The typical patient have a yearly maximum to spend...$750 or $1000 or $1500 or $2000; sometime even $10,000 or unlimited. There's usually no deductible and no copay for exam, xray checkup, prophy, emergency. Typically there's a deductible (pay yearly) of $25 or $50 or $75 or $100 for filling, extraction, root canal, gum treatment, crown; they also have to pay the 20%-60% copay of the allowed amount. You can collect the non-allowed amount, if the patient is willing to pay, if you're not in a contract with their insurance company. Here's an example:
crown: $1000 (insurance allowed price)
-$50 (deductible)
-$500 (50% copay)
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$450 (your check from insurance)
$550 (you collect from patient)
If you charge $2000 and the insurance only allow $1000, you can collect an extra $1000 from the patient. Good luck collecting though.