The effects of water on degradation of the zirconia-resin bond

The effect of combining primers and cements from different cement systems on the bond strength between zirconia and dentin

OBJECTIVE

The aim of this study was to evaluate the influence of combining primers and cements from two different resin cement systems on the microtensile bond strength (μTBS) between zirconia and human dentin.

MATERIALS AND METHODS

A total of 120 specimens of zirconia cemented to dentin were allocated into eight groups based on cement type (RelyX Ultimate or Panavia V5) and primers (Tooth Primer, Clearfil Ceramic Primer and Scotchbond Universal Adhesive) combinations, applied to dentin or ceramic surfaces. Following artificial aging with 5000 thermocycles, μTBS tests were conducted. Statistical analysis was performed using One-way ANOVA and Tukey's post hoc tests (p ≤ 0.05), and failure modes were assessed.

RESULTS

The Panavia V5 cement system demonstrated the highest bond strength (19.4 ± 4.4 MPa), significantly higher than the other groups except when RelyX cement was used with Panavia primers (16.9 ± 3.7 MPa). Cohesive fractures within the cement layer were the predominant failure mode.

CONCLUSIONS

The combination of primers from different adhesive cement system brands may significantly affect the bonding effectiveness. Therefore, using products from a single product line of the same adhesive cement system, and following the manufacturer's recommendations for indications and use, is crucial for a more predictable clinical outcome.

Bond Strength of Milled and Printed Zirconia to 10-Methacryloyloxydecyl Dihydrogen Phosphate (10-MDP) Resin Cement as a Function of Ceramic Conditioning, Disinfection and Ageing

This study aimed to assess the suitability of printed zirconia (ZrO2) for adhesive cementation compared to milled ZrO2. Surface conditioning protocols and disinfection effects on bond strength were also investigated. ZrO2 discs (n = 14/group) underwent either alumina (Al2O3) airborne particle abrasion (APA; 50 µm, 0.10 MPa) or tribochemical silicatisation (TSC; 110 µm Al2O3, 0.28 MPa and 110 µm silica-modified Al2O3, 0.28 MPa), followed by disinfection (1 min immersion in 70% isopropanol, 15 s water spray, 10 s drying with oil-free air) for half of the discs. A resin cement containing 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) was used for bonding (for TSC specimens after application of a primer containing silane and 10-MDP). Tensile bond strength was measured after storage for 24 h at 100% relative humidity or after 30 days in water, including 7500 thermocycles. Surface conditioning significantly affected bond strength, with higher values for TSC specimens. Ageing and the interaction of conditioning, disinfection and ageing also impacted bond strength. Disinfection combined with APA mitigated ageing-related bond strength decrease but exacerbated it for TSC specimens. Despite these effects, high bond strengths were maintained even after disinfection and ageing. Adhesive cementation of printed ZrO2 restorations exhibited comparable bond strengths to milled ZrO2, highlighting its feasibility in clinical applications.

Shear bond strength of adhesive cement to zirconia: Effect of added proportion of yttria for stabilization

STATEMENT OF PROBLEM

Zirconium dioxide (zirconia) cannot be etched in a clinical setting, but zirconia restorations with minimal to no micromechanical bonding are approved and widely used in contemporary dentistry. However, information on the shear bond strength of zirconia and adhesive cement, on the effect of an added proportion of yttria, and on the effect of aging is lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the shear bond strength of cement luted to zirconia and the effect of aging.

MATERIAL AND METHODS

A total of 131 test specimens were made from 4 zirconia materials with different amounts of yttria added to formulate yttria-partially stabilized zirconia (Y-PSZ); 3Y-PSZ (n=32), 4Y-PSZ (n=34), and 2 5Y-PSZs (n=32 and n=33). A dual-polymerizing cement and 10-methacryloyloxydecyl dihydrogen phosphate-containing primer were used. All specimens were stored in water at 37 °C, half of them for 24 hours and the other half for 6 months. After aging, the specimens were subjected to a shear bond strength test with a notched crosshead according to the International Organization for Standardization (ISO) 29022:2013 standard. The data were analyzed using the independent 2-sample t test, ANOVA, and the Levene test (α=.05).

RESULTS

The 3Y-PSZ material had higher mean ±standard deviation shear bond strength (31.83 ±12.80 MPa) compared with 4Y-PSZ (23.34 ±7.66 MPa) after 24 hours of aging in water and higher (28.98 ±14.03 MPa) than 4Y-PSZ (14.35 ±9.62 MPa) and one of the 5Y-PSZ (16.05 ±11.34 MPa) after 6 months. Debonding before loading occurred in all groups except for one of the 5Y-PSZ groups.

CONCLUSIONS

Zirconia without macromechanical retention, regardless of an added proportion of yttria, showed high shear bond strength, but the tested materials also had a high coefficient of variance, which, in practice, leads to the risk of the occasional debonding of zirconia restorations.

