José Renato Cavalcanti de Queiroz

Effect of multiple firing and silica deposition on the zirconia-porcelain interfacial bond strength

OBJECTIVES To test the hypothesis that multiple firing and silica deposition on the zirconia surface influence the bond strength to porcelain. MATERIALS AND METHODS Specimens were cut from yttria-stabilized zirconia blocks and sintered. Half of the specimens (group S) were silica coated (physical vapor deposition (PVD)) via reactive magnetron sputtering before porcelain veneering. The remaining specimens (group N) had no treatment before veneering. The contact angle before and after silica deposition was measured. Porcelain was applied on all specimens and submitted to two (N2 and S2) or three firing cycles (N3 and S3). The resulting porcelain-zirconia blocks were sectioned to obtain bar-shaped specimens with 1mm(2) of cross-sectional area. Specimens were attached to a universal testing machine and tested in tension until fracture. Fractured surfaces were examined using optical microscopy. Data were statistically analyzed using two-way ANOVA, Tukeys test (α=0.05) and Weibull analysis. RESULTS Specimens submitted to three firing cycles (N3 and S3) showed higher mean bond strength values than specimens fired twice (N2 and S2). Mean contact angle was lower for specimens with silica layer, but it had no effect on bond strength. Most fractures initiated at porcelain-zirconia interface and propagated through the porcelain. SIGNIFICANCE The molecular deposition of silica on the zirconia surface had no influence on bond strength to porcelain, while the number of porcelain firing cycles significantly affected the bond strength of the ceramic system, partially accepting the study hypothesis. Yet, the Weibull modulus values of S groups were significantly greater than the m values of N groups.

Surface characterization of feldspathic ceramic using ATR FT-IR and ellipsometry after various silanization protocols.

OBJECTIVES This study characterized the feldspathic ceramic surfaces after various silanization protocols. METHODS Ceramic bars (2 mm × 4 mm × 10 mm) (N = 18) of feldpathic ceramic (VM7, VITA Zahnfabrik) were manufactured and finished. Before silane application, the specimens were ultrasonically cleaned in distilled water for 10 min. The ceramic specimens were randomly divided into nine groups (N = 2 per group) and were treated with different silane protocols. MPS silane (ESPE-Sil, 3M ESPE) was applied to all specimens and left to react at 20°C for 2 min (G20). After drying, the specimens were subjected to heat treatment in an oven at 38°C (G38), 79°C (G79) or 100°C (G100) for 1 min. Half of the specimens of each group were rinsed with water at 80°C for 15s (G20B, G38B, G79B, G100B). The control group (GC) received no silane. Attenuated total reflection infrared Fourier transform analysis (ATR FT-IR) was performed using a spectrometer. Thickness of silane layer was measured using a spectroscopic ellipsometer working in the λ = 632.8 nm (He-Ne laser) at 70° incidence angle. Surface roughness was evaluated using an optical profilometer. Specimens were further analyzed under the Scanning Electron Microscopy (SEM) to observe the topographic patterns. RESULTS ATR FT-IR analysis showed changes in Si-O peaks with enlarged bands around 940 cm(-1). Ellipsometry measurements showed that all post-heat treatment actions reduced the silane film thickness (30.8-33.5 nm) compared to G20 (40 nm). The groups submitted to rinsing in hot water (B groups) showed thinner silane films (9.8-14.4 nm) than those of their corresponding groups (without washing) (30.8-40 nm). Profilometer analysis showed that heat treatments (Ra ≈ 0.10-0.19 μm; Rq ≈ 0.15-0.26 μm) provided a smoother surface than the control group (Ra ≈ 0.48 μm; Rq ≈ 0.65 μm). Similar patterns were also observed in SEM images. SIGNIFICANCE Heat treatment after MPS silane application improved the silane layer network. Rinsing with boiling water eliminated the outmost unreacted regions of the silane yielding to thinner film thicknesses.

