Effects of glass-ceramic spray deposition manipulation on the surface characteristics of zirconia dental restorations

A novel glass-ceramic spray deposition (GCSD) method was developed to modify the yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) surface and to enhance the bond strength between Y-TZP and resin cement. Five different experimental groups were characterized, non-treatment (NT), airborne particle abrasion (AB), GCSD without etching (GS), GCSD with 5% HF etching (GSE5), and GCSD with 9.5% HF etching (GSE9), to determine the optimal method for improving the bond strength. Scanning electron microscopy and an argon ion milling system were used to investigate the surface and cross-sectional microstructures. The changes in the surface characteristics of Y-TZP were analyzed via contact angle analysis, atomic force microscopy, X-ray diffraction, and energy-dispersive X-ray spectrometry. The bond strengths were determined using shear bond strength test. The results revealed that GCSD could produce a dense and uniform lithium disilicate glass-ceramic coating layer and infiltrate the Y-TZP surface. This coating resulted in superior micromechanical interlocking and increased hydrophilicity, thereby enhancing the bond strength between Y-TZP and resin cement (P < 0.05). The study findings indicated that GCSD accompanied by 5% HF etching for 100 s is optimal for strengthening the Y-TZP/resin cement bond, thereby providing a novel solution for dental bonding systems.     

Effects of surface treatments on the shear bond strength of luting cements to zirconia

Objective: The aim of this in vitro study was to evaluate the effect of surface treatments on the shear bond strength of resin cements to zirconia. Material and methods: Sintered zirconia specimens (n = 192) were divided into four different surface treatment groups: control (no treatment); airborne-particle abrasion; glaze layer and hydrofluoric acid (HF) application, and hot etching solution application. Then, each group was divided into four subgroups (n = 12), and three different resin cements were applied to the zirconia surfaces. The shear bond strength value of each specimen was measured after 5000 thermo cycles. The failure types were examined with a stereomicroscope and the effects of the surface treatments were evaluated with a scanning electron microscope. Results were analyzed using analysis of variance and Tukey’s post hoc tests (α = 0.05). Results: The surface treatment and resin cement type significantly affected the bond strength results (p < 0.05). For all resin cements, the airborne-particle abrasion treatment increased the shear bond strength values (p < 0.05). The glaze layer & HF application increased shear bond strength values for all groups, except the Single Bond Universal-RelyX Unicem Aplicap group (p < 0.05). The surface roughness values of airborne-particle abraded specimens were similar to comparable values for specimens from the control group and the hot etching solution group (p > 0.05). The glaze layer & HF application group produced the highest surface roughness values (p < 0.05). Conclusion: The results of this study recommend using the appropriate combination of surface treatment and adhesive/silane coupling agent to achieve durable zirconia-resin bonding.     

Acid etching and silica coating effects on Y-TZP topography and ceramic/resin cement bond strength

Zirconia-based (Y-TZP) dental prostheses' retention loss remains one of the most frequently reported difficulties in dental practice. Selective Infiltration Etching (SIE) treatment has been proposed to alter the final Y-TZP topography improving its bond strength to resin cement. SIE consists of glass film deposition on the Y-TZP surface before glass removal with 10% hydrofluoric acid etching. This study's objective was to investigate the effects of SIE protocol steps on Y-TZP topography and its consequence on its bond strength to resin cement. The SIE protocol was divided into two main steps: silica coating (first step) and glass dissolution by hydrofluoric acid (second step), and the null hypothesis was that the SIE treatment has the same bond quality independently of the HF exposition time. Atomic Force Microscopy (AFM), Scanning Electron and Transmission Electron microscopy were used to characterize the zirconia surfaces. The bond strength was evaluated by the interfacial fracture toughness test, and data were analyzed by ANOVA and Tukey's Test (5%). As the main result, it was shown that, when exposed during sufficient time, the 10% HF can etch zirconia at room temperature, which is responsible for topographic changes, significantly improving the bond quality. Additionally, no glass components or dihedral angles modifications were observed at Y-TZP grain boundaries after silica coating. With the study limitations, it was possible to infer that the surface-modifying agent in SIE protocol is the HF etching, and the null hypothesis was rejected.     

