Field of the Invention

The invention relates to denture adhesives, their use and methods for making denture adhesives.

Background of the Invention

Dentures are substitutes for missing teeth and serve as replacement for all or some of the teeth found in the oral cavity. Despite diligent efforts by dental professionals and designers of dental prostheses, dentures do not always fit perfectly. Over time, even well-fitting dentures can become ill-fitting due to natural shrinkage and changes in the gum or mucous tissues. Therefore, adherent creams, liquids or powders are often used to secure or temporarily fix dentures within the mouth.

Denture adhesive compositions, (also known as fixative compositions and stabilizer compositions), are used to fill the interstices between the dentures and the gums or tissues. Prior to placement of the denture in the oral cavity, a denture adhesive or fixative is applied to the denture plate surface, which for a perfect fit, should uniformly contact the gums and oral tissues. Denture adhesive compositions are formulated not only for their adherent properties, but also to provide an interface between the denture and the gums and/or oral tissues, thereby positioning the denture securely in the oral cavity.

There are a number of desirable attributes of a denture adhesive composition. The denture adhesive should develop a high degree of tack upon contact with saliva, generating a tacky, uniform and viscous mucilage, so that the dentures can be held in place as soon as they are seated in the mouth. It is also highly desirable that the mucilage of the adhesive be spread over the denture-mucosa interface in order to seal the denture in place effectively. The mucilage should possess sufficient cohesive strength to withstand the stresses of mastication, which act to rupture the seal and thus dislodge the denture. The denture adhesive must also exhibit sufficient resistance to degradation under the extreme environmental changes that can occur in the oral cavity during such common actions as drinking hot or cold beverages. Of course, the adhesive must also be releasable so that the denture wearer may remove the dentures for cleaning and maintenance. Denture adhesives are generally sold as a cream, liner or strip, liquid or powder, and many examples are well known in the art.

Early denture adhesives contained finely ground particles of natural gums that expanded when wet with water to become a viscous gel, which acted as a cushion and an adherent between the denture plate and the gum tissue. These denture adhesives, however, have been largely supplanted by polymeric denture adhesives in recent years. One preferred polymer from the field is a mixed partial salt of a copolymer of maleic acid and alkyl vinyl ether, sold under the GANT EZ ^® trade name. This class of polymers was described as a possible denture adhesive in Germann, et al. U.S. Patent No. 3,003,988, which issued more than 30 years ago. This polymer is chemically modified and/or combined with a number of other ingredients to form the final denture adhesive.

Due to the popularity of maleic acid and alkyl vinyl ether denture adhesives there has been little investigation into alternatives, particularly those that offer a more affordable composition. US 4,542,168 (Block Drug Co) describes a denture fixative composition containing a partially neutralised and crosslinked polyacrylic acid and at least one hydrophilic polymer. The polyacrylic acid is a carboxypolymethylene or carboxyvinyl polymer of high molecular weight. The denture adhesive compositions are said to develop a high degree of tack and uniform viscous mucilages of high cohesive strength when spread over the denture-mucosa interface.

EP1166744 Al (Healthtech Corp) discloses a denture adhesive having superior cleanability which can be easily removed from a denture base. The adhesives contain a water-soluble polymer, calcium sulphate and an alginate. The presence of the alginate and calcium produce a gel which adheres the denture to the mucosa surface but also allows for easy removal of the denture.

The Applicants have surprisingly found that denture adhesives comprising at least one hydrophilic adhesive polymer, and a source of metal cations are useful alternative compositions that do not need to contain either an alginate, polyacrylic acid and/or an alkyl vinyl ether-maleic acid anhydride copolymer. These compositions show a long duration of hold but also use more widely available and affordable ingredients. The denture adhesives of the present invention exhibit sufficient tack upon initial contact with oral mucosa, build up cohesive strength quickly when hydrated with moisture or saliva and are able to resist stresses such as those that occur upon mastication. Summary of the Invention

In one aspect, the invention relates to a denture adhesive powder composition, comprising:

(a) a hydrophilic adhesive polymer, which is at least a combination of a cellulosic polymer and a gum; and

(b) a source of metal cations;

wherein the composition does not contain an alginate or polyacrylic acid or an alkyl vinyl ether- maleic acid anhydride copolymer.

