The effect of washing phosphoric acid etchant on shear bond strength of an orthodontic adhesive

Kim, Hee Kyun; Lee, Ki Soo; Park, Young Guk

Abstract

The aim of present study in vitro was to evaluate and compare the effects of different washing times of enamels etched with low phosphoric acid solution which makes unsoluble salts and etched but contaminated with saliva on shear bond strength of an orthodontic adhesive to enamel, and to observe the washing effect on the etched enamel surface by scanning electron microscope. All brackets were bonded with Mono-Lok2(TM)) on the labial surface of extracted human bicuspids after etching with 20w/w% and 37w/w% phosphoric acid solution for 60 seconds and then washing for 0, 5,10 and 20 seconds respectedly, After etching with 37w/w% phosphoric acid solution and contaminating with saliva for 30 seconds and then washing for 0, 5, 20 and 30 seconds and re-etching for 10 seconds. After 24 hours passed in the 37C water bath, the shear bond strengths were measured on Universal Test Machine. The data were evaluated and tested by ANOV A and Duncan's multiple range test, and those results were as follows. 1. There was no significant differences between (P>0.05) shear bond strength of bonded bracke ts with 5, 10, 20 seconds washing etched enamel using 37%w/w% phosphoric acid solution. 2. The shear bond strength of bonded brackets with 20w/w% phosphoric acid and then washing for 5 seconds showed bonded strength durable to occlusal force but its coefficiency score was high and etched surface was not cleaned completely and therefore it was assumed that its clinical application is not applicable. 3. There was no significant differences between (P>0.05) shear bond strengths of bonded brckets with washing for 5 seconds etched enamel using 37w/w% phosphoric acid solution and 10, 20 seconds washing etched enamel using 20w/w% phosphoric acid solution. 4. The shear bond strength of washing for 5 seconds etched enamel which was contaminated with saliva showed sufficient bonded strength durable to occlusal force but its coefficiency score was high and therefore its clinical application was not applicable. 5. After etching, the sample contaminated with saliva showed the sufficient shear bond strength even washing 20 seconds without re-etching.