Avaliação do substrato dentinário irradiado com laser de Er:YAG : resistência de união, padrão de fratura e análise ultramorfológica / Evaluation of dentin irradiated with Er:YAG laser : bond strength, failure pattern and ultramorphology analysis

AUTOR(ES)
DATA DE PUBLICAÇÃO

2011

RESUMO

The Er:YAG laser has been widely used in Dentistry and because its ability to remove mineralized dental tissues, it is indicate to be used in Operative Dentistry. As the Er:YAG laser is recent, little is known about the consequences of dental tissues irradiation and their effects on adhesive restorative procedures. Thus, the objectives of this study were to evaluate the effects of two parameters of Er:YAG laser irradiation (250mJ/4Hz e 160 mJ/10Hz) on dentin bond strength (BS) of adhesive systems and measure, in depth, the effects promoted by laser irradiation. Additionally, the bonded interface area was analyzed under transmission electron microscopy (TEM). The experiments were performed on occlusal dentin surfaces of third molars that were flattened with sandpaper SiC (600). The adhesive systems used were: XP Bond (Dentsply De Trey), Clearfil SE Bond (Kuraray Medical) and Adper SE Plus (3M ESPE). For the evaluation of BS it was used the microtensile method and the fracture patterns of tested specimens were analyzed using the Scanning electron microscopy (SEM). The TEM was used for evaluation of bonded interfaces ultramorphology and to measure the depth of the effects produced by the laser irradiation. The control groups for the BS test and TEM observations were the adhesive application to non-irradiated surfaces. The Bs data were analyzed by two-way ANOVA and Tukey test (5%). The BS of adhesives for the control group was similar. The XP Bond adhesive showed similar BS between control group and irradiated groups, with no reduction on BS on irradiated dentin. Irradiation parameters produced similar effects of adhesive systems on BS to dentin, except for the Clearfil SE Bond under 160 mJ/10Hz , which did not differ from XP Bond. The failure pattern examination under SEM showed predominance of mixed fracture and for the TEM observations, the control groups presented hybrid layer formation with thickness varying between 1.0 and 3.0 ?m. For the irradiated groups, it was no possible to observe a uniform hybrid layer. The measurements of depth of the laser effects, it was used the Student T test that did not indicate statistical difference between laser parameters (250mJ/4Hz: 5.8 ?m ± 2.1 e 160 mJ/10Hz: 6.1 ?m ± 1.2). The results suggested that the dentin irradiation with Er:YAG laser may reduce the BS, depending on the adhesive system. The hybrid layer formation was compromised when the dentin was irradiated, independent on laser parameter used. The measurements of depth of the laser ablation effects did not differ, indicating that the laser parameters can affect the adhesive restorative procedures similarly.

ASSUNTO(S)

microscopia eletrônica de varredura microscopia eletrônica de transmissão adesivos dentinários dentina scanning electron microscope scanning electron transmission dentin-bonding agents dentin

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