Light-cured Composites Research Articles

Shear bond strength of orthodontic resins after caries infiltrant preconditioning

To investigate the influence of caries infiltrant preconditioning on the shear bond strength of orthodontic resin cements on sound and demineralized enamel. Stainless-steel brackets were bonded to sound or artificially demineralized (14 d, acidic buffer, pH 5.0) bovine enamel specimens using a resin cement or a combination of caries infiltrant preconditioning (Icon, DMG) and the respective resin cement (light-curing composite: Heliosit Orthodontic, Transbond XT, using either Transbond XT Primer or Transbond Plus Self Etching Primer; light-curing resin-modified glass ionomer cement: Fuji Ortho; or self-curing composite: Concise Orthodontic Bonding System). Each group consisted of 15 specimens. Shear bond strength was evaluated after thermo-cycling (10,000×, 5°C to 55°C) at a crosshead speed of 1 mm/min, and data were statistically analyzed by analysis of variance, Mann-Whitney test, and Weibull statistics. Adhesive Remnant Index (ARI) scores and enamel fractures were determined at 25× magnification and were statistically analyzed by regression analyses (P < .05). The caries infiltrant system significantly increased the shear bond strength of Transbond XT Primer, Transbond Plus Self Etching Primer, and Fuji Ortho in sound specimens, and of all resin cements except for the Concise Orthodontic Bonding System in demineralized enamel. Overall, caries infiltrant preconditioning decreased significantly the number of enamel fractures, but it did not affect ARI scores. Preconditioning of sound and demineralized enamel with the caries infiltrant system did not impair but rather increased the shear bond strength of most orthodontic resin cements while decreasing the risk of enamel fracture at debonding.

Influence of curing time, overlay material and thickness on three light-curing composites used for luting indirect composite restorations.

To assess the microhardness of three resin composites employed in the adhesive luting of indirect composite restorations and examine the influence of the overlay material and thickness as well as the curing time on polymerization rate. Three commercially available resin composites were selected: Enamel Plus HRI (Micerium) (ENA), Saremco ELS (Saremco Dental) (SAR), Esthet-X HD (Dentsply/DeTrey) (EST-X). Post-polymerized cylinders of 6 different thicknesses were produced and used as overlays: 2 mm, 3 mm, 3.5 mm, 4 mm, 5 mm, and 6 mm. Two-mm-thick disks were produced and employed as underlays. A standardized amount of composite paste was placed between the underlay and the overlay surfaces which were maintained at a fixed distance of 0.5 mm. Light curing of the luting composite layer was performed through the overlays for 40, 80, or 120 s. For each specimen, the composite to be cured, the cured overlay, and the underlay were made out of the same batch of resin composite. All specimens were assigned to three experimental groups on the basis of the resin composite used, and to subgroups on the basis of the overlay thickness and the curing time, resulting in 54 experimental subgroups (n = 5). Forty-five additional specimens, 15 for each material under investigation, were produced and subjected to 40, 80, or 120 s of light curing using a microscope glass as an overlay; they were assigned to 9 control subgroups (n = 5). Three Vicker's hardness (VH) indentations were performed on each specimen. Means and standard deviations were calculated. Data were statistically analyzed using 3-way ANOVA. Within the same material, VH values lower than 55% of control were not considered acceptable. The used material, the overlay thickness, and the curing time significantly influenced VH values. In the ENA group, acceptable hardness values were achieved with 3.5-mm or thinner overlays after 120 or 80 s curing time (VH 41.75 and 39.32, respectively), and with 2-mm overlays after 40 s (VH 54.13). In the SAR group, acceptable hardness values were only achieved with 2-mm-thick overlays after 120 or 80 s curing time (VH 39.81 and 29.78, respectively). In the EST-X group, acceptable hardness values were only achieved with 3-mm or thinner overlays, after 120 or 80 s curing time (VH 36.20 and 36.03, respectively). Curing time, restoration thickness, and overlay material significantly influenced the microhardness of the tested resin composites employed as luting agents. The clinician should carefully keep these factors under control.

