Stannous Fluoride Toothpaste Benefit: Dental Caries

Dental caries is endemic globally (Beaglehole et al. 2009). The prevalence of dental caries in the general population is significant throughout the world and particularly affects people in regions where consumption of refined sugar is high. Figure 4 shows caries prevalence for the 6–19 year-old age group in a number of countries (Beaglehole 2009).

Cariogenic bacteria in supragingival dental plaque, predominantly Mutans streptococci and Lactobacilli, metabolize fermentable carbohydrates to produce acids that cause demineralization of the dental hard tissues. Without adequate remineralization the caries balance is disturbed, resulting in net mineral loss that will eventually lead to cavitation. Fluoride is the most frequently used chemotherapeutic agent to combat dental caries.

Mechanisms of action of fluorides

Twice daily use of fluoride dentifrices is well-established as being effective in reducing caries and reversing early carious lesions (Marinho et al. 2003) Interventions that increase the amount of fluoride available to alter the plaque/tooth surface interaction are the most successful for caries prevention:

• Mechanical removal of plaque

• Anti-bacterial control of plaque

• Suppression of the host (human) inflammatory response

Higher concentrations of fluoride generally offer greater protection:

• 2,800 ppm sodium fluoride dentifrice has demonstrated 20.4% greater caries reduction compared to a regular 1,100 ppm sodium fluoride dentifrice (Biesbrock et al. 2001)

• 2,500 ppm sodium monofluorophosphate dentifrice has demonstrated a 16–20% greater reduction in caries (DMFS) compared to 1,000 ppm (Stephen et al. 1988)

Mechanism of action of stannous fluoride

The caries demineralization-remineralization balance described above is valid for all fluoride compounds which allow dissociation of the fluoride ion in the oral cavity. Stabilized stannous fluoride may offer additional anti-caries benefits through the anti-bacterial actions of stannous which reduce the production of plaque acids (Kasturi et al. 1995).

The following study summaries represent a sample of research demonstrating the benefits of stabilized stannous fluoride dentifrice for caries protection.

Full text available in the Research Database at www.dentalcare.com

Reference: Pfarrer AM, McQueen CM, Lawless MA, Rapozo-Hilo M, Featherstone JDB. Compend Contin Educ Dent. 2005;26(Suppl1):41-46.

Conclusion

In vitro studies demonstrated the anticaries potential of the stabilized stannous fluoride dentifrice.

Objective

To examine the anticaries potential of a stabilized stannous fluoride dentifrice with sodium hexametaphosphate (for cosmetic benefits).

Materials And Methods

In vitro anti-caries profile methods were:

• Fluoride uptake into demineralized enamel: single-treatment, mechanism-of-action study.

• Remineralization/inhibition of demineralization: multiple-treatment study under lesion progression pH-cycling conditions. Dentifrices compared in the respective profile methods were:

• Fluoride uptake

  • Stabilized stannous fluoride with sodium hexametaphosphate (1,100 pmm fluoride as stannous fluoride, sodium hexametaphosphate, and silica)

  • United States Pharmacopeia (USP) Reference Standard (1,100 pmm fluoride as stannous fluoride and silica)

  • Dose-response control USP Reference Standard (diluted to 250 ppm fluoride as stannous fluoride and silica)

  • Placebo negative control (<1ppm fluoride and silica)

• Remineralization/inhibition of demineralization

  • Stabilized stannous fluoride with sodium hexametaphosphate

  • Sodium fluoride with sodium hexametaphosphate (1,100 pmm fluoride as sodium fluoride, sodium hexametaphosphate, and silica)

  • Stannous fluoride USP Reference Standard (1,100 pmm fluoride as stannous fluoride and silica)

  • Sodium fluoride USP Reference Standard (1,100 ppm fluoride as sodium fluoride and silica)

  • Dose-response sodium fluoride control

  • Placebo negative control (<1ppm fluoride)

• Fluoride uptake

  Human enamel samples from extracted teeth – 3 mm diameter cores – were decalcified for 24 hours to produce early caries lesions 20-30 μm deep. Samples were taken from the cores by the microdrill biopsy technique. Samples were measured for fluoride levels pre-dentifrice treatment. Groups of specimens were treated with dentifrice/saliva slurries. Samples were taken to determine post-treatment fluoride levels. The difference between pre and post levels determined fluoride uptake.

• Remineralization/inhibition of demineralization

  Caries-free human molar or premolar crowns were each treated to produce a 3 x 2 mm window on one surface as the entry point for demineralization. 24-hour test cycles

  • 6 hours demineralization, 1 minute dentifrice treatment, 16 hours remineralization, 1 minute treatment – were repeated for 14 days. Cycles were designed to model normal demineralization and remineralization. The resulting lesions were measured for progression into the enamel, and mineral loss from each lesion calculated.

Results

• Fluoride uptake

  There was no statistically significant difference between the stannous fluoride with sodium hexametaphosphate toothpaste and the stannous fluoride USP Reference Standard toothpaste.

