ZBrushCentral

Cut out bits of a scanned mesh - technique help

Hi all, I’ve bought a scanned skull from 3dscanstore, and I need to adjust the model a bit so that the teeth have the appropriate space between them - I don’t use zbrush very often and wondered if anyone could suggest the workflow that they would use? especially with regards to filling in the sides of the teeth where I will end up creating holes.
any advice would be really appreciated!teeth.PNG

Ive tried masking out areas then deleting the faces, this leaves me with holes on the side of the teeth that are really hard to view - using the close holes function then also closes the holes I’ve intentionally made. Is there any other way I can attempt this?!01.JPG02.JPG