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.

Erosion protection comparison of stabilised SnF2 , mixed fluoride active and SMFP/arginine-containing dentifrices.

PURPOSE: To investigate the relative erosion protection potential of marketed dentifrices formulated with either stabilised stannous fluoride (SnF2 ), sodium fluoride (NaF) and/or sodium monofluorophosphate (SMFP) using an established laboratory erosion cycling model. METHODS: Sound enamel cores from extracted, human enamel were cleaned, ground and polished, soaked in pooled saliva (pellicle formation) and treated with a 1:3 slurry of dentifrice and saliva. Specimens were subjected to daily challenges with 1% citric acid, a potentially damaging acid found in common food and drinks. Marketed dentifrices compared were: (1) a stabilised stannous fluoride product formulated with 1,100 ppm F as SnF2 ; (2) a cavity protection product containing 1,100 ppm F as NaF; (3) a cavity protection product comprising a mixed active fluoride system with 1,000 ppm F as SMFP + 450 ppm F as NaF; and (4) a sensitivity product containing 1,450 ppm F as SMFP + 8% arginine bicarbonate. RESULTS: Specimens from Group 1 demonstrated an average loss of 5.5 (±1.2) µm of tooth surface enamel; Groups 2, 3 and 4 lost an average of 18.3 (±0.9) µm, 16.0 (±2.0) µm and 17.1 (±1.1) µm, respectively, of tooth surface enamel. Group 1 provided a statistically significant difference in protection compared with the other products. CONCLUSIONS: These results suggest that the marketed dentifrice formulated with stabilised SnF2 may provide enhanced protection of exposed tooth surfaces against dietary acid attack compared with the other products tested.

Protective benefits of a stabilised stannous-containing fluoride dentifrice against erosive acid damage.

PURPOSE: To assess the potential of a stabilised stannous (Sn)-containing NaF dentifrice (Oral B/blend-a-Med(®) Pro-Expert), in addition to a number of other marketed European dentifrices formulated with various fluoride actives and two control dentifrices, to protect enamel against erosive acid damage. METHODS: Cores of human enamel (four per group) were soaked in pooled human saliva, and then treated with a 1:3 slurry (dentifrice:saliva) using a standardised in vitro erosion model (5-day cycling) that includes 10-minute challenges with 1% citric acid applied 60 minutes after each dentifrice treatment. Enamel surface loss was measured using transverse microradiography (TMR). RESULTS: Specimens treated with the Sn-containing NaF dentifrice showed 6.5 µm of surface loss ± 1.2 (SEM), which was not significantly different (P < 0.05, Fisher LSD) from that of a clinically proven, stabilised SnF2 positive control [Crest(®) Pro-Health, 1,100 ppm F as SnF2 : 3.0 µm of surface loss ± 1.1 (SEM)]. The Sn-containing NaF dentifrice and the clinically proven positive control both provided significantly greater protection (P < 0.05, Fisher LSD) compared with all of the other products tested. Enamel loss (SEM) values for other European products and the reference control (active agents) were: Meridol(®) : (1,400 ppm F as AmF + SnF2 ) 12.0 µm (1.47); Colgate(®) Cavity Protection: (1,450 ppm F as SMFP + NaF) 12.9 µm (1.66); Odol med 3(®) (1,400 ppm F as NaF) 14.2 µm (1.49); Elmex(®) (1,400 ppm F as AmF) 14.5 µm (1.76); Colgate(®) Enamel Protect: (1,450 ppm F as NaF + KNO3 ) 16.3 µm (2.02); Lacalut(®) aktiv: (1,400 ppm F as AlF3 ) 18.5 µm (1.71); Sensodyne(®) ProNamel(™) : (1,450 ppm F as NaF + KNO3 ) 20.5 µm (1.26); Crest Cavity Protection (1,100 ppm F as NaF, reference control) 22.00 µm (2.04); and Mentadent(®) : (1,450 ppm F as NaF + Zn citrate) 22.3 µm (0.63). CONCLUSION: These results support the potential for the stabilised, Sn-containing NaF dentifrice to provide erosion protection benefits that are not significantly different from the positive control benchmark for erosion protection (stabilised SnF2 ), and are significantly better than a broad range of dentifrice formulations available on the European market.

