Wear 260 (2006) 1256–1261 On evaluation of wear resistance of tooth enamel and dental materials Eugeniusz Sajewicz ∗ Faculty of Mechanical Engineering, Bialystok Technical University, ul. Wiejska 45c, 15-351 Bialystok, Poland Received 21 February 2005; received in revised form 17 August 2005; accepted 23 August 2005 Available online 7 October 2005 Abstract A survey of the literature shows that in many studies on the wear resistance of tooth enamel or dental materials a large scatter of experimental data has been obtained when wear tests were performed at a fixed load. Despite the steady loading, wear conditions vary during sliding, since tooth enamel as well as dental materials have inhomogeneous structure. This leads to changes in contact interactions between sliding surfaces, and as a result, we get changes in the friction and wear behaviour of tested materials. This is why at the same loading the wear can be different. In this study, more reliable approach to evaluation of the wear resistance of human enamel and dental materials is proposed. The procedure is based on the correlation between the volumetric wear and the friction energy dissipated during sliding. The model can be useful to compare the wear resistance of different dental materials tested in different ambient conditions. © 2005 Elsevier B.V. All rights reserved. Keywords: Tooth enamel; Dental restorative material; Wear resistance; Friction energy 1. Introduction Tooth enamel is one of those unique natural substances which still cannot be substituted effectively by artificial restorative materials. The most important feature of enamel is its good wear resistance, despite fairly bad working conditions, such as widely ranging load, reciprocating movements, temperature shocks or possible acid attacks. Sound enamel under friction coming from mastication and biting loses only 10- to 40-m thick layer per year [1], whereas average wear rate found for restorative dental materials in clinical conditions equals 8–9 m per month [2]. This is why many researchers make a lot of effort to discover the nature of good wear performance of tooth enamel. It would seem that the best approach to evaluate the wear resistance of enamel as well as dental restorative materials should be based on experiments carried out in the oral envi- ronment. Although this approach has some advantages, there are also certain difficulties as clinical investigations are time consuming, and what is more important, lack controls and a wide variety of factors make it impossible to determine the influence of a separate factor on clinical wear mechanism. For ∗ Fax: +48 85 746 92 10. E-mail address: esaj@pb.bialystok.pl. these reasons, in vitro wear tests are widely used. By now, many test devices have been designed and employed for many ‘tribological’ purposes. Most of them are used for two-body tests employing relative movement between the sample and an abrasive surface (countersample). Among many of the geo- metric designs, pin-on-disc is the most commonly employed. This method is usually quite simple and advantageous giving relatively quick results. However, in some papers a certain disad- vantage is reported, namely poor repeatability of results obtained at potentially the same parameters, i.e. load, contact pressure, sliding speed and so on [3]. It seems that the above statement could be general regarding the majority of tribological tests, as the problem of reproducibility of wear and friction is considered not only for tooth tissues or dental materials [4]. It is entirely clear that the scatter of wear data is unavoidable, since the wear process must be considered as random. However, in some cases the scatter of wear of tooth enamel or restorative materials is unexpectedly enormous. For instance, the test carried out by Hirano et al. on five resins showed that the values of the coef- ficient of variation calculated for volume of removed material after 5000 or 10,000 sliding cycles, ranged from 38.3 to even up to 81.6% [5]. The similar results were obtained by Eisenburger and Addy during wear testing of tooth enamel in saline [6]. The coefficient of variation, calculated for the wear depth on the basis of their experimental results, ranged from 18.6 to 69.2%. 0043-1648/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.wear.2005.08.010