In one aspect, the invention relates to a denture adhesive cream composition, comprising:

(a) a hydrophilic adhesive polymer, which is at least a combination of a cellulosic polymer and a gum; and

(b) a source of metal cations; and

(c) a wax which is petrolatum;

wherein the composition does not contain an alginate or polyacrylic acid or an alkyl vinyl ether- maleic acid anhydride copolymer.

In another aspect, the invention further provides a method for making the denture adhesive compositions. In another aspect, the invention relates to a method for adhering a denture to the oral mucosa resulting from the use of the denture adhesive compositions.

Description of the drawings While the specification concludes with claims particularly pointing out and distinctly claiming the invention, it is believed that the present invention will be better understood from the following description taken in conjunction with the accompanying drawings in which: Figure 1 (fig 1): Is a chart of hang time comparing the cream adhesive compositions of the present invention.

Figure 2 (fig 2): Is a chart of shear strength comparing the cream adhesive compositions of the present invention.

Figure 3 (fig 3): Is a graph of adhesion profile data comparing the cream adhesive compositions of the present invention.

Figure 4 (fig 4): Is a chart of hang time comparing the powder adhesive compositions of the present invention.

Figure 5 (fig 5): Is a chart of shear strength comparing the powder adhesive compositions of the present invention. Figure 6 (fig 6): Is a graph of adhesion profile data comparing the powder adhesive compositions of the present invention.

Detailed description of the Invention In one aspect, the invention relates to a denture adhesive powder composition, comprising:

(a) a hydrophilic adhesive polymer which is at least a combination of a cellulosic polymer and a gum; and

(b) a source of metal cations;

wherein the composition does not contain an alginate or polyacrylic acid or an alkyl vinyl ether- maleic acid anhydride copolymer.

In one aspect, the invention relates to a denture adhesive cream composition, comprising:

(a) a hydrophilic adhesive polymer which is at least a combination of a cellulosic polymer and a gum and

(b) a source of metal cations; and

(c) a wax which is petrolatum;

wherein the composition does not contain an alginate or polyacrylic acid or an alkyl vinyl ether- maleic acid anhydride copolymer. In another aspect of the invention, the hydrophilic adhesive polymer is a cellulosic polymer. In another aspect of the invention, the hydrophilic adhesive polymer is a gum. In one aspect of the invention, the hydrophilic adhesive polymer is a combination of a cellulosic polymer and a gum.

In one aspect of the invention, the hydrophilic adhesive polymer is a combination of two gums and a cellulosic polymer.

In one aspect of the invention, the hydrophilic adhesive polymer is a combination of two cellulosic polymers and a gum. In one aspect of the invention, the hydrophilic adhesive polymer is a combination of at least a cellulosic polymer, a gum and polyethylene oxide.

In one aspect of the invention, the hydrophilic adhesive polymer is a combination of two cellulosic polymers and two gums.

Cellulosic polymers that are suitable for use in the denture adhesive compositions of the present invention include, but are not limited to, sodium carboxymethyl cellulose, hydroxypropyl methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethyl cellulose hydroxyethylmethylcellulose, methyl-cellulose, methylcarboxymethyl cellulose,

hydroxyethylcarboxymethyl cellulose, hydroxyethylmethylcarboxy methylcellulose,

sulfoethylcarboxymethyl cellulose, hydroxyethylhydroxypropyl cellulose, hydroxyethylethyl cellulose, or hydroxyethylsulfoethyl cellulose or a combination thereof.

