Fracture toughness of three heat pressed ceramic systems

Aim: The aim of this study was to evaluate fracture toughness by indentation method of three dental ceramics processed by heat pressing. The ceramics evaluated were fluorapatite glass ceramic (ZIR), glass ceramic containing leucite (POM) and leucite-reinforced glass ceramic (EMP). Materials and methods: Ninety disks (13mm of diameter x 4mm of thickness) and nine rectangular specimens (25x4x2mm) were made to evaluate, respectively, microhardness/fracture toughness (n=30) and elastic modulus (n=3). Samples were obtained by pressing ceramic into refractory molds. After polishing, Vickers microhardness was evaluated under 4,904N load for 20s. Elastic modulus was measured by impulse excitation technique. Data from microhardness and elastic modulus were used to calculate fracture toughness, after measuring crack length under 19,6N load applied for 20s. Results were evaluated by ANOVA and Tukey´s test. Results: Microhardness (VHN) of POM (637.9±53.6) was statistically greater (p<0.05) than ZIR (593.0±14.3), followed by EMP (519.1±21.5); no significant difference (p=0.206) was noted for elastic modulus (GPa) (ZIR: 71.5±9.0; POM: 67.3±4.4; EMP: 61.7±2.3). Fracture toughness (MPa/m) of POM (0.873±0.066) was statistically lower (p<0.05) than ZIR (0.977±0.021) and EMP (0.965±0.035). Conclusion: The results suggest that fluorapatite glass ceramic (ZIR) and leucite-reinforced glass ceramic (EMP) processed by heat pressing presented greater fracture toughness, improving clinical prognosis of metal free restorations

As ligas odontológicas determinam a escolha das resinas compostas a serem utilizadas: desgaste de ligas odontológicas contra resinas compostas / The dental alloys determine the choice of composite resins to be used: wear of dental alloys against composite resins

Objetivo: O objetivo deste estudo foi avaliar a resistência ao desgaste de duas resinas compostas contra ligas alternativas. Materiais e Métodos: Quinze amostras de corpo cônico foram obtidas das resinas Z250 e charisma (CHA). As amostras foram divididas em três grupos de acordo com o disco da liga a ser utilizada como antagonista: NíquelCromo (Ni-Cr), Cobalto-Cromo (Co-Cr) e titânio comercialmente puro (Ti cp). Os testes de desgaste foram realizados na velocidade de 265 ciclos/minuto e distância de 10mm, totalizando 40.000 ciclos. Antes e após os testes de desgaste, as amostras foram pesadas e tiveram seu perfil desenhado em projetor de perfil para avaliar a perda de peso e de altura, respectivamente. Resultados: Para a perda de peso e de altura, o desgaste de Z250 foi menor do que CHA para o antagonista de Co-Cr, mas maior para o Ti cp. CHA apresenta superfície mais regular, sem fendas, e aspecto semelhante para todos os antagonistas. Z250 apresentou algumas fendas, principalmente contra Ti cp e Ni-Cr. Conclusão: Baseado nos resultados deste estudo, concluiu-se que CHA é mais apropriada contra Ti cp, e Z250 para associação com liga de Co-Cr enquanto qualquer resina composta pode ser utilizada contra Ni-Cr. (AU)

Objective: The aim of the present study was to evaluate wear resistance of two composites resins against alternative alloys. Material and Methods: Fifteen stylus tips samples of composite resin were obtained for each resin Z250 and charisma (CHA). Samples were divided into three groups according to the disk of alloy to be used as antagonist: NickelChromium (Ni-Cr), Cobalt- Chromium (Co-Cr) and commercially pure titanium (cp Ti). Wear tests were performed at a speed of 265 cycles/min and distance of 10mm, in a total of 40,000 cycles. Before and after wear tests, samples were weighed and had their profile designed in an optical comparator to evaluate weight and height loss, respectively. Results: For weight and height loss, wear of Z250 was lower than CHA for Co-Cr antagonist, but greater for cp Ti. CHA presents a more regular surface without cracks and similar aspect for all antagonists. Z250 showed some cracks, mainly against cp Ti and Ni-Cr. Conclusion: Within the results of the present study, it was concluded that CHA is suitable against cp Ti, and Z250 for association with Co-Cr alloy while any composite resin can be used against Ni-Cr.(AU)

Tensile Strength of Resin Cements Used with Base Metals in a Simulating Passive Cementation Technique for Implant-Supported Prostheses

Abstract The aim of this study was to analyze the tensile strength of two different resin cements used in passive cementation technique for implant-supported prosthesis. Ninety-six plastic cylinders were waxed in standardized forms, cast in commercially pure titanium, nickel-chromium and nickel-chromium-titanium alloys. Specimens were cemented on titanium cylinders using self-adhesive resin cement or conventional dual-cured resin cement. Specimens were divided in 12 groups (n=8) in accordance to metal, cement and ageing process. Specimens were immersed in distilled water at 37 °C for 24 h and half of them was thermocycled for 5,000 cycles. Specimens were submitted to bond strength test in a universal test machine EMIC-DL2000 at 5 mm/min speed. Statistical analysis evidenced higher tensile strength for self-adhesive resin cement than conventional dual-cured resin cement, whatever the used metal. Self-adhesive resin cement presented higher tensile strength compared to conventional dual-cured resin cement. In conclusion, metal type and ageing process did not influence the tensile strength results.

