[iends]

Funnily enough the paper you are citing has that quote but they cite another paper. The paper they cite says “It has been suggested that perhaps as little as 8% of dental care is justified…” and cites two more papers.

How is this acceptable in academic research? Nobody is citing the primary source and everybody is citing interpretations of some source that I can’t find the text of (probably because I’m on mobile).

tl;dr your citation is worthless through no fault of your own.