Influence of Different Surface Pretreatments of Zirconium Dioxide Reinforced Lithium Disilicate Ceramics on the Shear Bond Strength of Self-Adhesive Resin Cement

AimTo analyze the influence of different surface pretreatments of zirconium dioxide reinforced lithium disilicate ceramics on the shear bond strength of self-adhesive resin cement.Materials and methodsEighty-four zirconium reinforced lithium disilicate disc Vita suprinity (Vita Zahnfabrick, Bad Säckingen, Germany) 14x12x2 mm specimens were fabricated according to the manufacturer''s recommendations. The specimens were embedded in acrylic resin blocks and randomly divided in seven groups (n=12/each) accorrding to the treatment: Group 1- 10% hydrofluoric acid; Group 2- silane; Group 3- hydrofluoric and silane; Group 4- sandblasting with silane; Group 5- Er: YAG laser+ silane; Group 6- Nd: YAG laser + silane; and the control group, in which the specimens were not treated. Round shape composite discs (Filtek Bulk fill, 3M ESPE, St.Paul, Minnesota, USA) with 3.5 mm diameter, were made for shear bond strength testing, and then cemented to the ceramic sample surface using composite cement (RelyX U200 Automix, 3M ESPE, Neuss, Germany). After cementing the composite disc on the sample, the samples were subjected to shear bond strength test of 10 N with a “stress rate” of 1 MPa / s. To determine the nature of the fracture (adhesive, cohesive or adhesive-cohesive), the broken samples were examined under a stereomicroscope. The ANOVA test and the Tukey test were used to compare the values ​​of the bond strength characteristics between different types of materials. All tests were performed with a significance level of α = 0.05.ResultsThere was a significant difference in the shear bond strength of self-adhesive cement to dental lithium-disilicate ceramics reinforced with zirconium dioxide after different preparation protocols (p<0, 05). The treatment of lithium disilicate ceramics reinforced with zirconium dioxide by silanization, sandblasting + silanization, Nd: YAG + silanization resulted in significantly higher bond strength compared to the control group. There was statistically higher bond strength of self-adhesive cement after pretreatment of lithium disilicate ceramics Nd: YAG + silanization compared to Er: YAG + silanization (p <0.05). Adhesive fracture dominated in the control group, sandblasting + silanization group, and in the laser groups, while mixed fracture dominated in other groups.ConclusionUnder the limitations of this study, the Nd:YAG irradiation with silanization could be used as pretreatment for providing greater shear bond strength of self-adhesive resin cement to zirconium reinforced lithium disilicate.     

Durable bonding to mechanically and/or chemically pre-treated dental zirconia

Objectives

To evaluate the effect of mechanical and chemical surface pre-treatment on the bond durability of two composite cements to dental zirconia.

Methods

Fully sintered IPS e.max ZirCAD (Ivoclar-Vivadent) blocks were either subjected to tribochemical silica sandblasting (CoJet, 3M ESPE) or not mechanically pre-treated. Next, the zirconia samples were either additionally pre-treated using one of two silane/MDP-combined ceramic primers (Clearfil Ceramic Primer, Kuraray; Monobond Plus, Ivoclar-Vivadent), or not further chemically pre-treated. Finally, two identically pre-treated zirconia blocks were bonded together using either a conventional BisGMA-based (Clearfil Esthetic Cement, Kuraray) or an MDP-based (Panavia F2.0, Kuraray) ‘self-etch’ dual-cure composite cement. The specimens were trimmed at the interface to a cylindrical hour-glass shape and stored for 7 days in distilled water (37 °C), after which they were randomly exposed to one of three ageing protocols: (1) immersed in 37 °C water for 10 days (10 d); (2) subjected to 10,000 thermo-cycles (TC); or (3) immersed in 37 °C water for 6 months (6 m). After storage, the micro-tensile bond strength (μTBS) was determined in MPa (n = 15–21/group). Fractographic analysis was performed using SEM.

Results

Weibull analysis revealed the highest Weibull scale and shape parameters for the ‘CoJet/Clearfil Ceramic Primer/Panavia F2.0/10d’ combination. While the BisGMA-based composite cement Clearfil Esthetic Cement (Kuraray) bonded equally well to zirconia using either tribochemical silica sandblasting (CoJet, 3M ESPE) or not, sandblasting appeared indispensable for the MDP-based and more hydrophilic composite cement Panavia F2.0 (Kuraray).

