Effect of self-etching ceramic primer on the bond strength of feldspathic porcelain repair

The purpose of this study was to evaluate the effect of a self-etching primer on the bond strength of feldspathic porcelain with composite resin. Forty-eight feldspathic porcelain specimens (13 mm × 13 mm × 2 mm) were sectioned from CAD/CAM blocks. Specimens were randomly divided into 4 groups (n = 12) as regards to surface treatment method; HF acid etching (HFE), Monobond Etch and Prime (MEP), sandblasting (SB), and MEP + SB. After silane application for group HFE and SB, an adhesive bond was used as a bonding agent in all groups. Composite resin cylinders were build up onto the specimens. Specimens were stored in distilled water, thermocycled 5–55 °C for 5500 cycles, and subjected to shear bond strength (SBS) test in a universal testing machine. Data were statistically analyzed by Kruskal-Wallis and Mann Whitney U test (α=.05). Type of failures was evaluated under optical microscopy and surfaces were examined by SEM at ×500 and ×2500 magnifications. There was a significant difference among groups. (p = .019) HF group had the highest mean SBS value (17.54 ± 2.98 MPa) which was significantly higher than other groups (p<.05). Followed by the MEP + SB group (14.68 ± 3.41 MPa), SB group (13.98 ± 3.34 MPa) and MEP group (12.75 ± 2.33 MPa). Nevertheless, the HFE group significantly has higher SBS value than other groups all of the tested surface treatment methods have reached the convenient bond strength values for repair. Although MEP showed clinically acceptable SBS values, further researches with another type of porcelains should be tested.     

Effect of self-etching ceramic primer on bond strength of zirconia-reinforced lithium silicate ceramics

Abstract

This study evaluated the effect of self-etching ceramic primer (SECP) on shear bond strength (SBS) of zirconia-reinforced lithium silicate (ZLS) ceramics. Two hundred and seventy block-specimens of two types of ZLS ceramics and one type of lithium disilicate (LS) ceramics were prepared. Ninety blocks of each material were divided into three groups (n?=?30), namely group 1: no surface treatment (control), group 2: hydrofluoric acid (HF), silane-based primer (S), and group 3: SECP. Resin cement was applied, and light-cured for build-up. Shear bond strength (SBS) test was used. Half of the bonded specimens (n?=?15) were tested after storage in distilled water for 24?h, whereas the other half were tested after 5000 thermo-cycles. The failure modes were evaluated using scanning electron microscope (SEM). The SBS values for samples treated with SECP and HF?+?S within the respective materials were statistically comparable (p?>?0.05). Thermocycling significantly reduced the SBS (p?<?0.05) for all ceramic materials in groups 2 and 3. Mixed failure followed by adhesive failure were the most common failure modes in groups 2 and 3, whereas pretest failure was only detected in group 1. Considering the limitations of the study, with respect to in vitro bond strength, the SECP is an alternative for the conditioning of internal surface of glass ceramics.     

Biaxial flexural strength and Weilbull characteristics of adhesively luted hybrid and reinforced CAD/CAM materials to dentin: effect of self-etching ceramic primer versus hydrofluoric acid etching

Abstract

This study evaluated the influence of the surface treatment and aging on the biaxial flexural strength of ceramic materials cemented to a dentin analogue. One hundred twenty disc-shaped specimens were allocated into 12 groups considering three study factors: ceramic material (lithium disilicate, leucite-based ceramic and hybrid ceramic), surface treatment (10% hydrofluoric acid etching?+?silane or self-etching glass-ceramic primer) and Aging (with 10,000 thermocycles of 5–37–55?°C or without). A tri-layer assembly was designed to mimic a cemented restoration (Variolink N) into a dentin analogue. All samples were submitted to the biaxial flexural strength assay. The flexural strength in MPa was calculated using the finite element method for each sample considering thickness, material properties, and the load to fracture during the in vitro test. Fractographic analysis was also performed. The data was evaluated using three-way ANOVA and Tukey test (α?=?5%). ANOVA showed influence for the Material*Treatment*Aging interaction on the flexural strength (p?=?0.011). The highest strength was calculated for lithium disilicate ceramic?+?self-etching ceramic primer without aging (499?±?17?MPa)^A and the lowest value for hybrid ceramic material?+?acid etching with aging (424?±?48?MPa)^E. According to the Weibull modulus, the most predictable strength was calculated for lithium disilicate?+?acid etching after aging. Acid etching or self-etching ceramic primer promotes similar immediate biaxial flexural strength for each evaluated ceramic. In the long-term, superior strength was observed using acid etching for lithium disilicate and the self-etching ceramic primer for the hybrid ceramic while no difference was observed for leucite-based ceramic.

