LED Light-curing Unit Research Articles

Kendinden bağlanabilen rezin simanlardan salınan monomerlerin HPLC ile incelenmesi

OBJECTIVE: The aim of this study was to determine the residual monomer leaching from two self-adhesive resin cements polymerized with Light Emitting Diode (LED) or halogen light curing unit. MATERIALS AND METHOD: Clearfil SA (group A, n = 48) and BisCem (group B, n = 48) cements were inserted in plastic moulds. Each group was further divided into two subgroups. Specimens were light cured with LED light curing unit (LCU) in group A1 and group B1 and halogen LCU in group A2 and group B2 for 20 seconds. The following compounds released from the samples stored in distilled water were analyzed: triethylene glycol-dimethacrylate (TEGDMA) and bisphenol A glycidyl methacrylate (Bis-GMA). Analysis of substances was performed with the use of high performance liquid chromatography, after 1 hour and 24 hour incubation periods. Factorial experimental design and independent t -test was used for statistical analyses. RESULTS: Self-adhesive resin cements released more Bis-GMA and TEGDMA when they were polymerized with LED LCUs (p 0.05). Clearfil SA cement released more Bis-GMA than BisCem (p<0.05). BisCem released more TEGDMA than Clearfil SA (p<0.05). CONCLUSION: The results of this study showed that the quantity of Bis-GMA and TEGDMA leached from self-adhesive resin cements was influenced by the type of LCU and by the type of self-adhesive resin cement.

Residual monomer release from orthodontic adhesives cured with different light sources

Introduction: The aim of this study was to evaluate the residual monomer release from orthodontic adhesives cured with light-emitting diode (LED) and halogen light sources.Methods: Seven hundred and twenty stainless steel brackets were divided into 3 groups according to the adhesive system used (Transbond XT light-cure adhesive [TXT], Transbond LR capsule [LR], and Light Bond light-cure adhesive paste [LB]), and each group was divided into 2 subgroups according to light-curing procedure (LED or halogen). Brackets were bonded with adhesives onto tooth buccal surfaces and polymerized. Each specimen contained 24 brackets that simulated the oral environment (n = 5). The specimens were immersed in a 75% ethanol/water solution at 37 °C for 10 min, 1 h, 1 d, 7 d, 14 d, and 30 d, respectively. Eluted monomers (Bis-GMA, UDMA, and TEGDMA) were detected using HPLC.Results: There was residual monomer release at all time periods, and the highest amount of release was observed cumulatively on the 30th day. The cumulative Bis-GMA released from adhesives was not different (p > 0.05). The cumulative TEGDMA released from adhesives was statistically different (p < 0.05). There was no statistical difference between QTH and LED light-curing units for each adhesive (p > 0.05).Conclusions: The release of residual monomers stays at a high level for a long time after polymerization. The total leaching of residual monomers from the Light Bond light-cure sealant resin plus Light Bond light-cure adhesive paste was higher than that of other materials for both curing units. Different curing units (LED or QTH) did not affect the monomer release from the orthodontic adhesives.

Comparison of the bonding strengths of second- and third-generation light-emitting diode light-curing units.

ObjectiveWith the introduction of third-generation light-emitting diodes (LEDs) in dental practice, it is necessary to compare their bracket-bonding effects, safety, and efficacy with those of the second-generation units.MethodsIn this study, 80 extracted human premolars were randomly divided into eight groups of 10 samples each. Metal or polycrystalline ceramic brackets were bonded on the teeth using second- or third-generation LED light-curing units (LCUs), according to the manufacturers’ instructions. The shear bond strengths were measured using the universal testing machine, and the adhesive remnant index (ARI) was scored by assessing the residual resin on the surfaces of debonded teeth using a scanning electron microscope. In addition, curing times were also measured.ResultsThe shear bond strengths in all experimental groups were higher than the acceptable clinical shear bond strengths, regardless of the curing unit used. In both LED LCU groups, all ceramic bracket groups showed significantly higher shear bond strengths than did the metal bracket groups except the plasma emulation group which showed no significant difference. When comparing units within the same bracket type, no differences in shear bond strength were observed between the second- and third-generation unit groups. Additionally, no significant differences were observed among the groups for the ARI.ConclusionsThe bracket-bonding effects and ARIs of second- and third-generation LED LCUs showed few differences, and most were without statistical significance; however, the curing time was shorter for the second-generation unit.

