Detection and analyzing plane of non-cavitated approximal caries by cross-polarized optical coherence tomography (CP-OCT).

OBJECTIVE: The objective was to assess the detection ability and the effect of analyzing plane of CP-OCT for non-cavitated approximal caries. METHODS: Thirty human extracted premolars were selected based on micro-computed tomography [mu-CT: mu- CT = 0: sound (n = 12), mu-CT = 1/2: caries into outer-/inner-half of enamel (n = 6 each), mu-CT = 3: caries into outer one-third of dentine (n = 6)]. Teeth were mounted in a custommade device to simulate approximal contact, and scanned from the marginal ridge above the contact area. CP-OCT images were analyzed by deepest caries extension from horizontal and coronal planes, and repeated 48-hrs later. Sensitivity, specificity,percent correct, area under the ROC curve (Az), intra-examiner repeatability and correlation with mu-CT were determined. RESULTS: Sensitivity/specificity/Az for Horizontalplane, Coronal-plane, and Deepest from both planes were 94percent/58percent/0.76,81percent/100percent/0.90, and 94 %/58 %/0.82. Coronal-plane had significantly higher specificity than Horizontal-plane and Deepest (p = 0.004) but Horizontal-plane and Deepest were not different (p = 1.00). Horizontal-plane had significantly lower Az than Deepest (p = 0.048), but Coronal-plane was not different than Horizontal-plane (p = 0.07) or Deepest (p = 0.20). Correlation coefficients were Horizontal-plane (0.53, p < 0.001), Coronal-plane (0.84, p < 0.001), and Deepest (0.66, p < 0.001). CONCLUSION: Within the limitations of this study, CP-OCT could be used to detect non-cavitated approximal caries. Analysis using the Coronal-plane is superior to the Horizontal-plane. CLINICAL SIGNIFICANCE: It is challenging to detect non-cavitated approximal caries clinically due to the adjacent tooth. CP-OCT is a nondestructive, no ionized-radiation caries detection technique. CP-OCT seems suitable to detect non-cavitated approximal caries and observing the Coronal-plane appears better than Horizontal-plane.