The Effect of Hydrofluoric Acid Concentration on the Bond Strength and Morphology of the Surface and Interface of Glass Ceramics to a Resin Cement

Effect of Combined Application of Hydrofluoric and Phosphoric Acids and Active Irrigation with a Microbrush on Shear Bond Strength of Lithium Disilicate Ceramics to Enamel

Background

This study assessed the effect of combined application of hydrofluoric (HF) acid and phosphoric acid (PA) and active irrigation (AI) with a microbrush on shear bond strength (SBS) of lithium disilicate (LDS) ceramics to enamel.

Materials and Methods

This in vitro study was conducted on 40 extracted teeth that received enamel preparation with a #12 cylindrical bur. Forty IPS e.max LT rods (3mm diameter, 6mm height) were fabricated and randomly assigned to four groups (n = 10) for surface treatment with 5% HF (group 1), 5% HF and AI with a microbrush for 20 seconds (group 2), 5% HF and 32% PA (group 3), and 5% HF and 32% PA plus AI with a microbrush for 20 seconds (group 4). Silane and Choice 2 cement were used for bonding rods to enamel. The SBS was measured by a universal testing machine. Data were analyzed by two-way analysis of variance (ANOVA), Bonferroni, and Chi-square tests (alpha = 0.05).

Results

Group 4 had the highest SBS, and group 1 had the lowest SBS (P < 0.05). Group 2 had a significantly higher SBS than group 1, and group 4 had a significantly higher SBS than group 3. AI with a microbrush significantly increased the SBS (P < 0.05), but the application of PA caused no significant change in SBS (P > 0.05). The interaction effect of PA and AI on SBS was not significant (P > 0.05).

Conclusion

The application of PA in addition to 5% HF acid caused no significant change in the SBS of LDS ceramic to enamel. However, AI with a microbrush significantly increased the SBS.

Clinical performance of laminate veneers: A review of the literature

PURPOSE

This narrative review aimed to survey the clinical outcomes of laminate veneers (LVs), including their survival and success rates.

STUDY SELECTION

An electronic search of MEDLINE/PubMed, Web of Science, Cochrane Library, and Google Scholar from 2000 to April 2023 was conducted using the keywords "laminate" OR "veneer" OR "porcelain" OR "feldspathic" OR "lithium disilicate" OR "composite resin" OR "zirconia" OR "survival" OR "success." Case reports, case series, reviews, abstracts, in vitro studies, and observational studies were excluded. Five researchers independently evaluated the titles and abstracts of all identified studies.

RESULTS

A total of 55 studies were identified. None of the studies met the criteria for zirconia LVs. According to the studies in this review, LVs fabricated with feldspathic porcelain, leucite-reinforced glass ceramics (LRG), and lithium disilicate ceramics (LDS) exhibited satisfactory survival and success rates. Furthermore, hydrofluoric acid etching followed by silane priming of the surface of ceramic LVs is necessary for improved clinical outcomes. The extent of dentin exposure significantly decreases the success rate of ceramic LVs. An appropriate adhesive luting process is required to achieve the long-term success of ceramic LVs. Dentin exposure should be minimized or sealed during tooth preparation to achieve a reliable and durable bond between LVs and abutment teeth.

CONCLUSIONS

Based on this narrative review of the literature, the use of silica-based ceramic feldspathic porcelain, LRG, and LDS is recommended for LVs.

Effect of different surface treatment protocols on the bond strength between lithium disilicate and resin cements

Because the use of hydrofluoric acid (HF) poses health risks if handled improperly, many clinicians prefer to have the ceramic restorations pre-etched in dental laboratories. However, during the try-in procedure, the pre-etched glass-ceramic restorations may be contaminated with saliva resulting in reduced bond strength. This in-vitro study aimed to investigate the effect of different surface treatments on the bond strength of lithium disilicate (LD) glass-ceramic restorations (IPS e.max Press, Ivoclar Vivadent) to two resin cements. One-hundred eighty blocks (4X4X3mm) of LD glass-ceramic were divided into twelve groups (n = 15), of which six received Variolink Esthetic DC (VE) cement and six received RelyX Ultimate (RU) cement, following the surface treatments: G1) Control: Hydrofluoric Acid + Silane (HF + Sil); G2) Hydrofluoric Acid + Saliva + Silane (HF + S + Sil); G3) Hydrofluoric Acid + Saliva + Ivoclean + Silane (HF + S + IC + Sil); G4) Hydrofluoric Acid + Saliva + Phosphoric Acid + Silane (HF + S + P + Sil); G5) Hydrofluoric Acid + Saliva + Monobond Etch & Prime (HF + S + EP); G6) Monobond Etch & Prime (EP). Following treatment, a resin-cement cylinder (2.3 mm diameter) was built on the glass-ceramic surface, photocured (20 s), stored in distilled water (37 °C, 24 h) and submitted to the shear bond strength test. Bond strength data (MPa) were subjected to two-way ANOVA and Tukey (α = 0.01). Cement type and surface treatment had a significant effect on the bond strength (p < 0.001) (Table 4). Single-step Monobond Etch & Prime (EP) significantly improved the bond strength of resin-cements to glass-ceramic with and without saliva contamination.

Interfacial fracture toughness of different surface treatments on zirconia-reinforced lithium silicate glass-ceramics

This study investigated the influence of different surface treatments on unfiring or firing zirconia-reinforced lithium silicate (ZLS) glass-ceramics. Celtra Duo and IPS e.max CAD blocks were cut and process following manufacturer protocols. The specimen surface was treated with seven different protocols. Two ceramic blocks with the same surface treatment were bonded with luting agent and prepared for mini-interfacial fracture toughness tests (mini-iFT). The specimens were tested after 1-week storage. The data was statistically analyzed using two-way ANOVA and Dunnett's T3 comparison (α=0.05). The highest mini-iFT of both Celtra Duo unfired and fired was shown in the HF+S group, which was not significantly different from HF+S+UA. For IPS e.max CAD, the mini-iFT was higher in the groups treated with hydrofluoric acid. Additional adhesive after silane application did not significantly improve bonding effectiveness. Therefore, surface treatment with hydrofluoric acid and silane is recommended for both unfiring and firing ZLS glass ceramics.

Effects of Hydrofluoric Acid Concentrations, Commercial Brands, and Adhesive Application on the Bond Strength of a Resin Luting Agent to Lithium Disilicate Glass Ceramic

OBJECTIVES

To evaluate the surface topography/roughness and bond strength of a resin luting agent to a lithium disilicate glass ceramic after etching with different concentrations of hydrofluoric acid (HF) and commercial brands.

METHODS

For bond strength evaluation, 260 lithium disilicate glass ceramic (EMX) discs were randomly distributed into 13 groups based on concentrations of HF and commercial brands (n=20): 5% and 10%, Lysanda (LY5 and LY10); 5% and 10%, Maquira (MA5 and MA10); 5% and 10%, FGM (FG5 and FG10); 4.8%, Ivoclar Vivadent (IV5); 5% and 10%, PHS do Brasil (PH5 and PH10); 5% and 10%, BM4 (BM5 and BM10); 9%, Ultradent Inc (UL10); and Dentsply (DE10). A further random distribution (n=10) was made based on the application (+) or absence (-) of an adhesive layer. Resin luting agent cylinders (1 mm in diameter) were added on EMX surfaces, light-cured, and stored for 24 hours in deionized water at 37°C. On a universal testing machine (DL 500, EMIC), specimens were submitted to a microshear bond strength test at a crosshead speed of 1 mm/min until failure. A representative etched EMX disc from each group underwent surface topography analysis using field-emission scanning electron microscopy (n=1), and five (n=5) etched EMX discs from each group were tested for surface roughness. Data were statistically analyzed using analysis of variance and Tukey test (α=0.05).

RESULTS

A less conditioned and smoother surface was observed for 5% HF compared to 10%. Additionally, commercial brands of HF were shown to affect bond strength. When the adhesive layer was not used (-), a 10% concentration promoted higher bond strengths to EMX. However, when adhesive was applied (+), the concentrations of HF and commercial brands had no effect on bond strength results.

CONCLUSIONS

A 10% concentration of HF results in higher bond strength than a 5% concentration. If an adhesive layer is applied, neither this distinction nor the influence of commercial brands is observed.

