Introduction
Black triangles, or gingival embrasures, represent a common aesthetic and functional concern in orthodontics. Open gingival embrasures, are defined as the embrasures cervical to the interproximal contact that is not filled by the gingival tissue architecture of periodontal protection
Aetiology
1. Root Divergence and Interproximal Contact
One of the most common causes of black triangles post-orthodontic treatment is improper root angulation. According to Kurth & Kokich (2001), root divergence significantly affects the presence of papillae, particularly when the contact point is located more than 5 mm from the alveolar bone crest.
2. Periodontal Biotype and Bone Loss
A thin periodontal phenotype and bone loss, often secondary to periodontal disease or age-related changes, contribute significantly. Tarnow et al. (1992) demonstrated that when the distance from the contact point to the bone crest exceeds 5 mm, the likelihood of complete papillary fill drops to 38%.
3. Tooth Morphology
Triangular-shaped teeth, characterised by a wider incisal edge and narrow cervical area, have less contact area and are prone to papillary deficiency (Olsson & Lindhe, 1991). These teeth inherently create more open gingival embrasures even with optimal alignment.
4. Orthodontic Tooth Movement
Excessive proclination or expansion may cause marginal bone loss or soft tissue recession, predisposing to black triangle formation (Speer et al., 2018). Conversely, aggressive interproximal reduction (IPR) may also contribute by excessively reducing enamel without achieving proper contact flattening.
Classification
There is no universal classification system, but a pragmatic approach includes:
• Type I: Mild papillary deficiency; less than 2 mm of space.
• Type II: Moderate; 2–4 mm with visible black triangle.
• Type III: Severe; >4 mm with minimal or no papilla.
A useful clinical tool is the Papilla Presence Index (PPI) by Jemt (1997), which grades papillary fill between adjacent teeth or implant restorations.
Management Options
1. Orthodontic Techniques
• Root Convergence: Uprighting and root parallelism can reduce the interradicular distance at the alveolar crest, promoting papilla regeneration (Kurth & Kokich, 2001).
• Torque Adjustment: Minor changes in incisor torque, particularly in triangular teeth, can help reduce embrasure space (Zachrisson, 2001).
• Controlled IPR: Interproximal enamel reduction followed by space closure with bodily tooth movement may flatten contacts (Tuverson, 1980), but should be done conservatively.
2. Restorative Approaches
• Composite Addition: Adding to the proximal line angles can create flatter contact surfaces (Nordland & Tarnow, 1998).
• Porcelain Veneers or Crowns: Indicated for more severe or aesthetic-driven cases, especially in adults.
3. Periodontal Intervention
• Papilla Reconstruction or Fillers: Hyaluronic acid fillers have been investigated as a non-surgical option with moderate success (Becker et al., 2010).
• Surgical Reconstruction
Techniques such as the roll technique or interproximal tunnelling have shown success in severe cases (Han & Takei, 1996).
4. Laser and Biostimulation
• Low-level laser therapy (LLLT) and platelet-rich fibrin (PRF) have been explored for stimulating papilla regeneration, though evidence remains emerging (Sharma et al., 2020).
Conclusion
Black triangles are multifactorial and should be addressed through interdisciplinary planning. Early recognition of at-risk patients—those with triangular tooth forms, thin biotypes, or existing periodontal compromise—is essential. A combination of precise orthodontic mechanics, conservative IPR, and, when necessary, adjunctive periodontal or restorative procedures can significantly improve outcomes.
References:
• Tarnow DP, Magner AW, Fletcher P. (1992). The effect of the distance from the contact point to the crest of bone on the presence or absence of the interproximal dental papilla. J Periodontol; 63(12):995–996.
• Kurth JR, Kokich VG. (2001). Open gingival embrasures after orthodontic treatment in adults: Prevalence and associated factors. Am J Orthod Dentofacial Orthop; 120(2):116–123.
• Olsson M, Lindhe J. (1991). Periodontal characteristics in individuals with varying form of the upper central incisors. J Clin Periodontol; 18(1):78–82.
• Jemt T. (1997). Regeneration of the papillae adjacent to single-implant restorations. Int J Periodontics Restorative Dent; 17(4):326–333.
• Zachrisson BU. (2001). Interdental papilla reconstruction. World J Orthod; 2(1):67–73.
• Becker W, Gabitov I, Stepanov M, Kois J, Smidt A, Becker BE. (2010). Minimally invasive treatment for papillae deficiencies in the esthetic zone: a pilot study. Clin Implant Dent Relat Res; 12(1):1–8.
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