You may be able to purchase an individual dental policy. Some polices however may require a waiting period before it will pay for certain services. As fas as how the dual insurances pay as Here757 is referring too, it depends on how the coordination of benefits is administered with your current dental carrier, however that shouldn't be an issue as your son has already used his lifetime maximum on his first ortho treatment I would assume, so your husbands insurance would deny the claim and then your supplemental would pay whatever amount was eligible.