Prescription drug coverage is a benefit of health insurance and any cost sharing would count towards your out-of-pocket maximum. Many health insurance plans now include pediatric dental coverage. If your child received pediatric dental services and your plan included that benefit, the cost sharing would count towards your out-of-pocket maximum.
Adult dental care and pediatric dental care not included in your medical health plan are likely covered by a separate dental insurance plan if you have coverage. Any cost sharing associated with this kind of care under a dental plan would not count towards your out-of-pocket maximum for your health insurance plan.