Different surface treatment strategies on etchable CAD-CAM materials: Part II-Effect on the bond strength

STATEMENT OF PROBLEM

Bonding to recently launched polymer-based computer-aided design and computer-aided manufacturing (CAD-CAM) materials has been challenging. Evidence regarding etching strategies for dual-phase CAD-CAM materials is sparse, but adequate bonding is crucial for the clinical success and longevity of a restoration.

PURPOSE

The purpose of this 2-part in vitro study was to evaluate and compare the effect of surface treatment strategies on the microshear bond strength and work of adhesion of polymer-based and ceramic materials. In addition, chemical elements present on the surface and the interface morphology after using those strategies were also assessed.

MATERIALS AND METHODS

Two CAD-CAM polymer and 1 CAD-CAM ceramic materials were selected for this in vitro study. The materials were subjected to different surface treatment strategies, including airborne-particle abrasion and the application of 9% hydrofluoric acid. Specimens were submitted to microshear bond strength before and after thermocycling, and the failure mode was classified. The work of adhesion was calculated based on the water-to-air surface tension of 72.8 mN.m-1 and the Young- Dupré equation. The surfaces were submitted to energy-dispersive X-ray spectroscopy, and the interfaces were analyzed using a scanning electron microscope. Data were subjected to 2-way ANOVA and the Tukey post hoc test (α=.05).

RESULTS

The highest microshear bond strength means were observed for the polymer-based materials when hydrofluoric acid or airborne-particle abrasion was applied. The 3 materials tested showed a decrease in microshear bond strength after thermocycling, except for applying airborne-particle abrasion to 1 of the polymer-based material tested. The ceramic material tested showed a high microshear bond strength with the application of airborne-particle abrasion and hydrofluoric acid combined. The work of adhesion varied across the materials and presented high means when hydrofluoric acid was used.

CONCLUSIONS

A combination of airborne-particle abrasion plus hydrofluoric acid should be considered for polymer-based or feldspathic ceramic CAD-CAM materials. In this in vitro study, both etching procedures combined produced higher bonding values for all materials tested.

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.

Fracture load of ultrathin occlusal veneers: Effect of thickness and surface conditioning

OBJECTIVE

This in-vitro study is planned to analyze the effect of different thicknesses of ceramic occlusal veneers and different surface treatments on fracture resistance.

MATERIALS AND METHODS

A total of 48 sound mandibular molars are anatomically prepared from the occlusal surface with two different thicknesses (1.0 and 0.5 mm). CAD/CAM zirconia-reinforced glass ceramic blocks (Vita Suprinity) are used for fabricating occlusal veneers. The teeth are randomly divided into two primary groups A and B (n=24) according to occlusal veneer thickness. Each group is subdivided according to surface conditioning into three equal subgroups (n=8)-subgroup HF: etching with hydrofluoric acid and ceramic primer application; subgroup APF: etching with acidulated phosphate fluoride and ceramic primer application; subgroup EP: conditioning with etch and prime only. Dual-cure adhesive resin cement (Multilink Automix) is utilized to adhesively bond the veneers. All specimens are subjected to 240,000 cycles of dynamic load aging prior to the fracture resistance test. The fracture resistance is measured in Newton (N). The Failure mode patterns are analyzed and categorized using a scanning electron microscope (SEM). The results are analyzed using a two-way ANOVA with Bonferroni's Post-Hoc test, followed by a one-way ANOVA for each factor. That is in addition to one-way ANOVA for surface treatment under each thickness, each followed by Bonferroni's Post-Hoc test. Then, a T-test is used to compare the two thicknesses under each surface treatment. All tests are set at 0.05 significance level.

RESULTS

The two-way ANOVA test revealed that restoration thickness and surface treatment both significantly affect the fracture resistance values (p<0.05). The highest fracture resistance mean (2672±216N) is obtained from HF at 1.0 mm thickness, while the lowest mean (2104±299N) is obtained from APF at 0.5 mm thickness.

CONCLUSION

All test groups, regardless of thickness, demonstrated fracture resistance values that exceeded both normal and parafunctional bite forces. The veneers that bonded after hydrofluoric acid etching followed by ceramic primer application showed more favourable fracture patterns.

Do different protocols affect the success rate or bond strength of glass-ceramics repaired with composite resin? A systematic review and meta-analysis

STATEMENT OF PROBLEM

Intraoral repair techniques prevent unnecessary replacement of ceramic restorations, thereby increasing the survival rate. However, adhesion between ceramics and the composite resin is challenging and how different protocols influence adhesion is unclear.

PURPOSE

The purpose of this systematic review and meta-analysis was to analyze the influence of different protocols on repairing glass-ceramic surfaces with composite resins.

MATERIAL AND METHODS

PubMed, Scopus, ISI Web of Science, and Embase electronic databases were searched to select studies comparing bond strength values or survival rates of glass-ceramic repaired with composite resins using different surface treatment protocols. No publication year or language restriction was applied. Data sets were extracted from all included studies, and the mean differences calculated. A 95% confidence interval was calculated by using the random effect model (Rev Man 5.4).

RESULTS

The search identified 5037 studies, and 165 were assessed for eligibility. Finally, 123 in vitro studies were included in the systematic review and 48 in the meta-analysis. Considering different glass-ceramics, bond strength tests, and aged or not aged specimens, 37 meta-analyses found the effect of repair protocols: only adhesive, silane plus adhesive alone or preceded by hydrofluoric (HF) acid, airborne-particle abrasion (APA) with Al2O3 particles, silica-coated APA (SCAPA), diamond rotary instrument (DRI), and laser irradiation (LI).

CONCLUSIONS

For feldspathic porcelain, HF acid, APA, SCAPA, or DRI improved the repair micromechanical retention; applying silane is essential to HF-conditioned surfaces but the use of adhesive is optional when silane is applied. Results for leucite and lithium disilicate were inconclusive in terms of suggesting a treatment other than HF acid plus silane and adhesive applications.

Effect of the region of the CAD/CAM block on the flexural strength and structural reliability of restorative materials

The aim of the study was to evaluate whether the region (internal or external) of the CAD/CAM block influences the mechanical performance of restorative materials. Blocks of different CAD/CAM materials (Composites: KAV - Katana Avencia; LULT - LULT Ultimate; Ceramics: ENAM - Vita Enamic; NICE - N!CE; EMP - IPS Empress CAD; VMII - Vita Mark II; EMAX - IPS e.max CAD) were selected, and direct resin composite blocks (APX - Clearfil AP-X; FSUP - Filtek Supreme) were built using the incremental technique on a mold from one of the CAD/CAM blocks. All blocks were sectioned into bar-shaped specimens (1 × 1 × 14 mm), which were separated into two groups according to the region of the block (inside or outside). 3-point bending tests were performed following ISO 6872:2015 and flexural strength data were analyzed using one-way ANOVA and Bonferroni post-hoc tests (p < 0.05). Weibull module and characteristic strength were also calculated. In general, the mean flexural strength values were not statistically different (p > 0.05) between the inside and outside regions of each material, except for LULT (inside > outside) and EMAX (outside > inside). Comparing the materials, a similar strength (only discrete variations) was observed for inside, outside or merged (inside and outside data assembled together) regions: EMAX > KAV = LULT > NICE = APX > EMP = ENAM = VMII ≥ FSUP (merged condition). Characteristic strength at 63.2% failure probability and at 5% failure probability generally corroborates such observations. There were no statistical differences for Weibull module data (inside, outside, or merged), except for KAV and NICE (outside > inside). Thus, the region from where the restoration is milled within the CAD/CAM block generally does not influence the mechanical performance hereof (flexural strength, failure probability, risk of premature failures, and mechanical reliability) of the material, except for LULT and EMAX.

Bond strength to different CAD/CAM lithium disilicate reinforced ceramics

OBJECTIVE

To evaluate the microstructure and the influence of applying universal adhesive only versus universal adhesive with additional silane application on shear bond strength (SBS) to four different lithium disilicate ceramic (LDC) materials.