Zirconia bond strength durability following artificial aging: A systematic review and meta-analysis of in vitro studies

The present study systematically reviewed the literature regarding the bond strength durability of zirconia ceramics to resin-based luting cements after application of different bonding protocols and aging conditions. Electronic searches in PubMed, Scopus, and Web of Science databases were performed for relevant literature published between January 1st 2015 and November 15th 2022. Ninety-three (93) English language in-vitro studies were included. The percentage of the mean bond strength change was recorded prior to and after artificial aging, and the weighted mean values and 95% confidence intervals were calculated. Bonding protocols were classified based on the combination of MDP/non-MDP containing cement/primer and surface pretreatment, as well as the level of artificial aging performed. Alumina sandblasting (SA) was identified as the most frequently used surface pre-treatment while an insufficient number of studies was identified for each category of alternative surface treatments. The combination of MDP cement with tribochemical silica coating (TSC) or SA yielded more durable results after aging, while the application of SA and TSC improved bond durability when a non-MDP cement and a non-MDP primer were used. TSC may lead to increased bond durability compared to SA, whereas MDP cements may act similarly when combined with SA or TSC.

Effect of surface topography and wettability on shear bond strength of Y-TZP ceramic

Zirconia ceramics have been widely used as dental restorations due to their esthetic appearance and high flexural strength. The bonding of zirconia with resin cement should rely on both mechanical and chemical bonds. This study was performed to investigate the effect of zirconia surface topography and its wettability after surface pretreatments on the microshear bond strength (μSBS) of a resin cement. Zirconia slabs were prepared and randomly divided into 5 groups based on the surface treatment as follows: no treatment (control), air abrasion (AB), etching with hydrofluoric acid (F), the mixture of hydrofluoric acid and nitric acid (FN), or the mixture of hydrochloric acid and nitric acid (CN) for 10 min. The specimens were subjected to investigation of surface roughness characteristics [average roughness (Ra), peak-to-valley average distance (Rpv), skewness (Rsk), and kurtosis (Rku)] using atomic force microscopy (AFM) and measurements of surface contact angle (θc) and μSBS of a resin cement. In addition, the area % of the nanoscale surface irregularity (nSI%) was calculated from the AFM images. The effects of nSI%, Ra and θc on the μSBS were analyzed by multiple linear regression analysis (p < 0.05). Multiple regression analysis revealed that the nSI% was the most predominant factor for the μSBS (p < 0.001). A surface with larger nSI%, higher Ra and relatively lower θc was essential for establishing a reliable resin-zirconia bond.

Wear behaviour of lithography ceramic manufactured dental zirconia

OBJECTIVE

The study aims to evaluate the wear surface using 3D surface roughness and other material characterization of zirconia fabricated using photopolymerization based Lithography-based Ceramic Manufacturing (LCM).

METHOD

LCM technology was used to fabricate zirconia specimens of size 10 × 10 × 2mm³. Scanning Electron Microscope, 3D-profilometer, X-ray Diffraction, and hardness test characterized the samples before and after wear and Coefficient of friction (COF) was monitored.

RESULT

The COF was around 0.7 and did not differ much between the horizontally and vertically printed specimens. However, the surface roughness after wear for horizontally printed specimen was 0.567 ± 0.139 μm, while that for vertically printed specimen was 0.379 ± 0.080 μm. The reduced valley depth and the dale void volume were low for the vertically printed zirconia specimen, indicating lesser voids and low fluid retention. In addition, it was observed that the hardness value of the vertically printed sample was better. The scanning electron microscopic images and 3D surface profiles of the zirconia specimens depicted the surface topography and revealed the wear track.

CONCLUSION

The study shows that zirconia fabricated using LCM technology possesses surface roughness of about 0.5 μm with no machining scars that are usually associated with CAD/CAM dentistry and also indicating agreement with clinically acceptable values for minimal surface roughness of dental restorations. Dental restorations using LCM fabricated zirconia redues the requirement of post-processing work flow that is part of CAD/CAM dentistry.

Y-TZP Physicochemical Properties Conditioned with ZrO2 and SiO2 Nanofilms and Bond Strength to Dual Resin Cement