Bonding strategies to full-contour zirconia: Zirconia pretreatment with piranha solution,glaze and airborne-particle abrasion

This study aimed to evaluate the effect of various zirconia surface pretreatments on the adhesion between full contour 3Y-TZP zirconia and glaze, and the shear bond strength (SBS) between glazed/3Y-TZP and resin cement. Specimens were allocated into groups: GL-glaze; AL+GL-sandblasting with Al₂O₃+GL; CJ+GL-tribochemical silica coating (Cojet^®/CJ)+GL; PS+GL-piranha solution+GL; and CJ. Adhesion between 3Y-TZP and GL was evaluated using the scratch test. Surface topography and glaze thickness were evaluated by using a scanning electron microscope (SEM). For SBS, glazed/3Y-TZP surface was etched with hydrofluoric acid and a silane was applied. For CJ only the silane was applied. Samples were tested after 24 h (24 h wet) or after 15,000 thermal cycles and 90 days storage (thermocycled). After SBS, the type of failure was classified as: adhesive, mixed or cohesive. The data were analyzed using two-way ANOVA and Tukey's test. SEM analysis after scratch test revealed circular cracks in the GL group and conformal cracks in the others groups. SEM micrographs suggested that zirconia specimens submitted to airborne-particle abrasion presents rougher and porous surface when compared to surfaces treated with GL and PS. The glaze layer was approximately 1.86 µm thick in all groups. After 24 h, SBS test showed highest values for AL+GL and CJ+GL and were significantly higher when compared to the GL group. Differences were not significant between PS+GL and the other groups. After aging (thermocycling+storage), groups GL and CJ presented no statistically significant difference compared to 24 h and aged AL+GL, CJ+GL and PS+GL groups. The predominant type of failure was mixed. 3Y-TZP surface treatment with glaze application could be considered as an alternative treatment, since it yielded a similar resin bond strength without the need for airborne-particle abrasion.     

Effect of the Etching Duration and Ultrasonic Cleaning on Microtensile Bond Strength Between Feldspathic Ceramic and Resin Cement

This study assessed the effect of different etching durations of feldspathic ceramic with hydrofluoric acid (HF) and ultrasonic cleaning of the etched ceramic surface on the microtensile bond strength stability of resin to a feldspathic ceramic. The research hypotheses investigated were: (1) different etching times would not affect the adhesion resistance and (2) ultrasonic cleaning would improve the adhesion. Ceramic blocks (6 × 6 × 5 mm) (N = 48) were obtained. The cementations surfaces were duplicated in resin composite. The six study groups (n = 8) were: G1—Etching with 10% aqueous HF (30 s) + silane; G2—10% HF (1 min) + silane; G3—10% HF (2 min) + silane; G4—10% HF (30 s) + ultrasonic cleaning (4 min) in distilled water +silane; G5—10% HF (1 min) + ultrasonic cleaning + silane; G6—10% HF (2 min) ultrasonic cleaning + silane. The cemented blocks were sectioned into microbars for the microtensile test. The etching duration did not create significant difference among the groups (p = .156) but significant influence of ultrasonic cleaning was observed (p = .001) (Two-way ANOVA and Tukey's test, p > 0.05). All the groups after ultrasonic cleaning presented higher bond strength (19.38–20.08 MPa) when compared with the groups without ultrasonic cleaning (16.21–17.75 MPa). The bond strength between feldspathic ceramic and resin cement was not affected by different etching durations using HF. Ultrasonic cleaning increased the bond strength between ceramic surface and resin cement, regardless of the etching duration.     

Efficacy of different surface treatments and universal adhesives on the microtensile bond strength of bulk-fill composite repair

