cosmetic dentistry vs dentistry

cosmetic dentistry and dentistry both are nouns.

Word	Noun	Adjective	Verb	Adverb
cosmetic dentistry	Yes	No	No	No
dentistry	Yes	No	No	No

As nouns, dentistry is a hypernym of cosmetic dentistry; that is, dentistry is a word with a broader meaning than cosmetic dentistry:

cosmetic dentistry: the branch of dentistry dealing with the appearance of the teeth
dentistry: the branch of medicine dealing with the anatomy and development and diseases of the teeth

Other hypernyms of cosmetic dentistry include dental medicine, odontology.

cosmetic dentistry (noun)	dentistry (noun)
the branch of dentistry dealing with the appearance of the teeth	the branch of medicine dealing with the anatomy and development and diseases of the teeth