A novel scratching approach for measuring age-related changes in the in situ toughness of bone

Abstract

A scratch test using a nanoindentation system was proposed in this study to assess the age-related changes in the in situ toughness of bone matrix at ultrastructural levels. A tissue removal energy density (u r ) was defined and estimated as the work done by the scratch (U T ) divided by the total volume of the scratch groove (u s ). The value of u s was used as a relative measure of the in situ toughness of the tissue. Human cortical bone specimens obtained from middle-aged (between 49 and 59 years old) and elderly groups (over 69 years old) were tested using this technique. A significant difference in the estimated removal energy density (u s ) in the secondary osteons was found between the middle-aged and elderly groups (5.49±0.696 vs. 4.09±1.30 N/mm 2 , respectively).

Authors’ response to “comments on ‘measurement of the microstructural fracture toughness of cortical bone using indentation fracture’”

“…Other errors in hardness can occur due to pile-up and sink-in, which lead to incorrect estimation of the contact area when using the Oliver and Pharr (2004) method. Based on our observations and those of other investigators (Johnson andRapoff, 2003, 2007;Tai et al, 2006;Wang et al, 2007), we do not believe this to be an issue for bone.…”

Calibration of a constitutive model for the post-yield behaviour of cortical bone

“…Rapoff (2003, 2007) reported no pile-up using scanning electron microscopy. More recently, AFM has been used to investigate the presence of pile-up, with Wang et al (2007), Tai et al (2006), and Fan and Rho (2004) reporting "very little pile-up", "sink-in" and "no pile-up" respectively. Spheroconical indenters have a superior ability to induce pileup over more blunt indenters such as the Berkovich indenter and hence, our observations provide compelling evidence that pile-up does not occur.…”

Anisotropic Wear Resistance of Human Mandible Cortical Bone

“…Nanoscratch technique has been used to characterize the in situ toughness not only for osteonal bone tissues but also for small animal models [29]. But only the trace profiles were measured before.…”