Silica-based Nano-coating on Zirconia Surfaces Using Reactive Magnetron Sputtering: Effect on Chemical Adhesion of Resin Cements

PURPOSE To compare the effect of silica (Si)-based nano-coating deposited by reactive magnetron sputtering (RMP) with that of conventional surface conditioning using metal/zirconia primer alone or after air-particle abrasion on the adhesion of resin cements to zirconia ceramic. MATERIALS AND METHODS Two hundred forty zirconia ceramic blocks (Cercon) were sintered, finished with 1200- grit SiC paper under water cooling, and cleaned ultrasonically in distilled water for 10 min. The blocks (4.5 mm x 3.5 mm x 4.5 mm) were randomly divided into 24 groups (n = 10) according to 3 testing parameters: a) resin cements (Multilink, Panavia F, RelyX U100), b) surface conditioning (no conditioning as control group; Metal/Zirconia Primer; air abrasion + Metal/Zirconia Primer; Si-based nanofilm + Monobond s); c) aging (no aging vs thermocycling at 5°C to 55°C, 6000 cycles). The nanofilm was deposited by direct current using argon/oxygen plasma (8:1 in flux) on the zirconia surface. Resin cements were bonded to zirconia surfaces using polyethylene molds. The shear bond strength (SBS) test was performed using a universal testing machine (1 mm/min), and after debonding, the substrate and adherent surfaces were analyzed using optical and scanning electron microscopes to categorize the failure types. The data were statistically evaluated using 3-way ANOVA and Tukeys test (5%). RESULTS Resin cement type (p < 0.05), surface conditioning method (p < 0.05), and aging condition (p < 0.05) had a significant effect on the bond strength results. Interactions were also significant (p < 0.05). In the nonaged condition, while control groups presented the lowest results with all cements (0 to 5.2 MPa), the airabraded group in combination with RelyX U100 resulted in the highest SBS (21.8 ± 6.7 MPa). After aging, the SBS results decreased in the air-abraded groups for all cements (4.54 to 9.44 MPa) and showed no statistical significance compared to the Si-based nanocoated groups (4.24 to 6.44 MPa). After air-abrasion and primer application, only Panavia F and RelyX U100 cements showed exclusively mixed failures, but after nanofilm coating and silanization, all cements showed exclusively mixed failures with and without aging. CONCLUSION Chemical adhesion of the resin cements tested to zirconia was similar after silica-based nanofilm deposition and air abrasion followed by primer application.

Effect of Diamond-Like Carbon Thin Film Coated Acrylic Resin on Candida albicans Biofilm Formation

PURPOSE The purpose of this study was to evaluate the effect of diamond-like carbon thin films doped and undoped with silver nanoparticles coating poly(methyl methacrylate) (PMMA) on Candida albicans biofilm formation. The control of biofilm formation is important to prevent oral diseases in denture users. MATERIALS AND METHODS Forty-five PMMA disks were obtained, finished, cleaned in an ultrasonic bath, and divided into three groups: Gc, no surface coating (control group); Gdlc, coated with diamond-like carbon film; and Gag, coated with diamond-like carbon film doped with silver nanoparticles. The films were deposited using a reactive magnetron sputtering system (physical vapor deposition process). The specimens were characterized by optical profilometry, atomic force microscopy, and Rutherford backscattering spectroscopy analyses that determined differences in chemical composition and morphological structure. Following sterilization of the specimens by γ-ray irradiation, C. albicans (ATCC 18804) biofilms were formed by immersion in 2 ml of Sabouraud dextrose broth inoculated with a standardized fungal suspension. After 24 hours, the number of colony forming units (cfu) per specimen was counted. Data concerning biofilm formation were analyzed using ANOVA and the Tukey test (p < 0.05). RESULTS C. albicans biofilm formation was significantly influenced by the films (p < 0.00001), reducing the number of cfu, while not affecting the roughness parameters (p > 0.05). The Tukey test showed no significant difference between Gdlc and Gag. Films deposited were extremely thin (∼50 nm). The silver particles presented a diameter between 60 and 120 nm and regular distribution throughout the film surface (to Gag). CONCLUSION Diamond-like carbon films, doped or undoped with silver nanoparticles, coating the base of PMMA-based dentures could be an alternative procedure for preventing candidosis in denture users.

