Fernando Eidi Takahashi

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.

Effect of Sodium Ascorbate and the Time Lapse before Cementation after Internal Bleaching on Bond Strength between Dentin and Ceramic

PURPOSE To evaluate the effects of the elapsed time (ET) after nonvital bleaching (NVB) and sodium ascorbate application (10%) (SAA) on the shear bond strength of dentin to ceramic. MATERIALS AND METHODS Bovine incisors were selected, internally bleached (35% carbamide peroxide) for 9 days and submitted to the following treatments (n = 10): G1, G2, G3-luting after 1, 7, and 14 days; G4, G5, and G6-luting after SAA, 1, 7, and 14 days, respectively. G7 and G8 were not bleached: G7-luting 24 hours after access cavity sealing; G8-luting 24 hours after access cavity sealing after SAA. After NVB, the vestibular dentin was exposed and flattened. The SAA was applied to the dentin (G4, G5, G6, G8) for 10 minutes, and it was then washed and dried. The dentin was etched (37% phosphoric acid), and an adhesive system (Single Bond 2) was applied. Feldspathic ceramic discs (VM7; 4-mm diameter, 3-mm thick) were luted with a dual-resin agent (RelyX ARC, 3M ESPE Dental Products, St. Paul, MN). After 24 hours, specimens were submitted to shear test on a universal testing machine. The data (MPa) were submitted to ANOVA and Dunnets test (5%). RESULTS The means (+/- SD) obtained were (MPa): G1 (14 +/- 4.5), G2 (14.6 +/- 3.1), G3 (14 +/- 3.7), G4 (15.5 +/- 4.6), G5 (19.87 +/- 4.5), G6 (16.5 +/- 3.7), G7 (22.8 +/- 6.2), and G8 (18.9 +/- 5.4). SAA had a significant effect on bond strength (p= 0.0054). The effect of ET was not significant (p= 0.1519). G5 and G6 presented higher values than the other bleached groups (p < 0.05) and similar to G7 and G8 (p > 0.05). CONCLUSIONS After NVB, adhesive luting to dentin is recommended after 7 days if sodium ascorbate has been applied prior to dentin hybridization.

The influence of cutting speed and cutting initiation location in specimen preparation for the microtensile bond strength test.

PURPOSE This study evaluated the effect of cutting initiation location and cutting speed on the bond strength between resin cement and feldspathic ceramic. MATERIALS AND METHODS Thirty-six blocks (6.4 x 6.4 x 4.8 mm) of ceramic (Vita VM7) were produced. The ceramic surfaces were etched with 10% hydrofluoric acid gel for 60 s and then silanized. Each ceramic block was placed in a silicon mold with the treated surface exposed. A resin cement (Variolink II) was injected into the mold over the treated surface and polymerized. The resin cement-ceramic blocks were divided into two groups according to experimental conditions: a) cutting initiation location - resin cement, ceramic and interface; and b) cutting speed - 10,000, 15,000, and 20,000 rpm. The specimens were sectioned to achieve non-trimmed bar specimens. The microtensile test was performed in a universal testing machine (1 mm/min). The failure modes were examined using an optical light microscope and SEM. Bond strength results were analyzed using one-way ANOVA and Tukeys test (α = 0.05). RESULTS Significant influences of cutting speed and initiation location on bond strength (p < 0.05) were observed. The highest mean was achieved for specimens cut at 15,000 rpm at the interface (15.12 ± 5.36 MPa). The lowest means were obtained for specimens cut at the highest cutting speed in resin cement (8.50 ± 3.27 MPa), and cut at the lowest cutting speed in ceramic (8.60 ± 2.65 MPa). All groups showed mainly mixed failure (75% to 100%). CONCLUSION The cutting speed and initiation location are important factors that should be considered during specimen preparation for microtensile bond strength testing, as both may influence the bond strength results.

Stress distribution around osseointegrated implants with different internal-cone connections: photoelastic and finite element analysis.

