A dynamic modal testing technique for noninvasive assessment of bone-dental implant interfaces.

A dynamic modal testing technique has been developed to noninvasively assess the interface surrounding an endosseous dental implant with a lateral tap from an impedance head hammer. The technique assesses the rotational stiffness of the interface based on the shape of the power spectrum of the force-time curve produced on impact. In vitro experiments were performed to determine the sensitivity of the technique for detecting clinically relevant structural differences between interfaces. The modal test data were able to distinguish interfaces based on the type of bone at the interface and the degree of fixation between the implant and the interface.

Geometric anatomy of the aortic--common iliac bifurcation.

Increased haemodynamic forces in the arterial wall may be among the factors responsible for atherogenesis and for determining the severity of the pathological process at a particular site. The present work was designed to help explain apparent asymmetries in the distribution of atheroma at the aorto-iliac bifurcation. A technique was devised for the quantitative evaluation of the geometric anatomy of this region. Measurements were made on 12 female and 14 male cadavers. In all cases there was an asymmetrical left lateral orientation of the abdominal aorta which resulted in a longer right common iliac artery, smaller left common iliac take-off angle and larger left radius of curvature at the aortic-common illiac bifurcation. These differences may explain, through variations in the local haemodynamics, the predilection of the disease for the left iliac artery, particularly in males with their relatively narrow pelvis. Knowledge of both the exact and the average numerical values associated with the local geometry are essential for a detailed haemodynamic study of the effect of these variations on atherogenesis.

Predilection of occlusive disease for the left iliac artery.

Eighty-six consecutive patients operated on for atherosclerotic occlusion of the aortoiliac segment were examined regarding the severity of the disease in the left or right iliac arteries. Sixty-nine percent of 78 patients were found to have predominantly more severe lesions on the left side. A study of the geometric anatomy of the aortoiliac region in 14 male and 12 female cadavers revealed that the right common iliac take-off angle was wider than the left and the radius of curvature of the right osculating circle at the aortoiliac bifurcation was smaller than the left, with the asymmetry of the region being much more marked in males than in females. The predilection of occlusive disease for the left iliac artery is explained on the basis of these differences in local geometric anatomy and their effect on the local hemodynamics.