Effect of dentin pretreatment and curing mode on the microtensile bond strength of self-adhesive resin cements

PURPOSEThe aim was to evaluate the effect of curing mode and different dentin surface pretreatment on microtensile bond strength (µTBS) of self-adhesive resin cements.RESULTSFor G-CEM LinkAce cement groups, polyacrylic acid pretreatment showed the highest µTBS in the self-cured group. In the light-cured group, no significant improvements were observed according to the dentin surface pretreatment. There were no significant differences between curing modes. Both dentin surface pretreatment methods helped to increase the µTBS of RelyX U200 resin cement significantly and degree of pretreatment effect was similar. No significant differences were found regarding curing modes except control groups. In the comparisons of two self-adhesive resin cements, all groups within the same pretreatment and curing mode were significantly different excluding self-cured control groups.CONCLUSIONSelecting RelyX U200 used in this study and application of dentin surface pretreatment with EDTA and polyacrylic acid might be recommended to enhance the bond strength of cement to dentin.     

Influence of the curing mode on the degree of conversion of a dual-cured self-adhesive resin luting cement beneath ceramic

Abstract

Objective. To evaluate the effect of the delayed photoactivation and ceramic barrier on the degree of conversion (DC) of self-adhesive resin cement. Materials and methods. Circular specimens (5 mm in diameter × 1 mm in thickness) of the RelyX U-100 resin cement were made using the following curing protocols (n = 10): (G1) 40 s beneath a IPS Empress II ceramic; (G2) 40 s of direct photocuring; (G3) 80 s beneath the ceramic; (G4) 80 s of direct photocuring; (G5) self-curing; (G6) 5 min in the absence of light (self-curing) followed by transceramic photocuring for 40 s; (G7) 5 min in the absence of light (self-curing) followed by transceramic photocuring for 80 s. All the specimens were photoactivated by LED (800 mW/cm²). After 24 h of dry storage, the DC was measured by FTIR, on the top surface of the specimens. Data were submitted to one-way ANOVA and Tukey test (p ≤ 0.05). Results. Direct photocuring with no ceramic interposition, regardless of the curing time (40 s and 80 s) promoted the highest conversion mean (56.79 ± 1.19 and 59.98 ± 2.93, respectively) and the 5 min delay time for the transceramic photocuring presented a similar mean compared to the immediate transceramic photocuring. The DC was influenced by the ceramic barrier, decreasing the conversion values (49.72 ± 1.91 for 40 s and 52.36 ± 2.50 for 80 s), with no statistical difference from the groups with the previous 5 min of photoactivation delay. The self-cure only showed the worst DC values. Conclusion. Direct photocuring provided a higher degree of conversion for the self-adhesive resin cement. The delayed light activation did not influence the degree of conversion for the resin cement tested.     

Influence of ceramic thickness and curing mode on the polymerization shrinkage kinetics of dual-cured resin cements.

OBJECTIVES: The purpose of this study was to assess how ceramic disc thickness and curing mode (light or chemical) affects the polymerization shrinkage of dual-cured resin cements and to evaluate the effect of the ceramic discs on the curing speed of the cements during light exposure. METHODS: Six commercial resin cements, RelyX ARC, Bistite II, Duolink, Panavia F, Variolink II and Choice were used. Filler weight contents were determined by the ash method. Four ceramic discs with thicknesses of 0.5, 1, 2 and 4mm, respectively, were made. The attenuation of light intensity due to the ceramic discs was measured using a radiometer. The polymerization shrinkage kinetics of the resin cements by chemical or light cure through the different ceramic discs was measured using a bonded-disc method. RESULTS: There were differences in filler content among brands of resin cement. The polymerization shrinkage without ceramic disc was 2.61-4.59% by chemical cure and 2.93-4.66% by light cure. The polymerization shrinkage of RelyX ARC and Panavia F by chemical cure was statistically lower than by light cure (p<0.05). Polymerization shrinkage and filler weight were inversely related (R=-0.965). Both the transmitted light intensity and polymerization shrinkage decreased with increasing thickness of ceramic discs (p<0.05). The time to reach the maximum shrinkage rate of the resin cements increased with increasing ceramic thickness. The cure speed by light cure was 15-322 times faster than by chemical cure. SIGNIFICANCE: The polymerization shrinkage kinetics of dual-cured resin cements significantly differed between brands under various curing conditions. Clinicians should be aware of the setting characteristics of the cements, so they can choose the optimal materials for different clinical situations.     

