The New Generation of Stannous Fluoride

Despite modern medical advances, oral diseases, such as caries and periodontitis, continue to negatively impact public health worldwide. In fact, dental diseases affect almost 3.5 billion people around the globe.¹

Fluoride is the gold standard in caries prevention and offers myriad oral health benefits. While stannous fluoride has been long established as an anticaries agent, its inclusion into oral health products has a challenging history due to problems with its stabilization.^2,3 With advances in technology, these issues have been resolved and oral health products containing stannous fluoride can now be recommended to patients who may benefit from their anticaries and antimicrobial properties. 

In addition to caries-prevention effects, stannous fluoride is an antimicrobial agent, providing dual therapeutic benefits to patients who are at risk for both caries and periodontal diseases.^1,2,4–6 Despite its proven clinical effectiveness, early versions of stannous fluoride dentifrice failed due to poor stabilization or incompatibility with other ingredients, such as abrasives.^1–3 White³ defines stability as the “capacity of a formula to maintain (after processing and in storage) levels of available and bioavailable agent sufficient to deliver desired therapeutic action over time.” Over the past decade, scientists have been able to successfully stabilize stannous fluoride.² Currently, stannous fluoride is available as a prescription gel, over-the-counter (OTC) mouthrinse, and OTC dentifrice. This article will focus on the beneficial properties of stannous fluoride dentifrices, adding it to the array of choices for daily oral care regimens. 

History

In 1950, Fluoristan made its debut as the first stannous fluoride dentifrice (Figure 1, page 16). In 1964, Fluoristan earned the American Dental Association’s (ADA) Seal of Acceptance. However, due to poor stability, the stannous fluoride was later replaced with sodium fluoride and sodium monofluorophosphate. In the 1970s, sodium fluorides with greater anticaries effect were launched. In 1997, reformulated versions of stannous fluoride toothpaste were introduced to the market. However, a portion of the population still experienced staining from these formulations. Over the past decade, scientists have successfully stabilized stannous fluoride,^1-3,7–9 making stannous fluoride-containing toothpastes a viable option for daily oral hygiene. 

The Stabilization Process

Stannous is tin fluoride. A stannous fluoride dentifrice contains 0.454% stannous. The therapeutic efficacy of stannous fluoride depends on stabilization, which requires sustaining oxidation of the tin. When free stannous ions are oxidized, they become stannic ions and are no longer effective. In addition, stannous fluoride is water-soluble; it will dissociate in water to form fluoride ions and tin hydroxide, a process known as hydrolysis. All of these chemical changes affect the bioavailability of stannous and result in deactivation of this essential ingredient, subsequently causing stannous fluoride to lose its therapeutic value.^2,3,5 There have been a number of attempts to overcome this, including the removal of water; addition of stannous chloride (salt), which serves to replenish the stannous reservoir; addition of polyphosphates and silicas, which reduce stain; and inclusion of other chemicals, such as chelating agents. Chelation is the process used to reduce or remove heavy metals, which is implemented to prevent hydrolysis. While these formulations have been successful in stabilizing stannous fluoride, several shortcomings were present, such as poor viscosity, grittiness, increased potential for extrinsic staining, metallic taste, and a weak flavor. From a patient’s perspective, tooth staining is the most significant drawback.^2,9,10,11 

Recently, several dentifrice manufacturers have successfully stabilized stannous fluoride. The addition of zinc phosphate, zinc citrate, or vegetable glycerin, along with other ingredients, has created a stabilizing effect.^1–3 These newer formulations maintain the clinical efficacy of stannous fluoride without compromising the flavor, texture, or esthetics. 