Clinical implications: Some protocols combining the CAD/CAM ceramic material and the surface treatment could present suitable and stable flexural strength.     

Effect of self etching ceramic primer and universal adhesive on bond strength of lithium disilicate ceramic

The clinical success of ceramic restorations is affected by the ceramic bonding procedure. The objective of the study was to evaluate the effect of different surface treatments, including the use of self-etching ceramic primer (SECP), on resin cement-glass ceramic bond strength. Thirty lithium disilicate ceramic (LDC) rectangles (3 mm × 3 mm × 8 mm) were fabricated Specimens were randomly assigned into three experimental groups (n = 10) according to the surface treatment: Group 1-hydrofluoric acid [HF acid]+ silane + universal adhesive; Group 2-HF + universal adhesive; Group 3-SECP + universal adhesive. All specimens were stored in distilled water for 24 h at 37 °C and shear bond strength (SBS) was tested at a crosshead speed of 0.5 mm (Universal Testing machine-Instron). Failure modes were evaluated using a digital microscope for all specimens. Analysis of variance and the Tukey post hoc tests using SPSS (Version 22.0, IBM, New York, USA) were used to analyze data. The SBS of groups 1 (19.74 ± 1.28 MPa) and 3 (21.11 ± 2.07 MPa) were significant higher than group 2 (14.80 ± 1.94 MPa). The SBS values for specimens in groups 1 (19.74 ± 1.28 MPa) and 3 (21.11 ± 2.07 MPa) were comparable. Adhesive, mixed and cohesive failure modes were observed and mixed failure was the most common in all groups. Therefore, the use of SECP and universal adhesive is recommended as an alternative to the use of HF acid in combination with ceramic primer while bonding to LDC.     

Effects of surface treatments on the bond strength of composite resin to hybrid computer-assisted design/manufacturing blocks

The aim of this study was to evaluate the repair bond strength of a dimethacrylate-based composite to two hybrid CAD/CAM blocks after different surface treatments. One hunded and twenty specimens were prepared from two different CAD/CAM blocks (Lava Ultimate (L), Cerasmart (C)). After thermal aging, specimens from each group (n?=?60) were divided into 6 treatment groups (n?=?10): (1) No treatment (2) Phophoric acid (37%) for 60?s, (3) Hydrofluoric acid (8%) for 60?s, (4) Sanblasting with 50-µm aluminium oxide (5) Er,Cr:YSGG laser treatment at 2?W and (6) Er,Cr:YSGG laser treatment at 3?W. Single Bond Universal was applied on all specimens and a dimethacrylate-based composite (Tetric N-Ceram) was bonded using Teflon tubes. After thermal cycling, shear bond strength (SBS) was tested, and failure modes were evaluated. Two-way ANOVA and independent t-test were used for statistical analysis (p?<?0.05). The highest SBS values were detected at Er,Cr:YSGG laser treatment groups (3W) (L:22.7?MPa, C:22.6?MPa). Lowest SBS values were obtained at no surface pretreatment groups followed by phophoric acid treatment groups which were significantly lower than sandblasting, hydrofluoric acid treatment and Er,Cr:YSGG laser treatment groups (p?=?0.001). The universal adhesive Single Bond Universal had no effect on promoting bond strength to hybrid ceramics alone or with phosphoric acid. Sandblasting, hydrofluoric acid and laser treatment were effective at increasing repair bond strength, for both Lava Ultimate and Cerasmart.     

