Calcium Hydroxide Removal from the Root Canal: MTAD versus EDTA

Remnants of calcium hydroxide alters the physical properties of sealers.   Objectives:  The purpose was to compare the effectiveness of two irrigants, MTAD and EDTA, to remove calcium hydroxide (Ca(OH)₂) medicament before obturation.  The null hypothesis of this study was that MTAD and EDTA would be equally effective.  Materials & Methods:  Sixty six single rooted extracted teeth had accesses prepared and working lengths established.  Canals were flared via step back preparation.  Sodium hypochlorite was used as an irrigant after each file, and smear layer removed using EDTA.  Calcium hydroxide medicament was mixed with glycerin and placed in the prepared canals with lentulo spiral drills.  Radiographs confirmed that calcium hydroxide filled the canal.  The accesses were sealed with cotton pellet and cavit.   The teeth were stored in a humidified environment at 37^oC for 7 days.  EDTA was then used on 32 teeth to remove Ca(OH)₂, while MTAD was used on 30 teeth.  A final flush was with NaOCl.   There were 4 control teeth – 2 positive and 2 negative.  Crowns were removed and the roots were split in half to expose the canal walls.  Digital images were made and scored as to the amount of Ca(OH)₂ remaining on the canal walls overall and in apical, middle, and coronal sections.  Statistical analysis (Fisher's exact test and non-parametric Wilcoxon rank-sum test) compared scores of the two groups.  Results:  There was no statistical difference (p>0.05 ) between the two irrigants EDTA and MTAD in removing Ca(OH)₂ medicament from the canal walls overall.  The apical 1/3 in each irrigant group showed more remaining Ca(OH)₂ than middle or coronal.  Conclusion:  There was no statistical difference between MTAD and EDTA in Ca(OH)₂ removal effectiveness.  Both irrigant groups showed more remaining Ca(OH)₂ in the apical 1/3.