Effect of storage and aging conditions on the flexural strength and flexural modulus of CAD/CAM materials.

Computer-aided design/computer-aided manufacturing (CAD/CAM) materials were submitted to thermocycling, to identify changes in mechanical behavior. Four CAD/CAM materials were divided in four subordinate groups (n=9): (1) dry out for 7 days, (2) distilled water at 37oC for 7 days, (3) 60,000 thermocycles, and (4) 120,000 thermocycles. Following thermocycling, samples were submitted to three-point bending test. Two-way ANOVA and post-hoc Tukey's test were performed (α=0.05). The IPS e.max CAD had a flexural strength of 396±75 MPa and flexural modulus of 84±11 GPa, followed by Vita Enamic with values of 153±17 MPa and 28±5 GPa respectively. The flexural strength recorded for Lava Ultimate was 149±28 MPa and the flexural modulus was 12±3 GPa. Vitablocs Mark II had the lowest flexural strength values (125±10 MPa) and a flexural modulus of 49±15 GPa. Although polymer-based materials have similar mechanical properties compared to ceramics, they are affected by thermo cycling conditions.

Microtensile bond strength between a UDMA fiber post and different resin cements: Effect of pre-surface treatment.

During a fiber post cementation, bonding failure often occurs at the junction between the fiber-post and resin-cement. Because this failure requires better characterization, we evaluated if different post surface treatment can affect the bond strength of urethane dimethacrylate (UDMA) fiber-posts with resin-cements. Three groups were created: G1: no treatment/silane; G2: ethyl alcohol (96° GL)/silane; G3: 24% H2O2/silane and further divided into four subgroups: I-Unicem/3MESPE; II-BisCem/Bisco; III-Panavia SA/Kuraray and IV-DuoLink/Bisco. Blocks of cured resin cements and posts placed in the center were serially cut into bar-shaped specimens and loaded into a micro tensile testing machine. ANOVA indicated no significant differences among post surface treatments (p>0.05), however, significant within the resin cements (p<0.05) and the interaction of both (p<0.05). The G3/IV showed the highest bond strength values. SEM showed that surface treatments on UDMA fiber posts presented no benefits in terms of surface roughness, thus, should not be performed.

Effect of temporary cements on the shear bond strength of luting cements.

OBJECTIVE: The purpose of this study was to evaluate, by shear bond strength (SBS) testing, the influence of different types of temporary cements on the final cementation using conventional and self-etching resin-based luting cements. MATERIAL AND METHODS: Forty human teeth divided in two halves were assigned to 8 groups (n=10): I and V (no temporary cementation); II and VI: Ca(OH)2-based cement; III and VII: zinc oxide (ZO)-based cement; IV and VIII: ZO-eugenol (ZOE)-based cement. Final cementation was done with RelyX ARC cement (groups I to IV) and RelyX Unicem cement (groups V to VIII). Data were analyzed statistically by ANOVA and Tukey's test at 5% significance level. RESULTS: Means were (MPa): I - 3.80 (+/-1.481); II - 5.24 (+/-2.297); III - 6.98 (+/-1.885); IV - 6.54 (+/-1.459); V - 5.22 (+/-2.465); VI - 4.48 (+/-1.705); VII - 6.29 (+/-2.280); VIII - 2.47 (+/-2.076). Comparison of the groups that had the same temporary cementation (Groups II and VI; III and VII; IV and VIII) showed statistically significant difference (p<0.001) only between Groups IV and VIII, in which ZOE-based cements were used. The use of either Ca(OH)2-based (Groups II and VI) or ZO-based (Groups III and VII) cements showed no statistically significant difference (p>0.05) for the different luting cements (RelyX ARC and RelyX Unicem). The groups that had no temporary cementation (Groups I and V) did not differ significantly from each other either (p>0.05). CONCLUSION: When temporary cementation was done with ZO- or ZOE-based cements and final cementation was done with RelyX ARC, there was an increase in the SBS compared to the control. In the groups cemented with RelyX Unicem, however, the use of a ZOE-based temporary cement affected negatively the SBS of the luting agent used for final cementation.

