The curse of the black triangle

For any orthodontic providers, the curse of the black triangle cannot be ignored. Gingival Black Triangles (GBTs) are surprisingly common in association with orthodontic treatment and potentially present a significant problem if not managed appropriately. A recent systematic review carried out by Rashid et al in 20221 found that the incidence of GBTs following orthodontic treatment ranged from 38% to 58%. Research has also been carried out to investigate patients’ perceptions of GBTs and to ascertain how patients rank “black triangles” against other aesthetic problems2. GBTs ranked as the third on the list of least aesthetic traits and were considered less aesthetic than crowding. Only anterior caries and unsightly crown margins ranked as worse. With the high incidence and high aesthetic concerns about GBTs, as orthodontic providers we need to be mindful that by treating a patient, we don’t inadvertently leave them with greater aesthetic problems.

The classic paper by Tarnow et al in 19923 identified that the key factor in the development of a papilla and thus absence of a GBT was the distance between the inter-proximal contact point and the interproximal alveolar bone level. At a distance of 5mm of less, the papilla was present in 98% cases. This dropped to 56% at 6mm and 27% at 7mm, in effect dropping by 50% for each mm increase. A separate study identified that if the distance between the roots was greater than 3mm, a lower level of interproximal bone occurred.

Other risk factors have also been identified by research which include an increased risk with age, tooth morphology (i.e. higher risk with triangular teeth) and pre-existing bone levels/ previous periodontal issues. Other studies suggest that risk increases with greater levels of crowding and that by aligning anterior teeth, there is a slight drop in the interproximal bone level as the roots move apart.

Fortunately, there are a number of strategies we can employ as part of our orthodontic treatment to reduce the risk of GBT’s and manage patients’ expectations. Firstly, it is important to ensure that anterior teeth are properly uprighted with good root parallelism.  Teeth that are tipped are likely to result in a higher contact point, greater distance between the roots and thus greater chance of a black triangle.

Secondly, careful and considered interproximal reduction (IPR) can lower the contact point and reduce the distance from the contact point to the interproximal bone to a figure at or below that magic 5mm target, thus ensuring an aesthetic papilla.  

Finally, in some cases, particularly due to morphology of the teeth, IPR alone will not suffice. In such cases (figures 1-3), interproximal bonding using a technique such as bioclear bonding, the tooth form can be improved and the contact point can be lowered avoiding an unsightly black triangle

How to avoid the curse of the black triangle:

1) Given the high incidence of GBTs and the aesthetic concerns they present, a discussion about them should form part of the informed consent process, particularly in high-risk patients such as adults.

2) Be aware of the risk factors such as age and tooth morphology and the magic target figure of no more than 5mm from contact point to alveolar bone level.

3) Ensure that anterior teeth are properly uprighted and plan IPR to help lower the contact point. Interproximal composite bonding may help in more severe cases.

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References 

1)    “Incidence of gingival black triangles followingtreatment with fixed orthodontic appliance: A systematic review” Rashid etal, Healthcare 2022, 10, 1373

2)    “Patients’ ranking of “black triangles” againstother common aesthetic problems” Joanne Cunliffe and Iain Pretty, The EuropeanJournal of prosthodontics and restorative dentistry, 12/2009, 17(4), 177-181

3)    “The effect of the distance fromthe contact point to the crest of bone on the presence or absence of theinterproximal dental papilla” Tarnow DP et al, J Periodontology,1992;63:995-6,