A comparative analysis of the accuracy of different direct impression techniques for multiple implants

The aim of this study was to compare the accuracy of different direct implant impression techniques for edentulous arches with multiple implants. Five experimental groups (n = 5) were assembled. Experimental models were created by a direct splinted technique (EG2 to EG5) and a non-splinted technique (EG1). In EG2 and EG3 synOcta impression copings were splinted with an acrylic resin bar, and in EG4 and EG5 with a light-curing composite resin bar. In EG3 and EG5 the resin bars were sectioned, while the other experimental groups were not. Three-dimensional discrepancies were measured by a computerized coordinate measuring machine. Distortion values among the groups were analysed using one-way repeated measures ANOVA. The post hoc Tukey's test was then performed for multiple comparisons. The highest accuracy was obtained in EG2 (mean deviation: 12.70 μm). The acrylic bars demonstrated less deviation (12.70 μm and 22.71 μm) from the master model than the light-curing composite resin groups and the non-splinted group (41.09 μm). The post hoc Tukey's test showed no significant difference among the groups when the effect of splint design on accuracy was investigated. For situations where impressions of multiple implants are to be made, splinting impression copings with acrylic resin demonstrate superior results than the non-splinted technique and splinting with light-curing composite.

Analysis of the Effect of Dental Chair Light on the Knoop Hardness of Composite Resin While Light Curing with QTH and LED Light Units

ABSTRACT Dental chair lights have been known to rapidly polymerize lightcured composites beyond the point of workability. Often in our dental clinics we are advised to switch off the dental chair light while light curing of dental composites. The purpose of this study was to determine whether the dental chair light causes any effect on the degree of polymerization of light cured composites using the quartz tungsten halogen (QTH) and the light emitting diode (LED) light curing units (LCUs). Filtek Z350 composite samples of 2 × 5 mm were prepared in an acrylic mold. Four groups were made having 20 samples each. In group I and II light curing was done using QTH LCU with and without the dental chair light respectively. Similarly in group III and IV LED LCU was used. Microhardness was measured and compared using Knoop's hardness Test. Data was submitted to ANOVA and Tukey's test. Results showed that the average microhardness was significantly higher in group 4 (LED light curing with dental chair light on). Thus, it was concluded that the dental chair light can be left on while using QTH and LED LCU's during light curing of composite material. How to cite this article Parekh B, Sathe S, Hegde V. Analysis of the Effect of Dental Chair Light on the Knoop Hardness of Composite Resin While Light Curing with QTH and LED Light Units. World J Dent 2012;3(2):156-160.

Quantitative Evaluation by Glucose Diffusion of Microleakage in Aged Calcium Silicate-Based Open-Sandwich Restorations

This study compared the in vitro marginal integrity of open-sandwich restorations based on aged calcium silicate cement versus resin-modified glass ionomer cement. Class II cavities were prepared on 30 extracted human third molars. These teeth were randomly assigned to two groups (n = 10) to compare a new hydraulic calcium silicate cement designed for restorative dentistry (Biodentine, Septodont, Saint Maur des Fossés, France) with a resin-modified glass ionomer cement (Ionolux, Voco, Cuxhaven, Germany) in open-sandwich restorations covered with a light-cured composite. Positive (n = 5) and negative (n = 5) controls were included. The teeth simultaneously underwent thermocycling and mechanocycling using a fatigue cycling machine (1,440 cycles, 5–55°C; 86,400 cycles, 50 N/cm2). The specimens were then stored in phosphate-buffered saline to simulate aging. After 1 year, the teeth were submitted to glucose diffusion, and the resulting data were analyzed with a nonparametric Mann-Whitney test. The Biodentine group and the Ionolux group presented glucose concentrations of 0.074 ± 0.035 g/L and 0.080 ± 0.032 g/L, respectively. No statistically significant differences were detected between the two groups. Therefore, the calcium silicate-based material performs as well as the resin-modified glass ionomer cement in open-sandwich restorations.

