Hi @StevenS,
Thanks for sharing this article. The authors actually say this is plausible, but plausibility is not necessarily causation. Saying something is probable or reasonably does not mean it is the cause of an issue or something. Per the conclusion of their commentary they share that this mode of transmission is less likely to happen. Because in other for this to happen, there has to be blood in one person’s mouth and at the same time an opening or cut in the other person for the chance of transmission; hence the low risk. You are more likely to get it through sex and birth today than any other mode.
There have been some discussions here about this issue in the past, I hope you find this helpful:
Are people around me safe?
The fear of being transmitted by touching surface with punctured finger
Transmitting HBV through sweat?
Constant fear of transmitting the virus
Best, Bansah1.