Commercial Yttria-tetragonal zirconia polycrystalline (Y-TZP) was subjected to surface treatments, and the bond strength of dual resin cement to Y-TZP and failure modes were evaluated. Disks (12 mm × 2 mm), cylinders (7 mm × 3.3 mm), and bars (25 mm × 5 mm × 2 mm) were milled from Y-TZP CAD-CAM blocks, divided into seven groups, and subjected to different surface treatments; silicatization was used as control. On the basis of the literature, this study evaluated modifications with films containing SiO2 nanoparticles and silane; SiO2+ZrO2—SiO2 (50%) and ZrO2 (50%) nanoparticles, SiO2+ZrO2/Silane-SiO2 (50%) and ZrO2 (50%) nanoparticles, and silane. Specimens were analyzed by wettability (n = 3), surface free energy (n = 3), X-ray diffraction (n = 1), Fourier transform infrared spectroscopy (FTIR) (n = 1), roughness (n = 5), shear bond test (n = 10), and dynamic modulus (n = 3). Specimens treated with hydrofluoric acid—HF 40% presented significantly higher contact angle and lowest surface free energy (p < 0.05). The SiO2/Silane presented crystalline SiO2 on the surface. The surface roughness was significantly higher for groups treated with nanofilms (p < 0.05). Shear bond strength was significantly higher for silicatization, HF 40%/silicatization, SiO2/Silane, and SiO2+ZrO2/Silane groups. The proposed treatments with nanofilms had potentially good results without prejudice to the physicochemical characteristics of zirconia. Generally, groups that underwent silica surface deposition and silanization had better bond strength (p < 0.005).

Enhancing Resin Cement Adhesion to Zirconia by Oxygen Plasma-Aided Silicatization

The combinations of alumina particle air abrasion (AA) and a 10-methacryloyloxyidecyl-dihyidrogenphosphate (MDP) primer and a tribochemical silica coating (TSC) and a silane-base primer are contemporary pre-cementation treatments for zirconia restorations for bonding with resin cements. However, the stability of zirconia resists the mechanical or chemical preparations. The purpose of this study was to develop an atmospheric-pressure oxygen plasma (OP)-aided silicatization method to enhance the adhesion of resin cements to zirconia. Zirconia discs were prepared to receive surface treatments of different combinations: (1) AA or TSC (2) with or without OP treatment, and (3) a chemical primer (no primer, silane, or a silane-MDP mixture). The surface morphology, hydrophilicity, and chemical compositions were characterized, and the resin-zirconia bond strengths were examined either after 24 h or a thermocycling test. The results indicated that the OP treatment after the TSC facilitated the homogeneous distribution of silane and crosslinking of silica particles, and effectively improved the hydrophilicity. The OP increased the O and Si and reduced the C elemental contents, while the combination of TSC, OP, and silane induced SiO_x generation. Among the groups, only the TSC-OP-silane treatment effectively enhanced the bond strength and maintained the adhesion after thermocycling. With these results, the OP aided the silicatization protocol effectively, generated silane crosslinking, and resulted in superior resin-zirconia bond strength and durability compared to the current treatments.

Adhesive Cementation of Zirconia Based Ceramics-Surface Modification Methods Literature Review

Introduction: The conditioning procedures for glass-based ceramic restorations before adhesive cementation are generally recognized. In the case of polycrystalline ceramics, which include zirconium oxide, there is still no standardized protocol. The aim of this work was to present conditioning methods of the cementation surface of zirconium oxide fixed dentures. The new generation high translucency zirconia has been also considered. Material and method: The following keywords for the PUBMED and EMBASE databases were used: zirconium oxide, zirconium oxide with increased translucency, bond strength, bending strength, surface treatment. The inclusion criteria were original papers in English published between 2015–2021. Results: Out of 1537 publications, 53 articles were selected for the study, covering methods of conditioning zirconium ceramics, including new materials with increased translucency. These procedures were divided into 5 main groups. Summary: Due to the widespread use of zirconia ceramics and the introduction of new zirconia-based materials, the use of a predictable and standardized cementation protocol is one of the most important factors contributing to the long-term clinical success of prosthetic restorations. Therefore, the research showed differences in the properties of the covered materials after conditioning. It suggests the need to create separate conditioning protocols for highly translucent and traditional zirconia.

Retention strength of monolithic zirconia crowns cemented with different primer-cement systems

BACKGROUND

The purpose of this in vitro study was to assess the influence of different cement systems with different ceramic primers on the retention strength of zirconia crowns.

METHODS

Thirty extracted molars were prepared with flat occlusal surfaces, 20 degrees taper, and 3 mm axial wall height. A zirconia crown with an occlusal bar was fabricated for each tooth. All specimens were divided (n = 10) into; Group M: Multilink Speed/Monobond N, Group P: Panavia V5/Clearfil Ceramic Primer Plus, Group D: Duo-Link universal/Z-Prime Plus. The intaglio surfaces of crowns were air-abraded using 50 µm alumina at 2.5 bar for 10 s. Then each crown was cemented onto its corresponding tooth. All specimens were thermocycled for 10,000 cycles between 5 and 55 °C. Each crown was subjected to gradually increasing vertical load along the path of insertion through hooks engaging the occlusal bar using a universal testing machine until failure. The force at dislodgment was recorded and retention strength was calculated for each specimen. The failure modes were recorded for each specimen. The data were statistically analyzed using one way ANOVA test followed by Tukey HSD test (α = .05).