MATERIAL AND METHODS

Specimens (n = 240, 1.5 mm thick) cut from four different CAD/CAM materials were polished and etched with 4.5% hydrofluoric (HF) acid according to manufacturers' instructions (20 s: IPS e.max CAD, n!ce; 30 s: Amber Mill, CEREC Tessera). For cementation, either universal adhesive only or silane + universal adhesive were applied before prefabricated composite cylinders were cemented using a dual-cure resin cement. SBS testing was performed either after 24 h or after 20,000 cycles thermocycling +2 months water storage. Surfaces were analyzed with stereomicroscope for failure mode and with scanning-electron microscopy for microstructure of the LDC. Statistical analysis of the data was performed with non-parametric tests at α = 0.001.

RESULT

SBS values for non-aged specimens ranged from 29.08 to 17.87 MPa and for aged specimens from 22.24 to 3.01 MPa. SBS was significantly reduced when silane was omitted after aging, (p < 0.001). Failure mode was mostly mixed with some cohesive failures in the LDC.

CONCLUSION

Bond strengths are highly affected by the CAD/CAM LDC and their microstructures. The application of silane after hydrofluoric etching is still essential to obtain long-term bonding, irrespective of the presence of silane in the universal adhesive. Water degradation can significantly affect long-term bonding to novel LDC.

CLINICAL SIGNIFICANCE

When using a universal adhesive for bonding to LDC restorations, the best long-term bond is achieved if an additional application of silane precedes the universal adhesive.

Phase Formation, Mechanical Strength, and Bioactive Properties of Lithium Disilicate Glass-Ceramics with Different Al2O3 Contents

Owing to its excellent mechanical properties and aesthetic tooth-like appearance, lithium disilicate glass-ceramic is more attractive as a crown for dental restorations. In this study, lithium disilicate glass-ceramics were prepared from SiO₂-Li₂O-K₂O-P₂O₅-CeO₂ glass systems with various Al₂O₃ contents. The mixed glass was then heat-treated at 600 °C and 800 °C for 2 h to form glass-ceramic samples. Phase formation, microstructure, mechanical properties and bioactivity were investigated. The phase formation analysis confirmed the presence of Li₂Si₂O₅ in all the samples. The glass-ceramic sample with an Al₂O₃ content of 1 wt% showed rod-like Li₂Si₂O₅ crystals that could contribute to the delay in crack propagation and demonstrated the highest mechanical properties. Surface treatment with hydrofluoric acid followed by a silane-coupling agent provided the highest micro-shear bond strength for all ceramic conditions, with no significant difference between ceramic samples. The biocompatibility tests of the material showed that Al₂O₃-added lithium disilicate glass-ceramic sample was bioactive, thus activating protein production and stimulating the alkaline phosphatase (ALP) activity of osteoblast-like cells.

Influence of Fit-checking Material and Cleaning Protocols on the Bond Strength of Lithium Disilicate Glass-ceramics

Objectives

To evaluate the bond strength of a resin luting agent to a lithium disilicate glass-ceramic after the use of different fit-checking materials and cleaning protocols.

Methods and Materials

Two hundred and forty-two (242) ceramic specimens were etched with 5% hydrofluoric acid for 20 seconds and distributed into 22 groups (n=10), in total. Four (4) groups were created based on fit-checking material and that had no following cleaning protocol: no fit-checking material used (control group); articulating paper; articulating spray; and fit-checker liquid. For each fit-checking material (3), 6 cleaning protocols were tested creating an additional 18 groups (n=10): air/water spray; 70% alcohol (ethanol); acetone; 35% phosphoric acid; 5% hydrofluoric acid; and a commercially available cleaning paste (Ivoclean, Ivoclar Vivadent). Silane and bonding resin were applied to all ceramic surfaces. Resin luting agent cylinders (1 mm in diameter) were created using silicone matrices, light-cured, and specimens were stored in deionized water at 37°C for 24 hours. Microshear bond strength test (μSBS) was performed on a universal testing machine (DL 500, EMIC) at a crosshead speed of 1 mm/min until failure. Results were statistically analyzed using ANOVA and Tukey’s test (α=0.05).

Results

Articulating paper and fit-checker liquid, when not properly removed, negatively affected the bond strength (p&lt;0.05). None of the tested cleaning protocols were effective for articulating paper (p&lt;0.05). There was no significant difference in bond strength after the cleaning protocols between articulating spray and fit-checker liquid when compared to the control group (no contamination) (p&gt;0.05).

Conclusion

The cleaning protocols tested can effectively restore the bond strength of resin luting agents to lithium disilicate ceramics that were exposed to articulating spray or fit-checker liquid. The use of articulating paper is not recommended for fit-checking indirect lithium disilicate restorations.

Replacement of Congenitally Missing Maxillary Lateral Incisor with Two-Buccal-Retainer Resin-Bonded Fixed Dental Prosthesis Modified by Proximal Boxes

A 21-year-old male patient with congenitally missing maxillary right lateral incisor presented to Fixed Prosthodontics Department at the Faculty of Dentistry, Damascus University (Damascus, Syria). A two-buccal-retainer lithium disilicate glass-ceramic resin-bonded fixed dental prosthesis (RBFDP) was chosen to replace the missing tooth. This clinical report describes a novel preparation design of two-buccal-retainer lithium disilicate glass-ceramic RBFDP modified by proximal boxes. A recall appointment after 3 years showed no fracture, no de-bonding, no secondary caries, and no staining in prosthesis margins. Color matching with natural teeth was excellent, and the patient was satisfied.

Do preheated composite resin or adhesive resin layer strengthen the feldspar ceramic?

STATEMENT OF PROBLEM

Preheated composite resin and adhesive coating have been recommended as luting agents for ceramic veneers; however, information about the mechanical behavior of feldspathic porcelain veneers after using these methods is still limited.

PURPOSE

The purpose of this in vitro study was to evaluate the influence of the use of preheated composite resin or an adhesive resin layer on the strengthening of a feldspathic porcelain.

MATERIAL AND METHODS

Feldspathic porcelain disks were fabricated (N=210), etched (10% hydrofluoric acid for 90 seconds), and bonded according to resin-based luting agents (30 per group) for the biaxial flexural strength tests: photopolymerized resin cement, flowable composite resin, preheated composite resin, with or without previous adhesive coating. Characteristic strength and Weibull modulus were calculated. The viscosity of the luting agents was measured by using isothermal analyses. Finite element analysis simulated the flexural test. Fractographic and bonded interfaces were observed.

RESULTS

The use of preheated composite resin led to the lowest stress levels in the feldspathic porcelain veneers. However, it did not increase the ceramic strengthening compared with other luting agents, as higher values were observed with flowable composite resin (P<.05). The use of an adhesive resin layer had no significant effect on ceramic strengthening when associated with preheated composite resin or resin cement (P>.05). Preheated composite resin presented the highest viscosity and led to incomplete filling of the porcelain surface irregularities. Failures originated on the ceramic surface subjected to tensile stress and were typically associated with pores at the ceramic-luting agent interface.

CONCLUSIONS

The use of preheated composite resin or an adhesive resin layer did not have a positive effect on strengthening feldspathic porcelain.

Adhesive application after ceramic surface treatment is detrimental to load-bearing capacity under fatigue of a lithium disilicate glass-ceramic

OBJECTIVE

To evaluate whether an adhesive application after surface treatment on a lithium disilicate ceramic (LD) has an influence on its load-bearing capacity under fatigue.

METHODS

LD discs (Ø= 10 mm; thickness= 1 mm) were allocated into 8 groups (n= 15), considering 3 factors: "ceramic surface treatment" - HF: hydrofluoric acid + universal primer application; or MEP: single-component ceramic primer; "adhesive application" - with or without; and "aging protocol" - baseline: 24 h to 7 days; or aging: 180 days of storage + 25,000 thermal cycles. The LD discs were adhesively bonded to glass fiber-reinforced epoxy resin discs (Ø= 10 mm; thickness= 2 mm) and stored according to the condition and each group. Cyclic fatigue testing (initial load= 100 N; step size= 100 N until600 N and after step size= 25 N to failure; 10,000 cycles/step; 20 Hz frequency) was performed. Fractographic and adhesive interface analyzes were also performed. The collected data were then analyzed by Kaplan Meier and Mantel-Cox tests and One-way ANOVA.

