The use of unverified survey data as used in this paper is problematic enough that the CDC warns against it:

https://wonder.cdc.gov/vaers.html

Also problematic is the potential confounding of E-methamphetamine, E-joint, and E-cigarette (nicotine) use. Methamphetamine is associated with severe adverse dental outcomes.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5364727/

E-joints (THC) are potentially used by patients undergoing chemotherapy / radiotherapy with known impacts on factors related to increased dental caries:

https://www.cancer.gov/about-cancer/treatment/side-effects/mouth-throat/oral-complications-pdq