title: Near-infrared imaging of secondary caries lesions around composite restorations at wavelengths from 1300-1700-nm.
abstract: OBJECTIVE
  Current clinical methods for diagnosing secondary caries are unreliable for identifying the early stages of decay around restorative materials. The objective of this study was to access the integrity of restoration margins in natural teeth using near-infrared (NIR) reflectance and transillumination images at wavelengths between 1300 and 1700-nm and to determine the optimal NIR wavelengths for discriminating composite materials from dental hard tissues.
  
  
  METHODS
  Twelve composite margins (n=12) consisting of class I, II and V restorations were chosen from ten extracted teeth. The samples were imaged in vitro using NIR transillumination and reflectance, polarization sensitive optical coherence tomography (PS-OCT) and a high-magnification digital microscope. Samples were serially sectioned into 200-μm slices for histological analysis using polarized light microscopy (PLM) and transverse microradiography (TMR). Two independent examiners evaluated the presence of demineralization at the sample margin using visible detection with 10× magnification and NIR images presented digitally. Composite restorations were placed in sixteen sound teeth (n=16) and imaged at multiple NIR wavelengths ranging from λ=1300 to 1700-nm using NIR transillumination. The image contrast was calculated between the composite and sound tooth structure.
  
  
  RESULTS
  Intensity changes in NIR images at wavelengths ranging from 1300 to 1700-nm correlate with increased mineral loss measured using TMR. NIR reflectance and transillumination at wavelengths coincident with increased water absorption yielded significantly higher (P<0.001) contrast between sound enamel and adjacent demineralized enamel. In addition, NIR reflectance exhibited significantly higher (P<0.01) contrast between sound enamel and adjacent composite restorations than visible reflectance.
  
  
  CONCLUSIONS
  This study shows that NIR imaging is well suited for the rapid screening of secondary caries lesions.
authors.affiliation: Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, CA 94143-0758, United States.
authors.forename: Jacob C
authors.initials: JC
authors.lastname: Simon
authors.affiliation: Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, CA 94143-0758, United States.
authors.forename: Seth
authors.initials: S
authors.lastname: A Lucas
authors.affiliation: Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, CA 94143-0758, United States.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Lee
authors.affiliation: Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, CA 94143-0758, United States.
authors.forename: Cynthia L
authors.initials: CL
authors.lastname: Darling
authors.affiliation: Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, CA 94143-0758, United States.
authors.forename: Michal
authors.initials: M
authors.lastname: Staninec
authors.affiliation: Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, CA 94143-0758, United States.
authors.forename: Ram
authors.initials: R
authors.lastname: Vaderhobli
authors.affiliation: Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, CA 94143-0758, United States.
authors.forename: Roger
authors.initials: R
authors.lastname: Pelzner
authors.affiliation: Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, CA 94143-0758, United States. Electronic address: daniel.fried@ucsf.edu.
authors.forename: Daniel
authors.initials: D
authors.lastname: Fried
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D003731:Dental Caries / Q000175:diagnosis* / Q000628:therapy*; D003793:Dental Restoration, Permanent; D006801:Humans; D066298:In Vitro Techniques; D054020:Lasers, Gas; D008852:Microradiography; D008859:Microscopy, Polarization; D019265:Spectroscopy, Near-Infrared; D041623:Tomography, Optical Coherence; D017001:Tooth Demineralization; D014172:Transillumination
chemical_list: D003188:Composite Resins
keywords: Composite restorative materials; Near-IR imaging; Optical coherence tomography; Secondary caries