RESULTS

Group D showed lowest strength (1.42 ± 0.23 MPa) and differed significantly (P < .001) from Group M (2.71 ± 0.45 MPa) and Group P (2.47 ± 0.41 MPa). There was no significant difference (P = .34) between Group M and Group P. The failure modes for Groups M and Group P were mainly cohesive, while Group D showed adhesive failure.

CONCLUSIONS

The retention strength of zirconia crowns was improved with Multilink Speed and Panavia V5 cement systems, while the use of the Duo-Link Universal cement system only showed half of those retention strength values.

Current scenario on adhesion to zirconia; surface pretreatments and resin cements: A systematic review

Several methods have been proposed to increase bonding of zirconia with resin. However, we are still to find the Holy Grail. A systematic literature review was performed through PubMed on international literature from January 2000 to May 2021 with relevant Medical Subject Headings terms. 56 articles were found to be relevant. Of all the different methods proposed, mechanochemical pretreatment of zirconia surface with alumina oxide and use of 10-methacryloyloxydecyl dihydrogen phosphate were found to be most effective as per majority of studies. New methods that require further research also surfaced.

The effects of different silicatization and silanization protocols on the bond durability of resin cements to new high-translucent zirconia

OBJECTIVE

The aim of this study was to assess the influence of different silicatization protocols with various silane treatment methods on the bond performance to high-translucent zirconia.

MATERIALS AND METHODS

High-translucent zirconia specimens were assigned to five groups according to mechanical surface pretreatment: as-sintered (Con), 0.2 MPa alumina sandblasting (AB2), tribochemical silica coating (TSC), 0.2 and 0.4 MPa glass bead air abrasion (GB2) and (GB4). Each group was subjected to 4 different cementation protocols: Panavia SA Universal (SAU), Panavia SA plus (SAP), silane + SAP (S-SAP), and Universal adhesive + SAP (U-SAP). Tensile bond strength (TBS) was measured after 24 h and 10,000 thermocycling (TC). Surface topography, surface energy, and elemental composition of the abraded zirconia surface analyses were completed. TBS data was analyzed using the Weibull analysis method. Surface roughness and surface energy were compared by one-way ANOVA analysis of variance (α = 0.05).

RESULTS

After 24 h, higher TBS was achieved with all cementation protocols in AB2 and TSC, also, in GB2 with all protocols except U-SAP, and in GB4 with SAU and S-SAP. After aging, GB4/S-SAP, GB2/S-SAP, AB2/U-SAP, and TSC/S-SAP showed the highest bond strength. GB groups showed the lowest surface roughness and highest surface energy.

CONCLUSION

Glass bead abrasion achieved the durable bond strength to high-translucent zirconia using a separate silane coupling agent while altered surface chemistry, surface energy, and roughness without effect on morphology.

CLINICAL RELEVANCE

Glass bead air abrasion is an alternative to alumina sandblasting and tribochemical silica coating and improves bond strength to high translucent zirconia.

Adhesion to Zirconia: A Systematic Review of Surface Pretreatments and Resin Cements

This systematic review aims to evaluate the different pretreatments of the zirconia surface and resin cement in order to determine a valid operative protocol for adhesive cementation. Methodologies conducted for this study followed the Prisma (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) guidelines. An electronic search was performed in four databases. The established focus question was: “What type of surface conditioning method is the one that obtains the best adhesion values to zirconia over time by applying a resin cement?” Forty-five relevant papers were found to qualify for final inclusion. In total, 260 different surface pretreatment methods, mainly combinations of air-abrasion protocols and adhesive promoters, were investigated. Altogether, the use of two artificial aging methods, three types of cement and four testing methods was reported. The results showed that mechanicochemical surface pretreatments offered the best adhesive results. Self-adhesive cement and those containing 10-MDP obtained the best results in adhesion to zirconia. Artificial aging reduced adhesion, so storage in water for 30 days or thermocycling for 5000 cycles is recommended. A standardized adhesive protocol has not been established due to a lack of evidence

Influence of different cleaning procedures on the shear bond strength of 10-methacryloyloxydecyl dihydrogen phosphate-containing self-adhesive resin cement to saliva contaminated zirconia

PURPOSE

To evaluate the effect of different cleaning methods on the shear bond strength (SBS) of a 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-containing self-adhesive resin cement to zirconia after saliva contamination.

METHODS

Sixty zirconia specimens were randomly divided into four groups (n=15) according to treatment surface. Except for the control group, all samples were contaminated with saliva and were then rinsed with water-spray and air-dried. Subsequently, the specimens were either treated with a cleaning paste (CP), with argon plasma (AP), or did not undergo an additional cleaning process (WS). An MDP-containing self-adhesive resin cement was applied onto the ceramic surfaces. Specimens were stored in water (24 hours) followed by thermocycling (5°C to 55°C for 10.000 cycles). SBS tests were performed in a universal testing machine, and the results (MPa ± SD) were statistically analyzed using ANOVA and Bonferroni post-hoc test. Fractured surfaces were examined to identify the failure types using a stereomicroscopy and SEM.