Effect of a broad-spectrum LED curing light on the Knoop microhardness of four posterior resin based composites at 2, 4 and 6-mm depths

ObjectiveTo measure the Knoop microhardness at the bottom of four posterior resin-based composites (RBCs): Tetric EvoCeram Bulk Fill (Ivoclar Vivadent), SureFil SDR flow (DENTSPLY), SonicFill (Kerr), and x-tra fil (Voco). MethodsThe RBCs were expressed into metal rings that were 2, 4, or 6-mm thick with a 4-mm internal diameter at 30°C. The uncured specimens were covered by a Mylar strip and a Bluephase 20i (Ivoclar Vivadent) polywave® LED light-curing unit was used in high power setting for 20s. The specimens were then removed and placed immediately on a Knoop microhardness-testing device and the microhardness was measured at 9 points across top and bottom surfaces of each specimen. Five specimens were made for each condition. ResultsAs expected, for each RBC there was no significant difference in the microhardness values at the top of the 2, 4 and 6-mm thick specimens. SureFil SDR Flow was the softest resin, but was the only resin that had no significant difference between the KHN values at the bottom of the 2 and 4-mm (Mixed Model ANOVA p<0.05). Although the KHN of SureFil SDR Flow was only marginally significantly different between the 2 and 6-mm thickness, the bottom at 6-mm was only 59% of the hardness measured at the top. Clinical significanceThis study highlights that clinicians need to consider how the depth of cure was evaluated when determining the depth of cure. SureFil SDR Flow was the softest material and, in accordance with manufacturer’s instructions, this RBC should be overlaid with a conventional resin.

Color Stability of Two Bulk-Fill Composite Resins

Objective: Bulk-fill composites are a group of composite resins designed for easy and fast filling of large cavities. This study aimed to assess the color stability of bulk-fill composites subjected to xenon radiation and evaluate their color change (ΔE) following polymerization.Methods: In this in vitro experimental study, 30 specimens (4mm in height and 8mm in diameter) were fabricated of x-traFil and Tetric N-Ceram universal color bulk-fill composites and A2 shade of Grandio composite (as control). Bulk-fill composites were placed in the mold in 4mm thickness according to the manufacturers’ instructions. In the control group, composite was applied to the mold in two layers each with 2mm thickness. Tetric and Grandio composites were cured for 20 seconds and x-traFil was cured for 10 seconds with a LED light-curing unit. A total of 15 specimens (five of each composite) were used for each test. For assessment of color change due to polymerization, L*, a* and b* color parameters were measured before and immediately after polymerization and also 30 days after immersion in distilled water in an incubator at 37°C and 70% humidity using a spectroradiometer. For xenon test, the specimens were subjected to color analysis after 48 hours of storage in distilled water. Next, they were subjected to xenon lamp radiation in xenon environment chamber for 122 hours at 22°C and 25% humidity and then the color parameters were measured again. The mean and standard deviation (SD) of all values were calculated. One-way and repeated measures ANOVA were used to compare ΔE and ΔL among the groups. Tukey’s HSD test was used for pairwise comparisons.Results: The value of ΔE immediately after polymerization was the lowest for Grandio (4.91) and the highest for Tetric (9.44). Thirty days after the polymerization, ΔE was the lowest in Grandio (3.07) and the highest in Tetric (9.27); ΔE showed a decreasing trend over time in all specimens. Under xenon light radiation, Grandio showed the lowest (1.50) and Tetric showed the highest ΔE (11.15).Conclusion: Following polymerization and under xenon lamp radiation, ΔE of conventional composite was less than that of bulk-fill composites.