Conclusions

Combined mechanical and chemical pre-treatment can best be recommended to durably bond to zirconia.

Clinical significance

As a standard procedure to durable bond zirconia to tooth tissue, both mechanical (tribochemical silica coating) and chemical (silane/MDP-combined ceramic primers) is clinically highly recommended.     

Effects of silica coating and silane surface conditioning on the bond strength of rebonded metal and ceramic brackets

Objective

The aim of this study was to evaluate the effects of tribochemical silica coating and silane surface conditioning on the bond strength of rebonded metal and ceramic brackets.

Material and Methods

Twenty debonded metal and 20 debonded ceramic brackets were randomly assigned to receive one of the following surface treatments (n=10 for each group): (1) sandblasting (control); (2) tribochemical silica coating combined with silane. Brackets were rebonded to the enamel surface on the labial and lingual sides of premolars with a light-polymerized resin composite. All specimens were stored in distilled water for 1 week and then thermocycled (5,000 cycles) between 5-55°C. Shear bond strength values were measured using a universal testing machine. Student''s t-test was used to compare the data (α=0.05). Failure mode was assessed using a stereomicroscope, and the treated and non-treated bracket surfaces were observed by scanning electron microscopy.

Results

Rebonded ceramic brackets treated with silica coating followed by silanization had significantly greater bond strength values (17.7±4.4 MPa) than the sandblasting group (2.4±0.8 MPa, P<0.001). No significant difference was observed between the rebonded metal brackets treated with silica coating with silanization (15±3.9 MPa) and the sandblasted brackets (13.6±3.9 MPa). Treated rebonded ceramic specimens primarily exhibited cohesive failure in resin and adhesive failure at the enamel-adhesive interface.

Conclusions

In comparison to sandblasting, silica coating with aluminum trioxide particles followed by silanization resulted in higher bond strengths of rebonded ceramic brackets.     

自粘接树脂水门汀与两种粗化处理的二硅酸锂陶瓷的粘接性能评价

摘要］目的：评价自粘接树脂水门汀与喷砂和氢氟酸酸蚀两种方式粗化处理的二硅酸锂陶瓷的粘接强度及耐久性。材料和方法：制作二硅酸锂瓷片183个,烧结后随机分为2组分别进行氢氟酸酸蚀和喷砂,随后根据粘接策略的不同分为RU（RelyX Unicem）、RU200(RelyXTM U200)以及RV(silane+RelyX Veneer) 3个亚组分别制作粘接试件。各组试件一半于37℃下水储24h,另一半进行20000次冷热循环,随后测试剪切粘接强度。氢氟酸酸蚀、喷砂及未进行粗化处理的陶瓷试件采用扫描电镜观察表面形貌。结果：氢氟酸组产生显著高于喷砂组的粘接强度（p<0.05）;单纯应用自粘接树脂水门汀组的粘接效果与传统树脂水门汀结合硅烷预处理组无统计学差别（p=0.057）;所有组的粘接强度在老化后均显著降低（p<0.05）。结论：氢氟酸酸蚀可以获得较氧化铝喷砂处理更佳的粘接效果;自粘接树脂水门汀在无需硅烷预处理的条件下用于二硅酸锂陶瓷的粘接可获得较好的粘接效果。     

Bonding effectiveness to different chemically pre-treated dental zirconia

Objective

The objective of this study was to evaluate the effect of different chemical pre-treatments on the bond durability to dental zirconia.

Methods

Fully sintered IPS e.max ZirCAD (Ivoclar Vivadent) blocks were subjected to tribochemical silica sandblasting (CoJet, 3M ESPE). The zirconia samples were additionally pre-treated using one of four zirconia primers/adhesives (Clearfil Ceramic Primer, Kuraray Noritake; Monobond Plus, Ivoclar Vivadent; Scotchbond Universal, 3M ESPE; Z-PRIME Plus, Bisco). Finally, two identically pre-treated zirconia blocks were bonded together using composite cement (RelyX Ultimate, 3M ESPE). The specimens were trimmed at the interface to a cylindrical hourglass and stored in distilled water (7 days, 37 °C), after which they were randomly tested as is or subjected to mechanical ageing involving cyclic tensile stress (10 N, 10 Hz, 10,000 cycles). Subsequently, the micro-tensile bond strength was determined, and SEM fractographic analysis performed.