Effect of curing mode on the polymerization characteristics of dual-cured resin cement systems

OBJECTIVES: To evaluate the effects of different curing conditions on the degree of conversion (DC) of dual-cured cementing systems [combination of bonding agent (BA) and resin cement (RC)] using infrared spectroscopy. METHODS: Four fourth generation products [Scotchbond Multipurpose Plus/RelyX (3M ESPE), Optibond/Nexus 2 (Kerr), All Bond2/Duolink (Bisco), and Bond-It!/Lute-It! (Pentron)], and three fifth generation materials [Bond1/Lute-It! (Pentron), Prime&Bond NT Dual-Cure/Calibra (Dentsply), and Optibond Solo Dual Cure/Nexus 2 (Kerr)] were applied to the surface of a horizontal attenuated-total-reflectance unit, and were polymerized using one of four conditions: self-cure (SC), direct light exposure through glass slide (DLE, XL3000/3M ESPE) or through pre-cured resin discs (shades A2;A4/2mm thick/Z250/3M ESPE). Infrared spectra of the uncured cementing systems were recorded immediately after application to the ATR, after the system was light-cured or left to self-cure, and spectra were obtained 5 and 10 min later. DC was calculated using standard techniques of observing changes in aliphatic-to-aromatic peak ratios pre- and post-curing. Data (n=5) were analyzed by two-way repeated measures ANOVA and Tukey's test (p=0.05). RESULTS: Changes in aliphatic-to-aromatic peak ratios before and after placing RC onto the BA demonstrated that a combined layer was created. All groups exhibited higher DC after 10 min than after 5 min, except the DLE group of Bond-it!/Lute-it!. No significant differences in DC were observed among light-activated groups regardless of the resin disc shade in three of the four fourth generation cementing systems. The SC groups exhibited lower DC than the DLE groups for both fourth and fifth generation products either after 5 or 10 min. CONCLUSION: The chemistry of the bonding interface changed when RCs were applied to uncured BAs. The presence of an indirect restoration can decrease the DC of some cementing systems and the self-curing mode leads to lower DC than the light-activating one.     

In-depth polymerization of a self-adhesive dual-cured resin cement

The aim of this study was to assess Knoop hardness at different depths of a dual-cured self-adhesive resin cement through different thicknesses of Empress Esthetic? ceramic.Flattened bovine dentin was embedded in resin. The cement was inserted into a rubber mold (0.8 x 5 mm) that was placed between two polyvinyl chloride plastic films and placed over the flat dentin and light cured by Elipar Trilight-QTH (800 mW/cm2) or Ultra-Lumelight-emitting diode (LED 5; 1585 mW/cm2) over ceramic disks 1.4 or 2 mm thick. The specimens(n=6) were stored for 24 hours before Knoop hardness (KHN) was measured. The data were submitted to analysis of variance in a factorial split-plot design and Tukey's test (a=0.05).There was significant interaction among the study factors. In the groups cured by the QTHunit, an increase in ceramic thickness resulted in reduced cement hardness values at all depths, with the highest values always being found in the center (1.4 mm, 58.1; 2 mm, 50.1)and the lowest values at the bottom (1.4 mm,23.8; 2 mm, 20.2). When using the LED unit, the hardness values diminished with increased ceramic thickness only on the top (1.4 mm,51.5; 2 mm, 42.3). In the group with the 1.4-mm-thick disk, the LED curing unit resulted in similar values on the top (51.5) and center(51.9) and lower values on the bottom (24.2).However, when the cement was light cured through the 2-mm disk, the highest hardness value was obtained in the center (51.8), followed by the top (42.3) and bottom (19.9),results similar to those obtained with the QTH curing unit (center > top > bottom). The hardness values of the studied cement at different depths were dependent on the ceramic thickness but not on the light curing units used.     

