Poly(methyl methacrylate) (PMMA), which is suitable for use in the human body owing to its biocompatibility, is commonly used in medical applications such as bone nails, bone cement, and dentures. However, due to its hard and brittle nature, PMMA can cause damage when it is subjected to excessive stress and can also cause severe wear. In this study, three different sizes of silica particles were used as reinforcing additives to enhance the wear resistance of PMMA composites. A pin-on-disk wear test was conducted to record the coefficient of friction and wear volume, and the wear volume was measured using a 3D laser scanning microscope. In the wear test, the transfer film of micron and submicron particles produced a plowing effect, resulting in wide grooved wear scars and a higher wear rate than the raw material. The nanoparticle transfer film reduced direct material wear, the wear scars were fine and flat, and the wear rate was decreased, reducing the wear of SiO2-reinforced PMMA composites by 40%. The experimental results revealed that the wear volume is proportional to the wear time. In addition, the observed area of the transfer film on the wear counterpart can be used as a service life sensor of the coating material.