Stannous Fluoride Deposition Into Plaque Biofilm: Effects of Formulation Chemistry and Hops β-Acids Extract Dispersion

Abstract: Objective: To evaluate how surfactant-mediated biofilm disruption by hops beta (β)-acids extract influences stannous fluoride (SnF₂) penetration and interaction with extracellular metabolites, including lipopolysaccharide (LPS). Methods: In two studies, oral biofilms were formed in vivo on artificial enamel surfaces mounted in dental appliances worn by volunteers and subsequently treated ex vivo under controlled conditions. Across the studies, biofilms were treated with supernatants of various commercial 0.454% SnF₂ dentifrices containing: (1) pyrophosphate; (2) potassium nitrate (KNO₃) and pyrophosphate; (3) tripolyphosphate; and (4) gluconate/citrate–stabilized 0.454% SnF₂ (Crest) with and without hops β-acids extract (Activ Bio-Cleanser™). Both studies used phosphate-buffered saline as a negative control (NC). Confocal laser scanning microscopy with component-specific fluorescent probes was used to quantify Sn and LPS distribution relative to bacterial biomass, biofilm thickness, and extracellular polymeric substance (EPS) structure. Image analysis was used to quantify Sn and LPS signal within bacterial regions, normalized to bacterial volume or area; statistical comparisons were made across conditions. Results: SnF₂ uptake and penetration varied significantly across formulations. In study 1, the rank order from greatest to least for Sn deposition and LPS neutralization was: gluconate/citrate > KNO₃ + pyro > pyro > NC (P < 0.05 between groups). In study 2, the rank order from greatest to least was: gluconate/citrate + hops > gluconate/citrate > tripolyphosphate and KNO₃ + pyro > NC (P < 0.05 between groups). Some stabilized SnF₂ systems exhibited limited penetration, consistent with diffusion barriers imposed by dense EPS matrices or over-stabilization reducing bioavailability. Gluconate/citrate–stabilized SnF₂-only treated biofilms showed higher deposition per unit bacteria than other SnF₂ technologies but uniformly exhibited the majority of uptake in surface regions. In the formulation containing both hops and SnF₂, increased Sn penetration and reduced detectable biofilm-associated LPS was observed, consistent with enhanced access of SnF₂ to extracellular plaque components following surfactant-enabled biofilm modification. In this case, Sn penetration achieved high relative deposition per unit bacteria in the treated regions throughout the biofilm. Conclusions: Hops β-acids extract acts as a co-surfactant in toothpaste, capable of modifying EPS structure to improve accessibility and interaction of SnF₂ with extracellular metabolites within oral biofilms. The observed changes in Sn penetration and biofilm-associated, extracellular LPS are consistent with enhanced cleaning with reduced concentration of known tissue irritants. Clinical Implications: These findings provide a mechanistic rationale for formulation strategies that enhance SnF₂ accessibility within adherent oral biofilms through surfactant-based modification of EPS supporting more efficient biofilm management during oral hygiene and providing a basis for selecting toothpastes based on their efficacy.

Keywords: surfactant, extracellular polymeric substances, hops β-acids, dental hygiene, toothpaste

Stannous fluoride (SnF₂) is widely formulated into toothpastes and has a long history of use in oral care. Originally utilized in the 1950s for the prevention of dental decay,^1,2 SnF₂ in contemporary formulations offers additional benefits, such as treatment of plaque-associated gingivitis and reduction of dentin hypersensitivity.^3-5 Antiplaque/antigingivitis efficacy is derived from antibacterial actions of SnF₂, including detoxification of the extracellular endotoxins in microbial biofilms.^6-9 As with other toothpaste ingredients, the effectiveness of SnF₂ depends on penetration and retention into target substrates, including adherent oral biofilms.

A distinct challenge for SnF₂ toothpaste design is the need to balance chemical stability with bioavailability.¹⁰ The stannous (Sn²⁺) portion of SnF₂ is prone to oxidation into ineffective stannic, and SnF₂ must be protected from destabilization reactions during formulation and storage. However, the stabilization approaches used to protect Sn²⁺ can influence diffusion, reactivity, and retention (collectively bioavailability) in the oral cavity, creating an inherent formulation trade-off.¹¹ Successful formulation of SnF₂ thus requires the balancing of stability with bioavailability.

