Improving Oral Health One Tea at a Time

Second only to water, tea is the most frequently consumed drink across the globe.¹ Besides its distinctive flavor and cultural importance, tea also offers myriad health benefits, including in the oral cavity.^1,2 Due to its wide availability and affordability, the use of tea to address common oral health conditions is a promising area of research.

Deriving from the plant Camelia senensis, tea originated about 4,000 years to 6,000 years ago.^1,3 Camelia senensis produces the three most popular teas consumed today:

1. Green

2. Black

3. Oolong

Most teas contain polyphenols, caffeine, amino acids, vitamins, flavonoids, polysaccharides, and fluorine. 

Depending on how tea is prepared, different compounds are activated, producing certain medicinal properties. Green tea leaves are steamed to prevent fermentation; they contain an abundance of the health-promoting catechin, epigallocatechin-gallate (EGCg).^1–4 On the other hand, black tea leaves are fermented, causing oxidation. This process turns the leaves brown and transforms the polyphenols into the antioxidant polyphenol, theaflavin.^1,3,4 Oolong tea leaves are prepared by partial fermentation.⁵ These components of tea may offer significant benefits in the prevention and treatment of caries, periodontal diseases, oral candidiasis, and oral malodor.

Caries

Research shows that tea extracts may impede the advancement of dental caries through their anti-cariogenic effects.^2,3,5–9 It was thought that the fluoride in tea was what provided anti-cariogenic properties; however, tea’s low levels of fluoride (0.38 ppm to 0.70 ppm) demonstrate that other components are more influential.^1,2 Subramaniam et al² compared 0.2% chlorhexidine to green, black, and oolong tea extracts to determine their caries-inhibitory effects on Streptococcus mutans in vitro. Oolong tea demonstrated the greatest caries-inhibiting properties. Chlorhexidine’s bacteriostatic mechanism occurs by binding to inner bacterial cell membranes, causing an alteration that enables chemicals to enter the cell. This action is reversible. On the other hand, oolong tea irreversibly impacts bacterial cell membranes, resulting in greater inhibitory effects.² 

In another study by Ferrazzano et al,⁷ 66 patients were randomly divided into two groups: one that rinsed with green tea extract and the other with a placebo mouthrinse three times a day for a week. Those rinsing with the green tea extract experienced greater reductions in S. mutans and lactobacilli than the control. 

Xiao et al⁸ found that tea polyphenols inhibit the adhesion of S. mutans and lactobacilli to acquired pellicle in vitro. Zhang and Kashket⁹ demonstrated that swishing with black or green tea after chewing on a salted cracker—a fermentable carbohydrate implicit in caries proliferation—inhibited salivary amylase activity, with black tea providing the greatest inhibitory effect. Similarly, in a study by Hirasawa et al,¹⁰ 15 subjects rinsed with green tea extract (EGCg) before sucrose exposure. The participants experienced a reduction in acid production and balancing of the oral pH. 

Periodontal Diseases

Tea has been extensively researched for its anti-inflammatory properties and its possible role in treating periodontal diseases.¹¹ A study by Okamoto et al¹² showed EGCg from green tea inhibited Porphyromonas gingivalis with efficacy similar to that of chlorhexidine, doxycycline, and modified tetracycline derivatives. EGCg, like these other antimicrobials, interferes with P. gingivalis by inhibiting enzymatic and collagenase activities that support the progression of periodontal diseases. 

In addition, a study by Priya et al¹³ compared the efficacy of green tea mouthrinses to chlorhexidine rinse for a month. Thirty patients were divided into two groups and were instructed to either rinse with a green tea mouthrinse or a chlorhexidine mouthrinse 30 minutes after brushing. Both groups experienced decreases in plaque, gingival index, and bleeding; however, patients using the green tea mouthrinse displayed a larger decrease in bleeding. 

Lombardo-Bedran et al¹¹ investigated the extracts of black tea, theaflavins, in vitro, and found they exerted irreversible antibacterial effects on the membranes of P. gingivalis and Prevotella intermedia. This study also demonstrated that theaflavins created a synergistic reaction with adjunct periodontal treatments (metronidazole and tetracycline), and further aided in reducing pathogens, although more research is needed. 

Oral Cancer

Due to the long-term toxicity of cancer medications, new treatments with low side effects are highly coveted. The goals of chemoprevention are to inhibit the progression of premalignant cells into cancer. Tea polyphenols fit this description as they produce chemopreventive properties by inhibiting cell progression of damaged cells.

Adding tea polyphenols to saliva in vitro or to mouthrinses in vivo has shown to provide protection against the destruction caused by cigarette smoking through reductions in oxidation, inflammation, and cell growth; induction of apoptosis; and inhibition of angiogenesis in cancer cells.^5,14,15 Chang et al¹⁶ looked at the synergism of EGCg with gefitinib, an oral cancer medication. Combining green tea extracts with gefitinib resulted in further inhibition of cancer cell activities. A pilot study by Schwartz et al¹⁷ included three heavy smokers (more than 10 cigarettes a day) and three nonsmokers over 4 weeks to evaluate the effects of green tea. Five (400 mg to 500 mg) cups of green tea extract a day led to a reduction in cell growth and apoptosis of damaged cells in the heavy smokers.

In Japan, Ide et al¹⁸ and Imai et al¹⁹ both conducted large-scale cohort studies including more than 8,000 individuals investigating the relationship between green tea consumption and oral cancer incidence. Over 10 years, women who drank more than five cups of green tea a day displayed a reduced risk of cancer compared to those who consumed less than one cup in both studies.

Theaflavin has shown even more promising results against carcinogens. Babich et al²⁰ compared gingival fibroblasts and carcinoma cells of the tongue and found that theaflavin induced cell apoptosis in cancerous cells. 

