D1110 and D1120: Dentition Rules vs Insurance Age Limits
Accurate coding for prophylaxis procedures keeps claims moving smoothly through insurance processing. Two codes that often cause confusion are D1110 (prophylaxis – adult) and D1120 (prophylaxis – child). Submitting the wrong one leads to frequent denials, delayed payments, and extra administrative work.
CDT Code Definitions
The American Dental Association defines these preventive services based on the patient's dentition:
- D1110 – prophylaxis – adult Removal of plaque, calculus, and stains from the tooth structures in the permanent and transitional dentition. This applies to patients with primarily permanent teeth.
- D1120 – prophylaxis – child Removal of plaque, calculus, and stains from the tooth structures in the primary and transitional dentition. This applies to patients who still have primary (baby) teeth or a mix of primary and permanent teeth.
The key distinction in the CDT guidelines is dentition type, not chronological age.
Why the Error Happens So Often
Many teams assume age alone determines the code. A 12-year-old with full permanent dentition might seem like a candidate for D1110, but some insurance plans enforce strict age cutoffs (often 13 or 14 years old) and automatically downcode D1110 to D1120 if the patient falls below that threshold. This results in lower reimbursement, despite the procedure matching the adult code descriptor.
The reverse occurs too. Submitting D1120 for a younger teen with complete permanent teeth gets denied when the plan expects D1110 based on dentition.
Insurance company policies frequently override ADA guidelines on this point. Age limits vary by carrier, so relying solely on CDT descriptors sets up claims for rejection.
How to Avoid the Mistake
Verify eligibility and plan details before treatment. During dental insurance verification, check the plan’s specific age cutoff for prophylaxis coverage. Note whether the plan follows dentition or uses a hard age limit.
Document the patient's current dentition clearly in the chart. Include notes on primary, transitional, or permanent status to support the submitted code if an appeal becomes necessary.
When the patient is near a common cutoff age (around 12-14 years), double-check both the clinical presentation and the plan's policy. This step prevents most denials related to D1110 and D1120.
Quick Reference Comparison
- Use D1110 for permanent or transitional dentition-dominant cases, following plan age rules.
- Use D1120 for primary or mixed dentition cases, again aligned with carrier guidelines.
Always submit the code that matches the service performed but anticipate how the payer will adjudicate based on age.
Getting this right reduces rejections and keeps dental billing efficient. Consistent verification habits and awareness of carrier-specific rules make the difference between clean claims and repeated rework. Review patient charts and plan documents regularly to stay ahead of these common pitfalls.
Note: This article reflects information as of January 2026. It is intended for informational purposes and does not replace professional advice. Always consult the latest ADA guidelines and payer requirements for the most accurate information.