This trade-off is particularly relevant in adherent oral biofilms in which bacteria reside within a protective extracellular polymeric substance (EPS) matrix that promotes cohesion, adhesion, and mechanical tenacity on tooth surfaces that can further accumulate tissue-irritating metabolites, including lipopolysaccharides (LPS) and volatile sulfur compounds.¹² As with virtually all microbial populations in nature, oral microbes reside in the oral cavity as 3-dimensional coatings on surfaces, described as biofilms.^13,14 To form biofilms, bacteria produce matrix components that act to “glue” the films together and ensure their tenacity to surfaces.¹⁵ Biofilm matrices are significant contributors to survival of bacterial species^16-20 by presenting a limitation to effective physical removal during hygiene. The EPS-rich matrix can also function as a diffusion barrier that limits the penetration of agents into deeper regions of the biofilm.^15,21,22 As a result, agents may show preferential accumulation near the biofilm surface, with limited penetration into the internal biofilm architecture.²³ In the context of SnF₂, these biofilm transport constraints may interact with formulation stabilization choices to determine how much stannous reaches, penetrates, and is retained within the adherent oral biofilms—namely SnF₂ bioavailability.

Within the broader framework of this special issue, this article addresses the hypothesis that formulation-enabled modification of EPS structure can reduce diffusion barriers and improve delivery of subsequently applied active ingredients during toothbrushing. Prior research has shown that hops beta (β)-acids extract, when delivered as part of an oral care formulation strategy, can solubilize and disperse EPS in ex vivo–treated oral biofilms, consistent with a surfactant-based, physical–chemical cleansing mechanism.²⁴ In this context, hops are positioned as surfactants that loosen EPS-rich adherent oral biofilms, thereby enabling improved access for active ingredients such as SnF₂.

A second gap addressed by this article is the need for penetration metrics that are robust to differences in biofilm thickness and biomass. To enable depth-resolved assessment of delivery within complex biofilm matrices, Procter & Gamble laboratories have successfully developed and applied specific fluorescent staining procedures for confocal laser scanning microscopy (CLSM) to help visualize effects of formulations on in situ–derived biofilms.²⁵ This includes a modified rhodamine B derivative, which is a novel stain developed and patented to provide specific visualization of stannous in complex matrices with excitation at 520 nm to 580 nm and analysis at 560 nm to 660 nm.²⁵ These imaging tools support quantitative evaluation of stannous distribution relative to bacterial biomass and biofilm structure, enabling comparisons of “delivery efficiency” across biofilm states and formulation types.

Accordingly, the purpose of this study was twofold. First, uniquely stabilized commercial SnF₂ toothpastes were compared for stannous uptake, penetration, and retention within in situ–generated adherent oral biofilms to assess the influence of formulation differences. Second, an evaluation assessed whether incorporation of a hops β-acids extract into a gluconate/citrate–stabilized, stannous-containing toothpaste could enhance subsequent stannous uptake and penetration into adherent oral biofilms under controlled ex vivo conditions. In addition, the study design supported assessment of formulation efficacy for removal of extracellular biofilm–associated components related to tissue irritation, LPS, using in situ–derived biofilms.

Methods and Materials

Overview of Experimental Approach

This study used in situ–generated adherent oral biofilms formed on hydroxyapatite (HA) discs mounted on removable oral splints and then treated ex vivo to enable assessment of Sn uptake, penetration, and retention from toothpaste supernatants. Biofilms were: (1) exposed to supernatants prepared from toothpastes to compare delivery behavior under different formulation conditions (Sn stabilization and hops β-acids extract content), and (2) assessed using CLSM with component-specific fluorescent probes to quantify Sn and LPS distribution relative to EPS distribution and bacterial biomass.

Biofilm Donors and Participant Characteristics

In situ biofilms were collected from a panel meeting the following criteria: between 18 to 50 years of age, good general health, free of active oral disease, minimum of 18 natural teeth, and demonstrated measurable plaque accumulation (defined as a score of 2–3 on the Turesky Modified Quigley Hein Plaque Index).^26,27 The protocol was approved by the Procter & Gamble site safety group, and the study followed Good Clinical Practices. All participants provided written informed consent prior to participation.

