Effect of the layering technique on bond strength and cohesive resistance of a porcelain-zirconia system.

PURPOSE: To evaluate the influence of the number of porcelain layers on its cohesive strength and on bonding to zirconia. MATERIALS AND METHODS: Y-TZP blocks were cut into 1 cm3 specimens (n = 30). The feldspathic porcelain (V9) was applied to the zirconia in different numbers of layers up to 1 cm total thickness (n = 10): ZP1 - one layer; ZP2 - two layers; ZP3 - three layers. Ten specimens with V9 were prepared following the same protocols of groups 1 (P1) and 3 (P3). All study specimens were sintered three times. The specimens were cut into 1 mm2 microbars and tested under tension in a universal testing machine (0.5 mm/min). We calculated strength (σ, in MPa) by dividing the fracture load (N) by the fractured area (mm2). The failure mode was classified as cohesive (used to calculate the cohesive strength, σc) or adhesive (bond strength, σa). The data were analyzed by Kruskal-Wallis and Dunn's tests (α = 0.05) or ANOVA and Tukey's test (α = 0.05), according to their distribution parameters. RESULTS: The ZP1 group presented the highest values for σa data, compared with other groups, which were statistically similar. The predominant failure mode for the bonded specimens was cohesive. With regard to the cohesive strength (σc), ZP1 presented the highest values. CONCLUSION: It can be concluded that the presence of more than one porcelain layer decreases its cohesive strength and its bonding strength to zirconia.

Fracture resistance of composite resin cores with or without prefabricated posts over different substrates.

The fracture resistance of endodontically treated teeth has been an obstacle to the durability of the remaining teeth and restorations. The aim of this study was to evaluate the fracture resistance of endodontically treated bovine and human teeth that were restored with either prefabricated metal posts, glass fiber posts, or composite resin cores. Statistical analysis revealed significant difference between different substrates, but there was no statistically significant difference between different types of intraradicular posts or in the interaction between substrate and post types. The intraradicular posts do not increase the fracture resistance of endodontically treated teeth. The metal posts presented more unfavorable fracture modes when compared to glass fiber posts and composite resin cores.

Effect of Air-Particle-Abrasion Protocols on Surface Roughness and Early Biofilm Formation of Zirconia.

PURPOSE: The air-particle-abrasion on zirconia in the gingival area of connectors and pontics in fixed partial dentures appears to increase fracture resistance. This study evaluated 'in situ' biofilm formation on the zirconia surface after different air-particle-abrasion protocols. MATERIALS AND METHODS: Ninety sintered blocks (5 × 5 × 2 mm) of yttrium partially stabilised zirconia (Y-TZP) were obtained and randomised among nine groups according to the factors 'type of particle' (Alumina 50 and 110 µm; Cojet and Rocatec) and 'pressure' (2.5 and 3.5 bar) used for sandblasting for 10 s. The surface roughness (Ra/Rz) was measured before and after sandblasting. For the in-situ analyses, custom-made removable intraoral devices n = 10 with one sample of each group attached to the buccal area were used by volunteers for 8 h at night. The specimens were analysed under confocal microscopy to quantify both biovolume and thickness of the initial biofilm formed. One-way analysis of variance (ANOVA) and Dunnett's tests were performed (5%). RESULTS: The roughness values ranged from 0.05 to 0.39 µm for Ra and from 0.35 to 2.11 µm for Rz, p = 0.00. Mean biofilm thickness ranged from 0.06 and 0.54 µm (p = 0.005), while the biovolume values were between 0.02 and 0.61 µm3/µm2 (p = 0.002). Values statistically significant for biofilm thickness and biovolume were found in groups sandblasted with Rocatec using 3.5 bar. CONCLUSION: In order to increase the fracture resistance of zirconia fixed partial dentures (FPDs), the air particle abrasion of zirconia with SiO2 (110 µm/3.5 bar), in the gingival area of connectors and pontics, should be avoided.

