Are dental payments only a part of medcare part b?

Medicare Part B premiums paid are only for medical insurance and are a deductible medical expense if you itemize.

If you have Dental Insurance and are paying the premiums for that insurance those premium payments are also a deductible medical expense if you itemized.

original medicare does not cover most dental - medicare A&B.   only some medicare advantage plans - medicare C cover dental. however,  i'm unsure why you're asking.  

If you are entering a SSA1099, any amount you paid for Medicare is going to flow to the medical expense section when you enter the SSA1099.  So check to see if you are having Medicare Part C or D deducted from your Social Security; do not enter it twice.