RESIN PERMEATION INTO ACID CONDITIONED, MOIST, AND DRY DENTIN - A PARADIGM USING WATER-FREE ADHESIVE PRIMERS

Preservation of the morphological integrity of demineralized dentin co llagen in its hydrated state may account for the success observed in w et-bonding procedures. This study investigated the micromorphological differences between moist- and dry-bonding techniques with the use of: (a) Aelitebond, an alcohol-based, water-free, single-component dentin adhesive primer system; and (b) a water-free, acetone-based experimen tal primer similar to the acetone-based, water-containing All-Bond 2, a two-component primer system. In the wet groups, acid-conditioned den tin surfaces were blotted so that they remained visibly moist prior to bonding. In the dry groups, dentin surfaces were air-dried for 30 sec . Following the bonding procedures, dentin discs in each group were la minated together by means of a chemical-cure resin and processed for s canning electron microscope (SEM) and transmission electron microscope (TEM) examination. Conditioning with 10% H3PO4 for 20 sec. produced c omplete demineralization of the outer dentin. In the wet groups, bande d collagen and interfibrillar spaces could be observed at the surface of the acid-conditioned dentin. Complete wetting of the loosely arrang ed collagen fibrils by the resin resulted in the formation of a hybrid layer. In the dry groups, only a very thin hybrid layer was observed on the dentin surface, along the walls of the tubules, and along the c ourse of their lateral branches. The absence of banded collagen and in terfibrillar spaces within these areas suggested the existence of a co llapsed dentin matrix along various liquid-vapor boundaries that restr icted resin permeation into the subsurface intertubular matrix, produc ing an incompletely infiltrated ''hybridoid region''.