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Journal of Indian Society of Pedodontics and Preventive Dentistry Official publication of Indian Society of Pedodontics and Preventive Dentistry
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Year : 2020  |  Volume : 38  |  Issue : 4  |  Page : 325-331

Effectiveness of licorice in preventing dental caries in children: A systematic review

1 Department of Pedodontics and Preventive Dentistry, Dr D.Y Patil Vidyapeeth, Pune, India
2 Department of Public Health Dentistry, Dr. D.Y. Patil Vidyapeeth, Pune, Maharashtra, India

Date of Submission25-Feb-2020
Date of Decision08-Aug-2020
Date of Acceptance01-Dec-2020
Date of Web Publication5-Jan-2021

Correspondence Address:
Dr. Ann Polachirakal Tharakan
Dr. D.Y. Patil Vidyapeeth Pune, Dr. D.Y. Patil Dental College and Hospital Pimpri Pune- 411018, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/JISPPD.JISPPD_100_20

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Background: Dental caries is one of the most prevailing oral health diseases in children. Recent times have focused on herbal products, because they have minimum or no side effects and are effective in prevention. Licorice is one such product belonging to Glycyrrhiza family used in the form of dentifrice, chewing gums, lollipop, gels, etc., Literature reports about the activity of licorice root extract on the biofilm thereby reducing Streptococcus mutans (SM) count and preventing dental caries in children. Objectives: The objective is to assess the effectiveness of licorice in reducing SM count and preventing dental caries in children. Methodology: PubMed and Google scholar were searched with search strategies for studies reporting licorice as intervention in children among 3–15 years for preventing dental caries. Only those studies with study design of randomized controlled trials, clinical trials, and comparative studies published between January 1, 2000, and October 31, 2019 were included. Cross references and hand searching for the relevant articles were also conducted. Results: A preliminary search yielded a total of 31 studies through PubMed and Google scholar. From 31 studies, nine studies were excluded based on the screening through titles. From the remaining 22 articles, six duplicates, four without parameters, six as reviews and case reports and were excluded. Finally, six articles giving ten estimates were included for qualitative synthesis. Conclusion: Licorice extracts proves to be effective as an antimicrobial agent by reducing the count of SM in children. Its action on biofilm limits the fall of pH thereby preventing acidic environment that increases the risk of dental caries. Moreover, licorice in lollipop form is well accepted by children.

Keywords: Dental caries, Glycyrrhiza glabra, licorice, Streptococcus mutans count reduction

How to cite this article:
Tharakan AP, Pawar M, Kale S. Effectiveness of licorice in preventing dental caries in children: A systematic review. J Indian Soc Pedod Prev Dent 2020;38:325-31

How to cite this URL:
Tharakan AP, Pawar M, Kale S. Effectiveness of licorice in preventing dental caries in children: A systematic review. J Indian Soc Pedod Prev Dent [serial online] 2020 [cited 2022 Nov 27];38:325-31. Available from: http://www.jisppd.com/text.asp?2020/38/4/325/306211

   Introduction Top

Dental caries is one of the most prevalent chronic diseases in humans. It is a multifactorial disease with host, agent, and environment as the major factors in its causation.[1] Caries relies upon explicit dietary propensities, and it is brought about by cariogenic microscopic organisms. The formation of acid because of sugar digestion by these microscopic organisms and the consequent reduction in ecological pH are liable for demineralization of the tooth surface and development of dental caries.[2],[3] Various factors contributing to the risk of the development of caries are consumption of dietary sugars, exposure to fluoride, decrease in the salivary flow, and oral hygiene behavior of individuals.[4] A decent decline in the dental caries has been reported in the Western developed countries over the last decade.[5] However, the stagnation in dental caries among the school going children was appreciated by the end of 1980s.[6] With change in the dietary habits among the younger generation and drift toward the refined carbohydrates, the decline may again tend to show a trend in increase of caries with time.[7] A recent meta-analysis reported that the prevalence of dental caries in India in all the WHO age and age groups was high. The mean prevalence for 5 and 12 years old was found to be 49%. The prevalence increased with increase in age and reported to be 60% in 15 years old, 78% in 35–44 years old, and 84% in 65–74 years old.[8]

