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There have been recent changes to dental CDT code D4921.

Changes to dental code D4921: Why now?

Feb. 27, 2024
Were you aware that this often misused code was amended last year? Are you using the code correctly in your practice? Find out from two coding experts.

Most dentists and dental hygienists are not aware that procedure code D4921, gingival irrigation–per quadrant, was amended for CDT 2023. Since its creation and inclusion in CDT 2014, the nomenclature (title) and descriptor have not changed. So why change now?

For a bit of history, we talked with Patti DiGangi, BSDH, RDH, (DentalCodeology founder and director emeritus of the DentalCodeology Consortium). Patti attended the ADA Code Maintenance Committee meeting in March 2013 when this procedure code was submitted by a dental service organization (DSO). Their representative presented data collected from their DSO practices that demonstrated an overwhelming number of gingival irrigation procedures being performed following scaling and root planing.

These were being submitted as D4999 (unspecified periodontal procedure, by report) since no separate procedure code existed. They suggested that having a procedure that wasn’t bundled with periodontal therapy would be beneficial for documentation and metrics. Their submission passed and the procedure code was created.

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D4921: Gingival irrigation–per quadrant

Descriptor: Irrigation of gingival pockets with medicinal agent. Not to be used to report use of mouth rinses or noninvasive chemical debridement.

At the March 2022 Code Maintenance Committee meeting, an amendment was proposed by the ADA’s Council on Dental Benefits that provided more clarification since it included the term “mouth rinses” that was not clearly defined. This new language clearly states the product used must be a prescription medicinal agent and not over the counter (OTC).

D4921: Gingival irrigation with a medicinal agent–per quadrant

Descriptor: Irrigation of gingival pockets with a prescription medicinal agent. Not to be used to report use of OTC mouth rinses or noninvasive chemical debridement.

Further clarification, as provided in Dental Coding with Confidence for CDT 2024, says noninvasive chemical debridement or drugs or medicaments dispensed in the office for home use should not be reported with D4921. This procedure should deliver a prescription medicinal agent such as chlorhexidine/Peridex into instrumented gingival pockets.1

The scientific literature does not seem to support subgingival irrigation as an effective, evidence-based procedure; however, many clinicians still provide this post-SRP for a variety of reasons, but often based on their personal experiences. A randomized controlled trial of sodium chloride 0.9%, chlorhexidine digluconate, and povidone-iodine was conducted to determine if changes occurred in the probing depths. It was determined that adjunct irrigation is not necessary.2

What’s the bottom line? If a hygienist is going to provide gingival irrigation to patients, D4921 is the appropriate CDT procedure code. Understand that with the amended descriptor, a prescription medicinal agent must be used.


1. Blair C, Grobmyer G, DiMarino J. Dental Coding with Confidence (CDT 2024 edition). eAssist Publishing; 2023.

2. Krück C, Eick S, Knöfler GU, Purschwitz RE, Jentsch HFR. Clinical and microbiologic results 12 months after scaling and root planing with different irrigation solutions in patients with moderate chronic periodontitis: a pilot randomized trial. J Periodonton. 2012;83(3):312-320. doi:10.1902/jop.2011.110044

Kathy S. Forbes, BS, RDH, has been a dental hygienist, educator, speaker, author, consultant, seminar, and study club leader for more than 40 years. She holds a license with the ADA for Current Dental Terminology, which allows her to provide the most up-to-date understanding of current procedure codes. Kathy currently serves as a director for the Dental Codeology Consortium, reviewing and developing procedure codes relevant to dental hygiene practice that are presented to the Code Maintenance Committee of the American Dental Association in March each year. 

Connie Simmons, MA, BSDH, RDH, earned her BSDH from The Ohio State University and her MA in aging studies from Wichita State University. She’s worked in clinical hygiene for almost 35 years and has other roles in clinical training, sales, speaking, and writing. Her knowledge of dental insurance and coding grew while working with an insurance carrier, and she’s now part of the Dental Codeology Consortium and an associate productivity coach with Inspired Hygiene. She’s also an expert in the clinical use of silver diamine fluoride. Reach her at [email protected].