Protective effects of SnF2 - Part II. Deposition and retention on pellicle-coated enamel

Effect of an experimental TiF4/NaF solution in preventing tooth erosion

OBJECTIVE

This was a randomized, double-blind, parallel, placebo-controlled in vivo study investigating the protective potential of a titanium tetrafluoride/ sodium fluoride (TiF4/NaF) solution compared to its respective positive and negative controls under an in vivo model, as well as the perception of participants regarding the use of this experimental solution.

METHODS

After the ethics approval and the selection procedures, 33 participants were divided into three treatments: TiF4/NaF solution (500 ppm F, pH 4.4); AmF/NaF/SnCl2-mouthwash (500 ppm F, pH 4.5) and water (pH 7.0) (n = 11). After professional cleaning, the participants rinsed with one of the solutions for one minute and waited two hours for the erosive challenge. The erosive solution (1 % citric acid, pH 2.5) was applied for 10 s on each central incisor (enamel area: 4 mm2) and collected for calcium analysis using III Arsenazo colorimetric method. The Ca2+ release data were compared using Kruskal-Wallis/ Dunn tests (p < 0.05).

RESULTS

Teeth treated with both fluoride solutions released less calcium into the acid (median and interquartile interval: TiF4/NaF - 0.45/0.19 mM and AmF/NaF/SnCl2 - 0.46/0.15 mM Ca2+, p = 0.99) compared to the negative control (1.12/0.42 mM Ca2+, 60 % reduction, p < 0.0006). For both F solutions, only one participant per group reported unpleasant taste. Four participants belonging to AmF/NaF/SnCl2-mouthwash reported burning sensation post-rinse, while only one participant described such feeling after TiF4/NaF rinsing.

CONCLUSION

The experimental TiF4/NaF solution was as effective as the commercial AmF/NaF/SnCl2-mouthwash in protecting enamel against erosive demineralization with a good acceptability by the participants.

Combined use of stannous fluoride-containing mouth rinse and toothpaste prevents enamel erosion in vitro

OBJECTIVE

To compare the protective effect of commercial stannous-containing mouth rinses on enamel erosion in a simulated 5-day in vitro cycling model.

MATERIALS AND METHODS

81 human enamel specimens were embedded in resin blocks and divided into nine groups as follows; group 1: stannous fluoride (1000SnF2) toothpaste; groups 2,3, and 4 were the same as group 1 plus Elmex®, PerioMed™, and Meridol®, respectively, group 5: stannous fluoride (1450SnF2) toothpaste, groups 6, 7, and 8 were the same as group 5 plus Elmex®, PerioMed™, and Meridol®, respectively, group 9: negative control. An erosive challenge was induced with a 1 min hydrochloric acid (0.01 M, pH 2.2) treatment 3 times per day. Each cycle included immersing in the toothpaste slurry twice for two minutes and a one-minute rinse. The enamel slabs were immersed in artificial saliva between each erosive cycle and incubated overnight at 37 °C. Surface hardness loss and enamel loss were determined by Knoop surface hardness and non-contact profilometry, respectively. Finally, enamel surfaces were analyzed by scanning electron microscopy and X-ray energy dispersive spectroscopy (SEM/EDS).

RESULTS

All three mouth rinses had similar protective effects against erosion when using adjunct with 1000 SnF2 toothpaste (p > 0.05). With 1450 SnF2 toothpaste, Elmex® presented significantly lower surface hardness loss than Meridol® (p < 0.05). The combined use of Elmex® or PerioMed™ with toothpaste provided significantly better erosion protection than toothpaste alone, either 1000 or 1450 SnF2. In addition, 1000SnF2 toothpaste adjunct with mouth rinse is comparable to 1450 SnF2 toothpaste alone in preventing enamel erosion.

CONCLUSION

All three mouth rinses reduced enamel erosion. The additional use of a high concentration stannous containing mouth rinse with 1450 SnF2 toothpaste increases the protective effect against enamel erosion in vitro.

