Avaliação das resistencias a fratura e a fadiga de tres sistemas de ceramica dental

Tese (livre-docencia) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaResumo: O propósito deste estudo foi investigar a influência das resistências à fratura e à fadiga (a seco e em água destilada) das cerâmicas In Ceram, OPC¿e IPS Empress, fixadas com os cimentos de fosfato de zinco e ionômero de vidro. Cinqüenta e dois corpos-de-prova com 8 mm de diâmetro por 8,5 mm de altura foram confeccionados para cada tipo de cerâmica. Após aplicação do glaze, as coroas foram fixadas sobre os troqueis de metal com os cimentos de fosfato de zinco e ionômero de vidro. Em seguida, os corpos-de-prova foram armazenados em água destilada por 24 horas em temperatura ambiente antes dos ensaios. Para cada sistema e cimento (fosfato de zinco ou ionômero de vidro), dez corpos-de-prova foram submetidos ao teste de fratura a uma velocidade de 1,0 mm/min.. O segundo grupo foi submetido ao teste de fadiga por 10.000 ciclos, com carga mínima e máxima de 20 e 300 N, aplicada com força em forma sinosoidal com 1 HZ, seguido pelo de fratura em água destilada (8 corpos-de-prova para cada tipo de cimento e cerâmica) e o terceiro grupo em ambiente seco (8 corpos-de-prova para cada tipo de cimento e cerâmica), usando uma máquina Instron. Os resultados foram estatisticamente analisados pelo teste de Mann-Whitney. Os resultados indicaram que (1) - a resistência à fratura para a cerâmica In Ceram com os dois tipos de cimentos foi significantemente superior em relação às OPC¿ e IPS Empress (p<0,05); e nenhuma diferença foi encontrada entre OPC¿ e IPS Empress (2) - quando submetida à fadiga em ambiente seco, In Ceram fixada com inômero de vidro foi significantemente superior em relação à OPC¿ e IPS Empress (p<0,05); e as mesmas diferenças estatísticas foram encontradas quando os corpos-de-prova foram submetidos à fadiga em água destilada; (3) - para os fixados com fosfato de zinco e submetidos à fadiga, In Ceram e OPC¿ a seco foram estatisticamente superiores em relação à IPS Empress (p<0,05); e nenhuma diferença foi encontrada entre In Ceram e OPC¿; (4) -houve uma significante diminuição de resistência para In Ceram e IPS Empress submetidas ao teste de fadiga em água destilada, fixadas com ionômero de vidro, quando comparadas com o teste de fratura; nenhuma diferença foi encontrada quando comparada a seco; e nenhuma diferença foi encontrada para o sistema OPC¿; (5) - nos três sistemas fixados com o cimento de fosfato de zinco houve uma significante diminuição de resistência após o teste de fadiga a seco e em água destilada, quando comparada com o teste de fratura (p<0,05); e para os corpos-de-prova submetidos ao teste de fadiga, o ambiente seco apresentou valores superiores em relação às imersas em água destilada, mas nenhuma diferença estatística foi encontradaAbstract: The aims of this paper was to investigate the influencia of fatigue, on the fracture strength of In ceram, OPC¿ and IPS Empress in both wet and dry environments, luted with zinc phosphate and glass ionomer cements. Fifty two crowns shapes with 8mm in diameter and 8.5mm height were fabricated for each ceramic system. After glazing, the crown shapes were cemented onto identical brass dies with zinc phosphate and glass ionomer cements. After, the specimens were then stored in distilled water at room temperature for 24 hours before testing. For each ceramic system luted with zinc phosphate and glass ionomer cement, ten specimens were tested for fracture strength without fatiguing at a crosshead speed of 1.0 mm per minute. The second group was submitted to a fatigue for 10,000 cycles, with minimum and maximum load of 20 and 300 N applied with the force profile in the form of a sine wave at 1 HZ, and fracture test in wet (8 specimens for each kind of ceramics and cement) and third group in a dry (8 specimens for each kind of ceramics and cement) environment; using a an Instron testing machine. The results were statistically analysed using a Mann-Whitney. The results indicated that (1) - the fracture strength for In ceram using luted zinc phosphate and glass ionomer was significantly stronger than OPC¿ and IPS Empress (p<0.05); (2) - when fatigued in a dry environment, In ceram crown shapes, luted with glass ionomer, were significantly stronger than OPC¿ and IPS Empress (p<0.05). The same statistical differences were found when fatigued in a wet environment; (3) - for luted with zinc phosphate, when fatigued in a dry environment, In ceram and OPC¿ were significantly stronger than IPS Empress (p<0.05); (4) - fatinguing and fracture testing showed a significant decrease in the frature strength for In ceram e IPS Empress in wet environment and no difference was found in dry environment. No difference was found for OPC¿; (5) -the strength of the three ceramic systems, luted with zinc phosphate, decreased significantly after fatiguing in both dry and wet environments, compared with non fatigued. No difference was found between fatiguing in dry and wet environmentsLivre DocênciaMateriais DentáriosLivre-Docente em Odontologi

