In dental research, occlusal force, masticatory load, tension of soft tissue and condition of the dental arch have been measured. It has not been possible to determine accurately the loads on the teeth and consequently on the periodontal structure. The purpose of this study was to develop a new force sensor, employing piezo plastic film. The sensor must be small, light and thin, and several designs were made. The film was used to measure the following forces: 1) tapping force; 2) behavior of the impact force applied to the teeth to evaluate their supporting structure; and 3) interproximal force transmitted in the dental arch. The force sensor was designed to be very small and light weight to attach easily to the teeth, and was made so thin that it could be inserted into the interproximal spaces. Because the stiffness of the piezo plastic film allows for high mechanical impedance and negligible deformation of the film under load, our sensor is a force-measuring device superior to those presently available. Even though the electrical out impedance of the film is high, it is suitable for the measurement of fluctuating forces. The force sensor needs no source voltage so that it can be used safely on the human body. The improved sensor design will have broad application in dentistry.