Effects of Light-Initiation Agent on Mechanical Properties of Light-Cured Nano-Hydroxyapatite Composite for Dental Restoration

In order to improve the experimental evidence of hotoinitiator, the effects of various dose of photoinitiator on mechanical properties of nanohydroxyapatite composite were investigated. According to the light initiating system, CQ and DMAEMA accounted for 0.8wt％, 1.0wt％, 1.2wt％ of total resin matrix, respectively. And then NHA processed by KH-570 was mixed with resin matrix in the ratio of 55:45. Then three groups （A, B, and C） of light-cured nanohydroxyapatite composites were prepared. Karuisima composite resin was used as control group D. The cured depth, compressive strength, and flexural strength were determined in each group. The results showed that as the ratio of photoinitiator increased, the cured depth increased, while the mechanical function declined. In group B, there were no significant differences in compressive strength, and flexural strength as compared with control group,P&gt;0.05. It is suggested that the quantity of CQ and DMAEMA in resin matrix were 1.0wt% respectively, the new light-cured nanohydroxyapatite composite has good qualities in both cured depth and mechanical property.

Evaluation of resin composite polymerization by three dimensional micro-CT imaging and nanoindentation

Objectives Light-cured composites undergo shrinkage during polymerization. The aim of this study was to evaluate regional shrinkage within a light-cured composite during polymerization by microcomputed tomography and mechanical properties by nanoindentation in bonded or non-bonded class-I cavity. Methods Zirconium oxide spherical fillers (30 μm diameter) were added as markers to a composite resin, filled into a box-shaped class I cavity with or without a bonding agent. The marker fillers were traced in 3D scans obtained by micro-CT before and after polymerization using a software (TRI/3D-BON). The average hardness of the resin composites determined by nanoindentation at each 250 μm depth was plotted against depth. Results In the bonded cavity, the filler particles at the top region moved toward the bottom of cavity, but at deeper depths, the direction of vertical movement changed toward the top of cavity (irradiated surface). A significant linear regression was found between filler displacement and composite depth ( R 2 = 0.9761). In the unbounded cavity, all the fillers moved toward the light curing source, and a significant power-law regression was found between filler displacement and composite depth ( R 2 = 0.849). In both groups, the data scattering increased at regions deeper than 3.5 mm, where the hardness, representing degree of conversion of composite, significantly decreased compared to the surface region. Significance The magnitude and direction of regional polymerization shrinkage depends on boundary conditions, depth and conversion degree. Polymerization shrinkage effect is most significant at the deepest part of the cavity. The application of micro-CT combined with sophisticated image analysis is a novel approach to investigate shrinkage mechanisms of dental composites.

Evaluation of different light-curing lamps

The aim of this study has been to evaluate light-curing composites polymerization quality carried out by halogen and new-diode lamps through the thermal analysis (TG–DTA). Samples have been polymerized at 3–20–40–60 s by halogen lamp and 1–3–6–9 s by new-diode lamp. The TG/DTA analysis shows that different light-curing times affect the degree of conversion of the composite, since by increasing the curing time the quantity of the monomer that has not reacted (residual) decreases. The new-diode lamp, according to the manufacturer, can cure composite restorations in few seconds; but at the conditions used in this study, the samples cured by the halogen lamp at the standard times of exposure, compared to the samples cured in few seconds by the new-diode lamp, show a lower mass loss.

Clinical evaluation on porcelain laminate veneers bonded with light-cured composite: results up to 7 years

