Effect of silane pretreatment on the immediate bonding of universal adhesives to computer-aided design/computer-aided manufacturing lithium disilicate glass ceramics

Effect of universal adhesives and self-etch ceramic primers on bond strength to glass-ceramics: A systematic review and meta-analysis of in vitro studies

STATEMENT OF PROBLEM

To simplify dental procedures, multicomponent products such as universal adhesives and self-etch ceramic primers have been recommended for glass-ceramic bonding; however, studies have shown a wide range of results.

PURPOSE

The purpose of this systematic review and meta-analysis was to analyze the in vitro bond strength promoted by hydrofluoric acid+silane-containing universal adhesives and a self-etch ceramic primer to glass-ceramics and compare it with that of conventional treatments.

MATERIAL AND METHODS

A systematic search was conducted in the PubMed/Medline, Scopus, LILACS, and ISI Web of Science databases up to April 2021. In vitro studies assessing the resin-mediated bond to glass-ceramics by using a self-etch ceramic primer and hydrofluoric acid+silane-containing universal adhesives and/or compared with traditional hydrofluoric acid+glass-ceramic primers were included. Selection of studies, data extraction, and risk-of-bias analysis were performed. Statistical analysis was performed by using a review management software program using a random effects model (α=.05).

RESULTS

A total of 33 studies were included in the qualitative analysis and 26 studies in the quantitative analysis. Bond strength to lithium disilicate ceramic was higher when a hydrofluoric acid+glass-ceramic primer was used than when using a hydrofluoric acid+silane-containing universal adhesive (P<.05), except when 9% to 10% acid concentration was used in combination with static aging (P=.100). A self-etch ceramic primer promoted bond strength values to lithium disilicate that were similar to those of the hydrofluoric acid+glass-ceramic primer (P>.100).

CONCLUSIONS

Hydrofluoric acid+silane-containing universal adhesive was not as effective as the hydrofluoric acid+glass-ceramic primer in promoting bond strength to glass-ceramic. Bond strength values generated by a self-etch ceramic primer to glass-ceramic were similar to those generated by the conventional treatment.

Evaluation of repair bond strength of a dental CAD/CAM resin composite after surface treatment with two Er,Cr:YSGG laser protocols following artificial aging

The aim of the present study was to evaluate the impact of two Er,Cr:YSGG laser surface treatments on the repair bond strength of a dental CAD/CAM resin composite (Brilliant Crios) after artificial aging. Twenty-four resin-based CAD/CAM blocks were cut and 48 rectangular slabs (3 x 12 x 14 mm) were prepared. Preliminary SEM observations indicated the most favorable laser settings regarding surface modification of the tested restorative material. The CAD/CAM specimens were then divided into 4 groups (n=12) based on their surface pretreatment: no treatment, air abraded with 50-μm Al2O3 particles, and laser irradiated with two different protocols using Er,Cr:YSGG laser with average power 3.5 and 4.5 W, pulse repetition rate 35 and 50 Hz, and pulse energy 100 and 90 mJ, respectively. After surface treatments each group followed a bonding protocol with silane and a flowable resin composite was used to prepare 48 microrods. Half of the microrods of each group were subjected on shear bond strength (SBS) test (chisel-shaped blade, load cell of 500 N, crosshead speed of 1 mm/min) after 24 h, while the other half underwent artificial aging (15,000 cycles, 5-55 °C) and then SBS test. The debonded specimens were examined under an optical microscope to determine the failure mode. All specimens were also evaluated using SEM to assess the surface topography after the treatments. The results showed that SBS significantly decreased after thermocycling in all the experimental groups (p<0.05). Control group presented much lower SBS values than the other groups after both 24 h and thermocycling (p<0.05). The highest values of SBS exhibited air-abrasion group (p<0.05), followed by the two laser groups, which did not differ to each other (p>0.05). The results of the current study indicated that Er,Cr:YSGG laser irradiation can be an alternative treatment for repairing the tested resin-based CAD/CAM restorative material.

Bonding stability of universal adhesives to feldspathic ceramic with or without prior silane application

PURPOSE

This study aimed to assess the bonding stability of three universal adhesives to a CAD-CAM feldspathic ceramic with or without prior silane application.

MATERIALS AND METHODS

The universal adhesives tested were Ambar Universal (FGM), Single Bond Universal (3M), and Ybond Universal (Yller). Scotchbond Multipurpose Plus (3M) was used as a control. The silane used was RelyX Ceramic Primer (3M). Microtensile bond strength (μTBS) to Vitablocs Mark II was measured after 24 h or 6 months of water aging (n = 20). Failure modes were observed through scanning electron microscopy, and pH and degree of C=C conversion (DC) of the adhesives were measured (n = 3). Data were analyzed using one-, two-, and three-way ANOVA.

RESULTS

The pH values differed significantly among the adhesives (p < 0.001), while the DC was similar (p = 0.141). The universal adhesives showed significant differences in μTBS, with higher immediate results when using silane and lower results after aging. Notably, a significant decrease in μTBS was observed after 6 months when silane was applied. In contrast, the control adhesive exhibited consistent results between the 24-h and 6-month storage periods. The universal adhesives showed a decrease in μTBS ranging from 25.5% to 40.1% after prolonged storage. Adhesive failures were predominant in all groups. The presence or absence of silane in the adhesive composition did not affect the bonding performance.