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

UNLABELLED: Deposition of an acid-resistant barrier onto enamel represents a potentially superior means for delivering protection against dietary, erosive acid challenges. PURPOSE: The purpose of this study was to demonstrate the ability of a stabilised stannous fluoride (SnF2 ) dentifrice to: (1) deposit a SnF2 barrier layer onto pellicle-coated enamel surfaces; (2) increase the intensity of the barrier layer over time; and (3) be retained on the enamel surface for hours after product use. METHODS: Squares of human enamel were exposed to pooled saliva for 1 hour (pellicle formation) and separated into six sets. Set 1 was treated with the supernatant of a 1:3 slurry of the test dentifrice (Crest(®) Pro-Health(®) : water for 2 minutes), then rinsed. Set 2 was treated in the same manner and then placed into saliva (6 hours). Set 3 was cycled through seven repeated treatments. Set 4 was treated for seven cycles and then placed into saliva (6 hours). Set 5 was a water control, and set 6 was a water control that remained in saliva for 6 hours. Surface analysis of specimens was done using laser ablation Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). RESULTS: Deposition of a barrier layer was demonstrated, beginning with the initial treatment, with Sn (using isotopes (117) Sn + (120) Sn) measured on the enamel surface as the reference marker. Deposition of the barrier layer was greater after seven cycles, and the retention of this layer was highly significant (P = 0.05, anova: 6 hours). CONCLUSIONS: This study confirms that: (1) the stabilised SnF2 dentifrice deposits a barrier layer onto the enamel surface, beginning with the first use of the product; (2) this barrier is enhanced following multiple treatments; and (3) the barrier layer is retained on the enamel surface for hours after product use.

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.

Enamel protection: a comparison of marketed dentifrice performance against dental erosion.

PURPOSE: To determine the relative ability of various marketed toothpastes formulated with either stabilized stannous fluoride (SnF2), sodium fluoride (NaF), or sodium monofluorophosphate (SMFP) to protect human enamel against the initiation and progression of damage due to dietary acid attack, using a laboratory erosion cycling model. METHODS: Cores of ground and polished enamel from extracted human teeth were soaked in pooled, human saliva (pellicle formation) and then subjected to erosion cycling conditions that included exposure of tooth specimens to: (1) treatments in a 1:3 slurry (w/w) of toothpastes and saliva; and (2) acid challenges using either citric acid (Study 1) or both citric and phosphoric acids (Study 2). These acids represent potentially damaging acids found in common food and drinks. Upon completion of treatments, specimens were analyzed with regard to the depth of tooth mineral removed from exposed areas of the treated specimens over the course of the study. Two studies were conducted: Study 1 included a marketed, stabilized SnF2 toothpaste vs. marketed NaF toothpastes; Study 2 tested the same stabilized SnF2 product compared to a marketed SMFP toothpaste and a NaF control. RESULTS: The stabilized SnF2 toothpaste included in these studies demonstrated a highly significant reduction in enamel surface loss, relative to the control, in each study: Study 1 = 65% reduction; Study 2 = 58% reduction when using citric acid and 84% reduction when using phosphoric acid. Products formulated with NaF resulted in a net loss of between +1% and -21%, with none of the NaF toothpastes performing significantly different from the control (P<0.05, ANOVA). For the SMFP product included in Study 2, results were also not significantly different from the NaF control. In both studies, the stabilized SnF2 paste demonstrated a highly significant level of protection compared to all other test groups included in the study, regardless of the type of dietary acid challenge considered.

Recommendation for a non-animal alternative to rat caries testing.