Effect of temporary cements on the shear bond strength of luting cements

OBJECTIVE: The purpose of this study was to evaluate, by shear bond strength (SBS) testing, the influence of different types of temporary cements on the final cementation using conventional and self-etching resin-based luting cements. Material and Methods: Forty human teeth divided in two halves were assigned to 8 groups (n=10): I and V (no temporary cementation); II and VI: Ca(OH)2-based cement; III and VII: zinc oxide (ZO)-based cement; IV and VIII: ZO-eugenol (ZOE)-based cement. Final cementation was done with RelyX ARC cement (groups I to IV) and RelyX Unicem cement (groups V to VIII). Data were analyzed statistically by ANOVA and Tukey's test at 5 percent significance level. RESULTS: Means were (MPa): I - 3.80 (±1.481); II - 5.24 (±2.297); III - 6.98 (±1.885); IV - 6.54 (±1.459); V - 5.22 (±2.465); VI - 4.48 (±1.705); VII - 6.29 (±2.280); VIII - 2.47 (±2.076). Comparison of the groups that had the same temporary cementation (Groups II and VI; III and VII; IV and VIII) showed statistically significant difference (p<0.001) only between Groups IV and VIII, in which ZOE-based cements were used. The use of either Ca(OH)2-based (Groups II and VI) or ZO-based (Groups III and VII) cements showed no statistically significant difference (p>0.05) for the different luting cements (RelyX TM ARC and RelyX TM Unicem). The groups that had no temporary cementation (Groups I and V) did not differ significantly from each other either (p>0.05). CONCLUSION: When temporary cementation was done with ZO- or ZOE-based cements and final cementation was done with RelyX ARC, there was an increase in the SBS compared to the control. In the groups cemented with RelyX Unicem, however, the use of a ZOE-based temporary cement affected negatively the SBS of the luting agent used for final cementation.

Efeito da inserção tardia de resina composta sobre a resistência de união de sistemas adesivos convencionais / Effect of delayed insertion of composite resin on the bond strength of etch-and-rinse adhesive systems

Introdução: Sistemas adesivos convencionais são caracterizados pelo condicionamento ácido da estrutura dental previamente à aplicação dos monômeros. Esses materiais podem ser classificados em 3 passos (quando primer e adesivo se encontram em frascos separados) ou 2 passos (em que a função de primer e adesivo é desempenhada por um único material). Objetivo: Verificar a influência do momento da inserção do material restaurador (inserção imediata ou tardia) sobre os valores de resistência de união de adesivos convencionais de 2 e 3 passos por meio do teste de microtração. Material e métodos: Foram utilizados dentes incisivos bovinos que tiveram sua superfície vestibular desgastada até se obter uma superfície plana em dentina. Empregaram-se sistemas adesivos convencionais de 3 passos (Scotchbond Multi-Uso ? SMP; Optibond FL ? OFL; Bond-It ? BIT) e de 2 passos (Single-Bond ? SB; Optibond Solo Plus ? OSP; Bond-1 ? B1), e resina composta (Z-350) foi aderida a esse substrato em dois diferentes momentos: imediata e tardiamente (após 24 horas). Todos os procedimentos foram realizados com simulação da pressão pulpar fisiológica. Os resultados foram submetidos à análise estatística Anova e ao teste de Tukey (p < 0,05). Resultados: Para inserção imediata da resina composta, todos os adesivos apresentaram comportamentos semelhantes. Os sistemas adesivos de 3 passos não evidenciaram redução da resistência de união quando a resina composta foi inserida tardiamente. Já os sistemas adesivos de 2 passos tiveram sensível redução dos valores de resistência de união. A redução ficou em torno de 30,24% para SB, 27,19% para OSP e 28,21% para B1. Conclusão: Cuidado especial deve ser tomado durante o uso de sistemas adesivos convencionais de 2 passos. É aconselhável que a resina composta seja inserida e polimerizada imediatamente após a conclusão do procedimento adesivo.

