i would like to travel to africa as a volunteer, how should i do this? I am a dentist?

contact the embassy of the country that you want to travel to or there should be african organizations in the US that could help you.

Try the world health organisation,

Try NGOs operating in Africa and UN agencies such as UNICEF, WHO, etc. If you can do something for kids, it may be easier as kids health is a major problem - may be target dental problems that kids have due to malnutrition, sanitation, etc.
You could also consider teaching.

i also would want that. sign up online in an aid releif organization. there is organizations that require you to finance on your own though.

A dentist I used to work with did this. He went with his church and I think they went through Doctors Without Border. You could check through them first and they could direct you possibly who to contact to do this.