A carbon coated filament cord for marking the sidewall of dental prostheses. The carbon coated filament cord is made up of a strand of filaments having a core and a marking coating placed around a circumference of the core along the length of the strand of filaments. The diameter of both the core and the marking coating is sized to fit within an interproximal spacing between teeth and dental prostheses such as crowns, bridges or onlays. When pressure is applied to the strand from the tooth and adjacent prosthesis, an easily identifiable mark is left on the sidewall of the prosthesis at that position, allowing a dental professional to easily locate the area that requires further work.