RESULTS

The surface cleaning treatment (p < 0.05) significantly affected the results. The highest SBS values were observed in the control group (12.16 ± 1.22 MPa) and were statistically comparable to values for the CP group (11.38 ± 1.65 MPa). The AP group (9.17 ± 1.06 MPa) showed significantly higher bond strength than the WS group (6.95 ± 1.20 MPa), but it showed significantly lower strength than the control and CP groups.

CONCLUSIONS

The CP application was the most effective method in removing saliva contamination. The AP treatment could not restore the SBS to the same level as uncontaminated specimens.

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.

Effect of potassium hydrogen difluoride in zirconia-to-resin bonding

The objective of this study was to compare potassium hydrogen difluoride (KHF₂) etching for zirconia with commonly used surface roughening and chemical bonding methods (silane, MDP-monomer primer) for resin-based luting cement bonding to zirconia. Zirconia specimens were divided into six groups (n=10) according to surface treatment and bonding procedures, with and without thermocycling (6,000 cycles, 5-55ºC): 1) air-borne particle abrasion with alumina+MDP-monomer (ABP), 2) air-borne particle abrasion with silica-coated trialuminium trioxide+silane (ABPR-S) and 3) KHF₂ etching+silane (ETC). Surface roughness and bond strength (SBS-test) for dry and thermocycled specimens were measured. SBS did not vary statistically between the dry groups, but thermocycling decreased the bond strengths of all the tested methods (p<0.05). After thermocycling, ABP had statistically significantly lower bond strength values compared to ABPR-S and ETC (p<0.05). Etching method with KHF₂ did not provide better bonding capacity to previously introduced and commonly adopted bonding methods.

Effect of surface treatment on the retention of zirconia crowns to tooth structure after aging

OBJECTIVE

To evaluate the effect of different surface treatments on the retention between zirconia crowns and tooth structure after in vitro aging.

MATERIALS AND METHODS

Human third molars (n = 44) received crown preparations and CAD/CAM zirconia crowns were manufactured. Specimens were divided into two groups: no aging, control (NAC, n = 11) or aging (A, n = 33). NAC were bonded with universal adhesive (UA). Aged specimens were divided into three subgroups (n = 11) according to surface treatment: Control: no abrasion + UA; Alumina: alumina abrasion + UA; Silica: tribochemical silica coating + UA. The crowns were cemented with dual-cure resin cement. Specimens in group A were aged by a combination of mechanical, thermal, and pH cycling. Retention strength values were obtained by tensile tests and results were analyzed by one-way analysis of variance (ANOVA) and Tukey test (P < .05).

RESULTS

Aging decreased the retention strength in control specimens (P < .001). Surface treatment improved the retention strength of aged specimens (P < .001), with similar results between alumina and tribochemical silica coating.

CONCLUSION

The chemical interaction between the universal bonding system and zirconia's surface was not sufficient to withstand artificial aging. Tribochemical silica coating did not promote additional retention in comparison to alumina blasting.

CLINICAL SIGNIFICANCE

The long-term retention of translucent zirconia crowns to tooth structure using phosphate-based materials is improved by means of mechanical surface treatments such as alumina blasting and tribochemical silica coating.

Resistance of bonded premolars to four artificial ageing models post enamel conditioning with a novel calcium-phosphate paste

Background

This in vitro study compares a novel calcium-phosphate etchant paste to conventional 37% phosphoric acid gel for bonding metal and ceramic brackets by evaluating the shear bond strength, remnant adhesive and enamel damage following water storage, acid challenge and fatigue loading.

Material and Methods

Metal and ceramic brackets were bonded to 240 extracted human premolars using two enamel conditioning protocols: conventional 37% phosphoric acid (PA) gel (control), and an acidic calcium-phosphate (CaP) paste. The CaP paste was prepared from β-tricalcium phosphate and monocalcium phosphate monohydrate powders mixed with 37% phosphoric acid solution, and the resulting phase was confirmed using FTIR. The bonded premolars were exposed to four artificial ageing models to examine the shear bond strength (SBS), adhesive remnant index (ARI score), with stereomicroscopic evaluation of enamel damage.

Results

Metal and ceramic control subgroups yielded significantly higher (p < 0.05) SBS (17.1-31.8 MPa) than the CaP subgroups (11.4-23.8 MPa) post all artificial ageing protocols, coupled with higher ARI scores and evidence of enamel damage. In contrast, the CaP subgroups survived all artificial ageing tests by maintaining adequate SBS for clinical performance, with the advantages of leaving unblemished enamel surface and bracket failures at the enamel-adhesive interface.

