My maintain oral hygiene is use a gagrin because gagrin is kill the bad tooth germs.
So gagrin is very perfect.
Here's your corrected composition, Jimmy. Please take a look at the corrections below. Have a good rest there! 
How do you maintain your oral hygiene?
My maintain oral hygiene is use a gagrin because gagrin is kill the bad tooth germs.
So gagrin is very perfect.
>>> I maintain oral hygiene by gargling because it kills bad germs in my teeth. So, gargling is very effective.
>>> OR: I maintain oral hygiene by gargling because it kills harmful bacteria in my mouth. Gargling is a very effective way to keep my teeth clean