Final answer:
The insured has a dental plan that covers a full-series mouth x-ray without any cost-sharing, but requires a deductible for filling cavities.
Step-by-step explanation:
The dental plan that the insured has is a plan that does not require the payment of co-insurance or deductibles for a full-series mouth x-ray. However, the insured does have to pay a deductible to get their cavities filled. This means that the plan provides coverage for preventive services like the full-series mouth x-ray without any additional cost-sharing, but requires the insured to pay a deductible for restorative services like filling cavities.