Influencia dos ciclos termicos e mecanicos na resistencia de união de restaurações classe II em resina composta confeccionadas com tres sistemas adesivos / Influence of thermal and mechanical load cycling on bond strength of Class II composite resin restorations using three adhesive systems

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

The aim of this study was to evaluate the influence of thermal and mechanical loading cycling on microtensile bond strength of Class II composite restorations in dentin, with three adhesive systems. One hundred and sixty eight slot vertical cavities were prepared on proximal surfaces of bovine teeth, and divided according to the adhesive system used (Single Bond, OptiBond Solo Plus, and Clearfil SE Bond). All cavities were filled with Filtek Z250 composite resin. Following restorative procedures, the teeth were once again allocated into different groups according to the thermal / mechanical treatment, thus obtaining 21 experimental groups (n=8): I - control, II - 100,000 mechanical cycles, III - 200,000 mechanical cycles, IV - 500,000 mechanical cycles, V - 100,000 mechanical cycles + 1,000 thermal cycles, VI - 200,000 mechanical cycles + 1,000 thermal cycles, VII - 500,000 mechanical cycles + 1,000 thermal cycles. Thermal cycling was performed by submitting the specimens to alternating 5o and 55oC baths, with a dwell time of 60 seconds in each bath. The teeth were then submitted to mechanical load cycling with an occlusal force of 80N at a frequency of 2Hz. The restorations were sectioned perpendicular to the cervical bonded interface into two 0.8-1mm thick slabs. The slabs were trimmed at the interface with a fine diamond bur in order to obtain a cross-sectional surface area of 0.8-1mm2. All specimens were then subjected to microtensile testing, at a cross-head speed of 0.5 mm/min, until failure of the specimens. The fractured surfaces were observed with a scanning electron microscope (SEM) to evaluate the fracture mode. Microtensile bond strength mean values (MPa) were subjected to ANOVA 3-way and Tukey?s test, at significance level of 5%. The Dunnett?s test was used in order to compare the groups that were submitted to load and thermal cycling with the control groups of each adhesive system (p<0.05). The self-etching primer presented lower bond strength mean values when compared to the total-etch systems (p<0.0001). In addition, the specimens restored with the self-etching primer did not resist to 200,000 e 500,000 load cycles associated with thermal cycling. The effectiveness of the aging protocols performed in this study showed different behavior according to the adhesive system evaluated. The application of only 100,000 load cycles did not present significant lower bond strength mean values. Failure modes varied according to the analyzed group, and all failures modes were verified in the fractured specimens. The number of mixed failures increased and the percentage of interphase failures decreased when the amount of thermal/mechanical cycles applied was higher

ASSUNTO(S)

resinas compostas dental materials composite resins materiais dentarios

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