Bond strength and interfacial characterization of eight low fusing porcelains to cp Ti

The effect of nanocoatings of SiO2, TiO2, and ZrO2 on titanium-porcelain bonding

STATEMENT OF PROBLEM

Durable titanium-porcelain bonding is challenging because of the formation of a thick oxide layer on the surface during porcelain firing.

PURPOSE

The purpose of this in vitro study was to evaluate how atomic layer deposition (ALD) of different oxide coatings affected titanium-porcelain bonding and failure types.

MATERIAL AND METHODS

Forty-four airborne-particle abraded Type-2 titanium specimens were coated by ALD with either SiO₂, TiO₂, or ZrO₂ (n=11) at a thickness of 30 nm, whereas control specimens were left uncoated (n=11) (airborne-particle abraded only). The surface roughness of the specimens was analyzed with a profilometer before applying porcelain (Vita Titankeramic). Titanium-porcelain bonding was analyzed by using a 3-point bend test. Surface properties and titanium-porcelain interfaces were examined under scanning electron microscopy combined with energy-dispersive spectroscopy, and failure types were evaluated by using a stereomicroscope. Surface roughness and bond strength data were analyzed by 1-way ANOVA and Tukey HSD tests. Failure type data were analyzed by the Fisher-Freeman-Halton exact test (α=.05).

RESULTS

All nanocoatings increased surface roughness values, but only TiO₂ and ZrO₂ coatings showed statistically significant higher roughness than the control surfaces (P<.001). Specimens coated with SiO₂ (28.59 ±4.37 MPa) and TiO₂ (26.86 ±3.66 MPa) presented significantly higher bonding strength than control (22.04 ±4.59 MPa) specimens (P<.01). Fracture types of different groups were not statistically different (P>.05).

CONCLUSIONS

Nanocoating titanium surfaces with SiO₂ and TiO₂ by using the ALD technique significantly improved titanium-porcelain bonding.

Effects of Bonding Agents on Metal-Ceramic Bond Strength of Co-Cr Alloys Fabricated by Selective Laser Melting

Bonding agents have been developed to improve bond strength between ceramic and Co-Cr metal. The aim of this study was to investigate the influence of two bonding agents on bond strength of Co-Cr metal fabricated by selective laser melting (SLM). Bond strength was determined by a three-point bending test, and the interfaces of the metal and ceramic, before and after the bending test, were observed by optical microscopy and scanning electron microscopy (SEM) to determine the thickness of the oxide layer and amount of ceramic remaining. To analyze the elemental composition of the bonding agents and fractured surfaces, energy dispersive X-ray spectroscopy (EDS) was used. Co-Cr specimens with bonding agent showed significantly higher bond strength than Co-Cr specimens without bonding agents. The fractured surfaces of most specimens showed mixed failure, but failure mode varied according to bonding agent and fabrication type. Specimens from groups treated with bonding agents had significantly higher remaining ceramic fractions on fractured Co-Cr alloys than specimens from groups that did not receive bonding agent. Mass amounts of silicone (Si) and titanium (Ti) on the fractured alloy surfaces were also different among specimens according to method of fabrication and presence of bonding agent. Together, the results suggest that application of bonding agent to 3D printed Co-Cr metal increases bond strength with ceramics.

Effect of different firing atmospheres on debonding strength of dental porcelain fused to commercially pure titanium

An in vitro investigation was performed to evaluate the bonding characteristics of porcelain fused to metal (PFM)/commercially pure titanium (cp Ti, grade II) in three firing atmospheres of under vacuum and using two noble gases argon (Ar) and helium (He). Three groups of porcelain veneers firing under vacuum, Ar, and He were prepared to evaluate the bonding of porcelain fused to the cold-rolled cp Ti. The bond strength of PFM durability by a three-point bending test, phases, microhardness of cp Ti after firing processes, and fractures were measured and evaluated. Results show the microhardness of cp Ti in group of porcelain firing under He atmosphere was significantly lower than that of the two other groups, which were in vacuum and Ar (P < .05). X-ray diffraction showed the He group produced in relatively small amounts of TiO₂ and TiO oxides than other groups but featured relatively high quantity of airhole defects in the porcelain body leading to the lowest bond strength. The Ar group presented the highest bond strength of comparing with the groups under vacuum and using He (P < .05). Although the firing processes in He could efficiently prevent the diffusion of oxygen into Ti, the porcelain-cp Ti bond strength using Ar protective atmosphere presented the advantage to achieve clinical requirement because porcelain firing under He revealed prominent voids and defects within the body of porcelain.