Influence of the curing mode on fluoride ion release of self-adhesive resin luting cements in water or during pH-cycling regimen

This study evaluated the effects of curing modes and storage conditions on fluoride release of resin cements. In phase 1, the cumulative fluoride release rate from samples of the resin cements (Panavia F 2.0, RelyX Unicem, MaxCem, and BisCem) was quantified after 15 days storage in water (n=4). In phase 2, the fluoride release profiles from the same materials were analyzed during pH cycling (n=4). In this second phase, fluoride was measured at specific times (one, two, three, five, eight, and 15 days). Disk-shaped specimens were prepared (10 mm × 0.5 mm), and the materials were either light activated or allowed to autopolymerize. For both phases, the fluoride release was measured using a fluoride ion-specific electrode. The fluoride release in water was not affected by the curing mode of RelyX Unicem and Maxcem resin cements. Panavia F. 2.0 and BisCem resin cements, either light cured or autopolymerized modes, released higher amounts of fluoride in water than the other self-adhesive cements. In phase 2, the concentration of fluoride released decreased from the first day of pH cycling until the 15th day for all resin cements, for both curing modes, regardless of the storage solution used (demineralizing/remineralizing). The fluoride release rate during pH cycling by Panavia F 2.0 and MaxCem was not affected by the curing mode. The effect of the curing mode on fluoride ion release in water or during pH cycling was product dependent.     

Light curing through glass ceramics: effect of curing mode on micromechanical properties of dual-curing resin cements

Objectives

The aim of this study was to investigate micromechanical properties of five dual-curing resin cements after different curing modes including light curing through glass ceramic materials.

Materials and methods

Vickers hardness (VH) and indentation modulus (Y _HU) of Panavia F2.0, RelyX Unicem 2 Automix, SpeedCEM, BisCem, and BeautiCem SA were measured after 1 week of storage (37 °C, 100 % humidity). The resin cements were tested following self-curing or light curing with the second-generation light-emitting diode (LED) curing unit Elipar FreeLight 2 in Standard Mode (1,545 mW/cm²) or with the third-generation LED curing unit VALO in High Power Mode (1,869 mW/cm²) or in XtraPower Mode (3,505 mW/cm²). Light curing was performed directly or through glass ceramic discs of 1.5 or 3 mm thickness of IPS Empress CAD or IPS e.max CAD. VH and Y _HU were analysed with Kruskal–Wallis tests followed by pairwise Wilcoxon rank sum tests (α?=?0.05).

Results

RelyX Unicem 2 Automix resulted in the highest VH and Y _HU followed by BeautiCem SA, BisCem, SpeedCEM, and finally Panavia F2.0. Self-curing of RelyX Unicem 2 Automix and SpeedCEM lowered VH and Y _HU compared to light curing whereas self-curing of Panavia F2.0, BisCem, and BeautiCem SA led to similar or significantly higher VH and Y _HU compared to light curing. Generally, direct light curing resulted in similar or lower VH and Y _HU compared to light curing through 1.5-mm-thick ceramic discs. Light curing through 3-mm-thick discs of IPS e.max CAD generally reduced VH and Y _HU for all resin cements except SpeedCEM, which was the least affected by light curing through ceramic discs.

Conclusions

The resin cements responded heterogeneously to changes in curing mode. The applied irradiances and light curing times adequately cured the resin cements even through 1.5-mm-thick ceramic discs.

Clinical relevance

When light curing resin cements through thick glass ceramic restorations, clinicians should consider to prolong the light curing times even with LED curing units providing high irradiances.     

