<p><span style="font-size: medium;">The objective of this study was to evaluate the influence of different speeds using the piston device in the shear bond strength. 48 cylinders of composed resin had been confectioned (Solidex),and were divided randomly in four groups (n=12).</span><span style="font-size: medium;"> </span><span style="font-size: medium;">The specimens were adapted to the device for the</span><span style="font-size: medium;"> </span><span style="font-size: medium;">shear bond strenth test and were taken to an universal testing machine with a load cell of 1000Kg. The test were carried through with four different speeds: group A: 0,5; group B: 1,0; group C: 1,5 and group D: 2,0mm/min. The mean and standard deviations, in Kgf, were: A - 66,31(10,24); B - 64,53 (20,40); C - 75,23 (11,84) and D - 66,62 (13,81). The data were submitted to ANOVA (p=0,13). The results indicated that it did not have statistical significant difference between the groups</span><span style="font-size: medium;"> </span><span style="font-size: medium;">A, B, C and D concluding that the speed in this type of test, with this device, can be varied without modify results.</span></p>
PURPOSE In testing adhesion using shear bond test, a combination of shear and tensile forces occur at the interface, resulting in complex stresses. The jig designs used for this kind of test show variations in published studies, complicating direct comparison between studies. This study evaluated the effect of different jig designs on metal-ceramic bond strength and assessed the stress distribution at the interface using finite element analysis (FEA). MATERIALS AND METHODS Metal-ceramic (Metal: Ni-Cr, Wiron 99, Bego; Ceramic: Vita Omega 900, Vita) specimens (N = 36) (diameter: 4 mm, veneer thickness: 4 mm; base diameter: 5 mm, thickness: 1 mm) were fabricated and randomly divided into three groups (n = 12 per group) to be tested using one of the following jig designs: (a) chisel (CH) (ISO 11405), (b) steel strip (SS), (c) piston (PI). Metal-ceramic interfaces were loaded under shear until debonding in a universal testing machine (0.5 mm/min). Failure types were evaluated using scanning electron microscopy (SEM). FEA was used to study the stress distribution using different jigs. Metal-ceramic bond strength data (MPa) were analyzed using ANOVA and Tukey's tests ( = 0.05). RESULTS The jig type significantly affected the bond results (p = 0.0001). PI type of jig presented the highest results (MPa) (p < 0.05) (58.2 ± 14.8), followed by CH (38.7 ± 7.6) and SS jig type (23.3 ± 4.2) (p < 0.05). Failure types were exclusively a combination of cohesive failure in the opaque ceramic and adhesive interface failure. FEA analysis indicated that the SS jig presented slightly more stress formation than with the CH jig. The PI jig presented small stress concentration with more homogeneous force distribution compared to the CH jig where the stress concentrated in the area where the force was applied. CONCLUSION Metal-ceramic bond strength was affected by the jig design. Accordingly, the results of in vitro studies on metal-ceramic adhesion should be evaluated with caution. CLINICAL SIGNIFICANCE When adhesion of ceramic materials to metals is evaluated in in vitro studies, it should be noted that the loading jig type affects the results. Clinical observations should report on the location and type of ceramic fractures in metal-ceramic reconstructions so that the most relevant test method can be identified. AbstractPurpose: In testing metal-ceramic adhesion using shear bond test, a combination of shear and tensile forces occur at the interface resulting in complex stresses. The jig designs used for this kind of test show variations in the published studies that complicate the direct comparison between different studies. This study evaluated the effect of different jig designs on metal-ceramic bond strength and assessed the stress distribution at the interface using finite element analysis. Materials and Methods:Metal-ceramic (Metal: Ni-Cr, Wiron 99, Bego; Ceramic: Vita Omega 900, Vita) specimens (N=36) (diameter: 4 mm, veneer thickness: 4 mm; base diameter: 5 mm and thickness: 1 mm)were fabricated and randomly divided i...
Introdução: O propósito deste estudo é comparar a resistência ao desgaste de três resinas para confecção de coroas temporárias (InstaTemp Provisional Crown & Bridge – Sterngold ImplaMed; Perfect Temp – Discus Dental; Duralay – Reliance Dental), após a simulação de um ano de escovação. Métodos: Foram confeccionados 12 corpos-de-prova (n = 12) com 5mm de diâmetro por 3mm de espessura, de cada marca comercial, obedecendo às especificações do fabricante. Foi utilizada uma matriz, usinada em aço inoxidá- vel, contendo três orifícios para que fossem assentados os corpos-de-prova das diferentes marcas, sendo que apenas 1mm do corpo de prova ficou saliente em relação à superfície da base de aço. Os corpos-de-prova foram acondicionados em água destilada, por catorze dias, a uma temperatura de 37º C, sendo que todas as amostras foram pesadas em uma balança analítica Mettler Toledo, modelo AB204. A simulação da resistência ao desgaste foi realizada em um simulador de escovação no Centro de Pesquisa e Tecnologia da Johnson e Johnson®. As escovas foram trocadas a cada noventa minutos de simulação, e após o total de seis horas, o que corresponderia a um ano de escovação, os corpos-de-prova foram pesados novamente na mesma balança analítica. Resultados e Conclusão: Os resultados obtidos (antes – depois) foram submetidos aos testes t-student e Tukey, ao nível de significância de 5%. Verificou-se que a resina Insta Temp foi a mais resistente ao desgaste, devido à perda de peso sempre ter sido menor que a de Perfect Temp e Duralay.
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