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Electrochemical anodization is a facile technique to synthesize ordered oxide nanostructures. Though the number of materials exhibiting anodized nanostructures has increased considerably in the recent years, only nanoporous alumina and nanotubular titania have been investigated extensively for various applications. Anodized nanostructures, nanotubes and nanopores, of zirconia are also of considerable interest for applications such as templates, sensors and solid-oxide fuel cells. In spite of the potential applications of zirconia, these nanostructures have been barely studied. As most of these applications require elevated temperatures in excess of 400C, thermal stability becomes an important attribute. Even though zirconia (Tm=2715C) has as higher melting point than alumina(Tm = 2072C), literature reports and initial research showed that the thermal stability of anodized zirconia was limited to 500C-1 h compared to 1000C-4 h for alumina. The work carried out as a part of this research showed that halide ions used in the synthesis are the possible cause for the lower thermal stability. Chemical treatment of the zirconia membranes to neutralize the halide ions helped enhance the stability to 1000C-1 h, thus, improving their usability for most of the applications mentioned above. Most of the current reported work on aluminum, zirconium, and titanium is predominantly limited to anodization of foils which can only yield free-standing nanostructures. As synthesis of these nanostructures on a substrate would further facilitate their usage, supported anodized zirconia nanostructures were synthesized by anodizing sputtered zirconium films. This study showed that the anodized morphology depends strongly on the sputtered film microstructure, which changes in accordance with the Thornton’s zone diagrams. A general approach thus developed is expected to be applicable to anodization of all metallic films. Most applications involving zirconia also require stabilization against a tetragonal-monoclinic phase transformation by suitable alloying such as with yttria. Towards this end, routes to develop anodized yttria-stabilized zirconia nanostructures, which are nonexistent, were explored. The synthesis of yttria stabilized zirconia nanostructures with no detectable monoclinic phase was achieved. Yttrium alloying using a solution treatment was found to enhance stability of the supported nanostructures to 900C-16 h, which makes it possible to now evaluate these nanostructures, especially for micro-SOFC applications.

OBJECTIVES: The aim of this in-vitro study is to evaluate the effect of different zirconia surface pretreatments, different cement types and the effect of accelerated aging on the adherence of bonding cements to zirconia. MATERIALS AND METHODS: 64 zirconia 3Y-TZP tapered rings were pressed from TZ-3YSB-E zirconia powder, pre-treated with different surface treatments, then cemented to titanium abutment pins using 8 different cements: Maxcem Elite chroma (Kerr), TheraCem (Bisco), RelyX Unicem2 (3M ESPE), Multilink Automix (Ivoclar Vivadent), Panavia SA Cement Plus (Kuraray), Ceramir C&B (Doxa), CemEZ Universal (Zest Dental), and Bifix SE (VOCO). The partitally sintered zirconia specimens were divided according to design of experment (DOE). Zirconia surface treatments: 1) control group with no surface treatment, 2) airborne particle abrasion of fully sintered zirconia ring (FS-APA50), 3) airborne particle abrasion of partially sintered zirconia (PS-APA50), 4) tribochemical silica coating of fully sintered zirconia (FS-CoJet30), 5) tribochemical silica coating of partial sintered zirconia (PS-CoJet30), and 6) nano-structured alumina coating of fully sintered zirconia (NanoAl). Zirconia rings were subjected to post-treatment:1) control 24h incubation after cementing proceedure, and 2) accelerated aging . The pull-out axial tensile retention load was tested using an Instron Model 5566A. Multi factorial linear regression model (JMP Pro 15) was used for data analysis (α=0.05). RESULTS: The retention force (N) of zirconia rings to titanium abutment pins was evaluated using a pull-out test. Four key factors were investigated in this study: zirconia surface pre-treatment, cement type, post-treatment and firing effect. There was a significant effect of zirconia surface pre-treatment on retention force (nano-structured alumina coating ≥ tribochemical abrasion = airborne-particle abrasion ≥ control). There was a significant effect of cement type on retention force [Multilink AM ≥ (Cem EZ = TheraCem = Panivia SA = RelyX Unicem2 = BiFix) ≥ Ceramir CB = Maxcem Elite]. There is a significant difference in retention strength to zirconia among post-treatment effect, with accelerated aging groups achieving slightly higher bond strength than 24h water storage groups. CONCLUSIONS: Significant different retention loads were found among tested groups. Nano-structured alumina coating surface pre-treatment has significantly higher bond strength than other treatments. Some cement systems with functional monomer had significant higher bond strengths.

OBJECTIVES: The objectives of this study was to determine the differences in failure load between cemented and fused machined veneers to zirconia while observing the effects of real time aging on failure load between cemented and fused machined veneers to zirconia. The study was to examine the differences in aging and fatigue resistance amongst a machined glass-ceramic veneer and a machined feldspathic porcelain veneer. MATERIALS AND METHODS: VITA In Ceram YZ zirconia blocks were used as a substructure framework for the three unit fixed partial denture. The veneering material was either milled IPS e.max CAD (glass-ceramic) or milled VITABLOCS Triluxe Forte (feldspathic porcelain). The types of linking material between the substructures and veneering material were either fusing or cementation. Observations were compared between aged and non-aged specimens divided into two main groups; (a) non-aged group (b) aged for three years at room temperature. Each group has two subgroups; fused and cemented which are further divided into static and cyclic fatigue at 20K, 60K and 80K. Specimens were subjected to load to failure test using universal test machine. 40% of failure load was calculated for the cyclic fatigue subgroups. In order to examine the difference in failure load between the static and fatigued specimens, the Tukey-Kramer HSD test was used to analyze the data. RESULTS AND CONCLUSIONS: The VITABLOCS Triluxe Forte (feldspathic porcelain) fused to YZ zirconia showed significantly lower failure load values compared to all the other groups (p˂0.05). The non-aged VITABLOCS Triluxe Forte cemented to YZ zirconia (static and cyclic) showed significantly higher load to failure than the aged cemented Triluxe fatigued groups (p˂0.05). There is no significant difference in failure load between IPS e.max CAD fused and IPS e.max CAD cemented to YZ zirconia framework (p˃0.05). The aged IPS e.max CAD fatigued (20K, 60K and 80K cycles) cemented to YZ zirconia showed lower significant difference in failure load among all the other IPS e.max groups. (p˂0.05).