Resumo O objetivo deste estudo foi analisar a resistência à tração de dois diferentes cimentos resinosos usados na técnica de cimentação passiva de próteses implanto-suportadas. Noventa e seis cilindros plásticos foram encerados em formas padronizadas, fundidos em titânio grau 2 comercialmente puro e ligas de níquel-cromo e níquel-cromo-titânio. Amostras foram cimentadas sobre cilindros de titânio usando um cimento auto-adesivo ou um cimento convencional de dupla polimerização. Os espécimes foram divididos em 12 grupos (n=8) de acordo com o metal, cimento e processo de envelhecimento. Espécimes foram imersos em água destilada a 37 °C por 24 h e metade deles foi termociclado por 5,000 ciclos. Espécimes foram submetidos ao ensaio de tração numa máquina universal de ensaios (velocidade de 5 mm/min). Análise estatística evidenciou maior resistência à tração do cimento auto adesivo do que o cimento convencional de dupla polimerização, independente do metal utilizado. O cimento resinoso auto adesivo apresentou maior resistência à tração do que o cimento convencional de dupla polimerização. O tipo de metal e o processo de envelhecimento não tiveram influência nos resultados.

Fracture Strength of Weakened Anterior Teeth Associated to Different Reconstructive Techniques

Abstract This study evaluated the fracture strength of endodontically treated teeth submitted to reconstructive techniques through dynamic and static tests. Forty human anterior teeth were divided into 4 groups (n=10): GNW (non-weakened) - root restored with glass fiber post (GFP), GW - weakened root restored with GFP, GDA - weakened root restored with direct anatomic GFP, and GIA - weakened root restored with indirect anatomic GFP. The teeth were endodontically treated considering that experimental groups (GW, GDA and GIA) simulated weakened roots for restoration with GFP using different techniques. The GFP was luted with resin cement and the coronal portion was restored with composite resin and metallic crowns. All samples were submitted to chewing simulation at 60 cycles/min in a total of 300,000 cycles. The survival samples were further exposed to compressive loading at a crosshead speed of 1.0 mm/min in a universal testing machine. The load was applied at 135° to the long axis of the tooth until failure. Data were analyzed by ANOVA (a=0.05). After chewing simulation were observed: GNW: 100% of survival roots; GW: 70% of survival roots, and GDA and GIA: 80% of survival roots. The mean fracture strength values (N) were 280.6 (GNW), 239.0 (GW), 221.3 (GDA), and 234.1 (GIA) without significant difference among the groups (p=0.7476). The results suggested similar fracture strength in both weakened and non-weakened teeth regardless the reconstructive technique of root internal wall. Higher incidence of catastrophic fracture was observed in weakened teeth without restoration of the root internal wall.

Resumo Este estudo avaliou a resistência à fratura de dentes tratados endodonticamente submetidos a diferentes técnicas de reconstrução por meio de testes dinâmico e estático. Quarenta dentes humanos anteriores foram divididos em 4 grupos (n=10): GNW (não fragilizado): raiz restaurada com pino de fibra de vidro (PFV), GW: raiz fragilizada restaurada com PFV, GDA: raiz fragilizada restaurada com PFV anatômico direto, e GIA: raiz fragilizada restaurada com PFV anatômico indireto. Os dentes foram tratados endodonticamente considerando que nos grupos experimentais (GW, GDA e GIA) simulou-se fragilização radicular das raízes para restauração com PFV utilizando diferentes técnicas. Os PFV foi cimentados com cimento resinoso e a porção coronária foi restaurada com resina composta e coroa metálica. Todas as amostras foram submetidas a simulação de mastigação em 60 ciclos/min totalizando 300,000 ciclos. As amostras sobreviventes foram submetidas a teste de compressão com velocidade de 1,0 mm/min em máquina universal de ensaio. A carga foi aplicada a 135° em relação ao longo eixo do dente até a falha do dente. Os dados foram analisados por ANOVA (a=0,05). Após a simulação da mastigação foi observado: GNW: 100% de sobrevivência das raízes; GW: 70% de sobrevivência das raízes, e GDA e GIA: 80% de sobrevivência das raízes. O valor médio de resistência à fratura (N) foi de 280,6 (GNW), 239,0 (GW), 221,3 (GDA) e 234,1 (GIA) sem diferença significante entre os grupos (p=0,7476). Os resultados sugerem similar resistência à fratura em ambos os dentes fragilizados ou não-fragilizados em relação à técnica de reconstrução das paredes radiculares internas. Elevada incidência de fraturas catastróficas foram observadas nos dentes fragilizados sem a restauração das paredes radiculares internas.

Reliability of FEA on the Results of Mechanical Properties of Materials

The present study evaluated the reliability of FEA on the results of different mechanical properties (E and v) of materials. Two 3D models of a maxillary canine with endodontic treatment, intracanal post, composite resin core and restored with porcelain-fused-to-metal crown were generated according to micro-CT images. Two groups with different E and ν values for porcelain, metal coping alloy, resin cement and composite resin were established. The materials' properties for group GL were based on literature data, while for group GIE the impulse excitation technique was used. A load of 180 N was applied at 45° on the incisal third of the lingual surface of the canine tooth. All models were supported by the periodontal ligament (x=y=z=0). The von Mises stress (VMS) was calculated. The stress values revealed differences between the groups for both VMS distribution and value. The porcelain (GL: 5.966 MPa; GIE: 7.478 MPa), metal coping (GL: 3.811 MPa; GIE: 0.973 MPa) and core (GL: 4.771 MPa; GIE: 0.026 MPa) were significantly affected. In conclusion, this study showed that the determination of mechanical properties (E and ν) of materials is essential for the reliability on the results of FEA.

