Papers by Ricardo Armini Caldas
The aim of this study was to access the biomechanical behavior of teeth without remaining coronal... more The aim of this study was to access the biomechanical behavior of teeth without remaining coronal structure when restored with posts of different materials and configurations. Fifty bovine teeth (n = 10 per group) with standard dimensions were restored as follows: cast post and core (CPC), prefabricated metallic post (PFM), parallel glass-fiber post (P-FP), conical glass-fiber post (C-FP) or composite core (no post, CC). The survival rate during thermomechanical challenging (TC), the fracture strength (FS), and failure pattern (FP) were evaluated. Finite element models were realized to evaluate the stress distribution with a 100 N load. All post-containing teeth survived TC, while CC had 30% of failures. CPC and C-FP had the higher fracture strength, but a high number of irreparable fractures (60%), such as PFM (70%). Von Mises analysis has shown the maximum stresses into the canal in groups restored with metallic posts, while glass-fiber posts and CC presented the maximum stresses at load contact point in the crown. CPC led to higher modified von Mises (mvM) stress in the cervical third of dentin. However , mvM values did not reach the dentin fracture limit for any group. Analysis of maximal contact pressure has shown better stress distribution along with the dentin interface in post-containing groups, especially for CPC.
The study verified the bond strength in simulated dental restorations of silorane-or methacrylate... more The study verified the bond strength in simulated dental restorations of silorane-or methacrylate-based composites repaired with methacrylate-based composite. Methacrylate-(P60) or silorane-based (P90) composites were used associated with adhesive (Adper Single Bond 2). Twenty-four hemi-hourglass-shaped samples were repaired with each composite (n=12). Samples were divided according to groups: G1= P60 + Adper Single Bond 2+ P60; G2= P60 + Adper Single Bond 2 + P60 + thermocycling; G3= P90 + Adper Single Bond 2 + P60; and G4= P90 + Adper Single Bond 2 + P60 + thermocycling. G1 and G3 were submitted to tensile test 24 h after repair procedure, and G2 and G4 after submitted to 5,000 thermocycles at 5 and 55 °C for 30 s in each bath. Tensile bond strength test was accomplished in an universal testing machine at crosshead speed of 0.5 mm/min. Data (MPa) were analyzed by two-way ANOVA and Tukey's test (5%). Sample failure pattern (adhesive, cohesive in resin or mixed) was evaluated by stereomicroscope at 30× and images were obtained in SEM. Bond strength values of methacrylate-based composite samples repaired with methacrylate-based composite (G1 and G2) were greater than for silorane-based samples (G3 and G4). Thermocycling decreased the bond strength values for both composites. All groups showed predominance of adhesive failures and no cohesive failure in composite resin was observed. In conclusion, higher bond strength values were observed in methacrylate-based resin samples and greater percentage of adhesive failures in silorane-based resin samples, both composites repaired with methacrylate-based resin.
Adaptation at the implant/abutment interface is important to the long-term success of prosthetic ... more Adaptation at the implant/abutment interface is important to the long-term success of prosthetic rehabilitations. The aim of this study was to evaluate the adaptation of overdenture bar frameworks casted with different materials and the stress distribution of ill-fitted frameworks placement through 3-D finite element analysis (FEA). Thirty overdenture bar frameworks (n ¼ 10) were casted in different materials (Co–Cr, Ni–Cr, Ti). Vertical misfit of both abutments was examined using a single screw test and, after both screws were tightened, using a scanning electron microscope (SEM). The misfit values of each group were used to construct 3-D models, and a displacement with the same extent observed in SEM was applied to the non-tightened abutment to simulate the effect of prosthetic tightening. von Mises stress for prosthetic components, and the maximum principal stress and microstrain for bone tissue were evaluated. The misfit in the non-tightened abutment during the single screw test ranged from 145 to 211 mm. Different bar framework materials did not present significant differences in regard to adaptation. An increase in the misfit values in the other abutment was observed after the final settlement of the bars in Ni–Cr and Ti frameworks. The stress values on prosthetic screw and implant were not influenced by the bar framework material. However, Ti caused lower stress in the bar framework itself and strain in the bone tissue. The bar framework material does not affect the implant/ abutment adaptation. Titanium frameworks presented the best behavior for the bar framework itself and bone tissue compared to the other materials.
International Journal of Morphology, 2011
aperture morfometry and nasal bones morphology in Brazilian population by postero-anterior Caldwe... more aperture morfometry and nasal bones morphology in Brazilian population by postero-anterior Caldwell radiographys. Int. J. Morphol., 29(2):393-398, 2011.
Journal of Conservative Dentistry, 2015
The aim of this study was to evaluate the tensile bond strength (TBS) of repairs in recent fillin... more The aim of this study was to evaluate the tensile bond strength (TBS) of repairs in recent fillings of methacrylate- (MBC) or silorane-based composites (SBC) subsequent to different surface treatments. Fifty slabs of Filtek P60 (3M ESPE, St Paul, USA) and Filtek P90 (3M ESPE) were stored for 10 days in distilled water at 37°C. The surface of adhesion was abraded with a 600-grit silicone paper and repaired using each respective composite: G1, no treatment (control); G2, application of adhesive; G3, application of silane and adhesive; G4, sandblasting (Al2O3) and adhesive; and G5, sandblasting (Al2O3), silane, and adhesive. Further 10 slabs of each composite were also evaluated for cohesive strength (G6). After 30 days immersion in distilled water at 37°C, the TBS was determined. TBS results were higher for MBC than for SBC (P = 0.00012). The experimental groups were similar for SBC and the TBS was 27% of its cohesive strength. For P60, sandblasting significantly improved the TBS compared to other groups. With MBC, G4 and G5, the TBS was approximately 47% of its cohesive strength. Sandblasting (Al2O3) improves the repair-strength of MBC, whilst for the SBC all treatments succeed. MBC presents higher repair strength than SBC.
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Papers by Ricardo Armini Caldas