Hydroxylation of dental zirconia surfaces: characterization and bonding potential

The Shear Bond Strength of Resin-Based Luting Cement to Zirconia Ceramics after Different Surface Treatments

Due to its unique properties, zirconia is increasingly being used in dentistry, but surface preparation for bonding is difficult because of its polycrystalline structure. This study aimed to determine the effect of a new etching technique (Zircos-E) on Ceramill Zi (Amann Girrbach). The effect of etching and the use of primers (Monobond Plus and MKZ Primer) on the bond strength of zirconia with resin cement (NX3) was assessed. Shear bond strength was evaluated after storage in water for 24 h and after thermal aging (5000 thermocycling at 5 °C/55 °C). A scanning electron microscope (Hitachi S-4700) was used to evaluate the surface structure before and after the Zircos-E system. The roughness parameters were assessed using an SJ-410 profilometer. The etched zirconia surface is more homogeneous over the entire surface, but some localized forms of erosion exist. The etching of zirconia ceramics caused changes in the surface structure of zirconia and a significant increase in the shear bond strength between zirconia and resin cement. The use of primers positively affects the adhesion between resin cement and zirconia. Aging with thermocycler significantly reduced the shear bond strength, with one exception-sandblasted samples with MKZ Primer. Standard ceramic surface preparation, involving only alumina sandblasting, does not provide a satisfactory bond. The use of etching with the Zircos-E system and primers had a positive effect on the strength of the zirconium-resin cement connection.

Influence of nonthermal argon plasma on the micro-shear bond strength between resin cement and translucent zirconia

Background

Considering the potential of translucent zirconia for application in esthetic restorations, it is necessary to find effective methods with the least adverse effects to increase its bond strength to resin cement.

Aims

This study aimed to test if different conservative surface treatments and cement types could affect the micro-shear bond strength (μSBS), failure mode, and bonding interface between resin cement and translucent zirconia.

Materials and Methods

In this in vitro experimental study, translucent zirconia blocks were divided into four groups based on the surface treatment they received: no treatment, argon plasma, primer (Pr), and Pr + plasma. Each group was further divided into two subgroups based on the applied cement: PANAVIA F2 and Duo-Link cement. Fourteen cement columns with a diameter of 1 mm were placed on each block (n = 14); all the specimens were immersed in 37°C water for 24 h. Afterward, μSBS was evaluated (P < 0.05), and the mode of failure was determined by a stereomicroscope (×10). The cement-zirconia interface and the surface hydrophilicity (contact angle) were also evaluated.

Statistical Analysis

Two-way analysis of variance (ANOVA) was used to evaluate the effect of surface preparation, cement types, and incubator, simultaneously (P < 0.05). The bond strengths after incubation were analyzed by one-way ANOVA (P < 0.05). Failure mode, contact angle, and cement-zirconia interface were analyzed descriptively.

Results

The highest bond strength was seen in Pr surface treatment for Duo-Link cement; however, this group was not significantly different from Pr and PANAVIA F2 cement and Pr + plasma and Duo-Link cement (P = 0.075) groups. All plasma specimens in the incubator failed prematurely. The mode of failure in all specimens was adhesive. The lowest and highest contact angles were seen in Pr + plasma and the control groups, respectively.

Conclusion

The use of Pr could successfully improve the bond strength of resin cement to translucent zirconia while plasma was not an acceptable and durable substitute.

Use of Piranha Solution as An Alternative Route to Promote Bioactivation of PEEK Surface with Low Functionalization Times

This study aimed to achieve bioactivity on the PEEK surface using piranha solution through a lower functionalization time. For this purpose, the functionalization occurred with piranha solution and 98% sulfuric acid in the proportions of 1:2, 1:1, and 2:1 at periods of 30, 60, and 90 s. The samples treated for longer times at higher concentrations registered the characteristic spectroscopy band associated with sulfonation. Additionally, both chemical treatments allowed the opening of the aromatic ring, increasing the number of functional groups available and making the surface more hydrophilic. The piranha solution treatments with higher concentrations and longer times promoted greater heterogeneity in the surface pores, which affected the roughness of untreated PEEK. Furthermore, the treatments induced calcium deposition on the surface during immersion in SBF fluid. In conclusion, the proposed chemical modifications using sulfuric acid SPEEK 90 and, especially, the piranha solution PEEK-PS 2:1-90, were demonstrated to be promising in promoting the rapid bioactivation of PEEK-based implants.

3-D Surface Morphological Characterization of CAD/CAM Milled Dental Zirconia: An In Vitro Study of the Effect of Post-Fabrication Processes

Objective: To investigate the effect on zirconia surface of the post-fabrication surface treatments on the morphological characteristics and mechanical properties of CAD/CAM milled dental zirconia specimens as well as to identify the critical parameters in the measurement of oral retention under in vitro circumstances. Method: The zirconia specimens (N = 20, n = 4) were subjected to CAD/CAM milling and divided into five groups. The specifications were: Group G1—sintered; Group G2—sintered followed by a polishing process; Group G3—sintered followed by polishing and sandblasting with alumina particles Al2O3 (110 µm); Group G4—sintered followed by sandblasting; Group G5—sintered followed by sandblasting with polishing as the end process. All the groups were subjected to Fretting wear tests, 3-D surface roughness measurements, and Vickers’s Micro hardness tests. Investigation of the phase transformation using XRD, and surface feature examination using SEM were also carried out. Additionally, one-way ANOVA, Tukey, and Pearson correlations were statistically analysed. Results: The fabrication processes had a significant effect on the performance of zirconia specimens in all the groups (p > 0.05). Specimens that underwent polishing as the last process exhibited lower surface roughness. The monoclinic phase of zirconia was observed in all the specimens before and after wear except for those in the G2 and G5 groups, where polishing was the end process. In G5, the post-wear surface properties revealed lower surface roughness and hardness. Further, the SEM and 3-D topography show grooves as seen by the dale void volume (Vvv) values; shallow valley depth (Svk); micro craters; and wear track. Conclusion: Specimens in G5 that were subjected to multistep post-fabrication process, namely sandblasting followed by polishing, yielded better results when compared to those in the other groups (G1, G2, G3, and G4). G5 with an interlayer of alumina is recommended for clinical applications due to its enhanced surface properties, mechanical properties, and low wear.

Revisiting the hydroxylation phenomenon of SiO2: a study through "hard-hard" and "soft-soft" interactions

Surface hydroxylation has been extensively studied over the years for a variety of applications, and studies involving hydroxylation of different silica surfaces are still carried out due to the interesting properties obtained from those modified surfaces. Although a number of theoretical studies have been employed to evaluate details on the hydroxylation phenomenon on silica (SiO₂) surfaces, most of these studies are based on computationally expensive models commonly based on extended systems. In order to circumvent such an aspect, here we present a low-cost theoretical study on the SiO₂ hydroxylation process aiming to evaluate aspects associated with water-SiO₂ interaction. Details about local reactivity, chemical softness, and electrostatic potential were evaluated for SiO₂ model substrates in the framework of the density functional theory (DFT) using a molecular approach. The obtained results from this new and promising approach were validated and complemented by fully atomistic reactive molecular dynamics (FARMD) simulations. Furthermore, the implemented approach proves to be a powerful tool that is not restricted to the study of hydroxylation, opening a promising route for low computational cost to analyze passivation and anchoring processes on a variety of oxide surfaces.