Resumo O presente estudo avaliou a confiabilidade do MEF nos resultados de diferentes propriedades mecânicas (E e v) dos materiais. Dois modelos 3D de um canino superior com tratamento endodôntico, pino intrarradicular, núcleo em resina composta e restaurado com coroa metalocerâmica foram gerados de acordo com imagens de micro-CT. Dois grupos com diferentes valores de E e v para a cerâmica, coping metálico, cimento resinoso e resina composta foram criados. As propriedades dos materiais para o grupo GL foram baseadas em dados obtidos da literatura, enquanto para o grupo GIE a técnica de excitação por impulso foi utilizada. Carga de 180 N foi aplicada a 45° na superfície lingual do terço incisal do canino. Todos os modelos foram suportados pelo ligamento periodontal (x=y=z=0). Tensões equivalentes de von Mises (VMS) foram calculadas. Os valores de tensões revelaram diferença entre os grupos, ambos para a distribuição e valor das VMS. A cerâmica (GL: 5,966 MPa; GIE: 7,478 MPa), coping metálico (GL: 3,811 MPa; GIE: 0,973 MPa) e núcleo (GL: 4,771 MPa; GIE: 0,026 MPa) foram significativamente afetados. Em conclusão, este estudo mostrou que a determinação das propriedades mecânicas (E and v) dos materiais é essencial para a confiabilidade dos resultados do MEF.

In Vitro Fit and Cementation Resistance of Provisional Crowns for Single Implant-Supported Restorations

Abstract: This study aimed to verify marginal fit and the effect of cement film thickness standardization on retention of provisional crowns made with prefabricated acrylic cylinders on abutments, using two temporary luting agents subjected or not to mechanical cycling. Provisional crowns were made from bis-acryl (Luxatemp Fluorescence) or methyl methacrylate (Duralay) resins on acrylic cylinders and marginal fit and cement film thickness were evaluated. For retention evaluation, crowns were cemented with two temporary luting agents: non-eugenol zinc oxide (Tempbond NE) or calcium hydroxide-based (Hydcal) cements and subjected to tensile strength in a universal testing machine. After cleaning, debonded crowns were cemented again, subjected to mechanical cycling and retention was reassessed. The results of marginal fit and cement film thickness were analyzed by Student's t-test while retention of cements before and after mechanical cycling was analyzed using a mixed linear model. Methyl methacrylate crowns presented greater marginal misfit (p=0.001) and occlusal cement film thickness (p=0.003) than the bis-acryl ones. No difference was observed at axial cement film thickness (p=0.606). Resins (p=0.281) did not affect crown retention, but luting agents (p=0.029) and mechanical cycling (p=0.027) showed significant effects. The only significant interaction was mechanical cycling*luting agents, which means that luting agents were differently affected by mechanical cycling (p=0.002). In conclusion, the results showed that bis-acryl resin associated to calcium-hydroxide luting agent provided the best retention and lower cement thickness.

Resumo: O objetivo deste estudo foi avaliar a adaptação marginal e o efeito da espessura da camada de cimento na retenção de coroas provisórias fixadas sobre os pilares com o auxílio de cilindros acrílicos pré-fabricados, utilizando dois cimentos provisórios submetidos ou não à ciclagem mecânica. Coroas provisórias foram confeccionadas com resina bis-acrilíca (Luxatemp Flourescence) ou resina à base de metil metacrilato (Duralay) sobre os cilindros, para posterior avaliação da influência das diferentes resinas na adaptação marginal e na espessura da linha do cimento. Para a avaliação da resistência à tração, as coroas foram cimentadas com dois cimentos provisórios: à base de óxido de zinco sem eugenol (Temp Bond NE) ou hidróxido de cálcio (Hydcal) e submetidas ao teste de tração em máquina universal de ensaio. Após o ensaio, as coroas foram limpas e novamente cimentadas para serem submetidas à ciclagem mecânica e posterior avaliação da resistência à tração. Os resultados obtidos para adaptação marginal e espessura do cimento foram analisados pelo teste t de Student, enquanto os resultados de resistência à cimentação antes e após a ciclagem mecânica foram analisados pelo modelo linear de efeitos mistos. As coroas confeccionadas com a resina de metil metacrilato apresentaram maiores valores para desadaptação marginal (p=0,001) e espessura do cimento (p=0,003) na parede oclusal quando comparadas com as coroas de resina bis-acrílica. Não houve diferença na espessura do cimento (p=0,606) na parede axial das coroas provisórias. As diferentes resinas não afetaram a resistência à cimentação das coroas (p=0,281), mas os diferentes cimentos (p=0,029) e a ciclagem mecânica (p=0,027) mostraram efeitos significantes. A única interação significante foi ciclagem mecânica ?#61482; agente cimentante, o que significa que os cimentos foram diferentemente afetados pela ciclagem mecânica (p=0,002). Em conclusão, a associação resina bis-acrílíca e cimento de hidróxido de cálcio proporcionou melhor resistência à tração e menor espessura de cimento.

Resistência retentiva de coroas implantossuportadas unitárias antes e após ciclagem termomecânica / Retentive strength of single-tooth implant-supported crowns before and after thermomechanical cycling

Objetivo: verificar a resistência à tração em coroas implantossuportadas cimentadas, antes e após o processo de ciclagem termomecânica. Material e métodos: foram confeccionadas18 coroas totais metálicas em liga de Ni-Cr a partir de cilindros calcináveis. As coroas foram cimentadas sobre pilares tipo munhão universal, instalados sobre implantes embutidos em bases cilíndricas de aço inoxidável. Foram testados os seguintes cimentos: cimento de óxido de zinco sem eugenol (OZ), cimento de fosfato de zinco (FZ) e cimento resinoso (RE), sendo seis corpos-de-prova para cada grupo. Após a cimentação, as coroas foram tracionadas em máquina universal de ensaios com velocidade de 0,5 mm/min. Após a limpeza, os corpos-de-prova foram novamente cimentados e submetidos ao ensaio de ciclagem termomecânica com carga de 120 N e temperatura entre 5°-55°C, sendo 500.000 ciclos mecânicos com frequência de 2 Hz e 2083 ciclos térmicos (um ciclo térmico: dois minutos). O ensaio de resistência foi realizado novamente, sendo os dados anotados e analisados estatisticamente. Resultados: a resistência de cimentação de FZ foi superior ao RE e OZ antes e após a ciclagem mecânica. A ciclagem termomecânica diminuiu significativamente a resistência de cimentação do grupo FZ. Conclusão: o cimento OZ foi o menos retentivo, seguido pelo RE e FZ, antes e após a ciclagem termomecânica. Além disso, o cimento FZ é mais susceptível às alterações pela ciclagem termomecânica.

