Application of infrared technique in identifying white spot lesions

White spot lesions are early – stage dental lesions which are difficultly identified and analysed by common diagnostic methods such as clinical examination or radiography. In contrast, in recent years, a number of research has showed that the infrared technique could be applied for identifying early – stage dental damages like white spot lesions due to the difference in optical properties between damaged and healthy tooth tissues. Sound enamel is nearly transparent under infrared light while damaged tissues appear darker. The aim of the present study was to apply the infrared technique to identification of white spot lesions at early stages. In this research, the optical system with 850-nm LEDs was designed and manufactured based on scattering and transmission techniques, and used for observing in vitro the tooth sample with white spot lesions. A number of 100 tooth samples were diagnosed with the infrared technique and traditional methods (clinical observation and radiography) at the same time. Then, Cohen’s Kappa coefficient was figured to evaluate the agreement in diagnosis between the mentioned methods. The low Kappa coefficient (only 0.01) indicates the low consensus between clinical – radiography assessment and the infrared technique. This result is reasonable due to the fact that the infrared technique is highly capable of detecting demineralized damages like white spot lesions whereas both clinical examination and radiography have low sensitivity in identifying this type of lesions.