Tooth brushing plays an important role in one's health, and particularly, in the prevention of oral diseases. It is a fundamental oral care technique in daily life; however, many elderly or handicapped people cannot brush their teeth without assistance from helpers. The purpose of this study is to develop an automatic teeth cleaning mouthpiece robot. One of the most common methods of brushing teeth is to move the toothbrush along the row of teeth. Hence, a mechanism to wipe teeth using sponges is designed and it consists of an eccentric cam, a wiper with sponges, and a rounded guide rail. This mechanism generates rounded wiper motions along the row of teeth. Furthermore, a safety system is designed to prevent aspiration. Brushing stops automatically when the user lifts his/her jaw up from the jaw supporter.