The orthodontist and periodontist expenses can be included in your medical expenses. Only the amount of medical expenses over 10% of your AGI is deductible (7.5% if you are 65 or older). In TurboTax enter the full amount of expenses that were not paid or reimbursed by insurance. TurboTax will subtract the appropriate percentage of your AGI (Adjusted Gross Income).
Medical expenses are an itemized deduction. They will not make any difference in your tax unless your total itemized deductions are more than your standard deduction.