If i get braces in mexico, will a dentist in the u.s. be able to tighten them and do check-ups?

Why would they?: The ortho will not take the liability of another's work. The professional adjustment is what you are paying for more than the hardware.

Don't bother: Either have your treatment in mexico, or the us, and in only one office, regardless of the country.

Very unlikely &:: First, i assume that the reason you are considering having orthodontic treatment in mexico is to save money. If that's the case, treatment usually requires a year or more of treatment. Are you prepared to stay there that long? Even if you do, consider the quality of treatment and not just the cost. Most orthodontists will be reticent about treating someone else's case. All trouble ahead !