my child is coming to 4months old and currently direct latching full bf. im curious to know how to direct latch once bb teeth starts appearing... will bb bite on..

Theorectically, it's physically impossible for baby to breastfeed and bite at the same time, because his/her tongue covers the bottom teeth/gum when baby is nursing. Most of the time, babies never bite too much but do note that biting is a behaviour that will occur, usually when they are teething. If baby bites, gently stop nursing and stay calm. Use positive words and don't freak out -- perhaps say things like, "Oh you don't want to nurse anymore now?" and pause the nursing session. In the long run, baby will hopefully know that biting is not desirable.