CONCLUSIONS

The application of a separate silane coupling agent improved the immediate bond strength of universal adhesives to CAD-CAM feldspathic ceramic. However, this bond strength significantly decreased after 6 months of water aging. The bond strength remained stable for universal adhesives when applied without silane after 6 months of aging.

Effects of Different Primers on the Bond Strength to Properly and Excessively Etched Ceramic-coated Zirconia

PURPOSE

To determine the effects of various primers on the immediate and long-term bond strength of ceramic-coated ultratranslucent zirconia that is properly or excessively etched.

METHODS AND MATERIALS

Ceramic-coated zirconia plates were etched with 9.5% hydrofluoric acid (HF) for 2 or 5 minutes, after which the surface morphology and elemental composition were examined. The etched specimens were treated with different primers including methacryloyloxydecyl dihydrogen phosphate (MDP)-only containing primer, silane-only containing primer, MDP and silane-containing ceramic primer as well as MDP and silane-containing adhesive system. For surface contact angle and shear bond strength (SBS) data, the difference between groups was evaluated by one-way analysis of variance (ANOVA) and three-way ANOVA factorial analysis, respectively. The statistical significance level of 0.05 was set and the Tukey test and the Dunnett-T3 test were used for post-hoc multiple comparisons.

RESULTS

Excessive etching (9.5% HF for 5 minutes) led to overconsumption of the glass layer and exposure of zirconia substrate compared to proper etching (9.5% HF for 2 minutes). Among different primers, the surface contact angle of the silane-only containing primer group was the lowest. The silane-only containing primer and MDP and silane-containing ceramic primer produced higher shear bond strength of properly and excessively etched ceramic-coated zirconia, respectively, both before and after thermal aging.

CONCLUSIONS

The silane-only containing primer and MDP and silane-containing primer can obtain better immediate and long-term shear bond strength for properly and excessively etched ceramic-coated zirconia, respectively.

Influence of the Application Time of Silane for the Bonding Performance between Feldspar or Lithium Disilicate Ceramics and Luting Resin Composites

A correct silanization time is essential for successful surface functionalization and sufficient bonding to dental ceramics. The shear bond strength (SBS) of lithium disilicate (LDS) and feldspar (FSC) ceramics and luting resin composite was investigated with respect to different silanization times, taking into account the physical properties of the individual surfaces. The SBS test was performed with a universal testing machine, and the fracture surfaces were evaluated by stereomicroscopy. The surface roughness of the prepared specimens was analyzed after etching. Changes in surface properties due to surface functionalization were evaluated by surface free energy (SFE) via contact angle measurement. Fourier transform infrared spectroscopy (FTIR) was used to determine the chemical binding. The roughness and SBS of the control group (no silane, etched) were higher for FSC than for LDS. Regarding the SFE, the dispersive fraction increased and the polar fraction decreased after silanization. FTIR confirmed the presence of silane on the surfaces. The SBS of LDS showed a significant increase from 5 to 15 s, depending on the silane and luting resin composite. For FSC, cohesive failure was observed for all samples. For LDS specimens, a silane application time of 15 to 60 s is recommended. Based on clinical conditions, no difference between the silanization times was observed for FSC specimens, indicating that etching alone produces sufficient bonding.

Acrylamide monomers in universal adhesives

OBJECTIVES

The mono-functional monomer 2-hydroxyethyl methacrylate (HEMA) is often added to universal adhesives (UAs) to improve surface wetting and prevent phase separation. Nevertheless, HEMA promotes water sorption and hydrolysis at adhesive interfaces, hereby affecting long-term bonding to dentin. This study investigated if two acrylamide monomers could replace HEMA in an UA formulation applied in etch-and-rinse (2E&R) and self-etch (1SE) bonding mode.

METHODS

Four experimental UAs were bonded to bur-cut dentin. In addition to 12 wt% 10-MDP, 25 wt% Bis-GMA and 10 wt% TEGDMA as common monomer composition, 20 %wt ethanol and 15 %wt water as solvent, and 3 wt% polymerization-related additives, the four formulations solely differed for either the acrylamide cross-linker monomer 'FAM-201' as TEGDMA alternative and HEMA replacement, the hydroxyethyl acrylamide monomer 'HEAA' as HEMA alternative, HEMA ('HEMA+'), or extra TEGDMA in a HEMA-free control ('HEMA-'), all added in a 15 wt% concentration. The split-tooth study design involved application in 2E&R mode on one tooth half versus 1SE mode on the corresponding half. Micro-tensile bond strength of half of the micro-specimens was measured upon 1-week distilled water storage ('immediate' 1w μTBS), with the other half measured after additional 6-month storage ('aged' 6 m μTBS). Statistics involved linear mixed-effects (LME) modelling (p < .05). Additionally, interfacial TEM characterization, thin-film (TF) XRD surface analysis, LogP determination, and a cytotoxicity assay were carried out.

RESULTS

FAM-201 revealed significantly higher μTBS than HEMA+ at 1w and 6 m when applied both in E&R and SE bonding modes. HEAA's μTBS was significantly lower than that of HEMA+ at 1w when applied in SE mode. TF-XRD and TEM revealed similar chemical and ultrastructural interfacial characterization, including stable 10-MDP_Ca salt nano-layering. FAM-201 was least cytotoxic and presented with an intermediary LogP, while HEAA presented with the highest LogP, indicating high hydrophilicity and water-sorption sensitivity.