Surface Bioactivation of Polyether Ether Ketone (PEEK) by Sulfuric Acid and Piranha Solution: Influence of the Modification Route in Capacity for Inducing Cell Growth

The aim of this study was to promote bioactivity of the PEEK surface using sulfuric acid and piranha solution. PEEK was functionalized by a sulfuric acid treatment for 90 s and by piranha solution for 60 and 90 s. Chemical modification of the PEEK surface was evaluated by infrared spectroscopy, contact angle analysis, cytotoxicity, cell adhesion and proliferation. The spectroscopy characteristic band associated with sulfonation was observed in all treated samples. PEEK with piranha solution 60 s showed an increase in the intensity of the bands, which was even more significant for the longer treatment (90 s). The introduction of the sulfonic acid functional group reduced the contact angle. In cytotoxicity assays, for all treatments, the number of viable cells was higher when compared to those of untreated PEEK. PEEK treated with sulfuric acid and piranha solution for 60 s were the treatments that showed the highest percentage of cell viability with no statistically significant differences between them. The modified surfaces had a greater capacity for inducing cell growth, indicative of effective cell adhesion and proliferation. The proposed chemical modifications are promising for the functionalization of PEEK-based implants, as they were effective in promoting bioactivation of the PEEK surface and in stimulating cell growth and proliferation.

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

Effect of Acid Mixtures on Surface Properties and Biaxial Flexural Strength of As-Sintered and Air-Abraded Zirconia

The aim of this work was to evaluate the effects of application time of an acid mixture solution on the surface roughness, phase transformation, and biaxial flexural strength of 3Y-TZP after sintering or air abrasion. For the biaxial flexural strength measurement, 220 3Y-TZP disk-shaped specimens were prepared after as-sintering or air abrasion. The etching solution comprised a mixture of hydrofluoric acid, sulfuric acid, hydrogen peroxide, methyl alcohol, and purified water. The samples were divided into 11 subgroups according to the etching times (Control, 1, 2, 3, 5, 8, 10, 12, 15, 20, and 30 min). The results showed that acid treatment on both as-sintered and air-abraded 3Y-TZP surfaces increased the surface roughness. However, it had no significant effects on the monoclinic phase or flexural strength of as-sintered zirconia. The monoclinic phase and flexural strength of air-abraded zirconia increased sharply after air abrasion; however, they gradually decreased after acid treatment, to a similar level to the case of the untreated surface. Surface treatment with acid mixture increased the roughness, but the lack of increase of monoclinic phase is thought to be because the loose monoclinic particles remaining on the surface were removed through the etching process.

The recovery of sulfuric acid from spent piranha solution over a dimensionally stable anode (DSA) Ti-RuO2 electrode

Piranha solution is a highly acidic mixture of sulfuric acid and hydrogen peroxide. The present study aimed at developing a dimensionally stable anode (DSA), made of titanium metal foil coated with Ruthenium Dioxide (RuO₂), for the electrochemical oxidation of hydrogen peroxide in the presence of strong sulfuric acid under ambient conditions. Results showed that hydrogen peroxide in the piranha solution was fully degraded in 5 h under a constant current of 2 A (or current density of 0.32 A-cm^-2). The oxidation kinetics of hydrogen peroxide followed the Langmuir-Hinshelwood model. The observed rate constant was a function of applied current. The initial current efficiency was 17.5% at 0.5 A (or 0.08 A-cm^-2) and slightly decreased to about 13.5% at applied current between 1.3 and 1.5 A (or current density of 0.208 and 0.24 A-cm^-2). Results showed the capability and feasibility of the electrochemical oxidation process for the recovery of sulfuric acid from the spent piranha solution in semiconductor industrial installations or general laboratories.

Influence of Hydrofluoric and Nitric Acid Pre-Treatment and Type of Adhesive Cement on Retention of Zirconia Crowns

Background: The aim of this study was to test the impact of hot acids etching and two types of adhesive cement on the retention of zirconia crowns. Methods: Forty maxillary premolars were prepared, and zirconia crowns were designed and fabricated with proximal extensions, then divided into 4 groups (n = 10). Group AP; the crowns were air-abraded and cemented using Panavia SA Cement. Group AL; the crowns were air- abraded and cemented using GC LinkForce. Group AHP; the crowns were air-abraded, etched with the hot acids (48% hydrofluoric acid and 69% nitric acid), and cemented using Panavia SA Cement. Group AHL; the crowns were air-abraded, etched with the hot acids, and cemented using GC LinkForce. Each zirconia crown was pre-treated and bonded to its corresponding tooth. After thermocycling (5–55 °C/10,000), the retention test was performed and the load required to dislodge the crown was reported in Newton (N), and mode of failure was recorded. The retention strength (MPa) was calculated for each tested variable and statistically analyzed. Results: Group AHP showed the highest mean value of the retention strength, followed by group AP then group AHL. Group AL showed the lowest value. A statistically significant effect (p = 0.001) of the hot acids etching on the retention of zirconia crown was found. Also, there was a significant effect (p = 0.000) of the cement type. The interaction between surface treatment and the cement type has no significant impact (p = 0.882). The main mode of failure for Panavia SA Cement is mixed mode of failure, while for G-CEM LinkForce is adhesive failure. Conclusions: Hot acid etching pre-treatment improved the retention of zirconia crown. Usage of Panavia SA Cement with hot acids etching is effective can be used for adhesive cementation of zirconia crown.

Effect of Methacryloyloxydecyl Dihydrogen Phosphate–Containing Silane and Adhesive Used Alone or in Combination on the Bond Strength and Chemical Interaction With Zirconia Ceramics Under Thermal Aging

Clinical Relevance

Achieving durable bonding to zirconia is fundamental for the application of a methacryloyloxydecyl dihydrogen phosphate (MDP)–containing silane solution or an MDP-containing silane solution associated with an MDP-containing universal adhesive.

SUMMARY

Objectives: To evaluate the effect of a methacryloyloxydecyl dihydrogen phosphate (MDP)–containing silane coupling agent and universal adhesive, used alone or in combination, on the microshear bond strength (μSBS) to zirconia after 24 hours of water storage (24h) and after 10,000 thermocycles (TC), complemented with chemical analysis of the surface to establish the presence of MDP on the surface of the zirconia after bonding procedures.