Conclusions

Enamel conditioning with acidic CaP pastes attained adequate bond strengths with no or minimal adhesive residue and enamel damage, suggesting a suitable alternative to the conventional PA gel for orthodontic bonding.

Key words:Enamel etching, calcium phosphate, bracket bond strength, adhesive residue, enamel damage.

Effect of different pH environments on the durability of bonds between zirconia and Ti-6Al-4V

This study investigated the role played by different pH environments in the deterioration of bonds between Y-TZP and Ti-6Al-4V. One hundred and thirty-five specimens were randomly assigned to one of the following storage media at 37°C: (1) distilled water, pH 6.9, DW; (2) acidic solution, pH 1-2, CS; and (3) alkaline solution, pH 10-11, KS. Shear bond strength (SBS) tests were carried out at the 4-, 14-, and 30-day storage time intervals. The morphology characteristics and elements distribution of the fracture surfaces were analyzed. CS-30 showed the lowest mean SBS and the least amount of residual cement on the Ti-6Al-4V surface after the SBS tests. Bond strength tended to decrease with increasing storage time for the acidic group. Alkaline and neutral media showed little influence on the SBS of Y-TZP to Ti-6Al-4V in 30 days. Acidic environments should be properly avoided to obtain reliable long-term bonding strength between Ti-6Al-4V and Y-TZP.

Bonding to industrial indirect composite blocks: A systematic review and meta-analysis

OBJECTIVE

The aim of this systematic review and meta-analysis was to evaluate the effect of surface conditioning methods on the bond strength of industrial indirect composite blocks (ICs).

METHODS

Based on the PICOS strategy, the Medline via PubMed, Embase and Web of Science (ISI - Web of Knowledge) electronic databases were searched for peer-reviewed articles in both English and Chinese, with no publication year limit. In vitro studies evaluating the effects of surface conditioning on the bond strength of ICs were selected. The meta-analysis was conducted to calculate the mean difference between surface-conditioned ICs and unconditioned controls. Subgroup analysis was performed to evaluate the different surface conditioning methods, separately for polymer-infiltrated ceramic network (PICN) material and the ICs with dispersed fillers (ICDFs). Meta-analyses were performed with a random-effects model at a significance level of 0.05.

RESULTS AND SIGNIFICANCE

From 802 relevant studies, 25 were selected for full-text analysis. Nineteen studies were eligible for inclusion in this systematic review, whereas 9 studies were included in the meta-analysis. A manual search of the principal periodicals specific to the area resulted in no additional articles. The meta-analysis indicated a significant difference in bond strength between the surface-conditioned ICs and controls under both non-aged and aged conditions. The combination of mechanical and chemical conditioning yielded the highest bond strength of ICs. This meta-analysis suggests that chemical etching followed by a universal primer and alumina air abrasion followed by a silane coupling agent could be considered the best strategy for optimizing the bond strength of PICN materials and ICDFs under aged conditions, respectively.

Surface Treatment Of Nanozirconia Fillers To Strengthen Dental Bisphenol A-Glycidyl Methacrylate-Based Resin Composites

Purpose

To investigate the effects of nanozirconia fillers conditioned with 10-methacryloyloxydecyl dihydrogen phosphate (MDP) with or without zirconium hydroxide precoating on bending strength, Vickers hardness, and translucence of dental resin composites.

Methods

We obtained nanozirconia fillers coated with different concentrations of Zr(OH)₄ using wet-chemical synthesis. We analyzed coating quality by observing electron-diffraction patterns using transmission electron microscopy. We conditioned zirconia fillers, with or without prior Zr(OH)₄-coating, using MDP-containing primers and evaluated the formation of chemical bonds using nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS). We then performed three-point bending-strength tests, Weibull analysis, Vickers hardness, and translucence-parameter analysis with or without addition of different concentrations of zirconia using untreated zirconia fillers as controls.

Results

We achieved desirable Zr(OH)₄ coating using 5 mmol/L zirconium chloride. NMR and XPS analysis detected stronger Zr–O–P peaks on MDP-conditioned zirconia fillers with prior Zr(OH)₄-coating compared with MDP-conditioned fillers alone, suggesting that MDP bonding with zirconia was enhanced by zirconium hydroxide. Our three-point bending-strength tests revealed that increasing levels of untreated zirconia fillers decreased the three-point bending strength of the resin composites, while MDP-conditioned zirconia fillers with or without prior Zr(OH)₄ coating improved three-point bending strengths. Adding 5 wt% and 7.5 wt% MDP-conditioned zirconia fillers with prior Zr(OH)₄ coating achieved the highest three-point bending strength. Furthermore, addition of zirconia fillers decreased the translucence of silica-based resin composites.

