Those having teeth removed for fear that root infections may get to the brain may feel a bit caught between a rock and a hard place on reading this. At least dentures—and presumably bridges and other compensation for lost teeth—reduce the risk. So if one can afford to cover their bases, this news may not change much. The bigger risk could be having teeth removed and then not replacing them with something to act as a 'tooth'.Conclusions and Implications
Moderate-quality evidence suggested tooth loss was independently associated with cognitive impairment and dementia; risk of diminished cognitive function increased with incremental numbers of teeth lost. Furthermore, timely prosthodontic treatment with dentures may reduce the progression of cognitive decline related to tooth loss.
I find there are quite a few papers on this topic, but I don't plan to look into it any further.