Results

Weibull analysis revealed the highest Weibull scale and shape parameters for the ‘Clearfil Ceramic Primer/mechanical ageing’ combination. Chemical pre-treatment of CoJet (3M ESPE) sandblasted zirconia using Clearfil Ceramic Primer (Kuraray Noritake) and Monobond Plus (Ivoclar Vivadent) revealed a significantly higher bond strength than when Scotchbond Universal (3M ESPE) and Z-PRIME Plus (Bisco) were used. After ageing, Clearfil Ceramic Primer (Kuraray Noritake) revealed the most stable bond durability.

Conclusion

Combined mechanical/chemical pre-treatment, the latter with either Clearfil Ceramic Primer (Kuraray Noritake) or Monobond Plus (Ivoclar Vivadent), resulted in the most durable bond to zirconia.

Clinical relevance

As a standard procedure to durably bond zirconia to tooth tissue, the application of a combined 10-methacryloyloxydecyl dihydrogen phosphate/silane ceramic primer to zirconia is clinically highly recommended.     

The effect of chewing simulation on surface roughness of resin composite when opposed by zirconia ceramic and lithium disilicate ceramic

Objective

To assess the change in surface roughness of nanohybrid resin composite (Tetric EvoCeram) after antagonist wear against monolithic zirconia and lithium disilicate ceramics through a simulated chewing test using a three-dimensional (3D) profilometer.

Interfacial fracture toughness of different resin cements bonded to a lithium disilicate glass ceramic

Objectives

To evaluate the effect of HF acid etching and silane treatment on the interfacial fracture toughness of a self-adhesive and two conventional resin-based cements bonded to a lithium disilicate glass ceramic.

Methods

Lithium disilicate glass ceramic discs were prepared with two different surface preparations consisting of gritblasted with aluminium oxide, and gritblasted and etched with hydrofluoric acid. Ceramic surfaces with a chevron shaped circular hole were treated by an optimized silane treatment followed by an unfilled resin and then three different resin cements (Variolink II, Panavia F2, and Multilink Sprint). Specimens were kept in distilled water at 37 °C for 24 h and then subjected to thermocycling. The interfacial fracture toughness was measured and mode of failures was also examined. Data were analysed using analysis of variance followed by T-test analysis.

Results

No statistically significant difference in the mean fracture toughness values between the gritblasted and gritblasted and etched surfaces for Variolink II resin cement was found (P > 0.05). For the gritblasted ceramic surfaces, no significant difference in the mean fracture toughness values between Panavia F2 and Variolink II was observed (P > 0.05). For the gritblasted and etched ceramic surfaces, a significantly higher fracture toughness for Panavia F2 than the other cements was found (P < 0.05).

Conclusions

The interfacial fracture toughness for the lithium disilicate glass ceramic system was affected by the surface treatment and the type of luting agent. Dual-cured resin cements demonstrated a better bonding efficacy to the lithium disilicate glass ceramic compared to the self-adhesive resin cement.

Clinical significance

The lithium disilicate glass ceramic surfaces should be gritblasted and etched to get the best bond when used with Panavia F2 and Multilink Sprint resin cements, whereas for the Variolink II only gritblasting is required. The best bond overall is achieved with Panavia F2.     

