The aim of this in vitro study was to determine the feasibility of monitoring the primary stability of dental implants using a simple transmission test with acoustic emission. Forty screw-shaped titanium dental implants were installed in the middle of 10 fresh bovine ribs obtained from different animals. The implants were divided into two size groups, 8.5 mm x 3.5 mm and 13 mm x 4.5 mm, and were inserted in either tight- or loose-fitting conditions. For each implant, pulses of acoustic energy were injected at the centre of a customised gold abutment 3 mm in height using a standard pencil lead break source (Hsu-Nielsen source). A total of 30 acoustic emission recordings were made for each implant in which the transmitted energy was measured on the surface of the bone using an acoustic sensor mounted at the middle of the rib. The transmitted acoustic energy for the implants under tight-fitting conditions was significantly higher than for the loose-fitting for both sizes of implant. The acoustic emission energy values for the 13 mm implants were also higher than for the 8.5 mm implants. The results indicate that implants with good primary stability (tight-fitting) had higher acoustic emission energy than implants where primary stability was poor (loose-fitting). The longer and wider implants produced higher acoustic emission energy than shorter and narrower implants. Together, the findings suggest that a simple transmission test, properly calibrated, should be able to assess the quality of the contact between the implant and the bone in the clinical situation.

There is considerable interest in using acoustic emission (AE) and ultrasound to assess the quality of implant-bone interfaces and to monitor for micro-damage leading to loosening. However, remarkably little work has been done on the transmission of ultrasonic waves though the physical and biological structures involved. The aim of this in vitro study is to assess any differences in transmission between various dental materials and bovine rib bones with various degrees of hydration. Two types of tests have been carried out using pencil lead breaks as a standard AE source. The first set of tests was configured to assess the surface propagation of AE on various synthetic materials compared with fresh bovine rib bone. The second is a set of transmission tests on fresh, dried and hydrated bones each fitted with dental implants with various degrees of fixity, which includes components due to bone and interface transmission. The results indicate that transmission through glass ionomer cement is closest to the bone. This would suggest that complete osseointegration could potentially be simulated using such cement. The transmission of AE energy through bone was found to be dependent on its degree of hydration. It was also found that perfusing samples of fresh bone with water led to an increase in transmitted energy, but this appeared to affect transmission across the interface more than transmission through the bone. These findings have implications not only for implant interface inspection but also for passive AE monitoring of implants.