Dental hygiene treatment includes professionally cleaning the teeth for the patient. This is usually called scaling and polishing.
Appointments usually involve careful removal of hard deposits of calculus (tartar) that build up on the teeth and teaching how to prevent it reforming. This will go a long way in slowing the progress of gum disease.
Regular professional cleaning combined with a good cleaning regime at home is the best way to keep the teeth free of plaque and will help keep your mouth healthy.