Yes but...
If you take a tax deduction in 2016 on the basis of the fact that you had the expense in 2016, then the payments you make with HSA money have to be added back to your taxable income, because taking a deduction and paying with tax-free HSA is double dipping. If you plan to use the HSA to make the monthly payments, you should just skip the medical expense deduction.
And there is one other point I forgot to add: you can only use the HSA to reimburse the dental care if the HSA was open when you actually received the care (even if the HSA did not have enough money to pay for the care.) But if you only opened the HSA after the dental care was provided, you can't use the HSA to pay the bill.