Introduction: Etch-and-rinse adhesive systems are characterized by the dental acid etching previously to the monomer application. These materials can be classified as 3-step (when primer and bond are applied separately) or 2-step (when the primer and bond functions are carried out by a single component). Objective: To determine the influence of immediate or delayed insertion of restorative material on the values of bond strength of 2-step and 3-step etch-and-rinse adhesive systems using the microtensile test. Material and methods: Bovine incisors were used, which had its vestibular surface abraded to obtain a flat dentin surface. 3-step (Scotchbond Multi-Purpose ? SMP; Optibond FL ? OFL; Bond-It ? BIT) and 2-step (Single-Bond ? SB; Optibond Solo Plus ? OSP; Bond-1 ? B1) etch-and-rinse adhesive systems were used, and composite resin (Z-350) was adhered to this substrate at two different times: immediately and later (after 24 hours). Procedures were performed with simulated physiological pulpal pressure. Results were submitted to statistical analysis through Anova and Tukey?s test (p < 0.05). Results: When the composite resin was immediately inserted all the adhesive systems showed similar results. 3-step adhesive systems did not show reduction in bond strength values related to delayed insertion of composite. On the other hand, 2-step adhesive systems showed significant reduction in the values of bond strength. Reduction was around 30.24% to SB, 27.19% to OSP and 28.21% to B1. Conclusion: 2-step etch-and-rinse adhesive systems should be used very carefully. It is advisable to insert and polymerize the composite resin immediately after the conclusion of adhesive procedure.

Cuspal movement related to different bonding techniques using etch-and-rinse and self-etch adhesive systems.

OBJECTIVES: To investigate the effects of adhesion technique using different contemporary adhesive systems on the cuspal movement in class II composite restorations in human premolar teeth. METHODS: Human premolar teeth were prepared with class II cavities and then restored with composite and etch-and-rinse (Adper Scotchbond Multi Purpose and Adper Single Bond) or self-etch (Clearfil SE Bond and Clearfil S3 Bond) adhesive systems under different bonding techniques (total bonding and selective bonding). The influence of an intermediate layer of flowable composite was also evaluated. The cuspal distance was measured before and after the restorative procedure, and the difference was recorded as cuspal movement. The data were submitted to ANOVA test and Tukey's post hoc comparison procedure test (alpha=0.05). RESULTS: For all adhesive systems, the teeth restored with selective bonding technique showed lower values of cuspal movement and the use of an intermediary layer of flowable composite did not show any influence on the cuspal movement. CONCLUSIONS: Both the adhesive techniques tested were not able to prevent the cuspal movement. However, selectively bonded class II composite restorations demonstrated lower values of cuspal movement comparing with total bonding technique, and the use of an intermediate layer of flowable composite did not diminish the values of cuspal movement.

Efeito da inserção tardia de resina composta sobre a resistência de união de sistemas adesivos autocondicionantes / Effect of delayed insertion of composite resin on the bond strength of self-etching adhesive systems

Introdução: O avanço tecnológico dos sistemas adesivos fez com que surgissem materiais com técnicas simplificadas, com menor número de passos clínicos. Objetivo: Buscou-se verificar a influência do momento da inserção do material restaurador (inserção imediata ou tardia) sobre os valores de resistência de união de adesivos autocondicionantes utilizando o teste de microtração. Material e métodos: Foram usados dentes incisivos bovinos, que tiveram sua superfície vestibular desgastada até obter uma superfície plana em dentina. Empregaram-se sistemas adesivos autocondicionantes - Clearfil SE Bond (CSEB), Clearfil Tri S Bond (CTSB), AdheSE (ADS) e AdheSE One (ADO) -, e a resina composta Z350 foi aderida a esse substrato em dois diferentes momentos: imediatamente e tardiamente (após 24 horas). Todos os procedimentos foram realizados com simulação da pressão pulpar fisiológica. Os resultados foram submetidos a análise estatística empregando Anova e teste de Tukey. Resultados: Todos os materiais testados, com exceção de ADS, apresentaram redução dos valores de resistência de união quando a resina composta foi aplicada tardiamente, e apenas para os sistemas de passo único (CTSB e ADO) a redução foi estatisticamente significante. Conclusão: Cuidado especial deve ser tomado durante a utilização de sistemas adesivos autocondicionantes de passo único. É aconselhável a aplicação de uma camada adicional de material hidrofóbico com o objetivo de diminuir a permeação da camada adesiva, e a inserção da resina composta deve ser iniciada imediatamente após a fotopolimerização do sistema adesivo.