In Situ Biofilm Generation and Substrate Preparation

Figure 1 shows the in situ plaque biofilm model, which was established based on minimal modification to the bovine dentin groove models.^23,26,28 Instead of bovine, HA discs (Bei’erkang) were used to more closely approximate human enamel mineral composition and provide disc-to-disc uniformity and the necessary structural integrity for groove machining. Discs were 6 mm in diameter and 1 mm in thickness, cut with three parallel grooves perpendicular to the disc surface (the middle groove being 500 µm in both depth and width, and the bilateral grooves being 300 µm in both depth and width). HA discs were fixed onto a customized removeable oral splint on buccal surfaces of molars and premolars for defined periods, allowing for natural biofilm accumulation for 48 hours under normal conditions.

Participants were instructed to wear the oral splint except during meals (during which time the splint would be stored in an opaque container in humid conditions without soaking in liquid) and when performing oral hygiene procedures. During the plaque accumulation phase, participants brushed their teeth using a provided commercial 0.243% sodium fluoride toothpaste (Crest® Cavity Protection, The Procter & Gamble Company, crest.com) and a manual toothbrush (Crest® Velvet Soft Bristle, The Procter & Gamble Company) twice daily during the study. Participants were instructed not to use any other non-study oral hygiene products (eg, dental floss, oral rinse) over the course of the study.

Test Materials and Treatment Conditions

Biofilms were treated with supernatants of commercial 0.454% SnF₂ toothpastes from three manufacturers along with a formulation incorporating hops β-acids extract. The hops β-acids extract was supplied as a commercially available botanical extract (Beta Bio 45%, Hopsteiner, hopsteiner.us), containing approximately 45% β-acids by weight. Phosphate-buffered saline (PBS) was used as a negative control in both studies. The treatments in each study were as follows:

Study 1

a. Negative control: PBS (1x, sterile-filtered, ThermoFisher Scientific Inc., thermofisher.com)

b. SnF₂-pyrophosphate: 0.454% SnF₂ toothpaste (Colgate Total Whitening, Colgate-Palmolive, colgate.com) supernatant

c. SnF₂-pyrophosphate: 0.454% SnF₂ toothpaste (Colgate Total Clean Mint, Colgate-Palmolive) supernatant

d. SnF₂-potassium nitrate (KNO₃)/pyrophosphate: 0.454% SnF₂ toothpaste (Colgate Total Active Penetration Whitening, Colgate-Palmolive) supernatant

e. SnF₂-KNO₃/pyrophosphate: 0.454% SnF₂ toothpaste (Colgate Total Active Penetration Clean Mint, Colgate-Palmolive) supernatant

f. SnF₂-gluconate/citrate: 0.454% SnF₂ toothpaste (Crest Pro-Health Clean Mint, The Procter & Gamble Company) supernatant

g. SnF₂-gluconate/lactate/hexametaphosphate: 0.454% SnF₂ toothpaste (Crest Pro-Health Advanced Deep Clean, The Procter & Gamble Company) supernatant

Study 2

A. Negative control: PBS (1x, sterile-filtered, ThermoFisher Scientific Inc.)

B. SnF₂-KNO₃/pyrophosphate: 0.454% SnF₂ toothpaste (Colgate Total Gum Protect Whitening, Colgate-Palmolive) supernatant

C. SnF₂-tripolyphosphate: 0.454% SnF₂ toothpaste (Parodontax Complete Protection, Haleon, parodontax.com) supernatant

D. SnF₂-gluconate/citrate: 0.454% SnF₂ toothpaste (Crest Pro-Health Gum Detoxify Deep Clean, The Procter & Gamble Company) supernatant

E. SnF₂-gluconate/citrate: 0.454% SnF₂ toothpaste (Crest Pro-Health Advanced Bacteria Protection, The Procter & Gamble Company) supernatant

F. SnF₂-gluconate/citrate-hops: 0.454% SnF₂ toothpaste with 0.15% hops β-acids (Crest Gum Detoxify with Activ Bio-Cleanser™, The Procter & Gamble Company) supernatant

Supernatants were prepared prior to use by mixing 5 g of treatment/toothpaste with 15 mL of ultra-pure water using a homogenizer, followed by centrifugation at 10,000 rpm for 20 minutes. PBS was used as supplied.

Biofilm Treatment and Dispersion Protocols

Following the 48-hour wear period, the biofilm-coated HA discs were removed from the splint and gently rinsed with PBS solution. In situ–derived biofilms on HA discs were treated ex vivo by quiescent immersion in 500 μL of the assigned test solution/toothpaste slurries for 2 minutes. Treated and rinsed HA discs were stored at 4°C prior to microscopy analysis.

