At birth, mental foramen opens:
Key concept:
At birth the mental foramen, opens below the sockets for the two deciduous molar teeth near the lower border.
This is so because the bone is made up only of the alveolar part with teeth sockets. The mandibular  canal runs near the lower border. The foramen and canal gradually shift upwards.
Below sockets of deciduous canines
In front of socket of deciduous canine
Below sockets of deciduous molars
Behind sockets of deciduous molars