Benefits of Stannous Fluoride

Fluorides used in dentifrices include sodium fluoride, sodium monofluorophosphate, and stannous fluoride. All of these fluorides offer anticaries benefits. In addition, stannous fluoride provides bacteriostatic and bactericidal properties, enabling it to fight plaque and gingivitis.^10,12,13 The United States Food and Drug Administration has approved stannous fluoride for antigingivitis and anticaries effects in the oral care monograph.⁴ In addition, stannous fluoride deposits a precipitate or protective mineral barrier, known as a smear layer, that is acid resistant. This smear layer obstructs the dentinal tubules, providing anti-sensitivity and anti-erosive mechanisms of action.^12,14

Plaque Reduction

Dental biofilm is an organized matrix of diverse microbes adhering to one another as well as to structures in the oral cavity. Preventing both caries and periodontal diseases depends on reducing these microbes through mechanical disruption and/​or chemical agents. Mechanical disruption of the biofilm is ideal, but complete removal during self-care is not always possible for patients. Stannous fluoride has been shown to reduce biofilm burden. The primary action is its retention on plaque.^4–6,11,15 Stannous fluoride interferes with the metabolic function of planktonic bacteria as well as aerobic and anaerobic biofilm, thereby affecting its ability to adhere to structures in the oral cavity.² 

Antimicrobial Effects

The stannous ion, specifically the solubility of tin, has a broad-spectrum effect by interfering with the metabolic function of oral bacteria and inhibiting bacterial adhesion.^2,4–6 Stannous fluoride restricts the bacterial uptake of sugars, interfering with its nutritional source. Further, stannous binds to the bacterial cells, preventing an inflammatory response. The antimicrobial properties of stannous fluoride also offer a high level of substantivity.⁵ The stannous ion remains at levels high enough to inhibit bacterial metabolic activity for up to 12 hours.¹⁶ 

Calculus Reduction

Calculus accretions form due to mineralized plaque. Calculus has a rough surface and serves as a reservoir for pathogenic bacteria, which can cause periodontal diseases. Stannous fluoride has been shown to reduce plaque/​biofilm adhesion and may support the reduction of calculus accumulation. Furthermore, some dentifrice manufacturers have incorporated additional anticalculus ingredients such as sodium hexametaphosphate, pyrophosphate, and/​or zinc. These ingredients have been shown to interfere with the crystal formation of calculus, weakening the structure of calculus.^17,18

Dentinal Hypersensitivity

Dentinal hypersensitivity is a common patient complaint and results in transient sharp pain in response to cold, hot, or tactile changes. These sensitivities arise from open dentin tubules that occur from gingival recession and/​or enamel erosion. Erosion is the loss tooth structure caused by acid exposure to the teeth for a prolonged period.¹² Treatment of dental hypersensitivity can be accomplished through in-office procedures or the use of OTC products and is addressed in two ways. The first includes sealing the dentinal tubules to reduce the dentin permeability to stimuli. Many OTC products are designed to occlude, or plug the dentinal tubules. The second option is desensitizing nerve endings to disrupt pain transmission from the nerve endings to the brain, which can be accomplished with potassium nitrate, which depolarizes the nerve endings. Stannous fluoride dentifrices may also provide relief from dentinal hypersensitivity by forming a precipitate or smear layer of an insoluble metal compound that inherently occludes the dentinal tubules.¹⁴ 

Children and adults who frequently consume highly acidic beverages, such as sports drinks, fruit juices, and soft drinks, may experience enamel erosion. Dental erosion is irreversible, making prevention key. Stannous fluoride provides a protective layer rich in calcium and phosphate, which may be able to withstand acid challenges. Research suggests that the protective layer provided by stannous fluoride produces resistance to acid erosion.¹² 

Caries Reduction

Stabilized stannous fluoride provides a 90% fluoride uptake, significantly increasing the available amount of soluble fluoride. While fluoride in general provides the greatest benefit on smooth surfaces of enamel, some research suggests stannous fluoride may also provide a reduction in root caries.^3,8 

Conclusion

Patients have many options when purchasing oral self-care products. Dentifrices containing stannous fluoride provide numerous benefits including anticaries, antimicrobial, antiplaque, and anti-hypersensitivity properties. Newer formulations of stannous fluoride toothpaste have improved taste, esthetics, and consistency, which are essential for patient compliance. 

