The purpose of this study was to evaluate sharpening effect of different sharpening stones on periodontal curettes. In conjunction with 21 brand-new Gracey No. 1/2 curette blades, the Arkansas, India synthetic and ceramic stones were used in this study. The simulated root planing procedure was performed with 45 strokes on freshly extracted, single-rooted teeth. Positive and negative controls were provided. All sharpening procedures were carried out by a clinician and 10 sharpening strokes were applied to each blade with an angle of approximately 70 degrees. The blades were then examined by scanning electron microscopy (SEM). The working edges were investigated within the first 1 to 2 mm from the top of the blade under 500 times of magnification and 3 SEM micrographs were taken from each blade. Micrographs were examined for sharp wire edges, narrow bevel and wide bevel. The Fisher's exact test, Mantel-Haenszel test for trend and 1% probability were used for data analysis. Results indicate that (1) following the simulated root planing procedure, blades became dull, (2) among all the sharpening stones, the ceramic stone was least effective (p less than 0.01) in limited sharpening strokes, (3) with the India synthetic stones, no significant difference was found and they had better sharpening effects than others. This study demonstrates that the sharpening effect of India synthetic stones is the best under SEM examination with a standardized sharpening procedure.