Monitoring the stability of dental implant using acoustic emission method
This thesis relates to the feasibility of monitoring dental implants using the transmission of Acoustic Emission (AE) from an intra-oral source to a sensor mounted on the patient’s face. A number of in vitro and in vivo experiments have been carried using different AE sources on teeth and dental implants with the ultimate aim of defining the characteristics of the AE signatures in the time- and frequency-domains that are affected by the implant-bone interface. An initial feasibility study was carried out to assess the transmission of simulated AE signals through human teeth and hard and soft tissues by biting on different types of hard food. The tests demonstrated that the transmission of AE signals through human tissues was feasible. However, the source was not reproducible. Further preliminary experiments were carried out to assess the transmission of AE in various dental materials as well as in bone and bone-implant combinations in various states of hydration. The main systematic body of work centred around establishing whether AE signals could discriminate between implants with different amounts of contact with bone. AE signals were generated by applying a standard impulse source through a specially-designed abutment onto dental implants of various sizes (large and small) inserted in bovine ribs under tight and loose fitting conditions. The findings suggested that this simple transmission test was able to assess the quality of the contact between the implant and the bone in the in vitro situation and that it might be possible to extend this to the clinical environment. The (standard) pencil lead break method was not suitable for use intra-orally, so a more suitable source for in vivo testing needed to be developed. After considering various options a continuous source (based on an air jet) was developed and this was applied to dental implants in the same set of systematic tests as for the pencil lead source. The analysis revealed that the air jet source was a little better at discriminating between the various implant contact conditions. Finally, an in vivo study was conducted to assess the characteristics of the transmitted AE form air jet source applied to the dental implants of a number of volunteers. The findings demonstrated that the AE transmission through the implants, soft and hard tissues using an air jet source was feasible, with the degree of transmission depending on a number of variables, some related to the patients themselves and some related to other, tractable engineering factors. The overall conclusion of the work is that the technique is very likely to be successful for monitoring implant stability, and is feasible to apply with minimum invasion to patients whose implants have been newly installed. An in vivo study in which the test is applied to patients during the stages of stabilisation of their implants is required in order to validate the technique.