TABLE II -.
List of studies suggesting the potential use of licorice in periodontal therapy
| Authors | Study design | Findings |
|---|---|---|
| Sharma et al 2022 (33) | Randomized controlled trial | Both licorice and chlorhexidine mouthwash inhibited the accumulation of plaque and inflammation of the gingiva. The herbal mouthwash was shown to be effective as a self-care treatment since chemical formulations are associated with adverse effects with long-term usage. |
| Madan et al 2019 (34) | Randomized clinical trial | Bleeding of the gingiva, probing pocket depth, and attachment loss were significantly decreased in patients using Glycyrrhiza glabra gum paint in 10% concentration. It can be used for longer periods to prevent and treat periodontal disease as they do not have any side effects, and thus, it is also effective as an alternative for synthetic agents. |
| Takamori et al 2018 (35) | Animal study | Loss of attachment, immune complex formation, and inflammatory cell infiltration were greater in the lipopolysaccharide (LPS) group than in the control, and were completely reduced in the glycyrrhetinic acid (GA) groups. Increased alveolar bone destruction was seen in the LPS group than in the GA or control groups. Hence, in the experimentally induced periodontitis model in rats, GA had the ability to reduce periodontal destruction. |
| Suwannakul and Chaibenjawong 2017 (26) | In vitro study | Licorice extract showed antimicrobial effects against Porphyromonas gingivalis with MBC and MIC of 25 and 62.5 μg/mL respectively. It also reduced the quantity of biofilm and the activities of Arg- and Kgp-proteases. |
| Salehi et al 2017 (36) | Double-blind clinical trial | Mucoadhesive tablets containing licorice extract can relieve pain, decrease the diameter of the ulcer and the inflammation around it, and improve the recovery in aphthous stomatitis. |
| Jain et al 2017 (37) | Randomized clinical trial | Licorice mouthwash reduced the accumulation of plaque and inflammation of gingiva, without any tooth discoloration or unpleasant taste sensation. |
| Shivprasad et al 2017 (38) | Randomized controlled trial | Subgingivally delivered licorice as an adjunctive treatment modality to scaling and root planing showed clinical and microbiological benefits in periodontal therapy, with a reduction in the prevalence of P. gingivalis. |
| Ali and Mohammed 2016 (39) | Comparative human study | Licorice extract based mouthwash inhibits plaque formation and inflammation of gingiva without any adverse effects. Therefore, it can be used as an adjunctive to scaling and root planing in periodontal treatment. |
| Hamdon et al 2014 (40) | Human study | Licorice extract showed antibacterial effects against Aggregatibacter actinomycetemcomitans, based on antimicrobial sensitivity tests. The antibacterial effect was greater against planktonic cells as compared to the cells within the biofilm. It produced an inhibition zone similar to tetracyclines with a concentration of 250 μg. |
| Kim et al 2013 (41) | Invitro study | 18α-GA is effective in the treatment of vascular diseases caused by P. gingivalis. It reduces vascular permeability induced by LPS by inhibiting IL-8 production from the endothelium. |
| Farhad et al 2013 (42) | Experimental human study | A significant reduction of MMP-8 concentration was seen in both licorice and doxycycline groups than in the placebo group. The licorice group showed better reduction of MMP-8 concentration than doxycycline group, which was not statistically significant. Hence, licorice extract can be as potent as antibiotics such as doxycycline to treat periodontal diseases by preventing the MMP production by host cells. |
| Kim et al 2012 (43) | In vitro study | Glabridin inhibits activation of signaling molecules induced by RANKL and other transcription factors of osteoclast precursors, and so it can be used to inhibit osteoclastogenesis. |
| Zhu et al 2012 (44) | Animal study | Isoliquiritigenin (ISL) inhibits osteoclastogenesis induced by RANKL and bone loss by various signaling pathways. Hence, it has the potential to be used as a therapeutic or preventive agent for the treatment of lytic bone diseases. |
| Feldman et al 2012 (45) | In vitro study | Licochalcone A inhibits the two primary causative factors of periodontitis, i.e., formation of biofilm with P. gingivalis and the immune response of the host. |
| La et al 2011 (46) | In vitro study | Licoricidin (LC) and licorisoflavan A (LIA) inhibited the production of IL-6, MMP-7, -8, and -9 in macrophages. They can be used to treat MMP and cytokine-mediated conditions such as periodontal disease, and are potent host-modulating agents. |
| Bodet et al 2008 (32) | In vitro study | Licorice extract showed anti-inflammatory effects by reducing the IL-1b, -6, -8 and TNF-α responses of macrophages induced by LPS. It is a potential therapeutic agent to prevent or treat the tissue destruction caused due to periodontal disease. |
| Wittschier et al 2006 (47) | In vitro study | The polysaccharides in G. glabra inhibit bacterial adhesion and thus can be potential therapeutic agents against bacterial infection. |
| He et al 2006 (27) | In vitro study | Glycyrrhizol B and gancaonin G showed moderate antibacterial effect against Streptococcus mutans, while Glycyrrhizol A showed strong antibacterial effect with MIC of 1 μg/mL. Hence, the roots of Glycyrrhiza uralensis contain isoflavones which exhibit antibacterial effects. |
| Choi 2005 (48) | Animal study | Glabridin, an estrogenic plant product, stimulates the in vitro formation of bone in cultured osteoblasts. Thus, glabridin can be a potent agent in the management of osteoporosis. |
| Salari et al 2003 (49) | Human study | Enoxolone with the mentioned concentrations is effective against isolated periodontopathogenic and capnophilic bacteria. Its MICs were 8 µg/mL for A. actinomycetemcomitans and Capnocytophaga species, and 16 µg/mL for Eikenella corrodens. The MBC was also 16 µg/mL for all the microorganisms. |
| Salari and Kadkhoda 2003 (28) | In vitro study | GA at an appropriate concentration has good efficacy against isolated periodontopathogenic and capnophilic bacteria. The MICs of GA were 8, 16, and 8 mg/L for A. actinomycetemcomitans, Eikenella corrodens and Capnocytophaga, respectively, and the MBC was 16 mg/L for all species. |
| Saeedi et al 2003 (50) | Randomized, controlled trial | Edema, erythema, and itching were more effectively reduced with 2% licorice topical gel than with 1% gel in 2 weeks. |
IL = interleukin; MBC = minimum inhibitory concentration; MIC = minimum bactericidal concentration; MMP = matrix metalloproteinase; TNF = tumor necrosis factor.