PURPOSE: As a requirement of the Food & Drug Administration's final monograph on "Anticaries drug products for over-the-counter human use", the toothpaste industry has been conducting animal caries tests on every fluoride-containing toothpaste introduced into the U.S. market since 1996. The practice of testing in animals, although required by law, is in stark conflict with the corporate policy of many U.S. and global toothpaste manufacturers, in which, if possible, alternatives to animal testing are utilized. A provision does exist within the regulation which allows the use of an alternative method to demonstrate efficacy. However, to take advantage of this provision, a petition must be submitted to the FDA and in this petition data demonstrating the alternative provides results of "equivalent accuracy" must be included. After many years of research, model development and model comparisons, we have identified one particular laboratory model that demonstrated excellent correlation with the currently accepted animal caries models. This model, known as the Featherstone pH cycling model, is discussed in this paper. METHODS: The Featherstone pH cycling model has been shown to produce results of equivalent accuracy to the animal caries model by: (1) demonstrating a clinically relevant fluoride dose response similar to that shown in the animal caries model (including 1100 ppm F, 250 ppm F and placebo); (2) demonstrating similar results to the animal caries model for clinically proven dentifrice formulations relative to positive and negative controls; (3) demonstrating discriminating ability in strong agreement with the animal caries model for differentiating between a dentifrice formulation with attenuated fluoride activity and a USP standard; and (4) providing a clinically relevant representation of the caries process, as demonstrated by orthodontic banding studies. In addition, the model sufficiently addresses both salivary and abrasive/anticalculus agent interference concerns. RESULTS: For more than 50 years, fluoride has been the first defense in the fight against dental caries. The clinical effectiveness of fluoride is well accepted and documented extensively in the literature. The mechanism through which fluoride provides its benefit is very straightforward and well understood. The proposed laboratory model effectively simulates the effect of the caries process and has been shown to demonstrate equivalent accuracy to animal caries. This indicates that there are strong scientific grounds for the use of this model as an alternative to the animal caries test. Based on the strength of the data and the correlations noted between the two models, we recommend that the scientific community and the toothpaste industry broadly accept the Featherstone laboratory pH cycling model as an appropriate alternative to animal testing, particularly for ionic fluoride based dentifrices.

The Featherstone laboratory pH cycling model: a prospective, multi-site validation exercise.

PURPOSE: To demonstrate the robustness of the Featherstone pH cycling model when tested in three independent laboratories and to evaluate the use of "non-inferiority" testing at those laboratories. METHODS: The fundamental principles for the Featherstone laboratory pH cycling model to be an appropriate alternative to animal testing is that it must demonstrate equivalent accuracy to the "Gold Standard" (rat caries model) by: (1) providing a meaningful representation of the caries process; (2) demonstrating a proportionate response to fluoride dose (or concentration); (3) being able to show that clinically proven formulations perform similarly relative to the controls; and (4) differentiating products that have attenuated fluoride activity. RESULTS: This cross-validation study confirmed the ability of the three independent laboratories to discriminate between various concentrations of fluoride-containing dentifrice formulations, demonstrated that clinically proven formulas perform as expected and identified an attenuated fluoride formulation (NaF/CaCO3 dentifrice - 1100 ppm NaF) as inferior compared to the 1100 ppm F (NaF/silica) positive control.

Anticaries potential of a stabilized stannous-containing sodium fluoride dentifrice.

PURPOSE: To evaluate the anticaries potential of a stabilized stannous-containing sodium fluoride dentifrice relative to appropriate control products. METHODS: A series of in vitro studies was conducted using the following standard anticaries efficacy measures: (1) fluoride uptake; (2) pH cycling remineralization/inhibition of demineralization; and (3) surface microhardness. In each study, the stannous-containing sodium fluoride test dentifrice (1450 ppm F) was compared to a negative control dentifrice (0 ppm F) and a positive control fluoride dentifrice (either 1100 ppm F or 1450 ppm F). RESULTS: Fluoride uptake: The mean fluoride uptake from both the test dentifrice and the positive control dentifrice was significantly greater than the negative control. There was no statistically significant difference between the two fluoride dentifrices, although the test dentifrice was directionally higher. pH cycling: The remineralization measured with the test dentifrice was directionally higher though not significantly different from the positive control dentifrice. Remineralization by both fluoride-containing dentifrices was significantly greater versus the negative control. Surface microhardness: The percent increase in surface microhardness measured on enamel surfaces after treatments with the test dentifrice was found to be significantly higher than that measured for the positive control and the negative control.

