1.   His jaw fell slack.

2.   Jaws fall open, revealing braces on teeth, and a few hands shoot up with burning questions, prompting a raised-eyebrow caution from Ms. Lesher.

3.   One steel mogul drank radium to increase his sexual prowess until his upper jaw fell off.

4.   Their jaws fell open when the FBI, within hours, ordered up a high-tech trailer for the board to have as its own command center.