CDT codes — Current Dental Terminology — are the standardized codes used to report dental procedures for insurance billing and clinical documentation. As a dental assistant, you may be responsible for charting treatment, preparing claims, or helping with documentation. Understanding what CDT codes are, how they're organized, and which ones you'll encounter most often makes you a more complete member of the clinical team.
What they are: CDT codes are maintained by the American Dental Association (ADA) and updated annually. Every dental procedure has a five-character alphanumeric code beginning with the letter D. They are used universally for insurance claims, treatment records, and communication between dental offices.
How CDT codes are organized
CDT codes are grouped by category, each beginning with a specific number after the D. Understanding the categories lets you identify what type of procedure a code refers to even if you don't know the specific code.
D0000s — Diagnostic
Exams, X-rays, diagnostic casts, cancer screenings.
D1000s — Preventive
Cleanings, fluoride, sealants, space maintainers.
D2000s — Restorative
Fillings, crowns, inlays, onlays.
D3000s — Endodontics
Root canals, pulp therapy.
D4000s — Periodontics
Scaling and root planing, gum grafts, crown lengthening.
D5000s — Prosthodontics
Dentures, partials, implant-supported prosthetics.
D6000s — Implants
Implant placement, abutments, implant crowns.
D7000s — Oral Surgery
Extractions, surgical procedures, biopsies.
D8000s — Orthodontics
Braces, aligners, retainers.
The most common CDT codes assistants encounter
| Code | Procedure | Notes |
|---|---|---|
| D0120 | Periodic oral evaluation | Established patient recall exam |
| D0140 | Limited oral evaluation | Problem-focused exam — emergency or specific complaint |
| D0150 | Comprehensive oral evaluation | New patient or patient not seen in 3+ years |
| D0210 | Full mouth radiographic series | 18-image full mouth X-rays |
| D0220 | Periapical X-ray — first image | Single periapical radiograph |
| D0230 | Periapical X-ray — additional | Each additional periapical in the same visit |
| D0272 | Bitewing X-rays — two images | Standard 2-image bitewing set |
| D0274 | Bitewing X-rays — four images | Standard 4-image bitewing set |
| D1110 | Prophylaxis — adult | Adult cleaning, patient 14 and older |
| D1120 | Prophylaxis — child | Child cleaning, patient under 14 |
| D1206 | Topical fluoride varnish | Professional fluoride application |
| D1351 | Sealant — per tooth | Billed per tooth, not per arch |
| D2140 | Amalgam — one surface, primary | One-surface amalgam filling, baby tooth |
| D2160 | Amalgam — three surfaces, primary | Three-surface amalgam |
| D2391 | Composite — one surface, posterior | One-surface composite, back tooth |
| D2740 | Crown — porcelain/ceramic | Full porcelain crown — no metal |
| D2750 | Crown — porcelain fused to metal | PFM crown |
| D3310 | Root canal — anterior | Front tooth root canal |
| D3330 | Root canal — molar | Molar root canal (three or more canals) |
| D4341 | Scaling and root planing — 4+ teeth per quadrant | Deep cleaning per quadrant |
| D7140 | Extraction — erupted tooth | Simple extraction |
| D7210 | Extraction — erupted tooth, surgical | Surgical extraction requiring flap or bone removal |
| D7240 | Extraction — impacted tooth, complete bony | Fully bony impacted tooth removal |
Understanding tooth surface codes in restorative billing
Restorative codes are surface-specific — the number of surfaces involved affects which code is billed. The five surfaces of posterior teeth:
- M — Mesial (toward midline)
- O — Occlusal (biting surface)
- D — Distal (away from midline)
- B — Buccal (cheek side)
- L — Lingual (tongue side)
For anterior teeth: Mesial, Incisal, Distal, Facial, Lingual. When charting, you'll record which surfaces are involved — the dentist documents this and it determines the specific restoration code billed.
Why accurate coding matters
Incorrect coding — whether undercoding or overcoding — creates both financial and legal problems. Undercoding means the practice doesn't receive appropriate reimbursement for services provided. Overcoding means billing for services not rendered — which is insurance fraud. Your role in charting must be accurate. Document what was done, by the code that describes what was done, supported by the clinical record.
The bottom line
CDT codes are the language that connects clinical treatment to documentation and billing. You don't need to memorize every code — but knowing the category structure and the most common codes you'll encounter daily makes you a more effective clinical team member. Accurate documentation is both a professional responsibility and a legal one. When in doubt about a code, ask — never guess on a claim.