Protection From Dental Erosion: All Fluorides are Not Equal.

All fluoride sources help strengthen teeth against bacterial acids that cause caries. However, excessive exposure to dietary acids, which can result in dental erosion, presents a more aggressive level of challenge compared to caries. Despite the fact that almost all toothpastes contain fluoride, both the incidence and prevalence of dental erosion appear to be on the rise. This article: (1) describes key differences between caries and dental erosion and the ability of different fluoride sources to help prevent erosion; (2) discusses the importance of the evaluation of patients for dental erosion at the earliest stages using the Basic Erosive Wear Examination scoring system to help assess and educate patients; and (3) provides evidence-based information for making specific recommendations to patients with dental erosion. The objective of this article is to assess the comparative ability of fluoride agents to protect against dental erosion. Though all fluorides are able to help strengthen teeth against cariogenic acids, not all available sources of fluoride provide the same level of erosion protection. Daily use of a stabilized stannous fluoride dentifrice has been shown to provide the most effective means of protecting teeth against the increasing risk of dental erosion and erosive tooth wear.

Anticaries potential of commercial dentifrices as determined by fluoridation and remineralization efficiency.

AIM: The aim of this in vitro study was to investigate fluoride uptake in human enamel after use of commercially available toothpastes containing different fluoride compounds, or combinations of fluoride actives formulated into a single product, as a means of determining the efficiency of each formula for delivering caries preventing fluoride to demineralized (caries active) enamel. METHODS AND MATERIALS: Four test dentifrices and two controls were assessed and placed in groups as follows: Group 1: Lacer (Spain); Group 2: Positive control-USP Reference Standard 1100 ppm F; Group 3: Fluocaril Bi-Fluoré 250 (France); Group 4: Colgate Fluor Active (Denmark); Group 5: Elmex (France); and Group 6: A placebo (formulated the same as the USP Reference Standard toothpaste with the exception that it contained < 1 ppm F). Cores 3 mm in diameter were removed from erupted human enamel specimens (extracted by local oral surgeons for orthodontic reasons) and stored in 1% Thymol solution prior to use. They were ground and polished to remove the natural fluoride rich enamel layer, then exposed to a demineralization solution, and assessed for surface microhardness to enable randomization for use in the study. Each group of five specimens underwent a daily pH cycling procedure that involved exposure to pooled human saliva (refreshed three times daily). The groups were then exposed to dentifrice slurries four times daily for one minute per exposure and to a demineralization solution for three hours. The cycling procedure was repeated for five days. Specimens were again analyzed for surface microhardness and fluoride uptake upon completion of five days of treatment. RESULTS: Average surface hardness: Groups 2 and 3 showed a statistically significant greater (p<0.05) change indicating greater remineralization compared to all other groups. The average change was 23.45 for Group 2 and 22.65 for Group 3. All other groups had changes ranging from 4.25-8.62. No other statistically significant differences were observed between groups. Fluoride uptake results: Groups 2 and 3 showed statistically significantly greater fluoride uptake versus all other groups (p<0.05). Groups 1 and 5 were significantly different from Group 6. No other statistically significant differences were observed for either analysis. CONCLUSIONS: Of the marketed products included in the study, the Fluocaril Bi-Fluoré 250 product formulation provided both the highest level of fluoride uptake and mineralization to the demineralized enamel. The clinical significance of these in vitro results is the confirmation Fluocaril Bi-Fluoré 250 is effective at remineralizing enamel caries lesions.