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)

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. .

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 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 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.

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.

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.

Implant/abutment vertical misfit of one-piece cast frameworks made with different materials

This study compared vertical and passive fit of one-piece cast frameworks made with 3 different materials: commercially pure titanium (CP Ti - G1), cobalt-chromium alloy (Co-Cr - G2) and nickel-chromium-titanium alloy (Ni-Cr-Ti - G3). Fifteen frameworks were obtained simulating bars for fixed prosthesis in a model with 5 implants. The passive and vertical fit of the framework interface was measured using an optical microscope at ×30 magnification. Data were statistically analyzed by ANOVA and LSD tests (α=0.05). Mean and standard deviation values for passive fit and vertical fit were, respectively: G1 [472.49 (109.88) µm and 29.9 (13.24) µm], G2 [584.84 (120.20) µm and 27.05 (10.30) µm], and G3 [462.70 (179.18) µm and 24.95 (11.14) µm]. For vertical fit, there were no significant differences among G1, G2 and G3 (p=0.285). There were no significant differences for passive fit between G1 and G3 (p=0.844), but both differed significantly from G2 (p=0.028 and p=0.035, respectively), which showed the highest misfit values. It may be concluded that the vertical fit of frameworks was not affected by the tested materials, and that one-piece cast frameworks resulted in inadequate passive fit. The Co-Cr alloy presented the worst values for passive fit.

Este estudo tem como objetivo comparar o ajuste vertical e a passividade de infraestruturas em monobloco confeccionadas em 3 diferentes materiais: titânio comercialmente puro (Ti cp - G1), cobalto-cromo (Co-Cr - G2) e níquel-cromo-titânio (Ni-Cr-Ti - G3). Quinze infraestruturas foram obtidas simulando barras para próteses fixas em um modelo com 5 implantes. O ajuste vertical e a passividade da interface da infraestrutura foram medidos usando um microscópio óptico (30×). Os dados foram analisados estatisticamente por meio da ANOVA e teste LSD (α=0,05). A média dos valores e o desvio-padrão da passividade e do ajuste vertical estão apresentados respectivamente: Ti cp [472,49 (109,88) μm e 29,9 (13,24) μm], Co-Cr [584,84 (120,20) μm e 27,05 (10,30) μm], Ni-Cr-Ti [462,70 (179,18) μm e 24,95 (11,14) μm]. Para o desajuste vertical, não houve diferença significante entre o Ti cp e as ligas Co-Cr e Ni-Cr-Ti (p=0,285). Para passividade, não houve diferença significante entre Ti cp e Ni-Cr-Ti (p=0,844), mas ambos foram estatisticamente diferentes do Co-Cr (p=0,028 e p=0,035, respectivamente), o qual apresentou os piores resultados. Pode-se concluir que os materiais utilizados para confecção das infraestruturas não influenciaram o ajuste vertical e que infraestruturas fundidas em monobloco resultaram em inadequados ajustes passivos. A liga de Co-Cr apresentou os piores resultados para a passividade.

Effect of temperature variation on the cytotoxicity of cast dental alloys and commercially pure titanium

Cell culture system has been used to evaluate alloy cytotoxicity under different environments, testing the extracts, but the effect of temperature variation on the cytotoxicity of dental alloys has not been analyzed. OBJECTIVE: The aim of the present study was to investigate if temperature variation could affect dental alloy cytotoxicity, testing alloy extracts in an epithelial cell culture system. MATERIAL AND METHODS: Discs of Ni-Cr, Co-Cr-Mo, Ni-Cr-Ti, Ti-6Al-4V and commercially pure titanium (cp Ti) were cast by arc melting, under argon atmosphere, injected by vacuum-pressure. Discs were immersed in artificial saliva and subjected to different temperatures: 37ºC and thermocycling (37ºC/5ºC/37ºC/55ºC/37ºC). After thermocycling, extracts were put in a subconfluent culture during 6 h, and the number of cells and their viability were used to evaluate cytotoxicity in these temperatures. For each alloy, data from temperature conditions were compared by Student's t-test (α=0.05). RESULTS: The cytotoxicity tests with alloy/metal extracts showed that Ni-Cr, Co-Cr-Mo, Ti-6Al-4V and cp Ti extracts (p>0.05) did not affect cell number or cell viability, while Ni-Cr-Ti (p<0.05) extract decreased cell number and viability when the alloy was subjected to thermocycling. CONCLUSION: Within the limitations of the present study, the Ni-Cr-Ti alloy had cell number and viability decreased when subjected to temperature variation, while the other alloys/metal extracts did not show these results.

