PRP Injection Technique for Gingival Black Triangles
Critical Clarification: No Evidence for Gingival PRP in Black Triangles
The provided evidence does not support the use of PRP injections for treating gingival black triangles (interdental papilla loss). The available guideline evidence exclusively addresses PRP use for periorbital/facial rejuvenation, not dental/gingival applications 1.
Evidence-Based Treatment for Black Triangles
First-Line Approach: Hyaluronic Acid Injection
For interdental papilla reconstruction to reduce black triangles, hyaluronic acid (HA) should be injected directly into the base of the deficient papilla, 2-3 mm apically from the tip of the papilla, using approximately 0.2 mL per site 2, 3.
Injection Protocol
- Injection site: Directly into the base of the papilla, 2-3 mm apical to the papillary tip 3
- Volume: Less than 0.2 mL per deficient papilla site 2, 3
- Technique: Following local anesthesia, inject into the papillary base in an apical direction 2, 3
- Frequency: Three injections total - initial injection, then repeat at 21 days (3 weeks), and again at 42 days (6 weeks) 4, 2
Expected Outcomes
- Peak improvement: Maximum black triangle reduction occurs at 3 months post-injection (39% reduction in height, 0.83 mm mean reduction) 5
- Sustained results: At 6 months, improvement decreases slightly to 29% reduction (0.62 mm mean reduction) 5
- Success rates: Statistically significant reduction in both height and surface area of black triangles compared to saline placebo 4
- Patient satisfaction: Significantly higher satisfaction scores with HA compared to placebo, though two-thirds would repeat the procedure despite discomfort 4, 2
Alternative Modality: Photobiomodulation (Limited Evidence)
- Hemolasertherapy protocol: 635 nm wavelength diode laser applied at four points (coronal third, apical third, mesial, and distal to papilla), followed by provoked bleeding in the sulcus, then repeat laser application 6
- Effectiveness: Only minor increase in papilla height with limited black triangle closure 6
- Evidence quality: Single case report with modest results; not recommended as primary treatment 6
Common Pitfalls to Avoid
- Overfilling: Exceeding 0.2 mL per site may cause tissue distortion without additional benefit 2, 3
- Inadequate follow-up: Improvement peaks at 3 months but partially regresses by 6 months, requiring patient counseling about realistic expectations 5
- Wrong injection depth: Superficial injection into papillary tip rather than base reduces effectiveness 3
- Single treatment expectation: Three injections over 6 weeks are required for optimal results, not a single session 4, 2
Important Caveat
PRP is not the evidence-based treatment for gingival black triangles. All high-quality research for interdental papilla reconstruction uses hyaluronic acid, not PRP 4, 2, 5, 3. The confusion may arise from PRP's use in periorbital "black triangles" (tear trough deformities), where PRP is injected intradermally into the periorbital area 1, but this is an entirely different anatomical region and clinical indication.