In vitro evaluation of a silane containing self-adhesive resin luting agent

ObjectivesTo investigate the setting characteristics, wettability and bonding capacity with a lithium disilicate ceramic of a silane containing self-adhesive resin luting agent (Panavia SA Universal-PU).MethodsThe degree of conversion (DC %) and extent of acid neutralization (SY %) of PU were measured on dual- (DC) and self-cured (SC) specimens after 10, 30 and 60 min storage by ATR-FTIR spectroscopy, whereas the presence of silanols was traced by curve-fitting the 60 min spectra, using the silane-free analog (Panavia SA Plus-PS) as a control. The role of a dedicated adhesive (Clearfil Universal Bond Quick-CU) in assisting the early DC % in PU-SC was investigated on 10 min-stored specimens. The water contact angles on polished and HF acid-etched lithium disilicate surfaces (IPS e.max Press), were assessed before and after silanization by unset PU or a silane primer (Ultradent Silane-SL). Finally, the shear strength of PU-DC specimens bonded to the acid-etched ceramic surfaces was determined before and after SL treatment.ResultsThe DC % was higher in DC than SC (PU, PS; all time intervals), in PU-SC than PS-SC (30, 60 min) and in the CU assisted PU-SC group. The SY % was lower in DC than SC (PU, PS) and higher in PS-SC than PU-SC groups. Silanols were found only in unset PU and PU-DC groups. SL treatment provided higher water contact angles on polished and acid-etched ceramic surfaces and higher shear bond strength on acid-etched ceramic surfaces than PU (p < 0.05 for all comparisons).SignificanceAlthough the degree of conversion of the silane containing luting agent was improved in the self-curing mode, especially in the adhesive assisted group, it was still inferior to light-curing. Acid-neutralization and presence of silanols were affected by the setting modes. The use of a silane primer enhanced the hydrophobicity and bond strength of the silane containing luting agent with the etched ceramic substrate.     

Fatigue failure load of an adhesively-cemented lithium disilicate glass-ceramic: Conventional ceramic etching vs etch & prime one-step primer

Objectives

To evaluate the effect of different glass-ceramic surface treatments and aging on the fatigue failure load of a lithium disilicate glass-ceramic adhesively cemented to a dentin analogue material.

Bonding quality of contemporary dental cements to sandblasted esthetic crown copings*

Aim: To evaluate the shear bond strength of current luting cements to sandblasted crown‐coping substrates. Methods: Specimens of nickel‐chromium, pressable glass ceramic, and zirconia crown‐coping substrates were sandblasted in three groups (n = 30 each) with 50 (group 1), 110 (group 2), and 250 μm (group 3) alumina particles at a pressure of 250 kPa. Cylinders of glass ionomer, universal resin, and self‐adhesive resin cements were then built up on the sandblasted substrate surfaces of each group (n = 10). All bonded specimens were stressed to evaluate the cement–substrate shear bond strength. Both the mode and incidence of bond failure were also considered. Results: No difference was noticed between all test groups in terms of cement–substrate bond strength. In comparison to self‐adhesive type, the universal resin cement provided lower bond strengths to both metal and glass–ceramic substrates in group 1. The self‐adhesive resin cement provided the highest bond strengths to the zirconia substrates in groups 2 and 3. The adhesive type of bond failure was common in the metal and zirconia substrates in all groups. Conclusions: Cement–substrate bonding quality is not affected by the size of sandblasting particles. Resin cements bond better to different coping substrates. Self‐adhesive resin cement is the best choice to bond zirconia‐based substrates.     

溶胶凝胶自组装法硅涂层对氧化锆陶瓷与树脂短期粘结强度的影响

目的　评价溶胶凝胶自组装法硅涂层对氧化锆陶瓷与树脂短期粘结强度的影响。方法　加工56 个氧化锆瓷块并随机分为4 组,分别对粘结面进行以下处理：A组：硅烷偶联剂;B组：溶胶凝胶浸涂1层硅涂层+硅烷偶联剂;C组：溶胶凝胶自组装2层硅涂层+硅烷偶联剂;D组：溶胶凝胶自组装3层硅涂层+硅烷偶联剂。制作56 枚光固化复合树脂圆柱并用树脂水门汀粘结于预处理后的氧化锆瓷块上,水浴24 h 后测试剪切粘结强度。以扫描电镜和表面能谱分析对不同表面处理的氧化锆进行表征分析,体视显微镜记录样品断裂模式。结果　A组到D组各组剪切粘结强度值分别为（3.05±0.26）MPa,（6.83±0.33）MPa、（10.51±0.58）MPa和（7.72±0.35）MPa。除B组和D组无统计学差异外,其余各组之间均具有统计学意义(P=0.000)。其中溶胶凝胶自组装2层硅涂层获得的剪切粘结强度值最大。结论　溶胶凝胶自组装法硅涂层可以提高氧化锆陶瓷表面粘结强度,其中溶胶凝胶自组装2层硅涂层组的效果最好。     

Influence of surface conditioning and cleaning methods on resin bonding to zirconia ceramic

Objectives

The purpose of this laboratory study was to evaluate the influence of different surface conditioning, new ceramic primers and cleaning methods on the bond strength of luting resin to zirconia ceramic (e.max ZirCAD).

