In vitro wear characteristics of a nano-hydroxyapatite filled dental resin composite under two-body wear condition

The aim of this work is to fabricate and characterize the Bis-GMA-based nano-hydroxyapatite (n-HAP) filled dental resin composites (DRCs) which comply with oral tribological behavior. The seven series (i.e., 0, 4, 8, and 12 wt%) of each MPTS ((3-methacryloxypropyl) trimethoxysilane)- and APTES (3-aminopropyl)-treated n-HAP-filled composites were prepared. These DRCs were characterized for void contents, vickers microhardness, and volumetric wear under dynamic working conditions (normal load, speed, and temperature) in artificial saliva medium. In order to perform the volumetric wear experiment, the masticatory movement was simulated by using a dental wear simulator in eight profile motion. The wear tests were conducted as per steady-state and Taguchi (L-16) orthogonal array; further, ANOVA analysis was employed to define the contribution of each considered process parameter. The findings of the experiment and ANOVA result reveal that n-HAP filler content has a greater contribution (95%) in improving the wear resistance ability of DRCs. In concerned with the unfilled dental material, 12 wt% of MPTS- and APTES-modified n-HAP-filled DRCs shows maximum microhardness [i.e., 34.10 Hv (39.52% improvement) for DRCs-12M and 33.32 Hv (36.33% improvement) for DRCs-12A] and minimum volumetric wear in the artificial saliva medium. According to the orthogonal setting of the design of the experiment, volumetric wear of dental composite was improved by 15.164% for DRCs-12M (i.e., A4B2C3D1) and 17.647% for DRCs-12A (i.e., A4B3C2D4) under two-body wear condition (artificial saliva medium). The W-SEM analysis after 20,000 mastication cycles in artificial saliva medium indicates that wear surfaces of DRCs were predominantly affected by the abrasion and adhesion phenomenon.