Confocal microscopy assessment of filling material remaining on root canal walls after retreatment.

AIM: The percentage of Endofill remaining on canal walls after retreatment with different techniques was evaluated using confocal microscopy and qualitative analysis of the interface between the filling material/dentine. METHODOLOGY: Sixty-four root canals of incisors were prepared with ProTaper, filled with gutta-percha and Endofill mixed with 0.1% rhodamine B. The roots were thermocycled and distributed into groups according to the method of evaluation: GI - direct viewing (DV) and GII - operating microscope (OM) and according to the removal technique: A) ProTaper retreatment (PR), B) PR/xylol, C) ultrasound and D) ultrasound/xylol. The root canals were then refilled with gutta-percha and AH Plus with 0.1% fluorescein and sectioned at 2, 4 and 6 mm from the apex. The percentage of remaining Endofill was analysed by confocal microscopy. Additionally, 16 roots were prepared with a ProTaper F5 instrument and were filled with Endofill + 0.1% rhodamine B/gutta-percha (negative control group) (n = 8), and the positive control group (n = 8) were filled with AH Plus with 0.1% fluorescein/gutta-percha. RESULTS: Three-way anova demonstrated differences in the method of evaluation, removal techniques and their interaction (P < 0.05). OM (26.15 +/- 12.16%) had a smaller percentage of remaining sealer than DV (32.77 +/- 14.47%). The Tukey's test revealed that ultrasound/xylol (15.77 +/- 7.15%) led to lower percentages of remaining sealer, significantly different from the PR group (35.25 +/- 13.63%), PR/xylol (33.03 +/- 11.64%) and ultrasound (33.79 +/- 11.71%), which were similar (P > 0.05). Qualitative analysis detected that ultrasound had lower remaining Endofill than PR, particularly when combined with xylol. Operating microscope resulted in lower residual sealer, regardless of the removal technique. CONCLUSIONS: None of the protocols was associated with complete removal of the filling material; however, the use of ultrasound/xylol under an OM provided better results.