Mechanism of action

The stain prevention and whitening effects of many stabilized stannous fluoride formulations in Procter & Gamble’s portfolio are provided by an advanced, high cleaning silica system and sodium hexametaphosphate (polyphosphate). The high cleaning silica gently removes stain mechanically during brushing, while the sodium hexametaphosphate works chemically. The sodium hexametaphosphate provides for excellent stain removal and prevention (Baig et al. 2005; Terezhalmy et al. 2007):

• Sodium hexametaphosphate has a strong affinity for and attraction to the tooth surface and the pellicle film at the tooth surface to which surface stain is attached.

- The sodium hexametaphosphate molecule is negatively charged while the calcium ions in the pellicle and enamel are positively charged. Since opposites attract, the polyphosphate is strongly attracted to these calcium sites.

• The sodium hexametaphosphate adsorbs to the pellicle, disrupting it.

- As a result of disruption of the pellicle, the stain that was attached to and trapped in it becomes displaced, released and lifted away from the tooth surface.

• Thirdly, the retention of sodium hexametaphosphate at the tooth surface and in the tooth pellicle prevents new stain from binding and accumulating at the tooth surface. (Figure 24)

The 2-step stabilized stannous fluoride formula contains hydrogen peroxide in the second step to provide whitening by disruption of carbon bonds. Stain is composed of materials containing carbon bonds that reflect back only the wavelengths of light that appear colored. Hydrogen peroxide breaks the carbon bonds, so the stain then reflects back more wavelengths of light, making the stain appear white (Goldstein & Garber, 1995). The smooth texture stabilized stannous fluoride formula uses a combination of silica and zinc citrate for stain prevention. The silica gently removes surface stains while the zinc citrate indirectly protects against stains by preventing calcification of plaque into tartar, thereby reducing the surface area that can attract stains.

The following study summaries represent a sample of research demonstrating the anti-stain and extrinsic whitening benefits of stabilized stannous fluoride dentifrice.

EXTRINSIC STAIN REMOVAL EFFICACY OF A STANNOUS FLUORIDE DENTIFRICE WITH SODIUM HEXAMETAPHOSPHATE

Reference: He T, Baker R, Bartizek RD, et al. J Clin Dent. 2007;18(1):7-11.

OBJECTIVE

To compare stain removal of a dentifrice containing stabilized stannous fluoride and sodium hexametaphosphate to a positive control dentifrice in 2 independent, double-blind, randomized 6-week trials.

The following dentifrices were tested in each study:

• Crest^® PRO-HEALTH^™ (0.454% stabilized stannous fluoride + sodium hexametaphosphate).
• Positive control dentifrice (Colgate Total Plus Whitening with sodium fluoride).

MATERIALS AND METHODS

• Both studies followed the same protocol.
• Study subjects were healthy adults with visible extrinsic tooth stain.
• The modified Lobene Stain Index was used to measure stain on the facial surfaces of the 8 central and lateral incisors at baseline.
• Oral soft and hard tissue examinations were also conducted.
• Subjects were randomized to either the stabilized stannous fluoride + sodium hexametaphosphate toothpaste or positive control toothpaste.
• Subjects used their assigned dentifrice twice a day for 6 weeks.
• Patients were examined again for stain and safety at weeks 3 and 6.

EXTRINSIC STAIN REMOVAL EFFICACY OF A STABILIZED STANNOUS FLUORIDE DENTIFRICEL

Reference: L Friesen, T He, R. Eusebio. J Dent Res 2017; 96 (Spec Iss A): Abstract 1941.

KEY CLINICAL FINDINGS

• After 2 week of use, the experimental stabilized stannous fluoride (SnF₂) group demonstrated significantly less Interproximal Modified Lobene (IML) stain overall (see Figure) and interproximal surface stain than the positive control dentifrice group (P<0.0012).
• Both groups showed statistically significant reductions in IML stain scores at Week 2 (P<0.0001) relative to Baseline. The median percent change reductions were 57% for the positive control and 70% for the SnF₂ dentifrice.

OBJECTIVE

To assess the extrinsic stain removal benefit delivered by a SnF₂ dentifrice and a positive control dentifrice over a two-week period.

METHODS

• This study utilized a randomized, two-week, double-blind, parallel group design.
• At Baseline, an IML examination^‡ was performed on the facial surfaces of the twelve anterior teeth. The two teeth with the highest IML composite scores were selected as the test teeth.
• Subjects were stratified on stain scores of the test teeth, and gender, and randomized to one of two treatment groups:

- Experimental 0.454% stabilized stannous fluoride dentifrice (Crest^® PRO-HEALTH^™ Clean Mint [Smooth Formula], Procter & Gamble); or

- 0.243% sodium fluoride/0.3% triclosan positive control whitening dentifrice (Colgate^® Total^® Whitening, Colgate-Palmolive).

• Subjects were instructed to use their respective test product following the manufacturer’s instructions at home over the two week study duration.
• Tooth color was reassessed at Week Two.
• Baseline to post-treatment change in stain score was tested using paired t-tests. Analysis of covariance (ANCOVA) with treatment as a factor and Baseline Lobene score as the covariate was used to assess treatment differences post-treatment. All comparisons were two-sided using a 5% level of significance.

‡ Friesen L, et al. Am J Dent 2016; 29:20-24.
§ Baig A and He T. Compend Contin Educ Dent. 2005;26 (Suppl 1): 4-11.

CLINICAL SIGNIFICANCE: STAINS