Assessing near infrared optical properties of ceramic orthodontic brackets using cross-polarization optical coherence tomography

J Biomed Mater Res B Appl Biomater. 2014 Apr;102(3):516-23. doi: 10.1002/jbm.b.33029. Epub 2013 Sep 19.


Secondary decay (caries) under ceramic orthodontic brackets remains a significant dental problem and near infrared cross-polarization optical coherence tomography (CP-OCT) has the potential to detect underlying demineralization. The purpose of this study was to determine the effect of crystalline structure and chemical composition of ceramic brackets on CP-OCT imaging. Four ceramic brackets types, which were divided into monocrystalline and polycrystalline, were examined using CP-OCT. The results of this study demonstrated that the crystallinity of the ceramic brackets affected the 1310 nm CP-OCT imaging with the greatest attenuation seen in polycrystalline alumina brackets. The alumina polycrystalline bracket materials had significantly higher attenuation and scattering than alumina monocrystalline brackets (p < 0.05, ANOVA, Bonferroni). Additionally, bracket base morphology and composition affected NIR light attenuation. There was considerable attenuation in bracket bases that contained additive zirconium spheres (∼30 µm) and this alteration was significantly greater than the jagged alumina crystallographic alterations found in the other bracket systems (p < 0.05, ANOVA, Bonferroni). Noninvasive, near infrared (NIR) cross-polarization optical coherence tomography (CP-OCT) has potential to effectively image through portions of ceramic brackets; however, further investigation into the optical effects of resin integration in the base portion of the brackets is warranted.

Keywords: dental caries; dental ceramics; imaging systems; medical optics instrumentation; optical coherence tomography; polarization.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aluminum Oxide
  • Ceramics / chemistry*
  • Crystallization
  • Dental Stress Analysis
  • Infrared Rays
  • Microscopy, Electron, Scanning
  • Orthodontic Appliances*
  • Spectroscopy, Near-Infrared
  • Tomography, Optical Coherence
  • Zirconium


  • Zirconium
  • Aluminum Oxide