What is coinsurance?
Coinsurance (sometimes written co-insurance) is the percentage of a covered dental procedure's cost that you and your plan each pay. It kicks in after your deductible is met.
In dental PPO plans, coinsurance is written as the plan's share, usually a 100/80/50 split. The percentages stand for what the plan pays, so your share is the inverse:
| Service type | Plan pays | You pay |
|---|---|---|
| Preventive (cleanings, exams, x-rays) | 100% | 0% |
| Basic (fillings, simple extractions) | 80% | 20% |
| Major (crowns, root canals, dentures) | 50% | 50% |
One detail that trips people up: coinsurance is figured on the lower of the dentist's actual charge or the plan's allowed amount (the UCR fee), not on the full billed amount when that bill runs above the plan's limit.
How it works
Once your deductible is met, every claim is split using the plan's coinsurance schedule. The plan sorts the procedure into a category (preventive, basic, or major), looks up the CDT code to find the allowed amount, compares the dentist's charge to that allowed amount and uses whichever is lower, then applies the plan's percentage to that figure and pays its share. You are billed the rest: your coinsurance share, plus any balance billing if the dentist is out of network.
Same crown, covered at 50% major, deductible already met. In network at a negotiated rate of $900: the plan pays 50% ($450), you pay 50% ($450), your total is $450. Out of network where the dentist charges $1,300 and the plan's UCR is $1,000: the plan pays 50% of UCR ($500), your coinsurance is 50% ($500), plus a $300 balance bill above UCR, so your total is $800. Same crown, same coinsurance percentage, $350 difference driven by network status.
What to watch out for
- Coinsurance and the deductible stack. Meeting your deductible does not end your obligation. You still pay your coinsurance percentage on every claim after that.
- Out-of-network dentists can add balance billing on top of coinsurance. Coinsurance applies to the UCR, not the dentist's full charge. The gap between the charge and the UCR is 100% yours, on top of your coinsurance share.
Frequently asked questions about coinsurance
80/20 typically refers to basic service coinsurance, the plan pays 80% of the allowed amount and you pay 20%. Full dental plans usually express three coinsurance tiers: 100% preventive / 80% basic / 50% major. The percentages represent the plan's share, so '50% major' means you also pay 50%.
After. You pay the full deductible first. Once the deductible is met, coinsurance applies to the remaining allowed amount. On a $200 filling with a $50 deductible and 80/20 plan: you pay $50 + 20% of $150 = $80 total. The plan pays $120.
No, your coinsurance payments do not count toward the annual maximum. Only what the plan pays counts. If you pay $500 in coinsurance on various procedures, that $500 is yours. The plan's $500 in payments counts toward the maximum.
Some plans offer improving coinsurance over years of continuous enrollment, for example, 50% major coverage in Year 1 stepping up to 70% in Year 3. This is called a 'graded' or 'step-up' coinsurance structure. Check your plan's benefit schedule or Summary of Benefits for any step-up provisions.
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