Push-out Strength of ProRoot Endo Sealer Using A Cone-free Model

Objectives: Push-out strengths of endodontic sealers were found to be much lower when tested as thin non-uniform layers (Jainaen et al., Int Endod J, 2007). This study evaluated the push-out strengths of dentin-sealer interfaces of three sealers before and after immersion in a simulated body fluid (SBF) using a cone-free root dentin model. Methods: Sixty 0.9 mm thick longitudinal root dentin slices were prepared from extracted human canines. Standardized 0.9 mm diameter simulated canal spaces were prepared using 0.04 taper Profile instruments along the coronal, middle and apical thirds of the slices (n=40/location). Following NaOCl/EDTA cleaning, the cavities were filled with ProRoot Endo Sealer, a new calcium silicate-based sealer (PES; Dentsply Tulsa Dental Specialties), AH Plus Jet (AHP; Dentsply/Caulk) or Pulp Canal Sealer (PCS; Kerr). After complete setting, half of the sealer-filled cavities were tested with a fiber-optic illuminated push-out testing device. The rest were immersed in SBF for 28 days before push-out evaluation. Failure modes after push-out were examined with stereomicroscopy and FE-SEM. Results: Location of the sealer-filled cavities had no significant effect on push-out strength. Data from the coronal, middle and apical aspects of the dentin slices were pooled (Table; in MPa) and further analyzed using two-way ANOVA and Tukey's test (a=0.05).

	PCS	AHP	PES
Without SBF	0.70±0.63 A,1	3.50±1.70 B,1	16.17±6.48 C,1
After SBF	0.41±0.29 a,1	6.60±1.75 b,2	22.44±4.95 c,2

Both the factors “sealer type” and “SBF storage” were significant (p<0.001) in affecting push-out results. Interaction of these two factors were also significant (p<0.001). Failure modes were predominantly adhesive and mixed for PCS and AHP, and predominantly mixed and cohesive for PES. Needle-shaped crystallites were present along the PES sealer-dentin interface after SBF storage. Conclusion: When tested in bulk instead of thin films, the PES sealer-dentin interface exhibited much higher push-out strengths than the other two commercially available sealers, particularly after SBF storage.