prosthodontics vs dentistry

prosthodontics and dentistry both are nouns.

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

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

prosthodontics: the branch of dentistry dealing with the replacement of teeth and related mouth or jaw structures by artificial devices
dentistry: the branch of medicine dealing with the anatomy and development and diseases of the teeth

Other hypernyms of prosthodontics include dental medicine, odontology.

prosthodontics (noun)	dentistry (noun)
the branch of dentistry dealing with the replacement of teeth and related mouth or jaw structures by artificial devices	the branch of medicine dealing with the anatomy and development and diseases of the teeth