SIGNIFICANCE

The acrylamide co-monomer FAM-201 could replace HEMA in an UA formulation, while HEAA not.

Bonding of Clear Aligner Composite Attachments to Ceramic Materials: An In Vitro Study

Background: We aim to evaluate the effect of surface conditioning, bonding agents and composite types on surface roughness (SR) and shear bond strength (SBS) of clear aligner composite attachments bonded to ceramics. Methods: One hundred and eighty IPS e.max CAD specimens were prepared. For SR, 60 specimens were divided according to surface conditioning (n = 15) into four groups: control, 9.6% hydrofluoric acid (HFA), 37% phosphoric acid (PhA), air abrasion (AA). SR was measured using a Profilometer and Atomic Force Microscopy. For SBS, 120 specimens were divided according to conditioning methods (n = 40) (9.6% HFA and 37% PhA or AA), then according to bonding agents (n = 20) (Assure universal bond (AUB) or Single bond universal (SBU)) and then according to composite type (n = 10): Filtek™ Z350 and Filtek™ Z350 XT flowable composite. SBS was measured using Instron testing machine. Descriptive and group comparison were calculated (p < 0.05). Results: AA had the highest SR, while the control had the lowest SR (p < 0.05). HFA had the highest, but insignificant SBS, followed by AA (p > 0.05). AUB had higher SBS than SBU (p < 0.001). Filtek™ Z350 produced higher SBS than Filtek™ Z350 XT flowable composite (p < 0.01). Conclusion: The combination of AA, AUB, and Filtek Z350 produced the highest SBS, followed by HFA, AUB, and Filtek Z350.

In Vitro Performance of Different Universal Adhesive Systems on Several CAD/CAM Restorative Materials After Thermal Aging

OBJECTIVE

To evaluate the microshear bond strength (mSBS) of 10 universal adhesive systems applied on five different CAD/CAM restorative materials, immediately and after thermal aging.

METHODS AND MATERIALS

Five CAD/CAM materials were selected: 1) feldspathic glass ceramic (FeCe); 2) pre-polymerized reinforced resin composite (ReRC); 3) leucite-reinforced glass ceramic (LeGC); 4) lithium disilicate (LiDi); and 5) yttrium-stabilized zirconium dioxide (ZiDi). For each material, 15 blocks were cut into four rectangular sections (6 × 6 × 6 mm; n=60 per group) and processed as recommended by the respective manufacturer. For each indirect material, the following adhesive systems were applied according to the respective manufacturer's instructions: 1) AdheSE Universal [ADU]; 2) All-Bond Universal [ABU]; 3) Ambar Universal [AMB]; 4) Clearfil Universal Bond [CFU]; 5) Futurabond U [FBU]; 6) One Coat 7 Universal [OCU]; 7) Peak Universal Bond [PUB]; 8) Prime&Bond Elect [PBE]; 9) Scotchbond Universal Adhesive [SBU]; 10) Xeno Select [XEN, negative control]. After the application of the adhesive system, cylinder-shaped transparent matrices were filled with a dual-curing resin cement (NX3) and light cured. Specimens were tested in shear mode at 1.0 mm/ min (mSBS), after 24 hours and 10,000 thermal cycles (TC). All data were submitted to statistical analysis (α=0.05).

RESULTS

For FeCe, there was no significant decrease in mean mSBS for AMB, FBU, and SBU after TC when compared at 24 hours. For ReRC, AMB and SBU showed higher mean mSBS when compared to CFU and XEN, after 24 hours and TC. For LiDi, FBU and OCU showed higher mean mSBS when compared to CFU and XEN, after 24 hours and TC. For LeGC, AMB and PUB showed higher mean mSBS when compared to XEN, after 24 hours and TC. For ZiDi, OCU and SBU showed higher mean mSBS when compared to XEN, after 24 hours and TC. In addition, PBE and XEN showed the lowest mean mSBS after TC with higher percentage of bond strength reduction.

CONCLUSIONS

The mean mSBS among the different universal adhesives varied widely for each CAD/ CAM material used. In addition, most universal adhesives underwent a statistically significant bond strength reduction after TC.

The effect of silane and universal adhesives on the micro-shear bond strength of current resin-matrix ceramics

PURPOSE

The aim of this in vitro study was to evaluate the effect of silane and universal adhesive applications on the micro-shear bond strength (µSBS) of different resin-matrix ceramics (RMCs).

MATERIALS AND METHODS

A total of 120 slides (14 × 12 × 1 mm) were produced from 5 different RMC materials (GC Cerasmart [GC]; Brilliant Crios [BC]; Grandio blocs [GB]; Katana Avencia [KA]; and KZR-CAD HR 2 [KZR]) and sandblasted using 50 µm Al₂O₃ particles. Each RMC material was divided into six groups according to the surface conditioning (SC) method as follows: control (G1), silane primer (G2), silane-free universal adhesive (G3), silane-containing universal adhesive (G4), silane primer and silane-free universal adhesive (G5), and silane primer and silane-containing universal adhesive (G6). Three cylindric specimens made from resin cement (Bifix QM) were polymerized over the treated surface of each slide (n = 12). After thermal cycling (10000 cycles, 5 – 55℃), µSBS test was performed and failure types were evaluated using a stereomicroscope. Data were analyzed using 2-way ANOVA and Tukey tests (α = .05).

