The IRS allows you to deduct unreimbursed expenses for preventative care, treatment, surgeries, and dental and vision care as qualifying medical expenses.  You have to claim the expenses in the year you paid them, so you cannot claim them on next year's taxes.

You can amend your return to add your dental expenses.  

How to amend (change or correct) a return you've already filed

https://ttlc.intuit.com/community/amending/help/how-to-amend-change-or-correct-a-return-you-already-...