Abstract

The purpose of this in vitro study was to evaluate the influence of different surface treatments and aging on the microtensile bond strength (μTBS) of bulk-fill composite resins. Bulk-fill composites (Filtek One; 3M ESPE) randomly received five different surface treatments: (1) no treatment, control, (2) 37% phosphoric acid etching (PA), (3) 9% hydrofluoric acid etching (HF), (4) air-borne particle abrasion with 50-μm alumina particles (Al₂O₃), (5) tribochemical silica coating (CoJet). Following, the specimens were divided into three subgroups according to universal adhesive applied: Clearfil Universal Bond (CU; Kuraray), Prime&Bond Universal (PBU; Dentsply Sirona), or Single Bond Universal (SBU; 3M ESPE). A nanofill composite (Filtek Ultimate; 3M ESPE) was employed as a repair. Bonded specimens were stored in water for 24?h at 37?°C or thermal aged, then subjected to the μTBS test. Additionally, specimens were analyzed with a contact profilometer and were evaluated with scanning electron microscopy. Control and PA treatments were showed the lowest µTBS (p?<?0.05), and there was no significant difference between these two groups (p?>?0.05). Al₂O₃ and CoJet treatments generally exhibited a similar influence on µTBS values. In addition, a correlation was found between surface roughness and bond strength (r?=?0.831). CoJet resulted in significantly higher repair µTBS values when compared to the other surface treatments. In addition, the use of silane-containing universal adhesive was increased the cohesive failure rate and maintained the repair µTBS values after thermocycling.     

Effect of experimental primers on hydrolytic stability of resin zirconia bonding

This study assessed the effect of experimental silane primers and two adhesive resin cements on resin zirconia adhesion strength. The surfaces of cut Y-TZP zirconia blocks (Lava? Frame), 16 mm × 16 mm × 4.5 mm, were pretreated twice. First, they were grit-blasted with Korox? alumina powder (110 μm) followed by silica-coating with Rocatec? Soft. Next, the blocks were randomly assigned into eighteen sub-groups (n = 6, N = 108) according to three primers (control ESPE Sil?, 1.0 vol.-% 3-acryloxypropyltrimethoxysilane, and 1.0 vol.-% 3-acryloxypropyltrimethoxysilane + 0.5 vol.-% bis-12-(triethoxysilyl)ethane), two in dentistry used resin cement products (Multilink? Speed, and Multilink? N), and three storage conditions (24 h dry, 1 month immersed in distilled water, and 6 months immersed in distilled water at room temperature) used. Onto each pretreated zirconia block, four cylindrical resin composite cement stubs were prepared and light-cured. The surface roughness, contact angle, and adhesion (shear bond) strength (SBS) were measured, and statistically analyzed (ANOVA, the Tukey’s test, p < 0.05). No statistical differences were observed in surface roughness values of different primer-treated zirconia groups. After six months of water aging, the shear bond strength of the groups that employed 1.0 vol.-% 3-acryloxypropyltrimethoxysilane (9.0 MPa ± 0.8 MPa), and the blend of 1 vol.-% 3-acryloxypropyltrimethoxysilane + 0.5 vol.-% bis-12-(triethoxysilyl)ethane (8.9 MPa ± 2.0 MPa) with Multilink? Speed resin composite cement were statistically insignificantly higher compared to using ESPE Sil? (8.7 MPa ± 1.8 MPa). The experimental primers may have potential to be used for long-term resin zirconia adhesion.     

An investigation of atomic force microscopy,surface topography and adhesion of luting cements to zirconia: effect of silica coating,zirconia primer and laser

This study evaluated the effect various surface conditioning methods on the surface topography and adhesion of luting cements to zirconia. Zirconia blocks (N?=?25) were randomly assigned to five groups according to the surface conditioning methods: (a) No conditioning, control (CON), (b) tribochemical silica coating (TSC), (c) MDP-based zirconia primer (ZRP), (d) coating with nano aluminum nitride (ALN) (e) etching with Er: YAG laser (LAS). The conditioned zirconia blocks were further divided into five subgroups to receive the luting cements: (a) MDP-based resin cement (Panavia F2.0) (PAN), (b) 4-META-based cement (Super Bond) (SUB), (c) UDMA-based (GCem) (GCE), (d) bis-GMA based (Bifix QM) (BIF) and (e) polycarboxylate cement (Poly-F) (POL). Cements were applied in polyethylene moulds (diameter: 3?mm; height: 2?mm). The bonded specimens were first thermocycled for 5500 cycles (5–55?°C) and then adhesive interface was loaded under shear (0.5?mm/min). The data (MPa) were analyzed using 2-way ANOVA, Tukey’s and Bonneferroni tests (alpha?=?0.05). Regardless of the cement type, TSC resulted in significantly higher bond strength (p???0.05) (13.3?±?4.35–25.3?±?6.3) compared to other conditioning methods (2.96?±?1.5–5.4?±?5.47). Regardless of the surface conditioning method, no significant difference was found between MDP, 4-META and UDMA based cements (p?>?0.05) being significantly higher than those of bis-GMA and polycarboxylate cements (p???0.05). Failure types were frequently adhesive in all groups. Tribochemical silica coating provided superior bond results compared to other conditioning methods tested on zirconia especially in conjunction with UDMA- and 4-META-based resin cements.     

