[Relationship between length of resin tag and bond strength of bonding adhesive]

It is well known that the bond strength of direct bonding adhesive to etched enamel is dependent upon the formation of resin tags. So it is considered that there is a significant correlation between the bond strength and the length and shape of resin tags. However, there are very few reports on this correlation. In this study, a method of combining halogenated methacrylate and electron-probe microanalyzer (EPMA) was applied for measurement of resin tag length in order to investigate the correlation between the bond strength and resin tag length. Two experimental light cured adhesives were prepared for this study. One (CI-U) was prepared by blending microfiller (30 wt%) to the mixture of di (1-methacryloyl-oxyethyl-2-chloromethyl)-2,2,4-trimethylhexamethylene dicarbamate (50 wt%) and triethylene glycol dimethacrylate (TEGDMA: 59 wt%) and the other (Br-B) was prepared by blending microfiller (30 wt%) to the mixture of Bis-GMA (22.2 wt%), TEGDMA (65.9 wt%) and tetrabromobisphenol-A-glycidyl methacrylate (4Br-Bis GMA: 11.9 wt%). Preparation of 2%, 10%, 37%, and 60% phosphoric acid solutions, 2%, 5%, 10%, and 30% maleic acid solutions and 2%, 5%, 10%, and 30% citric acid solutions was carried out for use as etchants. The consistency and the bond strength to etched enamel for the adhesives and the amount of decalcification for the etchants were measured. The etched enamel surfaces, the resin tags on resin surfaces and the interfaces between the resin and enamel were observed with a SEM. The results were as follows: 1) The consistency of Cl-U was higher than that of Br-B. 2) The amount of decalcification was proportional to acid concentration, except for phosphoric acid solution. The amount of decalcification decreased in the order of citric acid solution, maleic acid solution and phosphoric acid solution when the concentration was 2% and 10%. 3) The SEM micrographs revealed that the enamel surface treated with the etchants containing a high concentration of acid was rougher. 4) The bond strength increased with increasing the concentration of the etchants except for the bond strength of Cl-U after being immersed in 37 degrees C water for 30 days and being thermal cycled. The bond strength for Cl-U was reduced greater than that of Br-B by long-term water immersion and thermal cycling.(ABSTRACT TRUNCATED AT 400 WORDS)