RESULTS

µSBS values of specimens were significantly affected by the RMC type and SC protocols (P < .001) except the interaction (P = .119). Except for G2, all SC protocols showed a significant increase in µSBS values (P < .05). For all RMCs, the highest µSBS values were obtained in G4 and G6 groups.

CONCLUSION

Only silane application did not affect the µSBS values regardless of the RMC type. Moreover, the application of a separate silane in addition to the universal adhesives did not improve the µSBS values. Silane-containing universal adhesive was found to be the best conditioning method for RMCs.

The Bond Strength of a Universal Adhesive System with Silane to Lithium Disilicates in Comparison with an Isolated Silane Coupling Agent

PURPOSE

The aim of this in vitro study was to evaluate the effects of different durations of silane coupling agent application compared to a universal adhesive system regarding the shear bond strength of two ceramic materials.

MATERIALS AND METHODS

A total of 120 human molars were ground to the dentinal coronal third and then fixed into an acrylic resin holder. Lithium disilicate specimens were divided into two main groups according to the ceramic type: computer-aided design/computer-aided manufacturing IPS e.max CAD and heat-pressed Initial LiSi Press GC (dimensions of 4 × 3× 3 mm). Each main group was subdivided into 6 subgroups (n = 10) according to the duration of the silane and universal adhesive system application (20, 60, or 120 seconds) on the ceramic surface before cementation; then, the cementation procedures were performed. All specimens were subjected to 5000 thermal cycles at 5 and 55°C before testing. The shear bond strength was measured using a universal testing machine. ANOVA and Scheffe post hoc test multiple comparisons tests were conducted (α = 0.05).

RESULTS

The shear bond strength increased as the duration of the silane and universal adhesive system application increased. The highest bond value for each material was found for the silane application at 120 seconds, with a significant difference between 120 and 60, and 20 seconds for both e. max CAD and Initial LiSi materials (p = 0.029 and p ˂ 0.001, respectively). No significant difference was found between 60 and 20 seconds when silane and universal adhesive system were applied for both e. max CAD and Initial LiSi materials (p = 0.169 and p = 0.120, respectively). All groups treated with the silane primer showed significantly higher values than the universal adhesive system for each application time (p ˂ 0.001).

CONCLUSION

Increasing the duration of the silane coupling agent and universal adhesive system application to 120 seconds on the ceramic surface before cementation improved the shear bond strength of the ceramic-cement interface. Ceramic pretreatment with silane could be an essential step for bonding ceramic to dentin regardless of silane presence in the universal adhesive system.

Bonding ability of resin cements to different types of CAD/CAM composite blocks

This study investigated the bonding performance of two different types of resin cements to computer-aided design/computer-aided manufacturing (CAD/CAM) composite blocks based on the shear bond strength (SBS) test. A silane-containing self-adhesive resin cement (Panavia SA Cement Universal) and resin luting cement (Block HC Cem) with a primer, were used. Specimens were fabricated from three different types of CAD/CAM composite blocks, and their surfaces were blasted with alumina. Resin cements were bonded to the specimens, and their SBSs were measured after 15 min, 24 h, and after being subjected to thermal cycling for 10,000 and 30,000 cycles. Three-way ANOVA for bond strength revealed that CAD/CAM composite block, resin cement and storage time significantly influenced the SBS values, and the three-way interactions between the evaluated factors, and all the interactions were significant. It was concluded that the bonding performance of resin cements to CAD/CAM composite blocks were material and storage period dependent.

Effect of Silane-Containing Universal Adhesives on the Bonding Strength of Lithium Disilicate

The purpose of this study was to investigate the effect of silane-containing universal adhesives on the bonding strength of lithium disilicate. Two-hundred-and-forty lithium disilicate blocks were divided into 16 groups according to the following surface treatments: hydrofluoric acid (HF)-treated or not, silane-treated or not, and the type of universal adhesive used (All-Bond Universal (ABU); Prime & bond (PB); Clearfil Universal Bond (CU); Single bond Universal (SBU)). After surface treatment, resin discs were bonded to each lithium disilicate using dual-cure resin cement. Bonded specimens were stored in distilled water for 24 h and then subjected to microtensile bond strength (μTBS) test. Failure modes were examined under stereomicroscope. Microscopic observation of bonded interfaces was analyzed using scanning electron microscopy. The μTBS data were statistically analyzed. Regardless of silane treatment, all groups treated with HF showed higher bonding strengths compared to those that were not treated with HF (p < 0.05). In groups treated with HF, the bonding strength increased after silane application (p < 0.05) except PB and CU (p > 0.05). Adhesive failures were dominant in all groups, but some mixed failures were observed in ABU treated with HF and silane. While most of the specimens that were not treated with silane after HF application only showed loose bonding between the ceramic and resin cement due to partial gaps, the specimens treated with silane application after HF showed a tight ceramic–resin interface. In conclusion, the silane in universal adhesives did not effectively improve the bonding strength between lithium disilicate and resin cement.

