My divorce decree states that my ex and I split MEDICAL bills for our children NOT covered by insurance

Courts regularly consider those uninsured medical expenses that are divided between parents if recommended by the dentist.

I don't necessarily agree with the earlier post. IF a DENTIST prescribed braces, then it would have been for a "medical" reason - i.e., the braces were needed to correct a dental defect. That would clearly be a "medical" expense, subject to your requirement payment. Most braces are not installed for that reason, but, rather, for cosmetic reasons, which is why your insurance denied the claim. I've had this issue come up on several occasions, and my advice is usually this - if you were not consulted beforehand and did not approve of the procedure (which really should be required for ALL expenditures of a non-emergency nature), I'd advise to not pay your "half" of the expense since (a) you weren't consulted, and (b) it is not a medical or dental procedure necessary for the child's health - it's a cosmetic procedure only. Your ex may either file this with support collections for reimbursement or take you back to court, so you have to balance that fact with your refusal, but I'd still say no, unless your ex can prove this was a necessary medical procedure.

Are you unwilling to split the cost because you legitimately cannot afford to pay for the expense and the other parent is easily able to afford the expense on his/her own? While the law may allow you to avoid paying 50% of this expense, I would urge you to consider why it is you don’t feel you owe it to your child to pay for their braces. And you should look at it as what you owe your child, not what you owe your Ex. A child who is old enough for braces is definitely old enough to be aware of your unwillingness to contribute to their cost which may (or may not) cause the other parent financial hardship. Does the few thousand dollars you might save (and I stress the word “might”, as you won’t be saving anything if you have to go to court over this) outweigh the damage you could potentially do to your relationship with your child (and other children) due to a battle over whether or not you are legally obligated to pay half of this bill? Even if both you and your Ex are financially well off and/or you pay the maximum in child support each month, the consequences of your decision on how you handle this and other support and parenting time situations can have long-term consequences on things far more important than your bank account. When deciding what battles to fight in a co-parenting situation, you need to always keep in mind how your child might perceive—and possibly completely misunderstand—the situation and how they may be hurt by your action or inaction. If you truly can’t afford to pay for braces (and your lifestyle reflects that), that is a talk your child can understand. If you “can’t afford” braces because you’re taking your new spouse to Hawaii for a month or because “that’s what you pay child support for”…expect that it will cause some damage to your relationship.