Efficacy of remaining root canal dentin on bond strength of prefabricated glass fiber reinforced composite dowels

Abstract Background Thin-walled endodontically treated teeth with variable dentin thickness may affect bond strength of prefabricated glass fiber reinforced composite dowels to root canal dentin. The aim of this study was to evaluate the efficacy of remaining root canal dentin on bond strength of prefabricated glass fiber reinforced composite dowels. Patients and methods This experimental laboratory study was carried out on 40 extracted human upper central incisors that manually shaped, prepared, and obturated. The dowel space of each tooth was planned with 5 mm gutta percha apical seal, prepared to simulate thin-walled root canal and equally divided into four groups according to the remaining dentin thickness: 2 mm (control), 1.5 mm, 1 mm, or 0.5 mm. The desired remaining dentin thickness was ensured using a cone-beam computed tomography scanning. Adhesive resin cement was used for cementation of glass fiber reinforced composite dowels. Subsequently, each specimen was embedded in an auto-polymerizing acrylic resin and sliced into six sections (two cervical, two middle, and two apical). Each slice was then used for a push-out bond strength test in an Instron testing machine with a cross-head speed of 0.5 mm/min. Results Analysis of forces with parametric analysis of variance and Tukey’s Studentized Range disclosed a statistically significant difference for both remaining root canal dentin and root canal regions ( P < 0.001). A statistically significant interaction effect ( P < 0.001) was also found. Conclusions The bond strength of fiber dowels is affected by variable remaining dentin thickness. Significant differences were found among remaining root canal dentin. Bond strength at cervical region was significantly higher than other regions regardless to the remaining root canal dentin.