The purpose of this study was to evaluate the clinical performance of laminate porcelain veneers bonded with a light-cured composite. Thirty patients were restored with 119 porcelain laminate veneers. The veneers were studied for an observation time of 7 years. Marginal adaptation, marginal discoloration, secondary caries, color match, and anatomic form were clinically examined following modified United States Public Health Service (USPHS) criteria. Each restoration was also examined for cracks, fractures, and debonding. Pulp vitality was verified. In addition, plaque and gingival indexes and increase in gingival recession were recorded. Survival rate evaluating absolute failures and success rate describing relative failures were statistically determined, using both restoration and patient-related analyses. On the basis of the criteria used, most of the veneers rated Alfa. After 7 years, the results of the clinical investigation regarding marginal adaptation and marginal discoloration revealed only 2.5% and 4.2% Bravo ratings, respectively, among the 119 initially placed veneers. Using the restoration as the statistical unit, the survival rate was 97.5%, with a high estimated success probability of 0.843 after 7 years. Using the patient as the statistical unit, the survival rate was 90.0% and the estimated success probability after 7 years was 0.824. Gingival response to the veneers was all in the satisfactory range. Porcelain laminate veneers offer a predictable and successful treatment modality giving a maximum preservation of sound tooth. The preparation, cementation, and finishing procedures adopted are considered key factors for the long-term success and aesthetical result of the veneer restorations.

Influence of surface roughness on streptococcal adhesion forces to composite resins

Objective To determine streptococcal adhesion forces with composite resins with different surface roughness. Methods Polishing and grinding were applied to obtain smooth (roughness 20 nm), moderately rough (150 nm) and rough (350 nm) surfaces of two orthodontic, light-cured composites. Adhesion forces between Streptococcus sanguinis and Streptococcus mutans and the composite surfaces were measured using atomic force microscopy in absence or presence of a salivary conditioning film. Initial adhesion forces were measured as well adhesion after 120 s of contact, as longer contact times are known to result in stronger adhesion forces (“bond-strengthening”). Surface roughness in absence and presence of salivary conditioning films were compared using ANOVA, while adhesion forces were subjected to a Weibull analysis. Results Initial adhesion forces in absence of a salivary conditioning film amounted between −0.7 and −0.9 nN for smooth composite resins and increased between −1.0 and −2.0 nN for the roughest surfaces. Streptococcal adhesion forces after bond-strengthening were significantly stronger than upon initial contact, irrespective of the composite type. Salivary conditioning films significantly decreased the surface roughness of the composites, as well as the streptococcal adhesion forces. Yet, also in the presence of a conditioning film, rougher composite surfaces exerted stronger adhesion forces, irrespective of composite type or bacterial strain. Conclusion Streptococcal adhesion forces to orthodontic composite resins increase with increasing roughness of the composite surfaces. Composite surface roughness less affects adhesion forces with S. mutans than with S. sanguinis.

Influence of silver nano-particles on monomer elution from light-cured composites

Objectives Silver containing materials have been used for years as antimicrobial materials. Silver particles were also added to experimental dental composites to reduce caries. The aim of our study was to show whether silver nanoparticles can lead to higher amounts of elutable substances. Methods 0.0125, 0.025, 0.05, 0.1 and 0.3% by weight silver nanoparticles were added to the commercial composite Tetric Flow ®. After light curing of the specimen, they were stored up to 7 days in methanol. The eluate was analyzed by gas chromatography/mass spectrometry. Results Compared to controls more camphorquinone (CQ), ethoxylated bisphenol-A-dimethacrylate (BisEMA) and triethylene glycol dimethacrylate (TEGDMA) will be eluted when silver nanoparticles were added to the composite. Twenty-four hours after the beginning of the experiment 132 μmol/l of CQ, 33.9 μmol/l BisEMA and 4.5 mmol/l TEGDMA were found in the eluate of the specimens containing 0.3% Ag. Significance Silver nanoparticles may influence the polymerization process in dental materials and lead to an increase in elutable substances. Four possible mechanisms of interaction are discussed: (1) reflection and scattering of the photons, (2) absorption of photons, (3) electron transfer from or to the silver nanoparticles and (4) formation of complexes with Ag +-ions.

Evaluation of composites light-curing at different times and distances of irradiation

The aim of this study is to evaluate light-curing composites polymerization quality (monomer/polymer) carried out at different times and distances of irradiation through the thermal analysis (TG-DTA). Samples have been polymerized at 20, 40 and 60 s (0-2-4-6-8 mm) through a constant polymerization and subsequently analysed by TG-DTA. The TG/DTA analysis shows that different light-curing times and different distance of irradiation affect the quality of polymerization; it is necessary to increase the curing time when the irradiation distance is longer than 2 mm.

