škripiti

1. to creak; to squeak
   Vrata škripe svaki put kad ih otvoriš. — The door creaks every time you open it.
   Stari pod škripi pod nogama. — The old floor creaks underfoot.
2. colloq. (of affairs, relationships) to not go smoothly; to have problems
   U njihovom braku već neko vreme nešto škripi. — Something has been off in their marriage for a while.

For teeth, škrgutati zubima is the more usual expression.