Introduction: Technological advances in adhesive systems have resulted in materials with simplified techniques, which require less clinical steps. Objective: To determine the influence of immediate or delayed insertion of restorative material on the values of bond strength self-etching adhesives by using the micro tensile test. Material and methods: Bovine incisors were used, which had its vestibular surface abraded to obtain a flat dentin surface. Self-etching adhesive systems were used: Clearfil SE Bond (CSEB), Clearfil Tri S Bond (CTSB), AdheSE (ADS) and AdheSE One (ADO). The composite resin Z350 was adhered to this substrate at two different times: immediately and later (after 24 hours). Procedures were performed with simulated physiological pulpal pressure. Results were submitted to statistical analysis through Anova and Tukey's test. Results: Except ADS, all materials tested showed reduction of the values of bond strength when composite resin was applied delayed, and only for single-step systems (CTSB and ADO) this reduction was statistically significant. Conclusion: Special care shall be taken when using single-step self-etching adhesive systems. It is recommended the application of an additional layer of hydrophobic material in order to reduce permeation of adhesive layer, and the insertion of composite resin should be initiated immediately after the photopolymerization of adhesive system.

Comparação da microdureza de resina polimerizada por diferentes LED's e luz halógena / Comparison of composite's microhardness using different LED's and halogen light

O objetivo deste trabalho foi avaliar a microdureza da resina composta polimerizada por LEDs e luz halógena. Foram usados cinco aparelhos de luz divididos em cinco grupos, Grupo I – KM 200R, Grupo II – KM 100R, Grupo III – Ultraled II, Grupo IV – Ultrablue II, e Grupo V – Ultralled III. Para cada grupo foram confeccionados quatro corpos-de-provas, polimerizados em íntimo contato com a superfície da resina por 20 segundos, utilizando uma matriz de aço de 4mm de diâmetro por 2mm de profundidade. As leituras no topo e base do corpo-de-prova foram realizadas através do microdurômetro. Aplicou-se o teste estatístico de Kolmogorov-Smirnov para verificar a normalidade e, posteriormente o teste t-Student comparando-se a dureza entre topo e base dos corpos-de-prova, de acordo com os aparelhos utilizados. A dureza dentro de cada uma das regiões entre os cinco aparelhos foi analisada pelo teste ANOVA-F, seguido pelo teste de comparação múltiplas de Tukey, ao nível de significância de 5%. Observou-se que em todos os aparelhos a dureza Vickers apresentou-se com níveis médios superiores na região do topo em relação à base, exceto quanto ao aparelho Ultrablue II, onde esta superioridade não foi estatisticamente significativa (p=0,46). Quando analisada a dureza Vickers em cada uma das duas regiões entre os cinco aparelhos, verificou-se que houve diferença significativa entre todos na base (p<0,0002), não sendo significativas estas diferenças no topo entre os aparelhos Ultrablue II e III (p=0,46). Observou-se ainda que os LEDs testados apresentaram uma dureza menor quando comparados com os aparelhos de luz halógena, onde o aparelho Ultraled apresentou menor dureza entre os LEDs comparados

Resinas condensáveis / Condensate resins

A busca de um material estético ideal para regiäo posterior da cavidade bucal, tem originado mudanças significantes nas resinas compostas com o intuito de substituir o amálgama dental. Nesta publicaçäo enfatizamos algumas mudanças nesses materiais e técnicas, Entretanto, temos que ter a consciência de que estas informaçöes necessitam de mais estudos