Ligas do sistema Cu-Al-Zn-Nb, Cu-Al e Cu-Zn : estudos da corrosão quimica e de algumas propriedades fisicas

Orientador: João Manuel Domingos de Almeida RolloDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaResumo: No presente estudo foi elaborada uma liga EXPERIMENTAL à base de Cu-Al-Zn-Nb, onde os elementos de maior ponto de fusão que compõem a liga EXPERIMENTAL, foram adicionados na forma de pó. Alguns ensaios foram realizados, como: análise química. Dureza Vickers, análise metalográfica, corrosão através da análise eletroquímica potenciocinética, contração de fundição, fluidez e tração. A análise química foi realizada por via úmida, enquanto o ensaio de Dureza Vickers numa máquina Vickers Limited, e a metalografia num aparelho NEOPHOT 21 (CARL ZEISS). Já os testes de corrosão foram realizados num aparelho tipo CORROSCRIPT - TUCUSSEL e a contração de fundição em um anel metálico similar ao utilizado por 'EARNSHAW POT.10'. Para o ensaio de fluidez, foram utilizadas telas de nylon similares, a usada por 'PRESSWOOD POT.36'. O ensaio de tração foi efetuado numa máquina de ensaio UNIVERSAL LOSENHAUSENWERK de acordo com a especificação n. 5 da 'A.D.A. POT.1'. Este estudo foi desenvolvido, comparando-se os resultados da liga EXPERIMENTAL com os obtidos de duas ligas comerciais à base de cobre DURACAST MS e GOLDENT LA. Para obtenção dos corpos de prova foi utilizada a técnica de fundição odontológica pelo método da cera perdida. As fundições foram executadas através de um maçarico gás-oxigênio numa centrifuga convencional. Os resultados da análise metalográfica revelaram que não houve a formação de solução sólida nas três ligas estudadas. A liga EXPERIMENTAL e DURACAST MS apresentaram uma resistência à corrosão superior à liga GOLDENT LA. Quanto à Dureza Vickers, a liga EXPERIMENTAL apresentou um valor maior em relação às outras duas ligas. O valor da contração de fundição da liga DURACAST MS foi superior e a liga EXPERIMENTAL apresentou valores de fluidez superiores em relação às duas ligas comerciais. Já para o ensaio de tração, a liga EXPERIMENTAL foi superior e a liga GOLDENT LA apresentou maior valor de alongamento em relação às outras duas ligasAbstract: In the present study it was been developed an experimental alloy fo the Cu-Zn-Al-Nb base. Where the elements the most point of fusion, that compose the experimental alloy where odds in a power form. Some experiments were made, such as: metallographic analysis, corrosion by test eletrochemical potenciocinetic analysis, castability test, tensile test, casting of shrinkage, chemical analysis and Hardness Vickres. The chemical analysis has been made through moist medium, while the Hardness Vickers experiment has been made in a machine Vickers Limited and the metallographic analysis in a device called NEOPHOT 21 (CARL ZEISS). And the corrosion test has been realized in a device called Corroscript Tucussel and the casting of Shrinkage in a metal ring similar to the one used by 'EARNSHAW IND POT.10¿. For the castability test it was used nets of nylon similar to the one used by 'PRESSWOOD POT.36' and the tensile experiment was realized in a machine of the Universal test LOSENHAUSENNERK according to the expecification n. 5 of 'A. D. A. POT.1'. All this study was developed comparing the results of the experimental alloy with ones obtained with two comercial alloys to the base of copper DURACAST MS and GOLDENT LA. In order to obtain test samples, the routine dental casting tecnique, was used with lost wax method. The castings were executed through a gas/oxigen blowpipe in conventional centrifuge. The results from the metalographic analysis has revealed that there hasn't been formation of a solid solution in the three studied alloys. Lhe EXPERIMENTAL and de DURACAST MS alloys have presented a resistance to corrosion superior to the GOLDENT LA alloy. Concerning the Hardness Vickers, the EXPERIMENTAL alloy has presented a bigger value in relation to the other two alloys. The value of casting Shrinkage of the DURACAST MS alloy was superior and the EXPERIMENTAL alloy has presented superior values of castability in relation to the comercial alloys. And for the tensile test the EXPERIMENTAL alloy was superior and the GOLDENT LA alloy has presented a bigger alongation value in relation to the other two alloysMestradoMateriais DentariosMestre em Odontologi

