Study Of Aqueous Extract From Chinese Nutgall For Smear Layer Removal On Root Canal Walls

The cleaning and shaping of the root canals system are the key requirements for success in root canal treatments. During the treatment, a smear layer can be produced on the instrumented walls. Smear layer is composed of dentin debris, odontoblastic processes, necrotized pulp tissue and bacteria. It has been suggested that the smear layer must be completely removed from the surface of the canal wall because it can harbor bacteria and prevent irrigants and medicaments from penetrating into the dentinal tubules. Although there are many root canal irrigants for the smear layer removal, there still have some problems to be resolved.Studies have shown that tannic acid can remove the smear layer, but it has not yet been used in clinical root canal treatment. Chinese nutgall contains a plenty of tannic acid, and many studies have been done in oral clinical application. Because of the inexpensive price and lower adverse reaction compared to other irrigants, Chinese nutgall can be widely used in clinical treatment for smear layer removal. This study is aimed to investigate the action of Chinese nutgall for smear layer removal and to provide evidence for the clinical application.1. Effects of aqueous extract from Chinese nutgall for the removal of smear layer on root canal wallsFirstly high performance Liquid Chromatography were used to determinate the tannic acid contents in Chinese nutgall freeze-dry powder. Then scanning electron microscopic was used to observe the root canal walls irrigated by aqueous extract from Chinese nutgall and tannic acid solution with the same tannic acid contents. The results suggested that the effects of the smear layer removal were no significantly difference between the groups of Chinese nutgall and tannic acid solution with the same tannic acid contents. The effect of the smear layer removal increased with the concentration rising, and a contraction action on the dental tubules was found.2. The efficacy of aqueous extract from Chinese nutgall and several endodontic irrigants for the removal of smear layer and surface composition analysis of the root canal wallA scanning electron microscopic was used to observe the smear layer removal irrigated by aqueous extract from Chinese nutgall and other clinical irrigants on root canal walls, and the surface composition on root canal wall was analyzed by Fourier transform infrared spectroscopy. The results showed that aqueous extract from Chinese nutgall can remove the smear layer without enlarged orifices. It also seemed to have an astringent and block action on dental tubules with concentration increased. A new substance that may be composed of tannic-calcium was found in the blocked dental tubules detected by Fourier transform infrared spectroscopy.3. The study of soft tissue dissolution capacity about aqueous extract from Chinese nutgall The soft tissue dissolution capacity of the irrigants was measuered by the changes of the soft tissue weight. The result showed that the soft tissue dissolution capacity of NaOCl was the best of all these irrigants, and there was no significant soft tissue dissolution capacity in Chinese nutgall groups.4. Effect of aqueous extract from Chinese nutgall on micro-hardness of root canal dentinThe changes of root canal dentin micro-hardness after irrigation were measuered to detect the effect of each irrigant on the root cannal dentin micro-hardness. The results suggest that all kinds of solution decreased the micro-hardness value of root dentine, and Chinese gall solution did not significantly decrease the dentine micro-hardness with concentration increased over time.5. Influence of aqueous extract from Chinese nutgall on the coronal microleakageDye microleakage technology was used to evaluate the influence of the irrigants on the coronal microleakage. The dye penetration in each group was measured and the results showed that a phenomenon of dye microleakage was found in all groups, and the least leakage occurred in NaOCl + EDTA group and Chinese nutgall group.