SEM evaluation of roots obturated with adhesive root canal sealers

Objectives:  MetaSEAL^TM (Parkell; USA) and Super-bond^TM RC sealer (Sun Medical; Japan) were newly developed adhesive resinous sealers containing 4-META.  To evaluate the morphological characteristics in the interface between resinous sealer and radicular dentin, SEM observation and microtensile testing of roots obturated with these sealers were executed.

Methods:  The extracted single-rooted human teeth were used.  After enlargement of root with Ni-Ti file, root canals were irrigated with the combination of EDTA and NaClO.  MetaSEAL^TM or RC sealer was filled into root canal, and compared with Epiphany or Epiphany SE.  After storage in 100% humidity at 37°C for 2weeks, specimens were cut horizontally against tooth axis and sliced into 0.8mm thick.  SEM observations were executed to evaluate resin-dentin interface, and microtensile bond strengths (MTBS) were measured at a cross-head speed of 1mm/min.

Results:  When resin-dentin interfaces were observed with various distances from the apex, these SEM micrographs of MetaSEAL^TM and RC sealer showed the formed hybrid layer and resin tags in all the resin-dentin interfaces.  Although those of Epiphany groups were observed resin tags in part of resin-dentin interface, the hybrid layer was not observed.  MTBS of MetaSEAL^TM and RC sealer were significantly higher than those of Epiphany groups (Epiphany groups: debonded spontaneously).

Conclusion:  It was considered that MetaSEAL^TM and RC sealer had good adaptation in resin-dentin interface due to high degree of infiltration and polymerization into radicular dentin.  Since the contraction by polymerization initiated from the resin-dentin interface was observed, it was suggested that polymerization of these sealers proceeded from the interface.  On the other hand, it was considered that formation of hybrid layer was not observed in case of Epiphany groups because NaClO caused strong inhibition of polymerization.  These results indicated that MetaSEAL^TM and RC sealer could prevent coronal and apical leakages by formation of hybrid layer to radicular dentin.