In vitro early proximal caries detection using trilateral short-wave infrared reflection at 1050 and 1550 nm

This in vitro study evaluated the diagnostic potential of short-wave infrared reflection (SWIRR) at 1050 and 1550 nm for proximal caries detection from the occlusal, buccal, and lingual surfaces of posterior teeth under clinically relevant conditions. Bitewing radiography (BWR) was the alternative index test and micro-computed tomography (μCT) was the reference standard.

Two hundred and fifty proximal surfaces of extracted human teeth were examined using SWIRR at 1050 and 1550 nm and BWR. SWIRR, BWR, and μCT findings were evaluated twice by 2 trained examiners. SWIRR images were evaluated from occlusal and trilateral (occlusal, buccal, and lingual combined) views. Sensitivity, specificity, and area under the curves were calculated. Reliability assessment was performed using κ statistics.

Short-wave infrared reflection (1050 nm) showed sensitivity of 0.44 for occlusal and 0.55 for trilateral assessment, paired with specificity of 0.96 and 0.90, whereas SWIRR (1550 nm) showed sensitivity of 0.73 and 0.85 paired with specificity of 0.76 and 0.59. Compared to occlusal view, trilateral SWIRR view revealed ≈10% higher sensitivity and lower specificity. BWR revealed lowest sensitivity (0.30) and highest specificity (0.99). Over- and underestimation of caries demonstrated opposite trends: from 1050 to 1550 nm, overestimation of trilateral SWIRR increased (0.08-0.29), while underestimation decreased (0.15-0.06).

Trilateral SWIRR has higher sensitivity and lower specificity for proximal caries, than occlusal SWIRR. For trilateral SWIRR, wavelengths around 1050 nm are more suitable, while 1550 nm is better for occlusal examinations. A combination of SWIRR at 1050 and 1550 nm may exhibit a balanced sensitivity and specificity for proximal caries.