Permeability Roughness And Topography Of Enamel After Bleaching: Tracking Channels Of Penetration With Silver Nitrate

Aim: This study evaluated the surface roughness, topography and permeability of bovine enamel by profilometry and scanning electron microscopy (SEM) with and without silver nitrate solution, after exposure to different bleaching agents. Methods: Fifty-two enamel samples were randomly divided into four groups (n=13): CP16% –16% carbamide peroxide - Whiteness Perfect; HP6% - 6% hydrogen peroxide - White Class; HP35% - 35% hydrogen peroxide Whiteness HP Maxx; and Control - not bleached and kept in artificial saliva. For roughness analysis, average surface roughness (Ra) and flatness coefficient (Rku) parameters were used. The topography and permeability were examined by SEM. For permeability evaluation, the samples were immersed in a 50% silver nitrate solution and analyzed using a backscattered electron and secondary electron mode. Results: For the roughness (Ra) evaluation, Kruskal-Wallis and Wilcoxon Signed Ranks Test were used, showing an increase on the surface roughness in all bleached groups. The Rku parameter suggested changes on enamel integrity. The SEM micrographs indicated changes on enamel topography and different levels of silver nitrate penetration in the samples of the bleached groups. In the overall analysis, the bleaching agents promoted surface changes and higher silver nitrate penetration when compared to the control group. Conclusions: It may be concluded that different bleaching agents might alter the topography and roughness of enamel surface. Moreover, the higher infiltration of silver nitrate suggests an easier penetration path for the oxygen molecules into the dentin substrate.1011-

Clinical evaluation of the failure rates of metallic brackets

The aim of this study was to evaluate in vivo the bonding of metallic orthodontic brackets with different adhesive systems. Material and methods: Twenty patients (10.5-15.1 years old) who had sought corrective orthodontic treatment at a University Orthodontic Clinic were evaluated. Brackets were bonded from the right second premolar to the left second premolar in the upper and lower arches using: Orthodontic Concise, conventional Transbond XT, Transbond XT without primer, and Transbond XT associated with Transbond Plus Self-etching Primer (TPSEP). The 4 adhesive systems were used in all patients using a split-mouth design; each adhesive system was used in one quadrant of each dental arch, so that each group of 5 patients received the same bonding sequence. Initial archwires were inserted 1 week after bracket bonding. The number of bracket failures for each adhesive system was quantified over a 6-month period. Results: The number of debonded brackets was: 8- Orthodontic Concise, 2- conventional Transbond XT, 9- Transbond XT without primer, and 1- Transbond XT + TPSEP. By using the Kaplan-Meier methods, statistically significant differences were found between the materials (p=0.0198), and the Logrank test identified these differences. Conventional Transbond XT and Transbond XT + TPSEP adhesive systems were statistically superior to Orthodontic Concise and Transbond XT without primer (p<0.05). There was no statistically significant difference between the dental arches (upper and lower), between the dental arch sides (right and left), and among the quadrants. Conclusions: The largest number of bracket failures occurred with Orthodontic Concise and Transbond XT without primer systems and few bracket failures occurred with conventional Transbond XT and Transbond XT+TPSEP. More bracket failures were observed in the posterior region compared with the anterior region.20222823