Investigation on the properties of borate bonding agents: Ti6Al4V-porcelain bonding, chemical durability and preliminary cytotoxicity

The purpose of this study was to investigate the properties of the borate bonding agents (BBAS) including chemical durability, biocompatibility and bonding characteristics of porcelain to Ti6Al4V. The bond strength was performed by the three-point bending test. And the chemical durability and ion release of BBAS were tested by chemical soaking and inductively coupled plasma optical emission spectrometry (ICP-OES), respectively. Moreover, cytotoxicity was evaluated by cell viability assay and cell adhesion using human osteosarcoma cells (MG-63) and cell counter kit-8 (CCK-8) assay. To investigate the influences of composition and microstructure changes on all the properties mentioned above, the ¹¹B and ²⁷Al spectra and infrared spectra of BBAS were measured by solid-state nuclear magnetic resonance (SSNMR) and Fourier transform infrared spectroscopy (FTIR), respectively. Combined with all these properties of BBAS, the optimal addition proportion of Al₂O₃ into BBAS is 20 mol%. The relative contents of [BO3], [BO4], [AlO4], [AlO5] and [AlO6] have great influences on these properties of BBAS. BBAS, possessing excellent chemical durability, good biocompatibility and low ion release and being an effective way to improve the Ti6Al4V-porcelain bond strength, have significant clinical potentials in porcelain fused to metal restorations.

Effects of an etching solution on the adhesive properties and surface microhardness of zirconia dental ceramics

STATEMENT OF PROBLEM

Conventional approaches to adhesive bonding are not applicable to zirconia restorations. Recently, an etching solution, Zeta Etching Solution (ZES), has been introduced for etching the surface of zirconia. The effects of this etching solution on the bond strength and mechanical properties of zirconia are unknown.

PURPOSE

The purpose of this in vitro study was to examine the effects of ZES on the bond strength and surface hardness of zirconia.

MATERIAL AND METHODS

Two different types of partially stabilized tetragonal polycrystalline zirconia (TZP), Prettau zirconia (group P) and anterior Prettau (group AP), were evaluated with and without ZES etching. Each group was bonded to a zirconia substrate by using an adhesive resin cement. After 24 hours of storage in distilled water, the bond strength of the zirconia was analyzed. Vickers hardness was determined by using a microhardness tester. Scanning electron microscopy was used to analyze the surface microstructure and determine the mode of failure for each specimen. Results were analyzed and compared using 1-way ANOVA and Student t tests (α=.05).

RESULTS

Scanning electron microscopy analysis showed that etching the surface of zirconia with ZES etching solution for 60 minutes changed the morphological characteristics and microstructure of zirconia, making the surface more irregular. The changes were more pronounced for AP specimens. Etching with ZES significantly increased the shear bond strength of zirconia (P<.05) in AP specimens. The bond strength of Prettau (P group) specimens after ZES etching did not increase significantly (P>.05). An adhesive failure mode was observed for P zirconia specimens, whereas zirconia specimens exhibited a cohesive mode of failure. No significant decrease (P>.05) was observed in the mean Vickers hardness numbers.

CONCLUSIONS

Within the limitations of this in vitro study, it was concluded that etching in ZES for 30 minutes significantly enhanced the shear bond strength of highly translucent anterior Prettau (AP) zirconia restorations. Moreover, etching with ZES did not adversely affect the surface hardness of the zirconia specimens tested.

Influence of thermal and mechanical fatigue on the shear bond strength of different all-ceramic systems

Background

To evaluate the influence of thermal and mechanical fatigue on the shear bond strength of different all-ceramic cores and veneering porcelain interfaces.

Material and Methods

All-ceramic systems tested were lithium disilicate and zirconia veneered by layering technique. Sixty specimens (n=20) were subjected to shear bond strength. Ten of them were thermal and mechanical cycled. Fracture analysis was performed with stereomicroscopy and scanning electron microscopy. Energy dispersive X-ray spectroscopy analysis was performed across core/veneer interfaces.

Results

Thermal and mechanical cycling did not influence on bond strength. However, there was significant difference among systems (<0.01). CoCr group presented the highest values, followed by lithium disilicate, and zirconia. Failure modes were predominantly adhesive for CoCr, cohesive in core for lithium disilicate, and cohesive in veneer for zirconia. Energy dispersive X-ray showed interaction zone for CoCr and lithium disilicate groups and was inconclusive for zirconia. Fatigue had no influence on bond strength of groups tested.

Conclusions

The results suggest that there is a chemical bond between core and veneer materials for CoCr and lithium disilicate groups.

Key words:Ceramics, electron microscopy, fatigue, mechanical stress, shear bond strength.

