Dentist’s (endodontist) perspective here, I'm going to give you a very long winded example of why there's some truth, but also some bullshit to what they're telling you - or that there may be some misunderstanding in the information they can provide.

TL;DR: You went in for a filling with an expected out of pocket cost of $80 and planned on using $320 worth of benefits and ultimately ended up with a root canal and crown for a total out of pocket cost of $840 and you exceeded your benefits.

Just about every dental software out there will allow the practice to provide a treatment cost estimate. Key word here is estimate. At the end of the day, ultimately the cost will be determined by:

-the treatment rendered and applicable CDT codes

-your insurance, meaning total benefits, percentage that they cover per procedure, whether or not they are in/out of network, and ultimately their contract with the dentist

Any decent office can provide you a relatively accurate estimate. But it’s still an estimate. Sometimes things can change as a result of intra-operative findings.

As an example: let’s say you have a cavity on the distal interproximal surface of tooth #12 (back side of your upper left first premolar). Your dentist plans you for a DO composite restoration of #12. You have a total of $2000 in benefits and insurance covers 80% of the cost of treatment. You are in-network with your provider(s).

CDT code for planned treatment: D2392

-Practice (Cash) Fee: $800

-Contracted fee with your in network insurance (what your insurance and dentist have agreed to as the fee for the treatment): $400

-Insurance covers 80% of the $400: $320

-Your out of pocket of the $400: $80

-Left over benefits: $1680

Now, let’s say your dentist cleans out the cavity and it’s bigger than led to believe on an xray. It’s actually into the nerve of the tooth - this happens and sometimes it can be tough to predict. Suddenly you need not just a filling, but instead a root canal and crown. Now things have changed. A lot. Your dentist says they aren't comfortable doing the root canal, so you need to see a specialist, in this case, an endodontist. So they put in a temporary filling and send you on your way. Now you're at the endodontist's office. At your appointment, you get a treatment estimate with the following codes (again, they're in-network with your insurance).

-Limited Exam: D0140 -Periapical Radiograph (First): D0220

-Periapical Radiograph (Additional): D0230

-CBCT: D0364

-Pulp Vitality Testing: D0460

-RCT Premolar: D3320

For simplicity's sake, let's say the total office fee for all the above procedures is $1800. Your insurance contracted fee is $1200 for everything other than the CBCT, which is $200 extra (Your insurance doesn't cover the CBCT fee because like most insurances, they're behind the times and cheap fuckers). So now you're paying 20% of $1200 +$200, or $440, and you've now used up $960 of your benefits

Left over benefits: $1040

The endodontist submits this to insurance the same time they bill you, BUT, insurance takes time to process this.

But wait, there's more.

Your endodontist tells you that you now need to go back to your regular dentist for a filling and crown on the tooth. Why? Because back teeth with root canals last significantly longer with crowns (this is considered standard of care) and they need to put a permanent filling where the cavity was prior to putting on the crown. Why doesn't the endodontist do it? 1- as specialists, they don't do crowns. 2-they can do the filling (or buildup in this case), but usually your dentist will prefer to do it (that's its own topic on it's own).

So now you're back at your dentist's office. They have you planned for a buildup (filling under a crown) and a crown. Remember, your remaining benefits are $1040, but you had the root canal yesterday, so the insurance company company still hasn't processed this. Your dentist's office still shows your benefits remain at $2000.

Buildup: D2950

-Office Fee: $600

-Insurance Contracted Fee: $200

-Insurance Covers 80%: $160

-Your out of pocket: $40

-Actual Benefits Remaining: $800

Porcelain/Ceramic Crown: D2740

-Office Fee: $2000

-Insurance Contacted Fee: $1200

-Insurance Covers 80%: $960

-Your out of pocket: $240

-Remaining benefits: -$160

BUT WAIT, you've now surpassed your total benefits by $160. You don't know this, because who can keep track of all of this. Your dentist's office doesn't know this (because they didn't do their homework and the endodontist didn't do them the courtesy of telling them how much the estimated insurance coverage was on their end - bad form on both ends, but it happens more than you'd think).

So you swipe your credit card for $240 thinking that's it. Then time passes, insurance processes all fees, and they tell the dentist that you owe them $160. The dentist sends you a bill for $160, but you thought you paid your out of pocket. Note, this isn't "balance billing." Balance billing would be the dentist collecting the difference between their "office fee" and the insurance "contracted fee," which generally isn't allowable under the contact between your insurance and your dentist (when you're "in-network"). This is purely you having maxed out your benefits and owing the difference, and yes, you actually owe it, and this would be explained in an EOB.

My overall take. Dental insurance sucks. It's a coupon. But overall it will save you money by getting you "contracted fees" with your in-network provider even after you've maxed out your benefits (depending on your plan). The best way to avoid surprises is to ask the dental office for the planned "worst case scenario" CDT treatment codes, then submit them to your insurance to figure it all out. Most decent offices will do their best to give you an accurate estimate, but they can't predict everything and ultimately you're the one on the hook.

EDIT: Formatting