Evaluation of the true self-etching potential of a fourth generation self-adhesive methacrylate resin-based sealer

The limited diffusion of self-adhesive resin cements into crown dentin raises doubts on whether self-adhesive root canal sealers are capable of creating micromechanical retention in instrumented canal walls in the absence of adjunctive use of calcium chelating irrigants. This study evaluated the true self-etching potential of MetaSEAL, a self-adhesive sealer.

Mixed MetaSEAL sealer was applied to (1) fractured radicular dentin that was devoid of smear layers, (2) instrumented canal wall radicular dentin that was irrigated with water as the final rinse to preserve the smear layer, and (3) instrumented canal wall radicular dentin that was irrigated with ethylenediaminetetraacetic acid (EDTA) as the final rinse to remove the smear layer. Cryofractured tooth halves without sealer application were examined by scanning electron microscopy to identify the characteristics of the bonding substrates. The other tooth-halves were filled with sealer and processed for transmission electron microscopy.

MetaSEAL did not demineralize fractured radicular dentin that was devoid of smear layer and smear plugs. The self-adhesive sealer was incapable of etching beyond the 1- to 2-mum-thick smear layer retained on water-irrigated instrumented dentin to demineralize the underlying radicular dentin. Smear layer and smear plugs were absent in EDTA-irrigated radicular dentin. The EDTA also partially demineralized the intact dentin, creating a thin bed of collagen for infiltration of the self-adhesive sealer.

The limited self-etching potential of MetaSEAL is a clinically legitimate concern. Incomplete smear layer removal from instrumented canal wall regions that are not reached by calcium chelating agents might jeopardize its bonding and sealing performance.