The shear bond strength of repaired high-viscosity bulk-fill resin composites with different adhesive systems and resin composite types

This study compared the effect of different adhesive systems and composite resins on the shear bond strength (SBS) of repaired high-viscosity bulk-fill composites(Tetric EvoCeram Bulk Fill) and investigated failure modes. One hundred twenty cylindrical bulk-fill composite blocks (diameter 5?mm) were fabricated and thermocycled for 5000 cycles (5–55?°C). Specimens were roughened by diamond bur and divided into 8 groups (n?=?15). Bulk-fill blocks were repaired with the same material or nanohybrid composite resin(Tetric EvoCeram Nanohybrid) (diameter 3?mm) using different adhesive systems:Tetric N-Bond Universal (TSE);37% phosphoric acid etching?+?Tetric N-Bond Universal (TER); Clearfil SE Bond (CSE); 37% phosphoric acid etching?+?Adper^TMSingle Bond 2(SB). After repair procedures, all specimens were thermocycled again. The shear bond strengths were measured for all specimens using a universal test machine (crosshead speed of 1?mm/min). Cohesive strengths of bulk-fill composites were measured and described as control group. Debonded surfaces were observed with a stereomicroscope under 10x magnification to determine mode of failure. The SBS data of all groups was statistically analyzed by two-way ANOVA and Bonferroni correction test (p?<?0.05). The specimens repaired with bulk-fill composites showed significantly higher SBS values (25.86?±?5.74, 27.05?±?4.93, 24.49?±?6.95MPa) than those with nanohybrid composites (20.41?±?3.70, 22.08?±?6.37, 18.74?±?6.40?MPa) for TER,CSE,SB, respectively (p?<?0.05). There were no significant differences in SBS according to the type of adhesive systems for both repair materials (p?>?0.05). The predominant mode of failure was a mixed type in the restorative material except for the ones repaired with nanohybrid composites using Adper^TMSingle Bond 2. High-viscosity bulk-fill composites could be successfully repaired with the same materials. SBS of repaired bulk-fill composites reached cohesive strength for all tested groups.     

Effectiveness of different surface cleaning methods on the shear bond strength of resin cement to contaminated zirconia: an in vitro study

The purpose of this in vitro study was to evaluate and compare the effectiveness of different surface cleaning methods on the shear bond strength (SBS) of zirconia ceramic surfaces. Seventy polished and cleaned zirconia disk specimens of 8 mm in diameter and 3.4 mm in thickness were immersed in fresh saliva. They were then pressed into a freshly mixed silicone disclosing medium. Six different cleaning methods were applied to the tested groups; they were airborne-particle abraded (AA), covered with a cleaning paste (Ivoclean®) (IV), etched with orthophosphoric acid (PA), immersed in alcohol (AL), rinsed with tap water only (WA), or cleaned with steam (SC). No surface cleaning was done after saliva immersion and silicone disclosing medium contamination to the control group (CC). The specimens were then bonded to an adhesive resin cement using polyethylene tubes. SBS was determined using a universal testing machine at a crosshead speed of 1 mm/min. The specimens were also examined with a scanning electron microscope and a stereomicroscope. Group AA yielded the highest SBS value (7.01 ± 1.4 MPa) among the groups, while Group WA had the lowest SBS value (3.03 ± 0.8 MPa). The SBS values of Group AA (7.01 ± 1.4 MPa) and IV (6.2 ± 1.7 MPa) were also significantly higher than those of the remaining four groups (p < 0.05). Within the limitations of this in vitro study, it was concluded that among the various cleaning methods tested, airborne-particle abrasion and Ivoclean® paste were effective in cleaning the zirconia surface.     

Effect of different surface treatments on the repair bond strength of resin composites with titanium

The purpose of this study was to evaluate the effect of different surface treatment combinations on the bonding of composite resins to NiCr and titanium alloys after thermal cycling. Square-shaped specimens (10?mm x 10?mm x 2?mm) were made from NiCr and titanium alloys. The specimens were divided into 6 pretreatment groups (n?=?11): (1) machined titanium (control, no treatment); (2) CoJet sand application; (3) grinding with a diamond bur; (4) metal primer application; (5) CoJet sand?+?metal primer application; and (6) grinding with a diamond bur?+?metal primer application. The surface roughness of the mechanically treated specimens (control, grinding, CoJet sand) was evaluated. The surface morphology of both metals and elemental composition were examined with SEM and EDS. The composite resin was applied to the specimens. Shear bond strength (SBS) was tested after thermal cycling (5000 cycles, 5?°C to 55?°C). Failure modes were determined. The data were analyzed using the Shapiro-Wilk test, two-way ANOVA and post hoc Fisher’s LSD test (p?=?.05). For titanium specimens, the grinding?+?metal primer exhibited higher values than the other groups, and all groups showed higher SBS values than the control group. Combined use of CoJet sand, grinding with a diamond bur, and metal primer application would be useful for enhancing the bond strength of composite resin to titanium. The grinding of the NiCr surface with a diamond bur is the only method that could improve the bond strength of a composite resin compared to the other methods.     