Importance of a distal proximal contact on load transfer by implant-supported single adjacent crowns in posterior region of the mandible: a photoelastic study

OBJECTIVE: This study aimed to evaluate the importance of a distal proximal contact on the load transfer to the posterior region of the mandible by non-splinted adjacent implant-supported crowns using photoelastic stress analysis. MATERIAL AND METHODS: A rectangular model (68x30x15 mm) was made of polymethylmethacrylate resin to simulate half of the mandibular arch. One model was completed with resin replicas representing the first premolar and second molar and with two 3.75 mm dia.x11 mm internal hexagon threaded implants replacing the second premolar and first molar. The other model was manufactured in the same way but without the second molar. Both models were duplicated using photoelastic resin. The roots of the teeth replicas were covered with a layer of polyether impression material to simulate the periodontal ligament. Two different vertical loads were applied to the crowns as follows: 1 - single static point load alternately applied to the crowns replacing the second premolar and first molar (50 N); 2 - simultaneous static point loads applied to both of the crowns replacing the second premolar and first molar (100 N). The resulting isochromatic fringe pattern in the photoelastic model was monitored and photographed. RESULTS: All loading conditions studied showed that the presence of the second molar has changed the load transmission and the pattern of stresses. CONCLUSION: Results showed that the presence of a second molar proximal contact can help minimize the stresses around the implants. .

Avaliação da estabilidade do implante pela análise da frequência de ressonância: estudo in vivo com carregamento imediato e precoce em um modelo em cães / Evaluation of implant stability by means of resonance frequency analysis: an in vivo study with immediate and early loading in the dog model

Este estudo teve por objetivo avaliar a estabilidade de implantes de carga imediata ou precoce, em diferentes intervalos de tempo. Material e Métodos: foram extraídos os pré-molares mandibulares, bilateralmente, de oito cães e, após 12 semanas, cada cão recebeu seis implantes (três em cada lado da mandíbula). A carga foi aplicada em pares, em um implante de cada lado, sendo que o primeiro par recebeu carga imediata, o segundo par após sete dias, e o terceiro par após 14 dias. Em cada período, as medidas de estabilidade dos implantes foram realizadas por frequência de ressonância (ISQ). Após 12 semanas, uma nova leitura da estabilidade dos implantes foi realizada. A análise estatística foi feita usando modelo linear de efeitos mistos, que é uma generalização do modelo linear padrão (Anova). Diferenças foram consideradas significantes quando p < 0,05. Resultados: a estabilidade do implante mudou no decorrer do tempo para todos os protocolos de carga, apresentando aumento significativo na estabilidade final, mas as variações foram semelhantes para os três grupos estudados. Nos períodos de sete dias e 14 semanas, o protocolo de carga imediata apresentou menor estabilidade de implante do que os protocolos de sete e 14 dias. Conclusão: a estabilidade do implante diminui nos períodos iniciais após a cirurgia e aumenta no período de 14 semanas. A estabilidade dos implantes do protocolo de carga imediata é menor do que a dos protocolos de sete e 14 dias, sugerindo cautela para seu uso...

This study aimed to evaluate implant stability in function with immediate or early loading protocols at different time intervals. Material and Methods: The mandibular premolars of eight dogs were pulled bilaterally. After 12 weeks, each dog received 6 implants (3 at each mandibular side). Implant loading was performed for each implant pair according to the following periods: immediate (fi rst pair), 7 days later (second pair), 14 days later (third pair). Implant stability measurements were performed by means of resonance frequency for each period. After 12 weeks, new readings of implant stability were obtained. The statistical analysis was performed using a mixed linear model, which is a generalization of the standard linear model (Anova), with differences considered signifi cant at p<0.05. Results: Implant stability changed throughout time for all loading protocols, presenting a significant increase in fi nal stability values, but variations were similar for the three studied groups. At 7- and 14-week periods, immediate loading protocol presented lower implant stability than 7-day or 14-day protocols. Conclusions: Implant stability diminishes in the initial periods after surgery, and increases in a 14-week period. In the middle-term, there were no statistically significant differences in the stability of immediately-loaded implants, one or two weeks after implant placement...

Effect of toothbrushing with different toothpastes at commerciallypure titanium surface roughness / Efeito da escovação com diferentes dentifrícios na rugosidade superficial do titânio comercialmente puro