Methods

A total of 96 zirconia ceramic discs were divided into six groups (n = 16) according to surface conditioning, cleaning methods and ceramic primers. Zirconia ceramic discs were either air-abraded with 110 μm alumina particles or tribochemically silica-coated (Rocatec). Visible dust resulting from air-borne particle abrasion or silica coating was removed either by oil-free air stream or by ultrasonic cleaning in alcohol. Then either a conventional silane (Espe Sil) or a universal primer containing a silane and a phosphate monomer (Monobond Plus) were applied to the conditioned surface. Transparent plastic tubes filled with composite resin were bonded to the zirconia ceramic discs using a luting resin (MultiLink Automix). The bonded specimens were stored in water at 37 °C for 3 days and for 30 days with 7500 thermal cycles between 5 °C and 55 °C prior to tensile test. Statistical analyses were conducted with three-, two- and one-way ANOVAs followed by comparison of means with Tukey's HSD test.

Results

Tensile bond strength ranged from 31.5 to 45.2 MPa after 3 days and from 10.6 to 38.8 MPa after 30 days storage in water with thermal cycling. After artificial aging the decrease in bond strength was significant when the conventional silane was applied after silica coating or when the universal primer was used after air-borne particle abrasion without ultrasonic cleaning (P < .05). However after artificial aging, the decrease in bond strength was not significant (P > .05) when the universal primer was used after air-borne particle abrasion with ultrasonic cleaning or after silica coating.

Significance

A new universal primer improved bonding to zirconia ceramic while the cleaning method had little or no effect.     

The Effect of Laser Treatment on Bonding Between Zirconia Ceramic Surface and Resin Cement

Abstract

Objective. The purpose of this in-vitro study was to evaluate and compare the effects of different surface treatments and laser irradiation on the shear bond strength of resin cement to zirconia-based ceramic. Material and methods. Forty zirconia core specimens (10-mm diameter, 2-mm thickness) were produced and embedded in the centers of autopolymerizing acrylic resin blocks. Subsequently, specimens were randomly divided into four groups, each containing 10 specimens, for different surface treatment methods. The details of the groups are as follows: Group C, no treatment applied (control); Group SB, bonding surfaces of ceramic disks were airborne particle-abraded with 110-μm alumina oxide particles; Group HF, bonding surfaces of ceramic disks were etched with 9.6% hydrofluoric acid; and Group L, bonding surfaces of ceramic disks were irradiated by a CO₂ laser. A total of 40 composite resin disks were fabricated and cemented with an adhesive resin cement to the specimen surfaces. A universal test machine was used for the shear bond strength test at a crosshead speed of 1 mm/min. Results. The highest shear bond strength values were obtained with Group L (20.99 ± 3.77 MPa) and the lowest values with Group C (13.39 ± 3.10 MPa). Although there was no significant difference between Groups C, HF and SB (P > 0.05), Group L showed a significant difference from all other groups (p < 0.05). Conclusion. All surface treatment methods improved the bond strength between resin cement and the zirconium oxide ceramic surface. CO₂ laser etching may represent an effective method for conditioning zirconia surfaces, enhancing micromechanical retention and improving the bond strength of resin cement on zirconia ceramic.     

