periodontal disease vs disease

periodontal disease and disease both are nouns.

Word	Noun	Adjective	Verb	Adverb
periodontal disease	Yes	No	No	No
disease	Yes	No	No	No

As nouns, disease is a hypernym of periodontal disease; that is, disease is a word with a broader meaning than periodontal disease:

periodontal disease: a disease that attacks the gum and bone and around the teeth
disease: an impairment of health or a condition of abnormal functioning

periodontal disease (noun)	disease (noun)
a disease that attacks the gum and bone and around the teeth	an impairment of health or a condition of abnormal functioning