Intensity-modulated radiation therapy (IMRT) radiation treatment planning (RTP) requires accuracy. Metal artifacts are one of the factors that influence RTP. The metal artifacts from dental structures are problems at the level of the oropharynx, since these artifacts impair visualization of tumors or lymph nodes and change CT (computed tomography) values. We simulated RTP at the level of the oropharynx using CT images with and without artifacts from dental structures. Gantry tilt scanning was performed to avoid artifacts from dental structures and transverse images reconstructed from oblique images by gantry tilt scanning using a technique of multiplanar reconstruction (MPR) . The reconstructed transverse images were used for the RTP. The reconstructed transverse images were useful to obtain accurate target volumes and the RTP of two opposed equally weighted beams by correct CT values. As dose distribution was changed slightly by the metal artifacts, the use of CT images without artifact is recommended in RTP.