Adaptation and sealability of two contemporary obturation techniques in the absence of the dentinal smear layer

The aim of this study was to evaluate the adaptation and short- and long-term sealability of two different thermoplastic techniques--a core carrier technique, Thermafil; and a warm vertical continuous wave of compaction technique, System B.

Fifty-one mesial roots of mandibular molars with separate canals, patent canal orifices and curvature greater than 15 degrees were cleaned and shaped with Orifice Shapers and ProFile.04/.06 taper Ni-Ti rotary files using 5.25% NaOCl and 17% REDTA to a size 30.04 taper Profile at the apex to create a continuous tapered preparation. Canals were randomly obturated with Sealapex root canal sealer and either alpha-phase gutta-percha on a plastic Thermafil carrier, or nonstandardized beta-phase gutta-percha using the System B heat source. Proximal radiographs of roots were evaluated by three examiners based on established criteria for overall material adaptation, apical adaptation and filling material extrusion. Teeth were randomly separated into three groups of 17 each and placed in black India ink for 10 days, 24 h, or after 67 days storage in Hank's Balanced Salt Solution. All roots were demineralized and rendered transparent. Three examiners evaluated the apical leakage by the linear measurement of dye penetration under the stereo-microscope. The movement of filling material into canal irregularities was also evaluated.

Both obturation techniques were not significantly different in the overall canal obturation and in the apical third adaptation (P > 0.05). Significantly more filling material extrusion beyond the apex was noted with the Thermafil technique (P < 0.001). No significant difference was found amongst the 67-day, 10-day and 24 h System B groups (P > 0.05). The 67-day Thermafil group showed significantly more leakage than the 10-day and 24 h Thermafil groups. There was a significant difference in the degree of leakage between the 67-day Thermafil group and the 67-day System B group (P < 0.05), but not between the 10-day and 24 h groups (P > 0.05). Both obturation techniques produced substantial filling material movement into canal irregularities.

It was concluded that Thermafil demonstrated more filling material extrusion beyond the apex and significantly more long-term apical leakage.