Light-curing Units Research Articles

Photo-polymerization kinetics of a dental resin at a high temporal resolution

ObjectivesThis study: 1) aims to measure with high temporal resolution the intrinsic rate of the degree of conversion (DC) of a dental resin-based composite (RBC) photo-cured at two irradiances; 2) aims to determine the transition time at which the DC rate is maximum; 3) used two different irradiances to measure the shift in transition time; 4) aims to compare transition times measured using DC and shrinkage strain. MethodsSamples (n = 20) 1 mm thick by 10 mm diameter of Filtek One bulk-fill restorative A2 shade (3M Oral Care) were photocured for 20 s with a single emission peak (wavelength centered at 455 nm) light-emitting-diode-based light-curing unit at irradiance levels of 890 mW/cm2 and 209 mW/cm2, and initial sample temperature of T = 23 °C. The DC was measured in real-time using Attenuated Total Reflection (ATR) FTIR spectroscopy with a sampling rate of 13 DC data points per second. The data were analyzed within a phenomenological autocatalytic model. In addition, the axial shrinkage strain was measured using 3 samples of the RBC with the same outer dimensions and under similar experimental conditions using the bonded disk method and an interferometric technique. ResultsFor the 890 mW/cm2 and 209 mW/cm2 irradiance levels, the DC with time was found to agree with the model enabling the determination of transition times of 0.66 ± 0.05 s and 2.3 ± 0.2 s, and the DC at these times of 5.5 ± 0.2% and 6.4 ± 0.2%. The maximum linear strain rate at 0.76 ± 0.01 s and 1.98 ± 0.02 s for the 890 mW/cm2 and 209 mW/cm2 irradiance levels, respectively, are within two standard deviations of the corresponding transition times. SignificanceAt an irradiance level much greater than 1000 mW/cm2, the photo-polymerization kinetics of a dental RBC may be too fast to be measured accurately using ATR-FTIR spectroscopy. A viable alternative to monitor the kinetics is through the measurements of the axial shrinkage strain employing the bonded disk method and an interferometric technique.

Polywave And Monowave Light-Curing Units Effects On Polymerization Efficiency Of Different Photoinitiators

Objective: of this study was to characterize and correlate the absorption spectra of three photoinitiators [camphorquinone (CQ), diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO) and phenylbis (2,4,6-trimethylbenzoyl)-phosphine oxide (BAPO)], using second or third-generation light curing units (LCU), and to evaluate the degree of conversion and the physical properties of an experimental resin adhesive. Material and methods: Second-generation (Radii-cal® and Emitter D®) and third-generation (Valo® Cordless and Bluephase N®) LCU were assessed regarding spectrum and irradiance rate of emitted light. Also, the photoinitiators (CQ, TPO and BAPO) were characterized by a light absorption spectrum assessed by UV-Vis spectroscopy, degree of conversion and yellowing effect. Statistical analyzes considered two-way ANOVA and post-hoc Tukey test. Results: BAPO presented higher reactivity compared to TPO. Regarding degree of conversion of the photoinitiators activated by different light-curing units, the Emitter D® device promoted a high degree of conversion. BAPO presented the highest yellowing effect values. Conclusions: The emission and absorption characteristics of the photoinitiators were different. The polymerization reaction activated by the second-generation light-curing unit was reduced when using an experimental resin with photoinitiator TPO, and the third-generation light-curing unit showed a higher polymerization potential regardless of the photoinitiator. Keywords Light-curing of dental adhesives; Photoinitiators dental; Curing lights dental.

The effects of polymerization mode and layer thickness on monomer released from bulk fill composite resins.

Residual monomers released from composite resins have cytotoxic, mutagenic, and estrogenic effects. Mode of polymerization and application thickness are important for monomer release. The aim of this study was to investigate the effects of different modes of a third-generation light-curing unit (LCU) and layer thickness on residual monomer released from two different bulk-fill composite resins. A total of 80 samples were prepared for each bulk-fill composite using a mold. Each bulk-fill composite was divided into four groups according to polymerization mode (standard and extra power) and layer thickness (2 and 4 mm). In addition, four groups were divided into four subgroups according to time periods (1 h, 24 h, 3 days, and 7 days). The samples were polymerized with VALO LED device. The amount of residual monomer was measured with High-Performance Liquid Chromatography (HPLC). All statistical analyses were processed using SPSS Version 23.0. The normal distribution of data was confirmed using Kolmogorov-Smirnov Normal Distribution Test and Shapiro-Wilk Normal Distribution Test. When the distribution was normal, parametric tests, Student's t test and one-way ANOVA, were used. When the distribution was not normal, non-parametric tests, Mann-Whitney U test, and Kruskal-Wallis testwere used. It was found that the standard mode of LCU produced lower amounts of TEGDMA, Bis-GMA, and UDMA in both composite materials. In addition, when the layer thickness increased, TEGDMA, Bis-GMA, and UDMA releases increased, too. This study revealed that the amount of residual monomers released from bulk-fill composites was affected by layer thickness and polymerization time.