Effects of silica-coating on surface topography and bond strength of porcelain fused to CAD/CAM pure titanium

The aim of this study was to evaluate the shear bond strength of porcelain fusing to titanium and the effects of surface treatment on surface structure of titanium. In the shear bond strength test, titanium surface treatments were: conventional, silica-coating without bonding agent, and silica-coating with bonding agent. Titanium surface treatments for analysis by the atomic force microscope (AFM) were: polishing, alumina sandblasting and silica-coating. The shear bond strength value of silica-coating with bonding agent group showed significantly higher than that of other groups. In AFM observation results, regular foamy structure which is effective for wetting was only observed in silica-coating. Therefore, this structure might indicate silicon. Silica-coating renders forms a nanoscopic regular foamy structure, involved in superhydrophilicity, to titanium surface, which is markedly different from the irregular surface generated by alumina sandblasting.

Evaluation of the shear bond strength of dental porcelain and the low magnetic susceptibility Zr-14Nb alloy

The aim of this study was to investigate the bond strength of dental porcelain and the preheated Zr-14Nb alloy, and compare this strength with that of titanium. White oxide layers, which were predominantly composed of monoclinic zirconia, were formed on the preheated sample groups, and exhibited a greater roughness than the control samples. At the metal-ceramic interface, a greater Nb diffusion range was observed than in the control samples. The bond strengths of the samples subjected to 20min preheating treatment were the lowest (33.6 ± 3.2 MPa), which may be ascribed to the formation of a brittle thick oxide layer under excessive heat treatment. The samples subjected to this heat treatment for 5 min exhibited the highest mean bond strength (43.7 ± 5.9 MPa), which was significantly higher than that of titanium (35.3 ± 3.5 MPa). Thus, the Zr-14Nb alloy is a promising candidate for fixed dental prosthesis, as long as the appropriate treatment conditions are adopted.

The effect of thermal cycling on the shear bond strength of porcelain/Ti-6Al-4V interfaces

The aim of the study was to evaluate the effect of thermal cycling on the shear bond strength of the porcelain/Ti-6Al-4V interfaces prepared by two different processing routes and metallic surface conditions. Polished and SiO2 particle abraded Ti-6Al-4V alloy and Triceram bonder porcelain were used to produce the interfaces. Porcelain-to-metal specimens were processed by conventional furnace firing and hot pressing. Thermal cycling was performed in Fusayama's artificial saliva for 5000 cycles between 5 ± 1 and 60 ± 2°C. After thermal cycling, shear bond tests were carried out by using a custom-made stainless steel apparatus. The results were analyzed using t-Student test and non-parametric Kruskal-Wallis test (p<0.01). Most of the polished-fired specimens were fractured during thermal cycling; thus, it was not possible to obtain the shear bond strength results for this group. Sandblasted-fired, polished-hot pressed, and sandblasted-hot pressed specimens presented the shear bond strength values of 76.2 ± 15.9, 52.2 ± 23.6, and 59.9 ± 22.0 MPa, respectively. Statistical analysis indicated that thermal cycling affected the polished specimens processed by firing, whereas a significant difference was not observed on the other groups.

Effect of Bonding Agent Application Method on Titanium-Ceramic Bond Strength

PURPOSE

Although milled titanium may be used as a substructure in fixed and implant prosthodontics, the application of the veneering porcelain presents particular challenges compared to traditional alloys. To address these challenges, some Ti ceramic systems incorporate the application of a bonding agent prior to the opaque layer. Vita Titankeramik's bonding agent is available as a powder, paste, and spray-on formulation. We examined the effect of these three application methods on the bond strength.

MATERIALS AND METHODS

Four titanium bars were milled from each of 11 wafers cut from grade II Ti using the Kavo Everest milling unit and a custom-designed milling toolpath. An experienced technician prepared the 25 × 3 × 0.5 mm(3) metal bars and applied bonding agent using one of three application methods, and then applied opaque, dentin, and enamel porcelains according to manufacturer's instructions to a 8 × 3 × 1 mm(3) porcelain. A control group received no bonding agent prior to porcelain application. The four groups (n = 11) were blindly tested for differences in bond strength using a universal testing machine in a three-point bend test configuration, based on ISO 9693-1:2012.

RESULTS

The average (SD) bond strengths for the control, powder, paste, and spray-on groups, respectively, were: 24.8 (2.6), 24.6 (2.6), 25.3 (4.0), and 24.1 (3.9) MPa. One-way ANOVA and Tukey's multiple comparison tests were performed between all groups. There were no statistically significant differences among groups (p = 0.951).

CONCLUSION

Titanium-porcelain bond strength was not affected by the use of a bonding agent or its application method when tested by ISO 9693-1 standard.

