Near-infrared reflection at 780 nm for detection of early proximal caries in posterior permanent teeth in vitro

OBJECTIVES: The aim of this in vitro study was to evaluate the diagnostic potential of near-infrared reflection at 780 nm (NIRR(780nm)) for early proximal caries detection on the occlusal, buccal and oral surfaces of molars and premolars under simulated, clinically relevant conditions. The findings were validated by micro-computed tomography (µCT). METHODS: Bitewing radiography (BWR) was used as a comparative diagnostic method. 250 sound or decayed permanent teeth were examined using NIRR(780nm) and BWR. The NIRR(780nm) findings were evaluated using yes/no decisions depending on the presence of caries lesions, as the enamel-dentin junction was not detectable in the majority of samples. All NIRR(780nm), BWR and µCT findings were obtained twice by two trained examiners. NIRR(780nm) images were evaluated both occlusally alone and combined occlusally, lingually and buccally. All findings were presented in a cross-table. Sensitivity, specificity and area under the curve (AUC) values were calculated. Reliability assessment was performed using κ statistics. RESULTS: Underestimation of caries was observed for NIRR(780nm) in 26.0% of all surfaces and for BWR in 32.8% of all surfaces. Overestimation was 10.0% for NIRR(780nm) and 0.4% for BWR. Trilateral NIRR(780nm) assessment exhibited an overall accuracy of 67.2 %, an underestimation of 13.6% and an overestimation of 19.2%. Trilateral NIRR(780nm) exhibited 63.0% sensitivity and 69.6% specificity, while BWR exhibited 26.7% sensitivity but 100% specificity for proximal caries detection. CONCLUSION: NIRR(780nm) is not suitable for reliable detection of early proximal caries, even with the application of an ideal setup and optimized in vitro conditions.