My dentist treated a cavity I had without disrupting the nerve.
I had some treatment for a cavity and the dentist did it in a way that didn't affect the nerve.
この場合、次のような言い方ができますよ。
ーMy dentist treated a cavity I had without disrupting the nerve.
「歯医者さんは神経に支障が来さないよう虫歯の治療をした」
ーI had some treatment for a cavity and the dentist did it in a way that didn't affect the nerve.
「虫歯の治療をしてもらったんだけど、歯医者さんは神経に影響のない方法でやってくれた」
ここの「神経を残すやり方」は without disrupting the nerve や a way that didn't affect the nerve を使って表現できると思います。
ご参考まで！
カナダ 