The effect of different bonding protocols on the repair microshear bond strength of water-stored CAD/CAM resin composite

This study evaluated the repair microshear bond strength (μSBS) of water stored CAD/CAM resin composite under eight different surface treatments using a silane-containing universal adhesive in etch-and-rinse and self-etching modes. In total, 48 CAD/CAM resin composite slices were prepared from Lava Ultimate CAD/CAM blocks and stored in water for 6 months. The slices were assigned into 8 main groups, according to surface treatments (no treatment, no-treatment/silane, surface grinding, surface grinding/silane, sandblasting, sandblasting/silane, silica coating and silica coating/silane). Each main group was divided according to the universal adhesive application mode (either the etch-and-rinse mode or the self-etch mode). Each slice received 6 resin composite micro-cylinders (0.8 × 1 mm). Micro-shear bond strength was run at 0.5 mm/min crosshead speed until failure. Treated surfaces were examined using SEM. Bond strength data were statistically analyzed using Two-Way ANOVA/Tukey HSD post hoc test. Only ‘surface treatment’ significantly affected the repair μSBS (p ? 0.001). Parameters ‘Adhesive application mode’ and ‘surface treatment × adhesive mode’ showed no significant effect on μSBS (p = 0.458 and p = 0.286 respectively). Regardless of the adhesive application mode, silica coating showed the highest μSBS (21.6 ± 6.8 MPa), while sandblasting/silane showed the lowest μSBS (13.0 ± 6.1 MPa). Regardless of adhesive application mode, the use of silica coating to treat the water-stored CAD/CAM resin composite surfaces is crucial to improve the repair bond strength.     

Effects of chemical and physico-chemical surface conditioning methods on the adhesion of resin composite to different mineral trioxide aggregate based cements

This study investigated the adhesion of resin composite to mineral trioxide aggregate based cements after different chemical and physico-chemical surface conditioning methods. Mineral trioxide aggregate based cements (Biodentine, ProRoot MTA, Imicryl MTA) were embedded in Teflon disks (N?=?180). After storing at 37?°C at 100% humidity for 72?h, substrate surfaces were polished using silicon carbide papers. Specimens were allocated to 3 groups to be conditioned with one of the following (n?=?15 per group): a) Adhesive resin (Clearfil SE Bond, CSE), b) Adhesive resin (Adper Single Bond 2, SB2), c) air-abrasion with 30?μm alumina coated with silica?+?silane?+?adhesive resin (ALB), d) no surface conditioning, control group (CON). Microhybrid resin composite (Filtek Z250) was applied on the conditioned substrate surfaces and photo-polymerized. After storage at 37?°C at 100% humidity for 24?h, adhesive interfaces were loaded under shear (1?mm/min) in a universal testing machine. After debonding failure types were analyzed. Data were analyzed using 2-way ANOVA and Tukey’s test (alpha = 0.05). SBS results were significantly affected by surface conditioning (p?<?0.05) and materials (p?<?0.05). Interaction terms were significant (p?<?0.05). Biodentine-ALB resulted in significantly higher SBS values (3.96?±?1.24) compared to those of other combinations, while ALB and SB2 resulted in no significant difference for ProRoot MTA and Imicryl MTA (p?>?.05). CSE (1.36?±?0.5- 1.98?±?0.76) did not significantly increase SBS for all MTA materials compared to the control group (0.8?±?0.52 – 2?±?0.91) (p?>?9.05). While CON groups resulted in exclusively adhesive failures, ALB presented the highest incidence of mixed failures for all materials tested (60–100%).     

