Formulation of Toothpastes

FORMULATION

Toothpastes are the most popular form of dentifrices. They include the following ingredients which determine the quality and efficiency of toothpastes.

1.            Polishing Agents / Abrasive Agents:

The abrasives or the polishing agents are used to polish the teeth and remove food debris adhered to the surface of the teeth. They are used in concentration of about 20 - 50% of the total formulation.

They should possess the following characteristics:

    Ingredients Examples

The most commonly used Abrasive agents are as follow:

(a)            Precipitated Calcium Carbonate (CaCO3): It is also known as precipitated chalk and is available in a number of grades. The crystalline form of the precipitated chalk may be available as:

(i)             Calcite: Contains rhombohedral crystals.

Aragonite: Contains orthorhombic crystals.

Advantages:

·                               It is of very low cost.

·                               It is available in different grades in white or off-white colours.

·                               The lighter grades are very stable and do not get hardened on storage.

Disadvantages:

·                               The abrasivity is not consistent within the lots of same grade of powder due to the presence of impurities.

·                               It is incompatible with sodium fluoride which is used as anticaries agent.

(b)           Phosphates of Calcium: A large variety of insoluble calcium phosphates are used as abrasive agents. They may he as follows:

Dicalcium Phosphate (DCP) Dihydrate [CaHPO₄.2H₂O ]: It is a commonly used abrasive agent among the phosphate of calcium. Its properties and the advantages and disadvantages are follows.

Advantages:

·                               It provides good flavour stability.

·                               Toothpastes made with Dicalcium phosphate are better than toothpastes made with chalk.

·                               They do not make use of additional whitening agents.

·                               The hardening of the paste during preparation is accelerated in the presence-of fluoride ions.

·                               It has less abrasive effect on dentine.

Disadvantages:

·                               It is incompatible with sodium fluoride.

·                               The only source of fluoride is sodium monoiluoro phosphate since it consists of free calcium ions that react with other fluoride sources leading to incompatibility.

·                               The DCP Dihydrate is unstable in its natural for and may convert into anhydrous form which may result in hardening of the paste.

The other commonly used phosphates of calcium are tricalcium phosphate, calcium pyrophosphate etc., The insoluble sodium metaphosphate, dibasic ammonium phosphate are also used as abrasive agents.

(c)           Dental grade silica / Polymers of Silica (SiO₂)_n : They are polymer of silica that are commonly used as abrasive agents in the formulation of toothpaste `gels in large quantities. They are available in two forms as:

·                               Abrasive Form of Silica.

·                               Thickening Form of Silica.

Abrasive Silica: They are also referred to as xerolgels. They possess good abrasive property and are used in low concentration. They have least effect on the consistency of the finished product.

Thickening silica: They are referred to as aerogels. The particles are small in size and posses a greater surface area. They have the ability to swell and provide a thickening effect to the pastes.

Advantages:

The silicas are mostly used as abrasives in gels.

They are inert and easily compatible with other ingredients.

They provide good gloss to the dentine due to their high refractive index.

They can be used in low concentration.

Disadvantage: The abrasive property is not consistent within the different grades.    

(d)           Trihydrated Alumina (Al₂O₃.3H₂O): It may be available in two forms: As suspension or as crystalline powder.

Advantages:

·                               It is less costly.

·                               It possesses stability with fluorides.

·                               It is easily available and is stable during storage.

·                               It is compatible with other ingredients.

·                               It possesses a good abrasive property.

Disadvantage: It has poor thickening property.

2.          Foaming Agents / Surfactants:

They are also known as wetting agents. The mechanism of cleansing action is by reducing the surface tension at the interface of the adhered material and enamel of the teeth.

They aid in abrasive action by wetting the surface of the teeth. They help in the diffusion of into narrow spaces, thus enhancing the cleansing action. The properties of the surfactants are as follows:

·                               It should be compatible with other ingredients of the formulation.

·                               It should possess good surface active property.

·                               It should be non-toxic and non-irritant to the oral mucosa of the buccal cavity.

·                               It should be tasteless.

The most commonly used surfactants are:

(a)          Sodium Lauryl Sulphate (ROSO₃ Na): It is used in concentrations of 0.5 to 2% in order to provide necessary foaming action.

Advantages:

·                               It is available in a large variety of graded forms.

·                               The recrystallized grades have good surfactant property.

·                               They are more compatible with other ingredients of the formulation.

·                               They have a neutral pH range.

Disadvantages:

·                               The nature of the foaming agent may be altered by the presence of any free alcohol content.

·                               The different grades are very expensive.

(b)          Sodium Lauryl Sarcosinate: It is one of the most preferred detergents for oral products.

Advantages:

·                               It shows anti-enzymatic activity besides acting as a surface active agent.

·                               It is easily soluble in aqueous solvents and hence most preferred for the formulation of oral products.