Wettability and bond strength between leucite-reinforced dental porcelains and Co-Cr alloy

STATEMENT OF PROBLEM

A series of methods has been used to evaluate metal ceramic bond strength. However, little attention has been paid to the wettability and interfacial reactions of dental porcelain/alloy systems, which may affect the bond strength of metal ceramic restorations.

PURPOSE

The purpose of this study was to understand the wetting and spreading behaviors, the interfacial reactions, and the bonding mechanism of ceramic to metal with TiO2 and MoO3 added to the dental porcelain.

MATERIAL AND METHODS

Two leucite-reinforced dental porcelains were used in the study. Twelve Co-Cr alloy sheets (15 × 10 × 2 mm) divided into 2 groups were used to evaluate the wetting process, and 12 Co-Cr alloy sheets (25 × 3 × 0.5 mm) (Bego) divided into 2 groups were used for the 3-point bond strength test. The wetting process of the porcelain/alloy systems was observed in situ with a Tommi optical dimension measurement system using a modified sessile drop method. The reaction products of the interfacial region were determined by Raman spectra analyses. Metal ceramic specimens were tested in 3-point bending at a crosshead speed of 1.5 mm/min according to ISO 9693 requirements, and the results were statistically analyzed with 1-way ANOVA (α=.05).

RESULTS

The addition of TiO2 and MoO3 in the dental porcelain improved the wettability of the dental porcelain/Co-Cr alloy system. The bond strength of the porcelain modified with TiO2 and MoO3 was 43 ±2 MPa and that of the unmodified porcelain was 38 ±3 MPa. The fracture of the 2 metal ceramic systems occurred near the porcelain layer.

CONCLUSIONS

The application of TiO2 and MoO3 to the leucite-reinforced porcelain can improve the wettability of porcelain on alloy. Porcelain/alloy wettability can be used as a guide to improve the bonding property between dental porcelain and alloys.

Improvement in Ti-porcelain bonding by SiO(2) modification of titanium surface through cast method

This study aimed to improve Ti-porcelain bonding strength through SiO2 modifications. Wax patterns were coated with SiO2 mixed with tetraethoxy silane (group C), patterns without coating were used as controls and subdivided into sandblasting group (group S) and polishing group (group P). Castingsurfaces were analyzed with XRD, while Ti-ceramic interfaces were characterized using SEM/EDS. Metal-ceramic specimens were tested in three point bending, and characterizations were also analyzed with SEM/EDS of porcelain debonding surfaces. In group C, SiO2 and Ti5Si3 phases were observed; SEM micrograph showed that Ti-porcelain had a compacted interface, and EDS maps of the interface illustrated the diffusion of Si, Al, and Sn to Ti, and cohesive fracture within the bonding agent. The bond strength of group C was 39.04±5.0 MPa, which was 15% higher than that of group S and 32% higher than that of group P. SiO2 coating could improve Ti-porcelain bond strength.

Effect of a magnetron-sputtered ZrSiN/ZrO2 film on the bond strength of commercially pure titanium to porcelain

STATEMENT OF PROBLEM

The excessively thick and nonadherent titanium oxide layer formed during the porcelain sintering process can cause bonding problems between titanium and porcelain.

PURPOSE

The purpose of this study was to evaluate the effect of a magnetron-sputtered ZrSiN/ZrO2 composite film on the bond strength of commercially pure titanium (CP Ti) to porcelain.

MATERIAL AND METHODS

Sixty-eight cast titanium specimens were prepared according to the ISO 9693 standard and then divided into 2 coated and 2 noncoated groups (n=17). The ZrSiN/ZrO2 composite film was deposited on specimens of the 2 coated groups by magnetron sputtering. A low-fusing porcelain was applied on 1 coated group and 1 noncoated group. A surface profilometer, surface roughness tester, energy-dispersive X-ray analysis (EDS), scanning electron microscopy (SEM), and x-ray diffraction (XRD) were used to examine the characteristics of the film and the interfacial properties, while the bond strength of titanium-porcelain specimens was analyzed with the 3-point bend test. The results were analyzed with an independent samples t test (α=.05).

RESULTS

The mean bond strength of ZrSiN/ZrO2-coated CP Ti to porcelain (43.67 ±2.08 MPa) was significantly higher than that of the noncoated group (35.44 ±3.56 MPa). A generally cohesive failure mode was observed in the coated group, but the failure mode in the noncoated group was adhesive. EDS data showed that the ZrSiN/ZrO2 film effectively prevented the intrusion of oxygen into the Ti substrate.