Effect of universal adhesive and silane pretreatment on bond durability of metal brackets to dental glass ceramics

This study aimed to investigate the effect of universal adhesive and silane pretreatment on the bond durability of metal brackets to dental glass ceramics. Eighty lithium disilicate glass ceramic specimens were randomly assigned to one of four groups (n = 20) defined by the pretreatment and adhesive used: (i) Adper Single Bond 2; (ii) silane + Adper Single Bond 2; (iii) Single Bond Universal; and (iv) silane +Single Bond Universal. Maxillary central incisor metal brackets were bonded on the ceramic surfaces with resin composite. A shear bond strength test was conducted after 24 h of water storage and after 10,000 thermocycles. Adhesive remnant index scoring and field-emission scanning electron microscopy were performed to determine adhesives remaining on the ceramic surfaces and the ceramic ultrastructure following bracket debonding, respectively. After 10,000 thermocycles, specimens treated with Single Bond Universal preserved an appropriate bond strength between brackets and glass ceramics and showed minimum ceramic surface damage following bracket debonding, which was not the case in the other three groups. The application of a silane-containing universal adhesive without silane pretreatment achieves adequate durability of the bond of metal brackets to dental glass ceramics and allows safe debonding, which may aid in optimizing the effectiveness for orthodontic treatment.

Optimizing glass-ceramic bonding incorporating new silane technology in an experimental universal adhesive formulation

OBJECTIVE

Incorporating silane-coupling agent into universal adhesives (UAs) to simplify adhesive luting of glass-ceramic restorations appeared ineffective due to silane's instability in an acidic aqueous solution. This study aimed to evaluate new silane technology added to an experimental UA to be bonded to glass ceramics without separate prior silanization.

METHODS

Combined silane technology, consisting of 3-(aminopropyl)triethoxysilane (APTES) and γ-methacryloxypropyltriethoxysilane (γMPTES), was incorporated into an experimental UA formulation, being referred to as ADH-XTE (3M Oral Care). Immediate and aged shear bond strength (SBS) of ADH-XTE onto as-milled ('AM'), tribochemical silica-coated ('TSC'), HF-etched ('HF'), and mirror-polished ('MP') glass-ceramic CAD/CAM blocks (IPS e.max CAD) with/without separate silanization was measured (n = 10/group). The control adhesives included Scotchbond Universal ('SBU') and Scotchbond 1 XT ('SB1-XT'). The glass-ceramic surface topography and the fractography of the SBS-debonded specimens were observed by SEM.

RESULTS

Without separate prior silanization, the experimental UA ADH-XTE, containing combined APTES/γMPTES silane technology, significantly outperformed the glass-ceramic bonding efficiency of its silane-containing SBU precursor, while it performed equally effective as SBU applied with prior silanization. Upon aging, significant reduction in SBS was recorded when ADH-XTE was bonded to TSC glass-ceramic surfaces (p < 0.05), while not to HF ones. Notably, the lowest SBS was obtained when the UAs were bonded to AM and MP glass-ceramic surfaces, in particular when applied without separate prior silanization (p < 0.05).

SIGNIFICANCE

The glass-ceramic bonding capacity of the new combined APTES/γMPTES silane-containing UA ADH-XTE surpassed that of its SBU precursor. HF etching remains needed to durably bond to glass-ceramics.

Effect of different surface treatments and multimode adhesive application on the Weibull characteristics, wettability, surface topography and adhesion to CAD/CAM lithium disilicate ceramic

This paper aims to evaluate the effect of different surface treatments on surface topography, wettability, and shear bond strength of resin cement to glass ceramic.

Bonding Strength of Universal Adhesives to Indirect Substrates: A Meta-Analysis of in Vitro Studies

PURPOSE

To evaluate the in vitro bond strength of universal adhesive systems to indirect substrates.

MATERIAL AND METHODS

Two reviewers performed a literature search up to March 2018 in seven databases: PubMed, Web of Science, SciELO, Scopus, LILACS, IBECS, and BBO. The review included studies that compared the bond strength of universal adhesives and well-established material-specific primers to indirect substrates: lithium disilicate ceramic, yttrium-stabilized zirconium dioxide ceramic, leucite-reinforced ceramic, feldspathic porcelain, polymer infiltrated ceramic material, resin composite or metal alloys. Analyses were carried out using RevMan 5.3.5. A global comparison was performed with the standardized mean difference using a random-effects models at a significance level of p < 0.05.

RESULTS

A total of 45 studies were included in the qualitative analysis, and the meta-analysis was performed with 42 studies. Bond strength to glass-based ceramics and alloys was improved with the use of a specific-primer as separate step before the bonding procedures (lithium disilicate, p < 0.001; alloys, p < 0.001). The bond strength to zirconium substrates was improved with the use of universal adhesives (p < 0.001). For bond strength to composite resin as indirect substrate, universal adhesives performed in a manner similar to that of the material-specific primer (p = 0.11).

CONCLUSIONS

The clinical procedure of luting zirconia and resin composite restorations could be simplified by using single-bottle universal adhesives. However, the ability of universal adhesives to achieve an adequate and durable bond to glass-based ceramics and alloys appears to be limited.

HF etching of CAD/CAM materials: influence of HF concentration and etching time on shear bond strength

Background

The required pretreatment of CAD/CAM ceramic materials before resin composite cement application varies among studies. The aim of the present study was to evaluate the effect of hydrofluoric acid concentration and etching time on the shear bond strength (SBS) of two adhesive and two self-adhesive resin composite cements to different CAD/CAM ceramic materials.

