A combination of near - infrared and fluorescence techniques for detecting early tooth lesions

Abstract

In dentistry, X-ray method has been considered as the gold standard for identifying different types of structural damage in teeth. However, X-rays not only have adverse effects on patients’ health but also have failed in detecting small and early-stage lesions due to the low sensitivity of the method to these types of lesion. In order to overcome the disadvantages of X-ray method, in recent years, the infrared and fluorescence techniques have been developed strongly due to the fact that the optical properties of damaged tissue under infrared and ultraviolet lights are significantly different from those of sound dental tissue because of the demineralization of damaged tissue. The aim of the present study was to apply the fluorescence and infrared techniques to diagnosis of dental lesions at early stages. In this study, the optical systems with 850-nm LEDs and 365-nm LEDs which were applied for infrared imaging and luminescence imaging, respectively, were designed and used for diagnosing in vitro different types of early-stage lesions such as white spot lesions, dental plaque and lesions under restoration. A number of 68 tooth samples were assayed with infrared technique, fluorescence technique and clinical observation combined with radiography at the same time. Cohen's Kappa coefficient which was obtained with Statistical Package for the Social Sciences program was used to evaluate the agreement in diagnosis between the mentioned methods. The statistical evaluation showed that Kappa coefficients between traditional methods (clinical examination combined with X-rays) with optical techniques including infrared and fluorescence techniques were 0.147 and 0.235, respectively. These results suggest that all the lesions analyzed in this study were at the early stages and could not be detected by both visual inspection and X-rays, whereas the infrared and fluorescence techniques could be more sensitive to these types of lesion due to the fact that the optical techniques are able to detect early signs of demineralization of damaged tissue.