Influence of indirect reinforcements on the flexural strength of a thermally activated acrylic resin used for complete dentures / Influência de reforços indiretos na resistência a flexão de uma resina acrílica ativada térmicamente utilizada na confecção de próteses totais

Objective: This research aimed to verify the performance of thermally activated acrylic resin (TAAR) combined with a mix of glass and aramid fibers and/or composite resin of indirect use by a tree point bending test. Material and Methods: Ten samples, with 65 x 10 x 2.5 mm, were prepared for each group (n = 10): CO, control of only TAAR; CR, in which an 60 mm indirect composite resin was polymerized together with the acrylic resin during the thermo-polymerization cycle; SS, in which ceramic glass mixed with aramid fibers cut 60 mm in length were incorporated into the samples; and SC, in which the same fibers were incorporated with addiction of the indirect composite resin. A three point flexural strength test was performed with a universal testing machine with a load of 50KgF at a speed of 5 mm/min in the center of the samples supported by a suitable device. The reinforced face was placed to the tensile side. The statistical one way ANOVA and Tukey tests were made with a significance level of 95%. Results: The mean value for the CO was 60,27 ± 24,18 MPa, for CR it was 38,39±12,75 MPa, for SS it was 79,97±12,75 Mpa and for CS it was 32,40±9,05 MPa. Conclusion: The use of glass and aramid fibers at the base of a TAAR increased the three-point flexural strength, however when indirect composite resin was incorporated, a significant drop of this mechanical property was observed. (AU)

Objetivo: Esta pesquisa teve como objetivo verificar o desempenho de uma resina acrílica ativada termicamente (RAAT) combinada com uma mistura de fibras de vidro e aramida e / ou resina composta de uso indireto por um teste de flexão de três pontos. Material e Métodos: Foram preparadas dez amostras, com 65 x 10 x 2,5 mm, para cada grupo (n = 10): CO, controle com apenas RAAT; CR, em que uma resina composta indireta de 60 mm com polimerizada em conjunto com a resina acrílica durante o ciclo de termopolimerização; SS, em que o vidro cerâmico misturado com fibras de aramida cortadas com 60 mm de comprimento foi incorporado nas amostras; e SC, nas quais as mesmas fibras foram incorporadas em conjunto com a resina composta indireta. O teste de resistência à flexão de três pontos foi realizado em uma máquina de teste universal com uma carga de 50 KgF a uma velocidade de 5 mm/min no centro das amostras suportadas por um dispositivo adequado. A face reforçado foi colocado no lado da tração. Os testes estatísticos one-way ANOVA e Tukey foram feitos com um nível de significância de 95%. Resultados: O valor para o CO foi de 60,27 ± 24,18 MPa, para CR foi de 38,39 ± 12,75 MPa, para SS foi de 79,97 ± 12,75 Mpa e para CS foi de 32, 40 ± 9,05 MPa. Conclusão: o uso de fibras de vidro e aramida na base de uma RAAT aumentou a resistência à flexão de três pontos, no entanto, quando a resina composta indireta foi incorporada, observou-se uma queda significativa dessa propriedade mecânica (AU)

Electromyographic activity in patient with an inferior implant/tooth-supported overdenture: clinical report / Atividade eletromiográfica de um paciente com prótese inferior implantodentossuportada: Relato de caso clínico

Clinicians can find patients with one mandibular remaining tooth, and it is difficult to decide if the tooth has to be removed. When a clinician decides to maintain the tooth, it is common to question the masticatory load distribution divided between the tooth and implant. This paper reports a clinical case of patient with an implant/tooth-supported overdenture and elucidates the masticatory efficiency by electromyography activity analysis. The objective of this case report was to describe a clinical case of a patient with an implant/tooth-supported overdenture and to discuss the muscle response to this treatment. Electrical activities of the masseter and anterior temporal surfaces at maximum voluntary contraction were evaluated by electromyography during pre-treatment, immediately post-treatment,15 and 60 days after installation. When patienthas one remaining tooth in good condition, theimplant/tooth-supported overdenture can be recommended, to preserve the periodontal ligament and proprioception, and to minimize bone loss. Electromyography analysis showed that implant/tooth-supported overdenture is a viable treatment alternative, in muscular stand point, when the patient has a remaining tooth with good osseous support...

