Angularis nigra

{{short description|Small triangle-shaped gap which often occurs between the teeth, near the gums}}

Image:Angularis Nigra.png

File:Angularis nigra 2.png

Angularis nigra, Latin for 'black angle', also known as open gingival embrasures, and colloquially known as "black triangle", is the space or gap seen at the cervical embrasure, below the contact point of some teeth. The interdental papilla does not fully enclose the space, leading to an aperture between adjacent teeth.{{cite journal |doi=10.1016/S0889-5406(94)70013-3 |title=Incidence and size of pretreatment overlap and posttreatment gingival embrasure space between maxillary central incisors |year=1994 |last1=Burke |first1=S |last2=Burch |first2=J |last3=Tetz |first3=J |journal=American Journal of Orthodontics and Dentofacial Orthopedics |volume=105 |issue=5 |pages=506–11 |pmid=8166102}} This gap has many causes including gingival recession, and gingival withdrawal post-orthodontic work.{{cite journal |pmid=16429878 |year=2004 |last1=Ikeda |first1=T |last2=Yamaguchi |first2=M |last3=Meguro |first3=D |last4=Kasai |first4=K |title=Prediction and causes of open gingival embrasure spaces between the mandibular central incisors following orthodontic treatment |volume=20 |issue=2 |pages=87–92 |journal=Australian Orthodontic Journal}} Interdental "black triangles" were rated as the third-most-disliked aesthetic problem below caries and crown margins.{{Cite journal|last1=Cunliffe|first1=Joanne|last2=Pretty|first2=Iain|date=December 2009|title=Patients' ranking of interdental "black triangles" against other common aesthetic problems|journal=The European Journal of Prosthodontics and Restorative Dentistry|volume=17|issue=4|pages=177–181|issn=0965-7452|pmid=20158060}} Treatment of angularis nigra often requires an interdisciplinary approach, involving periodontal, orthodontic and restorative treatment.{{cn|date=January 2020}} Possible treatments to correct angularis nigra include addition of composite resin in the space,{{cite journal |pmid=19655542 |year=2008 |last1=Lenhard |first1=M |title=Closing diastemas with resin composite restorations |volume=3 |issue=3 |pages=258–68 |journal=The European Journal of Esthetic Dentistry}} veneer placement, or gum graft.{{cite journal |pmid=20213022 |year=2010 |last1=De Castro Pinto |first1=RC |last2=Colombini |first2=BL |last3=Ishikiriama |first3=SK |last4=Chambrone |first4=L |last5=Pustiglioni |first5=FE |last6=Romito |first6=GA |title=The subepithelial connective tissue pedicle graft combined with the coronally advanced flap for restoring missing papilla: A report of two cases |volume=41 |issue=3 |pages=213–20 |journal=Quintessence International}} Angularis nigra is generally only treated based on the aesthetic preference of the patient{{cite journal |pmid=19180945 |year=2008 |last1=Clark |first1=D |title=Restoratively driven papilla regeneration: Correcting the dreaded 'black triangle' |volume=125 |issue=11 |pages=1112–5 |journal=Texas Dental Journal}} (although serious gum recession may warrant periodontal treatment).

Previously, lack of proper terminology to report this condition was an issue, often colloquially termed the "black triangle"; angularis nigra has been proposed as a term to describe the appearance.

There are several risk factors leading to the development of black triangles. Papillae dimension can be changed due to any of the following reasons:

1. Inter-proximal space between teeth; diverging roots can result in the presence of an interproximal space when the contact point between the two clinical crowns is situated too incisally, diverging roots may also be a result of orthodontic treatment.{{Cite journal|last1=Cho|first1=Hae-Sung|last2=Jang|first2=Hyun-Seon|last3=Kim|first3=Dong-Kie|last4=Park|first4=Joo-Cheol|last5=Kim|first5=Heung-Joong|last6=Choi|first6=Seong-Ho|last7=Kim|first7=Chong-Kwan|last8=Kim|first8=Byung-Ock|date=October 2006|title=The Effects of Interproximal Distance Between Roots on the Existence of Interdental Papillae According to the Distance From the Contact Point to the Alveolar Crest|journal=Journal of Periodontology|volume=77|issue=10|pages=1651–1657|doi=10.1902/jop.2006.060023|pmid=17032106|issn=0022-3492}}

2. The increased distance between inter-proximal contact position to bone crest, example to that is the naturally occurring diastema.{{Cite journal|date=October 2014|title=Portuguese Abstract Translations|journal=Implant Dentistry|volume=23|issue=5|pages=e87–e93|doi=10.1097/id.0000000000000164|s2cid=220586634|issn=1056-6163}}

3. Gingiva biotype; thick and thin tissues often respond differently to inflammation and trauma,{{Cite journal|last=Houston|first=W. J. B.|date=1984-08-01|title=Textbook of clinical periodontology. Author: Jan Lindhe. Publisher: Munksgaard International Publishers Ltd., Price: D.kr. 460.00|journal=The European Journal of Orthodontics|volume=6|issue=3|pages=234|doi=10.1093/ejo/6.3.234|issn=0141-5387}}{{Cite journal|last1=SANAVI|first1=FARSHID|last2=WEISGOLD|first2=ARNOLD S.|last3=ROSE|first3=LOUIS F.|date=May 1998|title=Biologic Width and its Relation to Periodontal Biotypes|journal=Journal of Esthetic and Restorative Dentistry|volume=10|issue=3|pages=157–163|doi=10.1111/j.1708-8240.1998.tb00351.x|pmid=9759032|issn=1496-4155}} thin gingiva is more liable to recession following restoration / crown preparation / periodontal or implant surgery.

4. Patient's age; the gingiva recede with aging which can cause an open gingival embrasure.

5. Periodontal disease and loss of attachment, resulting in recession.

6. Tooth morphology and abnormal crown and restoration shape; a clinical crown that tends to be triangular in shape can also result in partial interproximal space.{{Cite journal|date=October 2014|title=Portuguese Abstract Translations|journal=Implant Dentistry|volume=23|issue=5|pages=e87–e93|doi=10.1097/id.0000000000000164|s2cid=220586634|issn=1056-6163}}