CDT Codes Explained: A Guide to Dental Codes, Tooth Numbers and Surfaces

CDT codes, short for Current Dental Terminology codes, are the dental codes used to report procedures on dental claims, and the American Dental Association organizes them into categories by code range, from diagnostic (D0100 to D0999) through adjunctive general services (D9000 to D9999). A correct claim pairs each code with the right tooth number, surface, quadrant or arch. Because the CDT Code is licensed by the ADA, the official manual is the only reliable cheat sheet.

Offices call the same code set by several names: ADA codes, ADA dental codes, dental procedure codes, dental treatment codes or simply dental insurance codes. They all mean the CDT Code. Dental coding is the step that turns the dentist’s clinical notes into those codes. Searches for a dental billing codes cheat sheet usually turn up unofficial lists that are incomplete, outdated or copied without permission. A better approach is to understand how the code set is structured, so your team knows where to look and what each claim line needs. This guide covers the structure and the most common claim pitfalls. It does not list individual code descriptors, which you should take from the current CDT manual or your licensed software.

What are dental procedure codes by category?

Every CDT code, which is the American Dental Association code for a single dental procedure, starts with the letter D followed by four digits. The first digits place the code in a category of service. The categories and their ranges are:

Code range	Category
D0100 to D0999	Diagnostic
D1000 to D1999	Preventive
D2000 to D2999	Restorative
D3000 to D3999	Endodontics
D4000 to D4999	Periodontics
D5000 to D5899	Prosthodontics, removable
D5900 to D5999	Maxillofacial prosthetics
D6000 to D6199	Implant services
D6200 to D6999	Prosthodontics, fixed
D7000 to D7999	Oral and maxillofacial surgery
D8000 to D8999	Orthodontics
D9000 to D9999	Adjunctive general services

Within each category, codes are grouped into subcategories. For example, diagnostic codes include evaluations, imaging and tests; restorative codes are grouped by material and type of restoration. Knowing the category helps your team find the right section of the manual and recognize when a code looks out of place on a claim.

Where can you read more about the most-billed dental codes?

A handful of ADA dental codes make up most of the claims a general or specialty office sends, and each group has its own billing traps. Our code-by-code guides explain the documentation, frequency rules and claim details for each one, without reprinting ADA descriptors:

• Diagnostic: dental exam codes D0120, D0140 and D0150 and dental x-ray codes for bitewings, full-mouth series and panoramic images.
• Preventive and periodontics: D4346 vs D1110 for deciding between a routine adult cleaning and the gingivitis cleaning code, and periodontal codes D4341, D4342, D4910 and D4355.
• Restorative and fixed prosthodontics: dental crown codes, including buildups and replacement rules.
• Implant services: dental implant codes for the surgical and restorative phases.
• Oral surgery: dental extraction codes D7140 and D7210 and the records that support a surgical extraction.

Why is the CDT Code licensed?

The ADA owns the copyright to the CDT Code and maintains it through its Code Maintenance Committee. HIPAA names CDT as the standard code set for dental procedures, so payers and providers must use it, but the descriptors and nomenclature remain the ADA’s intellectual property. Practice management software vendors include the code set under license. When you see free lists online, they may be unlicensed, out of date, or missing revisions that change how a code is used.

The code set also changes every January 1. Our article on CDT 2026 code changes explains the annual cycle and what is coming in 2027.

How do CDT codes pair with tooth numbers?

Many procedures are tooth specific, and the claim must say which tooth. In the United States, dental claims generally use the Universal/National Tooth Designation System:

• Permanent teeth are numbered 1 through 32, starting with the upper right third molar and moving across the upper arch to the upper left, then down to the lower left and across to the lower right.
• Primary teeth are lettered A through T, following the same direction.
• Supernumerary teeth have their own designations, which the ADA claim form instructions describe.

A mismatch between the tooth number and the procedure is a common reason for denials. A molar-only procedure reported on an anterior tooth, or a primary tooth letter used for an adult, will often be rejected or questioned.

How are surfaces reported?

Restorations are often coded by the number of surfaces involved, so the surfaces listed must match the code. Surfaces are reported with single letters:

• M for mesial and D for distal
• O for occlusal on posterior teeth and I for incisal on anterior teeth
• B for buccal and F for facial
• L for lingual

If the claim lists three surfaces but the code describes a two-surface restoration, expect a denial or a request for clarification. Payers also compare surfaces across claims to spot repeat restorations on the same tooth within their replacement limits.

What about quadrants, arches and areas of the oral cavity?

Some procedures apply to a section of the mouth rather than a single tooth. Periodontal scaling and root planing, for example, is reported by quadrant. Dentures and some orthodontic services are reported by arch. The ADA claim form provides a field for the area of the oral cavity, which uses standard two-digit designations for the entire oral cavity, each arch and each quadrant. Common quadrant abbreviations are UR, UL, LR and LL.

When a code requires an area and it is missing, or when the same quadrant is billed twice on one date, the claim is likely to be denied.

What else does each claim line need?

• Date of service for each procedure, which matters for frequency limits.
• Diagnosis codes when the payer requires them. Dental claims often do not, but some plans and some Medicare dental claims do.
• Attachments such as radiographs, periodontal charts, photos and narratives for procedures that need them.
• Prosthesis replacement information, including whether it is an initial placement or replacement and the prior placement date.
• Orthodontic details, such as appliance placement date and months of treatment remaining.

The claim itself is submitted on the ADA Dental Claim Form or electronically as an 837D transaction. Our overview of the dental insurance billing process walks through each step.

What are the most common dental coding pitfalls?

1. Using deleted or outdated codes after the January update.
2. Mismatched tooth, surface and code, such as the wrong number of surfaces.
3. Unbundling, or reporting separately a service that the code set or plan considers part of another procedure.
4. Missing attachments for crowns, periodontal treatment, implants and surgical extractions.
5. Frequency conflicts, such as billing a service before the plan’s waiting window has passed.
6. Coding to the fee instead of the documentation. The code must reflect what was done and recorded.
7. Using a deleted or outdated code after the annual CDT update. Review code changes each year and update fee schedules and templates in your software.

How do category rules show up in daily billing?

Knowing the category of a code helps predict how a plan will treat it. Diagnostic and preventive services are often covered at a higher percentage, with frequency limits. Basic restorative, endodontic and periodontal services often fall into a middle coverage tier, and many plans place crowns, prosthodontics and implant services in a major tier with waiting periods and lower coverage percentages. Orthodontics usually has its own lifetime maximum and age limits. Plans differ, so verification should confirm how each category is covered for each patient, but the pattern explains why the same patient may owe very different amounts for two procedures on the same day.

Categories also guide attachments. Claims in the periodontics, prosthodontics, implant and oral surgery ranges are the most likely to need radiographs, charting or narratives. Building that expectation into your workflow saves a round trip with the payer.

How can an office keep coding consistent?

• Keep the current CDT manual or app available at every billing workstation.
• Update practice management software codes and fees every January.
• Create internal notes for the procedures your office performs most, written in your own words and pointing to the manual.
• Review denied claims monthly and group them by cause.
• Have clinical and billing staff agree on documentation for procedures that often need narratives.

Specialty offices have their own patterns. For example, periodontal billing relies heavily on charting and quadrant reporting, while orthodontic billing depends on treatment dates and payment schedules. Our dental billing team works inside your practice software so coding standards apply where claims are created.

Want your team’s coding habits reviewed?

If denials for tooth numbers, surfaces or missing attachments keep coming back, book a free consultation. We can review a handful of recent claims with you, point out the patterns behind them and suggest simple internal checks your team can use.