RESULTS

The adhesive application in the baseline condition had no influence on the load-bearing capacity under fatigue when the HF surface treatment was performed, however, adhesive application for the MEP treatment led to worse results than without it. The adhesive application in the aged condition showed worse fatigue outcomes for both treatments. All specimens presented radial cracks. MEP treatment followed by adhesive application presented the thickest luting layer.

CONCLUSION

The adhesive application after surface treatments of a lithium disilicate glass-ceramic is detrimental to its load-bearing capacity under fatigue when adhesively luted onto a supporting substrate.

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.

Adhesion to a Zirconia-reinforced Lithium Silicate Ceramic: Effects of Ceramic Surface Treatments and Resin Cements

OBJECTIVE

This study had the objective to test the effect of ceramic surface treatments on the microshear bond strength (μSBS) of different resin cements to a zirconia-reinforced lithium silicate (ZLS).

METHODS AND MATERIALS

ZLS blocks were sectioned, embedded in acrylic resin, and then allocated into nine groups considering two study factors: "ceramic surface treatment" (HF - hydrofluoric acid; EP - self-etching primer; TBS - tribochemical silica coating) and "resin cements" (nMDP - without MDP monomer; MDP - with MDP monomer; SA - self-adhesive). Starch tubes (n=36) were placed on the treated ceramic surface and the cement was applied. Starch tubes were removed after 24 hours of storage, and the specimens were thermocycled (5,000×; 5°C-55°C). Next, the μSBS test was performed using the wire-loop technique, and topographic and failure analyses were performed.

RESULTS

The factors "ceramic surface treatment" and "resin cement" statistically influenced the μSBS results. Considering the surface treatment factor, the TBS produced statistically lower values when the MDP resin cement was applied, being only similar to the MDP plus EP group. For the resin cement factor, no difference was found for nMDP and SA groups, apart from the surface treatments. Failure analysis showed that the groups treated with EP had a greater number of pre-test failures. The surface treatments induced noteworthy topographic alterations when compared to control (no treatment).

CONCLUSION

The ZLS ceramic surface treatment with tribochemical silica coating associated with the MDP-containing resin cement resulted in lower bond strength values.

Evaluation of Cleaning Methods on Lithium Disilicate Glass Ceramic Surfaces After Organic Contamination

The purposes of this study were to 1) evaluate the effectiveness of different cleaning methods from a previously etched and silanized lithium disilicate glass ceramic (EMX) surface after contact with organic fluids (saliva or human blood) and 2) assess the effect of applying a new silane layer after the cleaning methods on the microshear bond strength (mSBS) of resin cement to EMX. EMX discs were etched with 5% hydrofluoric acid (HF) and properly silanized. Three control groups were created (n=10): control (without contamination), saliva positive, and human blood positive. Later, after new contaminations, the samples were distributed into four groups according to the cleaning method (n=20): air–water spray (AWS), 35% phosphoric acid, 70% alcohol, or Ivoclean cleaning paste. After the cleaning methods, subgroups were submitted to a new silane layer application, or not (n=10). All samples received a thin layer of a bonding agent and, subsequently, three light-cured resin cement cylinders were prepared on each EMX surface for the mSBS test. This test was performed on a universal testing machine at a vertical speed of 1 mm/minute until rupture. Contaminated and cleaned silanized EMX surfaces were assessed by scanning electron microscopy (SEM) (n=1). The noncontaminated control group showed an average mSBS of 18.7 MPa, and the positive saliva and human blood control groups yielded a 34% and 42% reduction in bond strength, respectively, compared to the uncontaminated control (p&lt;0.05). For saliva-contaminated surfaces, all cleaning methods were effective and not different from one another or the control group (p&gt;0.05). However, for human blood contamination, only Ivoclean cleaning paste was effective in restoring μSBS to uncontaminated control group levels (p&gt;0.05). SEM images showed a clean surface (ie, with no contaminant residues) after the cleaning methods, regardless of the organic contaminant type. All the assessed cleaning methods were effective in removing saliva from the silanized EMX surface; however, only Ivoclean was able to restore the adhesion quality when the silanized EMX surface was contaminated with human blood.

Surface Treatment and Cementation of Lithium Silicate Ceramics Containing ZrO2

Objective

To evaluate the effect of different surface treatments on the shear bond strength (SBS) of lithium silicate (LS) and lithium disilicate (LD) ceramics, after thermocycling.

Methods and Materials

For SBS test, 72 ceramic blocks (18×14×2 mm) were made (24 blocks from each ceramic material): VITA Suprinity (LSS), Celtra Duo (LSC), and Lithium disilicate (LD). The blocks were polished with sandpaper of increasing grit (#280, #400, #800, and #1200) and embedded in chemically activated acrylic resin. Afterwards, they were randomly divided into 12 groups (6 blocks per group) according to: “Ceramic” (LD, LSC, and LSS) and “Surface treatment” (HFS: hydrofluoric acid + silane; MEP: Monobond Etch & Prime/Ivoclar). From each treated surface ceramic block, four dual-curing resin cement cylinders (RelyX U200, 3M Oral Care) were prepared using a Tygon tube (Ø=3 mm and h=2 mm) and light cured for 40 seconds (1000 mW/cm2) (N=288/n=24). All specimens were submitted to thermocycling (10,000 cycles, 5°C and 55°C, 30 seconds) and then to SBS test at a crosshead speed of 1 mm/min using a 50-kgf load cell. Forty-five additional blocks were made for roughness and SEM analysis. Failure mode was also performed. The data (MPa) were statistically analyzed by oneway analysis of variance (ANOVA), Tukey test (5%), and Weibull analysis. The Ra was analyzed by Kruskal–Wallis and Dunn Test (5%). The other variables were analyzed qualitatively.

Results

ANOVA revealed that “surface treatment” was significant for all ceramic materials (p&lt;0.05). The LD-HFS (18.66±3.49), LSC-HFS (16.81±2.62), and LSS-HFS (16.33±3.08) groups had significantly higher SBS than the LD-MEP (7.00±4.2), LSC-MEP (14.12±3.51), and LSS-MEP (13.87±2.52) groups. Complete adhesive failures at the cement– dentin interface were more frequent. Weibull modulus was superior for the LD-HFS (6.22), LSC-HFS (8.8), and LSS-HFS (7.4) groups.

Conclusion

HF followed by silanization is the most suitable surface treatment for the cementation of LS and LD glass ceramics.

The Effect of Different Surface Conditioning Techniques on the Bonding between Resin Cement & Ceramic

Surface etching before cementation is a vital step that determines the clinical performance of ceramic restorations. Etching alters surface topography that contributes effective bonding between ceramic restoration and resin cement. This study aimed to compare etching techniques to determine the most effective etching method contributing the highest bond strength that helps in improving dental implants. Materials and methods: sixty discs of feldspathic ceramic measuring 10 mm diameter and 4 mm thickness were prepared. The 60 samples were divided into four equal groups based on the surface treatment technique used: group A: 9.6% hydrofluoric acid; group B: coarse diamond burs; group C: CO2 laser; and group D: no treatment. Ceramic disc specimens were examined under a Scanning Electron microscope (SEM) after surface treatment to characterize their surface morphology. Further, the specimens were luted with a resin luting agent and incubated for 24 h at a temperature of 37 °C simulating the oral environment. After 24 h, shear bond strength (SBS) and the nature of bond failure was determined for each specimen using a universal Instron testing machine. Results: significant change in surface morphology was noticed on hydrofluoric acid treatment forming larger irregular roughness (4.83 ± 1.78 µm) with multiple patterns of grooves and pores compared to other groups. Further, the highest SBS value was measured on hydrofluoric acid etching that display the highest bond strength due to the high surface roughness. In conclusion, our findings report a strong association between the surface roughness and bond strength upon hydrofluoric acid compared to other methods. Further work in this direction will enhance the utility of the etching technique on the improvement of dental implants.

Surface Treatment Effect on Shear Bond Strength between Lithium Disilicate Glass-Ceramic and Resin Cement

OBJECTIVE

 The study aimed to evaluate the shear bond strength (SBS) of lithium disilicate glass-ceramic (LDGC) and resin cement (RC) using different surface treatments.