Er,Cr:YSGG laser irradiation influence on Y-TZP bond strength to resin cement

The aim of this study was to evaluate Y-TZP surface pretreatment with different protocols on microshear bond strength (μSBS) ceramic-cement interface. One hundred and sixty pre-sintered IPS e-max ZirCAD (Ivoclar-Vivadent) blocks were randomly divided into sixteen groups according to surface treatment (n=20): G1- no treatment (control); G2- ceramic primer; G3- tribochemical silica coating; G4- tribochemical silica coating+primer; G5- airborne particle abrasion (Al₂O₃); G6- airborne particle abrasion (Al₂O₃)+primer; G7- Er,Cr:YSGG laser; G8- Er,Cr:YSGG laser+primer. All specimens were sintered before surface treatment, except lasers groups, which were sintered after laser irradiation. Ceramic blocks were bonded with Panavia F resin cement (Kuraray, Okayama, Japan) (n=10) or RelyX ARC (3M ESPE, St. Paul, MN, USA) (n=10). The μSBS tests were carried out in a universal testing machine at a speed of 1mm/min after 24 h (n=5) or 6 months storage (n=5). Differences were found for both resin cements and storage conditions in relation to μSBS values (p<0.05). However, no significant difference for interaction between factors was observed in cemented blocks with RelyX ARC. Panavia F resin cement showed significant differences for interaction between factors (p<0.05). Laser treatment was not sufficient to increase μSBS values between Y-TZP and resin cements. Tribochemical silica coating followed by primer achieved the highest immediate μSBS values. The storage did not affect negatively μSBS values to both evaluated cements.     

Influence of silicoating,etching and heated glaze treatment on the surface of Y-TZP and its impact on bonding with veneering ceramic

The study aimed to investigate the influence of surface treatments of Y-TZP on its topography and their impact on shear bond strength (SBS) of Y-TZP to veneering porcelain. Thirty-four zirconia cubes (Cercon) (10 × 10 × 10 mm³) were divided randomly into 3 groups (n = 11) according to the different surface treatments, Silica Coating (SC); Hot Solution Etching (HE); and Heat Treatment after porcelain glaze and powder application (GP). Porcelain application (IPs e.max) was performed after surface treatment using a standardized technique. Porcelain application (Ceramco-3) was also performed on 10 metal cubes (I BOND 2) as controls (MC). Specimens were subjected to thermocycling (5–55 °C, 20,000 cycles) followed by SBS testing in a universal testing machine. Surface topography was assessed by scanning electron microscopy and surface roughness (Image J). SC developed significantly higher SBS (42.10 ± 5.84 MPa) of Y-TZP to veneering ceramics compared to treatment by HE (24.0 ± 6.4 MPa), GP (23.30 ± 4.72), and the MC (29.3 ± 5.4 MPa) control (p < 0.05). SBS among HE, GP and MC specimens was comparable (p > 0.05). Y-TZP specimens treated with SC and HE showed high surface roughness compared to GP. Silicoating of Y-TZP prior to veneering can potentially reduce the high failure rates of zirconia-based restorations by enhancing the chemical bond between the core and the veneer materials.     

Effect of surface conditioning methods on the microtensile bond strength of repair composite to indirect restorative materials