Objective: To evaluate the effect of brushing, using toothpastes with different fluoride concentrations, on the surface of commercially pure titanium (cp Ti). Methods: Discs (13x4mm) made of cp Ti, embedded in PVC rings and metallographically polished have their surface roughness measured. Tooth brushing simulations (50,400 cycles) were performed: speed of 80mm/s, distance of 10mm distance, at 240 cycles/min. Three toothpastes were tested: Prevident 5000 (Colgate-Palmolive Ind. e Com. Ltda., São Paulo, Brazil), Colgate Total 12 (Colgate-Palmolive Ind. e Com. Ltda., São Paulo, Brazil) and Tandy (Colgate-Palmolive Ind. e Com. Ltda., São Paulo, Brazil), with 5000, 1300 and 500ppm fluoride concentrations, respectively. The brushings had 7.14g and 14.28g of toothpaste, both for 50mL of deionized water. The surface roughness was reevaluated and data were analyzed by two-way ANOVA and Tukey?s test for the effect of brushing and toothpastes. Results: At the beginning, no significant difference (p=0.09) of roughness was noted among the experimental groups (Prevident, Colgate-Palmolive Ind. e Com. Ltda., São Paulo, Brazil): 0.160±0.019; Colgate Total 12 (Colgate-Palmolive Ind. e Com. Ltda., São Paulo, Brazil): 0.159±0.030; Tandy (Colgate-Palmolive Ind. e Com. Ltda., São Paulo, Brazil): 0.157±0.019) but roughness decreased after the 1st (p<0.05) (0.094±0.010) and 2nd (0.089± 0.012) brushings (p<0.05) with Prevident 5000 (Colgate-Palmolive Ind. e Com. Ltda., São Paulo, Brazil), with no significant difference between the 1st and 2nd brushings (p=0.16). Discs brushed with Colgate Total 12 (Colgate-Palmolive Ind. e Com. Ltda., São Paulo, Brazil) presented surface roughness similar (p=0.090) at the beginning and after the 1st brushing (0.133±0.029), and between the 1st and 2nd (0.113±0009) brushings (p=0.402); roughness after the 2nd brushing was statistically greater than at the beginning (p<0.05). Tandy (Colgate- Palmolive Ind. e Com. Ltda., São Paulo, Brazil) toothpaste caused a surface roughness significantly lower (p<0.05) after the 2nd brushing (0.113±0.010), compared to the 1st (0.147±0.020) and the starting point, which were statistically similar (p=0.090). Conclusion: The results suggest that brushing using toothpastes with fluoride causes a decrease in the surface roughness of cp Ti, mainly when greater fluoride concentrations are present.

Objetivo: Avaliar o efeito da escovação com dentifrícios contendo diferentes concentrações de flúor na superfície do titânio comercialmente puro (Ti cp). Métodos: Discos (13x4mm) de Ti cp, embutidos em anéis de PVC e polidos metalograficamente, tiveram a rugosidade superficial avaliada. A simulação da escovação (50400 ciclos) teve velocidade de 80mm/s, curso de 10mm, com 240 ciclos/min. Foram testados três dentifrícios: Prevident 5000, (Colgate-Palmolive Ind. e Com. Ltda., São Paulo, Brasil); Colgate Total 12 (Colgate-Palmolive Ind. e Com. Ltda., São Paulo, Brasil) e Tandy (Colgate-Palmolive Ind. e Com. Ltda., São Paulo, Brasil), com 5000, 1300 e 500ppm de flúor, respectivamente. As escovações tiveram 7,14g e 14,28g de dentifrício, ambas para 50ml de água deionizada. A rugosidade superficial foi reavaliada e os dados analisados por ANOVA - dois fatores e teste de Tukey quanto ao efeito da escovação e dos dentifrícios. Resultados: Inicialmente não houve diferença significante (p=0,09) na rugosidade dos grupos experimentais Prevident, (Colgate-Palmolive Ind. e Com. Ltda., São Paulo, Brasil): 0,160±0,019; Colgate Total 12 (Colgate-Palmolive Ind. e Com. Ltda., São Paulo, Brasil): 0,159±0,030; Tandy (Colgate- Palmolive Ind. e Com. Ltda., São Paulo, Brasil): 0,157±0,019), mas houve diminuição da rugosidade após a 1ª (0,094±0,010) (p<0,05) e 2ª (0,089±0,012) escovações (p<0,05) com Prevident 5000 (Colgate-Palmolive Ind. e Com. Ltda., São Paulo, Brasil), sem diferença significativa entre as demais (p=0,16). Discos escovados com Colgate Total 12 (Colgate-Palmolive Ind. e Com. Ltda., São Paulo, Brasil) apresentaram rugosidade semelhante inicialmente (p=0,090) e após a 1ª escovação (0,133± 0,029), e entre a 1ª e a 2ª escovações (0,113±0,009) (p=0,402); a rugosidade após a 2ª escovação foi significativamente maior que a inicial (p<0,05). O dentifrício Tandy (Colgate-Palmolive Ind. e Com. Ltda., São Paulo, Brasil) causou rugosidade superficial significativamente menor (p<0,05) após a 2ª escovação (0,113±0,010), comparada à 1ª (0,147±0,020) e a inicial, que foram semelhantes (p=0,090). Conclusão: Os resultados sugerem que a escovação com dentifrícios fluoretados diminui a rugosidade superficial do Ti cp, mais significativamente quanto maiores as concentrações de flúor presentes.

Effect of whitening toothpaste on titanium and titanium alloy surfaces

Dental implants have increased the use of titanium and titanium alloys in prosthetic applications. Whitening toothpastes with peroxides are available for patients with high aesthetic requirements, but the effect of whitening toothpastes on titanium surfaces is not yet known, although titanium is prone to fluoride ion attack. Thus, the aim of the present study was to compare Ti-5Ta alloy to cp Ti after toothbrushing with whitening and conventional toothpastes. Ti-5Ta (%wt) alloy was melted in an arc melting furnace and compared with cp Ti. Disks and toothbrush heads were embedded in PVC rings to be mounted onto a toothbrushing test apparatus. A total of 260,000 cycles were carried out at 250 cycles/minute under a load of 5 N on samples immersed in toothpaste slurries. Surface roughness and Vickers microhardness were evaluated before and after toothbrushing. One sample of each material/toothpaste was analyzed by Scanning Electron Microscopy (SEM) and compared with a sample that had not been submitted to toothbrushing. Surface roughness increased significantly after toothbrushing, but no differences were noted after toothbrushing with different toothpastes. Toothbrushing did not significantly affect sample microhardness. The results suggest that toothpastes that contain and those that do not contain peroxides in their composition have different effects on cp Ti and Ti-5Ta surfaces. Although no significant difference was noted in the microhardness and roughness of the surfaces brushed with different toothpastes, both toothpastes increased roughness after toothbrushing.

