Scheme 1

Schematic illustration of the experiment design. (A) Sample preparation and crack generation by a three-point bending system. A notch was created, then a load was applied parallel to the width of the sample with a sharp knife drived by a micrometre screw. (B) MC3T3-E1 mouse osteoblasts culture on HA and TiO₂ pre-cracked samples. (C) Samples stimulation mechanism. A compressive strain on the top surface was induced using a preloaded piezoelectric actuator to stimulate the samples. 50 N were applied at 5 Hz for 150 s.