• Remineralization/inhibition of demineralization

  The stannous fluoride with sodium hexametaphosphate toothpaste was at least as good as the clinically proven stannous fluoride and sodium fluoride USP Reference Standard toothpastes.

Full text available in the Research Database at www.dentalcare.com

Reference: Stookey GK, Mau MS, Isaacs RL, Gonzalez-Gierbolini C, Bartizek RD, Biesbrock AR. Caries Res. 2004;38:542-550.

Conclusion

In a 2-year clinical trial, subjects in both the high-dose sodium fluoride dentifrice (2,800 ppm F) group and the 0.454% stabilized stannous fluoride dentifrice (SnF₂, 1,100 ppm F) group showed significantly fewer caries increments than subjects in the sodium fluoride positive control dentifrice group (1,100 ppm F). The low-NaF group (550 ppm F) and the positive control group did not differ.

Objective

To compare the anticaries effectiveness of a low-dose (500 ppm F) and high-dose (2,800 ppm F) sodium fluoride dentifrice (low-NaF and high Na-F) and an experimental dentifrice (SnF₂; 1,100 ppm F) with a sodium fluoride positive control dentifrice (1,100 ppm F) over 2 years. (Note: This was an early prototype of the eventual marketed stannous fluoride/sodium hexametaphosphate product.)

Materials And Methods

• The four dentifrices compared were as follows: an experimental dentifrice (0.454% SnF₂ and sodium hexametaphosphate for cosmetic benefits), low-NaF, high-NaF, positive control.

• Study subjects were 955 schoolchildren (~9-12 years) from an urban area in Puerto Rico.

• Subjects were randomly assigned to the four treatments and were supplied with their dentifrice and toothbrushes, which were replaced every 3 months. Their 1-minute toothbrushing was supervised twice a day by teachers in the classroom; brushing was ad libitum outside school hours.

• Caries were assessed by visual-tactile examinations (with aid of fiber-optic illumination and artificial light, mouth mirror, compressed air, dental explorer) as DMFS (decayed, missing, and filled surfaces) by two examiners and supplemented with a radiographic examination at baseline and after 12 and 24 months.

• Both examiners examined all subjects. Examiners were tested for the sensitivity and specificity of their examinations and repeatability of their results prior to the study.

Results

• 799 subjects completed the year 1 assessment; 683 subjects were re-examined at year 2.

• Considering evaluable subjects (i.e., those who attended at least 60% of the supervised brushing sessions over the 2-year study period):

  • Both examiners showed that caries increments were lower in the high-NaF group than the control group.

  • Both examiners showed statistically significantly less caries in the SnF₂ group than the positive control group.

  • Neither examiner showed statistically significant differences in caries increments between low-NaF and positive control groups.

Reference: Wefel JS, Stanford CM, Ament DK, Hogan MM, Harless JD, Pfarrer AM, Ramsey LL, Leusch MS, Biesbrock AR. Caries Res. 2002;36(2):122-8.

Conclusion

Based on this research, sodium hexametaphosphate does not interfere with the normal fluoride activity of the toothpastes tested. Relative to the positive and negative controls, the experimental dentifrice with stannous fluoride was numerically better at inhibiting demineralization of sound root surfaces.

Objective

An investigator-blinded, in situ clinical study was conducted to evaluate the effects of two experimental dentifrice formulations containing sodium hexametaphosphate, an anticalculus/whitening agent, on demineralization/remineralization.

Materials And Methods

Experimental dentifrices were:

• Stannous fluoride (SnF₂) with sodium hexametaphosphate (Note: This was an early prototype of the eventual marketed stannous fluoride/sodium hexametaphosphate product.)

• Sodium fluoride (NaF) and sodium hexametaphosphate

Both experimental dentifrices were packaged in a dual-phase tube

Three controls were used to evaluate the experimental dentifrice formulations’ ability to alter demineralization-remineralization:

• SnF₂-positive control

• NaF-positive control

• No fluoride placebo-negative control

The single-section crown model, developed at the University of Iowa, was used to evaluate the fluoride efficacy of the treatments.

1. a sound root section;

2. a root surface lesion section; and

3. enamel surface lesion section.

Thirty subjects were randomized to one of 10 treatment sequences involving 5 dentifrice treatments. Each dentifrice was used twice per day for 1 month over the 5-month period. At the end of each leg, the gold crown was removed and replaced by a new crown with three new substrates.

Results

Results suggested a clinical level of anticaries activity for the experimental SnF₂ and NaF dentifrice formulations that was as good as either of the positive controls, when evaluated using polarized light microscopy.

• Based on pairwise comparisons (P<0.05)

See publication for additional results.

• Stabilized stannous fluoride dentifrice provides effective caries management as part of a multi-benefit dentifrice.
• Research shows an early dual-phase prototype of the stannous fluoride formula with sodium hexametaphosphate provided a similar level of protection compared to a prescription strength (2,800 ppm F) dentifrice in a two-year clinical trial.