Pushing down on the chin causes a reflex contraction in the mentalis
muscle, which has exactly the opposite effect - it closes the jaw!

IMO, a baby who won't open or can't open his jaw has a good reason for this
behavior or inability. The solution is to find out why, NOT to force him
and risk further trauma.

Linda J. Smith, BSE, FACCE, IBCLC
Bright Future Lactation Resource Centre
Dayton, OH USA
http://www.bflrc.com