D3347 Dental Code: Premolar Root Canal Retreatment

What D3347 covers

D3347 reports nonsurgical endodontic retreatment of a permanent premolar. The tooth was root canaled before, that treatment failed, and the dentist reopens it through the crown, takes out the existing filling material, re-cleans and reshapes the canals, and refills them. The buildup and the crown that follow are separate codes.

What makes it retreatment is that the canal system was previously obturated. Two cases sit close to that line and are not:

• A tooth that was opened but never filled. If another office accessed the premolar, medicated it, and temporized it without ever obturating, most carriers read the completion as initial therapy under D3320 rather than a redo. Get the prior office’s notes before you decide.
• A tooth whose only endodontic history is pulpal therapy. A pulpotomy or pulpectomy on the way to a root canal is not a completed root canal, so the definitive treatment that follows is still initial therapy.

Failure of the first treatment is the clinical trigger: persistent apical pathology, a canal missed the first time, coronal leakage under a failing restoration, or new decay reaching the canal space. That reason belongs in the narrative, because it is what the reviewer is looking for.

Premolar means eight specific teeth

The retreatment family splits on tooth position exactly the way initial therapy does, and CDT 2026 keeps both series in step:

• D3346 for anterior teeth, matching D3310.
• D3347 for premolars, matching D3320.
• D3348 for molars, matching D3330.

Position, not canal count, picks the code. An upper first premolar with two canals and two roots is D3347. A lower second premolar with a single canal is also D3347. A premolar that took molar-level chair time is still D3347.

Premolars are teeth #4, #5, #12, #13, #20, #21, #28, and #29. That range is not just anatomy trivia, it is a claim edit. PEHP’s 2026 CDT code guide states on the D3347 row that the code applies to the permanent premolars and lists those eight tooth numbers. Carrier systems compare the tooth number on the line to the tooth type the code implies, so a molar retreatment submitted as D3347, or a premolar submitted as D3348, bounces on the mismatch before anyone reads the film.

A naming trap in your PMS and in carrier policy

CDT used to call these teeth bicuspids. D3320, D3347, and D3421 all read “bicuspid” in older editions and switched to “premolar” in CDT 2018, but both words are still in circulation. Your practice management software may carry the old description, and plenty of published carrier policies still print “bicuspid” on the D3347 row, the Blue Cross & Blue Shield of Rhode Island endodontic policy among them. So when you are hunting the retreatment rule in a payer’s policy PDF and “premolar” turns up nothing, search “bicuspid” before concluding the plan never published one.

Coverage and how carriers treat retreatment

Retreatment is usually a covered benefit on plans that cover endodontics at all, and it typically pays above initial premolar therapy because the old fill has to come out first. The rules that actually decide the claim are about timing, provider, and frequency, and they vary enough that reading the specific plan is the only reliable move.

The window after the original root canal. Plans commonly refuse to pay a retreatment performed close behind the original therapy. Published examples run from 12 to 24 months:

• Blue Cross & Blue Shield of Rhode Island treats retreatment by the same dentist who did the original root canal as integral to it for up to 12 months, and a participating dentist may not bill the member for it.
• EmblemHealth denies D3346, D3347, and D3348 as inclusive of the root canal therapy when billed within 24 months of the initial treatment by the same provider, with no patient liability.
• PEHP writes the limit from the other direction, as a benefit that begins 12 months after completion of the root canal therapy.

Whether the original provider matters. Read the two shapes above carefully, because they are not the same rule. The Rhode Island and EmblemHealth policies both turn on the same dentist or same provider, which means a retreatment by a different office can be payable inside the window. PEHP’s language runs on elapsed time. Do not assume the different-dentist exception exists on a plan that never wrote one.

Frequency. Once per tooth for the lifetime of the tooth is the common cap, published that way by both Blue Cross & Blue Shield of Rhode Island and PEHP. A premolar that has already been retreated has usually spent its endodontic benefit, and the next conversation is apical surgery or extraction rather than a second redo.

What is bundled into the code. Intraoperative radiographs taken during the retreatment are part of the procedure on most plans, and the final restoration is always separate. Post removal (D2955) and treatment of an obstructed canal (D3331) are their own codes, but the AAE has cautioned members that payers see both filed routinely alongside retreatment and want documentation proving the case was genuinely difficult.

Documentation that supports the claim

Retreatment claims ask for more than initial therapy does, and the extra items are all about history:

• The date the original root canal was completed, and who completed it. This resolves the post-treatment window, and PEHP lists it as required information for D3347 submissions.
• A pre-op periapical showing the existing fill and the finding that prompted the redo: an apical radiolucency, a canal that was never treated, or a post under a leaking restoration.
• A post-op periapical showing the completed retreatment with all canals filled. On an upper first premolar, that means both canals visible when both were treated.
• A narrative of necessity explaining why the first treatment failed. PEHP asks for it in the remarks section with a summary of the pre-treatment and post-treatment radiographic findings.
• Tooth identification, the field that trips the tooth-type edit.

In the chart, record the condition of the previous root canal, what came out of the canals, whether a post or separated instrument had to be removed, how many canals were located including any missed the first time, working lengths, the refill material, and the planned final restoration.

When retreatment is not the answer

Nonsurgical retreatment is not always the route, and the alternative on a premolar has a coding wrinkle worth knowing.

1. The canal cannot be renegotiated. A blocked or heavily calcified canal that stops conventional access may be reported with D3331 when the obstruction is real and documented. Treat it as an exception, not a routine add-on.
2. The tooth needs apical surgery instead. A premolar apicoectomy is D3421 for the first root. Upper first premolars are frequently two-rooted, so a second root treated at the same surgery is D3426. That rarely comes up on anterior teeth and is easy to miss on a premolar claim.
3. The tooth is not restorable. A premolar with a vertical root fracture, insufficient ferrule, or advanced periodontal loss will not hold a new restoration. Some plans deny retreatment on restorability grounds, and a predetermination on a borderline tooth is cheaper than an appeal.

What to get right in your PMS

1. Store the prior RCT date where the biller can find it. Original treatment date and original provider decide whether D3347 pays. If the tooth was treated elsewhere, capture the date from the patient or the referring office and get it into the remarks.
2. Keep the six endodontic codes distinct in the pick list, and label D3347 with both words. D3310, D3320, and D3330 are initial therapy; D3346, D3347, and D3348 are retreatment. Carrying “bicuspid” alongside “premolar” in the local description makes the code findable whichever term the person searching learned.
3. Check the tooth number against the code before submission. Only #4, #5, #12, #13, #20, #21, #28, and #29 belong on a D3347 line.
4. Attach both films to the claim, not just to the patient chart. The clearinghouse sends what is linked to the claim.
5. Bill the retreatment on the obturation date and the buildup and crown on their own dates. D2950 and the crown on the same date as the retreatment invites same-day sequencing review at some carriers.
6. Write down how the office handles a denial inside the post-treatment window. Decide the adjustment rule once and put it in the collections notes, so the answer stops depending on who is working the account.

For how the tooth number, the prior treatment date, and the narrative land on the claim itself, see the ADA dental claim form guide.