Early bond strength of two resin cements to Y-TZP ceramic using MPS or MPS/4-META silanes

For cementation of yttrium-stabilized tetragonal zirconium polycrystal (Y-TZP) ceramic frameworks, protocols of surface-conditioning methods and available cements vary, resulting in confusion among clinicians regarding selection and effects of different conditioning methods on cement adhesion. This study evaluated the effect of two silanes (3-trimethoxysilylpropylmethacrylate (MPS) and 3-trimethoxysilylpropylmethacrylate/4-methacryloyloxyethyl trimellitate anhydride methyl methacrylate (MPS/4-META) on the adhesion of two resin-based cements (SuperBond and Panavia F 2.0) to Y-TZP ceramic and compared several protocols with those indicated by the manufacturer of each of these cements. Disks of Y-TZP ceramic (LAVA, 3M ESPE) (n = 60) were divided into six experimental groups (n = 10 per group) and treated as follows: (1) silica coating (SC) + MPS silane + SuperBond; (2) SC + MPS/4-META + silane + SuperBond); (3) SC + MPS silane + Panavia F 2.0); (4) SC + MPS/4-META silane + Panavia F 2.0); (5) no conditioning + MPS/4-META silane + Super-Bond (SuperBond instructions); and (6) 50-μm Al₂O₃ conditioning + Panavia F 2.0 (Panavia F 2.0 instructions). The specimens were subjected to shear-bond testing after water storage at 37°C for 3 months in the dark. Data were analyzed by analysis of variance and Tukey’s HSD (α = 0.05). After silica coating, the mean bond strength of SuperBond cement was not significantly different between MPS and MPS/4-META silanes (20.2 ± 3.7 and 20.9 ± 1.6 MPa, respectively), but the mean bond strength of Panavia F 2.0 was significantly higher with MPS silane (24.4 ± 5.3 MPa) than with MPS/4-META (12.3 ± 1.4 MPa) (P < 0.001). The SuperBond manufacturer’s instructions alone resulted in significantly higher bond strength (9.7 ± 3.1 MPa) than the Panavia F 2.0 manufacturer’s instruction (0 MPa) (P < 0.001). When silica coating and silanization were used, both SuperBond and Panavia F 2.0 cements demonstrated higher bond strengths they did when the manufacturers’ instructions were followed. With SuperBond, use of MPS or MPS/4-META silane resulted in no significant difference when the ceramic surface was silica coated, but with Panavia F 2.0, use of MPS silane resulted in a significantly higher bond strength than use of MPS/4-META. Use of chairside silica coating and silanization to condition the zirconia surface improved adhesion compared with the manufacturers’ cementation protocols for SuperBond and Panavia F 2.0 resin cements.     

Shear Bond Strength between Feldspathic CAD/CAM Ceramic and Human Dentine for Two Adhesive Cements

Purpose: The purpose of this study was to evaluate the shear bond strength values between dentin substrate and a feldspathic ceramic material, based on computer‐assisted design and manufacture (CAD/CAM) technology, bonded together with two adhesive systems coupled with two dual‐polymerized luting agents. In addition, the effect of a silane coupling agent on bond strength was evaluated. Material and Methods: Forty cylinders (6 mm in diameter, 5 mm thick) obtained from feldspathic ceramic blocks were cemented to the dentin of 40 recently extracted human teeth stored in saline solution at room temperature until testing. The specimens were randomly divided into four groups of ten teeth each. All specimens were airborne‐particle abraded and etched with hydrofluoric acid. In the first two groups (A1, A2) 20 ceramic cylinders were cemented using Excite DSC and Variolink II; in the A2 group the bonding surfaces were also treated with a silane coupling agent. In Groups B1 and B2, 20 ceramic cylinders were cemented using Scotchbond MPP and RelyX ARC; in the B2 group the bonding surfaces were also treated with a silane coupling agent as in Group A2. All cemented specimens were submitted to a shear bond strength test to check the strength of adhesion between the two substrates, dentin and ceramic. The data were analyzed with two‐way analysis of variance (p < 0.05). Results: The mean values of the shear bond strength were (in MPa): 22 ± 7 for Excite DSC/Variolink II without silanization (Group A1); 29 ± 3 for Excite DSC/VariolinkII with silanization (Group A2); 22 ± 4 for Scotchbond MPP/RelyX ARC without silanization (Group B1); and 26 ± 5 for Scotchbond MPP/RelyX ARC with silanization (Group B2). Two‐way ANOVA revealed a significant effect of silanization (p < 0.01) and did not reveal any significant effect for either the bonding agents (p > 0.1) or the interaction between silanization and bonding agent (p > 0.05). Multinomial logit model did not show any statistical effects on the failure mode by the shear bond strength (p > 0.1). The hypotheses of independence between failure mode (cohesive vs. adhesive) and both the adhesive system (p < 0.05) and silanization (p < 0.05) were rejected by Pearson's chi‐square test. Conclusion: Within the assumptions and limitations of this study (including the small number of specimens) both bonding systems used achieved good shear bond strength values. The application of a silane coupling agent on the ceramic surface after etching with hydrofluoric acid increased the adhesion strength with both adhesive materials used.     

