Table 3.

Main studies conducted on the relationship between smoking and the oral cavity microbiota composition.

Features of the Study	Conclusions	References
82 patients, 22 non-smoking healthy controls, 28 non-smoking periodontal patients, and 32 smoking periodontal patients	Patients with periodontal disease have greater bacterial diversity, and non-smokers have a more diverse microbial community	Camelo-Castillo, A.J. et al., 2015 [12]
32 smoking and 32 non-smoking	Smoking affects the composition of the subgingival microbiota	Bašić, K. et al., 2021 [14]
316 healthy subjects	Smoking alters the composition of the microbiota of the oral cavity	Jia, Y. J. et al., 2021 [15]
558 participants divided into non-smokers, cigarette smokers, opium smokers, or both	Cigarette and opium smoking is associated with lower alpha diversity and a different composition of the oral microbiota	Wu, Z. et al., 2021 [20]
Saliva samples donated by 41 people	Evidence of a different composition of the oral microbiota between healthy patients and those with periodontal disease, which in turn diversified, whether smokers or non-smokers	Grant, M. et al., 2019 [27]
30 individuals, 10 tobacco smokers, 10 electronic cigarette users, and 10 controls.	Diverse composition in tobacco smokers, no significant differences between alpha or beta diversity, or in relative taxonomic abundances between e-cigarette users and controls	Stewart, C. J. et al., 2018 [30]