Table 3.

Summary of cross-sectional studies in other countries.

Ref. No.	Study Country Year Sample Size	Parameters for Evaluated for the Diagnosis of COPD	Parameters for Evaluated for the Diagnosis of Periodontitis	Main Findings
[46]	Russel et al. USA 1999 n = 58	Clinical diagnosis	Dental plaque	Pulmonary pathogens formed from oral plaque were associated with COPD morbidity.
[47]	Baldomero et al. USA 2019 n = 136	SGRQ	PD, BOP, CAL, PI, GI	Periodontitis index was not associated with COPD exacerbations.
[48]	Leuckfeld et al. Norway 2008 n = 180	Clinical diagnosis	Marginal bone level	Chronic periodontitis defined as mean marginal bone level ≥ 4 mm was significantly associated with severe COPD.
[49]	Chrysanthakopoulos et al. Greece 2016 n = 3360	Self-administered questionnaire	PPD, CAL	Clinical attachment loss was significantly associated with COPD.
[50]	Winning et al. Northern Ireland 2019 n = 1380	Spirometry	PPD, CAL	Chronic periodontitis was significantly associated with decreased respiratory function, after adjusting for other confounders.
[51]	Ledić et al. Croatia 2013 n = 136	Spirometry	PI, PBI, RE, PPD, CAL	An association with severity of periodontitis and COPD. (OR 3.2, 95% CI 1.0–9.8)
[52]	MLopez-de-Andrés et al. Spain 2018 n = 51142	Self-reported questionnaire		The prevalence of periodontitis in COPD patients was higher compared to that without COPD subjects.
[53]	Bergström et al. Sweden 2013 n = 80	Spirometry, Pulmonary X - ray, computed Tomography, and SGRQ	Remaining teeth, PPD, BOP, RE, Dental plaque	Periodontitis is strongly associated with smoking, but not with the development of COPD in smokers.
[54]	Henke et al. Germany 2016 n = 206	Spirometry	PPD, Alveolar bone loss	No association was observed between periodontitis and pulmonary function, and periodontitis was associated with age and smoking habits.