Objective:
Tobacco is responsible for infaust oral conditions and many oral diseases. Dental caries is one of the most prevalent oral diseases. The association between tobacco smoking and dental caries has become an important recent topic of research. A systematic review and meta-analysis were conducted to evaluate the association between tobacco smoking and dental caries.

Methods:
A literature search was conducted in the databases PubMed, EMBASE, Medline and Cochrane, up to December 2018. Original observational articles that estimated relevance between tobacco smoking and dental caries in adults were included. Caries were determined by measurements of decayed, missing or filled teeth (DMFT), or decayed, missing or filled surface (DMFS), or caries-related microflora levels. Trials did not include a non-smoking group,exposure to smokeless tobacco products, or participants under 16 years old.Also, literature reviews, comments, case reports and letters to the editor were not considered. Both methods of systematic review and meta-analysis were adopted. Newcastle-Ottawa Scale (NOS) was used to assess the methodological quality of all the included studies.

Results:
Ten out of eleven of the included studies indicated a positive association between tobacco smoking and dental caries. Two meta-analyses were performed: one included five studies using DMFT as an outcome; the other included two studies of DMFS. A random effects model was used. Both were highly heterogeneous (I2=93%, chi-squared p<0.00001; I2=70%, chi-squared p=0.07, respectively) and statistically significant (mean difference, MD=1.20, 95% confidence interval, CI: 0.40–2.00, z-test p=0.003; MD=1.88, 95% CI:0.99–2.77, z-test p<0.0001, respectively). The quality scores of all varied from 7 to 9.

Conclusions:
There is a correlation between tobacco smoking and an increased risk of dental caries. However, the overall representativeness of the studies is not good. More prospective and extensive research on this topic is needed to get validation. Even so, it is imperative that people quit tobacco smoking.