Cristiane Fonseca de Carvalho

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.

Effect of Surface Treatment of Yttria Stabilized Zirconia for Dental Prostheses

When it comes to providing reliable adhesion of low silica content alumina ceramic, hydrofluoric acid etching along with silanization has not shown sufficient efficacy because the microstructure of high-alumina content ceramics is unable to degrade them. The objective of this study was to analyze the effect of surface sandblasting of zirconia-based ceramic stabilized by yttria as used in dental prostheses, using a SEM and roughness average. The samples were divided in control, no surface treatment; Al2O3 sandblasting; Al2O3 sandblasting and Al2O3 + SIC particles 110 µm average sized; Al2O3 sandblasting and Al2O3 + SIC particles 110 µm average sized milled for 2 hours; Al2O3 sandblasting and Al2O3 + SIC particles 110 µm average sized milled for 6 hours. The Al2O3 sandblasting and the 2-hour milled Al2O3 + SIC particles showed better results and better characterization of roughness in SEM with the silica deposition on the samples surface.

Evaluation of the Influence of the Silane Drying Temperature on the Feldspar and Zirconia-Based Ceramics Surfaces

Ceramics are widespread used in restorative dentistry, mainly due to their aesthetics features. However, adequante bond strenght of this type on restoration to tooth structure spawned several investigations which aim to develop a clinical protocol for ceramic surface treatment. The objective of this study was to evaluate the influence of air temperature on the drying process of silane agent and the adhesion of feldspar and yttrium stabilized zirconia. They were divided into three groups (n=10): control; room temperature dried silane; and silane drying at 70º C. Then, composite resin cylinders were bonded to the samples and taken to a shear test. The results showed that air temperature rise, in silane drying, improved bonding resistance in Y-TZP ceramics, nevertheless in feldspatic ceramics, the bonding resistance was not altered.

Metallographic characterisation of 2205 duplex stainless steel brazed joint

Duplex and superduplex stainless steels have a wide industrial application when one requires high resistance to corrosion and mechanical properties higher than those of conventional stainless steels1, 2. These properties are obtained by way of chemical compositions involving elements such as Cr, Ni, Mo, W, Cu and nitrogen, which is an alloy element in a gaseous form in nature and with a characteristic microstructure composed of approximately 50% ferrite and 50% austenite. When these materials are subjected to heating and cooling, whether during welding, brazing or thermal treatments, its properties can be altered either by modifying the chemical composition or be changing its microstructure. In the case o f 2205 dup lex s t a in l e s s s t ee l (UNS S31803), two temperature ranges should be avoided.3,4 The first of these are temperatures much higher than the treatment temperature in which the balanced microstructure was obtained, which is between 1050oC and 1100oC. Above this temperature range, the austenite starts to dissolve and depending on the cooling rate can form chromium nitrate on cooling. The second range is at lower temperatures, between 700 and 850oC. In this case, precipitation of the sigma phase or other intermetallic phases may occur. The brazing of duplex stainless steels has barely been studied. This manufacturing process, if feasible, may further extend the use of these materials. As such, it is important to understand its brazability. By brazability one refers to the facility to braze a joint of one material (or dissimilar materials), maintaining its original properties practically unaltered. Generically, material brazability involves different aspects such as: the choice of ideal gap; the filler metal which fills the joint using capillarity; the type of atmosphere or flow; the temperature and brazing process time as well as potential alterations which may occur in the base metal during brazing. Figure 1 demonstrates schematically the variation in mechanical resistance of the brazed joint in relation to the gap for a given brazing condition. Analysing Figure 1, one observes there are two regions in which gaps are not ideal (regions 1 and 3) and another in which the gap is ideal (region 2). In region 1 of the figure, the mechanical resistance of the joint drops due to the lack of filling and other defects generated in the brazed joint. In region 3, the drop in resistance is associated with two factors: one mechanical6 and the other microstructural. The mechanical factor is related to a drop in joint resistance due to the increased gap. The joint behaves as if it were composed merely of the filler metal. The microstructural factor is associated with the presence of intermetallic phases in the joint which may reduce the resistance of the same when its distribution is continuous. Region 2, the ideal gap region of the joint demonstrates the greatest mechanical resistance because the region which will be deformed is ‘hardened’ by the mechanical effect of the restriction of the deformation of the joint by the base metal6. In this case, the mechanical resistance of the brazed joint, even though the filler is not a very resistant material, is similar to the base metal value. In this region the microstructure is practically absent in the intermetallic phases. To study brazability one can employ a variety of tests such as: sessile drop test, capillary ascension test, wedge test and variants7-13. In all these tests, the focus was exclusively on the properties of the liquid filler metal and its interaction with the base metal. Figure 2 schematically shows some of these tests. Figure 2a shows the sessile drop test which consists of a liquid drop on a solid substrate under the action Metallographic characterisation of 2205 duplex stainless steel brazed joint