Would in-office dental fluoride treatments benefit an adult who has both crowns (to protect margins) and natural teeth?

Topical Fluoride: Topical Fluoride treatments will help to some extent. The three most important things you can do is brush and floss properly and eat a healthy diet, limiting foods that promote tooth decay and periodontal disease. It's more important for patients who have dry mouths, sensitive teeth and poor oral hygiene as a supplemental way to better dental health.

Fluoride: Yes routine Fluoride rinses especially prior to bed would be helpful. A prescription strength Fluoride with tricalcium phosphate would also be helpful to help remineralize your tooth if a cavity starts. Ask you dentist.

Yes: While most often done on children's teeth, in office Fluoride treatments can help natural teeth of any age remineralize.