Are dental insurance premiums, my dental co-payments, dental cleaning procedures not covered by dental plans, and bridges deductible? Do Medicare premiums paid count?

Yes to all the dental questions. See IRS Publication 502 - https://www.irs.gov/pub/irs-pdf/p502.pdf

Generally, dental treatments for good health are deductible - this includes the co-payments, the cleaning procedures, and bridges.

Generally, you can deduct health insurance premiums (including dental) that you paid with after-tax dollars. 

As for Medicare, please read the following:

"Medicare A

If you are covered under social security (or if you are a government employee who paid Medicare tax), you are enrolled in Medicare A. The payroll tax paid for Medicare A isn't a medical expense. If you aren't covered under social security (or weren't a government employee who paid Medicare tax), you can voluntarily enroll in Medicare A. In this situation you can include the premiums you paid for Medicare A as a medical expense.

Medicare B

Medicare B is a supplemental medical insurance. Premiums you pay for Medicare B are a medical expense. Check the information you received from the Social Security Administration to find out your premium.

Medicare D

Medicare D is a voluntary prescription drug insurance program for persons with Medicare A or B. You can include as a medical expense premiums you pay for Medicare D." (see page 9 in Pub 502, link above).