Coordination of Benefits: Why Two Dental Insurance Plans Don’t Always Mean Better Coverage

If you’ve ever gone to the dentist, had work done, knew you had two dental insurance plans, and still ended up owing more than you expected — you’re not alone.

When that happens, it’s often because of something called Coordination of Benefits, or COB.

Many patients have never heard that term before, even though it can have a big impact on what insurance pays and what you ultimately owe.

So, What Is Coordination of Benefits?

Coordination of Benefits is the process insurance companies use when more than one insurance plan applies to the same dental treatment.

Instead of both plans paying independently, one plan is labeled primary and the other secondary. The way those two plans interact — and how much each one pays — is determined by COB rules.

On paper, this is meant to keep things organized. In real life, it often creates confusion.

What Coordination of Benefits Was Supposed to Be

COB was created for a simple reason:
to prevent someone from being paid more than the actual cost of their dental care.

That’s reasonable. Insurance was never meant to turn treatment into a profit.

The original idea was that one plan would pay first, the second plan would help with what was left, and together they’d cover the cost — but not more than that.

That’s the version most patients still picture.

What Most Patients Don’t Realize

There isn’t one universal rulebook for Coordination of Benefits.

Each insurance company writes its own rules, inside its own contract. As long as they follow what’s written there, they’re generally allowed to apply COB in the way the policy describes — even if the outcome feels confusing or disappointing to patients.

There are organizations like the National Association of Insurance Commissioners that publish suggested guidelines, but these are models, not laws. Insurance companies aren’t required to follow them exactly.

Some plans follow those models closely, while others apply different interpretations.

It becomes even more restrictive with employer-sponsored plans governed by the Employee Retirement Income Security Act. These plans operate under federal rules and are largely outside the reach of state insurance departments, which means options for appeal or review can be limited.

For fully insured plans, regulators such as the Texas Department of Insurance mainly check whether the insurance company followed the terms of its own contract — not whether the outcome feels reasonable from a patient’s perspective.

How This Plays Out in Real Life

What I see most often looks like this:
the primary plan pays something, and the secondary plan determines that amount satisfies its responsibility — even though the patient still owes money.

Sometimes the secondary plan bases its calculation on its own fee schedule rather than the actual cost. Sometimes it offsets what the first plan paid instead of adding to it. Sometimes payment is reduced because another plan could have paid more, even when it didn’t.

All of this can be allowed under the policy language.

From the patient’s side, it can feel like the rules changed after the visit was over.

Why This Is So Frustrating

You paid two premiums.
You followed the rules.
You didn’t try to game the system.

And yet, the coverage you expected just wasn’t there.

If that feels frustrating, you’re not wrong for feeling that way. Coordination of Benefits isn’t intuitive, and it’s rarely explained clearly before treatment takes place.

The One Thing I Wish Patients Knew

Having two dental insurance plans does not mean the benefits are added together. It doesn’t guarantee lower out-of-pocket costs, and it doesn’t mean the plans automatically fill in the gaps for each other.

More often, it means additional rules behind the scenes — rules that are structured to prevent overpayment by insurance plans, rather than to ensure full coverage for patients.

That gap between expectation and reality is where most frustration comes from.

Coverage and coordination rules vary by plan, and this explanation is meant to describe common patterns rather than any single insurance policy.

For more insurance education check our dental insurance FAQ.