Table 2.

Included studies' characteristics and potential concerns.

Study author, date, citation	Settings, country	Sample size, age range	Outcomes	Partial recording protocol (PRP)	Minimum number of teeth or sites	Potential concerns
Alawaji et al., 2021	Untreated individuals at a university setting, Saudi Arabia	431 subjects, 13–80 years	Prevalence of CDC/AAP moderate-severe and severe periodontitis, mean (SD) of periodontitis extent, risk associations including self-reported diabetes mellitus, obesity, and current cigarette smoking	(FM)MB-DL, RHM, and (HM)MB-DL	3 teeth	Targeted untreated subjects recruited at university settings which may limit the external validity. The medical conditions were self-reported by the subjects without adding objective measurement for glycemic control, obesity was self-reported as present/absent, no minimum number of cigarette smoking were included in the current smokers' group
Teixeira et al., 2020	Convenience sample, Brazil	350 subjects, 35–74 years	Prevalence of moderate periodontitis, mean (SD) of periodontitis severity, and extent	(FM)MB-B-DL, RHM, and (HM)MB-B-DL	4 teeth	Did not describe the background characteristics of the study subjects. It was not clear where the clinical examinations were conducted
Alshihayb et al., 2020	General population (NHANES 2009–2014), USA	9575 subjects, 30–79 years	Risk associations to periodontitis prevalence including self-reported diabetes mellitus	RHM, CPITN teeth, and Ramfjord teeth	2 teeth for each used PRP	Did not define the eligibility criteria for included subjects from the NHANES data, excluded all subjects with missing data, did not report the values for the dependent variables used in the multivariate models. Defined diabetes mellitus status as present or absent without considering glycemic control
Romano et al., 2019	General population, Italy	721 subjects, 20–75 years	Prevalence of CDC/AAP moderate-severe and severe periodontitis	(FM)MB-B-DL and RHM	6 teeth	Excluded subjects with less than 6 remaining teeth
Tran et al., 2016	NHANES 2009–2010, USA	3734 subjects, 30–80 years	Mean (SD) of periodontitis extent and severity	RHM	1 tooth per selected quadrant	Excluded subjects who had no teeth in the selected quadrants for the RHM
Akinkugbe et al., 2015	General population based (ARIC study), USA	6259 subjects, 45–64 years	Risk associations were listed including current smoking (total of ≥100 cigarettes in a lifetime) and diabetes mellitus	42 RSSM, (HM)MB-B-DL, and Ramfjord teeth	2 eligible sites	Eligibility criteria were not described, excluded subjects who had 1 site with CAL rather than considering them in the no periodontitis category. Defined diabetes mellitus status as present or absent without considering glycemic control
Tran et al., 2014	General population (NHANES data 2009–2010), USA	3667 subjects, 30–80 years	Prevalence of CDC/AAP moderate-severe and severe periodontitis	(FM)MB-DB, (FM)MB-DL, RHM, (HM)MB-DL, (HM)MB-DL, CPITN teeth, and Ramfjord teeth	6 teeth	Excluded all subjects with missing data and those who had less than 6 remaining teeth
Chu and Ouyang, 2014	Convenience sample, China	200 subjects, 22–64 years	Mean (SD) of periodontitis severity and extent	(FM)MB-B-DB, (FM)MB-B-DL, (FM)MB-DB, (FM)MB-DL, RHM, (HM)MB-B-DB, (HM)MB-B-DL, (HM)MB-DB, (HM)MB-DL, Ramfjord teeth, and CPITN teeth	≥16 remaining teeth, ≥4 of them are molars, having ≥1 site with ≥5 mm PPD and CAL ≥2 mm in ≥2 sites in different quadrants	Convenience sample, selected subjects with ≥16 remaining teeth with periodontitis which limit the external validity
Relvas et al., 2013	Convenience sample, Portugal	108 subjects, 25–65 years	Mean (SD) of periodontitis severity and extent	RHM, Ramfjord teeth, and CPITN teeth	≥24 teeth, ≥5 teeth per quadrant, ≥8 teeth in CPITN, ≥4 teeth in Ramfjord	Convenience sample and strict eligibility criteria that limits the external validity of the study
Kingman et al., 2008	Population based, Brazil	1437 subjects, 14–103 years	Mean (SD) of periodontitis severity	(FM)MB-B-DB, (FM)MB-B-DL, RHM, (HM)MB-B-DB, (HM)MB-B-DL, and Ramfjord teeth	≥6 teeth per quadrant	Minimum number of included teeth may limit the external validity of the study
Vettore et al., 2007	University setting, Maternity clinic, Brazil	156 subjects, 30–67 years	Mean (SD) of periodontitis severity	RHM and CPITN	≥15 teeth	Minimum number of included teeth may limit the external validity
Beck et al., 2006	Population based (ARIC study), 4 states, USA	6793 subjects, 45–64 years	Prevalence of moderate-severe and severe periodontitis, mean (SD) of periodontitis severity	84 RSSM, 42 RSSM, 36 RSSM, RHM, (HM)MB-B-DB, and Ramfjord teeth	≥1 tooth	Older subjects (52–74 years), which may limit the external validity
Susin et al., 2005	General population, Brazil	1460 subjects, 14–103 years	Prevalence of moderate-severe and severe periodontitis	(FM)MB-B-DB, (FM)MB-B-DL, RHM, (HM)MB-B-DB, and (HM)MB-B-DL	Not clear	Defined periodontitis at least at 1 site with CAL
Dowsett et al., 2002	Untreated population, randomly selected or from siblings and spouse pairs of the randomly selected subjects, Guatemala	292 subjects, 18–78 years	Prevalence of moderate-severe and severe periodontitis	RHM and Ramfjord teeth	Not clear	Did not state what the minimum number of sites considered to define subjects with periodontitis was; there were untreated subjects, which may reduce the external validity; did not describe the selection criteria for the study population

CDC/AAP: Centers for Disease Control and Prevention and American Academy of Periodontology, CAL: clinical attachment loss, HbA1c: glycated hemoglobin, ARIC: Atherosclerosis Risk in Communities, NHANES: National Health and Nutrition Examination Survey, MB: mesiobuccal, B: midbuccal, DB: distobuccal, DL: distolingual, FM: full-mouth, HM: half-mouth, RHM: random-half-mouth, CPITN: Community Periodontal Index of Treatment Needs, 84 RSSM: 84 sites selected using random site selection method, 42 RSSM: 42 sites selected using random site selection method, and 36 RSSM: 36 sites selected using random site selection method.