Abrasion wear resistance of different artificial teeth opposed to metal and composite antagonists

One of the most important properties of artificial teeth is the abrasion wear resistance, which is determinant in the maintenance of the rehabilitation's occlusal pattern. OBJECTIVES: This in vitro study aims to evaluate the abrasion wear resistance of 7 brands of artificial teeth opposed to two types of antagonists. MATERIAL AND METHODS: Seven groups were prepared with 12 specimens each (BIOLUX & BL, TRILUX & TR, BLUE DENT & BD, BIOCLER & BC, POSTARIS & PO, ORTHOSIT & OR, GNATHOSTAR & GN), opposed to metallic (M & nickel-chromium alloy), and to composite antagonists (C & Solidex indirect composite). A mechanical loading device was used (240 cycles/min, 4 Hz speed, 10 mm antagonist course). Initial and final contours of each specimen were registered with aid of a profile projector (20x magnification). The linear difference between the two profiles was measured and the registered values were subjected to ANOVA and Tukey's test. RESULTS: Regarding the antagonists, only OR (M = 10.45 ± 1.42 µm and C = 2.77 ± 0.69 µm) and BC (M = 6.70 ± 1.37 µm and C = 4.48 ± 0.80 µm) presented statistically significant differences (p < 0.05). Best results were obtained with PO (C = 2.33 ± 0.91 µm and M = 1.78 ± 0.42 µm), followed by BL (C = 3.70 ± 1.32 µm and M = 3.70 ± 0.61 µm), statistically similar for both antagonists (p>0.05). Greater result variance was obtained with OR, which presented the worse results opposed to Ni-Cr (10.45 ± 1.42 µm), and results similar to the best ones against composite (2.77 ± 0.69 µm). CONCLUSIONS: Within the limitations of this study, it may be concluded that the antagonist material is a factor of major importance to be considered in the choice of the artificial teeth to be used in the prosthesis.

Effect of fluoride-containing solutions on the surface of cast commercially pure titanium

This study evaluated the effects of fluoride-containing solutions on the surface of commercially pure titanium (CP Ti) obtained by casting. CP Ti specimens were fabricated and randomly assigned to 5 groups (n=10): group 1: stored in distilled water at 37 ± 1ºC; group 2: stored in distilled water at 37 ± 1ºC and daily immersed in 0.05 percent NaF for 3 min; group 3: stored in distilled water at 37 ± 1ºC and daily immersed in 0.2 percent NaF for 3 min; group 4: stored in distilled water at 37 ± 1ºC; and immersed in 0.05 percent NaF every 15 days for 3 min; and group 5: stored in distilled water at 37 ± 1ºC and immersed in 0.2 percent NaF every 15 days for 3 min. Surface roughness was measured with a profilometer immediately after metallographic polishing of the specimens (T0) and at 15-day intervals until completing 60 days of experiment (T15, T30, T45, T60). Data were analyzed statistically by ANOVA and Tukey's test (α=0.05). There was no statistically significant difference (p>0.05) in surface roughness among the solutions. In conclusion, fluoride-containing solutions (pH 7.0) used as mouthwashes do not damage the surface of cast CP Ti and can be used by patients with titanium-based restorations.

Este estudo avaliou o efeito de soluções para enxaguatório bucal contendo fluoreto sobre a superfície do titânio comercialmente puro (cp Ti) após fundição odontológica. As amostras (n=50) foram divididas igualmente: grupo A - armazenadas em água destilada a 37 ± 1ºC, grupo B - armazenadas em água destilada a 37 ± 1ºC e imersão diária em NaF a 0,05 por cento durante 3 min, grupo C - armazenadas em água destilada a 37 ± 1ºC e imersão diária em NaF a 0,2 por cento durante 3 min, grupo D - armazenadas em água destilada a 37 ± 1ºC e imersão em NaF a 0,05 por cento a cada 15 dias por 3 min e grupo E - armazenadas em água destilada a 37 ± 1ºC e imersão em NaF a 0,2 por cento a cada 15 dias durante 3 min. A rugosidade superficial foi medida logo após o polimento metalográfico das amostras (T0) e cada 15 dias de experiência até serem alcançados 60 dias (T15, T30, T45, T60). Os dados foram analisados usando ANOVA (α=0,05) e as diferenças não foram estatisticamente significantes (p>0,05) entre as diferentes soluções. Conclui-se que soluções contendo fluoreto (pH 7,0) não danificam a superfície do Ti cp e podem ser usadas como soluções para bochecho usadas por pacientes que possuem restaurações à base de titânio.