Effect of short curing times with a high-intensity light-emitting diode or high-power halogen on shear bond strength of metal brackets before and after thermocycling

To test the hypothesis that short curing times using a high-intensity light-emitting diode (LED) or high-power halogen are not associated with compromised shear bond strength (SBS) of metal brackets before and after thermocycling. Two hundred forty extracted human premolar teeth were divided into six groups of 40 each. Metal brackets were bonded using a light-cured composite (Transbond XT). In group 1 a conventional halogen light (Hilux) was used for 40 seconds. In groups 2, 3, and 4 a high-power halogen light (Swiss Master) was used for 2, 3, and 6 seconds, respectively. In groups 5 and 6 a high-intensity LED (Bluephase) was used for 10 and 20 seconds, respectively. After bonding, half of the specimens in each group were thermocycled, and all specimens were tested for SBS. After debonding, the bracket bases and the enamel surfaces were scored according to the Adhesive Remnant Index. Two-way analysis of variance detected significant differences in SBS values with respect to curing method (type of light-curing unit and curing time) (P = .0001) and thermocycling (P = .01). Tukey post hoc analysis showed that with or without thermocycling the mean SBS values of groups 1, 4, 5, and 6 were not significantly different, whereas group 2 showed the lowest SBS values. The predominant failure site for groups 2 and 3 was between the bracket and the adhesive and for groups 4, 5, 6 it was at the tooth/adhesive interface. Curing time can be reduced to 6 seconds with high-power halogen light and to 10 seconds with high-intensity LED without compromising in vitro SBS of metal brackets.

Characterization of light-cured dimethacrylate resins modified with silsesquioxanes

Methacrylate-functionalized silsesquioxanes (SSQO) were synthesized by the hydrolytic condensation of 3-(methacryloxypropyl) trimethoxysilane (MPTMS) using dimethacrylate monomers as reactive solvent. Resins containing about 40 wt% SSQO displayed a modest increase in viscosity compared with the unmodified methacrylate monomer. This is attributed to a dilution of the reacting medium, which discourages bimolecular reactions that lead to the generation of high-molar mass oligomers and, consequently, prevents undesired increases of viscosity. Substitution of monomer with SSQO reduced the volumetric shrinkage during photopolymerization. The amount of leachable monomer detected in formulations containing SSQO was markedly reduced. This indicates that the unreacted monomer exists mainly as pendant chains instead of free leachable monomer. The presence of different proportions of SSQO in the methacrylate monomer resulted in no apparent change in the flexural modulus and in a modest decrease in the compressive yield stress of the polymerized materials. From results presented in this research, it emerges that methacrylate monomers modified with SSQO are attractive for applications that require reduced volumetric shrinkage and long storage periods, such as light-cured dental restorative composites.

Effect of shrinkage strain, modulus, and instrument compliance on polymerization shrinkage stress of light-cured composites during the initial curing stage

