There is provided a dental apparatus including a light source for emitting a light to irradiate at least one of a tooth, a gum, a plaque and a calculus of an oral cavity, a light detector for detecting fluorescence from the oral cavity emitted to the light irradiated from the light source, and a control unit for outputting first data for visualizing a temporal change in a fluorescence intensity based on the fluorescence detected by the light detector. Also, there is provided a calculation method including irradiating an excited light, detecting a fluorescence intensity, and calculating a temporal change in the fluorescence intensity in a depth direction.
