Can your dentist tell your parents that u vape or smoke if your a minor ?

Depends on the state you live in and how they define "minor". Your post lists you as 20 and in my state you are an adult at age 18 and there must have a signed release in your chart for the doc/dentist to share any of your health info with anyone including your parents.

Your vaping can cause dry mouth and a build up of bacteria in oral cavity. This will lead to cavities and gum disease. Also headaches, coughing and shortness of breath. You don't need these problems at your age. Long term effects will hurt you. Stop and lead a healthy life.