5.4. The effects on bone biomechanical properties

In the three-point bending test, there was a significant increase of the tibial stress in the 10% (p=0.022) and in the 20% (p=0.004) xylitol supplementation groups as compared to the control rats (study IV). A parallel, but not a significant effect was also seen in the 5% xylitol supplementation group (p=0.062). No significant differences in strain or Young"s modulus were detected between the groups (Figure 5-6).

In the torsion test, the femoral shear stress also increased along with the increasing xylitol content, 10% (p=0.031) and 20% (p<0.001) xylitol supplementation groups differing significantly from the controls (Figure 5-6). A trend towards an increased shear modulus of elasticity was detected in all xylitol groups, although only the 20% supplementation group differed significantly from the controls (p=0.031).

The loading of the femoral neck showed a significant increase in the stress of the neck (load/area) in the 10% (p=0.031) and in the 20% (p<0.001) xylitol supplementation groups as compared to the controls (Figure 5-6). A parallel, but not a significant effect was seen in the 5% xylitol supplementation group.

In study V, the three-point bending test showed a significant preventive effect of 10% dietary xylitol supplementation against the ovariectomy-caused decrease of tibial stress (p<0.01) (Figure 5-7). No significant differences were found between any groups in the values of strain or Young"s modulus.

Accordingly, 10% dietary xylitol supplementation prevented the ovariectomy-caused decrease of femoral shear stress in the torsion test (p<0.01) (Figure 5-7). A trend towards an increased shear modulus of elasticity in the 10% dietary xylitol supplementation group was detected, but differences between the groups were not statistically significant.

Furthermore, dietary xylitol diminished the ovariectomy-caused decrease in the stress of the femoral neck by 40 % (p<0.01) (Figure 5-7).