Because she goes to the dentist regularly, she rarely gets toothaches.
Literal
She [topic-は] regularly dentist [to-に] go [because-ので], rarely teeth [subject-が] painfully does-not-become.
Two useful adverbs: 定期的に ('regularly/periodically') and めったに~ない ('rarely/seldom'). The ~ので connects cause to result. 歯が痛くならない uses the ~くなる pattern (adjective + なる = 'become X') in the negative — 'doesn't become painful.' A practical, real-world sentence showing how preventive care avoids problems.