MATERIALS AND METHODS

 LDGC blocks (Vintage LD Press) were prepared, etched with 4.5% hydrofluoric acid, and randomly divided into seven groups (n = 10), depending on the surface treatments. The groups were divided as follows: 1) no surface treatment (control), 2) Silane Primer (KS), 3) Signum Ceramic Bond I (SGI), 4) Signum Ceramic Bond I/Signum Ceramic Bond II (SGI/SGII), 5) experimental silane (EXP), 6) experimental silane/Signum Ceramic Bond II (EXP/SGII), and 7) Experimental/Adper Scotchbond Multi-purpose Adhesive (EXP/ADP). The specimens were cemented to resin composite blocks with resin cement and stored in water at 37 °C for 24 hours. The specimens underwent 5,000 thermal cycles and were subjected to the SBS test. Mode of failure was evaluated under the stereo microscope.

STATISTICAL ANALYSIS

 Data were analyzed with Welch ANOVA and Games-Howell post hoc tests (α = 0.05).

RESULTS

 The highest mean SBS showed in group EXP/ADP (45.49 ± 3.37 MPa); however, this was not significantly different from group EXP/SGII (41.38 ± 2.17 MPa) (p ≥ 0.05). The lowest SBS was shown in the control group (18.36 ± 0.69 MPa). This was not significantly different from group KS (20.17 ± 1.10 MPa) (p ≥ 0.05).

CONCLUSIONS

 The different surface treatments significantly affected the SBS value between LDGC and RC. The application of pure silane coupling agent with or without the application of an adhesive improved the SBS value and bond quality.

Comparison between Hydrofluoric Acid and Single-Component Primer as Conditioners on Resin Cement Adhesion to Lithium Silicate and Lithium Disilicate Glass Ceramics

This study aimed at evaluating the effects of different surface conditionings on the microshear bond strength (µSBS) of a self-adhesive resin cement to VITA Suprinity (ZLS) and IPS e.max CAD (LD). Three surface conditioning protocols were performed on ZLS and LD before luting with a self-adhesive resin cement (RelyX Unicem 2, RXU): hydrofluoric acid (HF), HF + silane (HF + S), or Monobond Etch & Prime (EP). In each group, 15 cylindrical buildups of RXU were prepared on five milled bars and submitted to a µSBS test. Data were statistically analyzed with two-way ANOVA and Tukey’s post hoc test (p < 0.05). Failure modes were recorded and classified as adhesive, mixed, cohesive in resin, or ceramic, and statistically analyzed with Fisher’s exact test (p = 0.05). One additional bar per group was used for the morphological characterization of the conditioned surface by means of SEM. The material per se did not significantly influence adhesion (p = 0.744). Conditioning protocol was a significant factor: EP yielded significantly higher μSBS than HF (p = 0.005), while no significant differences emerged between EP and HF + S (p = 0.107), or HF + S and HF (p = 0.387). The material-conditioning protocol interaction was not statistically significant (p = 0.109). Significant intergroup differences were found in distribution of failure modes: mixed failures were predominant in the ZLS/EP group, while the other groups showed a prevalence of adhesive failures. The self-etching primer showed promising results in terms of immediate bond strength of a self-adhesive resin cement to lithium-silica-based glass ceramics, suggesting its alternative use to hydrofluoric acid and silane conditioning protocols.

Effect of lithium disilicate ceramic thickness, shade and translucency on transmitted irradiance and knoop microhardness of a light cured luting resin cement

This in vitro study evaluates the influence of pressed lithium disilicate thickness, shade and translucency on the transmitted irradiance and the Knoop microhardness (KHN) of a light-cured resin cement at two depths. One hundred and thirty-five ceramic discs of IPS e.max Press (Ivoclar Vivadent) were fabricated and divided into twenty-seven groups (n = 5) according to the association between translucency: HT (hight translucency), LT (low translucency), and MO (medium opacity); shade: BL2, A1 and A3.5; and thickness: 0.5 mm, 1.5 mm, and 2.0 mm. One side of each ceramic disc was finished, polished and glazed. The irradiance (mW/cm²) of a multiwave LED light curing unit (Valo, Ultradent) was evaluated with a potentiometer (Ophir 10ª-V2-SH, Ophir Optronics) without (control group) or with interposition of ceramic samples. The microhardness of Variolink Esthetic LC resin cement (Ivoclar Vivadent) was evaluated after 24 h at two depths (100 μm and 700 μm). Data were submitted to ANOVA followed by Tukey's test (α = 0.05). Irradiance and KHN were significantly influenced by ceramic thickness (p < 0.0001), shade (p < 0.001), translucency (p < 0.0001) and depth (p < 0.0001). Conclusions: the interposition of increasing ceramic thicknesses significantly reduced the irradiance and microhardness of resin cement. Increased depth in the resin cement showed significantly reduced microhardness for all studied groups. Increased ceramic opacity reduced the KHN of the resin cement at both depths for all ceramic thicknesses and shades.

Effect of Die Spacer Thickness on the Microshear Bond Strength of CAD/CAM Lithium Disilicate Veneers

Aim

The aim of this study was to compare the microshear bond strength of ceramic veneers with digital die spacer settings at 20, 40, and 100 µm.

Materials and Methods

Eighteen milled lithium disilicate microdiscs (IPS e.max CAD, Ivoclar Vivadent) were divided into three groups (n = 6) according to their digital die spacer settings: group A = 20 µm, group B = 40 µm, and group C = 100 µm. Six randomly selected sound maxillary premolars received three microdiscs each. Each microdisc was 1 mm in diameter and 1 mm in height. The buccal surfaces of the premolars were prepared with a 0.5 mm depth in enamel. After cementation, the specimens were thermocycled for 2,500 cycles between 5 and 55°C. Microshear bond strength testing was performed using a universal testing machine until bonding failure. Failure modes were evaluated using a stereomicroscope. Statistical analyses included one-way ANOVA, Tukey's post hoc test, and chi-square test with a 5% alpha error and 80% study power.

Results

The mean microshear bond strength values were calculated in MPa for group A = 31.91 ± 12.41, group B = 29.58 ± 5.03, and group C = 13.85 ± 4.12. One-way ANOVA (p ≤ 0.05) showed a statistically significant difference in microshear bond strength among the three groups. Tukey's post hoc test showed significant differences between groups A and C (p=0.004) and between groups B and C (p=0.011). The failure modes were presented as cohesive, adhesive, and mixed failures. Chi-square test indicated that the failure mode distribution was not significantly different among the three groups (p=0.970).

Conclusion

Higher digital die spacer settings decrease the microshear bond strength of CAD/CAM lithium disilicate veneers.

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.

Two-Year Follow-Up of Self-Etching Ceramic Primer as Surface Treatment for Feldspathic Veneers: A Clinical Case Review

The two-step approach of applying hydrofluoric acid followed by silane is deemed the goldstandard surface treatment protocol before bonding to glass ceramics. Given hydrofluoric acid is a toxic conditioning agent and with the intention to simplify this step, the dental company Ivoclar Vivadent (Schaan, Lietchtenstein) released a self-etching ceramic primer, Monobond Etch & Prime in 2015, claiming that hydrofluoric acid and silane application would no longer be required prior to luting glass ceramics. Therefore, this clinical case report and retrospective analysis describes the replacement of unsatisfactory anterior veneers due to clinical failures for new feldspathic glass ceramic veneers, using the aforementioned self-etching ceramic primer. After two years, feldspathic glass ceramics presented satisfying clinical performance with absence of debonding, tooth sensitivity, recurrent carious lesions, or marginal infiltration.

Surface treatments on CAD/CAM glass-ceramics: Influence on roughness, topography, and bond strength

OBJECTIVE

To evaluate the influence of surface treatment on roughness (SA), topography, and shear bond strength (SBS) of computer-aided designer and manufacture (CAD/CAM) zirconia-reinforced lithium silicate (ZLS) and feldspathic (FEL) glass-ceramics.

MATERIALS AND METHODS

FEL and ZLS specimens were submitted to 5% or 10% hydrofluoric acid (HF) or self-etching ceramic primer (MEP) and different application times (20, 40, and 60 s), or to sandblasting (Control, 20 s). Resin cement cylinders were bonded to the specimens and tested in shear (n = 10) after 24 h and 16-months of water storage. SA and topography were evaluated by atomic force (AFM, n = 10) and scanning electron microscopy. Data were analyzed by ANOVA and Bonferroni test (α = 0.05).