Os dentistas podem encontrar casos em que o paciente possui apenas um dente mandibular remanescente,sendo difícil decidir se o dente deverá ser extraído. Quando o clínico decide manter este dente, é comum surgirem dúvidas sobre como ocorre a distribuição da carga mastigatória em próteses suportadas por dente e implante. Este artigo relata a resposta muscular por meio de atividade eletromiográfica de um paciente reabilitado com uma prótese inferior implantodentossuportada. O objetivo deste artigo foi descrever este caso clínico e discutir a resposta musculatória neste tipo de tratamento. As atividades eletromiográficas dos músculos massetere temporal anterior superficial foram avaliadas durante o pré-tratamento, imediatamente após a instalação da prótese, 15 e 60 dias pós-tratamento.Foi verificado que quando o paciente tem um dente remanescente em condição de ser mantido, a prótese implantodentossuportada pode ser recomendada como tratamento, para preservação do ligamento periodontal e da propriocepção, e para minimizar a perda óssea. A análise eletromiográfica demonstrou que a prótese implantodentossuportada é uma alternativa viável de tratamento, do ponto de vista muscular, quando o paciente possui um dente remanescente com suporte ósseo adequado...

Effect of cement type, relining procedure, and length of cementation on pull-out bond strength of fiber posts.

INTRODUCTION: As opposed to the cementation metal posts, the cementation of fiber posts has several details that can significantly influence the success of post retention. This study evaluated the effect of the relining procedure, the cement type, and the luted length of the post on fiber posts retention. METHODS: One hundred eighty bovine incisors were selected to assess post retention; after endodontic treatment, the canals were flared with diamonds burs. Post holes were prepared in lengths of 5, 7.5, and 10 mm; the fiber posts were relined with composite resin and luted with RelyX ARC, RelyX Unicem, or RelyX Luting 2. All cements are manufactured by 3M ESPE (St. Paul, MN). Samples were subjected to a pull-out bond strength test in a universal testing machine; the results (N) were submitted to a three-way analysis of variance and the Tukey post hoc test (alpha = 0.05). RESULTS: The improvement of post retention occurred with the increase of the post length luted into the root canal; the relining procedure improved the pull-out bond strength. RelyX Unicem and RelyX ARC showed similar values of retention, both showing higher values than RelyX Luting 2. CONCLUSION: Post length, the relining procedure, and the cement type are all important factors for improving the retention of fiber posts.

May the flexural strength of ceramics be influenced by salivary pH? / A resistência à flexão de cerâmicas pode ser influenciada pelo pH salivar?

Objective: This study purpose was to compare the three-point flexural strength of feldspathic ceramic after storage in artificial saliva for 30 days with different pH regimens, as acidic pH (3.5), neutral pH (7.0), basic pH (10) and alternating between acid/ basic pH, for 15 days each. Material and Methods: The bars were luted with resin cement and subjected to storage in artificial saliva of different pH values. Results: The values of flexural strength were significantly higher for bars stored in distilled water, at neutral and basic pH, when compared with the results for bars stored in acidic pH and in acid/basic pH. Conclusions: Storage for 30 days in artificial saliva at acidic pH, or alternating between acidic and basic pH, can reduce the mechanical properties of ceramics.

Objetivo: O objetivo do estudo foi comparar a resistência à flexão três pontos de uma cerâmica feldspática após armazenagem em saliva artificial, durante 30 dias com diferentes regimes de pH: pH ácido (3,5), pH neutro (7,0), pH básico (10) e alternando entre pH ácido/básico durante 15 dias cada. Material e Métodos: As barras foram cimentados com cimento resinoso e submetidas a armazenagem em saliva artificial com os diferentes valores de pH. Resultados: Os valores de resistência à flexão foram significativamente maiores para as barras armazenadas em água destilada, em pH neutro e em básico, quando comparadas com os resultados para as barras armazenadas em pH ácido e em meio ácido/básico. Conclusões: A armazenamento durante 30 dias em saliva artificial, com pH ácido, ou alternando entre pH ácido e basico, pode reduzir as propriedades mecânicas das cerâmicas

