Final answer:
A stain that cannot be removed from the surfaces of the teeth is called tartar or dental calculus stain. It forms when plaque biofilms become thick and calcify over time. Various bacterial species are present in these substantial plaque biofilms.
Step-by-step explanation:
A stain that cannot be removed from the surfaces of the teeth is called a tartar or dental calculus stain. When plaque biofilms become thick and calcify over time, they turn into tartar, which is a hardened deposit on the teeth. These substantial plaque biofilms can include various bacterial species like Streptococcus and Actinomycin.