Light-curing units used in dentistry: Effect of their characteristics on temperature development in teeth.

This study aimed to investigate pulp chamber and surface temperature development using different LED light curing units (LCUs). Eight brands of LED-LCUs were tested in a laboratory bench model. The pulp chamber and surface temperature were recorded with a type T thermocouple and infrared cameras, respectively. The highest pulp chamber and surface temperature increase was 6.1±0.3°C and 20.1±1.7°C, respectively. Wide-spectrum LED-LCUs produced higher pulp chamber temperature increase at 0 mm and 2 mm but lower at 4 mm. Narrow-spectrum LED-LCUs produced higher surface temperature increase. LED-LCU featuring modulated output mode resulted in lower increase in pulp chamber temperature but higher on surface temperature. LED-LCU with light guide tip delivering an inhomogeneous beam caused higher increase in temperature on the surface and in the pulp chamber. LED-LCUs with different spectral emission, output mode and light guide tip design contributed to different temperature development in the pulp chamber and at the surface of teeth.

‘Let there be Light,’ and there was Light, but was it Enough? A Review of Modern Dental Light Curing

Light curing, or photopolymerization, is a very common method of effecting the set of resin-containing dental materials. This review summarizes key aspects that influence optimal photopolymerization, and how both a basic knowledge of chemistry and properties of the light-curing device are essential to achieve optimal clinical performance of the material. Tips are offered with respect to both the light-curing units and those materials which are cured by them to ensure best practice when working clinically. CPD/Clinical Relevance: A thorough knowledge and understanding of photopolymerization is critical to clinicians given that many dental materials in contemporary use are cured by this means.

Choosing a Light-curing Unit

Choosing a Light-curing Unit

Beam Profiling of Dental Light Curing Units Using Different Camera-Based Systems.

Objective This study aimed to perform the beam profile of dental light-curing units (LCUs) using mirrorless and smartphone cameras and correlate it to a camera-based laser beam profiling system. Materials and Methods Three LCUs were evaluated (Radii Plus; Bluephase G2; and VALO Cordless). The spectral power of the LCUs was measured by using a spectrophotometer. The light emitted from the LCUs was projected onto a glass diffuser, and the images were recorded by using a mirrorless camera (NEX-F3), a smartphone (iPhone) and a camera-based beam profiler. Bandpass optical-filters were used, and for each LCU, the total spectral power output was integrated to calibrate the images. Statistical analysis was performed by digital image correlation (pixel by pixel) using Pearson’s correlation (α = 0.05; β = 0.2). Results The beam profile images showed nonuniform radiant emittance and spectral emission distributions across all the LCUs light tip. A strong correlation was found among cameras (Pearson’s r = 0.91 ± 0.03 with 95% confidence interval [CI]: 0.88–0.94 for the NEX-F3 and Pearson’s r = 0.88 ± 0.04 with 95% CI: 0.84–0.92 for the iPhone). Conclusion The standard Ophir beam profile system presented the most accurate distribution, but the mirrorless and smartphone cameras presented a strong correlation in the irradiance distribution of the beam profile images. Alternative cameras can be used to perform light beam profile of dental LCUs, but caution is needed as the type of sensor, image bit depth, and image processing are important to obtain accurate results.

Improper Light Curing of Bulkfill Composite Drives Surface Changes and Increases S. mutans Biofilm Growth as a Pathway for Higher Risk of Recurrent Caries around Restorations.