Methods

SBS of two adhesive (Panavia V5, Kuraray, [PV5]; Vita Adiva F-Cem, Vita Zahnfabrik, [VAF]) and two self-adhesive (RelyX Unicem 2 Automix, 3 M Espe, [RUN]; Vita Adiva S-Cem, Vita, [VAS]) cements to four different CAD/CAM materials (Vitablocs Mark II, Vita, [VM]; Vita Enamic, Vita, [VE]; e.max CAD, Ivoclar Vivadent, [EC]; Vita Suprinity PC, Vita, [VS]) was measured. The effect of the surface pretreatment by using two different hydrofluoric acid products (HF5% Vita Ceramics Etch, Vita and HF9% buffered, Ultradent Porcelain Etch, Ultradent Products) were assessed at etching times of 0 s, 5 s, 15 s, 30s and 60s for each cement and restorative material combination (n = 10 per group, total n = 1440).

Results

Significant effects were found for the etching time and cement for all materials with highest shear bond strength for etching times of 60s = 30s = 15 s ≥ 5 s > 0 s and for RUN>PV5 = VAF > VAS (p < 0.05). Etching with HF5% for 5 s to 15 s resulted in higher SBS values, while no differences were observed between HF5% and HF9% buffered when the substrates were etched for 30s to 60s (p < 0.05).

Conclusions

Within the limitations of this study the recommended surface pretreatment of silicate ceramics is HF etching with concentrations of 5% or 9% for 15 s to 60s to achieve highest shear bond strength while the glassy matrix is sufficiently dissolved. The tested resin composite cements can be applied with all tested materials and suggested for clinical application.

Effect of universal adhesives on microtensile bond strength to hybrid ceramic

Background

The aim of this study was to evaluate the effect of universal adhesives (UA) and silane on the microtensile bond strength (μTBS) of resin cement to a hybrid ceramic Vita Enamic (VE).

Methods

VE specimens were acid etched using hydrofluoric acid (HF) and were assigned to three groups (n = 10) based on the applied bonding technique. In group 1 (S), a silane-based primer was used as a surface treatment prior to the application of a resin cement (Variolink Esthetic DC). In group 2, a silane-containing UA, Clearfil Universal Bond (CUB) was used for the surface treatment, and in group 3, A silane-free UA, Tetric N-Bond Universal (TNU) was used for surface treatment. Resin cement build-ups were prepared. The bonded specimens were sectioned into resin-ceramic beams. Half of the beams of each group were stored for 24 h at 37 °C and the other half were subjected to a thermo-cycling aging. The microtensile bond strength (μTBS) was measured at a crosshead speed of 0.5 mm/min. Failure modes were assessed accordingly. Data were analyzed using a) two-way analysis of variance ANOVA followed by one-way ANOVA and Tukey tests between groups and b) independent t-test to detect differences (α = 0.05) for each group. The surface topographies of the ceramic surface were evaluated using scanning electron microscopy.

Results

The results showed that silane-based primer (S) application resulted in significantly higher (p < 0.05) μTBS values after 24 h and after thermocycling compared to both silane-containing UA (CUB) and silane-free UA (TNU). The μTBS values of all groups were significantly reduced after thermocycling. No statistically significant difference was observed between the μTBS of CUB and TNU after 24 h. However, TNU showed significantly higher μTBS after thermocycling. Different failure modes were observed, and adhesive failure was the most common in all groups. Marked surface topographic changes were observed following HF etching.

Conclusion

It is concluded that, the UAs tested cannot be recommended as substitutes to the silanization of Hybrid ceramic.

Silane reactivity and resin bond strength to lithium disilicate ceramic surfaces

OBJECTIVE

To evaluate the silane status in commercially available products and their bonding capacity with polished glass-ceramic surfaces before and after hydrofluoric (HF) acid-etching.

METHODS

The products tested were Calibra Silane Coupling Agent/CS, G-Multi Primer/GM, Kerr Silane Primer/KS, Monobond Plus/MB and Scotchbond Universal Adhesive/SB. The silane status was studied by ¹³C nuclear magnetic resonance spectroscopy (¹³C-NMR). The roughness parameters of polished (group A) and HF acid-etched (group B) lithium disilicate glass-ceramic surfaces were measured by optical profilometry (n = 5/group). The interaction of the products with group A and B ceramic surfaces was examined by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The shear strength (SBS) of a flowable composite bonded to the ceramic surfaces (groups A, B) was assessed before (NS) and after silane treatment (n = 20/group, product).

RESULTS

The NMR analysis showed the presence of silanol monomers only in CS. Methoxylated-siloxane adducts were found in GM, silanol-siloxane adducts in MB, SB, and siloxane polymers in KS. Acid-etching greatly increased Sa, Sz, Sdr, Sc and Sv parameters (p < 0.001) and ATR-FTIR analysis demonstrated evidence of bonding with the substrate in CS. Weibull analysis of SBS revealed the following rankings in characteristic life (p < 0.05): CS > SB,KS,MB > GM > NS (group A) and CS > GM > SB,KS,MB,NS (group B). The most reliable treatment in both groups was CS. For the same silane treatment, the SBS of group B were significantly higher from group A. Failures were mainly of adhesive type, except of several partial resin cohesive failures found in group B.