Temperature changes caused by light curing of fiber-reinforced composite resins.

Objective:The aim of the study is to evaluate temperature change in fiber-reinforced composite (FRC) resin photopolymerized with a light-emitting diode (LED) light-curing unit (LCU).Materials and Methods:Forty dentine disks (1 mm thick and 8 mm diameter) were prepared from human molars. The FRC specimens (2 mm thickness and 8 mm diameter) consisted of polyethylene fiber (Construct (CT)) products or glass fiber (ever Stick (ES)) and one hybrid composite bonded to the dentin disks and polymerized with an LED LCU. Control groups were prepared using the hybrid composite. Temperature rise in dentine samples under the FRC bonded disks was measured using a K-type thermocouple, and data were recorded. Temperature change data were subjected to analysis of variance (ANOVA) and Duncan's test.Results:The results show that addition of fiber (one or two layers) did not change temperature rise values at any of the exposure times (P > 0.05). The CT fiber/two layer/40 s group exhibited the greatest temperature rise (5.49 ± 0.62) and the ES/one layer/10 s group the lowest rise (1.75 ± 0.32). A significant difference was observed in temperature rise measured during 10 and 20 s exposures (P < 0.05).Conclusion:Maximal temperature rise determined in all groups was not critical for pulpal health, although clinicians need to note temperature rises during polymerization.

Effects of prolonged light exposure times on water sorption, solubility and cross-linking density of simplified etch-and-rinse adhesives.

This study evaluated the effects of light exposure times on water sorption, solubility, and polymer cross-linking density of simplified etch-and-rinse adhesives. Four commercial adhesives (XP Bond, Adper Single Bond 2, Tetric N-Bond, and Ambar) were selected, and resin disks 5 mm in diameter and 1.0 mm thick were prepared and light cured for 20, 40, or 80 s using an LED light-curing unit at 1200 mW/cm2. Water sorption and solubility were evaluated over a 28-day period. For polymer cross-linking density, additional specimens were prepared and their Knoop hardness measured before and after immersion in 100% ethanol. The data from each test were evaluated using a two-way ANOVA and Tukey's test (α = 0.05). The XP Bond adhesive showed higher water sorption (similar to Adper Single Bond 2) and solubility (p < 0.05) than did the other materials. Prolonged exposure times did not reduce the water sorption but did reduce the solubility of all tested materials (p < 0.05). For Ambar, the increase in the exposure time resulted in a significantly lower percent reduction in hardness. Water sorption, solubility, and cross-linking density of the materials selected in this study seem to be mainly influenced by the adhesive composition. Prolonged light exposure times reduced the solubility of the materials.

In vitro investigation of heat transfer phenomenon in human immature teeth.

Background and aims. Heat generated within tooth during clinical dentistry can cause thermally induced damage to hard and soft components of the tooth (enamel, dentin and pulp). Geometrical characteristics of immature teeth are different from those of mature teeth. The purpose of this experimental and theoretical study was to investigate thermal changes in immature permanent teeth during the use of LED light-curing units (LCU).Materials and methods. This study was performed on the second mandibular premolars. This experimental investiga-tion was carried out for recording temperature variations of different sites of tooth and two dimensional finite element models were used for heat transfer phenomenon in immature teeth. Sensitivity analysis and local tests were included in the model validation phase. Results. Overall, thermal stimulation for 30 seconds with a low-intensity LED LCU increased the temperature from 28°C to 38°C in IIT (intact immature tooth) and PIT (cavity-prepared immature tooth). When a high-intensity LED LCU was used, tooth temperature increased from 28°C to 48°C. The results of the experimental tests and mathematical modeling illustrated that using LED LCU on immature teeth did not have any detrimental effect on the pulp temperature. Conclusion. Using LED LCU in immature teeth had no effect on pulp temperature in this study. Sensitivity analysis showed that variations of heat conductivity might affect heat transfer in immature teeth; therefore, further studies are required to determine thermal conductivity of immature teeth.

