Non-invasive Treatment of Interdental Black Triangles with Hyaluronic Acid Injection

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Black triangles appear when the papilla fails to fill the space under the contact; more invasive options such as subgingival preparation or orthodontics to close the space are not always practical or desirable. This NoteCast brings together the hyaluronic acid injection protocol, the role of defect size in success, and how complete versus incomplete reconstruction differ in stability.

Interdental black triangles have long been a major challenge in esthetic dentistry. Common approaches to closing these spaces — deep subgingival preparation, orthodontics to approximate the teeth, or changing the contact-to-crest distance — each carry their own limits and character.

As a conservative alternative, clinical studies (including a 2016 study) have examined injectable hyaluronic acid gel for reconstructing the interdental papilla. The scientific findings and clinical workflow of this method can be summarized as follows:

• Clinical injection protocol: Treatment comprises five injection sessions at three-week intervals. To prevent gel extrusion under tissue pressure, the needle enters the connective tissue at a 45° angle, 2–3 mm apical to the interdental papilla. At each visit a very small volume of gel (about 0.01 cc) is injected, and the papilla is then shaped toward the incisal.
• Importance of defect size: The key to success is the initial size of the black triangle. The highest chance of complete reconstruction is seen in small defects with an area under 0.25 mm², height under 1 mm, and width under 0.5 mm.
• Stability and non-relapse: Where the interdental papilla has been fully reconstructed (complete reconstruction), results have been highly stable, with no resorption or relapse observed at 25-month follow-up.
• Relapse risk in incomplete reconstruction: Hyaluronic acid is naturally resorbed by the body; therefore in larger defects that are not fully closed by injection (incomplete reconstruction), the chance of gel resorption and return of the black triangle is high. Increasing the number of injections in large spaces does not necessarily improve success.

Overall, precise case selection matters: hyaluronic acid injection can be an effective, successful, and fully conservative alternative to invasive prosthetic approaches only in small interdental defects.

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