Depends on the teeth. Are the lines between each tooth going to be a t-junction to the top & bottom edge, or are they going to be more of a y-junction where each tooth has rounded or angled corners?
If a t-junction (like human teeth), it is easy to make one large shape for all the upper (or lower) teeth and just add the vertical lines after to define each tooth.
If you want more detail, rounded corners or sharp pointed teeth, it is easier to create them separately. Trying to add the saw-tooth details for the top/bottom edge in a single vector line will be more difficult to accomplish.
The mouth would be one big circular shape layered underneath the teeth.