Conclusion

MDP conditioning with prior Zr(OH)₄ coating is recommended for treating nanozirconia fillers of resin composites.

Bond durability when applying phosphate ester monomer-containing primers vs. self-adhesive resin cements to zirconia: Evaluation after different aging conditions

PURPOSE

This study aimed to evaluate bond durability when applying 2 phosphate ester monomer-containing self-adhesive resin cements alone, versus a combination of phosphate ester monomer-containing primer conditioning plus 2 conventional resin cements requiring primers, to zirconia after different artificial aging methods.

METHODS

We cemented air-abraded zirconia plates to composite resin cylinders with self-adhesive resin cements (MS; RU) alone or cemented them with traditional resin cements (ZRV; ZVN) after pre-conditioning with a zirconia primer. A shear bond strength (SBS) test were performed after subjecting them to 19 different aging conditions (n = 15) comprising 30,000× thermocycles, air storage at room temperature (RT), water storage at RT, or at 37 °C for 24 h, 1 week, 1, 3, 6, and 12 months. Zirconia powders mixed with zirconia primer or 2 self-adhesive resin cements were characterized by X-ray photoelectron spectroscopy.

RESULTS

Groups MS and ZVN obtained the highest SBS after all of aging methods. SBS after 6 months of storage was similar to SBS after 24 h of storage, while both were higher than SBS after 1 year of storage. Water storage at 37 °C provided higher SBS than RT water storage did. We detected a Zr-O-P bond in both self-adhesive resin cement/zirconia powder mixtures.

CONCLUSIONS

Application of self-adhesive resin cements alone could be an alternative to pre-conditioning with a zirconia primer followed by the application of conventional resin cements. Formation of Zr-O-P bonds contributed to the bonding improvement of self-adhesive resin cements. Different aging conditions affected SBS values.

Adhesion to Zirconia: A Systematic Review of Current Conditioning Methods and Bonding Materials

Background. Reliable bonding between resin composite cements and high strength ceramics is difficult to achieve because of their chemical inertness and lack of silica content that makes etching impossible. The purpose of this review is to classify and analyze the existing methods and materials suggested to improve the adhesion of zirconia to dental substrate by using composite resins, in order to explore current trends in surface conditioning methods with predictable results. Methods. The current literature, examining the bond strength of zirconia ceramics, and including in vitro studies, clinical studies, and a systematic review, was analyzed. The research in the literature was carried out using PubMed and Cochrane Library databases, only papers in English, published online from 2013 to 2018. The following keywords and their combinations were used: Zirconia, 3Y-TZP, Adhesion, Adhesive cementation, Bonding, Resin, Composite resin, Composite material, Dentin, Enamel. Results. Research, in PubMed and Cochrane Library databases, provided 390 titles with abstracts. From these, a total of 93 publications were chosen for analysis. After a full text evaluation, seven articles were discarded. Therefore, the final sample was 86, including in vitro, clinical studies, and one systematic review. Various adhesive techniques with different testing methods were examined. Conclusions. Airborne-particle abrasion and tribo-chemical silica coating are the pre-treatment methods with more evidence in the literature. Increased adhesion could be expected after physico-chemical conditioning of zirconia. Surface contamination has a negative effect on adhesion. There is no evidence to support a universal adhesion protocol.

Evaluation of shear bond strength of zirconia to composite resin using different adhesive systems

Background

To evaluate shear bond strength of zirconia to composite resin using different universal and conventional adhesives and a zirconia primer.

Material and Methods

Forty zirconia blocks were fabricated of zirconium ingots (10×10×5 mm) and sintered at 1530°C for 2 hours. They were then air-abraded with Al2O3 particles. The specimens were divided into 4 groups and subjected to one of the following bonding agents: Futurabond U (group 1), Clearfil Universal Bond, universal adhesives (group 2), Z-Prime Plus, zirconia primer (group 3) and Adper Single Bond 2, conventional adhesive (group 4). Composite resin was then applied in a diameter of 5 mm and in a thickness of 2 mm. All the specimens were stored in distilled water at 37°C for 24 hours and then thermocycled between 5°C and 55°C for 5000 cycles with a 30-second dwell time. The shear bond strength was then evaluated with a universal testing machine at a crosshead speed of 1 mm/min. Data (MPa) were analyzed using ANOVA and LSD test (P≤0.05). The specimens were evaluated under a stereomicroscope to determine the mode of failure.

Results

The mean shear bond strength was 16,874 MPa in group I, 13.4434 MPa in group II, 11.6500 MPa in group III and 6.8700 MPa in group IV. ANOVA revealed that the shear bond strength in group IV was significantly lower than that in other groups (P≤0.05).

Conclusions

The shear bond strength in group I was significantly higher than that in groups III and IV. So Universal adhesives could provide higher shear bond strength of zirconia to composite resin after thermocycling compared to zirconia primers.