Objectives The aim of this study was to investigate the influence of shrinkage strain, modulus, and instrument compliance on the polymerization shrinkage stress measurement of light-cured composites, and to determine whether the silorane-based low-shrinkage composite shows a low-polymerization shrinkage stress. Methods A universal hybrid; Z250 (Z2), a flowable; Z350 (Z3), and a silorane-based; P90 (P9) composite was examined. A modified “bonded disc method” was used to measure the axial shrinkage strain of the composite. For the measurement of the initial modulus development of composites during light curing, a dynamic oscillatory shear test was undertaken using a custom-made oscillation rheometer. A frequency of 6 Hz and strain amplitude of 0.0091 rad for 20 s was employed and the complex shear modulus ( G *) was determined. A newly designed stress–strain analyzer was made to measure the shrinkage stress of the composites with two modes: (1) high compliance, or (2) low compliance. The shift between the two modes was controlled by an On–Off switch of a negative feedback circuit. Theoretical shrinkage stress was calculated from the shrinkage strain and modulus measured above, and compared with experimentally measured stress. Data were analyzed with one-way ANOVA and Tukey's post hoc test ( α = 0.05), and correlation analysis was done to investigate the relationship between measured stress and shrinkage strain, modulus, and theoretical stress. Results The shrinkage strain of Z3 (4.12%) at 10 min was the highest, followed by Z2 (2.31%) and P9 (0.77%). At 10 s after light curing, Z2 showed the highest modulus (466.2 MPa), Z3 (154.1 MPa), and P9 the lowest (130.7 MPa). The measured stresses with low compliance were much higher than those with high compliance. With high compliance, the contraction stress of Z3 was the highest (2.75 MPa), followed by Z2 (1.54 MPa) and P9 (0.48 MPa). In low-compliance mode, the stresses of Z3 (7.93 MPa) and Z2 (7.48 MPa) were similar ( p = 0.323) while the stress of P9 (3.23 MPa) was much lower. A strong correlation was observed between the theoretical stress and the measured stress with low compliance ( R = 0.996). In high-compliance mode, the shrinkage strain also showed a near-linear relationship with the stress measured ( R = 0.937), but the modulus showed a low correlation with the measured stress ( R = 0.398). Significance Depending on the instrument compliance, polymerization shrinkage stress showed significant differences for each material. In high-compliance shrinkage strain played a greater role, while in low-compliance shrinkage strain and elastic modulus contributed comparably in determining the shrinkage stress. The low-shrinkage silorane-based composite demonstrated considerable reduction in shrinkage strain and stress.

Thermal analysis of light-curing composites

The aim of this study has been to evaluate light-curing composites polymerization quality (monomer/polymer) with an halogen and diode lamp through the thermal analysis (TG-DTA). Samples have been polymerized at 20, 40 and 50 s through a constant and a soft start polymerization and, subsequently, analyzed by TG-DTA. The TG/DTA analysis shows that different light-curing times affect the degree of conversion of the composite, since by increasing the curing time the quantity of the monomer that has not reacted (residual) decreases. The halogen lamp, compared to the diode lamp, produces a lower mass loss at 20 s, while for 40 and 50 s the results are overlapping. The soft start polymerization (20 s) initially produces a higher mass loss, if compared to the constant intensity, but, by performing a polymerization for at least 40 s, the results can be overlapped.

Thermal evaluation of light-curing composites

Thermal evaluation of light-curing composites

Degree of vinyl conversion, polymerization shrinkage and stress development in experimental endodontic composite.

This study explores degree of vinyl conversion (DVC), polymerization shrinkage (PS) and shrinkage stress (PSS) of the experimental amorphous calcium phosphate (ACP) composites intended for use as an endodontic sealer. Light-cure (LC), chemical cure (CC) or dual-cure (DC; combined light and chemical cure) resins comprised urethane dimethacrylate (UDMA), 2-hydroxyethyl methacrylate (HEMA), methacryloyloxyethyl phthalate (MEP) and a high molecular mass oligomeric co-monomer, poly(ethyleneglycol)-extended UDMA (PEG-U) (designated UPHM resin). To fabricate composites, a mass fraction of 60 % UPHM resin was blended with a mass fraction of 40 % as-made (am-ACP) or ground ACP (g-ACP). DVC values of copolymer (unfilled UPHM resin) and composite specimens were determined by infrared spectroscopy. Glass-filled composites were used as controls. PS and PSS of composites were determined by dilatometry and tensometry, respectively. LC copolymers attained extraordinary high DVC values at 24 h post-cure (95.7 %), compared to CC (52 %) and DC (79.3 %) copolymer specimens. While the DVC values of LC and DC am-ACP composites were reduced between 5 and 10 %, DVC values of DC g-ACP composites increased almost 8 % compared to the corresponding copolymers. High DVC attained in LC composites was, expectedly, accompanied with high PS values (on average 7 vol%). However, PSS developed in LC and especially DC composites did not exceed PSS values seen in other UDMA-based composites. Based on this initial evaluation, it is concluded that, DC, g-ACP filled UPHM composite shows promise as an endodontic sealer. However, further physicochemical evaluations, including water sorption, mechanical stability and ion release as well as a leachability studies need to be performed before this experimental material is tested for cellular responses and, eventually recommended for clinical utility.

