Are dental expenses allowed?

Yes. But You can only deduct the amount of unreimbursed Medical Expenses you actually paid over 7.5% of your AGI.  And then all your itemized deductions have to be more than the standard deduction to get any benefit (so you would only be getting the benefit of the amount that puts you over the standard deduction).  And since the Standard Deduction is increased more people will not need to Itemize.

For 2023 the standard deduction amounts are:

Single 13,850 + 1,850 or 65 and over or blind

HOH 20,800 + 1,850 for 65 and over or blind

Joint 27,700+ 1,500 for each 65 and over or blind

Married filing Separate 13,850 + 1,500 for 65 and over or blind

Yes, any amount paid in excess of reimbursements is an itemized deductible medical expense.   If you itemize, the amount of your medical expenses in excess of 7.5% of your AGI are deductible on Schedule A.   Where do I enter medical expenses?