Effect of bleaching on shear bond strength to dentin of etch-and-rinse and self-etching primer adhesives.

This study evaluated in vitro the influence of enamel bleaching on bond strength to dentin. One hundred and twenty bovine incisors were divided into 12 groups (n = 10), according to adhesive system: Adper Single Bond 2 (ASB2), Prime & Bond 2.1 (PB), Adhese (AD) and Clearfil SE Bond (SE). The experimental groups were exposed to 10% carbamide peroxide for 4 hours a day over a period of 10 days. After the bleaching, they remained stored in artificial saliva for a further 24 hours or 7 days. The control groups were stored in artificial saliva for 24 hs. Resin composite (Z250) cylinders were made, and the specimens were stored in distilled water (37 degrees C/24 h), until the shear strength test was performed. The results were statistically analyzed using ANOVA 3-way and Turkey's test (a < 0.05). The highest mean value of experimental groups was obtained for ASB2 (7 d) and the lowest for PB (24 h). Significant differences were observed for bleaching and adhesive system, but not for storage time. Moreover, the interaction between the factors under study was shown to be significant. Statistical differences were observed between the tested adhesives for the different bleaching situations and storage times. It may be concluded that dental enamel bleaching and storage time in artificial saliva interfered with the bond strength to subjacent dentin provided by the Prime & Bond 2.1 and Clearfil SE Bond.

Influence of antioxidants on stress of bonding agents in recently whitened teeth.

The aim of this study was to evaluate the influence of time of application of antioxidant agents on the bond strength to bovine enamel after bleaching by light emitting diode. Twenty two bovine incisors were used, on which the vestibular surfaces were flattened and divided into four experimental groups (n = 15) according to each antioxidant agent, with two groups each, varying the application time of 1 or 10 minutes, all submitted to the same whitening agent (Lase Peroxide) and the control group was only restored. The other groups were treated with antioxidant agents before the restorative procedure using the adhesive system All Bond 3 and resin Filtek Z-350. To obtain the dental fragments, teeth were placed in a precision cutter (Elquip), obtaining 0.8 mm 2 with sticks that were submitted to micro tensile testing at a test speed of 0.5 mm/min. The results, statistically analyzed by ANOVA and Tukey test (p < 0.05), indicated an increase in the value of bond strength of bleached groups treated with ascorbic acid, and a reduction when combined with sodium thiosulfate. No improvement in bond strength was found in the others.

Resistência à fratura de dentes reforçados com pinos pré-fabricados utilizando diferentes agentes cimentantes / Resistance to fracture of teeth reinforced with different pre-fabricated posts, using different cementing agents

O estudo comparou in vitro a resistência à fratura em dentes tratados endodonticamente reforçados com pinos intra-radiculares pré-fabricados, utilizando diferentes agentes cimentantes. Cinquenta dentes humanos permanentes unirradiculares obturados, foram divididos em 5 grupos: G I-controle (sem pino); G II- pino de fibra de carbono + cimento Rely X; G III- pino de fibra de carbono + cimento Enforce; G IV- pino de fibra de vidro + cimento Rely X; G V- pino de fibra de vidro + cimento En-force. Após cimentação dos pinos e restauração coronal, as raízes foram incluídas em resina acrílica quimicamente ativada e submetidos à carga de compressão em uma Máquina Universal de Ensaios (Instron 5582). Os dados obtidos foram analisados estatisticamente pelos testes Exato de Fisher e o teste F (ANOVA), a um nível de signifcância de 5,0%, os quais demonstraram que em relação ao local da interface no grupo total, a maioria (67,5%) das amostras teve fratura na interface dente/agente cimentante; destacou-se também que a freqüência de fraturas no dente/agente cimentante variou de 4 (grupo V) a 10 (grupo III), diferenças estas significante entre os grupos. Concluiu-se que o uso dos pinos pré-fabricados não proporcionou aumento na resistência dos dentes tratados endodonticamente; o pino de fibra de vidro em associação ao sistema Enforce mostrou-se superior na resistência à fratura, sendo estatisticamente signifcante quando comparado ao grupo Enforce / pino de fibra de carbono; em relação à resistência de união, o maior comprometimento se deu na interface agente cimentante/dente quando comparada ao agente cimentante/pino.

The study compared in vitro the resistance to fracture of teeth endodontically treated reinforced with prefabricated intra-radicular posts, cemented with diferent cementation agents. Fifty permanents human teeth which had only one root was filled and divided in five groups: G I- control (without pin); G II carbon-fiber post + Rely X cement; G III carbon-fiber post + Enforce cement; G- IV fiber core post + Rely-X cement; G-V f- ber core post + Enforce cement. After cementation of this posts and coronal restoration, the root was included in self-activated acrylic resin and was submited to compressive axial loading in a Universal Testing Machine (Instron 5582). The results were statistically analyzed by Exato de Fisher test and test F (ANOVA), with 5,0 % signifcance, which demonstrated that in relation to the interface place in the total group, the majority (67,5%) of the samples had fracture on interface tooth/cementation agent ; the frequency of fractures on teeth/cementation agent varied from 4 (group V) to 10 (group III), and these diferences were significant among the groups. It was concluded that the use of prefabricated intra radicular posts couldn´t intensify the resistance of endodontically treated teeth; fiber core post associated to Enforce cement was more resistant to fracture, and statistically significant than carbon-fiber post and Enforce cement group. About bond strength the interface cement agent/teeth was less resistant than cement agent/pin.