dental chair vs chair

dental chair and chair both are nouns.

Word	Noun	Adjective	Verb	Adverb
dental chair	Yes	No	No	No
chair	Yes	No	Yes	No

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

dental chair (noun)	chair (noun)
A chair designed for patients in the dentist office.	the position of professor
	a seat for one person, with a support for the back
	an instrument of execution by electrocution; resembles an ordinary seat for one person
	a particular seat in an orchestra
	the officer who presides at the meetings of an organization

dental chair (verb)	chair (verb)
	preside over
	act or preside as chair, as of an academic department in a university