How dentists cure a resin-based material has deleterious effects on the material’s properties and its interaction with surrounding dental tissues. Biofilm accumulation has been implicated in the pathogenesis of carious lesions around dental restorations, with its composition manifesting expressed dysbiosis in patients suffering from dental caries. To evaluate the influence of varying radiant exposure on the degree of conversion (DC%), Streptococcus mutans biofilm growth, and surface roughness of bulk-fill composites under different light-curing conditions. Two light-curing units (LCU) at 600 and 1000 mW/cm2 were used to simulate curing conditions with different angulations (∢20° and ∢35°) or 2 mm-distance displacements of the LCU tip. The radiant exposure (RE) was assessed, and the composites were analyzed for DC%. Biofilm formation was induced over the bulk-fill composites and analyzed via colony-forming units counting and scanning electron microscopy (SEM). The surface roughness was analyzed via a profilometer and SEM after biofilm formation. Curing conditions with different angulation or displacement decreased RE compared to the “optimal condition”. The moderately (∢35°) angulated LCU tip and low (600 mW/cm2) radiant emittance significantly reduced the DC% (p < 0.05). The difference in DC% between the top and bottom of the composites ranged from 8 to 11% for 600 mW/cm2 and 10 to 20% for 1000 mW/cm2. Greater S. mutans biofilm and surface changes were found in composites with non-optimal RE delivery (e.g., tip displacement and angulation) (p < 0.05). Inadequate polymerization of bulk-fill composites was associated with more biofilm accumulation and surface topography changes. Overall, non-optimally performed curing procedures reduced the amount of delivered RE, which led to low DC%, more biofilm formation, and higher surface roughness. The improper light-curing of bulk-fill composites compromises their physicochemical and biological properties, which could lead to inferior clinical performance and reduced restorative treatments’ longevity.

Wear Resistance of Bulk-Fill Dental Resins Cured by Different Light-Curing Settings

PurposeThe aim of this study was to investigate the wear behaviour of dental bulk-fill resins cured under different light-curing settings. Material and MethodsFour different materials investigated (Filtek, Beautifil, Admira, Powerfill) and cured with a light-curing unit at different curing settings and time. The wear loss of each material was investigated simulating 6- and 12-months wear in vivo, using a universal wear testing machine (UFW200) in a two-body dry wear with linear reciprocation design. Surface hardness also evaluated using nanoindentaion system. The worn surfaces were analysed under Scanning Electron Microscopy. Collected data was analysed statistically with one-way ANOVA and post hoc test. ResultsPowerfill resin showed the least wear loss (0.07 ± 0.03 mm), followed by Filtek specimens (0.09 ± 0.03 mm), whereas Beautifil resin showed the highest amount of wear loss (0.14 ± 0.05). The highest to lowest nanohardness in 3 s cured specimens were showed by Filtek, Powerfill, Admira, Beautifil (highest 0.66 ± 0.10 GPa, lowest 0.62 ± 0.16 GPa). SEM analysis suggested a wear mechanism of stress-induced cracking. ConclusionResin type has the most significant influence on wear behaviour. Increasing filler weight can negatively influence the wear resistance of bulk-fill resins. No correlation was found between wear resistance and surface hardness.

Effect of an elastomeric urethane monomer on BisGMA-free resin composites containing different co-initiators.

The aim of this study was to investigate the mechanical, chemical, optical, and adhesive properties of BisGMA-free experimental resin composites containing Exothane-24-an elastomeric urethane monomer-and different co-initiators. A blend of urethane dimethacrylate (UDMA), extended dimethacrylate urethane (PEG 400), triethylene glycol dimethacrylate (TEGDMA), and camphorquinone was prepared. Two different co-initiators-dimethyl aminoethyl methacrylate (DMAEMA) or 4-N alcohol, N-dimethylamine phenylethyl (DMPOH)-were added to the blend. Exothane-24 monomer was added to the blend for each co-initiator and four groups were established as follows: DMAEMA; DMAEMA + Exothane; DMPOH; and DMPOH + Exothane. Specimens were photo-activated using a multi-wave LED light-curing unit (VALO; 954 mW/cm2 of irradiance). Mechanical (ultimate tensile strength, flexural strength, flexural modulus and hardness), chemical (degree of conversion, hardness reduction, water sorption and solubility), optical (color change), and adhesive (microtensile bond strength) properties were analyzed. Data were submitted to two-way ANOVA and Tukey's test (α = 0.05). The resin composite containing DMPOH and Exothane-24 showed similar or superior performance to those of the other experimental composites for mechanical and chemical properties, except for flexural strength. It also showed less color change and greater micro-tensile bond strength. Among the combinations tested, the BisGMA-free resin composite containing Exothane-24 combined with the DMPOH co-initiator showed the best mechanical, chemical, optical, and adhesive properties. Clinical relevance Exothane-24 monomer and DMPOH co-initiator could be useful in the formulation of BisGMA-free resin composites in order to minimize exposure to BPA.