Glass transition and degree of conversion of a light-cured orthodontic composite

Objective:This study evaluated the glass transition temperature (Tg) and degree of conversion (DC) of a light-cured (Fill Magic) versus a chemically cured (Concise) orthodontic composite.Material and Methods:Anelastic relaxation spectroscopy was used for the first time to determine the Tg of a dental composite, while the DC was evaluated by infrared spectroscopy. The light-cured composite specimens were irradiated with a commercial LED light-curing unit using different exposure times (40, 90 and 120 s).Results:Fill Magic presented lower Tg than Concise (35-84°C versus 135°C), but reached a higher DC.Conclusions:The results of this study suggest that Fill Magic has lower Tg than Concise due to its higher organic phase content, and that when this light-cured composite is used to bond orthodontic brackets, a minimum energy density of 7.8 J/cm2 is necessary to reach adequate conversion level and obtain satisfactory adhesion.

Effect of Light Activation Mode on the Incompatibility Between One-bottle Adhesives and Light-cured Composites: An In Vitro Shear Bond Strength Study

This study examined the effect of different light activation modes for light-cured resin-based composites on the shear bond strength to dentin of two one-bottle adhesives with differing acidity. In this experimental study, a flat middle dentin surface was prepared on 110 extracted sound molars using a 600-grit polish paper. The teeth were then randomly divided into 10 equal groups (n = 11). One-Step Plus (OS) and Prime & Bond NT (P&B NT) were used according to the manufacturer's instruction with their respective composite (Aelite, Spectrum TPH) applied and cured using five different light-activation modes: 1. Conventional (CO): 600 mW/cm2 (40 seconds) 2. Soft-Start I (SSI): 100 mW/cm2 (10 seconds) 600 mW/cm2 (30 seconds) 3. Soft-Start II (SSII): 200 mW/cm2 (10 seconds), 600 mW/cm2 (30 seconds) 4. Pulse-Delay I (PDI): 100 mW/cm2 (3 seconds), 3-minute delay, 600 mW/cm2 (37 seconds) 5. Pulse-Delay II (PDII): 200 mW/cm2 (3 seconds), 3-minute delay, 600 mW/cm2 (37 seconds) After 24 hours storage in distilled water at room temperature, a shear bond strength (SBS) test was performed using an Instron machine at 1 mm/minute and the results were recorded in MPa. Statistical analysis included two-way ANOVA and Tukey HSD (p < 0.05). The highest SBS (MPa) was shown in the OS conventional group (19.62 +/- 2.21) and the lowest SBS was shown in P&B NT, PDII (5.93 +/- 1.79). In each group of five curing modes, the mean SBS for P&B NT was significantly lower than OS: conventional mode--P&B NT (17.27 +/- 1.98) vs OS (19.62 +/- 2.21); SSI-P&B NT (10.84 +/- 2.82) vs OS (13.09 +/- 1.24); SSII - P&B NT (14.78 +/- 1.63) vs OS (18.79 +/- 1.57); PDI-P&B NT (5.93 +/- 1.79) vs OS (11.97 +/- 2.59) and PDII-P&B NT (11.82 +/- 1.24) vs OS (16.00 +/- 1.62) (p < 0.001 for all comparisons). For each of the adhesives, the ranking of SBS was as follows: CO > SSII > PDII > SSI > PDI, with the two-paired comparisons of curing modes being significantly different (p < 0.05). The results of the current study indicated that the bond strength of P&B NT might be compromised by the higher acidity of this adhesive compared to OS during each curing mode, especially PDI. The conventional mode was least affected by the acidity of the adhesive.