The Influence of Storage Time and Cutting Speed on Microtensile Bond Strength

The aim of this study was to verify the influence of the storage time and the cutting speed during specimen preparation on the bond strength of a single-bottle adhesive to dentin. A flat dentin surface was exposed in 36 human third molars. The adhesive system (Single Bond) was applied according to the manufacturer's instructions, and composite resin crowns (Z250) were constructed incrementally. Specimens were stored for 10 min, 24 h, or 1 week in distilled water at 37°C before being longitudinally sectioned in both the "x" and "y" directions at different cutting speeds (0.5, 1.6, and 2.6 m/s) to obtain sticks with a cross-sectional area of approximately 0.8 mm2. The specimens were tested in a tensile load machine (0.5 mm/min) and the fracture mode analyzed. A two-way ANOVA with storage time (3 levels) and cutting speed (3 levels) as factors was used to compare the mean microtensile bond strengths. Highly significant main effects and interaction (p 0.0001) were detected. The highest mean bond strength was obtained with a storage time of 1 week and cutting speed of 2.6 m/s. The lowest mean was found when the specimens were prepared immediately after composite resin placement and sliced at 0.5 m/s. Both the storage time and the cutting speed may affect the bond strength results. Therefore, these variables must be controlled in microtensile bond strength tests. Keywords: microtensile test, cutting speed, resin-dentin bond strength