Morphological characteristics of the interface between resin composite and glass-ionomer cement to thin-walled roots: a microscopic investigation.

PURPOSE To identify how different treatments of the root dentin surface affect the microscopic appearance of the resin composite/glass-ionomer cement-to-dentin interface. METHODS The root canals of 70 extracted human single-rooted teeth were enlarged to reduce dentin wall thicknesses to 0.5 mm. The roots were randomly divided into seven test groups (n=10) according to the canal irrigant used: no irrigant (control), 5% hydrogen peroxide, 5% sodium hypochlorite, a combination of 5% hydrogen peroxide and sodium hypochlorite, 15% ethylenediaminetetraacetic acid (EDTA), 10% lactic acid, or 20% lactic acid. To simulate thin-walled roots, within each group, crowns were sectioned and the entire surface of each root canal space was enlarged with Profile instrument. Half of treated root canals (n=5) were filled with resin composite (PermaFlo) and the other half were filled with glass-ionomer cement (Fuji II LC). A light-transmitting plastic post (Luminex) was used to create space for a fiber-reinforced post and to ensure polymerization of the restorative material. Specimens were critical-point dried and freeze fractured for scanning electron microscope analysis. Three sites along the root were evaluated (cervical, middle, and apical). RESULTS Scanning electron micrographs showed no differences in the morphology of the resin tags at the cervical, middle or apical levels with any of the irrigants or the restorative materials used. Also, no difference in surface topography was found within individual groups. A resin-dentin interdiffusion zone and resin tags developed after application of resin composite with lactic acid solutions and EDTA but not with the glass-ionomer cement.