The aim of this study is to investigate the deterioration in mechanical integrity of the collagen network in bovine bone with aging, which are related to fracture toughness. Age-related changes in collagen molecular structures formed by non-enzymatic glycation were examined and indentation fracture technique was used as a method for measuring the microstructural toughness of cortical bone. Microcrack propagation characteristics of bone for fragility were also studied. Young and old group of bovine cortical bone specimens were grouped into 2 as ribosylated and non-ribosylated which were rested in solutions for four weeks. Series of indentations were made on bone specimen groups for each of five masses 10g, 25g, 50g, 100g and 200g for 10 sec to detect the effect of applied indentation load. The applied load was increased to 300g, 500g, 1000g and 2000g for 10 sec to be able to make microcracks. Series of indentations were made on bone specimen groups for each of five durations 5sec, 10sec, 20sec, 30sec for 100g to study the effect of indentation duration. Specimens were examined in the wet and dry state while studying the factors effecting microhardness measurement. Microhardness values measured by 10g of load for 10sec were indifferent between the ribosylated and non-ribosylated groups in the young and old bovine bone pointing that this load is not indicative of the structural collagen changes. Loads of 25g, 50g, 100g and 200g for 10 sec were able to differ ribosylated bone from non-ribosylated bone for the young and old bovine bones. Degree of microhardness increased with increased incubation period. Microhardness of dry specimens being either ribosylated or non-ribosylated were found to be statistically higher than wet specimens in young and old bone except for 10g for 10sec. It has been shown that the calculated fracture toughness measured by the indentation method is a function of indentation load. Additionally, effect of indentation size might have resulted in a higher toughness measurement for higher indent loads with longer cracks even if the toughness is not actually higher.Methods using indentation technique has difficulty in relating the resistance to crack growth to the Mode I fracture toughness definition.Indentation fracture toughness allows sampling only one point on the R&shy / curve methods and was not considered as successful for assessing materials with rising R&shy / curve. Toughness is ranked incorrectly among riboslated and non-ribosylated bovine bone by this technique. Presence of extrinsic toughening mechanisms including crack bridging due to uncracked ligaments and collagen fibers were directly observed by scanning electron microscope. Ribosylated bone was found to have lower number of collagen bridging compared ton on-ribosylated bovine bone.As a summary, indentation fracture method by Vickers indentation in bone is a method for measuring the fracture toughness.

Diabetes is associated with increased fracture risk, which leads to increased morbidity and eventual mortality with a substantial financial burden. Type 2 Diabetics also have increased fracture risk, despite having the same or higher BMD as non-diabetics with a low fracture risk. One hypothesis for this is increased modifications made to the extra-cellular matrix via non-enzymatic glycation (NEG) that can occur in a hyperglycemic environment, such as with diabetes. The accumulation of NEG products, known as advanced glycation endproducts (AGEs) can possibly lead to microdamage and eventual weakening of the bone itself. We developed a time-response model in order to induce a wide range of AGEs in a manner that would sustain the mineral integrity of the bone and could be applied to a variety of bone sample types. This was performed on 65 rat tibias, distributed amongst 8 groups (3,7,10, & 14 days) for both ribose and control. Secondly, the protocol was performed on human cortical beam samples cut from 10 donor tibias with 3,5 and 7 day time points for ribose and control groups. All samples were incubated in a 0.6 M ribose solution or 0.0 M ribose control solution. There was a 7, 4, and 5-fold increase in AGEs at the 7, 10, and 14 day time points respectively over controls in the rat tibia study. There was no significant variation in cortical porosity, however TTMD was significantly less dense in the 14-day ribose treated groups. There was a trend toward higher AGEs with time in the human cortical beam specimens, but no significant increase. The AGEs values in the human cortical beam specimens were much lower than expected based on previous trials and reports in the literature. We were able to establish a time-response model for AGE accumulation in bone. However, the effects of AGEs on bone material properties remains inconclusive.