title: Polarization-sensitive optical coherence tomographic imaging of artificial demineralization on exposed surfaces of tooth roots.
abstract: OBJECTIVE
  The purpose of this study was to assess the potential of polarization-sensitive optical coherence tomography (PS-OCT) to non-destructively measure the depth and severity of artificial demineralization on exposed root surfaces and measure the degree of inhibition by topical fluoride. Although PS-OCT imaging studies have demonstrated the utility of PS-OCT for imaging carious lesions on enamel and dentin surfaces the influence of the cementum layer that is present on intact root surfaces has not been investigated.
  
  
  METHODS
  In this study, extracted human tooth roots were partitioned into three sections with one partition treated with topical fluoride, one partition protected from demineralization with acid resistant varnish, and one partition exposed to a demineralization solution, producing artificial lesions approximately 200-mum deep in root dentin. The lesion depth, remaining cementum thickness and the integrated reflectivity for lesion areas were measured with PS-OCT. These measurements were also compared with more established methods of measuring demineralization, namely transverse microradiography (TMR) and polarized light microscopy (PLM).
  
  
  RESULTS
  PS-OCT was able to measure a significant increase in the reflectivity between lesion areas and sound root surfaces. In contrast to dentin, the cementum layer manifests minimal reflectivity in the PS-OCT images allowing non-destructive measurement of the remaining cementum thickness. The reflectivity of the cementum layer did not increase significantly after substantial demineralization, however it did manifest considerable shrinkage in a fashion similar to dentin and that shrinkage could be measured with OCT.
  
  
  CONCLUSIONS
  This study demonstrates that PS-OCT can be used to measure demineralization non-destructively on root surfaces and assess inhibition of demineralization by anti-caries agents.
authors.affiliation: Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, CA 94143-0758, USA.
authors.forename: Chulsung
authors.initials: C
authors.lastname: Lee
authors.forename: Cynthia L
authors.initials: CL
authors.lastname: Darling
authors.forename: Daniel
authors.initials: D
authors.lastname: Fried
mesh_terms: D002327:Cariostatic Agents / Q000627:therapeutic use; D003732:Dental Caries Activity Tests / Q000379:methods*; D003739:Dental Cementum / Q000473:pathology*; D003743:Dental Enamel / Q000473:pathology; D003804:Dentin / Q000473:pathology; D005460:Fluorides, Topical / Q000627:therapeutic use; D006801:Humans; D008852:Microradiography; D008859:Microscopy, Polarization; D055620:Optical Phenomena; D017213:Root Caries / Q000175:diagnosis* / Q000188:drug therapy; D012542:Scattering, Radiation; D041623:Tomography, Optical Coherence / Q000379:methods*; D017001:Tooth Demineralization / Q000175:diagnosis* / Q000188:drug therapy
chemical_list: D002327:Cariostatic Agents; D005460:Fluorides, Topical