Elsevier

Journal of Endodontics

Volume 29, Issue 3, March 2003, Pages 170-175
Journal of Endodontics

SCIENTIFIC ARTICLES
A New Solution for the Removal of the Smear Layer

https://doi.org/10.1097/00004770-200303000-00002Get rights and content

Various organic acids, ultrasonic instruments, and lasers have been used to remove the smear layer from the surface of instrumented root canals. The purpose of this study was to investigate the effect of a mixture of a tetracycline isomer, an acid, and a detergent (MTAD) as a final rinse on the surface of instrumented root canals. Forty-eight extracted maxillary and mandibular single-rooted human teeth were prepared by using a combination of passive step-back and rotary 0.04 taper nickel-titanium files. Sterile distilled water or 5.25% sodium hypochlorite was used as intracanal irrigant. The canals were then treated with 5 ml of one of the following solutions as a final rinse: sterile distilled water, 5.25% sodium hypochlorite, 17% EDTA, or a new solution, MTAD. The presence or absence of smear layer and the amount of erosion on the surface of the root canal walls at the coronal, middle, and apical portion of each canal were examined under a scanning electron microscope. The results show that MTAD is an effective solution for the removal of the smear layer and does not significantly change the structure of the dentinal tubules when canals are irrigated with sodium hypochlorite and followed with a final rinse of MTAD.

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MATERIALS AND METHODS

Forty-eight extracted maxillary and mandibular single-rooted noncarious human teeth were used for this study. Teeth with previous coronal restorations or root canal treatment were excluded. The teeth were randomly divided into 4 groups of 12 teeth each according to the type of irrigants used during and after instrumentation (Table 1).

After preparing a conventional access preparation for each tooth, a K-type file (size 10 or 15) was used to determine the working length by penetrating the apical

RESULTS

Removal of smear layer from the surfaces of root canals revealed the presence of more abundant and larger dentinal tubules in the coronal third of root canals compared with those seen in the middle and apical thirds of the root canal system. The dentinal tubules in the apical third of the canals were smaller and fewer than those observed in the rest of the root canals (Fig. 1). In addition, removal of the smear layer showed the presence of many lateral canals in the apical thirds of the root

DISCUSSION

The main purpose of this investigation was to evaluate the effectiveness of an irrigant solution with ingredients capable of disinfecting the dentin, removing the smear layer, opening the dentinal tubules and allowing the antibacterial agents to penetrate the entire root canal system. Various antibiotics such as penicillin, bacitracin, and streptomycin have been used in the past to disinfect the root canals (11). However, because of the ineffectiveness of these antibiotics against the flora of

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The authors thank Dr. Hossain Mohammadi for providing hundreds of extracted teeth for this project.

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