CLINICAL SIGNIFICANCE

To date, no standard protocol for preventing dental erosion is available. There are three stannous-containing mouth rinses on the market; however, no study compared their efficacy or indicated whether using adjuncts with anti-erosion toothpaste provides additional benefits. This study found that adding stannous mouth rinse to twice-daily toothpaste increases erosion protection.

Bioavailable gluconate chelated stannous fluoride toothpaste meta-analyses: Effects on dentine hypersensitivity and enamel erosion

OBJECTIVES

To compare the effect of bioavailable gluconate-chelated stannous fluoride (SnF₂) toothpaste with control toothpastes for treatment of dentine hypersensitivity (DH) and enamel erosion.

DATA AND SOURCES

A Procter & Gamble Oral Care archive of clinical studies was reviewed from 2000 to 2020. Eligible studies were Randomised Controlled Trials (RCTs) investigating bioavailable gluconate-chelated SnF₂ toothpaste efficacy compared to controls in adult participants measured following tactile (Yeaple force) and/or evaporative stimuli (Schiff score) in-vivo, duration <2 months (DH); or by erosive toothwear (profilometry) from in-situ samples, duration 10-15 days. Two authors independently assessed eligibility and resolved disagreements by discussion. A meta-analysis was undertaken and Risk of Bias (RoB) assessed using the Cochrane collaboration RoB tool for randomized parallel-group and cross-over trials.

RESULTS

Fourteen RCTs (1287 participants) assessed DH relief and Six RCTs (184 participants) enamel erosion protection. For DH SnF₂ toothpastes provided a 57 % (evaporative air) and 142 % (tactile) benefit versus negative controls (sodium fluoride/monofluorophosphate, 8 studies; p < 0.001). Compared to positive controls (potassium nitrate or arginine, 6 studies), a 22 % advantage (p = 0.036) was seen for evaporative air. In erosion studies, SnF₂ toothpastes provided an 83 % benefit versus control toothpastes (arginine or sodium fluoride; p < 0.001) with a change (95 %CI) in average surface profilometry level (μm) of -2.02(-2.85, -1.20).

CONCLUSIONS

The use of these bioavailable SnF₂ toothpastes, as part of a daily oral hygiene regimen, will provide patients with enamel erosion protection, combined with alleviation of DH pain when present, improving quality of life.

Fluoride dentifrice containing calcium silicate and sodium phosphate salts on dental erosion: In vitro study

OBJECTIVE

To investigate the effect of a commercial dentifrice containing fluoride, calcium silicate, and sodium phosphate and its dual phase gel serum to prevent erosive tooth wear in enamel.

METHODS

Forty-eight enamel specimens were selected by surface hardness and randomly allocated into 4 groups (n = 12) according to the commercial toothpastes: non-fluoridated (NF); 1100 ppm Stannous fluoride (SnF₂); 1450 ppm MFP + calcium silicate + sodium phosphate (CSSP); CSSP + dual-phase gel (CSSP + Serum). Cyclic experiments were repeated 3x / day for five days, including an erosive challenge with 0.05 M citric acid (pH 3.75 for 30 s), treatment with toothpaste slurries (1 min), and remineralization with artificial saliva (pH 7.0 for 60 min). Surface alterations were determined by stylus profilometry (μm) and scanning electron microscopy (SEM). Data were analyzed by ANOVA and Tukey tests (α = 0.05).

RESULTS

SnF₂, CSSP and CSSP + Serum significantly reduce surface wear compared to NF treated group. Besides, there were no significant differences among SnF₂, CSSP and CSSP + Serum. In micrographs of both groups treated with CSSP, the surface demonstrates the presence of a protective layer as a deposition of particles.

CONCLUSIONS

Dentifrice containing calcium silicate and sodium phosphate with or without the dual-phase gel was able to prevent the erosive tooth wear.

Randomized in situ clinical trial evaluating erosion protection efficacy of a 0.454% stannous fluoride dentifrice

OBJECTIVES

To assess the protective effects of a 0.454% stabilized stannous fluoride dentifrice and a marketed triclosan dentifrice against enamel erosion in a 10-day in situ model.

