Objectives: The aim of this study was to determine the Hounsfield values of selected bone sites on a computed tomography (CT) scan of the jaw and to investigate the relationship between this radiological parameter and structural parameters.
Materials and methods: A selection of 24 bone samples out of eight cadaver human jaws was made. The following parameters were measured: Hounsfield value in the jaw (HU1) determined by a first CT scan, Hounsfield value of the excised bone specimen (HU2) by a second CT scan, bone mineral density (BMD) by a dual-energy X-ray absorptiometry scan, bone volume (BV/TV) by the microfocus CT scan, first peak transmission time (T(US-1)) and first zero crossing transmission time (T(US-2)) by an ultrasound measurement and Young's modulus (E(MECH)) by a compression test.
Results: Thirteen specimens were composed of a mix of trabecular and a small amount of cortical bone, while another 11 specimens were composed of trabecular bone only. A good correlation was found between the HU value of the specimen (HU2) and BMD (rho = 0.99), BV/TV (rho = 0.97), T(US-1) (rho = -0.83), T(US-2) (rho = -0.87) and E(MECH) (rho = 0.83). For the pure trabecular bone specimens, the HU value of the excised bone specimen (HU2) was highly correlated (rho = 0.95) with the HU value of the total jaw scan (HU1). For mixed trabecular-cortical bone specimens, this relationship was weak (rho = 0.57).
Conclusion: With the current CT scan technology, predictions of the mechanical properties of trabecular jaw bone based on Hounsfield values were only valid for jaws with a thin layer of cortical bone. For jaws with a thicker cortical layer, the prediction of the mechanical properties decreased significantly.