 April 2020) WOODPECKER, China B-CURE® (NF) 1Ortho 2000 3 or 5 (ten activations with 1 s pause) 385–515 No NF http://www.glwoodpecker.com/ index.php?m=content&c=index&a= show&catid=36&id=195 (accessed on 23 April 2020) B-CURE PLUS® (NF) 1Turbo 2800 to 3000 1 or 3 385–515 No NF http://www.glwoodpecker.com/ index.php?m=content&c=index&a= show&catid=36&id=44 (accessed on 23 April 2020)