Can I claim my dental expenses from Mexico?

Maybe.  You can deduct dental work performed overseas as long as it is not "unnecessary cosmetic dental work".  See possible eligible IRS deductions below.

If you itemize, you can deduct medical expenses that exceed 7.5% of your adjusted gross income (AGI)

Enter Medical Expenses:

1. Open your return (if not already open)
2. Enter "medical expenses" or "Schedule A" in the Search box.
3. Click on "jump to medical expenses (or Schedule  A)" link.
4. Enter your information.

"You can include in medical expenses the amounts you pay for the prevention and alleviation of dental disease. Preventive treatment includes the services of a dental hygienist or dentist for such procedures as teeth cleaning, the application of sealants, and fluoride treatments to prevent tooth decay. Treatment to alleviate dental disease includes services of a dentist for procedures such as X-rays, fillings, braces, extractions, dentures, and other dental ailments."  Page 7.

The IRS has an extensive list of what you can and can’t deduct.  IRS Pub. 202 Medical and Dental Expenses (beginning on page 5).