Development of a Multi-Directional Dynamic Load Measuring Tooth Model

Introduction: In-vitro evaluation of powered dental devices such as ultrasonic scalers is often performed under a static load in a known, single direction. The effect of the treatment is then analysed. Such load determination may be carried out using a simple load cell system. Clinically, loading of a tooth may occur with forces applied in multiple directions. Furthermore, the force applied clinically is rarely fixed and varies with time. The aim of this work was to develop an in-vitro tooth model that would enable multiple dynamic force components to be evaluated simultaneously, in real time. Methods: Two Model 13 (1000g) compression load cells (accuracy of +/- 1g) were mounted perpendicularly to each other in an ‘L' shaped metal block. Each load cell was connected, via an S7DC ADC (analogue / digital converter) to a PC fitted with data logging software. Each load cell was powered by its own 30V power supply. A cradle was manufactured to hold the tooth in a fixed, known position. The cradle was fixed to a counterweighted bar which enabled it to be moved vertically or horizontally. This cradle was orientated such that the load cells measured horizontal and vertical force components. The counterweighted bar prevented the weight of the cradle and its contents from registering a load. The arrangement prevented any twisting motion of the cradle. Results: Associated computer software was able to record data from both load cells simultaneously. Multiple load data values (per second) could be acquired for any specified period of time. Data were then presented either as a table of numbers or as a real-time graph. Conclusion: This multi-directional dynamic load measuring in-vitro tooth model will greatly improve in-vitro analysis of the performance of powered dental instruments, producing real-time, multi-directional force/load measurement with accuracy.

Supported by EPSRC grants GR/T22551/01 and GR/T22568/01