Comparative Evaluation of Shear Bond Strength and Debonding Characteristics using Conventional Halogen Light Curing Unit and LED Light Curing Unit: An in vitro Study

Comparative Evaluation of Shear Bond Strength and Debonding Characteristics using Conventional Halogen Light Curing Unit and LED Light Curing Unit: An in vitro Study

Prototype of a new tip developed to be coupled to dental light-curing units for optimizing bonding of orthodontic brackets and accessories

Development of a new device to be coupled to light-curing units for bonding orthodontic brackets and accessories, and test its efficacy in an in vitro mechanical trial. The inner surface of the device is mirrored and is based on physical concepts of light refraction and reflection. The main advantage of such device is the reduced clinical time needed for bonding and the low possibility of contamination during the process. One hundred and twenty specimens were used for testing the shear bond strength of brackets bonded with the device. The Adhesive Remnant Index (ARI) was also determined. The sample was divided into 2 groups. In group 1 a halogen light-curing unit was used while in group 2 a led light-curing unit was used. Each group was then subdivided. In subgroups H1 and L1, a conventional light guide rod was used while in subgroups H2 and L2 bonding was performed with the mirrored device coupled to the tip of the guide light rod. The values obtained for the shear bond strength and the ARI in the subgroups were compared. Results showed that there was no statistically significant difference for the shear strength (p > 0.05) and the ARI (p > 0.05) between the subgroups. The tests of mechanical trials and the ARI analysis showed that the new device fulfilled the requirements for bonding orthodontic accessories, and that the time for bonding was reduced to half, being necessary only one light exposure.

Comparative Evaluation of Shear Bond Strength and Debonding Characteristics using Conventional Halogen Light Curing Unit and LED Light Curing Unit: An�in vitro�Study

Aim: The purpose of this study was to compare the shear bond strength of orthodontic brackets bonded to teeth with conventional halogenbased light curing units and commercially available LED curing units. LED light curing unit (Apoza) and halogen-based light curing unit (Q-Lux) were tested. Materials and methods: Specimens consisted of one hundred twenty human maxillary premolar on which stainless steel brackets were bonded with a light-cured adhesive system (Transbond XT; 3M Unitek). The specimens were divided into 6 groups of 20 teeth each. Three groups were exposed to halogen light for 10, 20, 40 seconds and the other three groups were cured with the LED light for 10, 20, 40 seconds respectively. The specimens were stored in water at 37°C for 24 hours and then tested for shear bond strength with an Instron universal testing machine at a cross head speed of 1 mm/min until the bracket debonded. The results were subjected to Kaplan meier survival analysis (p = 0.0001 sig). Results: The findings indicated no significant differences in the shear bond strength between the conventional halogen light and the commercially available LED-curing unit when the exposure time was 20 and 40 seconds. However, both halogen and LED lights displayed inadequate bond strength when the curing time was 10 seconds. Chi-square analysis detected no difference in the adhesive remnant index scores of the 6 groups (p = 0.0996). Conclusion: The result of this study showed promise for the orthodontic application of LED as light curing units and 20 seconds of exposure

Effects of different light sources on microleakage of composite resins with different monomer structures