Key words:10-MDP, shear bond strength, universal adhesive systems, zirconia primer.

Effect of tribochemical silica coating or multipurpose products on bonding performance of a CAD/CAM resin-based material

OBJECTIVES

Nanocomposite ceramics have been widely used in clinical practice; however, a standard, recommended bonding protocol has not been determined yet. The present study aimed to evaluate application of tribochemical silica coating or multipurpose products on bonding performance of a CAD/CAM resin-based material (known as nanocomposite ceramic).

MATERIALS AND METHODS

Nanocomposite ceramic specimens were fabricated and assigned into 11 groups to build bonded specimens (n = 15) according to surface treatments (none; air particle abrasion with 50-μm alumina followed by application of a silane coupling agent or a universal adhesive; tribochemical silica coating followed by application of a silane coupling agent or a universal adhesive) and resin luting cements (conventional resin cement, RelyX Veneer; self-adhesive resin cement RelyX Unicem) used. Micro-shear bond strength (μ-SBS) was measured after 24-h water storage or ageing with 10,000 thermocycles plus additional 90-d water storage. Surface roughness after alumina air abrasion and tribochemical silica coating were determined using a profilometer. Surface morphology and element variation were observed by using a scanning electron microscope (SEM)/energy dispersion spectrum (EDS). X-ray photoelectron spectroscopy (XPS) was used to characterize nanocomposite ceramic powders conditioned with silane coupling agent or the universal adhesive used in the μ-SBS test. The nanocomposite ceramic plates received alumina air abrasion, tribochemical silica coating, or without, were determined using X-ray diffraction (XRD).

RESULTS

Nanocomposite ceramic treated with alumina air abrasion achieved the highest surface roughness, followed by those treated with tribochemical silica coating. Newly formed Si-O-Si bonds on the nanocomposite ceramic surface were detected by XPS after treatment with silane coupling agent or universal adhesive, and a Zr-O-P bond was detected after treating with universal adhesive. μ-SBS was significantly affected by bond strategies and ageing. Ageing by thermocycling and water storage significantly decreased μ-SBS. μ-SBS values derived by use of a universal adhesive or self-adhesive resin cement alone were no lower than the values derived by use of a silane coupling agent alone. Pre-silanization further enhanced the bonding improvement of universal adhesive or self-adhesive resin cement. However, tribochemical silica coating failed to provide higher μ-SBS compared with alumina air abrasion. XRD detected no monoclinic zirconia phase after alumina air abrasion or tribochemical silica coating, suggesting that these two roughening methods did not lead to phase transformation of zirconia fillers.

CONCLUSIONS

Combination of presilanization and universal adhesives improve resin bonding of nanocomposite ceramics. Tribochemical silica coating is not superior to alumina air abrasion for pretreated nanocomposite ceramics.

Evaluation of the Effect of Different Types of Abrasive Surface Treatment before and after Zirconia Sintering on Its Structural Composition and Bond Strength with Resin Cement

This study evaluated the effect of air abrasion before and after sintering with different particle type, shape, and size on the surface morphology, monoclinic phase transformation, and bond strength between resin cement and zirconia surface using primer containing silane and MDP. Airborne particle abrasion (APA) was performed on zirconia before and after sintering with different particle shape and size (50 μm Al₂O₃ and 25 μm silica powder). 120 square shaped presintered zirconia samples (Amann Girrbach) were prepared (3 mm height × 10 mm width × 10 mm length) and polished with grit papers #800, 1000, 1200, 1500, and 2000. Samples were divided into 6 groups according to surface treatment-group A: (control) no surface treatment; group B: APA 50 μm Al₂O₃ before sintering (BS); group C: APA 50 μm Al₂O₃ after sintering (AS); group D: APA25 μm silica powder (BS); group E: APA25 μm silica powder (AS) at a pressure of 3.5 bar; and group F: APA 25 μm silica powder (AS) at a pressure of 4 bar. Samples were analyzed using XRD, AFM, and SEM. The samples were submitted to shear bond strength (SBS) test. A dual cure resin cement (RelyX Ultimate) and primer (Scotchbond Universal) were used. Data were analyzed with ANOVA and Tukey test (α ≥ 0.05). APA in group B significantly increased the surface roughness when compared to all other groups. A significant monoclinic phase transformation (t-m) value was observed in groups C and F and a reverse transformation occurred in presintered groups. The SBS value of group A was 11.58 ± 1.43 and the highest significant shear bond strength value was for groups B (15.86 ± 1.92) and C (17.59 ± 2.21 MPa) with no significant difference between them. Conclusions. The use of APA 50 μm Al₂O₃ before sintering and the application of primer containing MDP seem to be valuable methods for durable bonding with zirconia. The use of APA 50 μm Al₂O₃ after sintering induced the highest (t-m) phase transformation.