Permanent teeth

Japanese: 永久歯 - えいきゅうし（英語表記）permanent tooth

These are teeth that replace milk teeth and do not fall out for the rest of a person's life. There are 32 teeth in total, 8 on each side, symmetrically. From front to back, they are named central incisors, lateral incisors, canines, first and second premolars, and first, second and third molars. Of these, molars grow in the back where milk teeth were not, and embryologically they belong to milk teeth, but because they are used throughout a person's life and do not fall out, they are treated as permanent teeth. Permanent teeth are larger and harder than milk teeth, and have narrower pulp cavities. Incisors and canines are similar in shape to their respective milk teeth, but premolars are quite different from milk molars. They erupt from around 6 to 7 years of age, first with the first molars, followed by the incisors, premolars and canines, and the second molars at around 12 years of age. The third molars, also known as wisdom teeth or commonly known as third molars, grow in around the age of 18 to 24, but many people are missing them due to degeneration.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

乳歯と交代して，以後一生涯生え替わらない歯をいう。上下左右にそれぞれ対称的に8本ずつ，合計 32歯ある。前から奥へ向って，中切歯，側切歯，犬歯，第1・第2小臼歯，第1・第2・第3大臼歯と名づけられている。このうち大臼歯は，乳歯がなかった奥に生え，発生学的には本来乳歯に属するが，生え変ることなく生涯使用する点から，永久歯として取扱われている。永久歯は乳歯より大きく，硬く，歯髄腔が狭い。切歯，犬歯はそれぞれの乳歯と形が似ているが，小臼歯は乳臼歯とかなり異なっている。萌出は6～7歳頃からまず第1大臼歯，次いで切歯，小臼歯，犬歯と年を追って生え，第2大臼歯が 12歳頃生える。第3大臼歯は智歯あるいは俗に親知らずともいい，18～24歳頃に生えてくるが，退化のため欠如している人も多い。

出典　ブリタニカ国際大百科事典小項目事典ブリタニカ国際大百科事典小項目事典について　情報

<<: Eikyuji Temple

>>: Edictum Perpetuum