## 5 Topical Curcumin-Based Formulations in Oral Diseases
### Periodontal Disease  
According to World Health Organization (WHO) data, periodontal disease affects about 10% of global population [12], and according to the Centers of Disease Control and Prevention (CDC), 47.2% of United States population aged 30 years and older experience some health problems related to periodontal disease [113]. The problem intensifies with age and occurs more frequently in men than women. Its higher prevalence is also correlated with poorer socioeconomic status, smoking and comorbidities including diabetes [114, 115]. Periodontal disease affects gums which are swollen and bleed and can finally lose their supportive function towards teeth. This, in turn, is related to the increased risk of teeth falling out if the condition remains untreated. In most cases, the mechanisms underlying periodontal disease are related to the inflammatory processes caused by bacteria deposited in dental plaque. According to the classification proposed by the American Academy of Periodontology, periodontal disease comprises several different conditions, including gingival diseases, chronic periodontitis, aggressive periodontitis, periodontitis occurring as a manifestation of systemic diseases, necrotizing periodontal diseases, abscess of periodontitis, periodontitis associated with endodontic lesions and other developmental or acquired deformities and conditions [116]. The general therapy of periodontal disease should focus on the mechanical removal of dental plaque and can also comprise antimicrobial therapy, involving both systemically and locally acting preparations. It was shown that the application of topical antiseptic formulations can be more effective, due to the possibility to obtain significantly higher drug concentration in periodontal pockets. Moreover, in the products administered locally, the substances displaying broad antimicrobial spectrum can be included with significantly lower risk of drug resistance-related problems compared to the drugs acting systemically. Finally, the topical administration minimizes the risk of systemic side effects [117]. In the treatment of periodontal disease-related symptoms, curcumin can be considered useful due to its antibacterial, antioxidant and anti-inflammatory properties. It is important to notice that the experimental studies showed that curcumin had the ability to suppress the growth of bacterial strains associated with the occurrence of periodontal disease, particularly _Porphyomonas gingivalis_[118, 119]. The available literature studies presented in this paragraph usually focus on the application of curcumin as an adjuvant to standard procedures employed in periodontal problems. For example, [PERSON] et al. [117] compared curcumin-loaded collagen sponges and Periocol CG chips containing chlorheximide as adjuvant therapies to scaling and root planning which are the removal of the dental plaque above and below gums. For both compared systems, the clinical parameters, including plaque index (the thickness of dental plaque in supragingival region), gingival index showing the inflammation degree and clinical attachment level (CAL) were compared. In the study performed with volunteers suffering from chronic periodontal disease, it was shown that curcumin-loaded formulation administered locally resulted with reduced inflammation. As the most probable mechanism of this phenomenon, reduced expression of genes responsible for pro-inflammatory cytokines action was mentioned. The other possible pathway leading to anti-inflammatory results was the reduced activity of nuclear factor-kB (NF-kB). Similar results were observed for both compared formulations which suggested that curcumin can be effectively applied in the treatment of periodontal disease. However, after three months of study, the activity of curcumin-based formulation decreased compared to the chlorheximide-based product. The observed effect could be related to the shorter biological half-life of curcumin or insufficient concentration. [PERSON] et al.