**7. Probiotic bacteria and oral hygiene**

Oral diseases like caries, gingivitis, or periodontitis are associated with a shift in bacterial biofilm composition and subsequent host reactions. Probiotics have been found to be beneficial in preventing or treating these conditions. *In vitro* studies have demonstrated that probiotic species can have potential effects on cariogenic or periodontal pathogens.

A meta-analysis of studies on the clinical effectiveness of probiotics in treating gingivitis has suggested that probiotics can significantly improve gum condition during therapy. When used regularly during orthodontic treatment, probiotics can reduce the number of bacteria from the *Streptococcus mutans* group in a patient's saliva and inhibit the expression of inflammatory mediators and an excessive immune response.

Probiotics eliminate and inhibit the growth of pathogenic microorganisms by competing for receptor sites and secreting metabolites with antibacterial activity. They also stimulate specific and non-specific immune responses by activating T lymphocytes and producing cytokines, allowing their effective use in oral diseases.

Probiotics offer several advantages over conventional antibiotics, including the ability to specifically target harmful bacteria without affecting beneficial bacteria. They restore balance to the oral microbiome and reduce the risk of oral diseases. Regular use of probiotics can be safe and effective for maintaining oral health, particularly in conditions such as gingivitis and periodontitis. However, more research is needed to determine the optimal strains, doses, and duration of probiotic use for specific oral health conditions [14, 15].

### **7.1 Caries and caries-associated microbes**

Dental caries is a complex disease that arises mostly from bacterial infection, resulting in tooth demineralization and destruction (as shown in **Figure 5**). Tooth decay is a gradual process that occurs when acidogenic bacteria in the bacteria-laden biofilm and remnants of food accumulate on the tooth surface and eventually leads to tooth damage, loss, and infection. These bacteria thrive in microbial communities that form dental plaque accumulating on the tooth surface. Among the bacterial species found in the biofilm are *Streptococcus mutans, Streptococcus sobrinus*, and *Lactobacillus,* which produce organic acids as they metabolize fermentable carbohydrates. Organic acid production leads to the undesired low pH levels in the tooth environment, causing *Adherence of* Candida albicans *on Polymethyl Methacrylate in Probiotics Solution DOI: http://dx.doi.org/10.5772/intechopen.112321*

demineralization of the tooth structure. Oral bacteria are vital etiological factors in caries development, with *S. mutans*, the primary causative microorganism discovered in a caries lesion, being the most prominent in dental caries pathogenesis.

There is evidence from multiple studies that prebiotic bacteria can inhibit caries development and probiotic supplements seem to reduce caries incidence in preschool children and schoolchildren with a high caries risk. Several studies suggest that consumption of products containing probiotic bacteria (*lactobacilli or bifidobacteria*) reduces the number of *mutans streptococci* in saliva causing reduction of dental caries [16–18].

### **7.2 Periodontal diseases**

Periodontal diseases are prevalent among adults and are divided into two stages: gingivitis and periodontitis based on the presence or absence of attachment loss. Gingivitis is characterized by the presence of gingival inflammation with no loss of connective tissue attachment (as shown in **Figure 6**). Meanwhile, periodontitis is characterized by gingival inflammation accompanied by attachment loss and the resorption of coronal portions of tooth-supporting alveolar bone (also shown in **Figure 6**). Plaque bacteria are responsible for both conditions, inducing pathological changes in the tissues, either directly or indirectly. Although conventional therapies are effective, research continues through complementary therapies to improve periodontal treatments. Recently, probiotics have gained considerable interest as a possible management option against periodontal diseases, with several clinical trials conducted to investigate their impact on oral health.

A new approach of treating gingivitis and periodontitis that has been tried during the last few years is to control a number of infectious diseases through using and consuming of probiotics, so that the disease-causing pathogens are eliminated, promoting the development of a healthy flora, thus leading to restoration of health. Probiotic bacteria, especially lactobacilli, were effective adjunct for treating periodontal disease, particularly when combined with mechanical removal of pathogenic

### **Figure 6.**

*Normal periodontium, gingivitis, periodontitis.*

biofilms. Studies indicate that adjunctive use of specific probiotic supplements leads to significant amelioration of disease indices (probing pocket depth, gingival index, plaque index, bleeding on probing, and clinical attachment level), and reduces the need for antibiotics and surgery procedures [19].

### **7.3 Halitosis**

Halitosis is a challenging chronic problem to address in the dental field. Aside from its apparent social impact, it also affects patients psychologically, leading to an increase in demand for dental treatments. Halitosis usually has an oral cause, originating from the breakdown of sulfur-containing amino acids on the tongue and in the periodontal sulcus, leading to the release of volatile sulfur compounds (VSC). Traditional methods such as scaling or root planning and chemotherapeutic solutions like chlorhexidine have shown some effectiveness, but their results are short-lived, and they have negative side effects, such as disrupting the oral cavity's homeostasis. Therefore, probiotics have emerged as a promising alternative with inhibitory effects on oral halitosis and without any of the side effects associated with the conventional treatments.

A single study suggests that the oral probiotic *Streptococcus salivarius*, which is found early in healthy individuals as a colonizer of oral surfaces and represents the primary microorganism in the tongue microbiota, has limited capacity to produce volatile sulfur compounds responsible for halitosis. On the other hand, other research advocates for the use of probiotics in managing halitosis. However, the existing evidence is not persuasive enough to support the efficacy of using probiotics for halitosis management. For more effective future studies, standardized recruitment protocols for halitosis subjects and organoleptic measurements are necessary when using probiotics as an intervention for managing halitosis [20, 21].