CONCLUSIONS

The data suggested that the magnetron-sputtered ZrSiN/ZrO2 film could significantly improve the bond strength of CP Ti to porcelain and this may have clinical significance.

Influence of the processing route of porcelain/Ti-6Al-4V interfaces on shear bond strength

This study aims at evaluating the two-fold effect of initial surface conditions and dental porcelain-to-Ti-6Al-4V alloy joining processing route on the shear bond strength. Porcelain-to-Ti-6Al-4V samples were processed by conventional furnace firing (porcelain-fused-to-metal) and hot pressing. Prior to the processing, Ti-6Al-4V cylinders were prepared by three different surface treatments: polishing, alumina or silica blasting. Within the firing process, polished and alumina blasted samples were subjected to two different cooling rates: air cooling and a slower cooling rate (65°C/min). Metal/porcelain bond strength was evaluated by shear bond test. The data were analyzed using one-way ANOVA followed by Tuckey's test (p<0.05). Before and after shear bond tests, metallic surfaces and metal/ceramic interfaces were examined by Field Emission Gun Scanning Electron Microscope (FEG-SEM) equipped with Energy Dispersive X-Ray Spectroscopy (EDS). Shear bond strength values of the porcelain-to-Ti-6Al-4V alloy interfaces ranged from 27.1±8.9MPa for porcelain fused to polished samples up to 134.0±43.4MPa for porcelain fused to alumina blasted samples. According to the statistical analysis, no significant difference were found on the shear bond strength values for different cooling rates. Processing method was statistically significant only for the polished samples, and airborne particle abrasion was statistically significant only for the fired samples. The type of the blasting material did not cause a statistically significant difference on the shear bond strength values. Shear bond strength of dental porcelain to Ti-6Al-4V alloys can be significantly improved from controlled conditions of surface treatments and processing methods.

The effect of zinc levels in a gold-based alloy on porcelain-metal bonding

OBJECTIVES

The purpose of this study was to ascertain whether the amount of Zn in gold alloys contributes to porcelain-metal bonding.

METHODS

Experiments were carried out using a commercial Pd-free gold alloy with a nominal composition of 88.7 wt% Au, 9.49 wt% Pt, 1.5 wt% Zn, 0.1 wt% Mn, 0.2 wt% Rh, and 0.1 wt% Ir, which contains Zn and no other elements (In, Sn, Fe) known to affect porcelain-metal bond strength. To establish the effect of oxidation of the metal surface, porcelain was applied both to preoxidized and to non-preoxidized metal specimens. The bond strength was evaluated by means of the ISO 9693: 1999 crack initiation test. A conventional gold alloy was used as a control. The elemental distributions at the porcelain/alloy interfaces were analyzed in cross section by electron probe microanalysis. Additionally, after the bond strength test, cross-sections of the interfaces of the debonded specimens were microscopically analyzed to characterize the fracture mode.

RESULTS

The Pd-free gold alloy joints showed significantly higher bond strength values than joints made with conventional gold alloy. Preoxidation treatment significantly increases the bond strength, in the preoxidized joints Zn was highly localized at the interface and diffused into the porcelain up to about 10 μm from the interface, and the joint failed by cohesive fracture in the porcelain. In contrast, the non-preoxidized joint showed mainly adhesive fracture at the porcelain/alloy interface.

SIGNIFICANCE

The presence of Zn in gold alloys plays a part in establishing chemical bonding thus improving the bond strength between porcelain and alloy.

Effect of ZrN coating by magnetron sputtering and sol-gel processed silica coating on titanium/porcelain interface bond strength

In this study, a coating technique was applied to improve the bond strength of titanium (Ti) porcelain. ZrN coating was prepared by magnetron sputtering, and silica coating was processed by a sol-gel method. The treated surfaces of the specimens were analyzed by X-ray diffraction, and the Ti/porcelain interface was investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy. The coated specimens appeared fully coherent to the Ti substrate. The fractured bonding surface was also investigated by SEM. The residual porcelain on the metal surface could be observed in the ZrN group and silica group, but there was no obvious porcelain remaining in the control group. A three-point-bending test showed that the bonding strength of the ZrN group (45.99 ± 0.65 MPa) was higher than the silica group (37.77 ± 0.78 MPa) (P < 0.001) and control group (29.48 ± 1.01 MPa) (P < 0.001), while that of the silica group was significantly higher than the control group (P < 0.001). In conclusion, conditioning the ceramic surface with ZrN and silica coatings resulted in a stronger Ti/porcelain bond. ZrN coating by magnetron sputtering was a more effective way to improve the bond strength between Ti and porcelain compared with sol-gel processed silica coating in this study.