My then-minor daughter had braces 2008-2010. Her father (my ex) assumed fiscal responsibility for payment and dealt directly with the practice.

There are several issues that are not addressed in your inquiry and thus, it is difficult for me to fully advise you.  Please consider the below some preliminary guidance.  I would suggest, especially because of the possible collection efforts, that you bring all relevant documents and information to an attorney and have the attorney review.  The attorney would be in a position to more properly advise you. From the outset, since your husband signed the contract, he is certainly liable.  But, either during or since your divorce, was there an agreement or support order issued which outlined who was responsible for medical costs and expenses.  In part, the ultimate liability would also be dependent on the support order and/or agreement. Regardless of the contract and/or a support order, there are laws in Pennsylvania which provide that relatives of an indigent person (someone not able to pay their own medical bills) are responsible for the bill - that would include a parent.  Thus, the practice could potentially employ this area of the law to hold you responsible.  Certainly, if you were to be sued, you would want to consider joining him in any action that is filed.  Have you spoken with the practice and shared the relevant circumstances as to his responsibility?  Have you been in touch with your ex about his responsibility for the bill?  I hope that the above has provided some preliminary advice.  Marla D. Sones