Computerized tomography (CT) number (it is a normalized value of the x ray absorption coefficient of a pixel in a computed tomogram) and the effective atomic number (Z(eff)) of teeth [enamel outer surface (EOS), enamel middle (EM), enamel dentin junction towards enamel (EDJE), enamel dentin junction towards dentin (EDJD), dentin middle (DM), and dentin inner surface (DIS)] have been calculated for photon interactions by a direct method in the energy range of 1 keV-100 GeV using the computer program, WinXCOM. The sum of the computed values are tabulated. The estimated CT numbers are tabulated. All of the selected materials show an almost constant Z(eff) value in the energy range 500 keV to 1.5 MeV. Also, it is expected that the computed CT numbers are useful in medical diagnosis. Dosimetric implication of mass attenuation coefficient in teeth has also been discussed.