dental orthopedics vs dentistry

dental orthopedics and dentistry both are nouns.

Word	Noun	Adjective	Verb	Adverb
dental orthopedics	Yes	No	No	No
dentistry	Yes	No	No	No

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

dental orthopedics: the branch of dentistry dealing with the prevention or correction of irregularities of the teeth
dentistry: the branch of medicine dealing with the anatomy and development and diseases of the teeth

Other hypernyms of dental orthopedics include dental medicine, odontology.

dental orthopedics (noun)	dentistry (noun)
the branch of dentistry dealing with the prevention or correction of irregularities of the teeth	the branch of medicine dealing with the anatomy and development and diseases of the teeth