This study evaluated the effect of surface conditioning methods on the microtensile bond strength (µTBS) of a restorative composite to indirect restorative materials. Blocks (5?×?5 × 4?mm³) (N?=?72) of (a) Zirconia (In-Ceram Zirconia, Vita) (ZR), (b) lithium disilicate glass ceramic (IPS Empress II, Ivoclar Vivadent) (LD), (c) Indirect resin composite (Gradia, GC) (GR) were fabricated (n?=?24 per group) and divided randomly into three groups: 1-Control: no conditioning, 2-Silane coupling agent, 3-Hydrofluoric acid (9.5%) (HF)+silane. Each block was duplicated in resin composite. The adhesion surfaces were conditioned with airborne-particle abrasion (110?µm Al₂O₃ particles). Half of the conditioned blocks received no bonding and the other half one coat of bonding (ED Primer II, Kuraray). Each conditioned block was bonded to a composite block with a resin luting agent (Panavia F2.0, Kuraray). The blocks were sectioned into 1?mm² microsticks and tested for microtensile bond strength (µTBS) (0.5?mm/min) in a μTBS testing machine. Failure types were evaluated under stereomicroscope and Scanning Electron Microscope (SEM). Data were analyzed using three-way ANOVA, Bonferroni corrected and independent sample t-tests (p?<?0.05). Significant effect of the bonding (p?<?0.001) and surface conditioning (p?<?0.001) were observed in all groups. The highest mean bond strength values were obtained in the bonded, HF etched and silanized groups of ZR, LD and GR (12.4?±?2.9, 28.1?±?1.5 and 27.2?±?2?MPa, respectively). HF acid?+?silane increased the repair bond values in all materials. Majority of the failure types were adhesive for ZR group, whereas HF?+?silane conditioned LD and GR groups presented predominantly cohesive failures in the cement.     

Influence of different etching protocols on the reliability of resin bonding to CAD/CAM feldspathic porcelain

ObjectivesTo evaluate the effects of different acid etching times on the mechanical strength of dental porcelain as well as the influence on the reliability of resin bonded CAD/CAM porcelain veneer.Material and MethodsRectangular CAM/CAM feldspathic porcelain (Mark II, Vita Zahnfabrik) specimens (12 mm×10 mm×4 mm) were prepared and polished with silicon carbide abrasive paper under running water. All the samples were randomly divided into four groups according to the corresponding etching protocols: control group (without any treatment), group A (etched with a gel etchant containing 5% hydrofluoric acid for 30 s and rinsed with de-ionized water), group B (etched for 1 min and rinsed), group C (etched for 2 min and rinsed). After silanization, resin stubs were adhered on porcelain surface. There are 25 resin–porcelain samples prepared in each group and subjected to the shear bond strength testing. Weibull analysis was conducted to evaluate of the reliability of resin–porcelain bonding. For each of the etching method, eight additional porcelain samples (3 mm×2 mm×10 mm) were prepared and etched. Then, surface roughness (R_a), microhardness (Vickers Hardness) and biaxial flexural strengths were measured on these porcelain specimens. Energy dispersive X-ray spectrometry technique was used to assess the changes in surface chemical composition after etching and the surface topography was recorded under atomic force microscope (AFM) and scanning electron microscopy (SEM).ResultsThe reliability of resin to CAD/CAM porcelain bonding was decreased with the increase in HF etching time. The application of HF etching for 30 s decreased the Vickers hardness number (HV) significantly from 651.6 (control group) to 488.7 (group A). With the extension of etching time, the Vickers hardness number was further reduced to 430.1 (group B) and 305.7 (group C). However, the biaxial flexural strengths of these four groups were not statistically significant different (p>0.05). AFM revealed the porous structures on the porcelain surface at microscopic level.ConclusionsThe application of HF to etch the CAD/CAM feldspathic porcelain surface reduced the microhardness number. Etching with 5% hydrofluoric acid on dental porcelain for more than 1 min might impair the reliability of resin bonded porcelain veneer.     

Effects of different surface treatments of zirconia on the bond strength of self-adhesive resinous cement

Purpose: The aim of this study was to evaluate the effects of different zirconia surface treatments on the bond strength of two self-adhesive resinous cements (SARC).

Methods: Two hundred and eight cylindrical specimens were obtained from Y-TZP zirconia (half with diameter 3.2 mm and half with 4.8 mm). After sintering and polishing, specimens were divided into four groups (n = 26), according to surface treatment: Control (no treatment); Sandblasting (Al₂O₃ particles); Rocatec (Al₂O₃ particles, tribochemical silica coating and silane application); Laser (Nd: YAG laser: 20 Hz, 100 mJ, 0.2 J/cm²). The surface roughness (Ra) was evaluated after the surface treatments, and the groups were divided into two subgroups (n = 13), according to the SARC tested: RelyX U200 and Bifix SE. The 2.2-mm cylinders were bonded to 4.8-mm cylinders and stressed until failure under shear using a universal testing machine. Bond strength and Ra were analyzed using ANOVA, and Tukey’s test (α = 0.05).

