Interfacial adaptation of adhesive materials to root canal dentin

Extracted single-rooted maxillary teeth were endodontically treated and filled with gutta-percha/AH-26 (GP), Resilon points/RealSeal (RS), AdheSE DC/Multicore Flow (ADH, self-etch control), or Excite DSC/Multicore Flow (EXC, total-etch control). Specimens were analyzed with electron microscopy using three methods: (a) field emission scanning electron microscopy (FESEM) of the interface; (b) transmission electron microscopy (TEM) of the interface; and (c) FESEM of the material fitting surface. The three adhesive materials (RS, ADH, and EXC) formed a dentin hybrid layer, which nonetheless resulted in interfacial separation. Gaps were more frequent for GP, which did not hybridize dentin. The fitting surfaces exhibited resin tags at all levels for EXC. Tags were less frequent with ADH, especially in the apical third. For RS, resin tags were rare and virtually absent from the apical half, whereas GP did not form tags. Despite the hybridization, a tight seal of the root canal is difficult to achieve because of the complexity and the mechanical challenge of the substrate.