The movement range on the semi adjustable articulator and the movement range in anoral were measured. And then I studied to analyze the gap. I got wax records by themovement on the semi adjustable articulator, the movement in an oral. I measured thedistance of the cusp tips that are close to the mesial direction and the distal direction, thebuccal direction and the lingual direction then I compared gaps.As I saw results on data, I knew that the semi adjustable articulator represented therange of mandibular movement restrictively. I could find the decisive contradiction thatthe sliding movement finished on the semi adjustable articulator although it did not finishin an oral. When the sliding movement does not reappear exactly, it brings a fatal failureto the dental prosthesis. In addition it is impossible that the semi adjustable articulatorrestores the movement in an oral because the lateral condyle inclination and thehorizontal condyle inclination are appeared to be straight. Therefore dental prosthesisseswere made by the semi adjustable articulator, they will interfere with a mastication.I have obtained the following results;1. The distance of sliding movement on the semi adjustable articulator showed shorter than the distance of sliding movement in oral. This means the increase of cusp inclinationof the dental prosthesis that was made on the semi adjustable articulator. Therefore,when the lateral movement occurs in oral, there is a possibility to become the prematureas the increase of cusp inclination. 2. The difference in the range of movement is considered as the gap that is madebecause the movement only can be occurred as straight in the semi adjustable articulator.3. When the dental technician understand mandibular movement and articulatordeficiencies, they can attain proficiency in use of the articulator and reduce the gap.