Influence of healing time on the echographic response of the bone-implant interface
The study aims at investigating the effect of bone healing on the ultrasonic response of coin-shaped titanium implants. Sixteen implants were inserted on the tibiae of rabbits. Two groups of eight samples were considered, each group corresponding to a healing duration (7 or 13 weeks). After the sacrifice, the ultrasonic response of the bone-implant interface was measured in vitro at 15 MHz with a 2-D scanning device. The average value of the ratio r between the amplitudes of the echo of the bone-implant interface and of the water-implant interface was determined. The fraction of implant surface in contact with bone was measured by histomorphometry. The ultrasonic quantitative indicator r decreases significantly with healing time (p = 2.10(-4), from r = 0.53 to r = 0.49). Two phenomena are responsible for the decrease of the gap of acoustical impedance at the bone-implant interface: i) the increase of mineralization of newly formed bone tissue and ii) the increase of the bone-implant contact fraction (from 27 % to 69 %).