Background/purposeThe aim of this study was to investigate the effects of different light curing units (LCUs) on the microleakage of different composite resins. Materials and methodsForty-five freshly extracted human third molars were selected for this study. Standardized class V cavities were prepared on the buccal and lingual surfaces of each tooth. The teeth were randomly divided into three composite resin groups, comprising two dimethacrylate-based hybrid composites and a silorane-based composite. Each composite resin group was randomly divided into three subgroups for curing with three different LCUs (n = 5). Of the three different LCUs used, one was quartz–tungsten–halogen and two were light-emitting diodes (LEDs) with different power outputs. The teeth were immersed in a 2% methylene blue dye solution and examined under a stereomicroscope. Results were statistically analyzed using Kruskal–Wallis and Dunn tests. ResultsWhen all composite resin groups were compared, the lowest marginal leakage scores were obtained with the Filtek Silorane composite group, and they statistically significantly differed from those of the other groups (P < 0.05). Among all groups, the lowest marginal leakage value was obtained for the LED 1055 subgroup of the Filtek Silorane composite group, and the highest marginal leakage value was obtained for the quartz–tungsten–halogen subgroup of the Aelite Aesthetic Enamel composite group. ConclusionIt was concluded that it is not possible to entirely prevent microleakage, but it can be minimized with silorane-based composite resins and high-density-output LED LCUs.

FT-Raman Spectroscopy Study of Organic Matrix Degradation in Nanofilled Resin Composite

This in vitro study evaluated the effect of light curing unit (LCU) type, mouthwashes, and soft drink on chemical degradation of a nanofilled resin composite. Samples (80) were divided into eight groups: halogen LCU, HS--saliva (control); HPT--Pepsi Twist®; HLC--Listerine®; HCP--Colgate Plax®; LED LCU, LS--saliva (control); LPT--Pepsi Twist®; LLC--Listerine®; LCP--Colgate Plax®. The degree of conversion analysis and the measure of the peak area at 2,930 cm-1 (organic matrix) of resin composite were done by Fourier-transform Raman spectroscopy (baseline, after 7 and 14 days). The data were subjected to multifactor analysis of variance (ANOVA) at a 95% confidence followed by Tukey's HSD post-hoc test. The DC ranged from 58.0% (Halogen) to 59.3% (LED) without significance. Differences in the peak area between LCUs were found after 7 days of storage in S and PT. A marked increase in the peak intensity of HLC and LLC groups was found. The soft-start light-activation may influence the chemical degradation of organic matrix in resin composite. Ethanol contained in Listerine® Cool Mint mouthwash had the most significant degradation effect. Raman spectroscopy is shown to be a useful tool to investigate resin composite degradation.

Effectiveness of light emitting diode and halogen light curing units for curing microhybrid and nanocomposites

Aim:To compare the polymerization efficacy of micro-hybrid and nanocomposites cured with Quartz-tungsten halogen (QTH) and light emitting diode (LED) light curing units (LCUs). The effectiveness of pulse cure mode in LED LCU was also investigated.Materials and Methods:Both micro-hybrid and nanocomposite specimens were cured using four different curing protocols giving a total of eight experimental groups. Ten cylindrical specimens were prepared for each group, and light cured for 40 s on the top surface, thus giving a total of eighty specimens. Vicker hardness measurements were carried out on the top and bottom surfaces after 24 h and hardness ratio was calculated.Results:For both micro-hybrid and nanocomposites, highest mean VHN was observed for the group cured with QTH LCU, and the lowest was observed for the group cured with second LED LCU in standard mode but the difference was significant only in case of nanocomposite.Conclusion:Curing nanocomposites with QTH LCU results in better micro hardness. Pulse cure mode does not effectively increase polymerization efficacy than the standard mode of curing.

Does an additional UV LED improve the degree of conversion and Knoop Hardness of light-shade composite resins?

The purpose of this study was to evaluate the degree of conversion (DC) using FT-Raman spectroscopy and the Knoop hardness (KHN) of composites cured by second and third-generation LED light curing-units (LCU), Radii Cal and Ultralume 5. Three composites (Filtek Supreme XT, Filtek Z350, and Esthet X) were selected for this study. KHN testing (n=10) was performed with 10 indentations for the top (T) and bottom (B) surfaces. For DC (n=10), both the T and B surfaces were analyzed. For KHN, the three composites differed in hardens. There was a "LCU-surface" interaction, in which Radii Cal showed significantly greater hardens in the B surface. For DC, there was a "composite-surface-LCU" interaction. For the "composite" factor, there was no significant difference between the groups, except for Supreme XT-Radii Cal (T or B surfaces). For the "LCU" factor there was a significant difference for Supreme XT T surface, Ultralume 5 obtained a higher DC. For the Z350 T surface, a significant difference in the DC in which Radii Cal obtained better results. For the "surface" factor, all groups presented T surfaces with a higher DC than the B surfaces, the sole exceptions involved Esthet X-Radii Cal and Z350-Ultralume 5. Knowledge regarding composite composition and the characteristics of LCUs are important for effective polymerization.

