I have a back molar with a cracked filling that needs a crown. It happens that that tooth has a #5 gum pocket. Is it OK to put a crown on that tooth or should I take care of the gum first?

What does your dentist say ?

I'd see a periodontist about the gum pocket first.

They will probably want to address the gum issue first. That is a pretty deep pocket beside the tooth. But, yes, there is a natural progression to these procedures and a professional will determine this.