Effect of fluoride sodium mouthwash solutions on cpTI: evaluation of physicochemical properties

The effects of fluoride, which is present in different oral hygiene products, deserve more investigation because little is known about their impact on the surface of titanium, which is largely used in Implantology. This study evaluated the surface of commercially pure titanium (cpTi) after exposure to different concentrations of sodium fluoride (NaF). The hypothesis tested in this study was that different concentrations of NaF applied at different time intervals can affect the titanium surface in different ways. The treatments resulted in the following groups: GA (control): immersion in distilled water; GB: immersion in 0.05% NaF for 3 min daily; GC: immersion in 0.2% NaF for 3 min daily; GD: immersion in 0.05% NaF for 3 min every 2 weeks; and GE: immersion in 0.2% NaF for 3 min every 2 weeks. The experiment lasted 60 days. Roughness was measured initially and every 15 days subsequently up to 60 days. After 60 days, corrosion analysis and anodic polarization were done. The samples were examined by scanning electron microscopy (SEM). The roughness data were analyzed by ANOVA and there was no significant difference among groups and among time intervals. The corrosion data (i corr) were analyzed by the Mann-Whitney test, and significant differences were found between GA and GC, GB and GC, GC and GD, GC and GE. SEM micrographs showed that the titanium surface exposed to NaF presented corrosion that varied with the different concentrations. This study suggests that the use of 0.05% NaF solution on cpTi is safe, whereas the 0.2% NaF solution should be carefully evaluated with regard to its daily use.

Os efeitos do fluoreto, o qual está presente em diferentes produtos de higiene oral, necessita de maiores investigações, pois pouco se sabe sobre seus efeitos na superfície do titânio, o qual possui amplo uso na implantodontia. Este estudo objetivou avaliar a superfície do titânio comercialmente puro (cpTi) após exposição a diferentes concentrações de fluoreto de sódio (NaF). A hipótese testada neste estudo foi que diferentes concentrações de NaF aplicadas em diferentes intervalos de tempo seriam capazes de afetar diferentemente a superfície do titânio. Os tratamentos realizados foram: GA (controle): imersão em água destilada; GB: imersão diária por 3 min em NaF a 0,05%; GC: imersão diária por 3 min em NaF a 0,2%; GD: imersão quinzenal por 3 min em NaF a 0,05%; e GE: imersão quinzenal por 3 min em NaF a 0,2%. O tempo do experimento foi de 60 dias. A análise da rugosidade foi efetuada inicialmente e a cada 15 dias. Após 60 dias foi realizada análise de corrosão e polarização anódica. As amostras foram analisadas em MEV. Os dados de rugosidade foram analisados por ANOVA e não houve diferença estatisticamente significante entre grupos e entre tempos. Os dados de corrosão (i corr) foram analisados pelo teste de Mann-Whitney e foram encontradas diferenças significantes entre GA e GC, GC e GB, GC e GD, GC e GE. A MEV evidenciou que a superfície do titânio exposto ao NaF apresentou corrosão variando de acordo com a concentração. Com base nos dados encontrados conclui-se que o uso de solução NaF a 0,05% em cpTi é seguro, enquanto a solução NaF 0,2% para uso diário deve ser cuidadosamente avaliada.

Effects of chemical composition on the corrosion of dental alloys

The aim of this study was to determine the effect of the oral environment on the corrosion of dental alloys with different compositions, using electrochemical methods. The corrosion rates were obtained from the current-potential curves and electrochemical impedance spectroscopy (EIS). The effect of artificial saliva on the corrosion of dental alloys was dependent on alloy composition. Dissolution of the ions occurred in all tested dental alloys and the results were strongly dependent on the general alloy composition. Regarding the alloys containing nickel, the Ni-Cr and Ni-Cr-Ti alloys released 0.62 mg/L of Ni on average, while the Co-Cr dental alloy released ions between 0.01 and 0.03 mg/L of Co and Cr, respectively.The open-circuit potential stabilized at a higher level with lower deviation (standard deviation: Ni-Cr-6Ti = 32 mV/SCE and Co-Cr = 54 mV/SCE). The potenciodynamic curves of the dental alloys showed that the Ni-based dental alloy with >70 wt% of Ni had a similar curve and the Co-Cr dental alloy showed a low current density and hence a high resistance to corrosion compared with the Ni-based dental alloys. Some changes in microstructure were observed and this fact influenced the corrosion behavior for the alloys. The lower corrosion resistance also led to greater release of nickel ions to the medium. The quantity of Co ions released from the Co-Cr-Mo alloy was relatively small in the solutions. In addition, the quantity of Cr ions released into the artificial saliva from the Co-Cr alloy was lower than Cr release from the Ni-based dental alloys.

O objetivo deste estudo foi determinar o efeito do ambiente bucal na corrosão de diferentes ligas odontológicas, utilizando métodos eletroquímicos. Os índices de corrosão foram obtidos por meio das curvas de corrente-potencial e impedância eletroquímica (EIS). O efeito de saliva artificial na corrosão de ligas odontológicas foi dependente da composição. A dissolução dos íons ocorreu em todas as amostras e os resultados foram dependentes da composição da liga. Algumas mudanças na microestrutura foram observadas durante o estudo e influenciou o comportamento corrosivo das ligas investigadas. As ligas de Ni-Cr e Ni-Cr-Ti libertaram quantidade de 0,62 mg/L de íons Ni enquanto a liga de Co-Cr liberou entre 0,01 e 0,03 mg/L. As curvas potenciodinâmicas das ligas odontológicas mostraram que as ligas a base >70 wt% de Ni obtiveram curvas similares e a liga de Co-Cr apresentou a menor densidade de corrente e em consequência uma resistência alta a corrosão quando comparada as ligas à base de Ni. A baixa resistência à corrosão também levou a maior libertação de íons de níquel para o meio e a quantidade de Co liberado pela liga de Co-Cr-Mo foi relativamente pequena nas soluções. As quantidades de Cr liberada na saliva artificial pela liga de Co-Cr foi menor que a libertação de Cr pela liga à base de Ni.