Effect of laser welding on the titanium composite tensile bond strength

The aim of this study was to analyze the shear bond strength between commercially pure titanium, with and without laser welding, after airbone-particle abrasion (Al2O3) and 2 indirect composites. Sixty-four specimens were cast and divided into 2 groups with and without laser welding. Each group was divided in 4 subgroups, related to Al2O3 grain size: A - 250 µm; B - 180 µm; C- 110 µm; and D - 50 µm. Composite rings were formed around the rods and light polymerized using UniXS unit. Specimens were invested and their shear bond strength at failure was measured with a universal testing machine at a crosshead speed of 2.0 mm/min. Statistical analysis was carried out with ANOVA and Tukey's test (á=0.05). The highest bond strength means were recorded in 250 µm group without laser welding. The lowest shear bond strength means were recorded in 50 µm group with laser welding. Statistically significant differences (p<0.05) were found between all groups. In conclusion, airborne particle abrasion yielded significantly lower bond strength as the Al2O3 particle size decreased. Shear bond strength decreased in the laser welded specimens.

O objetivo deste estudo foi analisar a força de união entre o titânio comercialmente puro com solda e sem solda modificado por partículas de óxido de alumínio (Al2O3) e duas resinas indiretas. Um total de 64 espécimes foram fundidas e divididas em dois grupos sem solda e com solda a laser. Cada grupo foi novamente divididos em 4 subgrupos, de acordo com o tamanho de partículas de óxido de alumínio utilizado: A - Al2O3 (250 µm); B - Al2O3 (180 µm); C- Al2O3 (110 µm); D - Al2O3 (50 µm). Anéis de resina foram polimerizados ao redor das hastes de titânio no equipamento UniXS. Os espécimes foram embutidos em gesso e a força de união foi mensurada com auxílio da máquina de ensaios universais. ANOVA e teste de Tukey (p<0,05) foram utilizados para análise estatística. Os maiores valores de força de união foram registrados no grupo de 250 µm sem solda a laser. Os menores valores foram registrados para o grupo de 50 µm com solda a laser. Alterações estatisticamente significantes foram observadas entre todos os grupos (p<0,05). As forças de união diminuíram significantemente com a diminuição dos tamanhos das partículas de óxido de alumínio. A força de união diminuiu nas amostras que receberam a solda a laser.

Comparative study of chemical and mechanical retentive systems for bonding of indirect composite resin to commercially pure titanium

This study evaluated the effect of chemical and mechanical surface treatments for cast metal alloys on the bond strength of an indirect composite resin (Artglass) to commercially pure titanium (cpTi). Thirty cylindrical metal rods (3 mm diameter x 60 mm long) were cast in grade-1 cpTi and randomly assigned to 6 groups (n=5) according to the received surface treatment: sandblasting; chemical treatment; mechanical treatment - 0.4 mm beads; mechanical treatment - 0.6 mm beads; chemical/mechanical treatment - 0.4 mm; and chemical/mechanical treatment - 0.6 mm beads. Artglass rings (6.0 mm diameter x 2.0 mm thick) were light cured around the cpTi rods, according manufacturer's specifications. The specimens were invested in hard gypsum and their bond strength (in MPa) to the rods was measured at fracture with a universal testing machine at a crosshead speed of 2.0 mm/min and 500 kgf load cell. Data were analyzed statistically by one-way ANOVA and Tukey test (a=5 percent). The surface treatments differed significantly from each other (p<0.05) regarding the recorded bond strengths. Chemical retention and sandblasting showed statistically similar results to each other (p=0.139) and both had significantly lower bond strengths (p<0.05) than the other treatments. In conclusion, mechanical retention, either associated or not to chemical treatment, provided higher bond strength of the indirect composite resin to cpTi.

Este estudo avaliou o efeito de tratamentos de superfície químico e mecânico para ligas metálicas fundidas sobre a resistência de união de uma resina composta indireta (Artglass) ao titânio comercialmente puro (Ti cp). Trinta varetas cilíndricas metálicas (3 mm diâmetro x 60 mm comprimento) foram fundidas em Ti cp grau 1 e igualmente divididas em grupos de acordo com os seguintes tratamentos de superfície: jateamento, químico, mecânico com esferas de 0,4 mm, mecânico com esferas de 0,6 mm, químico/mecânico com esferas de 0,4 mm e químico/mecânico com esferas de 0,6 mm. Anéis de Artglass (6 mm diâmetro X 2 mm espessura) foram fotopolimerizados ao redor das varetas, de acordo com as recomendações do fabricante. Os corpos-de-prova foram embutidos em gesso-pedra e a resistência de união (MPa) foi medida em uma máquina universal de ensaios com velocidade de 2,0 mm/min e célula de carga de 500 kgf. Os dados foram analisados estatisticamente por ANOVA a um critério e teste de Tukey (a=5 por cento). Houve diferença estatisticamente significante (p<0,05) entre os tratamentos de superfície quanto à resistência adesiva. Retenção química e jateamento apresentaram resultados estatisticamente semelhantes (p=0,139), e ambos apresentaram menores valores de retenção que os demais tratamentos (p<0,05). Em conclusão, a retenção mecânica, associada ou não a tratamento químico, apresentou melhores resultados de resistência adesiva do compósito indireto ao Ti cp.