The effect of various concentrations of sodium hypochlorite on the ability of MTAD to remove the smear layer

By Torabinejad M, Khademi A, Bakland L, Shabahang S.

Date: 01/2003
Journal: JOE

Purpose:

To investigate the effect of various concentrations of sodium hypochlorite (NaOCl) as an intracanal irrigant before the use of MTAD (a mixture of a tetracycline isomer, an acid, and a detergent) as a final rise to remove the smear layer. N=80 single and multirooted teeth.

Materials/Methods:

  • 10 operators, using passive step-back and rotary 0.04 taper, nickel-titanium files. Distilled water, four different concentrations of NaOCl (0.65%, 1.3%, 2.6%, 5.25%), or MTAD was used as intracanal irrigant. The canals were then treated for 2min with 5ml of one of the following solutions as a final rinse: 5.25% NaOCl, sterile distilled water, 17% EDTA, or 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

Results:

  • The results show no significant difference in the ability of distilled water and 5.25% NaOCl to remove the smear layer from the surfaces of instrumented root canals
  • With 5.25% NaOCl and EDTA final rinse, smear layer completely removed from middle and coronal thirds
  • Group B showed erosion of the dentinal tubules as a result of application of EDTA as a final rinse
  • Results demonstrated that MTAD is less destructive to the tooth structure compared with EDTA when used as a final irrigant.
  • Use of MTAD as an irrigant left some odontoblastic processes in the dentinal tubules and organic debris on the surfaces of instrumented root canal walls

Clinical Significance:

As shown by the authors, MTAD may be effective as a final rinse to remove smear layer and reduce erosion of the dentin. However, MTAD by itself is not effective at removing organic debris.