Effect of different ceramic primers on shear bond strength of resin-modified glass ionomer cement to zirconia

Purpose: This study evaluated and compared the effect of different ceramic primers on the shear bond strength of RMGIC to zirconia with and without air-particle abrasion. Material and Methods: 120 zirconia square specimens (5 mm × 5 mm × 2 mm) were fabricated. Half of the specimens were air-particle abraded (A) and the other half were left untreated (NA). Both groups were further divided into six subgroups (n = 10). Composite cylinders (2.9 mm × 3.0 mm) were fabricated and bonded to the zirconia samples with RMGIC (RelyX Plus) after different priming methods: no ceramic primer (group NS); Z-Prime (group ZP); Clearfil ceramic primer (group CP); cleaned with Ivoclean then Monobond plus (IV/MS); Monobond plus (group MS); and Rely X ceramic primer (group RX). Specimens were rinsed, stored in distilled water, and thermocycled (TC) for 10,000 cycles between 5 and 60 °C with a dwell time of 15s. Data were analyzed with two-way ANOVA and the Tukey–Kramer method test (a = .05). Results: air-particle abrasion significantly affected bond strength of RMGIC to zirconia regardless of the primer used (p < 0.001 for all primers and the control). After TC, A-ZP (11.1 ± 0.6 MPa), A-CP (11.9 ± 0.6 MPa), and A-MS (11.9 ± 0.5 MPa) revealed the highest shear bond strength values, while NA-NS (2.9 ± 0.3 MPa) and NA-RX (4.7 ± 0.5 MPa) had the lowest. Failure modes were primarily adhesive. Conclusion: air-particle abrasion with aluminum oxide and application of MDP-based ceramic primers provide the highest bond strength of RMGIC to zirconia.     

Shear Bond Strength Evaluation of Orthodontic Brackets Bonded to Fluorotic Teeth with a Self-Etching Primer and a New Generation of Color Bonding

The objective of this work was to evaluate the shear bond strength (SBS) and bond failure site of brackets bonded to teeth with fluorosis treated with and without microabrasion before placement of a self-etching primer (SEP) and a color-changing composite and to compare with a control group. This in vitro study included 120 premolars with and without dental fluorosis, divided into six groups: (1) healthy enamel etched for 15 sec and fifth generation primer, (2) healthy enamel, (3) mild fluorosis (MIF) enamel, (4) MIF enamel microabraded, (5) moderate fluorosis (MOF) enamel, and (6) MOF enamel microabraded. For groups 2–6, an SEP was used. All samples were evaluated with the SBS test and the modified adhesive remnant index (ARI). The highest SBS mean value was for healthy enamel etched for 15 sec and fifth generation primer and the lowest SBS mean value was for healthy enamel with SEP. Significant differences were found in the ARI between healthy and MOF groups. SBS of orthodontic brackets bonded on fluorotic teeth with an SEP and a new generation of color bonding could be clinically acceptable as the value obtained was above the suggested minimum required for orthodontic bonding.     

Post-treatment with high-power lasers to improve bond strength of adhesive systems to bleached dentin

To assess the effect of Er:YAG and diode lasers on the shear bond strength (SBS) of adhesive systems to bovine dentin submitted to bleaching with a high concentration agent. One hundred and twenty bovine dentin fragments were used. Fragments were distributed into 12 groups (n = 10) considering the bleaching (present or not), surface post-treatment (untreated, Er:YAG laser or diode laser) and adhesive system (total-etching or self-etching). Specimens received two applications of 38% hydrogen peroxide. Er:YAG laser (2940 nm, 200 mJ, 4 Hz) and diode laser (980 nm, 1.5 W) were applied for 15 s on bleached dentin surface. Restoration was performed with resin using split matrix. Specimens were submitted to SBS test and data (MPa) were analyzed by ANOVA and Tukey’s test (α = 0.05). SBS of bleached specimens decreased in comparison with non-bleached (p < 0.05). The highest values were obtained for the post-treatment with Er:YAG laser (p < 0.05). Total-etching adhesive was superior to self-etching system (p < 0.05). The irradiation of bleached dentin with Er:YAG laser followed by the application of the total-etching adhesive had similar SBS to unbleached dentin with no post-treatment (control) (p > 0.05). Er:YAG laser post-treatment followed by the total-etching adhesive system improve the bond strength of restorative material to bleached dentin.     

