This study examined the effect of tannic acid solution on dissolution of dentine collagen and morphological aspects of tendon collagen. Using root dentine, which was cut off from bovine anterior tooth, dentine powders were obtained by the pulverization and lyophilization. They were subject to an application of 1, 3, 5 or 10% tannic acid (TA) solution for 1, 3, 6, 12 or 24 h. TA-treated dentine powders were treated with 40% phosphoric acid (PA) for 30 s at 20 degrees C and additionally with trypsin. Released hydroxyproline in Woessner's assay after a hydrolysis in 6 N HCl at 110 degrees C for 20 h was assumed to be dissolved dentine collagen. Released hydroxyproline in a control sample without acid treatment decreased from 100 to about 60% with increased TA concentration of 1 to 10%, and decreased with increased incubation times of 1 to 24 h when applied by 5% TA solution. Scanning electron microscopy results established the morphological effect of their surface characteristics due to such treatments as 40% PA for 30 s and 5% TA for 6 h, or 40% PA after 5% TA treatment, yielding collagen structures protected by TA to attack from phosphoric acid.
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