Calcium hydroxide intracanal dressing removal with different rotary instruments and irrigating solutions: a scanning electron microscopy study

Abstract

This study evaluated the efficacy of 2 types of rotary instruments employed in association with sodium hypochlorite (NaOCl) or EDTA in removing calcium hydroxide (CH) residues from root canals dentin walls. Forty-two mandibular human incisors were instrumented with the ProTaper System up to F2 instrument, irrigated with 2.5% NaOCl followed by 17% EDTA and filled with a CH intracanal dressing. After 7 days, the CH dressing was removed using 4 techniques: NiTi rotary instrument size 25, 0.06 taper (K3 Endo) and irrigation with 17% EDTA (Group 1), NiTi rotary F1 instrument (ProTaper) and irrigation with 17% EDTA (Group 2), NiTi rotary instrument size 25, 0.06 taper and irrigation with 2.5% NaOCl (Group 3) and NiTi rotary F1 instrument and irrigation with 2.5% NaOCl (Group 4). Two roots without intracanal dressing were used as negative controls. Teeth were evaluated by scanning electron microscopy, in the cervical and apical canal thirds. None of the techniques removed the CH dressing completely. In the apical and cervical thirds, F1 instrument was better than instrument size 25, 0.06 taper in removing CH residues (p<0.05), regardless of the final irrigating solution. No difference was found between the irrigating solutions in the groups of F1 instrument and of instrument size 25, 0.06 taper (p>0.05). The negative controls had no CH residues on the dentin walls. In conclusion, the ProTaper F1 instrument was better than K3 Endo instrument size 25, 0.06 taper in the removal of CH intracanal medication, regardless of irrigating solution used.

Efficacy of NiTi rotary instruments in removing calcium hydroxide dressing residues from root canal walls

“…In our study, scanning electron microscopy was used at ×1000 magnification and the calcium hydroxide residues were evaluated using a scoring method similar to that used in other studies. 17,26,27 We failed to remove calcium hydroxide residues completely from the canal walls under the conditions tested, regardless of the rotary instrument used, and dressing remnants were found in the apical and cervical thirds. This finding agrees with those of previous studies showing residues on the root canal walls, regardless of the removal technique used.…”

“…24,25 The dressing can be removed by irrigating the canal with NaOCl, EDTA or citric acid 13,26,27 in conjunction with manual files, 13 passive ultrasonic irrigation, 6,15 sonic activation, 14 the CanalBrush system, 6 or rotary instruments. 17 In the present study, a paste of calcium hydroxide with propylene glycol was used. According to the related literature, the paste composition does not influence the efficiency of mechanical and/or chemical methods in removing residues from root canal walls.…”

“…13,28 The final irrigation with 2.5% NaOCl was chosen because 17% EDTA and NaOCl are equally effective for the removal of calcium hydroxide when rotary instruments are used. 6,17 Various methods have been used in endodontic research to investigate the amount of residues on the canal walls. In our study, scanning electron microscopy was used at ×1000 magnification and the calcium hydroxide residues were evaluated using a scoring method similar to that used in other studies.…”

“…These areas were evaluated by three independent examiners. The images were scored according to the following criteria given by Kuga et al: 17 • 0 -absence of residues, • 1 -small amount of residues (up to 20% of the surface covered),…”

“…11,12 Several techniques have been proposed to remove the calcium hydroxide dressing from the root canal system, including the use of endodontic hand files, 13 sonic activation, 14 passive ultrasonic irrigation, 6,15 the CanalBrush System 6 and nickel-titanium rotary instruments. 16,17 Removal of the dressing using hand files, with or without an irrigating solution, may be inefficient and tedious, 6 whereas the use of NiTi rotary instruments may enhance the removal procedure when compared to the techniques Declaration of Interests: The authors certify that they have no commercial or associative interest that represents a conflict of interest in connection with the manuscript. using hand files.…”