CDT is a registered trademark maintained by the American Dental Association, which publishes and updates the official code set annually. What follows is an informational, plain-language summary of the codes hygienists use most often — not the official CDT manual, and not a substitute for it. For anything billing-critical, confirm current code descriptions and requirements against the ADA's published CDT reference.
With that said, most hygiene visits only ever touch a handful of codes. Knowing them cold — and knowing what a chart note needs to say to actually support each one — saves time at the end of the day and avoids the kind of vague note that gets a claim kicked back.
Preventive and diagnostic codes
D0120 — Periodic oral evaluation
The routine recall exam for an established patient. The note needs to reflect an actual exam, not just "patient seen for cleaning" — soft tissue status, any changes since the last visit, and the dentist's findings, even briefly.
D0150 — Comprehensive oral evaluation
Used for a new patient or a patient returning after a significant gap in care. Documentation should be noticeably more thorough than a periodic eval — full charting, health history review, and a documented treatment plan or lack of findings.
D0210 — Intraoral complete series (FMX) / D0274 — Bitewings
Radiographs need a stated clinical reason and an interpretation in the note, not just "images taken." Note what was seen — or explicitly that no pathology was noted — along with the rationale for taking a full series versus bitewings alone.
D1110 — Prophylaxis, adult / D1120 — Prophylaxis, child
Removal of plaque, calculus, and stain from a periodontally healthy or gingivitis- only mouth. The note should reflect a healthy baseline — if there's active periodontitis or a history of perio therapy, D1110 is usually the wrong code, and the note should look more like a maintenance visit (see D4910 below).
D1206 — Topical fluoride varnish / D1208 — Topical fluoride, other
Document why fluoride was applied — caries risk, sensitivity, xerostomia, patient age — rather than listing it as a default add-on. A one-line rationale is enough to support medical necessity if it's ever questioned.
D1330 — Oral hygiene instructions
Vague OHI notes ("OHI given") are common but weak. Specify what was actually taught — technique demonstrated, tool recommended (interproximal brush, floss threader, water flosser), and the area it targeted. That specificity is also what makes the instruction useful to whoever sees the patient next.
Periodontal codes
D4341 — Scaling and root planing, per quadrant (4+ teeth) / D4342 — SRP, 1-3 teeth
Requires documented pocket depths supporting active periodontal disease in that quadrant, plus the areas treated and anesthesia used. A note that just says "SRP performed, quadrant 2" without depths or disease findings won't hold up if a payer requests records.
D4355 — Full mouth debridement
Used when calculus and plaque are heavy enough to prevent a proper periodontal evaluation. The note should say exactly that — that a complete exam and accurate charting weren't possible prior to debridement — since that's the clinical justification for the code, and it typically precedes a real periodontal evaluation at a follow-up visit.
D4910 — Periodontal maintenance
For patients following active perio therapy or with a periodontal history. Needs ongoing perio status in the note — pocket depths or changes since last visit, bleeding points, plaque/calculus levels — not a routine-cleaning-style note. We cover this in detail in our periodontal maintenance note guide.
The rest of the code set
This list covers what shows up in most hygiene charts on a normal day, but it's nowhere near the full CDT set — there are codes for sealants, space maintainers, periodontal surgery, and dozens of other procedures a hygienist may touch less often. For the complete categorized reference, see our full CDT code list.
Write notes that support the code, automatically
ProphyNotes listens during the visit and structures the note around what actually supports the procedure performed — findings, rationale, and all — ready before the next patient sits down.
See how it works