(1) Normal seat stage. At first, there was no dental unit chair specially used for dentistry. Instead, on the basis of ordinary seats, ordinary seats were transformed into dental unit chair through some supporting materials. For example, the slightly modified dental unit chair appeared in 1790. It has a fixed head support on the upper part, the back can't adjust the angle, and the right armrest can be used to place medical devices.

(2) Adjust the dental unit chair by hand. In 1875, the hand-held adjustable dental unit chair was used to adjust the height of dental unit chair through the handle on the right side. On the left side, there was a mouthwash system and a spittoon, and there was a tray for medical equipment. Some hand-held adjustable dental unit chairs even had lighting equipment.

(3) The oil pump regulates the dental unit chair. In 1887, the dental unit chair with oil pump adjustment appeared in the United States. The angle can be adjusted by using the foot pedal, and the height of dental unit chair can be automatically raised and lowered, which is very practical.

(4) Electric adjustment of dental unit chair. Compared with the oil pump drive, the electric drive is cleaner and more hygienic, and the stains caused by oil stains are unpredictable. The electric drive dental unit chair avoids this problem and brings a higher quality operation environment.