The effect of sandblasting and different primers on shear bond strength between yttria-tetragonal zirconia polycrystal ceramic and a self-adhesive resin cement.

PURPOSE: To evaluate the effect of zirconia primers, air-abrasion, and tribochemical surface treatment methods on the shear bond strength between yttria-tetragonal zirconia polycrystal (Y-TZP) ceramic and self-adhesive resin cement. METHODS AND MATERIALS: Y-TZP ceramic surfaces were ground flat with 600-grit silicon carbide paper and then divided into seven groups of 10 and treated as follows: untreated (control), Monobond Plus, Z-PRIME Plus, ESPE Sil with CoJet, air-abrasion, Monobond Plus with air-abrasion, and Z-PRIME Plus with air-abrasion. Self-adhesive resin cement was placed onto the treated Y-TZP specimens for each group. All specimens were thermocycled and subjected to a shear bond strength test. Scanning electron microscope images of the fractured areas and x-ray diffraction (XRD) analysis of the surface-treated Y-TZP specimens were performed. Data were statistically analyzed using one-way analysis of variance and the Student-Newman-Keuls multiple comparison test (p<0.05). RESULTS: The Z-PRIME Plus treatment in combination with air-abrasion produced the highest bond strength (16.50±2.26 MPa), followed by air-abrasion (10.56±3.32 MPa), and then Monobond Plus combined with air-abrasion (8.93±3.13 MPa), ESPE Sil after CoJet application (8.54±3.98 MPa), and the Z-PRIME Plus group (8.27±2.79 MPa). The control (3.91±0.72 MPa) and Monobond Plus (4.86±1.77 MPa) groups indicated the lowest results (p<0.05). The XRD results showed the peaks of the monoclinic phase for the air-abrasion and CoJet treatment groups compared with the Y-TZP control. CONCLUSION: Z-PRIME Plus primer application after air-abrasion presented the best results for improving the bond strength between Y-TZP ceramic and self-adhesive resin cement.

A biometric study of C-shaped root canal systems in mandibular second molars using cone-beam computed tomography.

AIM: To investigate the configuration of C-shaped canals in mandibular second molars, canal wall thickness and the orientation of the thinnest area at 1-mm intervals from the canal orifice to the apex by using cone-beam computed tomographic (CBCT) images. METHODOLOGY: Three-dimensional CBCT images of 92 Korean mandibular second molars having C-shaped root canals were analysed to determine their configuration using a modification of Melton's classification, as well as the thinnest walls and their location. Associations between configuration type and distance from the canal orifice to the apex, as well as associations between the directional orientation of the thinnest root wall and distance from the canal orifice to the apex, were assessed by Fisher's exact test. Because serial measurements of minimum wall thicknesses were correlated with individual teeth, a mixed-effects analysis was applied. RESULTS: The most common configuration types were Melton's type I in the coronal region and Melton's type III in the apical region. Mean thicknesses of the thinnest root canal walls were 1.39 ± 0.38, 0.85 ± 0.25 and 0.77 ± 0.20 mm in the coronal, middle and apical regions, respectively. The thicker the root canal walls at the orifice region, the greater the decrease in thickness towards the apical region (P < 0.05), with the linguo-central root area being the thinnest. The pattern of decreasing thickness from the orifice to the apex formed a nonlinear cubic curve. CONCLUSIONS: The most prevalent configuration types were Melton's type I (coronal region) and type III (apical region). The linguo-central root area was the thinnest in C-shaped root canals of Korean mandibular second molars. These anatomical variations should be considered during surgical or nonsurgical endodontic procedures.