RESULTS

Sandblasting promoted the highest SA for ZLS, but 10% HF (40, 60 s) promoted higher SBS at 16 months. 10% HF produced the highest SA for FEL, but sandblasting and 5% HF (20 s) maintained SBS after 16 months, without differences from 10% HF (20 s) (p > 0.05). Overall, MEP produced lower SA and SBS among groups (p < 0.05). HF displayed greater morphological changes on FEL.

CONCLUSION

10% HF (40 s) provided better results for ZLS, while 5% or 10% HF (20 s) was suitable for FEL.

CLINICAL SIGNIFICANCE

Surface treatments influenced SA, topography, and SBS of materials. HF etching is the surface treatment of choice for both CAD/CAM glass-ceramics.

Effect of prolonged application of single-step self-etching primer and hydrofluoric acid on the surface roughness and shear bond strength of CAD/CAM materials

This in vitro study aimed to assess the influence of different concentrations and durations of hydrofluoric acid (HF) and Monobond Etch & Prime (MEP) etching on the surface roughness (R_a ) of different CAD/CAM materials and on the shear bond strength (SBS) of a self-adhesive resin bonded to the materials. Seventy specimens of hybrid ceramic, leucite-based glass-ceramic, lithium disilicate glass-ceramic, and zirconia-reinforced lithium silicate glass-ceramic were prepared and divided into seven groups according to the surface treatments: Control (C); MEP etching for 60 (MEP₆₀ ) and 120 (MEP₁₂₀ ) s; 5% HF etching for 60 (HF-5%₆₀ ) and 120 (HF-5%₁₂₀ ) s; 9.5% HF etching for 60 (HF-9.5%₆₀ ) and 120 (HF-9.5%₁₂₀ ) s. The R_a was measured using a 3D profilometer. All groups were treated with a universal primer except for the C, MEP₆₀ , and MEP₁₂₀ groups. A self-adhesive resin cement was bonded to all specimens, and the bond strengths were measured using a universal testing machine. All surface treatments increased both R_a and SBS values compared to the control in each material. Neither the duration of surface treatments nor the HF acid concentrations had a statistically significant effect on SBS. Within the limitations of this experimental study, it can be concluded that Monobond Etch & Prime may be a preferable method to achieve high bond strength values.

Glass-ceramic resin-bonded fixed partial dentures for replacing a single premolar tooth: A prospective investigation with a 4-year follow-up

STATEMENT OF PROBLEM

Resin-bonded fixed partial dentures (RBFPDs) are a reliable treatment option for the replacement of a single missing tooth. Glass-ceramic may be a promising material for the fabrication of RBFPDs, but clinical verification has been lacking.

PURPOSE

The purpose of this prospective clinical study was to evaluate the outcomes of glass-ceramic RBFPDs on participants with a single missing premolar.

MATERIAL AND METHODS

Twenty participants (6 men, 14 women; age range: 20 to 54 years) were treated with 2-retainer RBFPDs. These RBFPDs were made of lithium disilicate glass-ceramic (IPS e.max Press; Ivoclar Vivadent AG) and designed with improved C-shaped retention. These prostheses were evaluated at 6 months, 12 months, and annually thereafter and were classified as survival or failure. Analysis was performed with the Kaplan-Meier analysis (95% confidence interval). Modified United States Public Health Service (USPHS) criteria were used to rate the clinical performance. Parameters assessed were fracture, marginal integrity, marginal discoloration, color of restoration, secondary caries, and abutment mobility.

RESULTS

Twenty RBFPDs were provided, 9 in the maxilla and 11 in the mandible. The mean observation time was 49.2 months (minimum 9 months, maximum 53 months). Nineteen RBFPDs were evaluated as having survived during the observation period with some acceptable marginal discoloration, 1 RBFPD had to be replaced because of fracture and secondary caries and was evaluated as a failure. The Kaplan-Meier analysis revealed a survival rate of 95% after a 4-year observation.

CONCLUSIONS

The glass-ceramic RBFPDs in this study displayed a good survival rate and clinical performance, indicating that glass-ceramic RBFPDs might be a promising approach for the short-term replacement of a single premolar. However, further investigations are needed to determine the long-term outcome.

Bond strength of lithium disilicate after cleaning methods of the remaining hydrofluoric acid

Background

Different ceramic surface cleaning methods have been suggested after the acid conditioning. The aim was to evaluate the effect of different protocols used to remove the remaining hydrofluoric acid on the shear bond strength (SBS) between lithium disilicate and resin cement.

Material and Methods

Forty-four specimens of lithium disilicate (IPS e.max Press) were divided in 4 groups (n=11): group C (control, no treatment); group HF+S (5% hydrofluoric acid + silane); group HF+US+S (5% hydrofluoric acid + ultrasound cleaning + silane); group HF+PH+S (5% hydrofluoric acid + 37% phosphoric acid + silane). Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were performed to characterize the surface morphology. The SBS test was performed on the resin/ceramic interface, and the failure mode was characterized. SBS values were submitted to 1-way ANOVA and the Tukey test (α=.05). The relation between surface treatment and failure modes was analyzed using the chi-squared test (α=.05).

Results

The surface treatment type interfered in the shear strength (p<.001) and higher SBS values were observed for the groups HF+US+S (17.87 MPa) and HF+PH+S (16.37 MPa). The surface treatment did not influence the failure mode (p=.713). No fluorsilicate salts were observed after ultrasound cleaning.

Conclusions

The utilization of ultrasound cleaning was an effective procedure to remove remaining fluorsilicate salts, promoting the highest SBS values.

Key words:Bond strength, ceramics, fluorsilicate, lithium disilicate, resin cement.

Effect of experimental resin cements containing thio-urethane oligomers on the durability of ceramic-composite bonded interfaces

Thio-urethane oligomers improve conversion and mechanical properties of resin cements. The objective of this study was to evaluate the effect of resin cements formulated with thio-urethane (TU) oligomers on microtensile bond strength (µTBS) of ceramics to composites subjected to thermal/mechanical cycling. Methods: BisGMA/UDMA/TEGDMA (50/30/20 wt%) containg 0 (control, EC) or 20 wt% aliphatic or aromatic thiourethane (HDDI and BDI, respectively) were mixed with CQ/amine (0.2/0.8 wt%) and 25 wt% 0.7um Ba glass. Rely X Ultimate (RU-3M ESPE) was used as the commercial control. The cements were sandwiched between ceramic (IPS e.max Press) and resin composite blocks (Filtek Supreme, 3 M-ESPE). Eight bonded blocks were produced per experimental group. Prior to bonding, ceramic surfaces were etched (20 s - 10% HF) and silanized. Composite surfaces were treated with Single Bond Universal (3 M ESPE). Specimens were stored for 24 h in distilled water at 37 °C, and then either tested immediately, or subjected to thermal (10,000, 5 °C and 55 °C) or mechanical cycling (300,000 cycles). Sticks (1 mm², average of 25 sticks per block) were cut and tested for µTBS (1.0 mm/min). Data were analyzed with two-way ANOVA/Tukey's test (α = 5%). Fracture surfaces were analyzed to determine failure modes. Results: The µTBS for HDDI and RU was significantly higher than BDI and EC cements. BDI led to significantly higher µTBS than EC after 24 h, Tc and Mf. µTBS decreased significantly after thermal/mechanical cycling for all groups. Failure modes were predominantly adhesive or mixed. Significance: The use of selected thio-urethane oligomers was able to increase the µTBS of composite-cement-ceramic specimens. Tc and Mf reduced µTBS for all resins cements.