Methods and Materials: Thirty computer-aided design/computed-aided manufacturing blocks of zirconia were cut into four sections (6×6×6 mm) and sintered. Zirconia sections (n=96) were assigned to 24 groups according to three factors: 1) silane (no silane, Monobond S [MBS], Monobond P [MB+]), 2) adhesive + resin cement (no adhesive + Enforce [ENF], no adhesive + RelyX Ultimate [REX], Prime&Bond Elect + Enforce [PBE/ENF], Scotchbond Universal + RelyX Ultimate [SBU/REX]), and 3) thermocycling (no thermocycling [24h], 10,000 thermocycles [TC]). Upon silane/adhesive application, cylinder-shaped matrices were filled with resin cement and light cured. Specimens were tested in μSBS (1.0 mm/min) after 24h or TC. The μSBS data were analyzed using twoway ANOVA and Tukey’s post hoc test (α=0.05). In addition, micro-Raman spectroscopy was used to analyze the zirconia surface for immediate chemical interaction analysis (n=24).

Results: For the 24h condition, PBE/ENF resulted in lower mean μSBS than both groups with silane without PBE (MBS and MB+ groups; p&lt;0.001). SBU alone or MB+ alone and MB+ associated with SBU showed the highest mean μSBS (p&lt;0.001). For the TC condition, all groups showed a significant decrease in mean μSBS compared with those of 24h (p&lt;0.001), with the exception of MB+ associated to SBU (p&gt;0.05). However, the application of MB+ alone or MB+ associated to SBU resulted in higher mean μSBS (p&lt;0.001) after TC than the remaining TC groups. In terms of chemical interaction, only the SBU groups, alone or combined with both of the silane agents, were associated with the methacrylate groups after rinsing.

Conclusions: The results of the current study support the use of an MDP-containing silane solution or an MDP-containing silane solution associated with an MDP-containing universal adhesive for bonding to air-abraded zirconia, as a more stable bonding after thermocycling.

The impact of non-thermal plasma on the adhesion of polyetherketoneketone (PEKK) to a veneering composite system

The PEKK material can be used in prosthodontics for framework manufacturing and is commonly laminated with veneering composites to achieve a better esthetics. Various surface treatment methods including sandblasting, etching, laser and cold plasma treatments were reported to enhance the adhesive properties of dental polymers. Both tensile and shear bond test were employed to quantify the bond strength between PEKK and veneering composites. The present in vitro study aims to evaluate the influence of acetylene, argon, air, nitrogen and oxygen plasma on the shear bond strength between PEKK and one veneering composite. Firstly, to determine which bond test type should be applied, n = 40 PEKK specimens were treated with argon plasma. Both shear and tensile bond tests were performed and compared to the control group (n = 40). In shear bond testing, values were 8.14 ± 1.70 MPa for Argon plasma while 5.83 ± 1.42 MPa for control group. In tensile bond testing, Argon plasma 1.50 ± 0.51 MPa while control group 0.58 ± 0.50 MPa. Afterwards n = 160 PEKK specimens were treated with rocatec sandblasting (n = 20), adhesive (n = 20), acetylene (n = 20), argon (n = 20), air (n = 20), nitrogen (n = 20), oxygen (n = 20) plasma types and compared to the untreated control group (n = 20) using shear bond strength test (SBS). Additionally surface roughness and scanning electron microscopy analyses were performed. The following SBS values were revealed: 10.22 ± 1.06 MPa for rocatec; 9.89 ± 3.08 MPa for acetylene, 9.16 ± 1.48 MPa for adhesive, 7.54 ± 1.52 MPa for argon, 7.09 ± 1.99 MPa for air, 7.03 ± 1.48 MPa for nitrogen, 5.69 ± 1.59 MPa for oxygen plasma types and 4.71 ± 1.54 MPa for the control group. All groups, except control group, showed SBS over 5 MPa, which means that they are suitable for the clinical application, according to ISO 10477. Acetylene showed the highest SBS among all plasma types (p < 0.0001), which was on a level of rocatec sandblasting group. Rocatec and acetylene groups demonstrated Ra values significantly different to the reference group (p < 0.0001). Plasma treatment especially with acetylene gas can be an effective more convenient surface treatment method for strengthening the bond strength between PEKK and veneering composites than traditional sandblasting/adhesive treatment.

Silane reactivity and resin bond strength to lithium disilicate ceramic surfaces

OBJECTIVE

To evaluate the silane status in commercially available products and their bonding capacity with polished glass-ceramic surfaces before and after hydrofluoric (HF) acid-etching.

METHODS

The products tested were Calibra Silane Coupling Agent/CS, G-Multi Primer/GM, Kerr Silane Primer/KS, Monobond Plus/MB and Scotchbond Universal Adhesive/SB. The silane status was studied by ¹³C nuclear magnetic resonance spectroscopy (¹³C-NMR). The roughness parameters of polished (group A) and HF acid-etched (group B) lithium disilicate glass-ceramic surfaces were measured by optical profilometry (n = 5/group). The interaction of the products with group A and B ceramic surfaces was examined by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The shear strength (SBS) of a flowable composite bonded to the ceramic surfaces (groups A, B) was assessed before (NS) and after silane treatment (n = 20/group, product).

RESULTS

The NMR analysis showed the presence of silanol monomers only in CS. Methoxylated-siloxane adducts were found in GM, silanol-siloxane adducts in MB, SB, and siloxane polymers in KS. Acid-etching greatly increased Sa, Sz, Sdr, Sc and Sv parameters (p < 0.001) and ATR-FTIR analysis demonstrated evidence of bonding with the substrate in CS. Weibull analysis of SBS revealed the following rankings in characteristic life (p < 0.05): CS > SB,KS,MB > GM > NS (group A) and CS > GM > SB,KS,MB,NS (group B). The most reliable treatment in both groups was CS. For the same silane treatment, the SBS of group B were significantly higher from group A. Failures were mainly of adhesive type, except of several partial resin cohesive failures found in group B.

SIGNIFICANCE

The chemical bonding capacity of the silanes was highest in products with silanol monomers. Acid-etching increased bond strength to a level that neutralized the silane contribution in products with silanol-siloxane adducts and siloxane polymers, providing thus bond strength values similar to silane-free treatments.

The Effect of Various Plasma Gases on the Shear Bond Strength between Unfilled Polyetheretherketone (PEEK) and Veneering Composite Following Artificial Aging

This study investigated the effect of different gaseous plasma surface treatments on the shear bond strength between unfilled polyetheretherketone (PEEK) and veneering composite resin. The study followed ISO 10477 guidelines in preparing, bonding, and testing the samples. Specimens of unfilled PEEK were distributed to one of the following six surface treatment groups: reference, adhesive, argon, nitrogen, oxygen, and air plasmas. After milling, the specimens were wet polished using (P320) polishing discs. Bonding procedures were done according to the manufacturer's instructions using (Opaquer + Dentine), except in the adhesive group (Visio.link + Opaquer + Dentine). Afterwards, thermal cycling for 5000 cycles between 5 and 55 °C in distilled water was conducted. Finally, the shear bond strengths of all groups were calculated, and mode of fracture was determined. Nitrogen surface treatment had the highest mean shear bond strength of 10.04 (±1.84) MPa, while the reference group showed the lowest value of 5.38 (±2.90) MPa. Regarding mode of fracture, all the specimens showed a 100% adhesive failure mode. Plasma surface treatment can be a reliable alternative method to the traditional protocol of bonding veneering composite resin to unfilled PEEK material.