Effect of light curing unit and antiseptic mouthwashes on the physical properties of gingiva-colored composite resin

Objective: This study evaluated surface roughness (Ra) and color difference (ΔE00) of a gingiva-colored composite resin (NT Premium Gengiva, Coltene), light-activated with three light curing units (LCU) and immersed in different mouthwash solutions. Methods: 90 composite specimens (n=10) were divided according to the LCU: L1-Valo, L2-Bluephase and L3-Optilight Max; and solution: S1-alcohol-based antiseptic mouthwash (Listerine Cool Mint), S2-alcohol-free antiseptic mouthwash (Listerine Cool Mint Zero Alcohol) and S3-water (control). Immersions were performed for 30 s, 2x/day, for 21 days. Ra and coordinates of luminosity (L*) and color (a* and b*) were measured using a rugosimeter (SJ-201 P/M) and a spectrophotometer (SP62S), respectively, at: T0-start, T1-7 days, T2-14 days and T3-21 days. Results: L1 (1.3±0.9) presented higher Ra than L3 (0.7±0.6) and L2 (1.0±0.8); and Ra for S2 (0.9±0.1) was greater than S3 (-0.1±0.1), and S1 (0.1±0.1). Moreover, L1 (23.3±0.3) presented lower ΔE00 t han L 2 (24.7±0.3) a nd L 3 (25.1±0.3). Conclusion: Ra of the gingiva-colored composite resin tested increased when L1 and S2 were used, although L1-cured specimens also showed the lowest ΔE00.

High-Power LED Units Currently Available for Dental Resin-Based Materials-A Review.

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/cm2) 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/cm2 up to 6000 mW/cm2) were identified. Most output values vary on 2000–3000 mW/cm2. The highest output found was 6000 mW/cm2, 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.

Knowledge and Attitude of Dental Clinicians towards Light-Curing Units: A Cross-Sectional Study.

Objectives Light curing is crucial when applying composite resin restorations. Complete polymerization of the resin depends on delivering adequate light energy to it. Dental clinicians may be unaware of the importance of proper light-curing techniques. This study aimed at evaluating and comparing the level of knowledge of general practitioners (GPs) and specialists (SPs) regarding light-curing units. Materials and Methods An electronic survey was conducted online among GPs and SPs of various specialties, working in the governmental sector in Riyadh, Saudi Arabia. Collected data were analyzed for statistical significance. Results 310 dentists were included in the study. Nearly half of the GPs (45.9%) and more than half of SPs (56.8%) use light-emitting diode (LED) type light-curing units (LCUs). 36.9% of GPs and 29.6% of SPs were unsure about the type of LCUs they use in their dental clinics. 10.8% of GPs and 8.5% of SPs knew the proper term of the power output of LCU. 52.2% of the GPs and 55.7% of SPs were wrong about advancements in technology of LED LCUs. Regarding the use of radiometer, 48.2% of SPs and 35.1% of GPs had responded wrongly, and 37.7% of SPs and 52.3% of GPs were not familiar with the device, showing a statistical significance (p=0.040). There was no statistical significance observed in the responses pertaining to their years of experience, expected for two questions. Conclusion Both GPs and SPs displayed inadequate knowledge regarding the use of LCUs. Further educational programs are recommended to spread awareness about the handling of LCUs among dental clinicians.

Assessment of Streptococcus mutans biofilms on orthodontic adhesives over 7 days

The purpose of this study was to compare the metabolism of Streptococcus mutans biofilms after 1-7days of growth on different orthodontic adhesives. Specimens of 6 commercial orthodontic adhesives were fabricated in custom-made molds and polymerized using a light-emitting diode light-curing unit. Bioluminescent S mutans (UA159:JM10) biofilms were grown on ultraviolet-sterilized specimens for 1, 3, 5, and 7days (n=18 biofilms/d/product) in anaerobic conditions at 37°C. The metabolism of biofilms (relative luminescence unit [RLU]) was measured 0, 2, 4, and 6minutes after exposure to D-luciferin solution using a microplate reader. A linear mixed-effects model was used to analyze the logarithm of RLU (log RLU). The model included fixed effects of products, days, and minutes. Tukey-Kramer post-hoc tests were then performed on the significant predictors of log RLU (α=0.05). Days (P<0.0001) and minutes (P<0.0001) were independent predictors of log RLU, but the products were not (P=0.5869). After adjusting for minutes, the log RLU was analyzed with a post-hoc test, and all differences between days were significant with the exceptions of day 3 from day 5 (P=0.0731) and day 5 from day 7 (P=0.8802). After adjusting for day, log RLU was analyzed with a post-hoc test and all differences in minutes were significant. No significant differences in the metabolism of S mutans biofilms were observed among the 6 orthodontic adhesives. Biofilms that were grown for 3days demonstrated the highest levels of biofilm metabolism as evidenced by higher mean log RLU values relative to 1, 5, and 7-day growth durations.