Shear Bond Strength Of Metallic Brackets Bonded With A New Orthodontic Composite

Aim: The aim of this study was to assess the shear bond strength of orthodontic brackets in different enamel surfaces using the Transbond Plus Color Change composite (TPCC-3M Unitek), and to analyze the Adhesive Remnant Index (ARI). Methods: Seventy-two human premolars were divided into six groups (n = 12), as follows: Group 1(control) - Transbond XT conventional; in Groups 2 to 6, TPCC was used under the following enamel treatment conditions: phosphoric acid and XT-primer; Transbond Plus Self-Etching Primer (TPSEP); phosphoric acid only; phosphoric acid, XT-primer and saliva; and TPSEP and saliva, respectively. Twenty-four hours after bonding, the brackets were debonded with an Instron machine at a crosshead speed of 0.5 mm/min, and ARI was evaluated by using a stereoscopic magnifying glass. Results: The mean shear strength values (MPa) for Groups 1 to 6 were 24.6, 18.7, 17.5, 19.7, 17.5 and 14.8, respectively. Data were submitted to ANOVA and Tukey’s test (? = 0.05). Group 1 had significantly higher shear bond strength values than Groups 3, 5, and 6 (p 0.05). No statistically significant differences (p > 0.05) were found between Groups 2, 3, 4, 5 and 6. Conclusions: Bracket bonding using TPCC showed adequate adhesion for clinical use, and the type of enamel preparation had no influence.8276-8

Estudo comparativo do tipo de substrato dental utilizado em testes de resistência de união ao cisalhamento

The purpose of this study was to compare shear bond strength values obtained in human enamel and dentin with the values obtained in bovine teeth using two adhesive systems with different actions. Forty human tooth half-crowns and forty bovine tooth crowns were flattened to a minimum plain area of 5 mm in diameter. The samples were divided in four groups of 20 specimens each: 1) human enamel; 2) bovine enamel; 3) human dentin; 4) bovine dentin. The samples of each group were divided in 2 subgroups of 10 samples each, according to the adhesive system used: 1) Scotchbond Multi-Purpose (SBMP); and 2) Clearfil Liner Bond 2V (CLB2V) applied according to the manufacturer's recommendations. Afterwards, restorations of Z100 composite with cylindrical shape (4 mm diameter x 5 mm height) were made using a metallic mold to submit the samples to shear bond testing on an Instron universal testing machine, at a crosshead speed of 0.5 mm/min. The data were submitted to ANOVA and Tukey's test (5%). In enamel, there was no statistical difference between bovine and human teeth for SBMP (7.36 MPa, human; 8.24 MPa, bovine), nor for CLB2V (10.01 MPa, human; 7.95, bovine). In dentin, SBMP showed a statistically lower mean on human dentin (7.01 MPa) than on bovine dentin (11.74 MPa). For CLB2V, there was no statistical difference between human (7.43 MPa) and bovine (9.27 MPa) substrates.O propósito deste estudo foi comparar os valores de resistência de união sobre esmalte e dentina humanos com os valores obtidos em dentes bovinos, utilizando dois sistemas de união com princípios de atuação distintos. Para isso, desgastaram-se 20 meias coroas dentais humanas e 40 coroas bovinas, até obter uma área plana de pelo menos 5 mm de diâmetro. As 80 amostras foram separadas em 4 grupos de 20 amostras cada, sendo: 1) dente humano em esmalte, 2) dente bovino em esmalte, 3) dente humano em dentina, 4) dente bovino em dentina. As amostras de cada grupo foram divididas em 2 subgrupos de 10 amostras cada, de acordo com o sistema de união utilizado: 1) Scotchbond Multi-Uso (SBMU); e 2) Clearfil Liner Bond 2V (CLB2V). Em seguida, confeccionou-se um cilindro do compósito Z100 (4 mm de diâmetro x 5 mm de altura) utilizando-se uma matriz bipartida, para submeter os corpos-de-prova ao ensaio de cisalhamento numa máquina de ensaio Instron com velocidade de 0,5 mm/min. Os dados foram submetidos à análise de variância e as médias, ao teste de Tukey (5%). Em esmalte, não se verificou diferença estatística entre os dentes humanos e bovinos para os materiais SBMU (7,36 MPa, humano; e 8,24 MPa, bovino) e CLB2V (10,01 MPa, humano; e 7,95 MPa, bovino). Verificou-se que o SBMU apresentou média estatisticamente inferior em dentina humana (7,01 MPa), quando comparado à dentina bovina (11,74 MPa). Para o material CLB2V, não houve diferença estatística entre os substratos humano (7,43 MPa) e bovino (9,27 MPa)

