Journal of Theoretical and Applied Mechanics, Sofia, 2016, vol. 46, No. 2, pp. 27–36 DOI: 10.1515/jtam-2016-0008 ROUGHNESS MEASUREMENT OF DENTAL MATERIALS * Assen Shulev, Ilia Roussev, Simeon Karpuzov, Georgi Stoilov, Detelina Ignatova Institute of Mechanics, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Bl. 4, Sofia 1113, Bulgaria, e-mails: {assen, ilia, gstoilov, ignatova, simeon}@imbm.bas.bg Constantin von See, Gergo Mitov Steiner Landstraße 124 A-3500, Krems-Stein, Austria e-mails: {gergo.mitov, Constantin.See}@dp-uni.ac.at [Received 11 December 2015. Accepted 20 June 2016] Abstract. This paper presents a roughness measurement of zirconia ceramics, widely used for dental applications. Surface roughness varia- tions caused by the most commonly used dental instruments for intraoral grinding and polishing are estimated. The applied technique is simple and utilizes the speckle properties of the scattered laser light. It could be easily implemented even in dental clinic environment. The main criteria for roughness estimation is the average speckle size, which varies with the roughness of zirconia. The algorithm used for the speckle size estimation is based on the normalized autocorrelation approach. Key words: Roughness, speckle, light scattering, zirconia ceramics; nor- malized autocorrelation. 1. Introduction There are various factors, affecting dental enamel and crown ceramic mutual wear, which leads to changes in mechanical, microstructural, physical, chemical, and surface characteristics with unpleasant and dangerous conse- quences [1]. Exteriorly, the wear results in changes of the surface’s roughness, * Corresponding author e-mail: assen@imbm.bas.bg This work is supported by the Bulgarian National Science Foundation grant B02/25 (2014) for the project “Clinical Wear Investigation of New Zirconia Dental Ceramics by Optical and Laser Techniques”.