Effect of curing mode on microtensile bond strength to dentin of two dual-cured adhesive systems in combination with resin luting cements for indirect restorations

This study evaluated the microtensile bond strength (microTBS) of dual-cured adhesive systems when the different components were either light activated or left in the uncured state prior to cementation of an indirect composite restoration. Occlusal dentin surfaces of 40 human third molars were flattened. The teeth were randomly assigned to 8 groups (n = 5) according to the dual-cured systems (bonding agents/resin cements) and curing modes: All Bond 2/Duolink (AB2-BISCO Inc) and Optibond Solo Plus Dual Cure/Nexus 2 (SOLO-Kerr). Resin cements were applied to pre-cured resin composite discs (2 mm thick/Z-250/3M ESPE), which were fixed to dentin surfaces containing adhesive resin in either cured (LP) or uncured states (SP). The restored teeth were light activated according to the manufacturers' instructions (LRC-XL3000/3M ESPE) or allowed to self-cure (SRC). The restored teeth were water-stored at 37 degrees C for 24 hours. They were then both mesial-distally and buccal-lingually sectioned to obtain bonded specimens (1.2 mm2). Each specimen was tested in tension at a crosshead speed of 0.6 mm/minute until failure. Data (MPa (SD)) were analyzed by two-way ANOVA and Tukey's post-hoc test (p < .05). AB2/SP exhibited higher microTBS than AB2/LP (p = .00001); however, no significant differences were noted between SOLO/LP and SOLO/SP. Results suggested that dual-cured adhesive systems were as strong or even stronger when they were left in the uncured state prior to indirect resin composite cementation.     

Effect of activation mode of dual-cured resin cements and low-viscosity composite liners on bond strength to dentin

OBJECTIVES: The aim of this study was to investigate the influence of the activation mode of dual-cured resin cements and application of low-viscosity composite liners over self-primed dentin on bond strength (BS) of dentin-bonding agents (DBA). METHODS: Three DBA (Single Bond; Prompt L-Pop and Clearfil SE Bond), their respective resin cements (RelyX ARC and Panavia F) and two low-viscosity composites (Filtek Flow and Protect Liner F) were tested. After removing the buccal enamel surfaces of 25 bovine incisors, each flat dentin surface was sectioned longitudinally and divided into two similar parts. The dentin surfaces were wet-abraded with 600-grit SiC paper and randomly divided into 10 groups. Experimental groups comprised the use of DBA and their respective dual-cured resin cements, with or without light-activation of resin cements. The low-viscosity resin was used only for the self-etching systems, Prompt L-Pop and Clearfil SE Bond. Three resin cement cylinders (0.5mm high and 0.75mm diameter) were built on each bonded dentin surface, using a tygon tubing mold. After water storage for 24h, specimens were subjected to micro-shear testing. Data were statistically analyzed by two-way ANOVA and Tukey test. RESULTS: Light-activation of resin cements resulted in significantly higher BS for all DBA versus groups in which the resin cements were allowed to self-cure. The low-viscosity composite application increased the BS only for Prompt L-Pop. CONCLUSIONS: The bond strength of resin cements to dentin is reduced if light-activation is not employed. The use of a low-viscosity composite liner resulted in improved bond strength only for the single-step self-etching adhesive.     

Effect of temperature on the degree of conversion and working time of dual-cured resin cements exposed to different curing conditions

