D3320 Dental Code: Premolar Root Canal Billing Guide

What D3320 covers

D3320 reports complete endodontic therapy on a permanent premolar, still called a bicuspid in many offices. That includes the first and second premolars in both arches, typically teeth #4, #5, #12, #13, #20, #21, #28, and #29. The procedure covers opening the tooth, debriding the pulp chamber and canals, shaping and cleaning, and obturating with a permanent root canal filling material. Routine intraoperative radiographs and the temporary restoration placed at the completion appointment are included.

It does not cover:

• Anterior root canal therapy. Use D3310.
• Molar root canal therapy. Use D3330.
• Retreatment of a previously root-canaled premolar. Use D3347.
• Pulpotomy or interim pulpal treatment. Use D3220 or D3221.
• Apicoectomy on a premolar. Use D3421.
• The final restoration (buildup, crown, or direct restoration). Those are billed separately.

When to bill D3320

Bill D3320 when a premolar with pulpal pathology has had root canal therapy completed, the canals are obturated with a permanent filling material, and the tooth is temporized for the final restoration. Incomplete treatment is not billable.

The billing date is the date of obturation, not the date treatment started. Multi-visit cases are billed on the completion visit.

D3320 versus D3310 and D3330

The three endodontic therapy codes are divided by tooth type:

• D3310: Anterior teeth (incisors and canines). Typically one canal.
• D3320: Premolars. Typically one to two canals.
• D3330: Molars. Typically three or more canals.

Carriers price them at different allowables: D3310 lowest, D3320 in the middle, D3330 highest, reflecting the average complexity of each tooth category. The root canal dental codes guide maps the same split across retreatment and surgery.

Top reasons D3320 gets denied

1. Missing radiographs. Virtually every carrier requires pre-op and post-op periapicals. The pre-op shows the diagnosis (periapical pathology, caries into the pulp, fracture); the post-op shows complete obturation. Missing either pends the claim. The carrier only sees images attached to the claim, not images stored at the patient level in your PMS.
2. Retreatment coded as initial therapy. The carrier sees the existing fill on the pre-op film and denies. Premolar retreatment is D3347.
3. Waiting period not yet satisfied. Many plans classify endo as a major service, and new patients with recently effective coverage often face 6-to-12-month waiting periods. The claim denies on the benefit limitation regardless of clinical necessity. Verify waiting-period status before treatment when possible so the patient knows the financial exposure up front.
4. Lifetime frequency per tooth. One root canal per tooth, lifetime. If the carrier’s records show a previous D3320 on the same tooth, even from another provider, the claim denies. A true redo is D3347, which has its own frequency rules.
5. Same-day sequencing. Billing D3320 with D2950 (core buildup) and D2740 or D2750 (crown) on the same date triggers review at some carriers, and some deny the buildup or crown unless it has a separate date of service. Bill the RCT on one date and the buildup and crown on a later one when possible.

Documentation that supports the claim

The claim needs:

• Pre-op periapical radiograph showing the tooth and the diagnostic indication.
• Post-op periapical radiograph showing complete obturation of all canals.
• Date of service (the obturation date).
• Correct tooth number.
• A narrative for unusual cases, such as post-trauma or unusual canal anatomy.

For the patient record, document:

• Diagnosis (irreversible pulpitis, pulpal necrosis, apical periodontitis).
• Pulp testing results (cold, electric, percussion, palpation).
• Number of canals located and treated.
• Working length for each canal.
• Obturation material.
• Planned final restoration (direct restoration, buildup plus crown, or crown alone).
• Patient instructions.

On an upper first premolar, which commonly has two canals, a single-canal post-op film can raise questions about completeness even though the code has no minimum canal count. A film showing both canals obturated is the strongest documentation.

Example case

A 41-year-old patient presents with spontaneous pain on tooth #5 (upper right first premolar). Cold testing produces a lingering response. The pre-op periapical shows deep distal caries approaching the pulp chamber with a small periapical radiolucency.

Treatment sequence:

1. Visit 1: access opened, single canal located and instrumented to working length, calcium hydroxide placed, temporary restoration.
2. Visit 2 (one week later): obturation completed with gutta percha, post-op periapical confirms fill to the apex, temporary restoration placed.

Billing steps:

1. Submit D3320 on the date of obturation (visit 2). Attach pre-op and post-op periapicals.
2. No special narrative is needed. The pre-op film clearly shows the caries and periapical pathology.
3. Schedule the buildup (D2950) and crown (D2750) for a later visit and bill them on their own date of service.
4. If the carrier denies for waiting period or frequency, verify the patient’s benefit effective date and prior claims history before appealing.