13.1 The significance of tooth mobility levels and the value of the Periotest as a tool.
The fundamental aims of dentistry are the detection o f systemic disease originating in the mouth and the preservation o f dentitions. The secondary aim is the restoration of damaged or missing teeth to produce a dentition that is comfortable, functional and as stable as possible.
Poor quality or ill advised dentistry and undiagnosed or untreated dental disease may lead to increased mobility of teeth. It is common for teeth to be removed when mobility levels reach the point o f being uncomfortable or where they alarm the patient or dentist.
Interpretation o f the significance o f mobility level is not straightforward because o f the many factors affecting the status o f the tooth support system. Thus mobility values or Periotest values cannot stand alone as the measure o f the periodontal status of a tooth. They do, however, provide additional information to add to radiographic and clinical findings to give a more complete assessment.
The Periotest as a Tool
The factors aflfecting tooth mobility include attachment level, periapical and periodontal inflammatory status and occlusal status (all of which may be under a measure of control o f the clinician) and root morphology, the quality of the
periodontium and biting/chewing force (over which we have no control). Thus it is unlikely that specific therapeutic measures could be based on mobility levels alone.
In comparison with the clinical scale of tooth mobility assessment the Periotest provides an improvement with increased resolution and reproducibility. The instrument is quick and easy to use in the clinical setting but is not usable for very loose teeth. It is possible to measure changes in mobility which is not a realistic possibility using the clinical scale and changes in Periotest value give information which is more useful than Periotest value alone. Decreases of Periotest value during the healing phase after trauma or periodontal therapy give confirmation that all is well while increases in Periotest value after the fitting o f a crown will draw attention to a possible occlusal problem.
The uses o f the current Periotest system:-
a) Monitoring mobility levels before and after periodontal therapy including initial therapy and regenerative surgery and during periodontal maintenance.
b) Monitoring the healing after trauma.
c) Monitoring the changes of mobility after occlusal adjustment by selective grinding or occlusal changes following crown cementation.
The Periotest as a Tool
13.2 The future of the Periotest
The Periotest is very little used in Britain but is mandatory for clinical practice in Germany. The instrument has not gained wide acceptance in this country because of the lack of properly performed studies and the poor reproducibility of measurements of clinically very loose teeth.
The following recommendations for changes to the Periotest are based on the results of the experiments presented in this thesis:-
The microprocessor should be programmed to recognise and measure the full length o f each accelerometer signal rather than measuring the duration until the signal first crosses the +80 millivolt output threshold. If this change were made the
reproducibility of Periotest values in the upper part of the scale would be improved. The scale could then be extended upwards fi'om +50 to allow measurements o f teeth of Miller scale mobility 3. This would greatly increase the usefulness o f the
instrument.
Having established an understanding o f the function o f the Periotest system future experiments could use it as a clinical research tool. For example;-
a) To assess improvements to the tooth support system produced by periodontal treatment procedures such as guided tissue regeneration and grafting
techniques.
The Periotest as a Tool
system.
c) Implantology research. When considering linking implants to natural teeth it may be possible to chose a resilient attachment of a specific resilience, the choice o f which would be based on the Periotest value of the natural tooth.
13.3 The future of tooth support physiology research
In order to increase the precision of the system for load application, load measurement and displacement measurement future instrumentation will require total computer software control. Such a system would allow for a variable loading rate and provide simultaneous load and displacement recordings. The displacement recordings would be both axial and horizontal or conceivably in three dimensions.
Previous research has concentrated on clinically firm teeth. A more complete understanding would be provided by examining factors affecting the tooth support systems of teeth across the entire mobility range.
On a purely theoretical level data produced by a computer controlled system could be used to perfect the rheological analogue model o f the tooth support system. Currently there is no single model which behaves in agreement with experimental data across a wide range of loading rates.