Yes, you can deduct supplemental dental insurance through a different provider if you itemize and the total expenses for you, your spouse, and your
dependents exceed 10% of your adjusted gross income (7.5% if you're 65 or
older as of December 31, 2016). The deduction is limited to the expenses above
and beyond this amount.
See Deducting Medical, Dental, and Vision Expenses
You can claim medical expenses paid for your mother in law if you provided over one half of her total financial support in 2016.
You may also claim your mother in law as your dependent if:
- You provided more than half of her
support in 2016
-
She earned less than $4,050 in
gross taxable income. (Social Security income generally doesn’t count
here.)
- She lives with you 365 days in the year or is
related to you. 32
- She isn’t a dependent on someone else’s
tax return.
- She isn’t filing a tax return
with a spouse (married filing jointly).
- She is a U.S. citizen, resident alien,
national, or a Canadian or Mexican resident
See Rules For Claiming Dependents