METHODS

This was a double-blind, randomized, 2-treatment, 4-period, crossover in situ trial involving healthy adult participants. Participants were randomized to a treatment sequence involving the following products: a highly bioavailable 0.454% stannous fluoride dentifrice (Procter & Gamble) and a marketed dentifrice control containing 0.24% sodium fluoride and 0.3% triclosan (Colgate-Palmolive). Each study period took place over 10 days. Participants wore an intra-oral appliance retaining two polished human enamel samples for 6 hours per day. Two times per day they swished with the assigned dentifrice slurry and four times per day they swished with 250 mL of orange juice (25 mL per minute) over a 10-minute period. Contact profilometry measurements were made for each sample at baseline and day 10 to determine surface change.

RESULTS

Thirty-six participants were enrolled and 33 completed the study (mean age = 40.5 years). The stannous fluoride dentifrice demonstrated 93.5% less enamel loss than the NaF/triclosan dentifrice (P < 0.001) at Day 10, with median enamel loss of 0.097 µm and 1.495 µm, respectively. Both products were well tolerated.

CONCLUSION

The stannous fluoride dentifrice demonstrated significantly greater erosion protection efficacy relative to the NaF/triclosan dentifrice in this randomized in situ clinical trial.

Clinical effect of stannous fluoride and amine fluoride containing oral hygiene products: A 4-year randomized controlled pilot study

This 4-year randomized controlled trial (RCT) aimed at investigating whether routine home use of both a SnCl₂/AmF/NaF-containing mouth rinse and toothpaste has a preventive effect on oral health. Fifty-four test subjects were examined in biannual intervals. The primary endpoint “dental erosion” was determined by the Basic Erosive Wear Examination (BEWE). The secondary endpoints were “saliva pH”, “dentin hypersensitivity” generated by Visual Analogue Scale (VAS), and “discoloration” measured by the Lobene Stain Index (LSI). A mixed model for repeated measures (MMRM) was used to analyze the primary endpoint “dental erosion”. Primary analysis showed a significant intervention effect of the SnCl₂/AmF/NaF-containing test product (p₁ = 0.0242). This result was confirmed by two additional MMRM-based sensitivity analyses. Comparison of all models showed “dental erosion” values of the intervention group  below values of the control group. Discoloration of the teeth was significantly higher in the intervention than in the control group at all time points. Saliva pH and dentin hypersensitivity were not significantly different between groups over four years. In summary, this RCT is the first to indicate a possible preventive effect of SnCl₂/AmF/NaF-containing oral hygiene products on dental erosion over a follow-up period of four years.

Effect of fluoride mouthrinses and stannous ions on the erosion protective properties of the in situ pellicle

The particular feature of this study is the investigation of effects of pure fluoride- or stannous ions based mouthrinses on the erosion protective properties and the ultrastructure of the in situ pellicle (12 volunteers). Experimental solutions were prepared either from 500 ppm NaF, SMFP, AmF or SnF₂ or 1563 ppm SnCl₂, respectively. After 1 min of in situ pellicle formation on bovine enamel slabs, rinses with one of the preparations were performed for 1 min and intraoral specimens’ exposure was continued for 28 min. Native enamel slabs and rinses with bidestilled water served as controls. After oral exposure, slabs were incubated in HCl (pH 2; 2.3; 3) for 120 s and kinetics of calcium- and phosphate release were measured photometrically; representative samples were analysed by TEM and EDX. All mouthrinses reduced mineral loss compared to the native 30-min pellicle. The effect was pH-dependent and significant at all pH values only for the tin-containing mouthrinses. No significant differences were observed between the SnF₂- and the SnCl₂-containing solutions. TEM/EDX confirmed ultrastructural pellicle modifications. SnF₂ appears to be the most effective type of fluoride to prevent erosive enamel demineralisation. The observed effects primarily have to be attributed to the stannous ions’ content.

