Another possibility: switching the cause and effect, e.g. maybe you received ads for fixed bridge dentures and didn't notice consciously (how many ads do we gloss over each day "not paying attention"), but later brought it up because the mind assimilates ads subliminally (arguably the whole point of advertising).
This is perhaps even more creepy than just "phones listening in", but it's not an explanation I hear very often.
This is a documented effect but I forget the exact name of it so I'm having trouble finding a scholarly article about it. But it's basically how advertising is "supposed" to work from the advertisers' perspective: they get their products/brand to the top of your mind for a given subject.
This is perhaps even more creepy than just "phones listening in", but it's not an explanation I hear very often.