The purpose of the present study was to examine the possibility of obtaining root conditioning effect by using ethylenediamine tetraacetic acid(EDTA) solution instead of low pH etchants such as citric acid and tetracycline hydrochloride(Tc-HCl). Total 48 root specimens(4×5×2mm) were prepared from the mesial and distal root of 24 periodontitisaffected human mandibular molars after scaling and root planing. The specimens were treated with EDTA(17%, neutral pH, Pulpdent^?, Pulpdent Co., USA) for 1 min., 2 min., and 3 min., and tetracycline hydrochloride(100mg/ml) for 5 min. using the rubbing technique and the placement technique without rubbing. The dentinal tubules of the specimens were examined under a scanning electron microscopy(JEOL, JSM- 840A, Japan). On the microphotographs taken at ×3,000 magnification, the number of identifiable dentinal tubules, opened dentinal tubules, and fully opened dentinal tubules(over 0.9µm in diameter) per the unit area(1,067?m²) were counted. And the rate of opened dentinal tubule and the rate of fully opened dentinal tubule were calculated. The difference of those rates among all groups was statistically analyzed by ANOVA and Dunkan test.

The results were as follows;

1. In the specimens applied with EDTA, the rate of opened dentinal tubule was not significantly different between each group regardless of application technique and application time(p>0.1).

2. In the specimens applied with EDTA, the rate of fully opened dentinal tubule had tendency to be increased in proportion to application time regardless of application technique.

3. In the specimens applied with EDTA within 2 min., the rate of fully opened dentinal tubule failed to show significant difference between the two techniques(p>0.1). But, in the specimens applied for 3 min., the rate of fully opened dentinal tubule was significantly higher in the specimens applied by the rubbing technique than those by the placement technique(p<0.001).

4. In the specimens applied with Tc-HCl for 5 min., both the rate of opened dentinal tubule(p<0.01) and the rate of fully opened dentinal tubule (p<0.001) were induced significantly higher by the rubbing technique than the placement technique.

5. The rate of fully opened dentinal tubule was significantly higher in both the specimens rubbed for 3 min. with EDTA and the specimens rubbed for 5 min. with Tc-HCl than other groups(p<0.001). But there was no significant difference between the two(p>0.1).

The results demonstrate that 17% EDTA solution can replace low pH etchants for root conditioning, and the rubbing technique for at least 3 min. is recommendable.