Tereza Cristina Favieri de Melo-Silva

Evaluation of Bonding Resistance after Surface Treatment of Two Glass-Ceramics Used in Dentistry

The goal of this study was to evaluate the bonding resistance of two dental ceramics. The samples, one of each type of ceramics, were split into 4 groups (n=4) separated from those from control group, the others were conditioned with 5% hydrofluoric acid, according to the times of 20, 40 and 60 seconds. Cylindrical pins of resin cement were applied in each sample. After a shearing test, the obtained results showed that experimental groups has given higher bonding strength values than the control groups for both ceramics. For the e.max ceramic, the highest values were observed with timings of 20 and 40 seconds and for the Suprinity ceramic the conditioning timings were insignificant. The authors concluded that the surface treatment with hydrofluoric acid improved the bonding strength for both ceramics; and the e.max ceramic showed higher bonding values than the Suprinity.

Evaluation of Load Parameters and Hold Time of a Vickers Ultra-Micro Hardness Tester for Measure of Hardness and Modulus of Elasticity of Dental Composites

The aim of this study was to standardize the parameters for testing the hardness and elastic modulus for dental composites. It used the equipment Dynamic Ultra Micro Hardness Tester DUH-211 / DUH-211S (Shimadzu) varying the load and the hold time. two composites were used with various inorganic particles that were embedded and sanded for the assay. one Vickers indenter was used being held nine rows with ten penetrations. For each composite loads were used (20, 50 and 100gf) and times (zero, five and ten seconds). The results showed that the effect of the load and the hold time had influence on the modulus and hardness values of the studied composites. The authors concluded that loads and hold larger team showed greater stability of hardness values and modulus of elasticity for the studied composites and these values for both hybrid composites as for nanoparticulate were dependent on load and time.

Analysis of the Effect of Cyclic Fatigue on the Flexural Strength of a Ceramoceramic System Used in Dental Prostheses

The aim of this study was to analyze the flexural strength of ceramics based on yttria-stabilized zirconia (YTZP) , used in the manufacture of dental prostheses infrastructure before and after aging with cyclic fatigue in moisture. The samples were made by pre-sintered blocks of ZirkonTransluzent (Zirkonzahn GMHB) from YTZP ceramics with and without feldspathic ceramic coating, divided into groups: G1 = YTZP control; G2 = YTZP aged; G3 = YTZP + feldspathic; G4 = YTZP + aged feldspathic. The samples were submitted to a three-point bending test with a speed of 0.5 mm / min. The mean values of the flexural strength values were G1 = 645 MPa (DP ± 124), G2 = 681 MPa (DP ± 129), G3 = 904Mpa (DP ± 157) and G4 = 954Mpa (DP ± 243). The values of groups G1 and G2; G3 and G4 were statistically similar, depending on the presence or absence of coating. Cyclic stresses did not affect the flexural strength of the material

Evaluation of Mechanical Properties of Composite Materials Used in Dentistry Varying the Inorganic Composition

The aim of this study was to determine the hardness and the elasticity modulus of the two composite resins base of BISGMA with different inorganic particles: a nanoparticulated with a ceramic withload, (Filtek Z350XT-3M) with and without thermal activation and a microhybrid with no ceramic load (Opallis-FGM). The samples were prepared and subjected to the tests of Vickers hardness (Shimadzu HMV) and acoustic excitation pulse (Sonelastic ®). The samples were divided into three groups: G1-Filtek Z350 XT; G2-Filtek Z350XT MO (subject to further polymerization microwave) and G3-Opallis. The results showed that the hardness of G2 was significantly higher than the groups G1 and G3. The elastic modulus was higher than the G2 to G1 and G3. One can conclude that the resins filled with inorganic ceramic filler showed higher hardness and elastic modulus. The thermal activation increased the hardness and the elasticity modulus of the resin with ceramic load.

Analysis of Flexural Strength of Ceramics Based on Zirconia Stabilized by Yttria with Ceramic Cover

The aim of this study was to analyze the flexural strength of ceramics based on yttria-stabilized zirconia ( Y-TZP) , used in the manufacture of dental prostheses infrastructure with different types of coating ceramics. The rectangular samples measuring 18mm x 4mm x 1.2 mm were divided into groups (n = 10): G1 = control Y-TZP, G2= Y-TZP + sintered feldspathic ceramic and G3= Y-TZP + pressable feldspathic ceramic and submitted to assay of three points with a speed of 0.5 mm / min. Compared to the control group (G1), the group that showed the greatest resistance to bending was the G2, however, not significant relative to G3. No group provided the infrastructure fracture. It was observed by means of the methodology applied to all groups are suitable for use in dental prostheses.

Evaluation of Morphology and Roughness of the Surface of a Ceramic Based on Lithium Disilicate, after Conditioning with Acid Hydrofluoric the 5% and 10%

The aim of the study was to evaluate the difference in the surface of dental ceramics, the basis of lithium disilicate, varying the concentration and time of application of the acid. Samples of IPS e.max Press (Ivoclar) were divided into: G1-control; G2 hydrofluoric acid 10% - 20 sec; G3 hydrofluoric acid 10% - 40 sec; G4 hydrofluoric acid 5% - 20 sec G5 and hydrofluoric acid 5% - 40 sec. The samples were analyzed under SEM (Carl Zeiss) confocal microscope and (Carl Zeiss). The qualitative morphologic analysis showed that 40 seconds of conditioning promoted the dissolution of the vitreous component and the ceramic crystal display for the two concentrations. Hydrofluoric acid 10% showed higher values of roughness. One can conclude that conditioning for 40 seconds is more effective than the 20 seconds for the two concentrations hydrofluoric acid and 10% promoted a higher surface roughness in the ceramic.

Analysis of the Y-TZP Ceramic Substucture in Blasting with Aluminum Oxide before and after Sintering

The objective of this study was to evaluate the microstructure of a ceramic based on yttria stabilized zirconia (Y-TZP) in blasting with aluminum oxide and its effect on the sintering. 25 pre-sintered Y-TZP blocks were obtained. Ten samples were blasted with alumina, and then all samples were sintered and divided into the groups: Control-no treatment; alumina G1-blasted with alumina and sintered; alumina and Rocatec G1-blasted, sintered, and Rocatec; alumina G2-sintered, alumina blasting; alumina and Rocatec G2-sintering, alumina blasting, and Rocatec. The samples were evaluated by a scanning electron microscopy. The qualitative analysis showed that the treated samples had an increase in the surface texture and that group 1– alumina and Rocatec– presented the silica incorporation to be regular and homogeneous. It was concluded that the treatment of pre-sintered surfaces is a good alternative in the bonding strength between the Y-TZP and the resin cements.

Micromorfologia da interface da união sistema restaurador-dentina decídua, em função do sistema adesivo e do instrumento cortante rotatório

Objective: This study in vitro evaluated the micromorphology of the resin-dentin interface in primary teeth, using different rotatory instruments and adhes...