Confocal Laser Scanning Microscopy and Fluorescent Labeling

Biofilm structure and composition were evaluated using CLSM. Before imaging, treated biofilms were stained with fluorescent probes selected to enable separate visualization of key biofilm components, as noted in Table 1. Multichannel CLSM imaging was performed to capture spatial distribution and co-localization of bacterial cells, EPS matrix, and mineral components within the biofilm. Six selected fields were considered as representative of the whole sample after the experienced observer’s general examination.²⁶ Optical sectioning enabled assessment of biofilm thickness and internal structure.

All samples were analyzed in 35-mm glass-bottom dishes (Mattek, mattek.com) by CLSM (TCS SP8 AOBS, Leica Microsystems, leica-microsystems.com) using a 40x dry objective (HCX PL APO/bd.BL 40.0, Leica Microsystems). The confocal system consisted of a Leica DM6000B upright microscope and Leica DMIRE2 inverted microscope. Leica™ confocal software LAS AF3.3.0 provided an interface for multidimensional image series acquisitions, processing, and analysis, which included 3D image reconstruction and measurement, physiological recording and analysis, time-lapse, fluorochrome co-localization, spectral inmixing, and multicolor restoration. CLSM image stacks were analyzed to assess changes in biofilm coverage, thickness, and compositional distribution following treatment. Qualitative comparisons focused on EPS integrity, biofilm cohesion, and adhesion to enamel surfaces, while quantitative measurements were used where appropriate to support comparison across treatments.

Fluorescence Probe Staining Microscopy Parameters

Application of fluorescent probes for histomorphological CLSM analysis has been described previously.^23,26,28 An “ion fluorescent probe” refers to a fluorescent probe that specifically binds to one kind of ion/molecule and emits fluorescence at a certain wavelength. HA/biofilm specimens were soaked in 100 µl respective fluorescence solution and incubated at room temperature in the dark for 15 minutes. Table 1 shows probes used in this study.

For the primary penetration analyses, specimens were stained to evaluate bacterial content and Sn²⁺ signal, using SYTO-9 (bacterial label) and a modified rhodamine B derivative for Sn visualization.²⁵ The analysis approach normalized stannous signal to bacterial content to support comparative interpretation across specimens.

Image Sampling Strategy and Thickness Measurement

For each specimen, three selected fields per sample were considered as representative of the whole sample after the observer’s general examination. The biofilm volume was determined from the confocal measurement. This volume was divided by the area of the scan to determine the mean thickness of the biofilm for each specimen.

Statistical Analysis

Each treatment group was evaluated with multiple fields of view on multiple specimens, and treatment differences were summarized using Student-Newman-Keuls multiple-comparison groupings (treatments in different statistical groups differ at P < 0.05). An average value for each HA disc was made based on three fields per disc. Then the average treatment result was obtained by averaging the results from the three treated discs together. Analyses were, therefore, done at the HA disc level (n = 3).

Results

Two ex vivo studies evaluated formulation-dependent differences in Sn deposition and LPS neutralization in in situ–derived adherent oral biofilms treated under standardized conditions using fluorescent markers and CLSM. Sn deposition for studies 1 and 2 is illustrated in Figures 2a and 2b, respectively, while Sn penetration for studies 1 and 2 is depicted in Figures 3a and 3b, respectively. Finally, LPS neutralization for studies 1 and 2 is demonstrated in Figures 4a and 4b, respectively.

In study 1, bacteria-normalized Sn deposition differed across the seven treatment conditions, as reported in Table 2, spanning 0.03 for the negative control (treatment a) to 1.32 for SnF₂-gluconate/citrate Crest Pro-Health Clean Mint (treatment f). The SnF₂-pyrophosphate treatments were the lowest tier of efficacy (0.38 and 0.46, Colgate Total Whitening and Clean Mint, treatments b and c, respectively). The next tier was formed by the SnF₂-KNO₃/pyrophosphate treatments (0.89 and 0.72, Colgate Total Active Penetration Whitening and Clean Mint, treatments d and e, respectively), where there was improvement versus pyrophosphate-only Sn stabilization. The highest tier of efficacy in study 1 consisted of the SnF₂-gluconate/citrate toothpaste and the SnF₂-gluconate/lactate/hexametaphosphate toothpaste (1.32 and 1.28, Crest Pro-Health Clean Mint and Crest Pro-Health Advanced Deep Clean Mint, treatments f and g, respectively). Products within each tier were not significantly different, whereas products in different tiers were significantly different (P < 0.05).

