Oue et al. reported that cognitive decline was observed in the APP transgenic mouse from which teeth had been removed, but deposition of Aβ and induction of brain inflammation were not observed.39 On the other hand, in this study, we found that APP transgenic mice that had been infected with P. gingivalis and had developed periodontal disease showed increased cerebral Aβ deposition and enhanced intracerebral inflammatory response, as well as a decrease in cognitive function. The gene discussed is APP; the disease is Mental deterioration.