Frequency of Application of AmF/NaF/SnCl2 Solution and Its Potential in Controlling Human Enamel Erosion Progression: An in situ Study

Although several studies have demonstrated the efficacy of AmF/NaF/SnCl2 solution in inhibiting dental erosion progression, measures for further improvement in its effectiveness are paramount. Thus, this in situ study evaluated whether the protective effect promoted by the AmF/NaF/SnCl2 solution would be enhanced by increasing its frequency of use. The study was conducted with 12 volunteers, a 4-phase (5 days each) randomized, crossover model. Extraoral erosive challenges (0.5% citric acid, pH 2.6, 6 × 2 min/day) and rinsing protocol (1 or 2 × 2 min/day) were performed. Before the in situ phase, human enamel samples were subjected to an in vitro surface softening (1% citric acid, pH 4.0, for 3 min). Four treatment protocols were tested using samples in replicas (n = 12): group G1 - deionized water (negative control); G2 - NaF solution (positive control, 500 ppm F-, pH 4.5); G3 - AmF/NaF/SnCl2 solution (500 ppm F-, 800 ppm Sn2+, pH 4.5) once a day; G4 - AmF/NaF/SnCl2 solution twice a day. Tissue loss and morphological changes were determined by optical profilometry (n = 12) and scanning electron microscopy (n = 3) analysis, respectively. Data were statistically analyzed by ANOVA with subsequent pairwise comparison of treatments. Tissue loss means (±SD in µm) for each treatment protocol and statistical differences were found as follows: G1 4.55 ± 2.75, G2 4.59 ± 2.13, G3 2.64 ± 1.55, and G4 1.34 ± 1.16. Although there was no difference between the 2 AmF/NaF/SnCl2 solution application regimens (once or twice a day), application of the product twice a day was the only treatment that was able to control erosion progression, differing from the control groups.

Erosion protection benefits of stabilized SnF2 dentifrice versus an arginine-sodium monofluorophosphate dentifrice: results from in vitro and in situ clinical studies

Objectives

The aim of these investigations was to assess the ability of two fluoride dentifrices to protect against the initiation and progression of dental erosion using a predictive in vitro erosion cycling model and a human in situ erosion prevention clinical trial for verification of effectiveness.

Materials and methods

A stabilized stannous fluoride (SnF₂) dentifrice (0.454 % SnF₂ + 0.077 % sodium fluoride [NaF]; total F = 1450 ppm F) [dentifrice A] and a sodium monofluorophosphate [SMFP]/arginine dentifrice (1.1 % SMFP + 1.5 % arginine; total F = 1450 ppm F) [dentifrice B] were tested in a 5-day in vitro erosion cycling model and a 10-day randomized, controlled, double-blind, two-treatment, four-period crossover in situ clinical trial. In each study, human enamel specimens were exposed to repetitive product treatments using a standardized dilution of test products followed by erosive acid challenges in a systematic fashion.

Results

Both studies demonstrated statistically significant differences between the two products, with dentifrice A providing significantly better enamel protection in each study. In vitro, dentifrice A provided a 75.8 % benefit over dentifrice B (p < 0.05, ANOVA), while after 10 days in the in situ model, dentifrice A provided 93.9 % greater protection versus dentifrice B (p < 0.0001, general linear mixed model).

Conclusion

These results support the superiority of stabilized SnF₂ dentifrices for protecting human teeth against the initiation and progression of dental erosion.

Clinical relevance

Stabilized SnF₂ dentifrices may provide more significant benefits to consumers than conventional fluoride dentifrices.

The Future of Fluorides and Other Protective Agents in Erosion Prevention

The effectiveness of fluoride in caries prevention has been convincingly proven. In recent years, researchers have investigated the preventive effects of different fluoride formulations on erosive tooth wear with positive results, but their action on caries and erosion prevention must be based on different requirements, because there is no sheltered area in the erosive process as there is in the subsurface carious lesions. Thus, any protective mechanism from fluoride concerning erosion is limited to the surface or the near surface layer of enamel. However, reports on other protective agents show superior preventive results. The mechanism of action of tin-containing products is related to tin deposition onto the tooth surface, as well as the incorporation of tin into the near-surface layer of enamel. These tin-rich deposits are less susceptible to dissolution and may result in enhanced protection of the underlying tooth. Titanium tetrafluoride forms a protective layer on the tooth surface. It is believed that this layer is made up of hydrated hydrogen titanium phosphate. Products containing phosphates and/or proteins may adsorb either to the pellicle, rendering it more protective against demineralization, or directly to the dental hard tissue, probably competing with H+ at specific sites on the tooth surface. Other substances may further enhance precipitation of calcium phosphates on the enamel surface, protecting it from additional acid impacts. Hence, the future of fluoride alone in erosion prevention looks grim, but the combination of fluoride with protective agents, such as polyvalent metal ions and some polymers, has much brighter prospects.

