Sphero-conical indentor usage for estimation of tribological

Nanoindentation usage for measurement of the dental materials and dental tissues properties, including pathologically altered ones is widespread in modern bioengineering practice when designing new experimental compositions for the regeneration and restoration of damaged enamel and dentine. Application of a sphero-conical indenter in such studies allows for the most delicate measurements of not only mechanical but also tribological characteristics. In the present paper, using a sphero-conical indenter, we conducted the ex vivo research of the mechanical (nanoindentation method) and tribological (nanoscratching with continuous recording of the friction coefficient) characteristics of a composite filling, enamel in its vicinity, glass ionomer cement filling, and infiltrant-modified enamel in the case of early caries. For each sample the measurements of the sound enamel area on the medial opposite part of the tooth were performed. At the same time, for a more detailed analysis of the results, scanning electron and atomic-force microscope images of the studied areas were presented. The advantages of using a polymer infiltrant over filling materials in the case of white spot lesion caries stage were demonstrated. Based on the collected data, it is possible to conclude that the use of composite material by a practicing dental clinician is more preferable in cases where minimally invasive methods of treating early caries are insufficient for effective treatment. If it is possible to use polymer infiltration, the clinician can achieve greater preservation of the patient's enamel by "completing" partially dissolved hydroxyapatite crystals with a polymer material, which allows achieving significant proximity of the mechanical and tribological characteristics of the modified enamel to sound tissue. The limitations of the methods used and ways to overcome them in the future studies are considered in the work as well.