Push-out strength of root fillings with or without thermomechanical compaction

To evaluate the influence of thermomechanical compaction (Tagger's hybrid technique - THT) on the push-out strength of several root filling materials to root dentine.

Root canals of eighty roots in human canines were prepared with the ProTaper system and filled with one of the following materials, using either lateral compaction (LC) (n = 40) or THT (n = 40): AH Plus/gutta-percha (GP) (n = 10), Sealer 26/GP (n = 10), Epiphany SE/Resilon (n = 10) and Epiphany SE/GP (n = 10). Three 2-mm-thick dentine slices were obtained from each third of each root. The root filling in the first slice was subjected to a push-out test to evaluate the bond strength of the materials to intraradicular dentine. Data (in MPa) were analysed using anova and post hoc Tukey's test (P < 0.05). Failure mode was determined at × 25 magnification. The other two slices were prepared for scanning electron microscopy (SEM) to examine the surface of the filling materials.

Lateral compaction (1.34 ± 1.14 MPa) was associated with a significantly higher bond strength (P < 0.05) than the THT (0.97 ± 0.88 MPa). AH Plus/GP (2.23 ± 0.83 MPa) and Sealer 26/GP (1.86 ± 0.50 MPa) had significantly higher bond strengths than the other materials and differed significantly from each other (P < 0.05). There was a significant difference (P < 0.05) between the coronal (1.36 ± 1.15 MPa), middle (1.14 ± 1.05 MPa) and apical thirds (0.95 ± 0.83 MPa). Considering the technique and root filling material interaction, AH Plus/GP-LC was associated with the highest mean values (2.65 ± 0.66 MPa) (P < 0.05). Sealer 26/GP-LC (2.10 ± 0.46 MPa), AH Plus/GP-THT (1.81 ± 0.78 MPa) and Sealer 26/GP-TH (1.63 ± 0.44 MPa) had intermediate values that were not significantly different from each other (P > 0.05). Epiphany SE was associated with the lowest mean values (3.70 ± 0.86 MPa) (P < 0.05), regardless of the root filling technique and type of solid material (cone). Adhesive failures predominated in the specimens filled with Epiphany SE, whilst mixed and cohesive failures were more frequent in those filled with AH Plus and Sealer 26, regardless of the root filling technique. SEM analysis revealed that LC produced a dense and well-compacted filling whilst the use of a hybrid thermomechanical technique resulted in the solid material (GP or Resilon) intermingled within sealer to form a nonhomogenous mass.

Lateral compaction was associated with higher bond strengths of the materials to intraradicular dentine than a hybrid technique using thermomechanical compaction. The greatest push-out strengths were obtained when the canals were filled with LC of AH Plus and GP cones.