Oral Candidiasis

Candida albicans is the most common fungal organism infection of the oral cavity.²³ Treatments include antifungal medication, maintaining good oral health, and rinsing or brushing after inhaled corticosteroid use. An increase in resistance to antifungal medication has forced researchers to look for more options.^6,21,22 Tea extracts have continuously shown to exhibit antimicrobial properties, including antifungal effects. 

A study by Evensen and Braun²¹ showed tea polyphenols, especially EGCg, can cause metabolic instability in C. albicans and inhibit biofilm formation in cultures. Hirasawa and Takada²² found that the antifungal properties of green tea polyphenols increased as pH levels became more acidic. Also, their study showed a synergistic reaction with the antifungal medications fluconazole and amphotericin B when taken alongside EGCg in vitro. Results showed that combining both can further reduce fungal activity. Although these results are promising, in vivo studies are needed.²²

Oral Malodor

Oral malodor is a common oral health problem that impacts diverse populations. Oral malodor originates from volatile sulfide compounds (VSCs) caused by bacterial metabolism in the mouth.^14,23 Hydrogen sulfide and methanethiol are the two main gas compounds released by VSCs, and Solobacterium moorei is the main bacterium that causes oral malodor.^14,24,25 Treatment includes brushing the tongue, scraping the tongue, or using products designed to control oral bacteria.^23,24 

Morin et al²³ investigated the abilities of green tea extracts and EGCg to reduce the growth of S. moorei. Their study found that green tea extracts and EGCg inhibit the growth and alter the cell integrity of the bacterium, causing biofilm desorption. Preventing S. moorei from adhering to oral cavity cells decreases VSC production. Additional studies by Lodhia et al²⁴ and Zeng et al²⁵ showed green tea powder and green tea extracts were successful in removing VSCs. 

Zeng et al²⁵ demonstrated that green tea extract-containing chewing gum had a therapeutic effect on oral malodor in vitro. When the pH solution increased from a neutral 7.5 to an alkaline 8.0, the green tea extract-containing chewing gum was even better at VSC removal. Five minutes of chewing the green-tea gum at a pH level of 8.1 to 8.4 achieved maximum removal of hydrogen sulfide, but further increases in the pH beyond that decreased the extract’s efficacy.

Restorative Materials

With the evidence pointing to tea extracts as effective in the prevention of many oral diseases, additional research has been conducted to examine the potential of synthesizing green tea polyphenols in oral materials. Liao et al²⁶ reviewed the research on incorporating EGCg into dental adhesives, barrier membranes, bone replacement materials, tissue regeneration materials, and antimicrobial materials. They found evidence of successful incorporation of EGCg into dental adhesive resins and glass ionomer cements. EGCg exhibited longer-lasting antibacterial properties as well as improved bond durability of resin to enamel/​dentin compared with chlorhexidine. 

Treatments to prevent tooth loss can be lengthy and expensive, and sometimes the outcomes are less than desirable. An ideal barrier membrane would prevent the migration of epithelial cells, providing space for adhesion and growth of osteoblasts, and bone tissue regeneration.²⁶ Liang et al²⁶ investigated the inclusion of EGCg into membrane materials and found it was highly compatible, and the combination supported the formation of new bone tissue. EGCg has also been combined with bone marrow mesenchymal stem cells, which resulted in enhanced bone formation and periodontal ligament regeneration.²⁶ When included with dental collagen scaffolds, EGCg showed promising results. In the role of regenerating pulp cells, EGCg promoted cell adhesion and cell proliferation, and increased surface strength of the scaffold to surrounding tissue.²⁶

While these results sound promising, more in vivo research is needed before these treatments can be used in patients. In the future, restorative materials might include embedded tea extracts to allow exceptional biocompatibility and exert therapeutic antimicrobial and anti-inflammatory properties. 

Dentifrices

The addition of tea extracts to oral healthcare products seems like a logical next step to harnessing their beneficial properties. Maruyama et al²⁷ topically applied green tea catechin-infused dentifrices to rats with induced periodontal inflammation. Compared with the control subjects, these rats experienced a reduction in inflammation.

In a study by Hrishi et al,²⁸ 30 human patients were divided into two groups: one used a fluoride-triclosan dentifrice post-scaling and root planing and the other used a green tea dentifrice post-scaling and root planing. After 4 weeks, results showed that the patients using green tea dentifrice displayed a greater reduction in gingival inflammation and improved periodontal health than the fluoride-triclosan group. As promising as these results seem, more studies are needed. The green tea-infused dentifrice used in the studies was specifically prepared for the research and is not available to consumers or professionals.

Contraindications

While preliminary research demonstrates tea’s effectiveness in promoting oral health, consuming high amounts of tea is not without risk.²⁹ Too much exposure to tea can lead to neural tube defects in infants, staining of teeth or restorative material, insomnia, anxiety, irritability, nausea, headaches, stomach upset, diuresis, heart irregularities, and tremors. Pregnant and breastfeeding women and individuals with heart conditions, stomach ulcers, kidney or liver problems, anxiety disorders, thyroid hyperfunction, and psychiatric disorders should not consume more than two cups of tea per day due to the presence of caffeine.²⁹

Conclusion

The possible beneficial effects of tea have encouraged researchers around the world to study specific components to promote better oral health. Additional human in vivo studies are needed to truly be able to recommend tea extracts to patients. As more studies are conducted, results may reveal a natural, simple, widely available, and cost effective product to aid in untreated oral health conditions worldwide. 

References

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From Dimensions of Dental Hygiene. October 2021;19(10)28,31-33.