Effects of coloring procedures on shear bond strength between resin cement and colored zirconia

PURPOSE

Debonding is expected as a frequent failure type in zirconia restorations. Therefore the aim of the current study is to evaluate the shear bond strength between colored zirconia and resin cement.

MATERIALS AND METHODS

There were 11 groups evaluated each containing 12 zirconia discs (15 mm x 12 mm x 1.6 mm). Groups were colored with the colors A3, B1, C4, D2, and D4 of the VITA classical shade scale. Coloring procedure was carried out for either 3 second or 60 seconds for the study groups and the control group was left untreated. Specimens were then bonded to translucent resin cement having a thickness of 3 mm and width of 3 mm. The shear bond strength of the samples was measured in a universal testing machine with a crosshead speed of 1 mm per minute. Two-way analysis of variance and Tukey's HSD test were used for pairwise comparisons. Also paired t-test was used for comparing groups with the same color but having different shading times.

RESULTS

Any significant difference was not found between the shear bond strengths of samples depending on whether color or shading times. Among the groups, B1 (60 seconds of coloring) had the highest bond strength (10.05 MPa), while A3 (60 seconds of coloring) showed the lowest bond strength (6.72 MPa). However, these differences were not statistically significant.

CONCLUSION

Coloring zirconia did not affect the shear bond strength between zirconia and resin cement.

Effect of airborne-particle abrasion and, acid and alkaline treatments on shear bond strength of dental zirconia

The surface roughness, morphology and shear bond strength (SBS) of dental zirconia using three different surface treatment techniques were evaluated. Three groups of sintered zirconia blocks were treated as follow, 1) Airborne-particle abrasion (APA) group (G1-APA), 50-µm Al₂O₃; 2) APA and 9% hydrofluoric acid etching (G2-HF); 3) APA and Sodium Hydroxide (G3-NaOH). The specimens were evaluated for roughness [atomic force microscope (AFM)], morphology [Scanning Electron Microscope (SEM)] and for SBS in the universal testing machine. The AFM revealed changes in the roughness after the surface treatments, however there was not Ra difference between groups, SEM analysis revealed changes in surface morphology for all surface treated specimens. For SBS, significant difference was found between G1-APA=8.4±2.7 MPa and G2-HF=3.3±0.6 MPa (p<0.05) and G2-HF and G3-NaOH=9.0±3.0 MPa (p<0.05). The main fracture mode was mixed failure (63%) for G1-APA and G3-NaOH groups. G2-HF showed 100% adhesive failure. SBS was improved with NaOH, however application of HF significantly decreased SBS.

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.

Effect of tribochemical treatments and silane reactivity on resin bonding to zirconia

OBJECTIVE

The aim of the study was to assess the roughness, structure and bond strength with zirconia of four grit-blasting treatments combined with three silane types, the reactivity of which was evaluated, as well.

METHODS

The grit-blasted treatments performed on zirconia (Lava) were alumina (ALU), CoJet (COJ), SilJet (SLJ) and SilJet Plus (SJP, with silica-encapsulated silane). The other two silanes selected were the S-Bond (SB, prehydrolyzed) and Clearfil Ceramic Primer Plus (CP, prehydrolyzed with 10-MDP). The activity of the silanols in the silanes was evaluated by FTIR spectroscopy. Optical profilometry and Raman microspectroscopy were used for the assessment of roughness (Sa, Sz, Sdr parameters) and structure (monoclinic volume-Vm) of zirconia, before (REF) and after grit-blasting, and a shear bond strength (SBS) with a flowable resin composite, for the investigation of the bonding capacity of the treatments.

RESULTS

Only SB demonstrated reactive silanols. CP and the SJP silanes were mostly in a polymerized siloxane state. Roughness was increased after grit-blasting as follows: ALU>SLJ,SJP>COJ>REF (Sa,Sz) and ALU>SLJ,COJ,SJP>REF (Sdr). ALU demonstrated the highest Vm (7.52%) from all other treatments (4.16-4.81%) and the REF (0%). COJ and SLJ showed the highest SBS (14-15.94MPa) regardless of the silane type used. SJP showed no significant differences from SLJ-SB and COJ-SB. Weibull analysis showed a reliability (β) ranking of COJ, SJP, SLJ, ALU-CP>ALU-SB>REF and a characteristic life (η) ranking of COJ, SLJ, ≥SLJ-SB, SJP, ALU≥ALU-SB,REF-CP>REF-SB.

SIGNIFICANCE

The reactivity of the silanes used showed great variations to support a predictable effect in all treatments. CP with deactivated silanols demonstrated a) the most reliable and strongest treatment with a silica-rich powder (COJ), despite the lowest Sa,Sz substrate values and b) high strength with a low-silica powder (SLJ) with higher Sa,Sz substrate values. Therefore, it may be concluded that 10-MDP greatly contributes to the bonding mechanism of the silane containing primers.

Biodegradable Materials and Metallic Implants-A Review

Recent progress made in biomaterials and their clinical applications is well known. In the last five decades, great advances have been made in the field of biomaterials, including ceramics, glasses, polymers, composites, glass-ceramics and metal alloys. A variety of bioimplants are currently used in either one of the aforesaid forms. Some of these materials are designed to degrade or to be resorbed inside the body rather than removing the implant after its function is served. Many properties such as mechanical properties, non-toxicity, surface modification, degradation rate, biocompatibility, and corrosion rate and scaffold design are taken into consideration. The current review focuses on state-of-the-art biodegradable bioceramics, polymers, metal alloys and a few implants that employ bioresorbable/biodegradable materials. The essential functions, properties and their critical factors are discussed in detail, in addition to their challenges to be overcome.

The Impact of Plasma Treatment of Cercon® Zirconia Ceramics on Adhesion to Resin Composite Cements and Surface Properties

Introduction: In recent years, the use of ceramic base zirconia is considered in dentistry for all ceramic restorations because of its chemical stability, biocompatibility, and good compressive as well as flexural strength. However, due to its chemical stability, there is a challenge with dental bonding. Several studies have been done to improve zirconia bonding but they are not reliable. The purpose of this research is to study the effect of plasma treatment on bonding strength of zirconia. Methods: In this in vitro study, 180 zirconia discs' (thickness was 0.85-0.9 mm) surfaces were processed with plasma of oxygen, argon, air and oxygen-argon combination with 90-10 and 80-20 ratio (n=30 for each group) after being polished by sandblast. Surface modifications were assessed by measuring the contact angle, surface roughness, and topographical evaluations. Cylindrical Panavia f2 resin-cement and Diafill were used for microshear strength bond measurements. The data analysis was performed by SPSS 20.0 software and one-way analysis of variance (ANOVA) and Tukey test as the post hoc. Results: Plasma treatment in all groups significantly reduces contact angle compare with control (P=0.001). Topographic evaluations revealed coarseness promotion occurred in all plasma treated groups which was significant when compared to control (P<0.05), except argon plasma treated group that significantly decreased surface roughness (P<0.05). In all treated groups, microshear bond strength increased, except oxygen treated plasma group which decreased this strength. Air and argon-oxygen combination (both groups) significantly increased microshear bond strength (P<0.05). Conclusion: According to this research, plasmatic processing with dielectric barrier method in atmospheric pressure can increase zirconia bonding strength.