SIGNIFICANCE

The chemical bonding capacity of the silanes was highest in products with silanol monomers. Acid-etching increased bond strength to a level that neutralized the silane contribution in products with silanol-siloxane adducts and siloxane polymers, providing thus bond strength values similar to silane-free treatments.

Universal dental adhesives: Current status, laboratory testing, and clinical performance

Increasing demand for simplified and user-friendly adhesive systems has led to the development of a new class of adhesives termed as Universal Adhesives (UAs). The term "Universal" reflects manufacturers' claims that these adhesives can be applied with any adhesion strategy and offer the versatility of use with a variety of direct and indirect restorative materials. The aim of this review was to synthesize the literature regarding the current status of UAs, their adhesion potential to various substrates and their performance in different restorative situations. In vitro studies, clinical trials and systematic reviews were identified utilizing controlled vocabulary and keyword searches in Medline and EMBASE databases. About 282 studies (272 in vitro studies; 11 clinical studies) were included. Available laboratory and clinical evidence does not support the claim that UAs can be used with any adhesive strategy. Although, they can chemically bond to various tooth and direct/indirect restorative substrates, the stability of this bond is material-dependent and subject to hydrolytic degradation. Hence, additional measures are still needed to ensure long-term durability. which undermines the versatility of UAs. The lack of long-term data regarding the clinical performance of UAs further complicates clinical decision-making. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2121-2131, 2019.

Efficacy of prostheses bonding using silane incorporated to universal adhesives or applied separately: A systematic review

Currently, the long-term success of esthetic rehabilitation with ceramics is required. Hence, professional knowledge about the most indicated dental material for each clinical situation as well as its usage protocol is essential. The aim of this systematic review of clinical and laboratorial studies was to compare the bond strength of prostheses using silane incorporated to universal adhesives or applied separately. The literature search in databases “Cochrane Library,” “MEDLINE,” “Web of Science,” “Scopus,” “LILACS,” “Scielo,” and “Google Scholar” was based on the keywords “Silane;” “Silanes;” “Silane coupling agent;” “Universal adhesive;” and “Universal adhesives.” A total of five articles were included in this review. In general, the studies showed better results for ceramic etching with hydrofluoric acid and application of silane separately to the universal adhesive. As a conclusion, the treatment with pure silane or as an additional pretreatment with universal adhesives improved the bond strength of glass ceramics. Hence, higher shear bond strength can be achieved, resulting in treatment longevity.

High Bond Durability of Universal Adhesives on Glass Ceramics Facilitated by Silane Pretreatment

Objective:

This study aimed to investigate the long-term effectiveness of ceramic–resin bonding with universal adhesives in non–silane-pretreated and silane-pretreated modes after 10,000 cycles of thermal aging.

Methods and Materials:

All Bond Universal, Adhese Universal, Clearfil Universal Bond, and Single Bond Universal were selected. Etched lithium disilicate glass ceramics were prepared, randomly assigned to groups, and pretreated with or without ceramic primer containing silane coupling agent prior to the application of universal adhesive (ie, silane-pretreated or non–silane-pretreated mode). The shear bond strength (SBS), microleakage, and field-emission scanning electron microscopy images of the ceramic–resin interfaces were examined after 24 hours of water storage or 10,000 thermal cycles. Light microscopy and confocal laser scanning microscopy (CLSM) were performed to analyze marginal sealing ability.

Results:

SBS and microleakage percentage were significantly affected by bonding procedure (non–silane-pretreated or silane-pretreated mode) and aging (24 hours or 10,000 thermal cycles). After the universal adhesives in the non–silane-pretreated mode were aged, SBS significantly decreased and microleakage percentage increased. By contrast, the SBS of Adhese Universal, Clearfil Universal Bond, and Single Bond Universal decreased, and the microleakage percentage of all of the adhesives increased in the silane-pretreated mode. However, after aging, the SBS of the silane-pretreated groups were higher and their microleakage percentages lower than those of the non–pretreated groups. In the non–silane-pretreated mode, adhesive failure was dominant and gaps between composite resin and the adhesive layer were significant when observed with CLSM.

Conclusions:

The simplified procedure reduced the ceramic–resin bonding effectiveness of universal adhesives after aging, and additional silane pretreatment helped improve the long-term durability.

Stability and reactivity of γ-ΜPTMS silane in some commercial primer and adhesive formulations

OBJECTIVES

To evaluate the stability and reactivity of γ-methacryloxypropyl trimethoxysilane (MPTMS) in commercially available primers and adhesives.

METHODS

Four representative primer formulations [Calibra Silane Coupling Agent/Dentsply (CLB), G-Multi Primer/GC (GMP), Kerr Silane Primer/Kerr (KSP), Monobond Plus/Ivoclar Vivadent (MBP)] and a universal adhesive [Scotchbond Universal/3M ESPE (SBU)] containing MPTMS were analyzed spectroscopically. For the stability study, the silanol content was evaluated in bulk solutions as received (reference-RE) and after aging (AG, 48°C/1month) by ¹H, ¹³C, ³¹P NMR and in fresh films by transmission FTIR analysis (TIR, films applied on Ge windows after solvent evaporation). The reactivity, as expressed by the siloxane formation capacity of the RE products, was evaluated by micro-multiple internal reflectance FTIR analysis (MIR, films applied on Ge crystals) after drying and ethanol rinsing (t₀) and following 1 (t₁) and 24h (t₂₄) storage (air/37°C).