Indiana University-Purdue University Indianapolis (IUPUI) / BACKGROUND: Phosphoric acid treatment has been reported to be relevant for zirconia cleaning after contamination. However, its interaction with different primers is not well known and needs to be investigated. OBJECTIVES: To compare the shear bond strengths (SBS) of resin cement to Y-TZP after phosphoric acid pretreatment and different chemical conditioning protocols, and to test the durability of SBSs after long term storage and thermal cycling conditions. To investigate the effect of phosphoric acid 75 on the surface roughness of a yttrium-stabilized tetragonal zirconia polycrystal ceramic (Y-TZP). METHODS: Sixty bars of zirconia (30 X 5 X 2 mm) were polished and glued to acrylic tubes. Each bar received 3 different surface treatments (control, phosphoric acid and air-abrasion). The bars were randomly assigned into five groups according to different primers applied (No primer, Clearfil ceramic primer, Monobond Plus, Z-prime plus and AZ primer). After that, resin cement was mixed, injected into a mold, and light cured. The specimens were tested in shear on a universal testing machine. Half of the specimens were tested after 24 h water storage and the other half were tested after 90 days of water storage and thermocycling. Non-contact profilometer was used to assess the effect of the three surface pretreatments on surface roughness of zirconia. Mode of failure and surface roughness were evaluated with SEM. Statistical analyses were conducted with mixed-model ANOVA and chi-square tests. RESULTS: The results indicated that Monobond Plus primer showed higher SBS after phosphoric acid treatment compared to other primers used. SBS of all air abrasion groups were higher than phosphoric acid groups. Long term water storage and thermocycling led to a statistically significant decrease in SBS for all groups except Monobond Plus, Z-prime plus and AZ primer after air abrasion treatment. Surface roughness measurements showed no significant differences among the surface treatments. CONCLUSION: Monobond Plus provided the highest SBS to zirconia after phosphoric acid treatment. The findings suggest that the air abrasion is the best surface treatment after contamination of zirconia surface. Monobond Plus, Z-prime plus and AZ primer showed durable SBS after air abrasion treatment and aging process.

Introduction: The prevalence of implant treatment has increased tremendously over the past few decades. In the process of either treating peri-implantitis or during the implant maintenance phase, it has been noted that certain implant decontamination methods may generate particles from implant surfaces. This may result in potential for disease exacerbation and irreversible damage to the implant surface. Although the Er: YAG (erbium-doped yttrium aluminum garnet) laser has been considered to have the best properties for the decontamination of the implant surface, there is limited data on the amount of titanium and zirconia particles that can be generated and released in the process. Purpose: The aim of this in vitro study was to investigate the possible generation of titanium and zirconia particles when the Er:YAG laser is used as a tool for implant decontamination and to assess for any possible surface alterations that may have resulted from the use of the Er:YAG laser. Materials and Methods: Six (N=6) Ti-Zirconium alloy (Roxolid®; Straumann® USA) and six (N=6) yttra-stabilized tetragonal zirconia (PURE® Ceramic; Straumann® USA) machined material discs, as well as two (N=2) expired Ti sandblasted acid-treated implants (Ti SLA® Implant; Straumann USA) and two (N=2) expired acid-etched zirconium-dioxide ceramic implants (PURE® Ceramic ZLA® Implant; Straumann® USA) were irradiated with the Er:YAG laser (LiteTouchTM) using the gentle treatment mode for implant decontamination for 30 and 60 seconds. The coolant water generated during laser irradiation was collected and filtered through polycarbonate track etch (PCTE) hydrophilic membrane filters using a vacuum filtration assembly unit. The PCTE membranes were then analyzed for presence of titanium and zirconia particles using a Field Emission Gun Scanning Electron Microscope (FEG-SEM). The elemental composition of the particles was compared with that of the implants and discs using Energy-dispersive X-ray spectroscopy (EDS). The surfaces of the discs and implants were also inspected for morphological alterations. The average surface roughness (Ra, Ry, Rz) of the discs before and after laser application were measured using a 2-dimensional surface profilometer. A paired sample t-test was used for statistical analysis to compare the surface roughness values before and after laser application. Results: No titanium or zirconia particles were collected after laser irradiation of the material discs after laser irradiation. Titanium and zirconia particles were detected after laser irradiation on the implants. There were no surface topographical alterations evident at higher magnification for the titanium and zirconia material discs, and implants after laser irradiation. There was a statistically significant decrease in all surface roughness parameters measured (Ra, Ry, Rz) after 60 seconds of laser irradiation for the zirconia discs. Conclusions: Within the limitations of this study, the Er:YAG laser used in gentle treatment mode for implant decontamination resulted in no visible damages to the titanium and zirconia implant surfaces. There were some titanium and zirconia particles produced during the laser irradiation on implants but no produced over discs. Additional in-vitro and clinical studies will have to be conducted to assess the clinical significance of these particles. / Oral Biology

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