1)
What are "Mesal'os"?
1.
Metzudas Tziyon: This is like "Malta'os Kefirim" (Tehilim 58:7 - teeth), just the letters are reversed.
2)
How would he break the teeth of Avel?
1.
Malbim: I would cast the prey from between his teeth and return it to the owner. For what he already ate, I would break his teeth, i.e. punish him for his oppression.