Efeito de diferentes tempos de condicionamento e condições de envelhecimento na resistência à flexão de cerâmicas ácido sensíveis / Effect of different times of conditioning and storage conditions on the flexural strength of acid-sensitive ceramics

As cerâmicas são indicadas para coroas livres de metal, pois alcançaram resistência suficiente para resistir às cargas funcionais. O objetivo neste estudo foi avaliar a resistência à flexão de barras cerâmicas, após diferentes tempos de condicionamento com ácido fluorídrico, e diferentes protocolos de envelhecimento. Foram confeccionadas 500 barras cerâmicas com dimensões de 16 mm x 4 mm x 2 mm, sendo 250 para cada tipo de cerâmica. As barras foram lixadas e polidas e distribuídas em 5 grandes grupos com 50 amostras cada e foram condicionadas com ácido fluorídrico a 10%, variando os tempos de condicionamento entre 20, 30, 40, 60 e 90 segundos. Posteriormente, foi aplicado o agente silano e uma camada fina de cimento resinoso dual. Foram então subdivididas em 5 diferentes meios de envelhecimento: termociclagem, ciclagem mecânica, ciclagem termomecânica, ciclagem intra-bucal e controle. Após os ciclos, as amostras foram submetidas ao teste de resistência à flexão, em uma máquina de ensaio universal EMIC, com velocidade de 1mm/min. Os valores médios forma submetidos a análise estatística ANOVA 2 fatores e comparação de Tukey 5%. Para a cerâmica feldspática tanto o grupo controle quanto o grupo submetido à ciclagem termomecânica apresentaram valores mais homogêneos em relação ao tempo de condicionamento. No grupo submetido à ciclagem mecânica, houve um aumento da resistência quando condicionado por 90 segundos. No grupo ciclado termicamente houve uma queda nos valores de resistência quando condicionados por 40 segundos, e no grupo intra-bucal, uma queda quando condicionados por 60 segundos. Uma expressiva diferença foi encontrada entre os grupos condicionados por 40 e 60 segundos, ambos submetidos à ciclagem intra-bucal. Para a cerâmica de dissilicato de lítio o maior valor de resistência à flexão foi obtido no grupo controle, condicionado por 90 segundos. Os menores valores de resistência à flexão foram encontrado nos grupos submetidos...

Ceramics can be indicated for metal free crowns, since they have reached sufficient strength to withstand functional loads. The objective of this study was to evaluate the flexural strength of feldspathic bars and lithium disilicate, after different times of etching with hydrofluoric acid, and different protocols of aging. Five hundred bars (16 mm x 4 mm x 2 mm) were prepared, 250 for each type of ceramic. The bars were grounded, polished and distributed in 5 groups of 50 samples each and were etched with 10% hydrofluoric acid, varying the conditioning time (20, 30, 40, 60 and 90 seconds). Subsequently, the silane agent was applied followed by a thin layer of dual resin cement. Samples were then divided into five different ways of aging: thermal cycling, mechanical cycling, thermomechanical cycling, intra-oral cycling and control. After the cycles, the samples were subjected to flexural strength testing in a universal testing machine (EMIC), at a speed of 1 mm / min. Mean values were submitted to two-way ANOVA and Tukey test (á =5%). Both feldspathic ceramic control group and the group submitted to thermomechanical cycling showed more homogeneity regarding the conditioning time. In the group submitted to mechanical loading, there was an increase in the resistance when conditioning for 90 seconds. The thermally cycled group presented decrease in the strength values when conditioned for 40 seconds, and the intra-oral group, a decrease when conditioned for 60 seconds. The most significant difference was found between the groups conditioned for 40 and 60 seconds, both when submitted to intra-oral cycling. For lithium disilicate ceramic, the highest value of flexural strength was obtained in the control group, conditioned for 90 seconds. The lower values of flexural strength were found in groups submitted to intra-oral cycling, conditioned by 30 and 40 seconds...

