Influence of dental fluorosis on the bond strength of adhesive system to enamel / "Influência da fluorose dental na resistência de união de sistemas adesivos ao esmalte: análise em microscopia eletrônica de varredura e teste de microtração"

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

The purpose of this study was to observe the influence of dental fluorosis on the characteristics of the acid etch pattern and penetration of adhesive systems into enamel, by means of scanning electron microscopy (SEM), and on the bond strength of adhesive systems to enamel, through microtensile testing. In order to do so, 196 permanent posterior teeth were classified according to the Thylstrup and Fejerskov Index (TF= 0.1 and 4) and 69 of them were selected. Two-steps adhesive systems, one self-etching, Clearfil SE Bond®, and one total-etching, Adper Single Bond 2®, were used. For SEM analysis of the etch pattern and of the resin replicas, 27 premolars were sectioned mesiodistally and divided into 9 groups (n=3). The buccal surfaces were selected and longitudinally sectioned, using the half for each analysis. Specimens of the phosphoric acid gel at 37% (Magic acid®) group were etched using the two etching times (15 and 60 seconds), washed with air/water for 20 seconds and dried. Specimens of the Clearfil SE Bond® group received application of the material?s primer followed by a treatment to remove it. In order to obtain the resin replicas, the surfaces were outlined (2x2mm) using insulating tape, they were treated with each adhesive and underwent the building of a resin block (Filtek Z250TM ? 3M ESPE Brazil) of 2mm height. These specimens were immersed in 18% HCl for 48 hours and washed with distilled water under ultrasonication for 15 minutes. Microtensile testing was conducted on the intact buccal surface of 42 third molars that were divided into 7 groups and subdivided according to the degree of fluorosis and to the type of adhesive system, being that two etch times (15 and 60 seconds) were used in the TF4 group. After prophylaxis with pumice, washing and drying, the adhesive systems were applied and the composite resin blocks (Filtek Z250TM ? 3M ESPE Brazil) of 5x5mm were built upon a treated surface. After 24 hours, the blocks were sectioned in the X and Y directions perpendicular to the bond interface in order to obtain stick-shaped specimens with an area of approximately 1mm2. The sticks were submitted to tensile forces at a speed of 1mm/min and the values obtained underwent variance analysis (p<0.05). The etched surfaces, the replicas and fractured sticks were processed for analysis by SEM. There was a statistically significant difference between the adhesives (p = 0.008), being that Single Bond 2® presented the highest bond strength values. The severity of fluorosis did not influence the bond strength values, the etch pattern or the formation of resin tags. The increase in etch time, tested in TF4, influenced the bond strength, showing lower values for the 60 seconds time. In conclusion, the total-etch adhesive presented better results than the self-etch one in terms of bond strength, etch pattern and penetration of adhesive systems, regardless of the degree of fluorosis. The increase in etch time for the most severe fluorosis (TF4) cases impaired bond strength.

ASSUNTO(S)

resistência de união sistemas adesivos fluorosis fluorose adhesive system bond strength

ACESSO AO ARTIGO

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