Effects of air-abrasion pressure on the resin bond strength to zirconia: a combined cyclic loading and thermocycling aging study

OBJECTIVES

To determine the combined effect of fatigue cyclic loading and thermocycling (CLTC) on the shear bond strength (SBS) of a resin cement to zirconia surfaces that were previously air-abraded with aluminum oxide (Al₂O₃) particles at different pressures.

MATERIALS AND METHODS

Seventy-two cuboid zirconia specimens were prepared and randomly assigned to 3 groups according to the air-abrasion pressures (1, 2, and 2.8 bar), and each group was further divided into 2 groups depending on aging parameters (n = 12). Panavia F 2.0 was placed on pre-conditioned zirconia surfaces, and SBS testing was performed either after 24 hours or 10,000 fatigue cycles (cyclic loading) and 5,000 thermocycles. Non-contact profilometry was used to measure surface roughness. Failure modes were evaluated under optical and scanning electron microscopy. The data were analyzed using 2-way analysis of variance and χ² tests (α = 0.05).

RESULTS

The 2.8 bar group showed significantly higher surface roughness compared to the 1 bar group (p < 0.05). The interaction between pressure and time/cycling was not significant on SBS, and pressure did not have a significant effect either. SBS was significantly higher (p = 0.006) for 24 hours storage compared to CLTC. The 2 bar-CLTC group presented significantly higher percentage of pre-test failure during fatigue compared to the other groups. Mixed-failure mode was more frequent than adhesive failure.

CONCLUSIONS

CLTC significantly decreased the SBS values regardless of the air-abrasion pressure used.

The influence of Y-TZP surface treatment on topography and ceramic/resin cement interfacial fracture toughness

OBJECTIVE

Consider the efficacy of glass infiltration etching (SIE) treatment as a procedure to modify the zirconia surface resulting in higher interfacial fracture toughness.

METHODS

Y-TZP was subjected to 5 different surface treatments conditions consisting of no treatment (G1), SIE followed by hydrofluoric acid treatment (G2), heat treated at 750°C (G3), hydrofluoric acid treated (G4) and airborne-particle abrasion with alumina particles (G5). The effect of surface treatment on roughness was evaluated by Atomic Force Microscopy providing three different parameters: R_a, R_sk and surface area variation. The ceramic/resin cement interface was analyzed by Fracture Mechanics K_I test with failure mode determined by fractographic analysis. Weibull's analysis was also performed to evaluate the structural integrity of the adhesion zone.

RESULTS

G2 and G4 specimens showed very similar, and high R_a values but different surface area variation (33% for G2 and 13% for G4) and they presented the highest fracture toughness (K_IC). Weibull's analysis showed G2 (SIE) tendency to exhibit higher K_IC values than the other groups but with more data scatter and a higher early failure probability than G4 specimens.

SIGNIFICANCE

Selective glass infiltration etching surface treatment was effective in modifying the zirconia surface roughness, increasing the bonding area and hence the mechanical imbrications at the zirconia/resin cement interface resulting in higher fracture toughness (K_IC) values with higher K_IC values obtained when failure probability above 20% was expected (Weibull's distribution) among all the experimental groups.

Effect of Sandblasting Angle and Distance on Biaxial Flexural Strength of Zirconia-based Ceramics

AIM

Surface treatment is necessarily required for bonding of zirconia to the veneering porcelain and luting cements. Sandblasting is the most common and probably the most efficient surface treatment method. Sandblasting roughens the surface and may affect the flexural strength of zirconia. Different sandblasting protocols may yield variable results. This study sought to assess the effect of sandblasting angle and distance on the biaxial flexural strength of zirconia-based ceramics.

MATERIALS AND METHODS

This in vitro experimental study was conducted on 50 zirconia discs measuring 1.2 ± 0.2 mm in thickness and 15 ± 0.2 mm in diameter, which were randomly divided into five groups (n = 10) of one control and four experimental groups subjected to sandblasting with 110 μm aluminum oxide particles under 2 bar pressure for 10 seconds at 15 and 25 mm distances and 45 and 90° angles (between the nozzle head and zirconia surface). Surface roughness was measured by a roughness tester and samples were subjected to thermocycling followed by biaxial flexural strength testing according to ISO6872. The data were analyzed using one-way analysis of variance (p < 0.05).

RESULTS

No statistically significant difference was noted in the mean biaxial flexural strength of the five groups (p = 0.40). Different sandblasting protocols yielded significantly different surface roughness values (p < 0.001). The highest and the lowest mean surface roughness belonged to 15 mm/90° (0.51 μm) and control (0.001 μm) groups respectively.

CONCLUSION

Change in sandblasting angle and distance had no significant effect on the biaxial flexural strength of zirconia-based ceramic, but surface roughness was significantly different in the study groups. Clinical significances: Regardless of sandblasting angle, increasing distance to 25 mm significantly decreases surface roughness that may negatively affect zirconia bond strength.

A novel etching technique for surface treatment of zirconia ceramics to improve adhesion of resin-based luting cements

Objectives: Bonding of zirconia crowns and bridges to abutments is important, not only bonding of the thin resin layer to the abutment, but also bonding to the zirconia ceramic is crucial. Both mechanical and chemical adhesion are desired. Mechanical retention of dental porcelain achieved by etching with moderately concentrated hydrofluoric acid is not possible with zirconia ceramics.

The purpose of this study was to show that etching is possible with relative low melting fluoride compounds such as ammonium hydrogen difluoride and potassium hydrogen difluoride.

Materials and methods: Before melting, the fluorides can be introduced as powders or as aqueous slurries to the contact surfaces of the zirconia. After melting, the yttria-stabilized zirconia surface revealed a surface similar to an HF-etched dental feldspathic porcelain surface. Shear bond testing (n = 10) was performed with zirconia attached to zirconia with the Duo-Link composite luting cement (Bisco) after treatment of the etched zirconia surfaces with Bis-Silane (Bisco) and the Porcelain Bonding Resin (Bisco).

Results: Values for adhesive strength (mean ± standard deviation) after melt etching of the surfaces with initially dry powders were for K[FHF], (31.2 ± 7.5) MPa and for NH₄[FHF] (31.0 ± 11.8) MPa. When initially aqueous slurries were applied, the values were for K[FHF] (42.7 ± 12.7) MPa and for NH₄[FHF] (40.3 ± 10.0) MPa.

Conclusion: Good adhesion to zirconia can be achieved by a procedure including etching with selected melted fluoride compounds.

