Influencia do tratamento de superficie em uma liga de paladio-prata na resistencia de união de agentes cimentantes

Orientador: Simonides ConsaniTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaResumo: O propósito do estudo foi avaliar a influência de quatro tratamentos de superfície, efetuados em uma liga de paládio-prata, na resistência da união ao cisalhamento de três agentes cimentantes. Inicialmente, foram confeccionadas fundições em forma de disco (5 mm de diâmetro), com liga de paládio-prata, sendo os espécimes agrupados em pares, após limpeza manual e em ultra-som com água. Em seguida, os pares foram separados em quatro grupos de 30 cada, para realização de um dos seguintes tratamentos nas faces circulares opostas às correspondentes aos condutos de alimentação: 1 - bruto de fundição (controle); 2 aplicação de jato de óxido de alumínio malha 320; 3 - aplicação de jato de óxido de alumínio malha 60; e 4 - aplicação de jato de micro esferas de vidro malha 270. Após nova limpeza em ultra-som com água destilada, durante 5 minutos, os exemplares de cada grupo foram separados em três sub-grupos de 10 cada, sendo feita a fixação, através das faces tratadas, com um dos seguintes agentes cimentantes: A - cimento de fosfato de zinco; B - cimento de ionômero de vidro modificado por resina; e C - cimento resinoso. Dez espécimes de cada tratamento de superfície foram submetidos à análise da rugosidade média, sendo também feito Lo preparo de dois exemplares para observação com microscopia eletrônica de varredura. Após 24 horas de armazenagem em água destilada a 37°C, os pares fixados foram avaliados com ensaios de cisalhamento em máquina Instron (1 mm/min), até a ruptura das amostras. Os resultados foram submetidos à análise de variância e ao teste de Tukey (p < 0,05) e as médias obtidas (MPa) foram: Grupo 1 A: 1,77 (0,51); Grupo 1 B: 3,18 (1,42); Grupo 1 C: 1,63 (0,55); Grupo 2 A: 5,22 (0,88); Grupo 2 B: 11,90 (1,94); Grupo 2 C: 16,29 (3,94); Grupo 3 A: 4,03 (0,78); Grupo 3 B: 11,41 (2,69); Grupo 3 C: 14,15 (2,71); Grupo 4 A: 1,59 (0,44); Grupo 4 B: 2,24 (0,71); Grupo 4 C: 1,74 (0,51). As superfícies metálicas submetidas ao jato de óxido de alumínio (malhas 320 ou 60) proporcionaram maior resistência de união que a condição de bruto de fundição e que as superfícies submetidas ao jato de micro esferas de vidro malha 270. Nas superfícies tratadas com jato de óxido de alumínio, o cimento resinoso e o cimento de ionômero de vidro modificado por resina proporcionaram resistências de união estatisticamente superiores à do cimento de fosfato de zinco. Não houve relação entre a resistência de união dos agentes cimentantes e a rugosidade média das ligas metálicasAbstract: The purpose of this study was to evaluate the influence of four metal surface treatments on the shear bond strength of three luting agents. Cast samples in a disk shape (5 mm in diameter) were made with palladium-silver alloy and grouped in pairs afier ultrasonic cleaning. The pairs were assigned into four groups of 30 each and submitted to the following treatments on the circular surfaces opposite to that of the sprue former: 1 - as cast (control); 2 - aluminum oxide blasting (320 mash); 3 - aluminum oxide blasting (60 mash); and 4 - glass beads blasting (270 mash). Afier new ultrasonic cleaning in distilled water, during 5 minutes, the samples of each group were assigned into three subgroups of 10 each, being made the cementing, by the treated surfaces, with the following luting agents: A - zinc phosphate cement; B - resin-modified glass ionomer cement; and C ¿ resin cement. Before luting, 10 specimens of each treatment had the surfaces measured for roughness and two samples were prepared to observation in scanning electronic microscope. Afier storing in distilled water at 37°C, during 24 hours, the cemented pairs were submitted to shear bond strength tests in an Instron machine (1 mm/min), until the failure. The results were analyzed by ANOVA and Tukey's test (p < 0,05) and the means (MPa) were: Group 1 A: 1.77 (0.51); Group 1 B: 3.18 (1.42); Group 1 C: 1.63 (0.55); Group 2 A: 5.22 (0.88); Group 2 B: 11.90 (1.94); Group 2 C: 16.29 (3.94); Group 3 A: 4.03 (0.78); Group 3 B: 11.41 (2.69); Group 3 C: 14.15 (2.71); _Group 4 A: 1.59 (0.44); Group 4 B: 2.24 (0.71); Group 4 C: 1.74 (0.51). The metallic surfaces submitted to the aluminum oxide blast treatment (320 or 60 mash) showed bond strengths significantly higher than those of surfaces as cast or submitted to glass beads blast (270 mash). On surfaces treated with aluminum oxide blast, the resin cement and the resin-modified glass ionomer cement showed bond strengths statistical/y superior to those of the zinc phosphate cement. There was not a relationship between the bond strengths of cementing agents and the roughness of metal/ic surfacesDoutoradoDoutor em Materiais Dentário

Compressive strength of a glass ionomer cement under the influence of varnish protection and dietary fluids