Multiple acidogenic and aciduric bacteria contribute to the development of dental caries but Streptococcus mutans (SM) is the main organism and is responsible for initiating the caries process.[9] Pellicle formed over the tooth surface consists of salivary proteins such as glycoproteins, proline-rich proteins. To this pellicle, the bacterial interaction occurs and colonization of bacteria initiates. Initially, Streptococcus sangius and Actinomyces adhere which is followed by the adhesion of SM.[10] These organisms are strong acid producers and hence cause sharp decline in the pH after their interaction with the dietary carbohydrates leading to increased risk of caries.[11] The approach toward prevention of dental caries is targeted either at the whole population or at subgroups of the population.

Various preventive measures such as fluoride application, pit and fissure sealants, xylitol use through chewing gums, vaccines, fluoridated supplements, fluoridated water and milk, and fluoride varnishes are available for preventing dental caries.[12] All these are the established preventive practices which are being followed from a very long time. There is a large population which cannot undertake mechanical plaque control measures due to lack of dexterity. The recent time has been focusing a lot on the herbal products for oral health. The advantage with these products is the naturally occurring ingredients in the plants restore health with minimum or no side effects and with maximum efficiency. These herbs have been proved to be effective in various oral health problems such as bleeding gums, aphthous ulcers, halitosis, and dental caries.[13] Few herbal products such as Azadirachta indica, Ocimum sanctum, Aloe barbadensis, and licorice which have been found to inhibit dental caries.[13]

Licorice in India is known as Jeshthamadh in Marathi, Madhuka in Sanskrit, Jethimadhu in Gujarati, Atimadhurum in Tamil and Jaishbomodhu in Bengali, is a sweet herb which belongs to the genus Glycyrrhiza. The class name Glycyrrhiza is gotten from the antiquated Greek words glycos (which means sweet) and rhiza (which means root).[14] The health-related properties of licorice are due to the presence of metabolites such as saponins, aurones, benzofurans, and phenols.[14] The United States Food and Drug Administration has declared licorice as a safe drug if consumed in a small quantity. The use of the licorice as a drug should be restricted to small doses as the large doses can lead to hypertension, hyperkalemia, muscle paralysis, respiratory problems, and acute renal failure.[15] Licorice has a wide range of advantages in dentistry.[16] It has been used in treating oral candidiasis against the fungal infection, in case of gingivitis and severe periodontal disease, in recurrent aphthous ulcers as well as oral cancer. In case of root canal treatment, it is also used as an intra-canal medicament and root canal irrigant. Segal et al.[17] showed that licorice did not promote growth or induced plaque formation. The organisms in the biofilm convert the dietary carbohydrates into acid in the presence of enzyme glucosyltransferase. Licorice directly inhibits the dextran producing enzyme glucosyltransferase and thus stops the further cycle of acid production and enamel dissolution.

A study was conducted to assess the anticariogenicity of licorice against various bacteria it was found that it has the highest anti-microbial activity against SM when compared to other bacteria.[18] Thus, this systematic review was initiated to obtain an evidence-based data with an aim to investigate if licorice is effective in reducing SM count and preventing dental caries in children.

   Methodology Top

The criteria's defined for the studies to be included were all in vivo studies, randomized controlled trials and clinical studies containing licorice as a cariostatic agents in children, all forms of licorice such as dentifrice, chewing gum, gels, restorations used as an intervention, studies conducted among children 3–15 years, studies in English or studies in other languages where translation to English is possible, studies published from the year January 1, 2000 to October 31, 2019 and all clinical studies of licorice regardless of dose, frequency, duration, or method of administration. The exclusion criteria were studies where licorice is used as a remineralizing agent in caries prevention, all nonclinical studies, letters to the editor, patents, review articles, short communications, and conference proceedings. The PICO (Population, Intervention, Comparison Outcome) criteria for the review were children between 3–15 years (P), licorice in any form like dentifrice, chewing gum, gels, restorations (I) and primary prevention of new carious lesion, SM count reduction, side effects using of using licorice (O).