Direct silanization of zirconia for increased biointegration

High-performance bioinert ceramics such as zirconia have been used for biomedical devices since the early seventies. In order to promote osseointegration, the historical solution has been to increase the specific surface of the implant through roughness. Nevertheless these treatments on ceramics may create defects at the surface, exposing the material to higher chances of early failure. In zirconia, such treatments may also affect the stability of the surface. More recently, the interest of improving osseointegration of implants has moved the research focus towards the actual chemistry of the surface. Inspired by this, we have adapted the current knowledge and techniques of silica functionalization and applied it to successfully introduce 3-aminopropyldimethylethoxy silane (APDMES) directly on the surface of zirconia (3Y-TZP). We used plasma of oxygen to clean the surface and promote hydroxylation of the surface to increase silane density. The samples were extensively characterized by means of X-ray photoelectron spectroscopy (XPS) and contact angle, mechanically tested and its cytotoxicity was evaluated through cell adhesion and proliferation tests. Additionally, aging was studied to discard negative effects of the treatment on the stability of the tetragonal phase. No adverse effect was found on the mechanical response of treated samples. In addition, plasma-treated samples exhibited an unexpectedly higher resistance to aging. Finally, silane density was 35% lower than the one reported in literature for silica. However cells displayed a qualitatively higher spreading in opposition to the rounder appearance of cells on untreated zirconia. These results lay the foundations for the next generation of zirconia implants with biologically friendlier surfaces.

STATEMENT OF SIGNIFICANCE

The use of zirconia-based ceramics in biomedical devices is broad and well accepted, especially in dental implants. However, they do not bond naturally to bone, therefore to ensure fixation surgeons typically rely on roughness at different scales, or on cements. Alternatively in this work we present a new perspective of surface modification through chemistry to enhance the interaction between surface and biological environment, without the downsides of roughness. This surface treatment is proposed for zirconia, which allowed a direct silanization of its surface and a higher cell attachment. The results of this research may open the possibility for the next generation of bioinert ceramic implants with more advanced tailored surfaces for increased osseointegration.

Repair Bond Strength of Aged Resin Composite after Different Surface and Bonding Treatments

The aim of this study was to compare the effect of different mechanical surface treatments and chemical bonding protocols on the tensile bond strength (TBS) of aged composite. Bar specimens were produced using a nanohybrid resin composite and aged in distilled water for 30 days. Different surface treatments (diamond bur, phosphoric acid, silane, and sandblasting with Al₂O₃ or CoJet Sand), as well as bonding protocols (Primer/Adhesive) were used prior to application of the repair composite. TBS of the specimens was measured and the results were analyzed using analysis of variance (ANOVA) and the Student-Newman-Keuls test (α = 0.05). Mechanically treated surfaces were characterized under SEM and by profilometry. The effect of water aging on the degree of conversion was measured by means of FTIR-ATR spectroscopy. An important increase in the degree of conversion was observed after aging. No significant differences in TBS were observed among the mechanical surface treatments, despite variations in surface roughness profiles. Phosphoric acid etching significantly improved repair bond strength values. The cohesive TBS of the material was only reached using resin bonding agents. Application of an intermediate bonding system plays a key role in achieving reliable repair bond strengths, whereas the kind of mechanical surface treatment appears to play a secondary role.

Influence of Different Post-Plasma Treatment Storage Conditions on the Shear Bond Strength of Veneering Porcelain to Zirconia

This in vitro study investigated whether different storage conditions of plasma-treated zirconia specimens affect the shear bond strength of veneering porcelain. Zirconia plates were treated with a non-thermal atmospheric argon plasma (200 W, 600 s). Porcelain veneering (2.38 mm in diameter) was performed immediately (P-I) or after 24 h storage in water (P-W) or air (P-A) on the treated surfaces (n = 10). Untreated plates were used as the control. Each group was further divided into two subgroups according to the application of a ceramic liner. All veneered specimens underwent a shear bond strength (SBS) test. In the X-ray photoelectron spectroscopy (XPS) analysis, the oxygen/carbon ratios of the plasma-treated groups increased in comparison with those of the control group. When a liner was not used, the three plasma-treated groups showed significantly higher SBS values than the control group (p < 0.001), although group P-A exhibited a significantly lower value than the other two groups (p < 0.05). The liner application negatively affected bonding in groups P-I and P-W (p < 0.05). When the veneering step was delayed after plasma treatment of zirconia, storage of the specimens in water was effective in maintaining the cleaned surfaces for optimal bonding with the veneering porcelain.

Interaction of zirconia primers with yttria-stabilized zirconia surfaces

OBJECTIVES

Recently several zirconia primers have been introduced to mediate bonding of dimethacrylate resins to yttria-stabilized zirconia frameworks (Y-TZP). The aim of the study was to evaluate the changes in surface chemistry of Y-TZP frameworks induced by zirconia primer treatments.

METHODS

Polished Y-TZP discs (Lava, 3M ESPE), ultrasonicated for 10min in ethanol, water-rinsed and air-dried were treated as follows: A: Reference (no treatment), B: Treatment with Z Prime Plus (Bisco), and C: Treatment with Z-Bond (Danville Materials). The primer films formed on Y-TZP surfaces were air-dried, left intact for 5 days (dark storage, 37°C, 40% RH), rinsed with 10ml acetone to remove the loosely bound fractions, air-dried and studied by: (a) reflection optical microscopy, (b) reflection Fourier transform infrared microscopy (RFTIRM) and (c) scanning electron microscopy/energy dispersive X-ray microanalysis (SEM/EDX).

RESULTS

An amorphous thick film was observed on primed and acetone rinsed Y-TZP surfaces after B treatment, whereas C treatment formed a thinner film with phase-separated aggregates. The RFTIRM study showed that both primers induced carboxylate salt formation on Y-TZP. Phosphate groups in a dissociative form have been identified on Y-TZP, as well, indicating formation of phosphate salts. EDX analysis showed increased C, O and P content on the films, which masked the substrate contributions.

SIGNIFICANCE

The primers tested formed carboxylate and phosphate salts on Y-TZP, promoting thus chemical adhesion. However, the differences in the film forming properties and water solubility between the carboxylate and phosphate salts may affect the strength and the durability of adhesive resin interfaces with Y-TZP, as mediated by these primers.

Effect of Resin Cement Mixing Method on the Retention Strength of a CAD/CAM Zirconia Crowns

Several treatments have been suggested to improve the retention of zirconia-based restorations luted with different cements. Resin cements are believed to improve crown retention under certain circumstances. The aim of the present study was to examine the effect of three cements with different mixing methods on the retention of CAD/CAM zirconia crowns. Thirty extracted human molars were randomly divided into three groups and prepared for all-ceramic crowns (6° taper, 4-mm height and a 1.2 mm rounded shoulder finish line). A zirconia crown (Tizian CAD/CAM) was fabricated for each tooth. The crowns were air-abraded using airborne particles, adjusted, and cemented to the corresponding tooth with one of the following cements: Panavia F2 (PAN group), RelyX Unicem (UNH group) or RelyX Unicem Aplicap (UNA group). After 3,000 rounds of thermal cycling, retention was measured using a specific retentive jig and a universal testing machine. The retention strength was measured by dividing the retention force by the surface area of each tooth. The means of the pull-out test results for each group were compared using analysis of variance and Tukey's HSD test (α = 0.05). The mode of failure was examined using a stereomicroscope. The mean retention value was 6.45 (0.34) MPa for the UNA group, 4.99 MPa (0.47) for the UNH group, and 4.45 (0.39) for the PAN group; the differences among the three test groups were significant. A mixed failure was observed in 83.3 % of specimens, while no cohesive failure occurred in the crowns. Within the limitations of the present study, of the three tested cements, Relyx Unicem Aplicap cement was associated with the highest retention force for Tizian zirconia crowns.

