Push-out testing and SEM evaluation of adhesive root canal sealers

Objectives:  MetaSEAL^TM (Parkell; USA) is a dual-curing and self-etch resinous root canal sealer containing 4-META.  To evaluate the characteristics of MetaSEAL^TM, measurement of push-out bond strength to radicular dentin and SEM observations were executed.

Methods:  The extracted single-rooted human teeth were used.  The teeth were sectioned at the cement-enamel junction using a water-cooled diamond saw.  After enlargement of up to 1.6 mm diameter of root canal using a peeso reamer, pulp chamber was irrigated with the combination of EDTA and NaClO.  This root canal was filled with MetaSEAL^TM, and others were filled with Epiphany, Epiphany SE or AH26.  All specimens were kept moist at 37°C for 14 days by wrapping them in water-soaked gauze.  The specimens were then cut perpendicular to long axis to create 0.6 mm disk slices using a slow-speed diamond saw.  Push-out bond strengths were measured at a cross-head speed of 1.0 mm/min.  Furthermore, specimens were observed with SEM for evaluation of the interface between resinous sealer and radicular dentin.

Results:  From the results of push-out testing, the value of MetaSEAL^TM was significantly (p<0.05) higher than those of the other sealers.  Furthermore, failure mode of MetaSEAL^TM was almost cohesive failure within the sealer itself.  The SEM micrographs of MetaSEAL^TM showed hybrid layer and resin tags were formed with no gaps in resin-dentin interface.  Although those of the other sealers were observed resin tags, the gaps were partially observed and hybrid layer could not be observed in resin-dentin interface.

Conclusion:  MetaSEAL^TM had the highest push-out bond strength compared with the other resinous sealers.  The SEM observation showed good adhesion and adaptation by formation of hybrid layer in resin-dentin interface.  Therefore, even after endodontic treatment, MetaSEAL^TM adequately infiltrated and polymerized into radicular dentin.  These results indicate that MetaSEAL^TM could act as a complete hermetic apical seal.