D2140 Dental Code: One-Surface Amalgam Billing Guide

What D2140 covers

D2140 reports a one-surface amalgam restoration on a primary or permanent tooth. The surface can be any of the five: mesial (M), occlusal (O), distal (D), buccal (B), or lingual (L). The code includes the restoration material, the cavity preparation cleanup, the placement, the carving and finishing, and the occlusal adjustment.

The amalgam codes are set purely by surface count, for any tooth type. D2140 does not cover:

• Two-surface amalgam restorations. Use D2150.
• Three-surface amalgam restorations. Use D2160.
• Four or more surface amalgam restorations. Use D2161.
• Resin-based composite restorations. Use D2391 for one-surface posterior composites, D2330 for anterior.
• Glass ionomer or resin-modified glass ionomer restorations placed as definitive fillings. Report these under the resin-based composite series by surface count and tooth position (anterior D2330–D2335, posterior D2391–D2394). Reserve D2940 (protective/interim restoration) for interim placements, not permanent glass ionomer fillings.
• Sedative or interim restorations placed pending a definitive restoration. Use D2940.
• Pin retention. Use D2951 in addition to the amalgam code if pins were placed.

When to bill D2140

Bill D2140 when a tooth, primary or permanent and in any position, has a carious lesion or failing restoration involving exactly one surface, and that surface is restored with amalgam, carved, and the occlusion adjusted.

A two-surface preparation is D2150 even when the second surface is minor.

The composite-downgrade math

D2140 drives composite payments even at practices that no longer place amalgam. On plans with alternate-benefit downgrades for posterior composites, the carrier pays the composite at the corresponding amalgam allowable. For a one-surface posterior composite, that is the D2140 fee from the plan’s schedule.

1. The dentist places a composite, and the office bills D2391 at its composite fee.
2. The carrier applies the alternate-benefit clause.
3. The carrier pays D2391 at the D2140 allowable from the same fee schedule.
4. The patient owes the difference between the composite office fee and the amalgam allowable.

Top reasons D2140 gets denied or downgraded

1. Surface-count miscoding. D2140 billed on a two-surface preparation. The carrier reviews the chart and pays at D2150, or asks for clarification. The reverse, D2150 on a one-surface restoration, is less common because offices are more careful when the error would overbill.
2. Frequency limit on the same surface. Most plans pay one restoration per tooth surface per benefit year or per two years. The limit counts from the date of the prior covered restoration, including one placed at another office before the patient joined your practice, so check the full restorative timeline before scheduling. A narrative documenting recurrent decay, fracture, or marginal failure of the prior restoration usually clears the pend.
3. Plan no longer covers amalgam. Rare. The claim is denied as non-covered. Convert to composite if clinically appropriate and resubmit, or bill the patient per the financial agreement.
4. Wrong tooth type. Some plans apply different frequency or coverage rules to primary and permanent teeth, so a claim on a primary tooth may pay differently from the same code on a permanent tooth. The tooth number tells the carrier which it is.
5. Waiting period. Some plans, often individual plans, apply a waiting period to basic restorative services such as fillings. A D2140 placed shortly after the policy effective date can deny until that period ends, so check it at verification.

The amalgam-versus-composite decision and how it shows up in billing

The clinical decision belongs to the dentist and the patient, but the plan’s behavior shapes the conversation:

• Plans that cover composite at composite rates. Either material bills cleanly, and the patient pays the same coinsurance either way.
• Plans with alternate-benefit downgrades for posterior composites. Amalgam pays at the D2140 allowable. Composite bills at the D2391 office fee but also pays at the D2140 allowable, so the patient owes more on the composite.
• Plans that don’t cover amalgam. Composite is the only covered option, and D2140 returns a non-covered denial. Flag these plans on the plan record so the office does not quote amalgam to the patient.
• Pediatric Medicaid. Most state Medicaid programs cover both, often paying composite at composite rates without the downgrade. State-specific.

Give the patient a specific out-of-pocket estimate for the chosen material, not a generic “your insurance covers fillings.” That prevents the most common post-visit complaint.

Documentation that supports the claim

The claim needs:

• Date of service. Restorations are completed in a single appointment.
• Tooth number.
• Surface designation (a single letter: M, O, D, B, or L).
• Material code (D2140 carries amalgam implicitly).

The patient record should show:

• Clinical reason for the restoration (caries on the specified surface, fracture, failing existing restoration).
• Surface restored.
• Material placed (amalgam alloy, lot or batch if your office tracks it).
• Liner or base if placed.
• Occlusion adjusted and verified.
• Patient instructions, including post-op sensitivity expectations.

A chart note that reads only “filling on #19” does not pass audit.

Example case

A 52-year-old patient presents with a fractured restoration on tooth #30. The dentist removes the old amalgam, finds no caries underneath, and places a new one-surface amalgam on the occlusal surface. The patient prefers amalgam, and the plan covers both materials.

Billing steps:

1. Verify benefits and confirm amalgam coverage on posterior teeth.
2. Submit D2140 with surface designation O on the date of service.
3. If the prior restoration is still within the plan’s frequency window, add a brief narrative: “Replacement of fractured one-surface amalgam on #30 occlusal. No caries detected under the prior restoration. Replacement indicated for marginal integrity.”
4. The carrier processes per the plan’s amalgam coverage and frequency rules.

Had the patient been on a plan with composite-only coverage, the dentist would have offered composite, the office would have submitted D2391, and the patient would have paid composite coinsurance.