OBJECTIVES: This study evaluated the degree of conversion (DC) and working time (WT) of two commercial, dual-cured resin cements polymerized at varying temperatures and under different curing-light accessible conditions, using Fourier transformed infrared analysis (FTIR). MATERIALS AND METHODS : Calibra (Cal; Dentsply Caulk) and Variolink II (Ivoclar Vivadent) were tested at 25°C or preheated to 37°C or 50°C and applied to a similar-temperature surface of a horizontal attenuated-total-reflectance unit (ATR) attached to an infrared spectrometer. The products were polymerized using one of four conditions: direct light exposure only (600 mW/cm(2)) through a glass slide or through a 1.5- or 3.0-mm-thick ceramic disc (A2 shade, IPS e.max, Ivoclar Vivadent) or allowed to self-cure in the absence of light curing. FTIR spectra were recorded for 20 min (1 spectrum/s, 16 scans/spectrum, resolution 4 cm(-1)) immediately after application to the ATR. DC was calculated using standard techniques of observing changes in aliphatic-to-aromatic peak ratios precuring and 20-min postcuring as well as during each 1-second interval. Time-based monomer conversion analysis was used to determine WT at each temperature. DC and WT data (n=6) were analyzed by two-way analysis of variance and Tukey post hoc test (p=0.05). RESULTS : Higher temperatures increased DC regardless of curing mode and product. For Calibra, only the 3-mm-thick ceramic group showed lower DC than the other groups at 25°C (p=0.01830), while no significant difference was observed among groups at 37°C and 50°C. For Variolink, the 3-mm-thick ceramic group showed lower DC than the 1-mm-thick group only at 25°C, while the self-cure group showed lower DC than the others at all temperatures (p=0.00001). WT decreased with increasing temperature: at 37°C near 70% reduction and at 50°C near 90% for both products, with WT reduction reaching clinically inappropriate times in some cases (p=0.00001). CONCLUSION : Elevated temperature during polymerization of dual-cured cements increased DC. WT was reduced with elevated temperature, but the extent of reduction might not be clinically acceptable.     

光照模式对双固化树脂粘接剂聚合程度的影响

目的研究不同光照模式对两种双固化树脂粘接剂聚合程度的影响。方法采用间歇光照、即刻光照、延迟光照和无光照4种不同固化方式,分别制备3MRelyXUnicem和DMGPermaCem2．0双固化树脂试件．24h避光保存后使用显微硬度仪测定样本表面硬度．三点弯曲试验测量挠曲强度．差示扫描量热仪进行玻璃化转变温度测量。数据采用协方差分析进行统计。结果两种树脂粘接剂各组表面硬度和挠曲强度由高到低依次为：间歇光照模式、即刻光照模式〉延迟光照模式〉无光照模式（P〈0．05）。差示扫描量热分析未检测到明显吸热峰,不能确定玻璃化转变温度。除无光照组外．3MRelvX Unicem表面硬度均显著高于DMG PermaCem2．0（P〈0．05）;DMG PermaCem2．0挠曲强度显著高于3MRelyX Unicem（P〈0．05）。结论间歇光照模式比延迟光照模式更有利于提高双固化树脂粘接剂聚合程度：双固化树脂粘接剂在无光照情况下聚合不全;与3MRelyX Unicem相比．DMGPernlaCem2．0抗压性能较差．但韧性较好．且无光照条件下聚合程度更高。     

Evaluation of physical properties and surface degradation of self-adhesive resin cements

This study sought to evaluate the pH value, film thickness, filler particle percentage, and morphological changes of self-adhesive resin luting cements. Products tested were G-Cem, Maxcem, Smart Cem, and RelyX Unicem. Cement pH was measured with pH test paper. Filler particle percentage was calculated after cement samples were incinerated at 750 degrees C. To test film thickness, mixed cements were placed between two glass plates and compressed using a loading device. For morphological changes, specimen surfaces were observed by SEM after treatment with various media. There were significant differences among the cement pH values measured at 20 seconds after light curing, and at 90 seconds and 48 hours after mixing. Filler particle percentage was directly proportional to film thickness. Degradation of cement surfaces was also detected after surface polishing and immersion in water, acetic acid, and acetone. In conclusion, significant differences were found in the surface properties of the materials tested, and these differences might lead to differences in their clinical performance.     

Effect of thermocycling on the bond strength between dual-cured resin cements and zirconium-oxide ceramics