References

1. Ciancio SG. Whole mouth healthJ J Am Dent Assoc. 2019;150(4Suppl):S1–S4.
2. Meyers CP, Pappas I, Makwana E, et al. Solving the problem with stannous fluoride: Formulation, stabilization, and antimicrobial action. J Am Dent Assoc. 2019;150 (4Suppl):s5–s13.
3. White DJ. A “return” to stannous fluoride dentifrices. J Clin Dent. 1995;6(Spec No):29–36.
4. Haraszthy VI, Raylae CC, Sreenivasan PK. Antimicrobial effects of a stannous fluoride toothpaste in distinct oral microenvironments. J Am Dent Assoc. 2019;150(4Suppl):S14–S24. 
5. Seriwatanachai D, Triratana T, Kraivaphan P, et al. Effect of stannous fluoride and zinc phosphate dentifrice on dental plaque and gingivitis: a randomized clinical trial with 6-month follow-up. J Am Dent Assoc. 2019;150(4Suppl):S25–S31.
6. Salzer S, Slot DE, Dorfer CE, Van der Weijden GA. Comparison of triclosan and stannous fluoride dentifrices on parameters of gingival inflammation and plaque scores: a systematic review and meta-analysis. Int J Dent Hyg. 2015;13:1–17. 
7. He T, Farrel S. The case for stabilized stannous fluoride dentifrice: an advanced formulation designed for patient preference. J Clin Dent. 2017;28(Spec Iss B):B1–B5.
8. Stookey GK, Mau MS, Isaacs RL, Gonzalez-Gierbolinib C, Bartizekc RD, Biesbrock AR. The relative anticaries effectiveness of three fluoride-containing dentifrices in Puerto Rico. Caries Res. 2004;38:542–550.
9. Li Y, Suprono M, Mateo LR, Zhang YP, et al. Solving the problem with stannous fluoride: Extrinsic stain. J Am Dent Assoc. 2019;150(4 Suppl): S38–S46. 
10. Hu D, Li X, Liu H, et al. Evaluation of a stabilized stannous fluoride dentifrice on dental plaque and gingivitis in a randomized controlled trial with 6-month follow-up. J Am Dent Assoc. 2019;150(4Suppl):S32–S37.
11. Biesbrock A, He T, DiGennaro J, Zou Y, Ramsey D, Garcia-Godoy F. The effects of bioavailable gluconate chelated stannous fluoride dentifrice on gingival beelng: Meta-analysis of eighteen randomized controlled trials. J Clin Periodontol. 2019;46:1205–1216. 
12. West NX, Seong J, Hellin N, Eyon H, Barker ML, He T. A clinical study to measure anti-erosion properties of a stabilized stannous fluoride dentifrice relative to a sodium fluori/​e/​triclosan dentifrice. Int J Dent Hyg. 2017;15:113–119. 
13. Baig A, He T. A novel dentifrice technology for advanced oral health protection: a review of technical and clinical data. Compend Contin Educ Dent. 2005;26(1Suppl):4–11.
14. Hines D, Xu S, Stranick M, et al. Effect of a stannous fluoride toothpaste on dentinal hypersensitivity. J Am Dent Assoc. 2019;150(4Suppl):S47–S59.
15. Gerlach RW, Sagel, PA. Initial evidence of two-step dentifrice/​gel sequence effects on health: outcomes from three randomized controlled trials. Am J Dent. 2018;31(Sp Is A):7A–12A. 
16. Ramji N, Baig A, He T, et al. Sustained antibacterial actions of a new stabilized stannous fluoride dentifrice containing sodium hexametaphosphate. Compend Contin Educ Dent. 2005;26(9 Suppl 1):19–28. 
17. He T, Anastasia MK, Zsiska M, Farmer T, Schneiderman E, Milleman JL. In vitro and in vivo evaluations of the anticalculus effect of a novel stabilized stannous fluoride dentifrice. J Clin Dent. 2017;28:B21–B26.
18. Schiff T, Saletta L, Baker RA, et al. Anticalculus efficacy and safety of a stabilized stannous fluoride dentifrice with hexametaphosphate. Compend Contin Educ Dent. 2005;26(9Suppl):29–34.

From Dimensions of Dental Hygiene. May 2021;19(5):14-16.