The effects of universal adhesive and innovative fabrication techniques of metal-ceramic restorations on repair strength of porcelain fracture with metal exposure

This study was to evaluate the effects of universal adhesive and innovative fabrication techniques of Cobalt-Chromium (Co-Cr) alloys on shear bond strength (SBS) between the repair material. One hundred forty-four Co-Cr alloys specimens were fabricated by casting (C), milling (M), direct process powder-bed method (CL), and direct metal laser sintering (DMLS) (EL). Each group was then divided randomly into three groups, according to the chemical agent used: alloy primer (Z), universal adhesive (A), or both (AZ). The composite resin cylinders were built on metal specimens. SBSs were determined after water storage and thermocycling, and data were statistically analyzed. The method used for the fabrication of Co-Cr alloy had a significant effect on bond strength (p?=?0.016). AZ (12.077?±?0.575?MPa) groups showed highest SBS values. Co-Cr alloys fabricated with DMLS method have a superior repair capacity. The universal adhesive increased the repair strength when applied with an alloy primer.     

Effect of surface conditioning methods on the microtensile bond strength of repair composite to indirect restorative materials

This study evaluated the effect of surface conditioning methods on the microtensile bond strength (µTBS) of a restorative composite to indirect restorative materials. Blocks (5?×?5 × 4?mm³) (N?=?72) of (a) Zirconia (In-Ceram Zirconia, Vita) (ZR), (b) lithium disilicate glass ceramic (IPS Empress II, Ivoclar Vivadent) (LD), (c) Indirect resin composite (Gradia, GC) (GR) were fabricated (n?=?24 per group) and divided randomly into three groups: 1-Control: no conditioning, 2-Silane coupling agent, 3-Hydrofluoric acid (9.5%) (HF)+silane. Each block was duplicated in resin composite. The adhesion surfaces were conditioned with airborne-particle abrasion (110?µm Al₂O₃ particles). Half of the conditioned blocks received no bonding and the other half one coat of bonding (ED Primer II, Kuraray). Each conditioned block was bonded to a composite block with a resin luting agent (Panavia F2.0, Kuraray). The blocks were sectioned into 1?mm² microsticks and tested for microtensile bond strength (µTBS) (0.5?mm/min) in a μTBS testing machine. Failure types were evaluated under stereomicroscope and Scanning Electron Microscope (SEM). Data were analyzed using three-way ANOVA, Bonferroni corrected and independent sample t-tests (p?<?0.05). Significant effect of the bonding (p?<?0.001) and surface conditioning (p?<?0.001) were observed in all groups. The highest mean bond strength values were obtained in the bonded, HF etched and silanized groups of ZR, LD and GR (12.4?±?2.9, 28.1?±?1.5 and 27.2?±?2?MPa, respectively). HF acid?+?silane increased the repair bond values in all materials. Majority of the failure types were adhesive for ZR group, whereas HF?+?silane conditioned LD and GR groups presented predominantly cohesive failures in the cement.     

Fatigue and fracture resistance of minimally invasive ceramic and resin composite veneers with different designs bonded adhesively to severely eroded teeth

This study evaluated the load bearing capacity of minimal invasive restoration alternatives on severely worn teeth after cyclic loading. Sound human maxillary incisors (N?=?72, n?=?9 per group) were randomly divided into nine experimental groups to receive one of the following restoration types: Group 1: Intact tooth, Group 2: Direct resin composite, Group 3: Lingual: Indirect resin composite, Labial: Ceramic veneer with lingual overlap, Group 4: Lingual: Indirect resin composite with lingual overlap, Labial: Ceramic, Group 5: Lingual: Direct composite, Labial: Ceramic, Group 6: Lingual: Feldspathic Ceramic, Labial: Feldspathic ceramic, Group 7: Lithium disilicate crown, Group 8: Metal-ceramic crown. Teeth were prepared simulating erosion/wear conditions. Specimens were subjected to cyclic loading (1,200,000 cycles, 5–55?°C) and then loaded to failure from the lingual surface at 105° inclination (1?mm/min). Data (Newton) were analyzed using one-way ANOVA, Tukey`s tests and Weibull moduli were calculated (α?=?0.05). Significant differences were observed between the groups for the initial (p?=?0.006) and maximum fracture load (p?=?0.002). Group 3 (55?±?36) presented significantly lower initial fracture load compared to other groups (79?±?35–134?±?36) (p?<?0.05). When maximum fracture load is considered, control group (1) (602?±?355) and from restored groups 2 (449?±?144) and 4 (495?±?291) showed significantly higher results (p?<?0.05). Weibull modulus for the maximum fracture load was the highest for Group 2 (m?=?3.47) among all groups (m?=?1.61–4.18). Groups 2, 3, 6 presented the highest incidence of repairable failures. Based on the results, severely worn teeth could be restored with lingual direct resin composite and labial veneering with indirect resin with overlap.     

