In vitro evaluation of coronal microleakage associated with two root obturation techniques

Aim: The purpose of this study was to determine the influence of the smear layer on the coronal microleakage in root canals obturated with laterally condensed cold gutta-percha or Thermafil and two root canal sealers. Materials and methods: Sixty extracted single-rooted human teeth with straight root canals were allocated to two experimental groups. The root canals were instrumented using the STEP-BACK technique, K reamers and K files and irrigated with 2.5 % NaOCl. The teeth in the first group were treated with 17% EDTA and 2.5 % NaOCl to remove the smear layer. The teeth in both groups were obturated either with laterally condensed cold guttapercha (28 teeth) or Thermafil gutta-percha with plastic cores (28 teeth) and RSA or AH-PLUS sealers. The specimens were evaluated for coronal microleakage using silver nitrate solution. The linear penetration of the dye was assessed using a binocular magnifying glass (x25), with an inserted micrometer scale. Results: The results showed low coronal microleakage in the group where the smear layer was removed in both the lateral compaction technique (RSA - 1.71mm and AHPLUS - 1.61mm) and the Thermafil groups - RSA (1.65mm) and AH-PLUS (1.66mm). In the group with the intact smear layer, greater microleakage was noticed in both groups, lateral compaction technique -RSA (3.06 mm) and AH-PLUS (2.83mm) and Thermafil technique -RSA (2.99mm) and AH-PLUS ( 2.83mm). The difference was statistically significant between the groups with and without the smear layer for both RSA (p< 0.001) and AH-PLUS sealers ( p<0.001). Conclusion: The present results suggest that the removal of the smear layer significantly improves the tightness of the coronal seal and reduces the coronal microleakage