The present study evaluated the durability of bond strength between zirconia and 3 different resin cements. Thirty stabilized tetragonal zirconium-dioxide blocks were duplicated in dual-curing resin core build-up material specimens. Resin blocks were randomly luted to zirconium surfaces using 1) Clearfil Esthetic Cement (CLF), 2) RelyX Unicem Aplicap (RELX), or 3) Multilink Automix (MLA). After 24 h, half of the specimens from each of the 3 groups were loaded in tension until fracture (0.5 mm/min). The remaining half were tested after 6,000 thermal cycles (5 to 55°C). Data were analyzed using 2-way ANOVA and the Tukey test (α = 0.05). Fractographic analysis was performed using a stereomicroscope. Tensile bond strength values were significantly affected by the luting agent system employed and by thermal aging (P < 0.001). The highest tensile bond strength values in non-thermal-aged groups were observed for specimens from the RELX and CLF groups. In contrast, in the thermal-aged groups, the highest tensile bond strength values were for the MLA and RELX groups. Moreover, while thermocycling significantly affected bond strengths in the RELX and CLF groups, the mean strength of the MLA group did not significantly change after aging. There was little difference in the distribution of failure modes in any group.     

光照射强度和水储存条件对双重固化树脂机械性能的影响

目的:探讨水储存条件对不同光强度照射条件下的双重固化树脂粘接剂机械性能的影响.方法:按照ISO 4049标准,将3种双重固化树脂粘接剂(Linkmax HV, Nexus 2和VariolinkII HV)制作成2 mm×2 mm×25 mm长方形试件,接受800, 310 和80 mW/cm2光强度照射后,干燥储存1 d或水储存90 d.储存后的试件接受三点弯曲试验测量其挠曲强度和弹性模量.使用SPSS 11.5统计软件对每种粘接剂的试验数据进行双因素方差分析.结果:光强度的减弱显著降低了3 种树脂粘接剂的挠曲强度和弹性模量;而90 d的水储存只显著降低了Linkmax HV和VariolinkII HV的弹性模量和挠曲强度,其中只有VariolinkII HV的弹性模量在光照射条件与水储存条件间出现在统计学上有显著性差异的交互作用,随着光强度的减弱其弹性模量呈现出加速降低的趋势.结论:双重固化树脂粘接剂仍然需要足够的光照射强度才能获得良好的机械性能和性能的稳定.     

Bond strength of dual-cured resin cements to human teeth

PURPOSE: This study evaluated the bond strength of four commercial resin luting cements to enamel and superficial dentin, using a second-generation laboratory composite. MATERIALS AND METHODS: Forty teeth were embedded in acrylic: 20 had superficial dentin exposed; 20 had enamel exposed. Each group was divided into four subgroups (n = 5) to be bonded with Variolink II, Dual Cement, 2-bond-2, and Permalute System, using an inverted, truncated cone of pre-cured Artglass that was placed over the resin cement with a load of 2 N for 2 seconds. Specimens were stored at 37 degrees C in 100% relative humidity for 24 hours before being tested for tensile bond strength (MPa). Data were analyzed using a two-way analysis of variance. Tukey-Kramer intervals for comparisons among resin cements and bonding substrates were calculated at a .05 significance level. RESULTS: Significant differences were found among resin cements. Variolink II had statistically higher bond strength values for both substrates than the rest of the cements evaluated. When bonding was to enamel, all failures were cohesive in the composite, and when bonding was to dentin, some adhesive failures occurred at the resin cement-dentin interface. Permalute System had higher bond strengths than 2-bond-2 and Dual Cement when bonded to enamel. CONCLUSIONS: Variolink II and Permalute had statistically different bond strengths to enamel and dentin. Variolink II showed statistically higher values for dentin bonding than the other cements. Use of Variolink II and Permalute resulted in statistically higher bond strengths than the other two cements.     

Hardening of dual-cured cements under composite resin inlays.

This study was conducted to determine the extent of hardening of three dual-cured cements under composite resin inlays and to determine the effectiveness of a light-reflecting wedge in promoting curing of the cements in the proximal margin. The exposure times needed to optimally harden the cements were determined by directly exposing the cements to the curing light. Composite resin inlays were bonded in an extracted molar with Dual cement, Dicor light-activated cement, and Duo cement. Cure-Thru reflective wedges were placed in the gingival embrasure of half of the specimens. None of the cements hardened completely by 24 hours when we used an exposure time that met or exceeded that recommended by the manufacturers. The chemical-cure component did not completely cure the cements when light was attenuated by the tooth and restoration. The light-transmitting wedge had little effect on hardening of the cements.