Tribological Properties of Dental Enamel Before and After Orthodontic Bracket Bonding-Debonding by Nano-Scratch Test

ABSTRACTThis study investigates the effect of bracket bonding-debonding on the tribological properties of human tooth enamel, when two different adhesives are applied. The nano-scratch experiment was performed on the enamel at untreated and under the bracket regions to obtain wear resistance, scratch hardness and friction coefficient. The results indicated that the tribological properties of the enamel vary significantly after bracket bonding-debonding. However, no significant difference exists between the effects of bracket bonding by the nano-composite and the composite adhesives on the tribological properties. Therefore, considering the mechanical and physical properties of the nano-composite adhesive, its bond strength for orthodontic bracket bonding and the influences on the enamel after removing the bracket, the use of nano-composite adhesive is suitable for orthodontic treatments.

An Experimental Study of the Nano-Scratch Behavior of Cement Composite Material

This paper presents a preliminary exploration in tribological property and dynamic elastic/plastic behavior of cement composite material at micro- and nano- scale. Pastes were prepared by pure cement clinker with water-to-cement ratio of 0.3 and 0.4. For comparison, a polymer-based clinker composite was also introduced. Nano-scratch test was carried out to study the scratch process. Different constituents were identified by penetration depth value. Based on this identification, the coefficient of friction and elastic deformation status were analyzed. Substrate effect was found when refers to the coefficient of friction of hard clinker particles embedded in soft matrix. An H/E ratio dependent elastic/plastic behavior was also revealed for cement composite. The results confirm the nano-scratch test as a promising method for cement composite investigation; however, some important attributes of this type of material, including the complexity of multi-phase structure and the viscous effect, need to be taken into account in experimental analysis and practical application.