Protective effects of SnF2 - Part I. Mineral solubilisation studies on powdered apatite

PURPOSE

To compare the ability of two active ingredients - sodium fluoride (NaF) and stannous fluoride (SnF2 ) - to inhibit hydroxyapatite (HAP) dissolution in buffered acidic media.

METHODS

Two in vitro studies were conducted. HAP powder, which is representative of tooth mineral, was pretreated with: test solutions of NaF or SnF2 , 10 g solution per 300 mg HAP powder (Study 1); or NaF or SnF2 dentifrice slurry supernatants, 20 g supernate per 200 mg HAP powder for 1 minute followed by three washes with water, then dried (Study 2). About 50 mg of pretreated HAP was exposed to 25 ml of acid dissolution media adjusted to and maintained at pH 4.5 in a Metrohn Titrino reaction cell. Exposure of HAP to the media results in dissolution and release of hydroxide ion, increasing the pH of the solution. The increase in pH is compensated for by automatic additions of acid to maintain the original pH (4.5) of the reaction cell. Total volume of titrant added after 30 minutes was used to calculate the percentage reduction in dissolution versus non-treated HAP control.

RESULTS

Both F sources provided protection against acid dissolution; however, in each study, SnF2 -treated HAP was significantly more acid-resistant than the NaF treated mineral. In study 1, at 280 ppm F, representing concentrations of F found in the mouth after in vivo dentifrice use, the reduction in HAP dissolution was 47.7% for NaF and 75.7% for the SnF2 -treated apatite (extrapolated). In study 2, the reduction in HAP dissolution was 61.3% for NaF and 92.8% for SnF2 -treated samples. Differences in percentage reduction were statistically significant (Paired-t test).

CONCLUSIONS

Results of these studies demonstrate that both of the fluoride sources tested enhance the acid resistance of tooth mineral and that resistance is significantly greater after treatment with SnF2 compared with treatment of tooth mineral with NaF.

Protective effects of SnF2 - Part III. Mechanism of barrier layer attachment

OBJECTIVE

To assess the ability of various fluoride salts to protect enamel against acid attack via a barrier mechanism.

METHODS

Extracted human enamel specimens were cleaned and rinsed, then soaked in pooled human saliva for 1 hour to initiate formation of an early pellicle. Groups of three specimens each were etched for 10 minutes in 1% citric acid (pH 2.3), treated in a 1:3 slurry of dentifrice [1,100 ppm F as stannous fluoride (SnF2 ), 1,100 ppm F as sodium fluoride (NaF), 1,000 ppm F as sodium monofluorophosphate (SMFP), or 1,400 ppm F as amine fluoride (AmF)] and saliva for 2 minutes, exposed to 2% alizarin red-S (a calcium-selective dye) and rinsed again. The relative ability of each test product to deposit a barrier layer on the enamel surface was measured by its ability to protect against attachment of the calcium-selective dye.

RESULTS

Specimens treated with the SnF2 dentifrice showed the least dye attachment, indicating a high level of surface protection. On a five-point scale, with 0 being no dye deposition (100% protection) and four being complete dye coverage (0% protection), the SnF2 -treated specimens scored an average of 0.25, with NaF scoring 3.4, SMFP scoring 3.4 and AmF scoring 3.7. Protection of the enamel surface was significantly higher for the SnF2 product than for the other products (P < 0.05), with no significant differences among the other three F salts.

CONCLUSIONS

These results demonstrate that after an aggressive acid challenge, SnF2 deposits a barrier layer onto the pellicle-coated enamel surface, and the barrier layer which attaches onto acid challenged tooth surfaces is different from any that might be provided by treatment with the other fluoride compounds tested.