Results: Surface treatment was significant (p < 0.0001), but cement type (p = 0.73) was not. Related to roughness, significant differences were found for the treatment type (p < 0.0001), with laser being the treatment with higher Ra values.

Conclusions: Nd:YAG laser produced a rougher surface and a higher bond strength compared with sandblasting, silicatization, and control groups.     

Effect of ceramic surface treatments on the bond strength of different composite resins

This study was aimed to observe the relationship between the different surface treatments and the bond strength of both composite based adhesive cement and zirconia ceramic. Thirty-two zirconia ceramic discs were fabricated by following the instructions of manufacturer (5 × 5 × 1.5 mm). Four subgroups were obtained from the specimens according to the specified surface treatments respectively: (a) C: control groups: no treatment; (b) SB: sandblasting with 125 μm aluminum oxide particles for 10 s; (c) SC: silica coating for 10 s; (d) Nd :YAG laser . The composite resin specimens Panavia F and Clearfil SA were introduced and polymerized to the treated bonding areas. Afterwards the specimens were stored in distilled water at 37 °C during 24 h, and the shear test was applied. The data were statistically analyzed by ANOVA and Duncan tests. The bond strength was stated significantly higher in silica coating/Panavia F group (23.35 MPa). The lowest bond strength was stated in control groups cemented with Clearfil SA (12.25 MPa). As a result it was determined that the bond strength has affected the both surface treatments and cement types (p < 0.001). The silica coating –treated zirconia ceramic recorded a significant increase in mean bond strength values.     

Could readily silanized silica particles substitute silica coating and silanization in conditioning zirconium dioxide for resin adhesion?

This study investigated the effect of particle types with different morphology and surface properties on the wettability and adhesion of resin cement to zirconia. Zirconia specimens (5 × 5 × 1 mm³) were wet polished. Specimens were randomly assigned to one of the following protocols (N = 36, n = 9 per group): Group CON: Control, no surface conditioning; Group AL: Chairside air-abrasion with aluminium trioxide (50 μm Al₂O₃) + silane; Group SIL: Chairside air-abrasion with alumina particles coated with silica (SIL) (30 μm SiO2, SilJet) + air-drying + silane; Group 4: Chairside air-abrasion with readily silanized silica particles (SILP) (30 μm SiO_2, SilJet Plus). Adhesive resin was applied and resin cement (Variolink II, Ivoclar) was bonded using polyethylene moulds and photo-polymerized and aged (thermocycling, 6.000 cycles, 5–55 °C). Shear bond test was performed using Universal Testing Machine (1 mm/min). Pretest failures were considered 0 MPa. Contact angle measurements were performed (n = 2/group, sessile drop with water). Data (MPa) were analyzed (ANOVA, Tukey’s (α = 0.05). Two-parameter Weibull distribution values including the Weibull modulus, scale (m) and shape (0), values were calculated. Contact angle measurements were in descending order as follows: SIL (74°)^c < CON (60°)^c < AL (51°)^b < SILP (40°)^a. Bond strength (MPa) with SIL (17.2 ± 4)^a and SILP (17.3 ± 1.9)^a demonstrated no significant difference (p > 0.05), being higher than AL (8.4 ± 1.5)^b and CON (0)^c (p < 0.05). Failure types were exclusively adhesive in all groups. Weibull distribution presented the highest shape (0) for SILP (10.8). SILP presented better wettability than AL. SILP provided similar bond strength to SIL. Readily silanized silica particles may substitute for conventional silica coating and silanization.     

