Abstract : Estimating the number of total dentinal tubules present, measuring the diameter of individual patent dentinal tubules and comparing the efficacy of surface alterations and smear layer removal on planed root surfaces following application of EDTA (15%) and tetracycline hydrochloride (10%). A total of 20 specimens were prepared from 10 human teeth extracted due to chronic periodontitis, from the patients who reported to the Department of Periodontology. The specimens are divided into two groups comprising of 10 specimens in each group for application of EDTA and tetracycline. The surface of the roots was scanned and observed by scanning electron microscopy. Total number of tubules were 33.7± 8.49 and 30.6 ± 4.14 for EDTA and tetracycline groups respectively with no statistical significance. The difference in percentage of patent tubules in EDTA and tetracycline groups, and the percentage patent dentinal tubules was also not statistically significant between the two groups. Number of patent dentinal tubules was slightly higher for EDTA compared to tetracycline. Both EDTA and tetracycline were equally effective in removing smear layer and opening dentinal tubules. The lesser number of patent dentinal tubules in tetracycline group may be due to the inherent difference in their structural characteristics.