Tribology International 40 (2007) 885–895 A new tribometer for friction and wear studies of dental materials and hard tooth tissues Eugeniusz Sajewicz à , Zbigniew Kulesza Faculty of Mechanical Engineering, Bialystok Technical University, Wiejska 45c, 15-351 Bia!ystok, Poland Received 9 May 2006; received in revised form 19 September 2006; accepted 25 September 2006 Available online 13 November 2006 Abstract This paper presents a new tribometer developed for a study of the tribological behaviours of dental materials and hard tooth tissues. The device simulates oral kinematic conditions and the loading produced during masticatory process. The tribometer is similar to the existing devices regarding the kinematic features, i.e. it produces an adjustable oscillating movement. However, the device machine is equipped with a unique pneumatic system of loading controlled via computer by special software called TOOTHY. The programmable system allows easy adjusting of the loading parameters such as the magnitude of normal force and its amplitude or pattern of cyclic loading. In this way different combinations of loads can be applied thus making the investigation of different wear situations possible. The device has two full bridge strain gauges for the measurement of loading and friction forces, by which the coefficient of friction is determined. The use of the tribometer is illustrated by a comparative study of tribological behaviour of human enamel subjected to two- and three- body friction, and to two different loading patterns as well. The obtained results are discussed. r 2006 Elsevier Ltd. All rights reserved. Keywords: Tribometer; Friction and wear test; Tooth enamel; Dental materials 1. Introduction Up to now a wide range of devices for tribological testing of dental materials has been employed. It is understandable that simple wear-producing machines such as pin-on-disc cannot duplicate the complexity of intra-oral conditions. However, even more sophisticated simulators like the ones developed by De Long and Douglas [1] or by Yap et al. [2] have only partially been successful at predicting clinical performance of restorative dental materials or tooth enamel. The main reason for this situation is that while developing a new design a lot of effort has been concentrated on obtaining a similarity to the physiological movements or force patterns existing in the mouth, whilst there is no standard pattern of intra-oral conditions. Kinematics as well as loading of teeth has a strong stochastic nature, different for each individual [3] and it depends, for instance, on the kind of food subjected to reduction, and as a consequence substantial scatterings of the tooth wear is observed [4]. It follows from the above that the methodo- logy of tribological investigations of dental materials or hard tooth tissues as well as designed apparatus should be covering main oral features (in terms of tribology) with a possibility of their controlling rather than fixed ‘‘the most probable’’ oral conditions. This approach gives us also a possibility to carry out more fundamental investigations instead of a simple wear assessment after tests. Moreover, it is also very important to record the friction force as a function of test time (usually skipped in oral simulators). This allows us to obtain kinetic characteristics, which are helpful to interpret wear mechanisms and utilize energy criteria to evaluate wear resistance of the investigated materials [5]. On the basis of the literature study and the authors’ own experimental experience, it is postulated here that a ARTICLE IN PRESS www.elsevier.com/locate/triboint 0301-679X/$ - see front matter r 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.triboint.2006.09.006 à Corresponding author. Tel.: +48 85 746 92 53; fax: +48 85 746 92 10. E-mail addresses: esaj@pb.bialystok.pl (E. Sajewicz), kuleszbi@pb. bialystok.pl (Z. Kulesza).