Effect of Hydrofluoric Acid Concentration and Thermal Cycling on the Bond Strength of Brackets to Ceramic

This study to evaluate the effects of different hydrofluoric acid (HF) concentrations and thermal cycling on the shear bond strength (SBS) of brackets to ceramic. Cylinders of ceramic were divided into 10 groups (n=15), according to HF concentrations: 1-1%;2-2.5%;3-5%;4-7.5%;5-10% (storage 24 h); 6-1%;7-2.5%;8-5%;9-7.5%; and, 10-10% (thermal cycling). All cylinders were etched for 60s and received one layer of silane. Metallic brackets were bonded to the cylinders using Transbond-XT, light activated for 40 s, using a LED (Radii Plus) and stored in deionized water at 37o C for 24h. The groups 6 to 10 were submitted to thermal cycling (7,000 cycles - 5o/55oC). SBS was performed in an Instron at crosshead speed of 1.0 mm/min. Data were submitted to two-way ANOVA and Tukey's post-hoc test (α=0.05). The Adhesive Remaining Index (ARI) was evaluated at 40x magnification. The different HF acid concentrations influenced on the SBS of the brackets to ceramic (p<0.05). The thermal cycling decreased the SBS of the brackets to ceramic for all acid concentrations (p<0.05). The ARI showed a predominance of scores 0 for all groups, with an increase in scores 1, 2 and 3 for the group storage for 24 h. In conclusion, the different HF acid concentrations 5.0%, 7.5% and 10% influenced on the SBS of brackets to ceramic. The thermal cycling decreased significantly the SBS of brackets to ceramic.

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.

Interaction of a universal adhesive with different surface treatments with feldespathic ceramics

Introduction

Universal adhesives provide the possibility of simplified protocols for using ceramics; however, determining the synergy of these adhesives with silanes and the possibility of replacing silanes requires extensive research.

Objective

To evaluate the influence of a universal adhesive, associated with airborne-particle abrasion, acid etching, and silane, on the bond strength of a feldspathic ceramic CAD-CAM to composite resin.

Materials and methods

CAD-CAM feldspathic ceramic blocks were cut into 2-mm slices and were randomly divided into six groups (n = 10): A1, Single Bond Universal (SBU); A2, Adper Single Bond 2 (SB2); B1, silane + SBU; B2, silane + SB2; C1, acid etching + silane + SBU; C2, and acid etching + silane + SB2. Tygon tubes were placed and filled with composite resin. All samples were stored in distilled water at 37 °C for 24 h and then subjected to micro-shear tests. The type of failure was analyzed using a stereomicroscope.

Results

SBU demonstrated slightly higher adhesion values compared with SB2 in all groups; however, no significant differences were observed between the adhesives (p < 0.05).

Conclusion

SBU was not statistically superior to the control adhesive. The use of silane prior to a universal adhesive should not yet be eliminated.

Effect of Different Neutralizing Agents on Feldspathic Porcelain Etched by Hydrofluoric Acid

Objective The aim of this study was to evaluate the effect of neutralizing agents on the shear bond strength of hydrofluoric (HF)–etched porcelain in nonaging and aging conditions.

Subjects and Methods One hundred and twenty feldspathic porcelain specimens were prepared and divided into six groups to undergo different surface conditioning methods—group 1: control; group 2: HF; group 3: HF + calcium hydroxide; group 4: HF + calcium carbonate; group 5: HF + calcium gluconate; and group 6: HF + ultrasonic. All samples were immersed in 37°C distilled water for 24 h. Half of the samples were thermocycled in water for 5,000 cycles. The shear bond strength test was performed using a universal testing machine at a crosshead speed of 0.5 mm/min. Data were statistically analyzed by two-way ANOVA and Tukey's multiple comparison test at a 95% confidence level. The surface micromorphology and surface elements were analyzed using scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX), respectively.

Results The shear bond strengths of groups 2–6 were significantly higher than the control group in both aging and nonaging conditions ( p < 0.05). There were no significant differences among all of the HF-etched porcelain groups ( p > 0.05). SEM images of groups 2–6 illustrated similar patterns of irregularity on the specimen surfaces. Elemental analysis of EDX demonstrated identical elements on surfaces of specimens of groups 2–6.

Conclusion Within the limitations of this study, shear bond strength values between HF-etched porcelain, HF-etching followed by application of neutralizing agents, and HF-etching followed by ultrasonic cleaning were not significantly different in both nonaging and aging conditions.

Effect of hydrofluoric acid concentration and etching time on resin-bond strength to different glass ceramics

The objective of this study was to evaluate the effect of the hydrofluoridric acid (HF) concentration and time of acid conditioning on bond strength of three glass ceramics to a resin cement. Thus, fifty blocks (10 mm x 5 mm x 2 mm) of each ceramic (LDCAD: IPS e.max CAD; LCAD: IPS Empress CAD and LDHP: IPS e.max Press) were made and embedded in acrylic resin. The surfaces were polished with sandpaper (#600, 800, 1000, and 1200 grits) and blocks were randomly divided into 15 groups (n = 10) according to the following factors: Concentration of HF (10% and 5%), conditioning time (20 s and 60 s) and ceramic (LDCAD, LDHP, and L). After conditioning, silane (Prosil / FGM) was applied and after 2 min, cylinders (Ø = 2 mm; h = 2 mm) of dual resin cement (AllCem / FGM) were made in the center of each block using a Teflon strip as matrix and light cured for 40 s (1,200 mW/cm2). Then, the samples were thermocycled (10,000 cycles, 5/55°C, 30s) and submitted to the shear bond test (50 KgF, 0.5 mm/min). The data (MPa) were analyzed with 3-way ANOVA and Tukey's test (5%). Failure analysis was performed using a stereomicroscope (20x) and a scanning electron microscope (SEM). ANOVA revealed that the "concentration" factor (p = 0.01) and the interaction "acid concentration X ceramic" (p = 0.009) had a significant effect, however, the "ceramic" (p = 0.897) and "conditioning time" (p = 0.260) factors did not influence the results. The LDHP10%60s (10.98 MPa)aA* group presented significantly higher bond strength than LDHP10%20s (6.57 MPa)bA, LCAD5%20s (6,90 ±3,5)aB and LDHP5%60s (5.66 ± 2,9MPa)aA* groups (Tukey). Failure analysis revealed that 100% of specimens had mixed failure. In conclusion, etching with 5% HF for 20 seconds is recommended for lithium disilicate and leucite-reinforced CAD/CAM ceramics. However, for pressed lithium disilicate ceramic, 10% HF for 60 s showed significantly higher bond strength to resin cement.

Bonding effectiveness of tooth-colored materials to resin cement provided by self-etching silane primer after short- and long-term storage

STATEMENT OF PROBLEM

Glass-ceramic materials are typically treated with hydrofluoric acid (HF) and silane to improve their bond to composite resin; however, HF may be harmful to human tissues and the integrity of the material, and its application is a technique-sensitive procedure. A novel self-etching ceramic primer has been introduced with the claim that it can solve those problems. However, independent scientific evidence regarding its performance is scarce.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of self-etching silane primer on glass-ceramic surface roughness and on long-term bonding between glass-ceramic and composite resin cement.

MATERIAL AND METHODS

Plates of 3 materials (n=10), lithium disilicate glass-ceramic (LDC) (IPS e.max CAD), leucite-based glass-ceramic (LEU) (IPS Empress CAD), and resin-modified ceramic (PIC) (VITA ENAMIC), were treated in the following ways: no treatment (C), HF (5%) applied during the recommended time for each material (HF), and self-etching ceramic primer (Monobond Etch & Prime [MBEP]). Surface roughness (Sa) was analyzed with a laser 3D profiler. Ceramic sticks were subjected to (n=20) no treatment (C); treatment with hydrofluoric acid plus silane (HF+S); and treatment with self-etching ceramic primer (MBEP) bonded to prepolymerized composite resin sticks with composite resin cement (Variolink II) and stored for 24 hours and 1 year (n=10). The assemblies were submitted to microtensile bond strength testing (μTBS). Data were analyzed using ANOVA and the Tukey pairwise, post hoc test (α=.05). Failure pattern and surface and interface morphology were assessed using scanning electron microscopy.

RESULTS

Only individual factors resulted in statistically significant differences for both variables (material: P<.001; surface treatment: P=.020), interaction (P=.570). HF group (0.49 ±0.11 μm) showed statistically higher roughness values (P≤.05) than control groups (0.44 ±0.97 μm), while MBEP (0.48 ±0.11 μm) was comparable with both. HF produced greater surface alterations than MBEP and C. PIC (0.60 ±0.051 μm) exhibited significantly higher roughness values (P≤.05) than LDC (0.37 ±0.07 μm) and LEU (0.45 ±0.04). Regarding μTBS, the general mean of PIC (24.6 ±10.1 MPa) was higher (P≤.05) than LEUs (14.7 ±6.7 MPa) and LDCs (13.1 ±4.8 MPa), while treatment groups HF+S (17.9 ±10.0 MPa) and MBEP (20.5 ±9.7 MPa) produced higher μTBS values than control groups (14.2 ±5.5 MPa). Adhesive failure was associated with low μTBS values and aged specimens, while cohesive failure within the composite resin-cement layer and mixed failures were associated with higher μTBS values. Interface debonding was detected in C groups for LDC and LEU. PIC exhibited better interface stability.