Effect of laser welding on the titanium ceramic tensile bond strength

Titanium reacts strongly with elements, mainly oxygen at high temperature. The high temperature of titanium laser welding modifies the surface, and may interfere on the metal-ceramic tensile bond strength. OBJECTIVE: The influence of laser welding on the titanium-ceramic bonding has not yet been established. The purpose of this in vitro study was to analyze the influence of laser welding applied to commercially pure titanium (CpTi) substructure on the bond strength of commercial ceramic. The influence of airborne particle abrasion (Al2O3) conditions was also studied. MATERIAL AND METHODS: Forty CpTi cylindrical rods (3 mm x 60 mm) were cast and divided into 2 groups: with laser welding (L) and without laser welding (WL). Each group was divided in 4 subgroups, according to the size of the particles used in airborne particle abrasion: A - Al2O3 (250 µm); B - Al2O3 (180 µm); C - Al2O3 (110 µm); D - Al2O3 (50 µm). Ceramic rings were fused around the CpTi rods. Specimens were invested and their tensile strength was measured at fracture with a universal testing machine at a crosshead speed of 2.0 mm/min and 200 kgf load cell. Statistical analysis was carried out with analysis of variance and compared using the independent t test (p<0.05). RESULTS: Significant differences were found among all subgroups (p<0.05). The highest and the lowest bond strength means were recorded in subgroups WLC (52.62 MPa) and LD (24.02 MPa), respectively. CONCLUSION: Airborne particle abrasion yielded significantly lower bond strength as the Al2O3 particle size decreased. Mechanical retention decreased in the laser-welded specimens, i.e. the metal-ceramic tensile bond strength was lower.

Evaluation of screw loosening on new abutment screws and after successive tightening

This study evaluated the loss of the torque applied after use of new screws and after successive tightening. Four infrastructures (IE), using UCLA castable abutment type, were cast in cobalt-chromium alloy and new abutment screws (G1) were used in a first moment. Subsequently, the same abutment screws were used a second time (G2) and more than two times (G3). The values of the torques applied and detorques were measured with a digital torque wrench to obtain the values of initial tightening loss ( percent). Data were analyzed by ANOVA and Tukey's test (?=0.05). Significant differences were observed between the G1 (50.71 percent ± 11.36) and G2 (24.01 percent ± 3.33) (p=0.000) and between G1 (50.71 percent ± 11.36) and G3 (25.60 percent ± 4.64) (p=0.000). There was no significant difference between G2 and G3 (p=0.774). Within the limitations of the study, it may be concluded that the percentage of the initial torque loss is lower when screws that already suffered the application of an initial torque were used, remaining stable after application of successive torques.

O objetivo deste estudo foi avaliar a perda do torque inicial, quando usados novos parafusos de pilares e após sucessivos apertos. Quatro infra-estruturas (IE), utilizando pilares calcináveis tipo UCLA, foram fundidas em liga de cobalto-cromo, onde novos parafusos de pilares foram utilizados (G1) em um primeiro momento. Posteriormente os mesmos parafusos de pilares foram utilizados em um segundo momento (G2), e depois por mais duas vezes (G3). Os valores de torque e detorque aplicados foram mensurados a partir de um torquímetro digital para obtenção dos valores de perda do torque inicial ( por cento). Os dados foram coletados e submetidos à análise de variância e teste de Tukey (p<0,05). Foram observadas diferenças estatisticamente significantes entre os grupos G1 (50,71 por cento ± 11,36) and G2 (24,01 por cento ± 3,33) (p=0,000) and the groups G1 (50,71 por cento ± 11,36) and G3 (25,60 por cento ± 4,64) (p=0,000). Os maiores valores foram encontrados para o grupo G1. Não houve diferença estaticamente significante entre os grupos G2 e G3 (p=0,774). Dentro das limitações deste estudo, pôde-se observar que a porcentagem de perda de torque inicial foi menor quando os parafusos já haviam sofrido a aplicação do primeiro torque, se mantendo estáveis após os demais torques.

Comparative study of two commercially pure titanium casting methods

The interest in using titanium to fabricate removable partial denture (RPD) frameworks has increased, but there are few studies evaluating the effects of casting methods on clasp behavior. OBJECTIVE: This study compared the occurrence of porosities and the retentive force of commercially pure titanium (CP Ti) and cobalt-chromium (Co-Cr) removable partial denture circumferential clasps cast by induction/centrifugation and plasma/vacuum-pressure. MATERIAL AND METHODS: 72 frameworks were cast from CP Ti (n=36) and Co-Cr alloy (n=36; control group). For each material, 18 frameworks were casted by electromagnetic induction and injected by centrifugation, whereas the other 18 were casted by plasma and injected by vacuum-pressure. For each casting method, three subgroups (n=6) were formed: 0.25 mm, 0.50 mm, and 0.75 mm undercuts. The specimens were radiographed and subjected to an insertion/removal test simulating 5 years of framework use. Data were analyzed by ANOVA and Tukey's to compare materials and cast methods (α=0.05). RESULTS: Three of 18 specimens of the induction/centrifugation group and 9 of 18 specimens of plasma/vacuum-pressure cast presented porosities, but only 1 and 7 specimens, respectively, were rejected for simulation test. For Co-Cr alloy, no defects were found. Comparing the casting methods, statistically significant differences (p<0.05) were observed only for the Co-Cr alloy with 0.25 mm and 0.50 mm undercuts. Significant differences were found for the 0.25 mm and 0.75 mm undercuts dependent on the material used. For the 0.50 mm undercut, significant differences were found when the materials were induction casted. CONCLUSION: Although both casting methods produced satisfactory CP Ti RPD frameworks, the occurrence of porosities was greater in the plasma/vacuum-pressure than in the induction/centrifugation method, the latter resulting in higher clasp rigidity, generating higher retention force values.