The bacteria-normalized LPS neutralization results in study 1 exhibited a parallel tiering, ranging from 0.18 for the negative control (treatment a) to 1.46 for Crest Pro-Health Clean Mint (treatment f). Treatments b and c again formed the lowest tier (0.69 and 0.77, respectively), and treatments d and e formed the next tier (1.17 and 1.04, respectively). The highest tier again comprised treatments f and g (1.46 and 1.35, respectively). Again, products within tiers were not significantly different, while products in different tiers were significantly different (P < 0.05).

In study 2, bacteria-normalized Sn deposition differed across the six treatment conditions (Table 3), spanning 0.06 for the negative control (treatment A) to 2.18 for SnF₂-gluconate/citrate-hops (Crest Gum Detoxify with Activ Bio-Cleanser, treatment F). The SnF₂-KNO₃/pyrophosphate and SnF₂-tripolyphosphate treatments (1.25 and 1.34, Colgate Total Gum Protect Whitening and Parodontax Complete Protection, treatments B and C, respectively) were the lowest tier of efficacy. The next tier was formed by the SnF₂-gluconate/citrate treatments (1.69 and 1.82, Crest Pro-Health Gum Detoxify Deep Clean and Crest Pro-Health Advanced Bacteria Protection, treatments D and E, respectively), where there was improvement versus KNO₃/pyrophosphate or tripolyphosphate Sn stabilization. The highest tier of efficacy in study 2 consisted of the SnF₂-gluconate/citrate-hops toothpaste (2.18, Crest Gum Detoxify with Activ Bio-Cleanser, treatment F). Products within each tier were not significantly different. Products in different tiers were significantly different (P < 0.05).

The bacteria-normalized LPS neutralization results in study 2 also exhibited a parallel tiering, ranging from 0.34 for the negative control (treatment A) to 1.69 for Crest Gum Detoxify with Activ Bio-Cleanser (treatment F). Treatments B and C formed the lowest tier (0.73 and 0.76, respectively), and treatments D and E formed the next tier (0.92 and 0.98, respectively). The highest tier comprised treatment F (1.69). Again, products within tiers were not significantly different, while products in different tiers were significantly different (P < 0.05).

Across both studies, the lowest bacteria-normalized values for both endpoints occurred in the respective negative control groups (treatment a in study 1; treatment A in study 2), while the highest tiers were observed among the top-performing treatments in each study (treatments f/g in study 1; treatment F in study 2). Results for the hops-containing, SnF₂ toothpaste stabilized with gluconate/citrate (treatment F, study 2) were universally the highest observed across both studies. In both studies, the statistical tiering for neutralized LPS closely tracked the tiering observed for bacteria-normalized Sn deposition, with intermediate comparator groups clustering together and the upper-tier formulations clustering. Taken together, the two studies demonstrate that dentifrice formulations containing the same level of 0.454% SnF₂ can differ substantially in bacteria-normalized Sn deposition into adherent oral biofilms and in the associated bacteria-normalized neutralized LPS results under controlled ex vivo conditions.

Discussion

This research used CLSM histomorphological analysis to evaluate formulation-dependent differences in Sn deposition and penetration within in situ–derived adherent oral biofilms treated ex vivo and to quantify associated neutralization of biofilm-associated, extracellular LPS. Across two studies, Sn deposition and LPS neutralization per unit bacteria showed consistent tiering patterns across treatment sets, demonstrating that dentifrice formulations can differ substantially in delivery and interaction behavior in adherent oral biofilms under controlled conditions despite the formulations being comprised of similar levels of SnF₂ (0.454%). In study 1, Crest Pro-Health formulations formed the highest tier relative to the other variants, while in study 2 the hops-containing, gluconate/citrate–stabilized SnF₂ formulation (Crest Gum Detoxify with Active Bio-Cleanser) formed the highest tier for both bacterial-normalized endpoints relative to stabilized SnF₂ comparators without hops. These findings provide a mechanistic basis for statistically significant differences in gingivitis outcomes observed in clinical studies evaluating various 0.454% SnF₂ toothpastes with different formulation chemistry.^29,30