Adhesion of orthodontic brackets to indirect laboratory-processed resin composite as a function of surface conditioning methods and artificial aging

This study compared the shear bond strength of orthodontic brackets to laboratory-processed indirect resin composites (IRC) after different surface conditioning methods and aging. Specimens made of IRC (Gradia Indirect, GC) (thickness: 2 mm; diameter: 10 mm) (N = 80) were randomly assigned to one of the following surface conditioning methods: C – Control: no treatment; AA – Air-abrasion (50 μm Al₂O₃ particles); DB – Diamond bur and HF – Etching with hydrofluoric acid (9.6%). After adhesive primer application (Transbond XT), orthodontic brackets were bonded to the conditioned IRC specimens using adhesive resin (Transbond XT). Following storage in artificial saliva for 24 h at 37 °C, the specimens were thermocycled (×1000, 5–55 °C). The IRC–bracket interface was loaded under shear in a Universal Testing Machine (0.5 mm/min). Failure types were classified using modified adhesive remnant index criteria. Data were analyzed using two-way ANOVA and Tukey`s HSD (α = 0.05). Surface conditioning method did not significantly affect the bond strength results (p = 0.2020), but aging significantly decreased the results (p = 0.04). Interaction terms were not significant (p = 0.775). In both non-aged and aged conditions, non-conditioned C group presented the lowest bond strength results (MPa) (p < 0.05). In non-aged conditions, surface conditioning with DB (8.03 ± 0.77) and HF (7.87 ± 0.64) showed significantly higher bond strength results compared to those of other groups (p < 0.05). Thermocycling significantly decreased the mean bond strength in all groups (2.24 ± 0.36–6.21 ± 0.59) (p < 0.05). The incidence of Score 5 (all adhesive resin remaining on the specimen) was the highest in HF group without (80%) and with aging (80%) followed by DB (40, 70%, respectively). C groups without and with aging showed exclusively Score 1 type (no adhesive resin on the specimen) of failures indicating the least reliable type of adhesion.     

Sintering,microstructure and hardness of Y-TZP- 64S bioglass ceramics

3 mol% yttria-partially stabilized zirconia (Y-TZP) powder and a sol-gel derived CaO- P₂O₅- SiO₂ (64S) bioglass, were used to produce Y-TZP- 64S slip cast compacts. The compacts with 10.5 and 19.9 vol% 64S were sintered at different temperatures up to 1500 °C using 5 and 10 °C/min heating/cooling rates. The densification behaviour, crystalline phase formation and zirconia grain growth were investigated as a function of sintering temperature and 64S glass content. Ca₃(PO₄)₂ along with SiO₂ as a major phase were obtained from thermal decomposition of the 64S glass at 950–1500 °C. Both 64S additions, 10.5 and 19.9 vol%, promoted the sintering process at a lower temperature with respect to Y-TZP (1500 °C); the SiO₂ phase markedly increased the Y-TZP solid state sintering rate at the intermediate stage. The rapidly cooling at 10 °C/min inhibited the t-m transformation of Y-TZP and markedly reduced that of Y-TZP- 64S at 1300–1500 °C. Sintered Y-TZP with 10.5 vol% 64S, nearly fully densified at 1300–1400 °C, was constituted by polygonal ZrSiO₄ particles and elongated Ca₂P₂O₇ particles uniformly distributed in the tetragonal zirconia fine grain matrix. This ceramic exhibited similar hardness to that of Y-TZP sintered at 1500 °C; the in situ formation of calcium phosphate will have the potential to improve the Y-TZP biological properties without significantly affecting its hardness.     

Microtensile bond strength testing of resin cements

To investigate the microtensile bond strength (μTBS) and failure mode of resin cements bonded to ceramic blocks following various surface treatments.Seventy-two Ceramco II (Ceramco lnc., Burlington, NJ) ceramic discs 10 mm in diameter and 4 mm thick were prepared. The ceramic specimens received 8 different surface conditions treatments before the application of resin cement. These surface treatments were sanding with 600-grit silicon carbide paper, microetching with aluminum oxide, sanding followed by silane application, microetching followed by silane application, hydrofluoric acid etching, hydrofluoric acid etching followed by silane application, application of adhesive resin, and combination of the previous two treatments (HF+S+Adh). Seventy-two extracted molars were ground flat at 90° to the long axis of the tooth until a sufficient circular area of dentin was exposed (at least 5 mm in diameter). Three resin cements were applied to these surfaces. After 24 h storage at 37 °C, the non-trimming version of μTBS test was used to produce 1 mm² microbars. The microbars were subjected to a tensile load using a modified testing device.Data were analyzed with 2-way analysis of variance. The interaction between the substrate surface treatment and cement type is significant (p<0.001).The results of this in vitro study suggest that when the tested ceramic restoration is cemented with a resin cement system, the ceramic should be etched with hydrofluoric acid, silane and adhesive should be applied prior to cementation. The results also suggest that an auto- or light-polymerizing cement should be considered instead of a dual-polymerizing cement.     

