D2391Resin-Based Composite, One Surface, Posterior

What This Code Covers

D2391 covers the placement of a single-surface resin-based composite (tooth-colored) filling on a posterior tooth, meaning a premolar or molar. The procedure includes removal of decay, etching and bonding of the tooth surface, layered placement and light-curing of composite material, and finishing and polishing. This is one of the most commonly billed posterior composite codes and is important to understand because many payers apply alternative benefit provisions that reimburse at the lower amalgam rate.

Billing Guide

Bill this code when:

• Decay involves one surface of a premolar or molar and composite resin is the material placed
• The restoration is a direct chairside composite, not a lab-fabricated inlay or onlay
• The tooth is either primary or permanent
• The provider and patient have chosen composite over amalgam for the restoration

Do not bill this code when:

• Amalgam is the material placed. Use D2140 for a single-surface amalgam on any tooth
• Two or more surfaces are involved. Use D2392 for two surfaces or D2393 for three surfaces of posterior composite
• The tooth is an anterior tooth (incisor or canine). Use D2330 for a single-surface anterior composite
• A sealant is placed rather than a filling. Use D1351 for a sealant on a tooth without caries into dentin

Insurance and Denial Prevention

Key Payer Rules:

• Many plans apply an "alternative benefit" or "least expensive alternative treatment" (LEAT) clause, reimbursing D2391 at the D2140 (amalgam) rate
• When a downgrade applies, the patient is responsible for the difference between the composite fee and the amalgam reimbursement
• Posterior composites are still classified as basic restorative, typically at 70-80% coverage after the downgrade
• Some plans have eliminated amalgam downgrades entirely, so always check the specific plan document
• Pre-authorization is not usually required but can be useful to confirm whether the plan downgrades

Common Denials and How to Respond:

• Downgraded to D2140 amalgam benefit -> This is usually a plan design issue, not a true denial. Collect the difference from the patient. If composite was medically necessary (e.g., documented metal allergy), appeal with supporting documentation
• Denied for lack of radiographic evidence of caries -> Resubmit with a clear pre-operative radiograph. Include a narrative explaining clinical findings if the decay was not visible on film but detected through other diagnostic methods
• Bundled with another procedure on the same tooth -> If a separate procedure was performed (such as a pulp cap), submit with documentation explaining that each procedure was distinct and clinically necessary
• Exceeds frequency limit for the tooth -> Provide evidence of new pathology or restoration failure since the last procedure. Include updated radiographs and clinical notes