Detection of Proximal Caries Using NIRR From 1050 to 1550nm

Objectives: This in vitro study aimed to evaluate the diagnostic potential of near-infrared reflection at 1050 (NIRR₁₀₅₀), 1200 (NIRR₁₂₀₀), 1300 (NIRR₁₃₀₀) and 1550nm (NIRR₁₅₅₀) for proximal caries detection in permanent posterior teeth. The findings were validated by micro-computed tomography.
Methods: A total of 250 healthy and decayed permanent human teeth were arranged in pairs, examined with bitewing radiography (BWR) and using NIRR with wavelengths of 1050 to 1550nm. Findings in the NIRR images were evaluated using a yes/no decision depending on the presence of caries lesions. Two examiners evaluated all findings twice. Reliability assessments included kappa statistics and revealed a high agreement level for all methods. Statistical analysis included cross-tabulation and calculation of sensitivity, specificity and AUC values.
Results: Overestimation of proximal caries was 2.00% for NIRR₁₀₅₀, 7.60% for NIRR₁₂₀₀, 8.00% for NIRR₁₃₀₀, 20.00% for NIRR₁₅₅₀ and 0.40% for BWR. Whereas an underestimation was 18.80% for NIRR₁₀₅₀, 16.40%, for NIRR₁₂₀₀, 14.40%, for NIRR₁₃₀₀, 8.80% for NIRR₁₅₅₀ and 25.81% for BWR. Overall accuracy was 79.20% for NIRR₁₀₅₀, 76.00% for NIRR₁₂₀₀, 77.60% for NIRR₁₃₀₀, 71.20 % for NIRR₁₅₅₀ and 73.79% for BWR.
Sensitivity values for proximal caries detection were 48.91% for NIRR₁₀₅₀, 55.43% for NIRR₁₂₀₀, 60.87% for NIRR₁₃₀₀ and 76.09% for NIRR₁₅₅₀. Specificity values were 96.84% for NIRR₁₀₅₀, 87.97% for NIRR₁₂₀₀, 87.34% for NIRR₁₃₀₀ and 68.35% for NIRR₁₅₅₀. BWR exhibited 29.67% sensitivity, but 99.36% specificity.
Conclusions: For proximal caries detection by NIRR, wavelengths above 1000nm showed significantly higher sensitivity values than near-infrared wavelengths below 1000nm. With increasing wavelength, sensitivity values increased while specificity values decreased.