Because they pulled their teeth out to treat cavity
① "Only the royal family was allowed to eat pears until the French Revolution." =「フランス革命まで王族だけが洋ナシを食べることが許されていた。」
Only ~ = ~だけ
Royal family = 王族、王家
Allowed to ~ = ~することが許される、~できる
Eat = 食べる
Pear = 洋ナシ
Until ~ = ~まで
The French Revolution = フランス革命
② "Back then, they pulled their teeth out to treat cavities, and pears were eaten as a medicine to heal the wound." = 「当時、虫歯の治療で歯を抜いてしまっていたため、洋ナシは傷を治す薬として食べられていた。」
Back then = 当時
Pull (someone's) tooth out = (誰かの)歯を抜く
Pull (someone's) teeth out ーー>複数形
Treat = 治療する
Cavity = 虫歯
Eaten = 食べられた
Medicine = 薬
Heal = 治す
Wound = 傷