Are you self-employed? If you are a W-2 employee be aware that W-2 job work related expenses are not deductible anymore.
Dental expenses that you pay with out of pocket funds and are not reimbursed are entered as a itemized medical deduction on Schedule A. Only your total medical expenses greater then 7.5% of AGI can be deducted on Schedule A.
Your total itemized deductions must be greater than the standard deduction for your filing status to have any tax benefit.
Standard deductions for 2018
If you are not aware of what can be included in itemized deductions, see this FAQ: <a rel="nofollow" target="_blank" href="https://ttlc.intuit.com/questions/1901553-what-is-schedule-a">https://ttlc.intuit.com/questions/1901553-what-is-schedule-a</a>
The 2018 tax law has eliminated or capped a number of items which were previously deductible as an itemized deduction.