implantation dip on bbt ?

Lovemylife • Mom to two awesome girls. 1 MC. Had my rainbow baby boy 6/5/2017!!!! So in love 😍
So I keep hearing and reading about when implantation occurs there will be a dip on bbt chart. This got me wondering. Does this dip have to occur if you implanted? Can you b pregnant without having one? Just curious. What do you ladies think!