If I am previously covered with BCBS health insurance, and principal dental, and I switch jobs.....Will COBRA also cover my dental if I need it to?

If you switch jobs, in the long term it depends on if your new employer offers group dental coverage. If they do, without any exclusion or limitation with respect to any pre-existing condition, then you would no longer qualify for the dental insurance extension.

Dental insurance is a scam. Take care of your teeth like everything else, and only pay for periodic cleanings. You'll be fine.