The Influence of Probiotics in Halitosis and Cariogenic Bacteria: A Systematic Review and Meta-Analysis  
[PERSON]  
1 School of Dentistry, Department of Integrated Dentistry, International University of Catalonia, Sant Cugat del Valles, 08195 Barcelona, Spain; [EMAIL_ADDRESS] (V.O. ); [EMAIL_ADDRESS] (F.R.-V.); [EMAIL_ADDRESS] (M.A. ); [EMAIL_ADDRESS] (A.R.G. ); [EMAIL_ADDRESS] (C.G.) [PERSON]  
2 Department of Human Pathology of Adults and Developmental Age, Messina University, 98100 Messina, Italy 2*  
Smokers are at an increased risk of developing periodontal disease, demonstrating a likelihood of developing periodontal disease three times higher than non-smokers [2,4]. Diabetes mellitus has been shown to cause a similar effect; inflammatory mediators are found in higher concentrations in gingival crevicular fluids and saliva in diabetics with periodontal disease compared to healthy individuals with periodontal disease [4]. Other modifiable factors that have been linked to periodontal disease are hormonal changes in females, obesity, poor oral hygiene, and stress [2, 3, 4], whereas non-modifiable factors include age [4], gender, genetics, ethnicity, and socioeconomic status [2,3]. Diagnostic measurements of periodontal disease include specific clinical indexes, such as bleeding on probing (BOP), plaque index (PII), gingival index (GI), periodontal pocket depth (PPD), clinical attachment level (CAL), gingival recession (REC), and gingival crevicular fluid (GCF) volume [3]. In addition to the clinical indexes, an evaluation of outcomes reported by the patient (bleeding gums while brushing, halitosis, tooth sensitivity, etc.) is carried out, as well as a radiographic assessment. Combining the periodontal examination, the radiographic evaluation, and the patient's medical history, a clinical diagnosis of periodontal disease can be made. According to the American Academy of Periodontology (AAP), periodontitis can be classified into four stages and three grades. Meanwhile, the four stages (I, II, III, and IV) are based on severity, complexity, and extent, and the three grades (A, B, and C) are based on the disease progression and its rate (slow, moderate, and fast) [3,5]. Periodontal treatment involves the elimination of both supra- and subginguival plaque through Scaling and Root Planning (SRP). Adjunctive to SRP, surgical procedures such as respective or regenerative surgery can be performed. In addition, antibiotics are often administered as adjunctive therapy; however, antibiotics may cause undesired side effects or may even be contraindicated in certain situations. Furthermore, bacterial resistance to antibiotics due to their excessive clinical implementation is an increasing global problem, and there is a frequent recolonization of pathogenic bacteria once antibiotic therapy is finished [6]. Hence, therapeutic alternatives are being investigated, one of them being probiotics [3]. Probiotics are non-pathogenic live organisms with potential benefits for the host if taken in adequate amounts. Common probiotics are various species of the genera _Latchocillus_ and _Bifidobacterium_, _Bacillus coagulans_, _Streptococcus thermophilus_, _Enterococcus ficeum_, and _Saccharomyces cerevisiae_[7]. They can be taken in two forms, either in fermented foods or as supplements in the form of powder, capsule, or tablet. For them to show a clinical effect, the probiotic microorganisms must be viable. The quantity of viable organisms determines the dosage of probiotic foods and supplements; clinical trials have shown that effective therapeutic results have been achieved with a daily intake ranging from 107 to 1011 live bacteria [7].