title: Comparative assessment of the roughness, hardness, and wear resistance of aesthetic bracket materials.
abstract: OBJECTIVE
  The purpose of this study was to assess critical properties of orthodontic aesthetic bracket materials.
  
  
  METHODS
  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 alpha=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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Biomaterials, Section of Basic Sciences and Oral Biology, School of Dentistry, University of Athens, Athens, Greece.
authors.forename: Spiros
authors.initials: S
authors.lastname: Zinelis
authors.forename: Theodore
authors.initials: T
authors.lastname: Eliades
authors.forename: George
authors.initials: G
authors.lastname: Eliades
authors.forename: Margarita
authors.initials: M
authors.lastname: Makou
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Silikas
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D003460:Crystallization; D003764:Dental Materials / Q000737:chemistry*; D004955:Esthetics, Dental; D006244:Hardness; D006801:Humans; D008422:Materials Testing; D016910:Orthodontic Brackets; D011076:Polycarboxylate Cement / Q000737:chemistry; D011095:Polyethylenes / Q000737:chemistry; D012117:Resins, Synthetic / Q000737:chemistry; D013499:Surface Properties
chemical_list: D003764:Dental Materials; D011076:Polycarboxylate Cement; D011095:Polyethylenes; D012117:Resins, Synthetic; C111601:ultra-high molecular weight polyethylene; C005506:polycarbonate; C010102:delrin; D000537:Aluminum Oxide