Comparative assessment of the roughness, hardness, and wear resistance of aesthetic bracket materials

Objective The purpose of this study was to assess critical properties of orthodontic aesthetic bracket materials. Method Samples of polycarbonate, poly(oxy)methylene, ultra high molecular weight polyethylene (UHMWPE), and polycrystalline alumina raw material used from bracket manufacturing were subjected to: (a) profilometry for the determination of Ra, Rq, Rmax and Rz roughness parameters; (b) Vickers hardness (HV50) testing; and (c) wear resistance determined by the scratch test. The results were analyzed with one-way ANOVA and Tukey multiple comparisons test at α=0.05 level of significance. Results The UHMWP and alumina specimens showed the highest roughness values for all parameters. The highest hardness, amongst the polymeric raw materials, was obtained from the poly(oxy)methylene appliances. Differences were also noted between the polycarbonate raw material of different manufacturers implying an effect from the manufacturing process. With the exception of alumina, the highest wear resistance was found for the poly(oxy)methylene specimens. Significance The results of this study reveal the variability among aesthetic plastic bracket raw materials, their reduced hardness and wear resistance relative to alumina as well as the inappropriateness of UHMWPE as alternative bracket material.