이 연구는 부식농도가 전단결합강도와 법랑질 표면의 부식깊이에 미치는 영향을 관찰하기 위하여 표면을 편평하게 연마한 소의 법랑질을 0%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% 및 85% 인산용액으로 60초간 부식시키고, 브라켓 접착의 전단결합강도와 법랑질 표면의 부식깊이와 조도를 측정하고, 주사전자현미경으로 부식면을 검경하였으며, 이상에서 얻은 자료를 통계처리하고 평가하여 다음과 같은 결론을 얻었다. 법랑질 표면의 부식깊이는 인산액의 농도가 40% 내지 50%에 도달할 때까지 증가하다가 그 이후의 농도증가와 함께 점진적으로 감소하였다. 법랑질 표면의 부식깊이와 부식면의 조도 사이에 상관성이 없었으며, 부식면의 조도와 전단결합강도 사이에 중등도의 상관성(r=0.63)을 보였다. 인산액의 농도가 5%에서 40%에 도달할 때까지 균질의 편평한 부식면을 나타내는 소견을 보였으나 50%와 60%에서 불균질의 과도한 그리고 편평하지 못한 부식면소견을 보였으며, 10%에서 60%까지의 인산액에 의한 법랑질 부식 후 레진 접착제의 전단결합강도 사이에는 유의차가 없어으며, 5%와 70%의 인산액에 의한 것은 전자보다 작았으나 구강 내에서 교정력에 견딜 수 있는 전단결합강도를 나타낼 것으로 추정된다.
Previous study had shown the diversities in the propriety for optimal bond strength on the concentration of the etchant. The aim of present study in vitro was to evaluate and compare the shear bond strength of orthodontic brackets to enamel and to measure the depth of etch on the phosphoric acid concentrations. A hundred and seventy six extracted bovine lower centrals were ground to yield flat surfaces and etched by the concentration 0%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% and 85% of phosphoric acid respectively during 60 seconds. The shear bond strength of orthodontic brackets, the depth of etch and surface roughness of the enamel were measured, and scanning electron microscopic observations on the etched enamel surfaces were carried out. The data obtained from the very experiments were processed and statistically analyzed and evaluated. The gradual increase in the depth of etch to enamel as the accretion of the concentration of the phosphoric acid up to 40-50% and decline henceforth were manifested. The surface roughness showed no correlation with the depth of etch, yet moderate correlation with the shear bond strength of brackets. Scanning electron microscopic investigation revealed that morphological patterns of the etched enamel surfaces for 5% to 40% of concentrations were even and homogenous, and those for 50% as well as 60% exhibited the overetched and unhomogenous. The shear bond strengths from 10% to 60% of concentration showed no statistically significant differences. It was suggested that the shear bond strengths at 5% and 70% were sufficient to tolerate the force levels of the ordinary orthodontic treatment notwithstanding to be significantly lower than those from 10% to 60% phosphoric acid solution.