Retention Forces between Titanium and Zirconia Components of Two-Part Implant Abutments with Different Techniques of Surface Modification

BACKGROUND

The adhesive connection between titanium base and zirconia coping of two-part abutments may be responsible for the failure rate. A high mechanical stability between both components is essential for the long-term success.

PURPOSE

The aim of the present in-vitro study was to evaluate the influence of different surface modification techniques and resin-based luting agents on the retention forces between titanium and zirconia components in two-part implant abutments.

MATERIALS AND METHODS

A total of 120 abutments with a titanium base bonded to a zirconia coping were investigated. Two different resin-based luting agents (Panavia F 2.0 and RelyX Unicem) and six different surface modifications were used to fix these components, resulting in 12 test groups (n = 10). The surface of the test specimens was mechanically pretreated with aluminium oxide blasting in combination with application of two surface activating primers (Alloy Primer, Clearfil Ceramic Primer) or a tribological conditioning (Rocatec), respectively. All specimens underwent 10,000 thermal cycles between 5°C and 55°C in a moist environment. A pull-off test was then conducted to determine retention forces between the titanium and zirconia components, and statistical analysis was performed (two-way anova). Finally, fracture surfaces were analyzed by light and scanning electron microscopy.

RESULTS

No significant differences were found between Panavia F 2.0 and RelyX Unicem. However, the retention forces were significantly influenced by the surface modification technique used (p < 0.001). For both luting agents, the highest retention forces were found when adhesion surfaces of both the titanium bases and the zirconia copings were pretreated with aluminium oxide blasting, and with the application of Clearfil Ceramic Primer.

CONCLUSION

Surface modification techniques crucially influence the retention forces between titanium and zirconia components in two-part implant abutments. All adhesion surfaces should be pretreated by sandblasting. Moreover, a phosphate-based primer serves to enhance long-term retention of the components.

Improved Resin-Zirconia Bonding by Room Temperature Hydrofluoric Acid Etching

This in vitro study was conducted to evaluate the shear bond strength of “non-self-adhesive” resin to dental zirconia etched with hydrofluoric acid (HF) at room temperature and to compare it to that of air-abraded zirconia. Sintered zirconia plates were air-abraded (control) or etched with 10%, 20%, or 30% HF for either 5 or 30 min. After cleaning, the surfaces were characterized using various analytical techniques. Three resin cylinders (Duo-Link) were bonded to each treated plate. All bonded specimens were stored in water at 37 °C for 24 h, and then half of them were additionally thermocycled 5000 times prior to the shear bond-strength tests (n = 12). The formation of micro- and nano-porosities on the etched surfaces increased with increasing concentration and application time of the HF solution. The surface wettability of zirconia also increased with increasing surface roughness. Higher concentrations and longer application times of the HF solution produced higher bond-strength values. Infiltration of the resin into the micro- and nano-porosities was observed by scanning electron microscopy. This in vitro study suggests that HF slowly etches zirconia ceramic surfaces at room temperature, thereby improving the resin–zirconia bond strength by the formation of retentive sites.

Effects of multipurpose, universal adhesives on resin bonding to zirconia ceramic

This study evaluated the effects of single-bottle, multipurpose, universal adhesives on the bond strength of resin cement to zirconia ceramic. Polished zirconia ceramic (Cercon base) discs were randomly divided into four groups (n=40) according to the applied surface-conditioning agent: Single Bond 2, Single Bond Universal, All-Bond Universal, and Alloy Primer. Cured composite cylinders (Ø 0.8 mm × 1 mm) were cemented to the conditioned zirconia specimens with resin cement (RelyX ARC). The bonded specimens were subjected to a microshear bond-strength test after 24 hours of water storage and after 10,000 cycles of thermocycling. The surface-conditioning agent significantly influenced the bond strength (p<0.05). Single Bond Universal showed the highest initial bond strength (37.7 ± 5.1 MPa), followed by All-Bond Universal (31.3 ± 5.6 MPa), Alloy Primer (26.9 ± 5.1 MPa), and Single Bond 2 (8.5 ± 4.6 MPa). Artificial aging significantly reduced the bond strengths of all the test groups (p<0.05). After 10,000 cycles of thermocycling, All-Bond Universal showed the highest bond-strength value (26.9 ± 6.4 MPa). Regardless of artificial aging, Single Bond Universal and All-Bond Universal showed significantly higher bond strengths than Alloy Primer, a conventional metal primer.

Comparison of shear test methods for evaluating the bond strength of resin cement to zirconia ceramic

OBJECTIVE

This study compared the sensitivity of three shear test methods for measuring the shear bond strength (SBS) of resin cement to zirconia ceramic and evaluated the effects of surface treatment methods on the bonding.

MATERIALS AND METHODS

Polished zirconia ceramic (Cercon base, DeguDent) discs were randomly divided into four surface treatment groups: no treatment (C), airborne-particle abrasion (A), conditioning with Alloy primer (Kuraray Medical Co.) (P) and conditioning with Alloy primer after airborne-particle abrasion (AP). The bond strengths of the resin cement (Multilink N, Ivoclar Vivadent) to the zirconia specimens of each surface treatment group were determined by three SBS test methods: the conventional SBS test with direct filling of the mold (Ø 4 mm × 3 mm) with resin cement (Method 1), the conventional SBS test with cementation of composite cylinders (Ø 4 mm × 3 mm) using resin cement (Method 2) and the microshear bond strength (μSBS) test with cementation of composite cylinders (Ø 0.8 mm × 1 mm) using resin cement (Method 3).

RESULTS

Both the test method and the surface treatment significantly influenced the SBS values. In Method 3, as the SBS values increased, the coefficients of variation decreased and the Weibull parameters increased. The AP groups showed the highest SBS in all of the test methods. Only in Method 3 did the P group show a higher SBS than the A group.

CONCLUSIONS

The μSBS test was more sensitive to differentiating the effects of surface treatment methods than the conventional SBS tests. Primer conditioning was a stronger contributing factor for the resin bond to zirconia ceramic than was airborne-particle abrasion.

Plasma in dentistry

This review describes the contemporary aspects of plasma application in dentistry. Previous studies on plasma applications were classified into two categories, surface treatment and direct applications, and were reviewed, respectively according to the approach. The current review discussed modification of dental implant surface, enhancing of adhesive qualities, enhancing of polymerization, surface coating and plasma cleaning under the topics of surface treatment. Microbicidal activities, decontamination, root canal disinfection and tooth bleaching were reviewed as direct applications with other miscellaneous ones. Non-thermal atmospheric pressure plasma was of particular focus since it is gaining considerable attention due to the possibility for its use in living tissues. Future perspectives have also been discussed briefly. Although it is still not popular among dentists, plasma has shown promises in several areas of dentistry and is now opening a new era of plasma dentistry.

