My ex-husband, an E-7 in the Army said he didn't have to help me with the kids' medical and dental expenses. A couple of years ago, my son had to get braces and now it is my daughters turn. According to the divorce decree, it says he is responsible for providing health insurance for them and we both make decisions regarding medical and dental procedures. However, it doesn't specify anything about who pays for the expenses.
Hopefully you can work out so that you can at least split the expenses 50/50. The military offers mediation through family support services if you cant come to an agreement.
Actually I am pretty sure if it says he is responsible for keeping medical insurance on him then he has to pay the medical cost or at least tricare does. As for the dental part I am not sure since that is another type of insurance. You could take him back to court to help get it paid for I am sure.
My step-son is covered under Tricare and United Concordia (the dental plan). In the divorce decree it states that whatever Tricare does not cover she is responsible for. Unless you live near a military base I assume your children are in Tricare Standard rather than Prime? I believe that United Concordia covers about 1/2 of the cost of braces but you have to use one of their orthodontist after your referral from the dentist is put in.