In one aspect the cellulosic polymer is sodium carboxymethyl cellulose or hydroxypropyl methylcellulose, or a combination thereof. In another aspect the cellulosic polymer is sodium carboxymethyl cellulose. In another aspect the cellulosic polymer is hydroxypropyl methylcellulose. In another aspect the cellulosic polymer is a combination of sodium carboxymethyl cellulose and hydroxypropyl methylcellulose. Gums that are suitable for use in the denture adhesive compositions of the present invention include, but are not limited to, xanthan gum, locust bean gum, konjac gum, guar gum and its derivatives, fenugreek gum and dietary fibres, pectin and its derivatives, chitosan and its derivatives, carrageenan and its derivatives, or karaya gum or a combination thereof. In one aspect the gum is xanthan gum, locust bean gum, konjac gum or a combination thereof. In another aspect the gum is xanthan gum. In another aspect the gum is locust bean gum. In another aspect the gum is konjac gum. In another aspect the gum is a combination of xanthan gum and locust bean gum. In another aspect the gum is a combination of xanthan gum and konjac gum. Polyols that are suitable for use in the denture adhesive compositions of the present invention include, but are not limited to, polyethylene oxide homopolymers or copolymers such as, but not limited to, polyethylene glycol and its derivatives, polyethylene oxide (Polyox ^® ) and the like or a combination thereof. In one aspect of the invention, the hydrophilic adhesive polymer is polyethylene oxide. In one aspect of the invention, the hydrophilic adhesive polymer is present in the denture adhesive composition in a total amount of about 10% to about 90%. In another aspect of the invention, the hydrophilic adhesive polymer is present in the denture adhesive composition in a total amount of about 20% to about 85% by weight. In another aspect of the invention, the hydrophilic adhesive polymer is present in the denture adhesive composition in a total amount of about 35% to about 85% by weight.

In another aspect of the invention, the hydrophilic adhesive polymer is present in the denture adhesive composition in a total amount of about 30% to about 60% by weight. In another aspect of the invention, the hydrophilic adhesive polymer is present in the denture adhesive composition in a total amount of about 40% to about 50% by weight.

In another aspect of the invention, the hydrophilic adhesive polymer is present in the denture adhesive composition in a total amount of about 50% to about 90% by weight. In another aspect of the invention, the hydrophilic adhesive polymer is present in the denture adhesive composition in a total amount of about 60% to about 80% by weight.

The "source of metal cations" that are suitable for use in the denture adhesive compositions of the present invention include, but are not limited to a source of zinc, calcium, magnesium, potassium, sodium or strontium ions, or a combination thereof.

The "source of metal cations" acts as a cross-linking agent forming a bond between the hydrophilic adhesive polymer chains. In one aspect of the invention, the source of metal ions is a source of calcium ions. In another aspect of the invention, the source of metal ions is a source of strontium ions. In another aspect of the invention, source of metal ions is a combination of a source of calcium ions and a source of strontium ions. A suitable source of calcium ions is a calcium salt, such as calcium chloride (anhydrous or dihydrate) or a calcium phosphate, e.g. dicalcium phosphate dihydrate.

A suitable source of strontium ions is a strontium salt, such as strontium chloride. In one aspect of the invention, the source of metal cations is present in the compositions of the present invention in an amount to provide from about 0.5% to about 10% of metal cations.

In another aspect of the invention, the source of metal cations is present in the compositions of the present invention in an amount to provide from about 1% to about 10% of metal cations. In another aspect of the invention, the source of metal cations is present in the compositions of the present invention in an amount to provide from about 3% to about 8% of metal cations.

In another aspect of the invention, the source of metal cations is present in the compositions of the present invention in an amount to provide from about 0.5% to about 5% of metal cations. In another aspect of the invention, the source of metal cations is present in the compositions of the present invention in an amount to provide from about 1% to about 2% of metal cations.

Each of the aspects of the invention are independent unless stated otherwise. Nevertheless the skilled person will understand that all the permutations of the aspects described are within the scope of the invention. Thus it is to be understood that the present invention covers all

combinations of suitable, convenient and exemplified groups described herein.

Denture adhesive compositions of the present invention may be used to secure full or partial dentures.

In addition to the foregoing materials, the denture adhesive compositions may be formulated with additional components well known in the denture adhesive art including, but not limited to, waxes, oils, preservatives, anti-caking agents, fluoride ions, deodourising agents, anti-bacterial agents, humectants, flavouring agents, colorants, sweetening agents, viscosity modifiers, and so forth.

The waxes useful in the invention include, but are not limited to, both natural and synthetic waxes and include without limitation animal waxes such as beeswax, lanolin and shellac wax, vegetable waxes such as carnauba, candelilla and bayberry wax, mineral wax such as petroleum waxes including paraffin, and microcrystalline wax. In one aspect, the wax is petrolatum. In one aspect, the wax is petrolatum blend W-180. In one aspect, the denture adhesive composition comprises from about 13% to about 30% by weight of wax. In one aspect, the denture adhesive composition comprises from about 20% to about 40% by weight of wax. In one aspect, the denture adhesive composition comprises from about 20% to about 40% by weight of petrolatum.

