They go deeper
Periodontists are dentists who have chosen to go on further in the treatment of the gums and bone surrounding teeth.
They still clean teeth like a gp but they also will go deeper into the gums and may even fold back the gums to get to the super deep crud that has formed on the roots below the gum line. They also restore lost gum tissue thru grafting. Much more but not enuf room here. Earl.