Efeito de diferentes tempos de condicionamento e condições de envelhecimento na resistência à flexão de cerâmicas ácido sensíveis / Effect of different times of conditioning and storage conditions on the flexural strength of acid-sensitive ceramics

As cerâmicas são indicadas para coroas livres de metal, pois alcançaram resistência suficiente para resistir às cargas funcionais. O objetivo neste estudo foi avaliar a resistência à flexão de barras cerâmicas, após diferentes tempos de condicionamento com ácido fluorídrico, e diferentes protocolos de envelhecimento. Foram confeccionadas 500 barras cerâmicas com dimensões de 16 mm x 4 mm x 2 mm, sendo 250 para cada tipo de cerâmica. As barras foram lixadas e polidas e distribuídas em 5 grandes grupos com 50 amostras cada e foram condicionadas com ácido fluorídrico a 10%, variando os tempos de condicionamento entre 20, 30, 40, 60 e 90 segundos. Posteriormente, foi aplicado o agente silano e uma camada fina de cimento resinoso dual. Foram então subdivididas em 5 diferentes meios de envelhecimento: termociclagem, ciclagem mecânica, ciclagem termomecânica, ciclagem intra-bucal e controle. Após os ciclos, as amostras foram submetidas ao teste de resistência à flexão, em uma máquina de ensaio universal EMIC, com velocidade de 1mm/min. Os valores médios forma submetidos a análise estatística ANOVA 2 fatores e comparação de Tukey 5%. Para a cerâmica feldspática tanto o grupo controle quanto o grupo submetido à ciclagem termomecânica apresentaram valores mais homogêneos em relação ao tempo de condicionamento. No grupo submetido à ciclagem mecânica, houve um aumento da resistência quando condicionado por 90 segundos. No grupo ciclado termicamente houve uma queda nos valores de resistência quando condicionados por 40 segundos, e no grupo intra-bucal, uma queda quando condicionados por 60 segundos. Uma expressiva diferença foi encontrada entre os grupos condicionados por 40 e 60 segundos, ambos submetidos à ciclagem intra-bucal. Para a cerâmica de dissilicato de lítio o maior valor de resistência à flexão foi obtido no grupo controle, condicionado por 90 segundos. Os menores valores de resistência à flexão foram encontrado nos grupos submetidos...

Ceramics can be indicated for metal free crowns, since they have reached sufficient strength to withstand functional loads. The objective of this study was to evaluate the flexural strength of feldspathic bars and lithium disilicate, after different times of etching with hydrofluoric acid, and different protocols of aging. Five hundred bars (16 mm x 4 mm x 2 mm) were prepared, 250 for each type of ceramic. The bars were grounded, polished and distributed in 5 groups of 50 samples each and were etched with 10% hydrofluoric acid, varying the conditioning time (20, 30, 40, 60 and 90 seconds). Subsequently, the silane agent was applied followed by a thin layer of dual resin cement. Samples were then divided into five different ways of aging: thermal cycling, mechanical cycling, thermomechanical cycling, intra-oral cycling and control. After the cycles, the samples were subjected to flexural strength testing in a universal testing machine (EMIC), at a speed of 1 mm / min. Mean values were submitted to two-way ANOVA and Tukey test (á =5%). Both feldspathic ceramic control group and the group submitted to thermomechanical cycling showed more homogeneity regarding the conditioning time. In the group submitted to mechanical loading, there was an increase in the resistance when conditioning for 90 seconds. The thermally cycled group presented decrease in the strength values when conditioned for 40 seconds, and the intra-oral group, a decrease when conditioned for 60 seconds. The most significant difference was found between the groups conditioned for 40 and 60 seconds, both when submitted to intra-oral cycling. For lithium disilicate ceramic, the highest value of flexural strength was obtained in the control group, conditioned for 90 seconds. The lower values of flexural strength were found in groups submitted to intra-oral cycling, conditioned by 30 and 40 seconds....(AU)