The oils useful in the invention include, but are not limited to, mineral oil, vegetable oil such as corn, soybean, cottonseed, castor, palm and coconut oils and animal oil such as fish oil, and oleic acid. In one aspect, the oil is mineral oil. In one aspect the denture adhesive composition comprises from about 0% to about 50% by weight of oil. In another aspect the denture adhesive composition comprises from about 10% to about 25% by weight of oil.

Preservatives which may be used in the denture adhesive compositions of the invention include, but are not limited to, those known antimicrobial agents conventionally employed in the art, such as benzoic acid and sodium benzoate, the parabens, sorbic acid and sorbates, propionic acid and propionates, acetic acid and acetates, nitrates and nitrites, sulfur dioxide and sulphites, antibiotics, diethyl pyrocarbonate, epoxides, hydrogen peroxide, and phosphates. The parabens include the methyl, ethyl, propyl, and butyl esters of parahydroxybenzoic acid. In one aspect, a single preservative may be used. In another aspect, a combination of one or more preservatives may be used. In another aspect, the preservative is methyl paraben. In another aspect, the preservative is propyl paraben. In another aspect, the denture adhesive composition comprises a combination of methyl paraben and propyl paraben as the preservatives. In another aspect, the denture adhesive composition comprises from about 0.03% to about 0.25% by weight of the preservative. Anti-caking agents which may be used in the denture adhesive compositions of the invention include, but are not limited to, silica, magnesium stearate and talc. In one aspect of the invention, the denture adhesive composition comprises talc. The humectants which may be used in the denture adhesive compositions of the invention include, but are not limited to, polyethylene glycol, propylene glycol and the like or a combination thereof.

Flavouring agents well known to the denture adhesive art may be added to the compositions of the present invention. These flavouring agents include, but are not limited to, synthetic flavour oils and/or oils derived from plants, leaves, flowers, fruits and so forth, or a combination thereof.

Representative flavour oils include spearmint oil, cinnamon oil, oil of wintergreen (methylsalicylate) and peppermint oils. Also useful are artificial, natural or synthetic fruit flavours such as citrus oil including lemon, orange, grape, lime, and grapefruit, and fruit essences including apple, strawberry, cherry, pineapple, and so forth. The flavouring agent may be a liquid, spray dried, encapsulated, or absorbed on a carrier, and mixtures thereof. In one aspect, the flavouring agent is peppermint oil. In another aspect, the flavouring agent is spray dried peppermint. In another aspect, the flavouring agent is spray dried spearmint. The amount of flavouring agent utilized varies depending on such factors as flavour type, adhesive composition and strength desired. In one aspect, the denture adhesive composition comprises from about 0.01% to about 3.0% by weight of the flavouring agent. In another aspect, the denture adhesive composition comprises from about 0.01% to about 2.0% by weight of the flavouring agent. In another aspect, the denture adhesive composition comprises from about 0.05% to 2% by weight of the flavouring agent.

The denture adhesive compositions may also include the use of sweeteners well known in the art. The sweetening agent may be selected from a wide range of materials including water-soluble agents, water-soluble artificial sweeteners, and dipeptide based sweeteners, including mixtures thereof. Representative sweeteners include, but are not limited to, (a) sugar alcohols such as sorbitol, xylitol, mannitol, maltitol, hydrogenated starch hydrolysate, and mixtures thereof; (b) water-soluble artificial sweeteners such as the soluble saccharin salts, i.e., sodium or calcium saccharin salts, cyclamate salts, Acesulfame-K, sucralose, and the like, and the free acid form of saccharin; and (c) dipeptide based sweeteners such as L-aspartyl-L-phenylalanine methyl ester, and the like. In one aspect, the denture adhesive composition comprises from about 0.001% to about 5 % by weight of the sweetening agent. The colourants useful in the present invention include the pigments such as titanium dioxide, and may also include dyes suitable for food, drug and cosmetic applications. These colourants are known as FD&C dyes. Illustrative examples include, but are not limited to, D&C Red#30 Aluminium Lake Paste, D&C Red #7 Calcium Lake Paste, Erythrosine Lake Paste, indigo dye, known as FD&C Blue No. 2, which is the disodium salt of 5,5 -indigotindi-sulfonic acid; FD&C Green No. 1, comprising a triphenylmethylene dye and is the monosodium salt of the 4-[4-N-ethyl-p-sulfobenzylamino) diphenylmethylene]-[l-(N-ethyl-N-P-sulfobenzyl)-2,5-cyclohex adienimine]. In one aspect, the colorant is FD&C Red No. 3. In another aspect, the denture adhesive composition comprises from about 0% to about 0.2% by weight of colourant. The viscosity modifiers useful herein include, but are not limited to, silica, quaternary ammonium compounds and similar agents, starches, gums, casein, gelatin and semi-synthetic cellulose.

