SURFACE CHARACTERIZATION OF CERAMIC BRACKETS - A MULTITECHNIQUE APPROACH

The purpose of this study was to investigate the microstructure and bo nding mechanisms for four types of ceramic brackets by using informati on from several methods. Two of the bracket provided exclusively micro mechanical retention as a bonding mechanism, with the use of microsphe res or microcrystals to achieve a rough structure for the bracket base . A silane layer that provided chemical adhesion was found to cover th e bases of the two other types of brackets; one type also used central regions of increased roughness to provide additional micromechanical retention. Polarized-light optical microscopy showed that the silane l ayer was not continuous. Small area x-ray photoelectron spectroscopy a nalysis (SAXPS) of the silane layer was consistent with the presence o f gamma-methacryloxypropyl trimethoxysilane. The study of the ceramic bracket bases revealed a wide variety in composition, structure, morph ologic condition, and coating treatment that implies different bonding mechanisms to orthodontic adhesives.