RESULTS

NMR and TIR showed ∼60% MPTMS silanol groups in RE-CLB, with the other (∼40%) groups being methylated or ethoxylated. In AG-CLB, the silanol peaks further decreased, while ethoxylation and siloxane derivatization increased. In all other products and aging conditions no silanols were traced and formation of small- and large-size MPTMS derivatives was evident. Apart from the 10-MDP molecule, phosphorous impurities were identified in all RE specimens (2-5%), which after AG reached a maximum value of 15% (MBP). MIR analysis showed siloxane formation in all products, regardless the presence of free silanols (t₁), which further increased at t₂₄ especially in CLB, GMP and MBP.

SIGNIFICANCE

MPTMS silanols are very sensitive to mild thermal aging. Incorporation of MPTMS in the same vials with adhesive and conventional methacrylate monomers, results in derivatization with no detectable silanols, even in fresh materials. The condensates formed may induce additional siloxane formation due to residual activity, which greatly varies among the materials tested. These may have a detrimental effect on MPTMS silanol chemisorption and bonding capacity.

Water-associated attributes in the contemporary dentin bonding milieu

OBJECTIVES

The water-associated attributes of resin-dentin interfaces created by contemporary adhesives are important determinants of bond integrity and stability. In the present work, these attributes were estimated from the perspectives of causality, to examine the behavior of the first and most-recently launched versions of universal adhesives when applied in either the etch-and-rinse mode or the self-etch mode.

METHODS

The immediate cause of interfacial permeability and the time-dependent cause of water sorption were investigated in conjunction with the intermediate effect of interface degradation and the more long-term effect of loss of mechanical strength, before and after thermomechanical cycling. The results were compared with control etch-and-rinse and self-etch adhesives.

RESULTS

Although the introduction of this new class of universal adhesives has brought forth significant changes to the dental adhesion arena, including more application options, reduced bonding armamentarium and increased user friendliness, the water-associated attributes that are critical for making resin-dentin bonds more durable to environmental challenges and less susceptible to degradation have remained unchanged at large, when compared with benchmarks established by former classes of adhesives.

CONCLUSION

It appears that the current trend of adhesive development has brought forth significant changes but lacks the vigor that demarcates progress and technological sublimity.

CLINICAL SIGNIFICANCE

The advent of the user friendly universal adhesives has brought forth significant changes to the dental adhesion arena. However, the elements that are critical for making resin-dentin bonds more durable to environmental challenges and less susceptible to degradation have remained unchanged at large.

Acidic pH weakens the bonding effectiveness of silane contained in universal adhesives

OBJECTIVES

Some silane-containing universal adhesives were introduced that a separate ceramic primer was unnecessary to glass-ceramic bonding because of incorporated silane. We aimed to investigate the effectiveness of silane in universal adhesives with acidic media.

METHODS

A functional γ-methacryloxypropyltrimethoxysilane (γ-MPTS) was used, and its pH value was adjusted to 2.7 by adding hydrochloric acid (HCl) or 10-methacryloxydecyl phosphate (MDP). The prepared acidic silane solutions after 2h or 10d storage were characterized by Fourier transform infrared spectroscopy (FTIR), ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy. Micro-shear bond strength (μSBS) was used to evaluate the bonding performance of glass ceramics. Two silane-containing and two silane-free universal adhesives were included. Field-emission scanning electron microscopy fractography analysis was also performed.

RESULTS

FTIR, ¹H and ¹³C NMR revealed that the hydrolysis of γ-MPTS and the self-condensation reaction of silanol groups occurred over time under acidic conditions (HCl or MDP solution). This reaction formed the siloxane oligomers. For glass-ceramic bonding, the μSBS of acidic silane after 10 d storage was lower than that of silane stored for 2h storage (p<0.05), although the difference among the μSBS of the four universal adhesives were nonsignificant (p>0.05). Additionally, cohesive failure was the main fracture pattern of universal adhesive bonding.

SIGNIFICANCE

The effectiveness of silane contained in low pH universal adhesives can be weakened by dehydration self-condensation and consequently became unstable. For the enhancement of glass-ceramic bonding efficiency with universal adhesives, a separate ceramic primer was recommended.

Adhesive Bonding to Computer-aided Design/ Computer-aided Manufacturing Esthetic Dental Materials: An Overview

AIM

To review the adhesive bonding to different computer-aided design/computer-aided manufacturing (CAD/CAM) esthetic restorative materials.

BACKGROUND

The use of CAD/CAM esthetic restorative materials has gained popularity in recent years. Several CAD/ CAM esthetic restorative materials are commercially available. Adhesive bonding is a major determinant of success of CAD/ CAM restorations. Review result: An account of the currently available bonding strategies are discussed with their rationale in various CAD/ CAM materials.

CONCLUSION

Different surface treatment methods as well as adhesion promoters can be used to achieve reliable bonding of CAD/CAM restorative materials. Selection of bonding strategy to such material is determined based on its composition. Further evidence is required to evaluate the effect of new surface treatment methods, such as nonthermal atmospheric plasma and self-etching ceramic primer on bonding to different dental ceramics.

CLINICAL SIGNIFICANCE

An understanding of the currently available bonding strategies to CA/CAM materials can help the clinician to select the most indicated system for each category of materials.