All components of the denture adhesive composition are used in safe and adhesively effective amounts, which herein means an amount sufficient to provide adherence to the oral cavity.

The denture adhesive compositions may be in the form of a powder, a paste, a cream, or a strip. In one aspect, the denture adhesive composition is in the form of a paste. In another aspect, the denture adhesive composition is in the form of a cream. Means for preparing such compositions are well known in the denture adhesive art, employing conventional types of mixing equipment for blending, heating, and cooling solids and liquids. In one embodiment, mixing is performed at temperatures suitable to melt the components, e.g. petrolatum, to be blended.

In the powder form, the components are suitably admixed with flavouring agents and colorants, together with other ingredients such as non-toxic anti-caking agents (silica, magnesium stearate, talc and the like). The mixture of ingredients is thoroughly agitated or stirred to yield a completely homogenous intermixing of all components.

In the cream or paste composition, the components are suitably admixed with petrolatum along with the previously described waxes, oils, preservatives, flavouring agents, colorants, sweetening agents, viscosity modifiers, and so forth.

In the strip or layer form, the components are suitably mixed and then coated onto a non-adhesive self supporting coating layer by any conventional coating techniques, such as by spraying (if the material is liquid or slurry or dissolved or suspended in a liquid such as water) or by sifting (if the denture adhesive is in powder form). In one aspect, the components are admixed with the previously described waxes, oils, preservatives, flavouring agents, colorants, sweetening agents, viscosity modifiers, and so forth. The liner is then formed by any variety of techniques known in the polymer film-forming art, including casting, calendaring, coating, and extrusion. In one embodiment to form liners, the components are first mechanically softened by a ring roller; smoothed on a hydraulic press, and die-cut as desired into denture liner shapes or other desired shapes.

The following Examples further describe and demonstrate embodiments within the scope of the present invention. The Examples are given solely for the purpose of illustration and are not to be construed as limitations of the present invention. Many variations of these are possible without departing from the spirit and scope of the invention.

In these, as throughout the specification and claims, all parts and percentages (% by weight) is total weight of the composition and all temperatures in degrees centigrade, unless otherwise indicated.

EXAMPLES

All ingredients are commercially available. The invention is illustrated by the non-limiting Examples described below.

Example 1: Denture adhesive composition - Cream composition

Table 1

Procedure: The weighed quantity of xanthan gum and sodium CMC was sifted. The sifted material was loaded into a blender and mixed. Weighed calcium chloride anhydrous was dispersed into mineral oil (2/3rd quantity) under stirring and homogenized. Petrolatum blend w-180 was melted at a temperature of 70-80°C.The dispersion of calcium chloride and mineral oil was added to the molten mass of petrolatum blend w-180 under stirring followed by addition of the remaining l/3rd quantity of mineral oil. The polymer blend was added and the mixture was homogenized. The temperature was maintained at 60-70°C during the process. The cream thus prepared was allowed to cool to room temperature and then filled into laminated tubes.

Example 2: Denture adhesive composition - Cream composition

Table 2

Procedure: The weighed quantity of xanthan gum, locust bean gum and sodium CMC was sifted. The sifted material was loaded into a blender and mixed. Weighed calcium chloride dihydrate was dispersed into mineral oil (2/3rd quantity) under stirring and homogenized. Petrolatum blend w-180 was melted at a temperature of 70-80°C. The dispersion of calcium chloride and mineral oil was added to the molten mass of petrolatum blend w-180 under stirring followed by addition of the remaining l/3rd quantity of mineral oil. The polymer blend was added and the mixture was homogenized. The temperature was maintained at 60-70°C during the process. The cream thus prepared was allowed to cool to room temperature and then filled into laminated tubes.