Bond strength of veneering porcelain to zirconia after different surface treatments

Aim: The aim of this study was to evaluate the effect of various surface treatments on the bond strength of veneering feldspathic porcelain to zirconia. Methods: Fifty yttria-stabilized tetragonal zirconia polycrystalline specimens were divided into five groups (n = 10) according to various surface treatments. The groups were as follows: Group 1: control group with liner application and no further surface treatment; Group 2: air-particle abrasion with 110 μm of alumina (Al₂O₃) particles; Group 3: grinding with a diamond disk; Group 4: Nd:YAG laser irradiation (the laser and the energy parameters were 10 Hz, and 2 W and 200 mJ, and the pulse duration (short pulse) range was up to 180 μs); Group 5: selective infiltration etching (SIE). After surface treatments, a liner application was performed for all surfaces according to the manufacturer’s instructions. Veneering porcelain was applied on zirconia surfaces using a Teflon mold. Shear bond strength was tested using a universal testing machine. The fractured surface morphologies were examined with scanning electron microscopy. The data were statistically analyzed using Mann–Whitney U and Kruskal–Wallis tests (α = .05). Results: The Megapascal values of the bonding groups were as follows: G1 = 8.62 ± 1.12, G2 = 13.87 ± 5.08, G3 = 12.31 ± 3.35, G4 = 17.32 ± 6.16, and G5 = 16.17 ± 4.55. Statistically significant differences were observed between the control group and the other groups (p < 0.05). Group 4 had the highest bond strength while G1 showed the lowest bond strength. No significant differences were found between the Nd:YAG, grinding, sandblasting, and SIE groups. Conclusion: Surface treatments had different effects on the shear bond strength of feldspathic porcelain to zirconia. Surface treatment techniques used in this study can be used on zirconia specimens prior to liner application to obtain an acceptable bond strength of veneering porcelain to zirconia. The effect of Nd:YAG laser irradiation and SIE techniques on bond strength of veneering ceramic to zirconia should be evaluated with further studies.     

Effects of different particle deposition parameters on adhesion of resin cement to zirconium dioxide and phase transformation

This study evaluated the effect of air-abrasion parameters such as particle size, distance, and time on adhesion of resin cement to zirconium dioxide (Y-TZP) and t→m phase transformation. Y-TZP blocks (N = 80) (In-Ceram YZ, Vita) (4 mm^3?×?4 mm^3?×?3 mm³) were assigned into eight groups (n = 10): air-abrasion with 30 μm (CoJet Sand, S30) and 110 μm (Rocatec-Plus, S110) silica-coated alumina particles, applied for either for 10–20 s (T = time), from a distance of 10–20 mm (D = distance), composing the following groups: S₃₀T₁₀D₁₀, S₃₀T₁₀D₂₀, S₃₀T₂₀D₁₀, S₃₀T₂₀D₂₀, S₁₁₀T₁₀D₁₀, S₁₁₀T₁₀D₂₀, S₁₁₀T₂₀D₁₀, and S₁₁₀T₂₀D₂₀. Resin composite (RelyX ARC) was bonded to Y-TZP blocks in polyethylene molds. The specimens were aged (10,000 thermal cycles and water storage for 90 days) prior to shear bond test. Failure types were analyzed under stereomicroscope and SEM, and phase transformation was calculated. Data (MPa) were analyzed using 3-way ANOVA and Tukey’s tests. Air-abrasion with 110 μm silica particles (10.96) presented significantly higher bond strength (p = 0.0149) compared to 30 μm (8.96). Time (p = 0.403) and distance (p = 0.179) parameters did not affect the results significantly. Air-abrasion with 110 μm particles (12.3) promoted higher bond strength than that of 30 μm (6.4) when applied for 10 s from a distance of 10 mm (Tukey’s). Failure types were predominantly adhesive. Phase transformation ranged between 30.3 and 35.9% for 30 μm particles and 23.8–43.7% for 110 μm particles. While the size of silica-coated alumina particles were more relevant parameter for resin cement adhesion to Y-TZP, time (up to 20 s) and distance (up to 20 mm) appear to be less pertinent.