Comment On Dental Opening Closing Mouth Since Medieval Times

Exhaling with mouth opened or closed, a pair of symmetrical systems, the changing between which is a significant reflection of Chinese phonetic development, is to distinguish various rhymes. This paper analyzes the dental characters' converting of these two systems since mediaeval times, and shows historical development of dental according to the angles of mouth opening or closing.This paper, adopting historical comparison method, separates dental developing process into three main times as medieval, modern and contemporary on one hand, and two transitional phases from medieval to modern times, from modern to contemporary times on the other hand. With the contrast of opening or closing the mouth in different periods lengthwise, the author, consequently, figures out six groups of dental characters having the change of opening or closing the mouth during history processing, and depicts its' development track. Besides, the author expounds the development of dental initial consonant.