The objective of this study was to evaluate the compressive strength of a glass ionomer cement (GIC) under the influence of varnish protection and dietary fluids. Eighty cylindrical test specimens were made from GIC and distributed into four groups (G1, G2, G3, G4) according to the dietary fluid. Each group was further divided into subgroups A and B according to the presence or absence of varnish protection. The eight subgroup samples were stored in distilled water for 30 days and received the following treatments for 14 days: G2A: varnish protection and immersion in soft drink, G2B: no varnish protection and immersion in soft drink, G3A: varnish protection and immersion in orange juice, G3B: no varnish protection and immersion in orange juice, G4A: varnish protection and immersion in yogurt, G4B: no varnish protection and immersion in yogurt. The immersion procedure was performed three times a day, for 15 minutes at a time, for a total of 14 days. The samples from subgroups G1A (with varnish) and G1B (without varnish) were used as controls and stored in distilled water only for 30 days. The samples were submitted to a compressive strength test after the immersion period. The results were analyzed using the ANOVA 2, Tukey test (5%) and Student’s t-test (5%). There were no significant differences between the subgroups, except for the subgroup with varnish protection and immersion in orange juice, which showed reduced GIC compressive strength.El objetivo de este estudio fue evaluar la resistencia a la compresión de un cemento de ionómero de vidrio (GIC) bajo la influencia de la protección del barniz y alimentos. Ochenta muestras cilíndricas de GIC fueron realizadas y se distribuyeron en cuatro grupos (G1, G2, G3, G4) de acuerdo con el alimento. Cada grupo se sub-dividió además en A y B, de acuerdo con la presencia o ausencia de protección de barniz. Las ocho muestras de cada subgrupo se almacenaron en agua destilada durante 30 días y recibieron los siguientes tratamientos durante 14 días: G2A: protección del barniz e inmersión en gaseosas, G2B: sin barniz e inmersión en gaseosas, G3A: protección del barniz e inmersión en jugo de naranja, G3B: sin protección de barniz e inmersión en jugo de naranja, G4A: protección de barniz e inmersión en yogurt, G4B: sin protección de barniz e inmersión en yogur. El procedimiento de inmersión se realizó tres veces al día, durante 15 minutos por 14 días. Las muestras del Subgrupo G1A (con barniz) y G1B (sin barniz) se usaron como controles y se almacenaron en agua destilada. Las muestras se sometieron a una prueba de resistencia a la compresión después del período de inmersión. Los resultados se analizaron usando ANOVA 2, prueba de Tukey (5%) y T de Student (5%). No hubo diferencias significativas entre los subgrupos, a excepción del subgrupo con protección de barniz e inmersión en jugo de naranja, que mostró una resistencia a la compresión GIC reducida

The influence of desensitizing dentifrices on pain induced by in-office bleaching

The purpose of this study was to evaluate whether the use of desensitizing dentifrices used 15 days prior to and after in-office tooth bleaching could eliminate or reduce tooth sensitivity. After institutional review board approval and informed consent, 45 subjects were selected and divided into 3 groups according to the dentifrice selected: Colgate Total (CT), Colgate Sensitive Pro-Relief (CS) or Sensodyne ProNamel (SP). The subjects used toothpaste and a toothbrush provided to them for 15 days prior to bleaching. They were then submitted to two in-office bleaching sessions (Whiteness HP Blue Calcium). Their tooth sensitivity was assessed using the Visual Analog Scale (VAS) for a week after each session. Their tooth shade alteration was measured with a Vitapan Classical shade guide to determine if the dentifrices could influence the effectiveness of the bleaching agent. The data were submitted to Wilcoxon, Kruskal-Wallis and Mann-Whitney tests (&#945; = 0.05). The use of desensitizing dentifrices did not affect the bleaching efficacy. In regard to tooth sensitivity, there was a statistically significant difference between the results of the Control Group and Group T2 after the first session (p = 0.048). There was no statistically significant difference in the results for the other groups after the first session. In regard to the second session, there was no statistically significant difference in the results for all the groups. The use of a desensitizing dentifrice containing nitrate potassium reduced tooth sensitivity during the bleaching regimen. Dentifrices containing arginine and calcium carbonate did not reduce tooth sensitivity. Color change was not influenced by the dentifrices use

Influence of light intensity on mechanical properties of the resin composite

of this study was to evaluate Vickers micro-hardness and flexural strength, of five commercial resin composites cured by two light curing units (LCU) with different intensities. The inorganic filling content of the composite was evaluated by thermogravimetric analysis (TGA) and the morphology of the surface was analyzed by scanning electron microscopy (SEM), in composites cured by different light intensities and immersed into a commercial soft drink or distilled water. The results show an improvement in the mechanical properties when the highest intensity of the halogen light-curing unit was used. At the same intensity of LCU, the highest values for the mechanical properties were found in specimens with a higher percentage by weight of filler. The better values were observed for micro-hardness and flexural strength in hybrid resin composites than in microfill resin composites. When the material was stored in the soft drink, changes occurred in the composite structure. The SEM images show a fractured specimen immersed in the soft drink compared with the control group, maintained in distilled water. The images show the low level of light beam penetration into resin composites, since the removal of resin components at the central part of the specimen was higher than at the surface near the light incidence