Shear bond strength of dental ceramics to cast commercially pure titanium

Aim: The objective of this study was to evaluate the bond strength of four dental ceramics to commercially pure titanium. Methods: To measure the resistance of metal-ceramic bonding,ceramic rings (Noritake Ti22®, Triceran®, IPS®, Noritake EX-3®) were made around metal rodsfused to commercially pure titanium. The area of metal-ceramic union was measured and, after mounting in type III plaster, the rings were subjected to a shearing force in a universal testing machine at a cross head speed of 2 mm/s until failure occurred. The metal-ceramic shear bond resistance was calculated in MPa. Results: The shear bond strength means for the ceramics Triceram and Noritake Ti22 (42.50 MPa and 61 MPa, respectively) were higher than the minimum value required by the DIN 13927 standard (25 MPa). The ceramics IPS and NoritakeEX3, although not specifically formulated for titanium, also had shear bond strength means above the ISO-recommended value (38.47 MPa and 29.04 MPa, respectively); however, there cracks in some specimens after burning and detachment of the ceramic from the metal. Conclusions:The ceramic Noritake Ti22 should be indicated for the commercially pure titanium casting due to its higher mean bond resistance compared to other ceramics utilized.

Effect of phosphate-bonded investments on titanium reaction layer and crown fit

This study analyzed the reaction layer and measured the marginal crown fit of cast titanium applied to different phosphate-bonded investments, prepared under the following conditions (liquid concentration/casting temperature): Rema Exakt (RE) - 100 percent/237°C, 75 percent/287°C, Castorit Super C (CS)-100 percent/70°C, 75 percent/141°C and Rematitan Plus (RP)- 100 percent/430°C (special to titanium cast, as the control group). The reaction layer was studied using the Vickers hardness test, and analyzed by two way ANOVA and Tukey's HSD tests (á = 0.05). Digital photographs were taken of the crowns seated on the die, the misfit was measured using an image analysis system and One-way ANOVA, and Tukey's test was applied (á = 0.05). The hardness decreased from the surface (601.17 VHN) to 150 ìm (204.03 VHN). The group CS 75 percent/141°C presented higher hardness than the other groups, revealing higher surface contamination, but there were no differences among the groups at measurements deeper than 150 ìm. The castings made with CS - 100 percent/70°C presented the lowest levels of marginal misfit, followed by RE -100 percent/237°C. The conventional investments CS (100 percent) and RE (100 percent) showed better marginal fit than RP, but the CS (75 percent) had higher surface contamination.

Avaliação da resistência à abrasão do Ti cp frente a diversos materiais restauradores / Evaluation of Wear Resistance of cp Ti Opposing Several Restorative Materials

O uso do titânio comercialmente puro (Ti cp) tem aumentado na confecção de estruturas metálicas de próteses. Assim, o objetivo deste trabalho foi avaliar in vitro a resistência à abrasão do Ti cp em oposição a diversos materiais restauradores. Foram fundidos corpos-de-prova de forma hemiesféricas (5mm de raio) em titânio cp grau I por arco voltaico em atmosfera inerte de argônio. Como antagonistas foram preparados discos com 20,0mm de diâmetro de: Ti cp; ligas de Co-Cr e Ni-Cr, resina composta TPH e cerâmica Empress-2, todos com rugosidade de 0,75 micrometro. Foram realizados aproximadamente 40000 ciclos (4,4Hz) sob carga constante de 5N. A resistência à abrasão do titânio foi medida pelo desgaste vertical dos corpos-de-prova hemiesféricos em projetor de perfil Nikon. Os dados foram submetidos à ANOVA e teste complementar de Tukey (alfa=0,05). Os resultados (micrometros) encontrados foram: Ti cp X resina (37,75±7,99); Ti cp X cerâmica (73,25±9,96); Ti cp X Co-Cr (77,17±9,95), Ti cp X Ti cp (199,00±86,90) e Ti cp X Ni-Cr (261,50±39,23). Não houve diferença significante (p>0,05) quando os antagonistas foram de resina, cerâmica e liga de Co-Cr. Quando submetido a antagonistas de Ti cp e liga de Ni-Cr os resultados foram estatisticamente significantes (p<0,05), com maior desgaste contra o antagonista de Ni-Cr. É possível concluir que o material a ser utilizado na arcada antagonista deve ser escolhido cuidadosamente quando as próteses forem confeccionadas em Ti cp porque há o risco de desgaste da prótese.

The use of commercially pure titanium (cp Ti) has increased in prosthodontics frameworks. Thus, the aim of the present study was to evaluate in vitro wear resistance of cp Ti opposing several restorative materials. Hemispheres (r=5mm) were cast in cp grade I by arc melting under inert argon atmosphere. As antagonistic samples, disks of 20mm in diameter were prepared in cp Ti, Co-Cr and Ni-Cr alloy, composite resin and Empress-2 ceramic, and roughness was adjusted to 0.75 micrometro. It was performed approximately 40,000 cycles (4.4Hz) using a load of 5N. Wear resistance of cp Ti was measured as height loss of hemispherical samples in a Nikon profile projector. The data were submitted to ANOVA and post-hoc Tukey test (alfa=0.05). The results (micrometros) were: cp Ti X composite resin (37.75±7.99); cp Ti X ceramic (73.25±9.96); cp Ti X Co-Cr (77.17±9.95), cp Ti X cp Ti (199.00±86.90) and cp Ti X Ni-Cr (261.50±39.23). No significant difference was noted (p>0.05) when antagonistic were composite resin, ceramic or Co-Cr alloy. When cp Ti opposed to cp Ti and Ni-Cr alloy, the results were statistically significant (p<0.05), presenting greater wear when Ni-Cr alloy was used as antagonist. It is possible to conclude that the material used as antagonist should be chosen carefully when titanium frameworks are used because there is a risk of wear of prostheses.