CONCLUSIONS

MBEP produced smoother surfaces than HF. HF+S and MBEP significantly improved ceramic and composite resin cement bonding.

Influence of hydrofluoric acid etching time and concentration on shear bond strength of metal brackets to ceramic surfaces

Abstract Introduction Surface treatment prior to bonding ceramic brackets with hydrofluoric acid is indicated because of its ability to promote morphological changes necessary for adhesion. Objective To evaluate the shear bond strength (RUC) of metal brackets bonded to the feldspar ceramic surface under the action of hydrofluoric acid (AF), in different concentrations (5% and 10%) and different application times (30 and 60 seconds). Material and method Four nickel-chrome metal blocks that received an application of feldspathic ceramic were used, to which 80 metal brackets (Abzil/3M) were bonded and divided into 4 Groups (n=20) according to the acid etching procedure. The blocks were etched with 5% hydrofluoric acid for 30 and 60 seconds (AF5/30 and AF5/60, respectively) and 10% hydrofluoric acid for 30 and 60 seconds (AF10/30, AF10/60, respectively). The resin composite used was Transbond XT (3M) and the presence of a glazer was maintained on the ceramic surface. The specimens were placed on a Universal test machine Instron 4411 (Instron Corp, USA) to which a chisel was adapted to perform the shear test at a speed of 1mm/min. The data were submitted to the analysis of variance (ANOVA) and the Adhesive Remnant Index was evaluated. Result In the time interval of 30 seconds, there was no significant difference for the 5% and 10% hydrofluoric acid concentrations. In the 60-second time interval, the 10% concentration showed significantly higher shear bond strength values (p<0.05). The ARI showed predominance of scores 1 and 2. Conclusion It was concluded that 10% hydrofluoric acid showed higher shear bond strength values in 60 seconds of etching, while 5% hydrofluoric acid showed no significant difference between the etching times.

Adhesion to a Lithium Disilicate Glass Ceramic Etched with Hydrofluoric Acid at Distinct Concentrations

This study evaluated the effect of different hydrofluoric acid (HF) concentrations on the bond strength between a lithium disilicate-based glass ceramic and a resin cement. Eighty ceramic-blocks (12×7×2 mm) of IPS e.Max CAD (Ivoclar Vivadent) were produced and randomly assigned to 8 groups, considering 2 study factors: HF concentration in 4 levels, i.e., 1% (HF1), 3% (HF3), 5% (HF5), and 10% (HF10), and storage in 2 levels, i.e., baseline (tests were performed 24 h after cementation), and aged (storage for 150 days + 12,000 thermal-cycles at 5°C and 55°C). Acid etching (20 s) was performed, followed by washing, drying, and silanization. Four resin cement cylinders (ϕ= 0.96 mm) were built-up from starch matrices on each ceramic sample (n= 40). Additional ceramic samples were etched and analyzed for contact angle, micro-morphology, and roughness. In baseline condition (without aging), the HF3, HF5, and HF10 groups showed similar bond strength values (13.9 - 15.9 MPa), and HF1 (11.2 MPa) presented lower values than HF5, being that statistically different (p= 0.012). After aging, all the mean bond strengths statistically decreased, being that HF3, HF5, and HF10 (7.8 - 11 MPa) were similar and higher than HF1 (1.8 MPa) (p= 0.0001). For contact angle, HF3, HF5, and HF10 presented similar values (7.8 - 10.4°), lower than HF1 and CTRL groups. HF5 and HF10 presented rougher surfaces than other conditions. For better bond strength results, the tested ceramic may be etched by HF acid in concentrations of 3%, 5%, and 10%.

Effect of Surface Coating on Bond Strength between Etched Feldspar Ceramic and Resin-Based Luting Agents

This study evaluated adhesive protocols (silane, silane and unfilled resin, and universal adhesive) of bond strength between feldspar ceramic and resin-based luting agents (RBLAs). Thirty ceramic disks were embedded into acrylic resin, polished, etched, and randomly divided into 6 groups: S-RC: silane (S) and light-cured resin cement (RC) (RelyX Veneer; 3M ESPE); SB-RC: S followed by bond (B) (Clearfil SE Bond, Kuraray) and RC; UA-RC: universal adhesive (UA) (Single Bond Universal; 3M ESPE) and RC; flowable composite resin (F) was used on groups S-F, SB-F, and UA-F, and luting agent cylinders were built. The response variables (n=20) were microshear bond strength (MPa), characteristic strength (σ₀, MPa), and Weibull modulus (m). The RC groups presented similar bond strengths regardless of whether or not bond was used. The S-F group with only silane application showed the highest bond strength, while the universal adhesive showed the lowest bond strength. The reliability was only affected in the UA-RC group, which was lower than the S-F group. Silane application is fundamental since the universal adhesive only decreased the bond strength between the feldspar ceramic and the RBLAs. Overall, the use of unfilled resin did not positively influence bond strength.

Fracture Resistance of Ceramic Laminate Veneers Bonded to Teeth with Class V Composite Fillings after Cyclic Loading

Purpose

Porcelain laminate veneers (PLVs) are sometimes required to be used for teeth with composite fillings. This study examined the fracture strength of PLVs bonded to the teeth restored with different sizes of class V composite fillings.

Materials and Methods

Thirty-six maxillary central incisors were divided into three groups (n=12): intact teeth (control) and teeth with class V composite fillings of one-third or two-thirds of the crown height (small or large group, resp.). PLVs were made by using IPS e.max and bonded with a resin cement (RelyX Unicem). Fracture resistance (N) was measured after cyclic loading (1 × 10⁶ cycles, 1.2 Hz). For statistical analyses, one-way ANOVA and Tukey test were used (α=0.05).

Results

There was a significant difference between the mean failure loads of the test groups (P=0.004), with the Tukey-HSD test showing lower failure loads in the large-composite group compared to the control (P=0.02) or small group (P=0.05). The control and small-composite groups achieved comparable results (P > 0.05).

Conclusions

Failure loads of PLVs bonded to intact teeth and to teeth with small class V composite fillings were not significantly different. However, extensive composite fillings could compromise the bonding of PLVs.

The effect of hydrofluoric acid and resin cement formulation on the bond strength to lithium disilicate ceramic

To investigate how the hydrofluoric acid (HF) concentrations applied to a lithium disilicate glass-ceramic (EMX) affects the surface morphology and microtensile bond strength (μTBS) of ceramics to dentin, using light-cured resin cements with or without UDMA. Sixty-three EMX square ceramic blocks were etched for 20 seconds using different HF concentrations (1%, 5% and 10%) and luted to dentin using two types of resin cement combinations: BisGMA/TEGDMA and BisGMA/TEGDMA/UDMA (n = 10). Each bonded EMX-dentin block was sectioned to obtain 1 mm2 sticks for μTBS evaluation. Half of the sticks were tested after 24 hours and the other half was assessed after 6 months of water storage. Data were statistically assessed using split-plot three-way ANOVA and multiple comparisons were performed using the Tukey's post hoc test (α = 0.05). One EMX sample from each HF concentration was analyzed using field-emission scanning electron microscope (FE-SEM) to characterize the etching pattern. According to the FE-SEM images, increasing the concentration of HF from 1 to 5 and then to 10% led to increased removal of glassy matrix and greater exposure of lithium disilicate crystals. The 10% HF concentration yielded higher μTBS when compared to 1% for BisGMA/TEGDMA formulation (p < 0.05); whereas HF 1% and 5% showed similar μTBS values when compared to 10% HF for BisGMA/TEGDMA/UDMA resin matrix (p > 0.05) at both storage times. Water aging decreased the μTBS values (p < 0.05), except when 10% HF was associated with BisGMA/TEGDMA resin cement. Resin cement formulation and hydrofluoric acid concentrations can interfere with the immediate and long-term glass-ceramic bond strength to dentin.