Robertson, R. G.; (1995) The multiple impulse method of tooth mobility assessment. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This study evaluates the multiple impulse method of tooth mobility assessment. For many years clinicians have sought a handheld means of evaluating tooth mobility for clinical use. This could provide data to aid in periodontal and restorative diagnosis and treatment planning and allow monitoring of the status of the supporting tissues of teeth and implants. The Periotest device analyses the electronic signals produced by an accelerometer, mounted within a handpiece and attached to a percussion rod which is electromagnetically accelerated towards the tooth to produce a "moveability" value. Bench and electronic testing evaluated the instrument signals and tooth displacement data. Initially this was carried out using an LVDT linked to an ultraviolet recorder and the data was collected from the teeth of anaesthetised Macaque monkeys. Ultimately a computerised recording system in conjunction with a non-contact displacement transducer were used to achieve this. The factors affecting measurement were then analysed using the teeth in pig jaw models. The results are summarised as follows; 1. The percussion rod slows down as it travels away from the handpiece. 2. It is possible to control the position of the handpiece so that this deceleration is not a factor in measurement. 3. Increasing the tooth mass affects signals and the Periotest values obtained. These changes are statistically significant. 4. Measured mobility values decreased as the application point was moved in an apical direction. 5. Significant changes in mobility values were produced by changing the angle of application in the horizontal and vertical plane by more than 100 from normal for some of the test teeth. 6. The results of multiple impulse testing are, to some extent, comparable with traditional tooth mobility measurements. 7. When testing very loose teeth the system gives highly unpredictable results. This is explained by the method of analysis of the signals used by the microprocessor and could be modified to allow the instrument to function over a wider mobility range. Based on the results of this work recommendations are made for the use and further development of this method.

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