Effect of the increase of energy density on knoop hardness of dental composites light-cured by conventional QTH, LED and xenon plasma arc

The aim of this study was to evaluate the effect of the increase of energy density on Knoop hardness of Z250 and Esthet-X composite resins. Cylindrical cavities (3 mm in diameter X 3 mm in depth) were prepared on the buccal surface of 144 bovine incisors. The composite resins were bulk-inserted and polymerized using different light-curing units and times: conventional QTH (quartz-tungsten-halogen; 700 mW/cm²; 20 s, 30 s and 40 s); LED (light-emitting diode; 440 mW/cm²; 20 s, 30 s and 40 s); PAC (xenon plasma arc; 1700 mW/cm²; 3 s, 4.5 s and 6 s). The specimens were stored at 37°C for 24 h prior to sectioning for Knoop hardness assessment. Three measurements were obtained for each depth: top surface, 1 mm and 2 mm. Data were analyzed statistically by ANOVA and Tukey's test (p0.05) were found for QTH. Knoop hardness values decreased with the increase of depth. The increase of energy density produced composites with higher Knoop hardness means using LED and PAC.Este estudo teve como objetivo avaliar o efeito do aumento da densidade de energia na dureza Knoop das resinas compostas Z250 e Esthet-X. Cavidades cilíndricas (3 mm de diâmetro X 3mm de profundidade) foram preparadas na superfície vestibular de 144 incisivos bovinos. As resinas compostas foram inseridas em incremento único e fotopolimerizadas com diferentes unidades e tempos de fotopolimerização: luz halógena convencional (700 mW/cm²; 20 s, 30 s and 40 s); LED (diodo emissor de luz; 440 mW/cm²; 20 s, 30 s and 40 s); PAC (arco de plasma de xenônio; 1700 mW/cm²; 3 s, 4,5 s and 6 s). Os espécimens foram armazenados a 37°C durante 24 h, previamente à realização das leituras de dureza Knoop. Foram realizadas três leituras por profundidade: superfície, 1 mm e 2 mm. Os dados foram submetidos à ANOVA e ao teste de Tukey (p0.05). Os valores de dureza Knoop diminuíram com o aumento da profundidade. O aumento da densidade de energia produziu compósitos com maior dureza Knoop quando o LED e o PAC foram utilizados como fontes de polimerização.21822

Resistência à compressão de ionômeros de vidro modificados por resina: efeito da relação P/L e tempos de armazenagem

O objetivo deste estudo foi avaliar a resistência à compressão dos cimentos de ionômero de vidro modificados por resina Vitremer e Fuji II LC, nas relações pó/líquido 1:1, 1:2 e 1:3, por três períodos de armazenagem (24 horas, 7 e 28 dias) em água destilada a 37 ºC. Para cada material, relação pó/líquido e tempo de armazenagem, cinco corpos-de-prova cilíndricos foram preparados com 4 mm de diâmetro por 6 mm de altura, em moldes de silicone. Os corpos-de-prova foram fotoativados por 40 segundos, em cada extremidade, removidos dos moldes, fotoativado lateralmente (perpendicular ao longo eixo) por 40 segundos, protegidos conforme as instruções dos fabricantes e imersos pelo tempo de teste. Os corpos-de-prova foram submetidos à compressão em uma Instron, à velocidade de 1,0 mm/min até a falha. Os dados foram submetidos à análise de variância e ao teste de Tukey (5%), e mostraram que a resistência à compressão do cimento de ionômero de vidro modificado por resina foi reduzida quando a relação P/L foi diminuída e a armazenagem em água destilada teve pouca influência na resistência à compressão.The aim of this study was to evaluate the compressive strength of resin-modified glass ionomer cement Fuji II LC and Vitremer, in powder/liquid ratios of 1:1, 1:2 and 1:3, at three periods (24 hours, 7 and 28 days) of storage in distilled water at 37ºC. For each material, P/L ratio and storage time, 5 cylindrical specimens were prepared, with 4mm diameter and 6mm height, in silicon moulds. Specimens were light-cured for 40 seconds at each extremity, removed from the moulds and laterally light-cured (perpendicular to long axis) for 40 seconds, protected as recommended by the manufacturers and immersed for the time tested. The specimens were submitted to compressive strength testing in an Instron machine at a crosshead speed of 1.0mm/min until failure. Data were submitted to ANOVA and Tukey's test (5%), and showed that the compressive strength of resin-modified glass ionomer cement was reduced when P/L ratio was reduced and that the storage in water had little influence on compressive strength