Does the Ultrasonic Cleaning Medium Affect the Adhesion of Resin Cement to Feldspathic Ceramic

PURPOSE To evaluate the effect of different cleaning media on the adhesion of resin cement to feldspathic ceramic after etching. MATERIALS AND METHODS The cementation surfaces of ceramic blocks (N = 20, n = 5 per group) were etched with 10% hydrofluoric acid (HF) gel for 20 s and rinsed for 60 s. They were then randomly assigned to 4 groups: G1: air-water spray+drying (control); G2: ultrasonic cleaning in distilled water for 4 min+drying; G3: ultrasonic cleaning in 99.5% acetone for 4 min+drying; G4: ultrasonic cleaning in 70% alcohol for 4 min+drying. The ceramic blocks were silanized and cemented (RelyX ARC) to the composite blocks. Subsequently, the microtensile bond strength test (µTBS) was performed. In addition, EDS analysis was made to assess the elemental composition of the conditioned and cleaned ceramic surfaces. RESULTS A significantly higher mean µTBS was obtained when specimens had been ultrasonically cleaned in distilled water (G2: 18.8 ± 0.4 MPa) (p < 0.05) compared to other groups (G1: 16.6 ± 0.5; G3: 16.1 ± 0.9; G4: 15.8 ± 1.4) (one-way ANOVA). EDS analysis indicated the presence of F- only in G1. Dissolved precipitates after HF etching were removed by ultrasonic cleaning. CONCLUSION Cleaning the HF-etched ceramic surface ultrasonically in distilled water is recommended, instead of rinsing it with air-water spray only.

Carbon film coating of abutment surfaces: effect on the abutment screw removal torque.

Purpose:To evaluate the effect of diamond-like carbon (DLC) coating of prefabricated implant abutment on screw removal torque (RT) before and after mechanical cycling (MC). Materials and Methods:Fifty-four abutments for external-hex implants were divided among 6 groups (n = 9): S, straight abutment (control); SC, straight coated abutment; SCy, straight abutment and MC; SCCy, straight coated abutment and MC; ACy, angled abutment and MC; and ACCy, angled coated abutment and MC. The abutments were attached to the implants by a titanium screw. RT values were measured and registered. Data (in Newton centimeter) were analyzed with analysis of variance and Dunnet test (&agr; = 0.05). Results:RT values were significantly affected by MC (P = 0.001) and the interaction between DLC coating and MC (P = 0.038). SCy and ACy showed the lowest RT values, statistically different from the control. The abutment coated groups had no statistical difference compared with the control. Scanning electron microscopy analysis showed DLC film with a thickness of 3 &mgr;m uniformly coating the hexagonal abutment. Conclusion:DLC film deposited on the abutment can be used as an alternative procedure to reduce abutment screw loosening.

Degree of chronic orofacial pain associated to the practice of musical instruments in orchestra's participants.

OBJECTIVE The practice of playing musical instruments can affect structures of the head, neck, mouth, and the masticatory system. The aim of this study was to obtain information regarding the prevalence of orofacial pain in musicians according to the type of instrument they play, by applying a specific questionnaire. MATERIALS AND METHODS One hundred and seventeen musicians of Sao Paulo states orchestras participated in this study. They answered an anamnesis questionnaire with 20 questions regarding their personal data, type of instrument played, hours of daily practice, and presence or absence of orofacial pain according to the Chronic Pain Grade Classification (CPGC). Musicians were divided into two groups in accordance with the risk of affecting TMJ: RG (risk group, including violin, viola, vocalist, trombone, tuba, clarinet and saxophone); CG (control group, other instruments). They received an informative brochure about the subject. Data obtained from the questionnaire were submitted to descriptive statistics, Pearsons correlation analysis and Z-test for difference between two proportions. RESULTS The participants were from 15 to 62 years old. Pain degree showed positive correlation for reported symptoms (P = 0.002) and hour/day practice (P = 0.030). Regarding the prevalence of pain degree, data were, for RG: Grade 0 (54.5%), Grade 1 (30.3%), and Grade ≥2 (15.1%). For CG, Grade 0 (84.4%), Grade 1 (8.9%), and Grade ≥2 (6.6%). Z-test showed positive difference between groups (P = 0.0001). CONCLUSION It was concluded that the musicians of risk group presented higher prevalence of orofacial pain than control (non-risk) group.