Degree of conversion and microhardness of TPO-containing resin-based composites cured by polywave and monowave LED units

ObjectivesTo determine the degree of conversion (DC) and Knoop microhardness (KHN) of resin-based composites (RBCs) containing trimethylbenzoyl-diphenylphosphine oxide (TPO) cured by polywave or monowave LED light-curing units (LCUs). MethodsThree groups (each n=5) of Tetric EvoCeram (Ivoclar Vivadent), Vit-l-escence (Ultradent) and Herculite XRV Ultra (Kerr) were prepared in Teflon moulds (5mm in diameter and 2mm thick) and cured with polywave Bluephase® G2 (Ivoclar Vivadent), polywave Valo (Ultradent) or monowave Bluephase® (Ivoclar Vivadent; control) resulting in 9 groups. DC and KHN were determined using micro-Raman spectroscopy and Knoop microhardness, respectively. High-performance liquid chromatography and nuclear magnetic resonance spectroscopy were used to confirm the presence or absence of TPO in the three uncured materials. Data were statistically analysed using two-way and one-way ANOVA and DC and KHN were correlated using Pearson's correlation (α=0.05). ResultsTPO was confirmed in Tetric EvoCeram and Vit-l-escence but not in Herculite XRV Ultra. All three LCUs produced comparable KHN for Tetric EvoCeram and Herculite XRV Ultra (p>0.05). Both polywave LCUs resulted in significantly higher KHN for Vit-l-escence and higher DC in Tetric EvoCeram and Vit-l-escence than the monowave Bluephase® (p<0.05). Conversely, Bluephase® showed higher DC than the two polywave LCUs in Herculite XRV Ultra (p<0.05). Pearson's correlation coefficient was r=0.818. ConclusionsPolywave LED LCUs improved monomer to polymer conversion and KHN in the two TPO-containing RBCs, but not in Herculite XRV Ultra. DC and KHN were linearly correlated in all three RBCs. Vit-l-escence showed the highest DC and KHN of the three materials tested. Clinical significanceThe use of polywave LEDs significantly improves both the DC and KHN of materials which contain TPO. This should be taken into account when curing bleached shades of RBCs even if the manufacturers do not indicate the presence of TPO in their materials.

Scanning Electron Microscopy and Roughness Study of Dental Composite Degradation

Our aim was to test the hypothesis that the use of mouthwashes, consumption of soft drinks, as well as the type of light curing unit (LCU), would change the surface roughness (Ra) and morphology of a nanofilled composite resin (Z350® 3M ESPE). Samples (80) were divided into eight groups: Halogen LCU, group 1, saliva (control); group 2, Pepsi Twist®; group 3, Listerine®; group 4, Colgate Plax®; LED LCU, group 5, saliva; group 6, Pepsi Twist®; group 7, Listerine®; group 8, Colgate Plax®. Ra values were measured at baseline, and after 7 and 14 days. One specimen of each group was prepared for scanning electron microscopy analysis after 14 days. The data were subjected to multifactor analysis of variance at a 95% confidence followed by Tukey's honestly significant difference post-hoc test. All the treatments resulted in morphological changes in composite resin surface, and the most significant change was in Pepsi Twist® groups. The samples of G6 had the greatest increase in Ra. The immersion of nanofilled resin in mouthwashes with alcohol and soft drink increases the surface roughness. Polymerization by halogen LCU (reduced light intensity) associated with alcohol contained mouthwash resulted in significant roughness on the composite.

