Do the primary dental insurance rules govern the allowed charges from the dentist?

The answer to the question, is it depends. State laws on coordination of benefits (CoB) can impact the answer, but there is a general rule of thumb. If the dentist participates in a network that is connected to the patient's coverage--whether that coverage is primary or secondary, the participating network contractual relationship determines the amount that can be collected from the patient.

Here's a table that was developed by the National Association of Dental Plans outlining various CoB scenariOS and what determines the charges to patients under each.

PATIENT COVERAGEWHAT THE DENTIST CHARGES THE PATIENTPrimary and secondary coverage are both DPPOs; Office participates in both network plans.The DPPO allowances of the primary plan.Primary coverage is a DPPO, and the secondary coverage is an indemnity plan.The DPPO allowances of the primary plan.Indemnity plan is primary, and the secondary coverage is a DPPO.The DPPO allowances of the secondary plan. Primary coverage is an DHMO, and the secondary is an indemnity plan.The DHMO patient co-payments. (The secondary indemnity plan may cover all or most of these co-payments.)Indemnity plan is primary, and the secondary coverage is an DHMO.The DHMO patient co-payments. (The primary indemnity plan may cover all or most of these co-payments.)Primary coverage is a DPPO, and an DHMO is the secondary plan.The DPPO allowances of the primary plan.Primary coverage is an DHMO, and the DPPO is the secondary plan.The DHMO patient co-payments. (The secondary DPPO plan may cover all or most of these co-payments.)
NOTE: Discount dental plans are not subject to COB laws and regulations as they are not insurance products.