The goal of this study was to evaluate the distribution of stresses generated around implants with different internal-cone abutments by photoelastic (PA) and finite element analysis (FEA). For FEA, implant and abutments with different internal-cone connections (H- hexagonal and S- solid) were scanned, 3D meshes were modeled and objects were loaded with computer software. Trabecular and cortical bones and photoelastic resin blocks were simulated. The PA was performed with photoelastic resin blocks where implants were included and different abutments were bolted. Specimens were observed in the circular polariscope with the application device attached, where loads were applied on same conditions as FEA. FEA images showed very similar stress distribution between two models with different abutments. Differences were observed between stress distribution in bone and resin blocks; PA images resembled those obtained on resin block FEA. PA images were also quantitatively analyzed by comparing the values assigned to fringes. It was observed that S abutment distributes loads more evenly to bone adjacent to an implant when compared to H abutment, for both analysis methods used. It was observed that the PA has generated very similar results to those obtained in FEA with the resin block.

Comparison of Physicochemical Surface Conditioning Methods for Adhesion of bis-GMA Resin Cement to Particulate Filler Composite and Surface Characterization

This study compared the effect of physicochemical surface conditioning methods on the adhesion of bis-GMA-based resin cement to particulate filler composite (PFC) used for indirect dental restorations. PFC blocks (N block = 54, n block = 9 per group) were polymerized and randomly subjected to one of the following surface conditioning methods: a) No conditioning (Control-C), b) Hydrofluoric acid (HF)etching for 60 s (AE60), c) HF for 90 s (AE90), d) HF for 120 s (AE120), e) HF for 180 s (AE180), and f) air-abrasion with 30 µm silica-coated alumina particles (AB). The conditioned surfaces were silanized with an MPS silane, and an adhesive resin was applied. Resin composite blocks were bonded to PFC using resin cement and photo-polymerized. PFC–cement–resin composite blocks were cut under coolant water to obtain bar specimens (1 mm × 0.8 mm). Microtensile bond strength test (μTBS)was performed in a universal testing machine (1 mm/min). After debonding, failure modes were classified using stereomicroscopy. Surface characterization was performed on a set of separate specimen surfaces using Scanning Electron Microscopy (SEM), X-Ray Dispersive Spectroscopy (XDS), X-Ray Photoelectron Spectroscopy (XPS), and Fourier Transform-Raman Spectroscopy (FT-RS). Mean μTBS (MPa) of C (35.6 ± 4.9) was significantly lower than those of other groups (40.2 ± 5.6–47.4 ± 6.1) (p < 0.05). The highest μTBS was obtained in Group AB (47.4 ± 6.1). Prolonged duration of HF etching increased the results (AE180: 41.9 ± 7), but was not significantly different than that of AB (p > 0.05). Failure types were predominantly cohesive in PFC (34 out of 54) followed by cohesive failure in the cement (16 out of 54). Degree of conversion (DC) of the PFC was 63 ± 10%. SEM analysis showed increased irregularities on PFC surfaces with the increased etching time. Chemical surface analyses with XPS and FT-RS indicated 11–70% silane on the PFC surfaces that contributed to improved bond strength compared to Group C that presented 5% silane, which seemed to be a threshold. Group AB displayed 83% SiO2 and 17% silane on the surfaces.

Estabilidade de cor de uma resina composta indireta

A cor das resinas compostas indiretas e um dos mais importantes fatores no sucesso do tratamento protetico. Com este material a estabilidade de cor e aspecto preponderante na longevidade deste trabalho. A proposta deste estudo foi avaliar a estabilidade de cor de resina composta indireta (Resilab Master, Wilcos – Brasil) atraves de um colorimetro digital. Foram confeccionados 32 corpos-de-prova (CP). Realizou-se o registro inicial da cor de cada CP, atraves de um colorimetro digital, que foram distribuidos em 4 grupos (n=8) e imersos em diferentes solucoes. Grupo 1 (controle): agua destilada/estufa; Grupo 2: agua destilada/termociclagem; Grupo 3 : suco de laranja/termociclagem e Grupo 4: cafe/termociclagem. Apos termociclagem e imersao em estufa (tempo total aproximado de 60 horas), as amostras foram enxaguadas e o registro final da cor foi obtido. Os dados foram submetidos a analise estatistica (Teste de Dunnet – p<0,005). Os resultados mostraram que os valores de ΔE (diferenca de cor) e desvio padrao dos grupos foram: G1: 2,35±0,84; G2: 2,97±1,21; G3: 8,33±5,87; G4: 22,38±5,33. Foi observado que os grupos 3 e 4 diferiram estatisticamente do grupo 1, exceto o grupo 2 que nao foi estatisticamente significante. Baseado nos resultados, conclui-se que a termociclagem contribui para uma alteracao de cor da resina composta indireta e a solucao de cafe mancha mais do que o suco de laranja.