Effects of different luting cements and light curing units on the sealing ability and bond strength of fiber posts

This study evaluated the sealing ability and push-out bond strength of two luting cements cured with two different types of light curing units (LCU): light-emitting diode (LED) versus quartz tungsten halogen (QTH). Forty teeth were divided into four groups(n=10/group). Quartz fiber posts (D. T. Light-Post) were luted to coronal or apical section of root canals using two types of resin cements (Panavia F or RelyX) cured with either LED LCU (Elipar FreeLight II) or QTH LCU (Optilux 501). Highest push-out bond strength was exhibited by QTH-cured RelyX, which was not significantly different from LED-cured RelyX but was higher than QTH-cured Panavia F. The push-out bond strength of Panavia F did not differ with LCU type (p>0.05), but exhibited lower values than both QTH- and LED-cured RelyX. Fluid filtration test revealed that sealing ability was not influenced by luting cement type, but was significantly influenced by LCU type in favor of QTH light source: QTH-cured specimens displayed better seal than LED-cured ones (p<0.05).

Comparison of light transmittance in different thicknesses of zirconia under various light curing units

PURPOSEThe objective of this study was to compare the light transmittance of zirconia in different thicknesses using various light curing units.MATERIALS AND METHODSA total of 21 disc-shaped zirconia specimens (5 mm in diameter) in different thicknesses (0.3, 0.5 and 0.8 mm) were prepared. The light transmittance of the specimens under three different light-curing units (quartz tungsten halogen, light-emitting diodes and plasma arc) was compared by using a hand-held radiometer. Statistical significance was determined using two-way ANOVA (α=.05).RESULTSANOVA revealed that thickness of zirconia and light curing unit had significant effects on light transmittance (P<.001).CONCLUSIONGreater thickness of zirconia results in lower light transmittance. Light-emitting diodes light-curing units might be considered as effective as Plasma arc light-curing units or more effective than Quartz-tungsten-halogen light-curing units for polymerization of the resin-based materials.

Micro-Raman spectroscopic analysis of the degree of conversion of composite resins containing different initiators cured by polywave or monowave LED units

Objectives To determine the degree of conversion (DC) over 48 h post-curing of resin mixtures containing trimethylbenzoyl-diphenylphosphine oxide (TPO) initiator cured by a polywave or a monowave LED light-curing unit (LCU). Methods In resin mixtures based on equal weight percent (wt%) of BisGMA and TEGDMA the following initiators were added: 0.2 wt% camphorquinone (CQ) + 0.8 wt% ethyl-4-dimethylaminobenzoate (EDMAB) (Group 1); 1 wt% TPO (Group 2) and 0.1 wt% CQ + 0.4 wt% EDMAB + 0.5 wt% TPO (Group 3). Half of the samples in each group ( n = 5) were cured using a polywave (bluephase ® G2, Ivoclar Vivadent) or a monowave LED LCU (bluephase ®, Ivoclar Vivadent). The DC was measured using micro-Raman spectroscopy within 5 min and then 1, 3, 6, 24 and 48 h post-irradiation. The data were analysed using general linear model and two-way ANOVA for the factors ‘time’, ‘material’, ‘surface’ and ‘LCU’ at α = 0.05. Results The initial DC values obtained upon light curing remained similar over a 48 h period. bluephase ® G2 produced the highest DC in Group 2 followed by Group 3, and Group 1. bluephase ® resulted in the highest DC in Group 1, followed by Group 2 and Group 3 ( p < 0.05). Conclusions Unfilled resin materials containing both TPO– and CQ–amine initiators are effectively cured using bluephase ® G2. Resin mixture with the same wt% of initiators is better cured when TPO is the only initiator, compared to CQ–amine only or combined TPO and CQ–amine system. After initial light cure, no additional conversion of uncured monomers was detected in an unfilled resin material over 48 h at 37 °C.