A central interpretation of these findings is that Sn stabilization strategy appears to influence functional bioavailability in adherent oral biofilms.¹⁰ The study design intentionally compared systems with distinct stabilization chemistries and then observed a tiering pattern in both studies that is consistent with the concept that stabilization approaches can create meaningful differences in how readily Sn species can move into, persist within, and interact across EPS-rich biofilms. In study 1, the pyrophosphate-only stabilized Colgate Total formulations clustered in a lower tier than the KNO₃/pyrophosphate “active penetration” formulations, and both were lower than the Crest Pro-Health stabilized systems (gluconate/citrate or gluconate/lactate/hexametaphosphate). In study 2, Colgate Total Gum Protect Whitening and Parodontax Complete Protection clustered together below the Crest stabilized system, which in turn were below the hops-containing Crest system, reinforcing the premise that formulation design and stabilizer choices are associated with measurable differences under identical biofilm and exposure conditions.

Like most biofilms, adherent oral biofilms are comprised of a variety of bacterial species embedded in an EPS matrix. EPS serves to protect films from dispersion but also create diffusion, oxidation, and potential gradients, which help in the retention and maturation of the adherent oral biofilm. EPS is recognized to be a factor in interfering with diffusion and uptake of chemotherapeutics into plaque.³¹ All formulations showed a gradient of stannous uptake and retention, with levels concentrated near the surfaces of the biofilms. This uptake pattern is commonly observed for cationic antimicrobials (eg, chlorhexidine²³) and is influenced by strong binding and reactivity in biofilms throughout the plaque structure. Within this EPS-mediated framework, the stabilization system is relevant not only to the shelf stability of Sn but also to how effectively the stabilized Sn system can access and move through EPS microdomains once delivered to the biofilm surface.

Incorporation of hops β-acids extract into a gluconate/citrate–stabilized SnF₂ formulation was associated with a step-change in bacteria-normalized Sn deposition and neutralized LPS compared with stabilized SnF₂ systems without hops in study 2. This research illustrates that hops β-acids extract has affinity for the EPS matrix of the adherent oral biofilms, and treatment with hops produces dispersion of biofilm from surfaces.²⁴ Interpreted through the EPS-mediated barrier model, these results are consistent with the idea that hops β-acids reduce matrix-imposed barriers that otherwise constrain transport of stabilized Sn. If stabilizer choice affects how well a stabilized Sn system can access or traverse EPS microdomains, then partial removal or loosening of EPS structure provides the stabilizer–Sn system a less restrictive environment in which its inherent bioavailability can be more fully expressed. Under this model, hops act to modify the physicochemical biofilm environment as a surfactant-based cleanser, enabling more effective distribution and interaction of the stabilized Sn system within adherent oral biofilms.

Several limitations should be recognized when interpreting these findings. First, the experimental model involves in situ–derived oral biofilms grown under intraoral conditions but treated ex vivo, which enables controlled comparisons but does not fully reproduce all the dynamics of repeated-use brushing regimens or longitudinal measurements. Second, sample sizes per treatment were modest (N = 3), and the statistical groupings should be interpreted accordingly. Third, while the observed patterns are consistent with EPS-mediated transport constraints and excipient-enabled matrix modification, definitive mechanistic attribution (eg, specifying the exact EPS microdomains interacting with the various Sn stabilizers or Sn species) is beyond the scope of this study and is instead addressed conceptually.

Conclusion

These studies demonstrate that toothpaste formulations with the same level of SnF₂ differed meaningfully in bacteria-normalized Sn deposition and associated LPS neutralization within in situ–derived adherent oral biofilms treated under controlled ex vivo conditions. Differences among Sn stabilization systems were associated with distinct delivery profiles in EPS-rich matrices. Incorporation of hops β-acids extract into a gluconate/citrate–stabilized SnF₂ formulation was associated with a further increase in bacteria-normalized Sn deposition and LPS neutralization relative to formulas without hops. Together, these findings provide mechanistic substantiation that the formulation strategies combining optimized Sn stabilization with EPS-cleansing excipients can enhance accessibility and interaction of SnF₂ within adherent oral biofilms. This establishes a plausible foundation for observed differences in breath-related measurements evaluated in subsequent work³² in this special issue.

ACKNOWLEDGMENT

The authors thank Donald J. White, PhD, for medical writing assistance.

DISCLOSURE

The authors are employees of The Procter & Gamble Company, the funder of the research and medical writing assistance.

ABOUT THE AUTHORS

Samuel St. John, PhD
The Procter & Gamble Company, Mason, Ohio

Ross Strand, BS
The Procter & Gamble Company, Mason, Ohio

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