The search strategy was developed using keywords related to children, licorice, caries prevention, and SM count. Data were searched through the database, PubMed and Google scholar from January 1, 2000, to October 31, 2019. Hand searching of articles was done when the full texts of the relevant studies were not available through electronic database.

The primary key words used were Children, Glycyrrhiza, Effectiveness, Clinical studies. Secondary keywords were Child, Preschool, Children, licorice, Licorice, Glycyrrhiza glabra, licorice dentifrice, gel. Chewing gum, Caries reduction, Cariostatic, dental caries reduction, SM reduction, Bacterial count reduction, Clinical studies, in vivo studies, randomized controlled trial.

Search strategy

A total of seven search strategies were formed. Google search was carried out but no search strategy was used for searching articles in Google scholar. Scholar yielded 1 article which was found to be relevant according to the eligibility criteria [Table 1].
Table 1: Search strategy

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Study selection

One review author independently screened the titles and abstracts obtained by search strategy and included them if they met the inclusion criteria. Later full texts of all the included studies were obtained. After obtaining the full texts of the articles, they were screened by reading the whole article and then decided if they met the inclusion criteria. Whenever there was uncertainty regarding any study to be eligible for inclusion, the problem was resolved by discussing it with the second author finally, the search yielded 22 studies to be included in the systematic review.

Data collection process

A standardized data extraction form was prepared in Microsoft Excel with the help of an expert. Initially, 3–4 entries were made into the Excel and it was reviewed by an expert. Any disagreement between the authors was resolved by discussion. The data items included study Id, author, year of publication, purpose of the study, study design, sample size, age, duration, study setting, intervention, extract, frequency of intervention, duration of intervention, SM reduction, rebound, adverse effects, and inference [Table 2].
Table 2: Articles that met inclusion criteria

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   Results Top

This systematic review yielded a total of 28 articles [Appendix 1], through PubMed search strategy and three through Google scholar. After screening these studies for titles, nine studies were excluded. The remaining 22 studies were subjected for duplicate removal. It was observed that around 6 articles were duplicates which kept coming in different search strategies. The abstract of the remaining 16 articles was read and none of them were excluded based on abstract. These 16 articles were then read full text and a final decision was made whether to include of exclude the studies. After reading full text, 10 articles were excluded with reason: parameters required for the review were not assessed in four articles; three were review articles and three were case reports thus giving a total of six articles to be included for evidence of the licorice in children as a cariostatic agent. The characteristic of each of the included study is presented in [Table 1]. The overall findings from all the included studies reported that licorice lollipop is potential and simple effective caries-preventive agent for high-risk children.

   Discussion Top

Literature reports various studies which have been conducted throughout the world to assess the effect of licorice as a cariostatic agent in children. Although various studies are present but there was no data which gave an overall picture of licorice as a cariostatic agent. The characteristics of the articles included in this systematic review are discussed below:

Peters et al.[19] conducted a clinical study to determine the clinical effect of a simple herbal caries-prevention agent which aimed at reducing the count of SM in children. In this study, sugar-free lollipops containing licorice were given to children twice daily for 3 weeks and it was observed that the high-risk children had the steepest early decrease in Streptococcus count. At end of a follow-up period, the SM count which decreased moved the high-risk group down to moderate-risk level. The consumption of lollipop twice a day by these children significantly reduced both number and relative percentage of SM in high-risk children. An in vitro and in vivo study[20] done among children used Glycyrrhizol A as a sugar-free lollipop and reported that these sugar-free lollipops were safe and stable with respect to their antimicrobial activity. A marked reduction in cariogenic bacteria was found using these lollipops twice a day for 10 days.

When efficacy of aqueous and ethanolic extracts of licorice was assessed through a double-blind randomized controlled trial an immediate antimicrobial action of licorice extracts, with limited retentivity was observed. Both aqueous and ethanolic licorice extracts were found to be potent cariostatic agents and palatable by child patients.[21]Another study[22] gave a similar result wherein the effect of root extracts of licorice was assessed on caries-free and high-caries-risk children of 5–11 years old. Since the licorice was effective as a cariostatic agent it as suggested to use this product in high caries risk patient who have a rich carbohydrate diet and ho do not comply with dental treatments.

