Do people who have good dental hygiene live longer than ones who don't?

Sure: The oral-systemic link has shown that periodontal gum disease can lead to various medical conditions. Also, people who have teeth, as opposed to standard removable dentures, can chew their food better and digest better to absorb the nutrients. So see your dentist and get on a great oral hygiene program.

Yes: Dr. Charles mayo of the famous mayo clinic is reported to have said over 90 years ago, that "if you keep your own teeth you can expect to live 10 years longer". Good oral hygiene should help to keep teeth a lifetime. Remember decay and periodontal disease are both infections and you must learn the proper way remover the infection. Ask your dentist or hygienist to teach you and not just show you.

Maybe not, but...: They have a better quality of life.

Correlation: Good oral hygiene doesn't prevent many diseases, however people who have great oral hygiene also tend to take better care of themselves.

Correlation: There are no guarantees & lots of other factors to consider, but statistically speaking the answer is yes for a few reasons. 1. Poor oral hygiene creates inflammation & pathogen overgrowth which is linked to several medical issues. 2. People who care about their dental health tend to also care about their general health\life style. 3. Healthier teeth & gums allow for better chewing and nutrition.