Example 3: Denture adhesive composition - Cream composition

Table 3

Procedure: The weighed quantity of xanthan gum, konjac gum and sodium CMC was sifted. The sifted material was loaded into a blender and mixed. Weighed calcium chloride anhydrous was dispersed into mineral oil (2/3rd quantity) under stirring and homogenized. Petrolatum blend w-180 was melted at a temperature of 70-80°C. The dispersion of calcium chloride and mineral oil was added to the molten mass of petrolatum blend w-180 under stirring followed by addition of the remaining l/3rd quantity of mineral oil. The polymer blend was added and the mixture was homogenized. The temperature was maintained at 60-70°C during the process. The cream thus prepared was allowed to cool to room temperature and then filled into laminated tubes.

Example 4: Denture adhesive composition - Cream composition

Table 4

Procedure: The formulation was made on a lab scale using a speed mixer. The required quantities of petrolatum and mineral oil mineral oil were mixed at 2000rpm in speed mixer for lOMin. To the mix the weighed quantity of Locust bean gum was added and mixed at 2000rpm in speed mixer for another lOMin. To the mix the weighed quantity of Xanthan gum was added and mixed at 2000rpm in speed mixer for lOMin followed by the weighed quantity of Sodium CMC. The mixture was then further mixed at 2000rpm in speed mixer for lOMin. Finally the weighed quantity of Calcium acetate was added and mixed at 2000rpm in speed mixer for lOMin. The resultant mixture was mixed for a further 20Min at 2000rpm. The resultant cream was a smooth, viscous paste. Example 5: Denture adhesive composition - Powder Adhesive composition

Table 5

Procedure: All materials were sieved through #60 Mesh and weighed. Hydroxypropyl Methyl

Cellulose (HPMC), Konjac Gum, sodium CMC were transferred to a 500 CC HDPE container and mixed for 5 minutes using a Turbula mixer at room temperature. Spray Dried Peppermint and Spray Dried Spearmint were added to the HDPE container and mixed for 5 minutes. Finally DI-TAB was added and mixed for an additional 10 minutes.

Example 6: Denture adhesive composition - Powder Adhesive composition

Table 6

Procedure: All materials were sieved through #60 Mesh and weighed. Hydroxypropyl Methyl Cellulose (HPMC), Konjac Gum, sodium CMC were transferred to a 500 CC HDPE container and mixed for 5 minutes using a Turbula mixer at room temperature. Spray Dried Peppermint and Spray Dried Spearmint were added to the HDPE container and mixed for 5 minutes. Finally DI-TAB and Talc were added and mixed for an additional 10 minutes. Example 7: Denture adhesive composition - Powder Adhesive composition

Table 7

Procedure: All materials were sieved through #60 Mesh and weighed. Hydroxypropyl Methyl Cellulose (HPMC), Polyox, Konjac Gum, sodium CMC were transferred to a 500 CC HDPE container and mixed for 5 minutes using a Turbula mixer at room temperature. Spray Dried Peppermint and Spray Dried Spearmint were added to the HDPE container and mixed for 5 minutes. Finally DI-TAB and Talc were added and mixed for an additional 10 minutes.

Example 8: Denture adhesive composition - Powder Adhesive composition

Table 8

Procedure: All materials were sieved through #60 Mesh and weighted. Xanthan Gum, Hydroxypropyl Methyl Cellulose (HPMC), Konjac Gum, sodium CMC were transferred to a 500 CC HDPE containers and mixed for 5 minutes using a Turbula mixer at room temperature. Spray Dried Peppermint and Spray Dried Spearmint were added to the HDPE container and mixed for 5 minutes. Finally DI-TAB was added and mixed for an additional 10 minutes. Assessment of Adhesive Properties: Cream and Adhesive Powder Compositions (Examples 1 to 3 and 5 to 8)

Adhesion profile assessment:

To test the adhesion profile of denture adhesives in PBS solution an Instron Texture Analyzer (5943) equipped with BioPuls Bath and 500 N load cell was used (Instron, UK). 0.1 g of powder adhesive was added to 0.2 g of deionized water (1:2 ratios) and mixed to form a uniform paste. 0.2 ml of adhesive paste was placed on the texture analyser and initially compressed to 101 bf and then took through a compression cycle for a total of 5 minutes. The cross head was then moved apart with speed of 6lbf/min and the maximum tensile force recorded. This was repeated 12 times (cycles) for each sample.