Heat treatment following surface silanization in rebonded tribochemical silica-coated ceramic brackets: shear bond strength analysis

OBJECTIVE This study aimed to evaluate the effects of heat treatment on the tribochemical silica coating and silane surface conditioning and the bond strength of rebonded alumina monocrystalline brackets. MATERIAL AND METHODS Sixty alumina monocrystalline brackets were randomly divided according to adhesive base surface treatments (n=20): Gc, no treatment (control); Gt, tribochemical silica coating + silane application; Gh, as per Gt + post-heat treatment (air flux at 100ºC for 60 s). Brackets were bonded to the enamel premolars surface with a light-polymerized resin and stored in distilled water at 37ºC for 100 days. Additionally, half the specimens of each group were thermocycled (6,000 cycles between 5-55ºC) (TC). The specimens were submitted to the shear bond strength (SBS) test using a universal testing machine (1 mm/min). Failure mode was assessed using optical and scanning electron microscopy (SEM), together with the surface roughness (Ra) of the resin cement in the bracket using interference microscopy (IM). 2-way ANOVA and the Tukey test were used to compare the data (p>0.05). RESULTS The strategies used to treat the bracket surface had an effect on the SBS results (p=0.0), but thermocycling did not (p=0.6974). Considering the SBS results (MPa), Gh-TC and Gc showed the highest values (27.59±6.4 and 27.18±2.9) and Gt-TC showed the lowest (8.45±6.7). For the Ra parameter, ANOVA revealed that the aging method had an effect (p=0.0157) but the surface treatments did not (p=0.458). For the thermocycled and non-thermocycled groups, Ra (µm) was 0.69±0.16 and 1.12±0.52, respectively. The most frequent failure mode exhibited was mixed failure involving the enamel-resin-bracket interfaces. CONCLUSION Regardless of the aging method, Gh promoted similar SBS results to Gc, suggesting that rebonded ceramic brackets are a more effective strategy.

Evaluation of Surface Roughness of Monolithic Zirconia after Using Different Polishing Kits

Objective: To evaluate the effect of different kits to polish monolithic zirconia on its surface roughness. Material and Methods: Five samples were fabricated using zirconia blocks. Each sintered block was divided into four areas of equal size and each area was subjected to a specific surface treatment according to the four groups of the study: GC: no surface treatment, GG: unidirectional grinding with high speed tapered bur under refrigeration, GP1: wear similar to GG followed by polishing with zirconia polishing kit Kenda at the same wear direction, and GP2: wear similar to GG followed by polishing with zirconia polishing kit Diacera at the same wear direction. Qualitative and quantitative analyses of ceramic topography and roughness were performed using a digital optical profilometer, and Roughness measurements were performed using two parameters (R a and R z : arithmetical mean of the absolute values of the surface departures and of the five highest peaks and valleys, respectively). Scanning electron micrographs of each ceramic surface were obtained to illustrate sample roughness. The means of each group were analyzed by 1-way ANOVA followed by Tukey’s test. Results: Morphological analysis showed that polishing kits provided the same pattern of a smooth surface. To statistical analysis, this study showed that different polishing kits influenced zirconia roughness for both Ra and Rz after surface wear ( p < 0.05) with both situations improved the surface roughness observed immediately after zirconia sintering. Conclusion: According to the results, both polish kits resulted in a surface texture within acceptable clinical parameters.

Dislodgement Resistance of Zirconia Copings Cemented onto Zirconia and Titanium Abutments

Purpose: To determine the effect of the cement type and abutment material on the tensile strength required to dislodge zirconia copings. Materials and Methods: Two experimental groups of abutments were prepared: (1) titanium abutments (n = 30) and (2) zirconia abutments (n = 30). Sixty zirconia copings (custom designed) were fabricated using 3-dimensional computer-assisted design to have a 6-mm projection above the abutment to accommodate a hole, through which a wire was inserted to attach the zirconia coping to a universal testing machine. Each abutment was placed onto an implant analog embedded in acrylic resin blocks to fit onto the universal testing machine. The zirconia copings were cemented onto the abutments with a provisional luting agent, zinc phosphate (ZP) cement, and adhesive resin cement, and after 5500 thermocycles, a tensile force was applied at a crosshead speed of 0.5 mm/min. The removal force was recorded for each specimen. Two-way analysis of variance (ANOVA) and 1-way ANOVA were used for the statistical analysis (P < 0.05). Results: The mean forces necessary to remove the zirconia copings from titanium abutments were 6.52, 83.09, and 251.18 N for temporary cement, ZP cement, and resin cement, respectively. For zirconia abutments, the required forces were 17.82, 116.41, and 248.72 N. Conclusions: The abutment material had no effect on retention, but the cement type affected the retention of the zirconia copings.