A measurement of irradiance of light-curing units in dental offices in three Croatian cities.

Aim To determine irradiance of light-curing units (LCUs) in dental offices in three Croatian cities and to compare irradiance values with the age and model of LCUs. Methods Private and public dental offices in three most prominent cities in Croatia (Rijeka, Split and Zagreb) were included in this study. In total, 195 LCUs were tested, using radiometer Ivoclar Bluephase Meter 2 for irradiance (mW/cm2 ). The minimum acceptable value was set at 400 mW/cm2 . The age, model and difference between declared and measured irradiance of the LCUs were also determined. Of the total of 195 LCUs, 190 (98%) were LED (light-emitting diode) and 5 (2%) were QTH (quartz-tungsten - halogen). Results The mean age of tested LCUs was 4.43±3.4 years; the oldest was in Rijeka, 5.2±3.8 years. The overall mean irradiance for all three cities was 806.4 mW/cm2 (p=0.0004). Of all LCUs, 11.3% were considered clinically unacceptable with irradiance of less than 400 mW/cm2 . Of all tested LCUs 42% (p=0.0005) had a 30% lower value of irradiance than the manufacturer of the LCU declared. In 73% tested LCUs, there was a matching between measured and declared irradiance. The age and model of LCUs had the most significant impact on irradiance. Conclusion The most commonly used LCU included in dental offices was LED. Mean irradiance was good enough to secure adequate polymerization of resin-based materials. Irradiance decreases with usage time of LCU.

Microhardness homogeneity of RBCs light-cured with a multiple-peak LED and surface characterization after wear.

This in vitro study evaluated the effect of the beam homogeneity of a multiple-peak light-curing unit on the surface microhardness and the effect of toothbrushing wear on the microhardness, surface roughness, roughness profile, volume loss, and gloss retention of incremental and bulk-fill resin-based composites (RBCs). A LED light-curing unit (VALO) with four LEDs at the tip end (405, 445, 465A, and 465B nm emission peak) was used according to each manufacturer-recommended time to obtain disks (n=10) of six RBCs: Estelite Sigma Quick, Charisma Classic, Tetric EvoCeram Bulk Fill, Filtek Z250, Filtek Supreme Ultra, and Filtek Bulk Fill. Microhardness values were obtained according to each LED positioning of the light-curing unit on the top surface of the RBCs and were analyzed before and after toothbrushing regarding microhardness, surface roughness, roughness profile, volume loss, and gloss retention. Microhardness was considered homogeneous on the top surface regardless of the type of RBC or wavelength tested (p>0.05). Overall, toothbrushing did not reduce the microhardness of the RBCs but influenced the gloss values for most RBCs (p<0.001). Charisma Classic presented the greatest surface roughness and roughness profile after toothbrushing (p<0.05). Volume loss did not differ among RBCs (p>0.05). In conclusion, different wavelengths of the LED did not affect the top surface microhardness, regardless of the RBCs tested; and bulk-fill composites presented similar surface changes (microhardness, surface roughness, roughness profile, volume loss, and gloss retention) when compared to conventional composites after toothbrushing.

Comparison of temperature rise within pulp chamber during light curing of composite restoration

AbstractIn this study, total of 60 extracted human teeth were divided into four groups. Group I and II were subjected to LCU A (2550 mW/cm2) and Group III and IV to LCU B (700 mW/cm2), respectively. The increase in temperature level from baseline was recorded using K type thermocouple while curing of dentin bonding agent and composite resins. The temperature rise was significantly higher for Light Curing Unit A which had higher intensity light than Light Curing Unit B. Remaining dentin thickness of the prepared tooth also has significant role in the temperature rise. Hence, light curing units should be used with caution to avoid over‐exposure of teeth. Dental practitioners need to prepare teeth with silicone indices and pre‐assessment of radiographs to avoid over‐preparation. Regular check of intensity of light curing unit using commercially available intensity meter is advocated.