Shear strength:

0.4 g of powder adhesive was added to 1.2 g of deionized water (1:3 ratios) and mixed for 30 sec. The uniform paste was placed on acrylic slides and pressed with 20lbf for 5 seconds followed by 5 minutes hydration. Similar to powder samples, 0.8 g of paste samples were mixed with 0.4g water and placed on acrylic slides and pressed with 20lbf for 5 seconds followed by 20 minutes hydration.

Adhesion was assessed by shear test performed on Instron 5943 (lnstron,UK) tensile testing machine equipped with a 500 N load cell. The crosshead speed was 0.5 in/min. For each test, the load versus displacement was measured, and the shear stress at break (ultimate adhesion strength or adhesion strength at break) is used to characterize adhesion for each composition. Each test was repeated at least five times.

Hang time

Hang time method was used for assessing the duration of hold of denture adhesives. 0.4 g of powder adhesive was added to 1.2 g of deionized water (1:3 ratio) and mixed for 30 sec. The uniform paste was placed on acrylic slides and pressed with 20lbf for 5 seconds followed by 5 minutes hydration. Similar to powder samples, 0.8 g of paste samples were mixed with 0.4g water and placed on acrylic slides and pressed with 201 bf for 5 seconds followed by 20 minutes hydration. Hang time stability of the samples was measured using a Lasting Adhesive Tester - CZY-6S equipped with 200g hook weight (Qualitest, Canada). Each sample was tested at least five times.

Comparative Evaluations: Cream Compositions The compositions of Examples 1, 2, 3 were compared and a comparative tabular representation of the tests conducted is shown in Table 9.

Table 9

Comparative Evaluations: Powder Adhesive Compositions

The compositions of Examples 4-8 were compared and a comparative tabular representation of the tests conducted is shown in Table 10.

Table 10

Assessment of Adhesive Properties: Example 4

Adhesion Profile Assessment: To test the adhesion profile of denture adhesives in PBS solution an Instron Texture Analyzer (5943) equipped with BioPuls Bath and 500 N load cell was used (Instron, UK). 0.1 g of powder adhesive was added to 0.2 g of deionized water (1:2 ratios) and mixed to form a uniform paste. 0.2 ml of adhesive paste was placed on the texture analyser and initially compressed to lOlbf and then took through a compression cycle for a total of 5 minutes. The cross head was then moved apart with speed of 6lbf/min and the maximum tensile force recorded. This was repeated 12 times (cycles) for each sample.

Sample preparation for hang time and shear stress: Weigh 0.8g paste and 0.4g of water in a beaker, mix the adhesive and water homogeneously with spatula for 5 seconds. (The initial 2 sec mixing was done slowly to incorporate the water into cream and further 3 sec vigorous mixing was done.) Spread the mixture over a one inch square area of acrylic slide, and cover with a second slide to give a 1 square inch overlap region. Compress to 20 pounds (lbs) for 5 seconds. Allow samples to hydrate for 5 minutes, then compress to 20 lbs for a further 5 seconds.

Shear strength: Adhesion was assessed by shear test performed on Instron 5943 (lnstron,UK) tensile testing machine equipped with a 500 N load cell. The crosshead speed was 0.5 in/min. For each test, the load versus displacement was measured, and the shear stress at break (ultimate adhesion strength or adhesion strength at break) is used to characterize adhesion for each composition. Each test was repeated at least five times.

Hang time: Hang time stability of the samples was measured using a Lasting Adhesive Tester - CZY- 6S equipped with 200g hook weight (Qualitest, Canada). Each sample was tested at least five times.

Table 11 Test Example 9

Shear stress 1.79

(Ibs/sq. inches)

1.19

Hang time (log Min)

The purpose of the above description is to illustrate some embodiments of the present invention without implying a limitation. It will be apparent to those skilled in the art that various modifications and variations may be made in the apparatus or procedure of the invention without departing from the scope or spirit of the invention.