Measurement of the force exchanged by orthodontic masks and patients

One of the key factors for the success of the orthodontic treatments is the patients’ compliance to the prescriptions of the doctors, especially when removable appliances are used. However, at the current state of the art, there are no standard techniques for measuring for how long the patients use the prescribed appliance. Moreover, also the force exerted by the orthodontic appliance on patient is not directly measured. This paper describes two different sensors prototypes, based on pressure resistive transducers and on strain gauges respectively, that measure the traction force in the range between 5 and 30 N. The two prototypes have been calibrated with a purposely designed experimental setup. Results show the higher accuracy of the strain-gauge device in force measurements, that has a standard uncertainty of 0,23 N in the case of half bridge configuration, against a value of 6,7 N for the force sensitive resistors. The time in which the orthodontic mask is worn can be successfully measured also with the pressure-based setup, although the location and the positioning of the setup must be carefully chosen.