The phrase "haven't been to the dentist in 3 years" refers to the act of neglecting regular dental checkups for an extended period. Dental checkups are crucial for maintaining good oral health, preventing cavities, gum disease, and other dental problems.
Regular dental visits allow dentists to examine your teeth and gums, clean your teeth professionally, and provide preventive treatments such as fluoride applications and sealants. These measures help to keep your teeth and gums healthy, preventing the need for more extensive and costly dental work in the future.