1. A method for identifying one or more tooth regions, comprising: accessing a fluorescence image of the tooth; accessing a reflectance image of the tooth; combining image data for the fluorescence and reflectance images to obtain a combined image of the tooth, generating a complement image from a grayscale combined image of the tooth; generating an intermediate image by applying a morphological reconstruction operation to the complement image; generating a first threshold image by applying a thresholding operation to the intermediate image with a first upper threshold value and generating a first processed threshold image from the first threshold image; generating a second threshold image by applying the thresholding operation to the intermediate image with a second upper threshold value and generating a second processed threshold image from the second threshold image, the second upper threshold value being larger than the first upper threshold value; and identifying the one or more tooth regions using the first and second processed threshold images.