Table 3.

Articles used for data extraction

Author(s) and Year	Study design	Topic of review	Findings
Dominy et al., 201935	Cohort study	Porphyromonas gingivalis	P. gingivalis in the brain plays a central role in the pathogenesis of AD
Ishida et al., 201759	Experimental study on mice	Porphyromonas gingivalis	Periodontitis is a risk factor for Alzheimer’s disease
Kamer et al., 202052	Systematic review	Causal relationship between periodontal disease and Alzheimer’s disease	Periodontal disease could induce systemic inflammation, blood-brain barrier disruption, neuroinflammation, brain amyloid, neurodegeneration, and cognitive impairment
Cestari et al., 201657	Case–control	Oral infections and cytokine levels in patients with Alzheimer’s disease	Increased levels of cytokines suggest their implication in the overlapping mechanisms between oral infections and Alzheimer’s
Farhad et al., 201353	Case–control	Tumor necrosis factor-α	TNF-α in patients with Alzheimer’s disease and periodontitis was approximately three-fold higher than in patients only with Alzheimer’s disease
Kamer et al., 201560	Cross-sectional	Periodontal inflammation and amyloid plaques	Periodontal inflammation is associated with amyloid accumulation in brain in areas that are prone to amyloid accumulation in patients with Alzheimer’s disease
Hategan et al., 202154	Cross-sectional	Cognitive dysfunction and periodontal inflammatory cytokines	Subjects with periodontitis had cognitive dysfunction; interleukin-1β may play a role in this process
Poole et al., 201336	Experimental study on brain tissue	Porphyromonas gingivalis	Associative hypothesis between P. gingivalis and Alzheimer’s disease
Ide et al., 201638	Cohort study	Porphyromonas gingivalis	Study suggests there is a direct relationship between P. gingivalis and cognitive decline
Hayashi et al., 201940	Experimental study on mice	Porphyromonas gingivalis	P. gingivalis worsens the prognosis in Alzheimer’s disease
Liu et al., 201741	Experimental study on mice	Porphyromonas gingivalis	Study supports the periodontal infection hypothesis of Alzheimer’s disease
Nie et al., 201942	Experimental study on mice	Porphyromonas gingivalis	Study supports periodontitis related Alzheimer’s disease initiation and pathological progression
Ding et al., 201855	Experimental study on mice	Oral infection with Porphyromonas gingivalis	Periodontal infection by P. gingivalis may cause cognitive impairments
Sochocka et al., 201756	Case–control	Pro- and anti-inflammatory cytokines	Results confirm that the presence of cognitive decline and the additional source of proinflammatory mediators, such as periodontal health problems, aggravate systemic inflammation
Leblhuber et al., 202039	Case–control	Porphyromonas gingivalis	Data support a possible association between specific periodontal pathogens and cognitive impairment
Cortexyme Inc., 202245	Randomized, double-blind, placebo-controlled clinical trial	Gingipains	Reduction of P. gingivalis in the saliva is associated with cognitive improvement
Laugisch et al., 201846	Case–control	Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, and Treponema species	Periodontal pathogens may enter the brain and stimulate a local immune response. However, [they] do not act as a trigger for developing AD
Díaz-Zúñiga et al., 201947	Case–control	Aggregatibacter actinomycetemcomitans	Aggregatibacter actinomycetemcomitans causes specific inflammatory and immune responses in brain cells
Taati Moghadam et al., 202248	Case–control	Porphyromonas gingivalis, Fusobacterium nucleatum, Prevotella intermedia, Aggregatibacter actinomycetemcomitans, and Streptococcus mutans	There was a significant relationship between increased number of pathogenic bacteria in oral microbiome and higher concentration of cytokines in patient’s blood