Table 1.

Main characteristics of the included studies in the meta-analysis.

Included studies	Country	Study design	Case	control	OC kinds	Evaluation of PD
Komlos et al. (2021)	Hungary	Case-control	100	100	OSCC	CAL, PPD, BOP, SLPI, DMFT
Chen et al. (2021)	China	Case-control	1292	2584	Oropharyngeal cancer	SRP, History of periodontitis
Shin et al. (2019)	Korea	Case-control	146	278	OSCC	Radiographic ABL
Laprise et al. (2016)	Canada	Case-control	350	371	OC	Gingival inflammation, Gingival recession
Moraes et al. (2016)	Brazil	Case-control	35	40	OC	Chronic periodontitis, DMFT, plaque index, Gingival index, PPD, CAL
Narayan et al. (2014)	India	Case-control	242	254	OSCC	Dental caries, oral hygiene status, and periodontal disease status.
Moergel et al. (2013)	Germany	Case-control	178	123	OSCC	MBL, missing teeth
Tezal et al. (2009)	USA	Case-control	267	207	OC	ABL, missing teeth
De Rezende et al. (2008)	Brazil	Case-control	50	50	OOSCC	Dental caries, missing teeth
Tezal et al. (2007)	USA	Case-control	51	54	OOSCC	ABL, missing teeth, decayed teeth, filled teeth, crowns, root canal treatment
Chang et al. (2007)	China	Case-control	317	296	OC	Regular dental visits, missing teeth
Guha et al. (2007)	France	Case-control	2286/924	1805/928	OSCC	Oral hygiene, missing teeth, Dental check-ups
Rosenquist et al. (2005)	Sweden	Case-control	132	320	OOSCC	Missing teeth
Garrote et al. (2001)	Cuba	Case-control	200	200	OC	Dental check-ups, missing teeth
Bundgaard et al. (1995)	Denmark	Case-control	161	483	OSCC	Dental check-ups, numbers of teeth
Zheng et al. (1990)	China	Case-control	248	248	OC	Missing teeth,

OC, oral cancer; PD, periodontitis; OSCC, oral squamous cell carcinoma; ABL, alveolar bone loss; CAL, clinical attachment loss; PPD, periodontal pocket depth; BOP, bleeding on probing; SLPI, Silness-Löe plaque index; DMFT, decayed, missing and filled teeth; SRP, Periodontitis and scaling and root planning.