Black Triangles' act as a source of plaque accumulation and flossing interference, this should be treated by:
Black Triangles’ can be treated by:

Filling the entire embrasure space with pink porcelain.
Andrew's bridge system
Increasing the connector height

Loss of residual ridge contour may lead to unesthetic open gingival embrasures (“black triangles”), food impaction and percolation of saliva during speech.
Fill the entire embrasure space with pink porcelain
Andrew's bridge system can be given
Large pontics can be given
Both 1 & 2