Micro-tensile bond strength

Microtensile bond testing was originally designed to allow the assessment of bond strengths between dental adhesive materials and regions of tooth tissue. Laboratories use micro-tensile bond strength (µ-TBS) testing to compare products or assess the influence of experimental parameters on adhesive-tooth bond strength. In our study, we tested the µ-TBS using 5 wt.% of all the nanoparticles separately added in the commercial adhesive (Scotchbond™ bond, 3 M ESPE, USA) [11]. The restored teeth were sectioned using a low-speed diamond saw (Buehler, Lake Bluff, IL, USA) under water coolant into resin–dentin beams (0.9 × 0.9 mm) and stored in artificial saliva (pH 7.4) for one week. The artificial saliva was used as the testing medium and prepared according to the protocol described by Levallois et al. [26] that involves the dissolving of reagents (0.125 M NaCl, 0.964 M KCl, 0.189 M KSCN, 0.655 M KH₂PO₄, 0.2 M Urea, 0.229 M CaCl₂ 2H₂O, 0.76 M Na₂SO₄ 10H₂O, 0.178 M NH₄Cl and 0.631 M NaHCO₃) in distilled water (pH = 7.4) to produce a total volume of 1.0 L. The beams in each group (n = 75) were then randomly divided into 5 subgroups (n = 15 in each subgroup). The samples were tested for µ-TBS immediately following the one-week and 9 months storage in the artificial saliva (pH 7.4). The artificial saliva solution was replenished every 7 days and the pH was re-checked using a pH meter (Orion 818 pH meter, Thermo Fisher Scientific, USA). For bond strength testing, each beam was mounted on a metallic jig fixed to a universal testing machine (Instron E3000, Microtester, Instron Corp., Canton, MA) using cyanoacrylate adhesive (Zapit; Dental Ventures of America, Corona, CA, USA). A tensile load was applied at a crosshead-speed of 0.5 mm/min⁻¹ until failure. For determining µTBS in MPa, the de-bonded beams were removed, and the cross-sectional area was measured at the site of fracture to the nearest 0.01 mm with the help of a digital caliper (Model 500-196-20, Mitutoyo Digimatic Caliper).