Evaluation of Chemical Treatment on Zirconia Surface with Two Primer Agents and an Alkaline Solution on Bond Strength

Objectives

This study evaluated the effect of an alkaline solution and two 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-based primer agents on bond strength to zirconia (yttria-stabilized tetragonal zirconium polycrystal [Y-TZP]) through the shear bond strength (SBS) test.

Materials and Methods

Sixty square-shaped Y-TZP samples were embedded in an acrylic resin mold, polished, and randomly assigned to one of six groups (n=10) according to treatment surface: group CR, no treatment (control); group NaOH, 0.5 M NaOH; group AP, Alloy Primer; group ZP, Z-Primer Plus; group NaOH-AP, 0.5 M NaOH + Alloy Primer; and group NaOH-ZP, 0.5 M NaOH + Z-Primer Plus. The resin cement (Rely X U100) was applied inside a matrix directly onto the Y-TZP surface, and it was light-cured for 40 seconds. The samples were stored in distilled water at 37°C for 24 hours prior to the test, which was performed in a universal machine at a crosshead-speed of 0.5 mm/min. The data were analyzed by one-way analysis of variance and Tukey tests (p&lt;0.05). Light stereomicroscopy and scanning electron microscopy were used to assess the surface topography and failure mode.

Results

The SBS was significantly affected by the chemical treatment (p&lt;0.0001). The AP group displayed the best results, and the use of NaOH did not improve SBS results relative to either AP or ZP. The samples treated with Alloy Primer displayed mainly mixed failures, whereas those conditioned with Z-Primer Plus or with 0.5 M NaOH presented a balanced distribution of adhesive and mixed failure modes.

Conclusions

The use of a NaOH solution may have modified the reactivity of the Y-TZP surface, whereas the employment of a MDP/6-4-vinylbenzyl-n-propyl amino-1,3,5-triazine-2,4-dithione–based primer enhanced the Y-TZP bond strength.

Highly efficient enzyme-functionalized porous zirconia microtubes for bacteria filtration

In contrast to polymer membranes, ceramic membranes offer considerable advantages for safe drinking water provision due to their excellent chemical, thermal, and mechanical endurance. In this study, porous ceramic microtubes made of yttria stabilized zirconia (YSZ) are presented, which are conditioned for bacteria filtration by immobilizing lysozyme as an antibacterial enzyme. In accordance with determined membrane pore sizes of the nonfunctionalized microtube of ≤200 nm, log reduction values (LRV) of nearly 3 (i.e., bacterial retention of 99.9%) were obtained for bacterial retention studies using gram-positive model bacterium Micrococcus luteus. Immobilization studies of lysozyme on the membrane surface reveal an up to six times higher lysozyme loading for the covalent immobilization route as compared to unspecific immobilization. Antibacterial activity of lysozyme-functionalized microtubes was assessed by qualitative agar plate test using Micrococcus luteus as substrate showing that both the unspecific and the covalent lysozyme immobilization enhance the microtubes' antibacterial properties. Quantification of the enzyme activity at flow conditions by photometric assays reveals that the enzyme activities of lysozyme-functionalized microtubes depend strongly on applied flow rates. Intracapillary feeding of bacteria solution and higher flow rates lead to reduced enzyme activities. In consideration of different applied flow rates in the range of 0.2-0.5 mL/min, the total lysozyme activity increases by a factor of 2 for the covalent immobilization route as compared to the unspecific binding. Lysozyme leaching experiments at flow conditions for 1 h show a significant higher amount of washed-out lysozyme (factor 1.7-3.4) for the unspecific immobilization route when compared to the covalent route where the initial level of antibacterial effectiveness could be achieved by reimmobilization with lysozyme. The presented platform is highly promising for sustainable bacteria filtration.

Surface fluorination of zirconia: adhesive bond strength comparison to commercial primers

OBJECTIVE

This study evaluated contact angle and shear bond strength of three commercial zirconia primers and compared them to a recently developed fluorination pre-treatment. Earlier investigations reported that plasma fluorinated zirconia modifies the chemical bonding structure creating a more reactive surface.

MATERIALS AND METHODS

Yttria-stabilized zirconia (LAVA, 3M ESPE) plates were highly polished using 3μm diamond paste (R(a) ∼200nm) prior to pretreatments. After primer and fluorination treatment, contact angles were measured to quantify surface hydrophobicity before and after ethanol clean. Additionally, simple shear bond tests were performed to measure the adhesion strength to a composite resin.

RESULTS

Plasma fluorination produced the lowest contact angle (7.8°) and the highest shear bond strength (37.3MPa) suggesting this pretreatment facilitates a more "chemically" active surface for adhesive bonding.

CONCLUSIONS

It is hypothesized that plasma fluorination increase hydroxylation at the surface, making it more reactive, thus allowing for covalent bonding between zirconia surface and resin cement. A strong correlation was observed between contact angle and adhesion strength for all specimens; a relationship which may help understand the frequency and modes of failures, clinically. It is also believed that this surface treatment can increase long-term viability of zirconia restorations over other adhesive techniques.

Enhanced bonding between YSZ surfaces using a gas-phase fluorination pretreatment

The present investigation focuses on the surface modification, via gas-phase fluorination process, of yttria- stabilized zirconia (YSZ) to increase its wettability and chemical bonding directly to acrylate-based resin cements. YSZ plates and cylinders, as-received and roughened, were pretreated in a fluorine containing plasma and bonded with a commercially available resin cement for simple shear bond adhesion testing. No organo-silane coupling agent was used to enhance bonding between the two substrates. Shear bond tests revealed that bond strength increased with fluorination time. Furthermore, the pretreated, as received (nonroughened) specimen group displayed relatively high bond strengths suggesting surface reactivity and direct chemical bonding with the resin cement. X-ray photoelectron spectroscopy analysis revealed the surface conversion layer to be a mixture of phases; zirconium oxyfluoride, zirconium fluoride, and yttrium fluoride. It is hypothesized that these fluoride and oxyfluoride phases have the potential to increase surface hydroxylation, enabling direct covalent bonding between YSZ and resin cement. It is believed that this surface treatment has broad reaching impact when using high-strength ceramics in a multitude of bioapplications.

Adhesion/cementation to zirconia and other non-silicate ceramics: where are we now?

Non-silicate ceramics, especially zirconia, have become a topic of great interest in the field of prosthetic and implant dentistry. A clinical problem with use of zirconia-based components is the difficulty in achieving suitable adhesion with intended synthetic substrates or natural tissues. Traditional adhesive techniques used with silica-based ceramics do not work effectively with zirconia. Currently, several technologies are being utilized clinically to address this problem, and other approaches are under investigation. Most focus on surface modification of the inert surfaces of high strength ceramics. The ability to chemically functionalize the surface of zirconia appears to be critical in achieving adhesive bonding. This review will focus on currently available approaches as well as new advanced technologies to address this problem.