The Correlation of Surface Roughness Parameters of Zirconia and Lithium Disilicate with Steatite Wear

Purpose

Various surface roughness parameters are utilized to describe the surface in the tooth to ceramics abrasion and to assess the resulting wear. The use of three-dimensional parameters may offer a better estimation for wear and an improved deduced clinical surface treatment. The aim of this study was to determine the influence of various surface roughness parameters of zirconia and lithium disilicate ceramics on the wear of steatite antagonists.

Material and methods

Forty zirconia specimens with a diameter of 7 mm and a thickness of 3 mm and 40 lithium disilicate specimens with the dimensions 10×10×4 mm were each divided into five subgroups. Two subgroups were treated with different clinically established diamond burs; a third subgroup was treated with a silicone polishing set. Two additional subgroups were produced by glazing the surfaces after treatment. Surface roughness parameters were determined by laser scanning microscopy. All specimens underwent 1.2 million loading cycles using steatite antagonists. After regular intervals of cycles, precision impressions were made to assess the wear. The correlation between wear and different roughness parameters was evaluated using the Spearman correlation test.

Results

For the glazed zirconia, unglazed zirconia, and glazed lithium disilicate specimens no significant correlations (p > 0.05) between the investigated roughness parameters and antagonist wear could be found. In the unglazed lithium disilicate groups, significant (p ≤ 0.05) correlations with steatite substance loss could be found for several roughness parameters after 1.2 million cycles.

Conclusions

For lithium disilicate, it seems not sufficient to use only one roughness parameter to indicate the wear behavior of the surface. There was no correlation between wear and the tested roughness parameters of zirconia surfaces.     

Influence of surface conditions and silane agent on the bond of resin to IPS Empress 2 ceramic

PURPOSE: The aim of this study was to evaluate the effect of different ceramic surface treatments on the tensile bond strength between IPS Empress 2 ceramic framework and Rely X adhesive resin cement, with or without the application of a silane coupling agent. MATERIALS AND METHODS: One hundred twenty disks were made, embedded in resin, and randomly divided into six groups: group 1 = sandblasting (100 microm), no silanation; group 2 = sandblasting (100 microm), silane treatment; group 3 = sandblasting (50 microm), no silanation; group 4 = sandblasting (50 microm), silane treatment; group 5 = hydrofluoric acid etching, no silanation; and group 6 = hydrofluoric acid etching, silane treatment. The disks were bonded into pairs with adhesive resin cement. All samples were stored in distilled water at 37 degrees C for 24 hours and then thermocycled. The samples were submitted to tensile testing. RESULTS: The use of silane improved the bond strength in relation to the groups in which silane was not applied (P < .05). The most effective surface treatment was etching with 10% hydrofluoric acid, both with (25.6 MPa) and without silane application (16.4 MPa); these values showed a statistically significant difference compared to sandblasting with 50- and 100-microm Al2O3. Sandblasting with 50-microm Al2O3, with (11.8 MPa) and without silane (5.4 MPa), demonstrated significantly higher tensile bond strength than sandblasting with 100-microm Al2O3, with (8.3 MPa) and without silane (3.8 MPa). CONCLUSION: Combined application of 10% hydrofluoric acid and silane enhanced the bond strength between the IPS Empress 2 ceramic framework and resin agent.     

Effect of surface pre-treatments on the zirconia ceramic-resin cement microtensile bond strength

Objective

To evaluate the influence of different surface treatments on the microtensile bond strength of resin cement to zirconia ceramic.