Light and viscosity effects on the curing potential of bulk-fill composites placed in deep cavities.

To determine the influence of light curing units (LCUs) and material viscosity on the degree of conversion (DC) of bulk-fill (BF) resin-based composites (RBCs) placed in deep cavity preparations. Four LCUs were tested: Valo cordless, Bluephase-G2, Poly wireless and Radii-cal. Light irradiance was determined at 0mm and 6mm distance to the reading sensor. The following RBCs were considered: Filtek BF, Filtek BF Flow, Opus BF, Opus BF Flow, Tetric N-Ceram BF and Surefil SDR Flow. Sirius-Z was used with the incremental technique. DC (n = 3) was evaluated by spectroscopy both at top and bottom regions of deep preparations with 6mm depth. The data were submitted to ANOVA and Tukey's test (α = 0.05). Pearson's correlation (95%) was used to verify the relation between the LCUs and the curing potential of RBCs. The DC at 6mm depth was reduced when Opus BF, Opus BF Flow and Tetric N-Ceram BF were activated with Radii-cal. There was a positive correlation between the LCU irradiance and the bottom/top conversion ratios. The materials' viscosities did not affect the curing potential. Bulk-fill composites did not present higher curing potential than the conventional composite used with the incremental technique; the most important aspect of the LCU was the irradiance ratio; and the materials' viscosity did not affect the curing potential as a function of depth. Radii-cal negatively impacted the degree of conversion at 6mm depth for most bulk-fill resin composites. Depending on the brand, bulk-fill composites may present reduced curing potential due to the light source when placed in deep cavities. Dentists should avoid LCU with acrylic tips to photoactivate bulk-fill resin-based composites.

Utilizing Light Cure Units: A Concise Narrative Review.

The use of photo-curable resin composite restorations is an essential treatment modality in modern dental practice. The success and longevity of these restorations depend on achieving predictable and effective polymerization. Understanding the dynamics of the polymerization and the effect of light cure units (LCUs) on this process is paramount. The goal of this concise narrative review is to provide a simplified presentation of basic principles of composite chemistry, polymerization reactions, and photo-curing with relevant terminologies. Clinical guidelines for choosing and maintaining LCUs, as well as safety precautions and factors under the control of the clinician are listed. Finally, clinical recommendations of LCUs’ usage and monitoring are included to aid practitioners in achieving predictable polymerization during the placement of direct resin composite restorations.

Relationship Between the Cost of 12 Light-curing Units and Their Radiant Power, Emission Spectrum, Radiant Exitance, and Beam Profile.

To correlate the radiant power (mW), radiant exitance (or tip irradiance in mW/cm2), emission spectrum (mW/cm2/nm), and beam irradiance profile of 12 light-curing units (LCUs) available in the Brazilian market with their market cost. Six LCUs that cost more than US$900 (Bluephase G4,VALO Grand, VALO Cordless, Radii Xpert, Elipar DeepCure-S, and Radii plus) and six low-cost LCUs costing less than US$500 (Radii Cal, Optilight Max, High Power LED 3M, Emitter D, Emitter C, and LED B) were examined. Radiant power (mW) and emission spectrum (mW/nm) were measured using an integrating sphere connected to a fiber-optic spectroradiometer. The internal tip diameter (mm) of each LCU was measured using a digital caliper and was used to calculate the average radiant exitance (mW/cm2). Irradiance profiles at the light tip were measured using a commercial laser beam profiler. The cost of each LCU in Brazil was correlated with internal tip diameter, radiant power, and tip irradiance. None of the low-cost LCUs were broad spectrum multiple peak LCUs. There was no correlation between the cost of the LCUs and their averaged tip irradiance; however, there was a high positive correlation between the cost of the LCUs and the radiant power and tip diameter. The VALO Grand, Elipar DeepCure-S, VALO Cordless, and Bluephase G4 all emitted a higher radiant power. They also had a significantly greater tip diameter than other LCUs. For the LCUs with a nonuniform output, some areas of the light tip delivered less than 400 mW/cm2, while other areas delivered more than 2500 mW/cm2. In general, LCUs that had a higher cost (US$971-US$1800) delivered more power (mW) and had a greater tip diameter (mm), which covered more of a tooth. In general, the low-cost LCUs (US$224-US$470) emitted a lower radiant power and had a smaller tip diameter.