A scannig electron microscopic study on the effect of chinese nutgall for smear layer removal on root canal walls

AIM:To observe the effect of Chinese nutgall for smear layer removal on root canal. METHODS: Seventy-two human teeth with one root canal were randomly divided into nine groups. The irrigates were Chinese nutgall(200mg/mL, 100mg/mL, 50mg/mL, 25mg/mL, 12.5mg/mL and 6.25mg/mL), 3 mL/L hydrogen peroxide plus physiological saline, 170g/L EDTA plus 52.5g/L NaClO (positive control group) and distilled water (negative control group). Each group was prepared and irrigated, and the middle of canal walls was observed with scanning electron microscopy. A scoring system for smear layer was used to analysis. RESULTS: The most completed smear layer removal was showed in the group of 170g/L EDTA plus 52.5g/L NaClO, but erosion of the dental tubule occurred. Chinese nutgall with 25mg/ml, 50mg/ml, 100mg/ml and 200mg/ml effectively removed the smear layer, and the degree of the smear layer removal increased with the rise of the concentration. An contraction action on the dental tubules was found. The dental tubules were blocked when concentration was more than 50mg/mL. The group of 30mL/L hydrogen peroxide plus physiological saline and distilled water could not remove the smear layer. CONCLUSION: Chinese nutgall with concentration above 6.25mg/ml can remove the smear layer effectively. It also seemed to have an contraction and block action on dental tubules with concentration increased.