Three-month water degradation of resin-dentin interfaces subjected to direct and indirect exposure

Objectives: The aim of this study was to assess the effects direct or indirect water exposure on the 3 months hydrolytic degradation of three dentin bonding agents. Materials and methods: The samples were divided in three groups: Clearfil SE Bond, Clearfil S3, Adper Singlebond 2; and the samples were restored with Filtek Z350. Subsequent to the restorative procedures, the specimens of each group were divided into three subgroups (immersed in water deionised): Control (24h-37ºC), Direct Water exposure DWE for 3 months (37º), Indirect water exposure (IWE-3m) with enamel margins for 3 months (37ºC). After the storage the samples were sectioned into sticks and µTBS testing (EZ test) and Scanning Electronic Microscopy assessed the failure mode. The µTBS data were statistically analysed using two-way ANOVA and Tukey’s test at α=0.05%. The samples were processed for nanoleakage evaluation immersed in 50 wt% ammoniacal silver nitrate (24 h), rinsed and immersed in a photo-developing solution for 8 h. Results: After 3 months CSE was the least affected by water degradation regardless the aging strategy. IWE afforded very little variation on µTBS after 3 m.  Intense nanoleakage was observed with DWE groups with increases incidence of mixed failures instead Conclusion: Bonded dentin margins are more prone to hydrolytic degradation than resin-enamel interfaces. The increased nanoleakage and the drop of bond strength showed this

Clinical evaluation of the failure rates of metallic brackets

OBJECTIVES: The aim of this study was to evaluate in vivo the bonding of metallic orthodontic brackets with different adhesive systems. MATERIAL AND METHODS: Twenty patients (10.5-15.1 years old) who had sought corrective orthodontic treatment at a University Orthodontic Clinic were evaluated. Brackets were bonded from the right second premolar to the left second premolar in the upper and lower arches using: Orthodontic Concise, conventional Transbond XT, Transbond XT without primer, and Transbond XT associated with Transbond Plus Self-etching Primer (TPSEP). The 4 adhesive systems were used in all patients using a split-mouth design; each adhesive system was used in one quadrant of each dental arch, so that each group of 5 patients received the same bonding sequence. Initial archwires were inserted 1 week after bracket bonding. The number of bracket failures for each adhesive system was quantified over a 6-month period. RESULTS: The number of debonded brackets was: 8- Orthodontic Concise, 2- conventional Transbond XT, 9- Transbond XT without primer, and 1- Transbond XT + TPSEP. By using the Kaplan-Meier methods, statistically significant differences were found between the materials (p=0.0198), and the Logrank test identified these differences. Conventional Transbond XT and Transbond XT + TPSEP adhesive systems were statistically superior to Orthodontic Concise and Transbond XT without primer (p<0.05). There was no statistically significant difference between the dental arches (upper and lower), between the dental arch sides (right and left), and among the quadrants. CONCLUSIONS: The largest number of bracket failures occurred with Orthodontic Concise and Transbond XT without primer systems and few bracket failures occurred with conventional Transbond XT and Transbond XT+TPSEP. More bracket failures were observed in the posterior region compared with the anterior region