The effect of curing lights and modes on dentin bond strength of bulk-fill composites applied in different thickness

To investigate shear bond strength (SBS) to dentin of a conventional and three bulk-fill composites applied in different increment thickness and cured by mono- and multi-wave LED LCUs. Two hundred and fifty-two extracted sound human molars were prepared for SBS test. The teeth were divided into four groups according to the resin composites used. Conventional composite: Tetric N-Ceram (control); high-viscosity bulk-fills: Tetric N-Ceram Bulk Fill, X-tra Fil, and SonicFill. Each group was subdivided (n?=?7) according to increment thickness (2, 4, and 6?mm) and cured by standard mode of a mono-wave LED or two different modes (standard and xtra power) of a multi-wave LED. The failure mode was stereomicroscopically determined at 40× magnification. Data were analyzed using Three-way ANOVA and further comparisons were assessed by Bonferroni’s multiple comparison test. There were no significant differences within X-tra fil and Tetric N-Ceram Bulk Fill groups for any of the variables (p?>?0.05). A significant decrease in SBS values with increase of layer thickness was observed for SonicFill and control groups. Also, curing mode had a significant effect on both composites at 6?mm thickness and standard mode of multi-wave LED caused the highest SBS value (p???0.05). Adhesive failure was the most common fracture pattern especially at 6?mm thickness applications. Based on the results of this study, the bulk-fill composites can be safely applied in one-step with 4?mm increments, although the examined composites performed better at 2?mm thickness. The performance of the composites at 6?mm increment may show differences related to the curing lights and modes.     

Prime-and-rinse approach for improving the enamel micro-tensile bond strengths of self-etch adhesives

The study investigated the effects of prime-and-rinse approach using 15% MDP (10-methacryloyloxydecyl dihydrogen phosphate)-containing primer on the enamel micro-tensile bond strengths (MTBS) of (ultra-) mild self-etch adhesives, enamel surfaces and enamel-resin interfaces. The buccal enamel surfaces of 69 human third molars were polished and randomly assigned to three groups: Group A (control, self-etch approach): Polished enamel surfaces were not further pre-treated. The enamel surfaces were acid-etched (Group B, (selective) enamel etching) or primed with 15% MDP-containing primer (Group C, prime-and-rinse approach) for 15?s and thoroughly water-sprayed. The enamel surfaces were applied with self-etch adhesives and placed with composite resins (Adper Easy One?+?Filtek Z350 (3?M ESPE); Clearfil S3 Bond?+?Clearfil Majesty (Kuraray-Noritake Co.); G Bond?+?Gradia Direct (GC); iBond?+?Charisma (Heraeus-Kulzer)), respectively. The specimens were prepared for MTBS test and scanning/transmission electron microscopy observations. Compared with group A, groups B and C produced significantly higher enamel MTBS (p?<?.01), regardless of the adhesives used. Groups B and C possessed similar enamel MTBS (p?>?.05). The SEM findings showed that smear layer remained on the polished enamel surface was completely removed by acid etching and almost completely removed by prime-and-rinse approach. The TEM microphotographs reveal that smear layer was detectable at the resin-enamel interface in group A, not in groups B and C. The novel prime-and-rinse approach using MDP-containing primer before the application of (ultra-) mild self-etch adhesives could greatly increase the enamel MTBS. That might be an alternative to selective enamel etching.     

Effect of Different Surface Treatment Methods on Micro-Shear Bond Strength of CAD-CAM Restorative Materials to Resin Cement.