Oznurhan et al.[23] in their study evaluated the effectiveness of a simple herbal caries-prevention protocol for reducing salivary SM levels in children. Group were given licorice and saliva samples were collected before rinsing, at the end of 5 min and 60 min following rinsing, and the differences were calculated within 5–60 min. Licorice made a significant decrease in the streptococcus count. A study[24] displayed a strong antimicrobial activity of Glycyrrhizol A against SM among children aged 3–6 years. Salivary microbiome when analyzed showed either no change or even increase in phylogenetic diversity of the oral community following herbal lollipop usage. It suggested that the use of licorice extract-containing lollipops can be as a simple and effective way to reduce the risk of dental caries in children.[24]

In this systematic review, only six articles could fit into the eligibility criteria. The search itself did not give much literature specifically on dental caries though it focused on SM count in others. Although licorice is known since a long time, it was found this review had studies from 2010. Either studies were not reported or they may not have got eligible for this review. One study was in each of these years; 2010, 2011, 2013, and 2014 while two were reported in 2019. From the studies included, only two studies were randomized controlled trials while others were clinical trials conducted without randomization. The sample size ranged from 6 children to 66 children. Hu et al.[20] did not mention about the sample size in their study and the age ranged from 2 years to 14 years in children.

The maximum follow-up was done in the study conducted by Peters et al.[19] in 2010 which gave licorice for 9 weeks while the least follow-up was done by Hu et al.[20] for 10–11 days. There were few studies which did not do any follow-up. The intervention was provided and pre- and immediate post-intervention readings of Streptococci were taken from the saliva sample. Jain et al.[21] were the one who took saliva sample within 30 min of the study. Licorice was given to children in the form of lollipop or mouthwash which were prepared from the root extract in the included studies. Not all the studies reported about the time of licorice intake in children. The maximum time for which lollipop was in use was 10 min for 3 weeks and 10 days in Peters et al.[19] and Hu et al.[20] respectively.

No significant reduction in SM count was observed in study reported by Almaz et al.[22] in 2016 while all other studies reported a significant difference in the mutans count. Most of these studies had a very small sample size except for Peters et al.[19] Taste of licorice lollipop was not accepted by few children in Jain et al. while other studies did not report any such thing. The lollipops in one of the study were not consumed under dentist's supervision and the information was provided by the parents thus this may have altered the results obtained in this study.

Limitation of this systematic review is that only PubMed database and Google scholar were searched. Future studies large sample size, longer with follow-up period and randomized clinical trials design to assess licorice root as herbal lollipops through alternative modes of delivery are required.

   Conclusion Top

Within the limitations of this systematic review, it can be concluded that licorice extracts which are obtained from the roots of the plant, utilized in child patients demonstrates antimicrobial efficacy by leading to reduction in SM count and it also helps in lowering the acidic nature of saliva. Due to reduction in the microbial count and decreased acidic nature, it can be very well utilized as a preventive routine in pediatric practice under dentists or parent's supervision. The supervision by dentist or parents would limit the nonadherence of advised dosage and accidental over consumption by children as high doses of licorice have been linked with respiratory and renal diseases. Moreover, the candies and lollipop way of providing licorice can be well accepted by the children.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

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[PUBMED]  [Full text]  
Almaz ME, Sönmez IŞ, Ökte Z, Oba AA. Efficacy of a sugar-free herbal lollipop for reducing salivary Streptococcus mutans levels: A randomized controlled trial. Clin Oral Investig 2017;21:839-45.  Back to cited text no. 22
Öznurhan F, Buldur B, Cartı Ö, Tutar U, Celik C, Hepokur C. Antimicrobial efficacy of chlorhexidine and licorice mouthwashes in children. Meandros Medical and Dental Journal 2019;20(1):13.  Back to cited text no. 23
Chen Y, Agnello M, Dinis M, Chien KC, Wang J, Hu W, et al. Lollipop containing Glycyrrhiza uralensis extract reduces Streptococcus mutans colonization and maintains oral microbial diversity in Chinese preschool children. PLoS One 2019;14:e0221756.  Back to cited text no. 24


  [Table 1], [Table 2]


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