Rounded nipple pacifiers are long and slim, with a rounded tip on top that resembles a human nipple. Orthodontic-shaped pacifiers are more oval-shaped, with one flat side, to make it easier for your baby to suck and avoid future tooth problems. For breastfed infants, the rounded nipple shape is more similar to a mother’s nipple and could be a safer choice. The round type should be tried first, followed by the orthodontic design.