This study aimed to investigate the micro-shear bond strength (μSBS) of surface treated CAD-CAM materials to resin cement. The specimens obtained from IPS e.max CAD, Lava Ultimate, Cerasmart and Vita Enamic were divided according to the surface treatment method applied as: no treatment, 3W and 2W Er, Cr:YSGG laser irradiation, sandblasting and 5% hydrofluoric acid (HF) application. Then, μSBS and field emission-scanning electron microscope analysis were performed. Data were analyzed using the Mann Whitney U and the Kruskal Wallis tests. For all materials, the highest μSBS values were demonstrated in HF acid applied groups. Regarding the μSBS values of IPS e.max CAD, no significant differences were found among control, 2W Er, Cr:YSGG laser and sandblasting groups (p?>?0.05). For Cerasmart and Lava Ultimate; 2W Er, Cr:YSGG laser treated group showed significantly lowest μSBS values while there was no significant difference among control, 3W Er, Cr:YSGG and sandblasting groups. HF applied Lava Ultimate and IPS e.max CAD groups exhibited the highest μSBS values among all the groups. For Vita Enamic; significantly lowest μSBS values were obtained in sandblasting group, whereas there was no significant difference among control, 3W Er, Cr:YSGG and 2W Er, Cr:YSGG groups (p?>?0.05). The FE-SEM images of all CAD-CAM materials submitted to surface treatment revealed an increase in surface alterations compared to control groups. It can be concluded that prior to bonding 5% HF acid treatment is the best surface treatment method regarding the bond strength for all CAD-CAM restorative materials. Er, Cr:YSGG laser application with energy level of 3W can be recommended for IPS e.max CAD.     

Evaluation of a new test method to determine the failure mode and macro-shear bond strength of dental materials to metals

Objective: To compare the macro mean shear bond strength (SBS) and failure mode of three cements to two types of metal using mould-enclosed and non-enclosed cement specimens. Methods: Titanium and base metal cobalt-based substrates were finished with 50 μm aluminium oxide. Two resin-modified glass-ionomers (Riva Luting Plus, Fuji Plus) and one resin cement (RelyX Unicem) were prepared as per manufacturers’ instructions. Metal mould-enclosed and non-enclosed cement specimens with a bonding area diameter of 3.5?mm were prepared and stressed to failure using a 2 mm blunt edge shear knife at a cross-head speed of 1?mm/min to determine mean SBS. The shear knife was placed against the surface of the substrate. Failure analysis of the failed interface was performed with a stereo microscope at 40× magnification. Results: Two-way Analysis of Variance demonstrated a significant difference in mean SBS between materials (p?=?0.004) and cement (p?=?0.001). There was also a significant interaction between method and cement on SBS, F(2,?170)?=?7.209, p?=?0.003. Post hoc Tukey tests demonstrated no significant difference for either resinmodified glass-ionomer cements (RMGIC) (p?=?0.864, p?=?0.620) when comparing non-enclosed and mould-enclosed test methods bonded to titanium. There was however a significant difference (p?<?0.001) between the mean SBS obtained for the resin cement when comparing the non-enclosed and mould-enclosed test methods. For base metal, the RMGIC’s SBS was higher than resin cement but no difference was observed between one of RMGIC’s and the resin cement non-enclosed mean SBS. Although not the case for RMGIC’s bonded to titanium or one RMGIC bonded to non-precious cobalt-based metal, when comparing the test method on each cement, RMGIC and the resin cement showed significant differences between non- and mould-enclosed specimens mean SBS. In the non-enclosed specimen tests, 71% of all specimens tested exhibited adhesive failure, which was statistically different (p?<?0.001) to 91% for the mould-enclosed specimens. Failure mode was not always statistically different within groups, however non-enclosed specimens showed higher frequencies of mixed failures. Conclusion: Within the limits of this study, significant differences were found in comparing the mean SBS between mould-enclosed and non-enclosed specimens. A significant difference was found in failure mode between mould-enclosed and non-mould enclosed specimens. Mould-enclosed specimens bonded to metal exhibited a higher frequency of adhesive failure than non-mould enclosed specimens. Relevance: Mould-enclosed specimens used in place of non-enclosed specimens can be used in SBS testing to give a more valid result when bonding to metal.