Dual phase stannous oral compositions

Details Dual phase stannous oral compositions Dual phase stannous oral compositions

2000-11-10

2003-02-18

Rose, Shep K. (Department: 1614)

Drug, bio-affecting and body treating compositions

Dentifrices

Fluorine or fluorine compound containing

C424S049000

Reexamination Certificate

active

06521216

ABSTRACT:

TECHNICAL FIELD
The present invention relates to improved dual phase oral compositions containing stannous salts, such as stannous fluoride. These improved compositions provide a spectrum of intraoral benefits derived from stannous fluoride and/or other stannous salt, including antimicrobial effects, control of breath malodor, control of dental plaque growth and metabolism, reduced gingivitis, decreased progression to periodontal disease, reductions in dentinal hypersensitivity and reduced coronal and root dental caries. The improved stannous containing compositions provide high efficacy by having the stannous stabilized in a separate phase from the rest of the composition. The stannous is stabilized without increasing the negative aesthetics associated with stannous and ingredients commonly used to stabilize stannous. This improvement results in a more aesthetically pleasing, particularly less astringent, oral composition compared to other oral composition with the same efficacy.
BACKGROUND OF THE INVENTION
Stannous fluoride is commonly known for its efficacy when formulated into oral products. Stannous fluoride was the first fluoride source incorporated into toothpastes for therapeutic efficacy in the control of dental caries. Stannous fluoride gels, rinses, and dentifrices have since been shown to provide clinical efficacy for the reduction of dental caries, dentinal hypersensitivity, dental plaque and gingivitis. In addition to these clinical effects, formulations containing stannous fluoride may also help to provide improved breath benefits through chemical and antibacterial actions. Stannous fluoride formulations typically include stabilization systems designed to maintain bioavailable (i.e., soluble and active) levels of stannous during shelf storage, accounting for loss of stannous to oxidation, hydrolysis or precipitation. Therefore, stannous fluoride formulations may contain other additional stannous containing ingredients, which may provide important stabilization benefits for efficacy. High concentrations of stannous in dental formulations helps to ensure stability of stannous fluoride and therefore clinical efficacy of formulations containing the latter. Unfortunately, although stannous fluoride compositions are known to be highly effective, successful commercial utilization is complicated by complexity in the development of formulations providing adequate stannous fluoride stability and in the side effects of stannous. Formulations providing increased or improved efficacy typically promote increased side effects. This limits clinical and commercial applications.
A negative side effect routinely encountered during use of effective stannous fluoride formulations is unacceptable formulation astringency. Astringents are locally applied protein precipitants that have low cell permeability, thus restricting actions to cell surfaces and interstitial spaces. Strong astringents can induce contraction and wrinkling of the tissues and mucous secretions can be precipitated or reduced. Within oral products, these chemical actions produce an unpleasant ‘drying’ sensation in the oral cavity, such as on the tongue, gingival tissues or buccal epithelia. Stannous formulations containing sufficient stannous for bioavailability are routinely described as astringent by patients and consumers and this property is undesirable. The astringency is most noticeable after use of the product. Astringency is caused by stannous and by ingredients commonly used to help stabilize stannous, such as citrate and gluconate. Another commonly found side effect from the regular use of stannous fluoride is cosmetic yellow-brown tooth staining. This stain is derived from pellicle, plaque and dietary component reactions with available stannous deposited on tooth surfaces during treatment with effective stannous fluoride formulations.
Previous attempts to develop effective and consumer acceptable stannous fluoride oral compositions have attempted to solve these cumulative detriments, however none have been fully successful for a dual phase stannous composition. This is because the concentration of stannous in one of the phases is typically twice as high as compared to single phase oral compositions. U.S. Pat. No. 5,004,597, issued to Majeti et al., discloses oral compositions containing stannous fluoride and gluconate salts. The inclusion of gluconate results in improved formulation efficacy and stability. While effective at lower levels of stannous ion concentration, the present inventors have found this method of stabilization is not as effective at higher levels of stannous, which is required in the phase containing stannous in a dual phase oral composition. In Majeti et al., to stabilize the stannous at higher levels, it is suggested that high levels of gluconate be used. Although this is acceptable for stability, the product aesthetics from the high level of gluconate are significantly reduced resulting in a highly astringent product.
U.S. Pat. No. 5,578,293, issued to Prencipe et al., discloses the use of an organic acid compound to stabilize the stannous ion concentration. Coupled with the stannous fluoride and citrate as the organic acid, the formulations also include soluble pyrophosphate salts. In the Prencipe et al. patent, all examples include sufficient amount of either citric acid and/or sodium citrate dihydrate to stabilize the stannous ions and include soluble pyrophosphate to prevent precipitation. The level of citrate needed to effectively stabilize the stannous ion against hydrolysis and precipitation significantly detracts from the aesthetics of the stannous composition. The composition will be salty, sour, and the stannous bound to citrate will still act as an astringent, which reduces the overall taste acceptability. Likewise, U.S. Pat. No. 5,213,790, issued to Lukacovic et al., also discloses the use of a citrate ion source in a stannous composition. In U.S. Pat. No. 5,780,015, issued to Fisher et al., the use of dual phase dentifrice containing a potassium salt and a stannous salt wherein hydrogenated castor oil is used to help reduce astringency. The stannous salt is stabilized through the use of an organic acid compound as described in Prencipe et al.
Another attempt to produce efficacious stannous composition is described in U.S. Pat. No. 5,716,600, issued to Zhrandik et al. This patent discloses low water formulations which help to prevent the stannous fluoride from degradation over time. No attempts are made to reduce the astringency or staining of the formulation.
U.S. Pat. No. 5,017,363, issued to Suhonen, discloses a stannous ion chelating copolymer of an alkyl vinyl ether and maleic anhydride or acid in an amount to effectively stabilize stannous ions. Suhonen also discloses that the compositions are substantially free from silica, soluble phosphates such as soluble pyrophosphates (e.g., tetrasodium pyrophosphate and tetrapotassium pyrophosphate), and aldehyde group containing compounds, since the stabilizing function of the stannous ion chelating polymer is not effective in the presence of these ingredients.
U.S. Pat. No. 5,338,537, issued to White, Jr. et al., discloses the use of a low molecular weight diphosphonic acid, which is used as a binding agent for stannous to help reduce the tendency of staining from the composition. While effective in reducing staining potential, laboratory studies have demonstrated that the antibacterial activity of formulations containing stannous complexed with the low molecular weight diphosphonic acid is very low. Similar results are obtained on formulation with soluble pyrophosphate salts, in the absence of strong citrate chelation, as described above.
Commonly marketed today are dual phase dentifrices. The dual phase enables ingredients that are not compatible to be separated and formulated into separate phases. For stannous containing compositions, this is desirable so that ingredients not stable with stannous can be used in a separate phase. However, to still achieve high therapeutic benefits from the stannous, the vast majority of t

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