Materials and methods

Twelve cylinder-shaped (∅ 12 × 5.25 mm high) blocks of a commercial zirconium-oxide ceramic (Cercon^® Zirconia, DENTSPLY) were randomly divided into 4 groups (n = 3), based on the surface treatment to be performed: (1) airborne particle abrasion with 125 μm Al₂O₃ particles (S); (2) selective infiltration etching (SIE); (3) experimental hot etching solution applied for 30 min (ST) and (4) no treatment (C). Paradigm MZ100 blocks (3M ESPE) were cut into twelve cylinders of 4 mm in thickness. Composite cylinders were bonded to conditioned ceramics using a resin cement (Calibra^®, DENTSPLY), in combination with the proprietary adhesive system. After 24 h bonded specimens were cut into microtensile sticks and loaded in tension until failure. Bond strength data were analyzed with Kruskall-Wallis and Dunn's Multiple Range test for multiple comparisons (p < 0.05). Failure mode distribution was recorded and the interfacial morphology of debonded specimens was analyzed using a scanning electron microscope (SEM).

Results

Bond strength values achieved after SIE and ST treatment were significantly higher than after S treatment and without any treatment (p < 0.05). Premature failures were mostly recorded in the S group.

Significance

Conditioning the high-strength ceramic surface with SIE and ST treatments yielded higher bond strengths of the resin cement than when zirconia ceramic was treated with airborne particle abrasion or left untreated.     

Shear bond strengths of various luting cements to zirconia ceramic: surface chemical aspects

Objectives

To measure the shear bond strengths of various luting cements to a sandblasted zirconia ceramic and to determine the surface energy parameters of the luting cements.

Methods

Two conventional glass ionomer cements, two resin-modified glass ionomer cements, two compomer cements, and two adhesive resin cements were prepared and bonded to sandblasted zirconia (Lava). All bonded specimens were stored in water at 37 °C for 48 h and then half of them additionally thermocycled 10,000 times prior to the shear bond strength test (n = 10). Surface roughness (R_a) values and surface energy parameters of the eight luting cements and polished zirconia ceramic were evaluated using a profilometer and contact angle measurements, respectively (n = 10). The bond strength and surface roughness data were statistically analysed using non-parametric and parametric procedures, respectively (α = 0.05). Relationships between surface energy parameters and measured shear bond strengths were investigated using the Spearman rank correlation test.

Results

Panavia F 2.0 and Principle produced higher bond strengths than the other cements, with no significant changes before and after thermocycling. Fuji I, Ketac Cem Easymix, and Ionotite F yielded near-zero or zero values after thermocycling. All debonded specimens showed adhesive failure. Mean R_a values ranged from 0.104 to 0.167 μm. We found the base (hydrogen bond accepting) components of the luting cements significantly affected the bond strengths both before and after thermocycling.

Conclusion

It is recommended that the surface energy parameters of luting cements be considered in evaluating their adhesive properties with zirconia ceramic.     

Effect of various intermediate ceramic layers on the interfacial stability of zirconia core and veneering ceramics

Abstract

Objectives. The purposes of this study were to evaluate the effects of intermediate ceramics on the adhesion between the zirconia core and veneer ceramics. Materials and methods. The polished surfaces of fully sintered Y-TZP blocks received three different treatments: (1) connector (C), (2) liner (L) or (3) wash layer (W). All the treated zirconia blocks were veneered with either (a) fluorapatite glass-ceramic (E) or (b) feldspathic porcelain (V) and divided into four groups (CE, CV, LE and WV). For the control group, the testing surfaces of metal blocks were veneered with feldspathic porcelain (VM). A half of the samples in each group (n = 21) were exposed to thermocycling, while the other half of the specimens were stored at room temperature under dry conditions. All specimens were subjected to the shear test and the failed surfaces were microscopically examined. The elemental distribution at the zirconia core/veneer interface was analyzed. Results. The specimens in Groups CE and CV exhibited significantly greater mean bond strength values than those in Groups LE and WV, respectively (p < 0.05). However, the mean bond strengths significantly decreased in the connector groups (CE and CV) after thermal cycling (p < 0.05). The elemental analysis suggested diffusion of ceramic substances into the zirconia surface. Conclusions: A glass–ceramic based connector is significantly more favorable to core/veneer adhesion than the other intermediate ceramics evaluated in the study. However, thermal cycling affected the bond strength at the core/veneer interface differently according to the intermediate ceramics.