Validation of Optical Coherence Tomography against Micro-computed Tomography for Evaluation of Remaining Coronal Dentin Thickness.
BACKGROUND
Optical coherence tomography (OCT) is a noninvasive modality to obtain in-depth images of biological structures. A dental OCT system has become available for chairside application. This in vitro study hypothesized that swept-source OCT can be used to measure the remaining dentin thickness (RDT) at the roof of the dental pulp chamber during excavation of deep caries.


METHODS
Human molar teeth with deep occlusal caries were investigated. After obtaining 2-dimensional and 3-dimensional OCT scans using a swept-source OCT system at a 1330-nm center wavelength, RDT was evaluated by image analysis software. Microfocus x-ray computed tomographic (micro-CT) images were obtained from the same cross sections to confirm OCT findings. The smallest RDT values at the visible pulp horn were measured on OCT and micro-CT imaging and compared using the Pearson correlation. Pulpal horns and pulp chamber roof observation under OCT and micro-CT imaging resulted in comparable images that allowed the measurement of coronal dentin thickness.


RESULTS
RDT measured by OCT showed optical values range between 140 and 2300 μm, which corresponded to the range of 92-1524 μm on micro-CT imaging. A strong correlation was found between the 2 techniques (r = 0.96, P < .001).


CONCLUSIONS
Further analysis indicated linear regression with a slope of 1.54 and no intercept, closely matching the bulk refractive index of dentin. OCT enables visualization of anatomic structures during deep caries excavation. Exposure of the vital dental pulp because of the removal of very thin remaining coronal dentin can be avoided with this novel noninvasive technique.
Cariology and Operative Dentistry Department, Graduate School of Medical and Dental Science, Tokyo Medical and Dental University, Tokyo, Japan.
Patrycja
P
Majkut
University of Washington, School of Dentistry, Seattle, Washington. Electronic address: arsadr@uw.edu.
Alireza
A
Sadr
Cariology and Operative Dentistry Department, Graduate School of Medical and Dental Science, Tokyo Medical and Dental University, Tokyo, Japan.
Yasushi
Y
Shimada
Division of Oral and Dental Surgery, Department of Advanced Medicine, National Hospital for Geriatric Medicine, National Center for Geriatrics and Gerontology, Aichi, Japan.
Yasunori
Y
Sumi
Cariology and Operative Dentistry Department, Graduate School of Medical and Dental Science, Tokyo Medical and Dental University, Tokyo, Japan.
Junji
J
Tagami
D000328:Adult; D000368:Aged; D003731:Dental Caries / Q000000981:diagnostic imaging; D003804:Dentin / Q000000981:diagnostic imaging*; D006801:Humans; D016014:Linear Models; D008875:Middle Aged; D008963:Molar / Q000000981:diagnostic imaging*; D009929:Organ Size; D041623:Tomography, Optical Coherence / Q000379:methods; D055114:X-Ray Microtomography / Q000379:methods; D055815:Young Adult
Deep dentin caries; micro–computed tomography imaging; optical coherence tomography; refractive index; remaining dentin thickness