·                               It is consistently stable with a neutral pH range.

Disadvantage: It may alter the taste of the final formulation when used in high concentrations.

3.          Humectants:

Humectants are used in order to prevent the rapid drying of dentifrices. They prevent excessive moisture loss from the product. They may additionally impart plasticity to the final product. The concentration of the humectant used in the formulation may vary from 20% to 40%.

The most commonly used humectants in the formulation of dentifrices are as follows:

(a)            Sorbitol 70: It consists of 70% w/v concentration of the sorbitol solution. It comprises the largest pan the humectant phase.

Advantages:

·                               It has high viscosity and can produce firm toothpastes with good plasticity.

·                               It imparts cool sensation in the mouth and may also enhance the sweetening property.

It possesses good compatibility with other ingredients; it is less expensive than glycerin.

(b)          Glycerine: It can be used at concentrations ranging between 5 to 10%.

Advantages:

·                               It provides a good gloss and good shine to the product.

·                               It is safe, stable and compatible with other ingredients.

·                               It is easily available both from natural and synthetic sources.

Disadvantages:

·                               It is very expensive.

·                               It provides a warm sensation in the mouth.

(c)          Propylene Glycol: it is less commonly used and has been replaced by sorbitol.

Advantage: It has good solvent properly and can also be used as a co-solvent.

Disadvantage: It has very low viscosity and may also impart a bitter taste to the product.

4.          Ceiling/ Binding Agents:

The binding agents are used in order to hold the solid and the liquid components together to form a smooth paste and maintain its property, particularly during storage. They prevent bleeding from the paste and also add up to the body and viscosity of the final formulation.

The commonly used binding agents are cellulose derivatives such as Carboxy Methyl Cellulose (CMC), Sodium Carboxy Methyl Cellulose (SCMC), HydroxyethyJ cellulose, Cellulose ethers etc.

(a)           Sodium CMC: It is a commonly used cellulose derivative and used in concentrations between 0.9 to 2.0%. It is sensitive to pH value outside 5.5 to 9.5. The properties with its advantages and disadvantages are as follows:

Advantages:

·                               It provides stability to the gels.

·                               It resists change in the efficiency of the formulation even in the presence of divalent calcium ions and other electrolytes.

Disadvantage: It may react with cationic substitutes of antibacterial agents due to its anionic nature. Hence it cannot be used in such formulations.

(b)          Ethers of Cellulose: Methyl cellulose and hydroxyethylcellulose are the most commonly used cellulose ethers.

Advantages:

·                               They are stable over a wide range of pH changes.

·                               They are not affected by the metallic ions.

·                               They can be used in the toothpastes containing cationic antibacterials.

·                               The properties can be adjusted as required by varying the degree of substitution of the components.

Disadvantages:

·                               The toothpastes made with cellulose ethers are more viscous at and stiff and disperse slower than those made with SCMC.

·                               They cannot be used with glycerine as they are incompatible with it.

The other naturally available gelling agents may be Gum karaya, Gum tragacanth, Iris moss (Chondrus), Gum Arabica etc,

(c)           Water: Water is used in the deionized form in the formulation of toothpastes. It can be used either as a solvent for the soluble ingredient of the formulation or as a supporting media for the binding agents. Binding agents swell after imbibing water. It is used in concentrations of more than 10% in the formulation of clear gels.

5.          Sweetening Agents:

These are added in. order to improve the sweetening properties and cover the bitter taste of the other ingredients like surfactants, binders etc. They help in promoting the acceptance of the product when administered orally.

The most commonly used sweetening agents are Saccharin sodium, Chloroform, Aspartame, Cyclamates and Potassium acesulfame.

(a)             Saccharin Sodium: It is the most widely used sweetening agent. It is used at concentrations of about 0.05 0.3 1 %. The concentration may vary depending upon the amount of humectant (glycerine) used.

Advantages:

·                               It is of low cost.

·                               It is widely distributed and easily available.

·                               It is compatible with all other ingredients.

·                               It provides good sweetening property.

(b)          Chloroform:

Advantages:

·                               It masks the taste of precipitated chalk and prevents dry feeling in the mouth.

·                               It provides a fresh and sharp sweetness.

·                               It also has antibacterial property besides the sweetening property.

Disadvantages:

·                               It is expensive.

·                               It is incompatible with certain ingredients.

6.            Flavouring Agents:

 Flavouring agents may comprise the most proprietary and most crucial part of the formulation essential to meet the consumer preferences. They are generally a mixture of edible volatile oils consisting of spearmint and peppermint oil as major components. The other components included may be thymol, anethol, eucalyptol, aniseed oil, oil of winter green etc. Flavouring agents are used in the concentration range of about 0.5 to 1. 5% and constitute the most costly part of the formula; they may interact with other components of the formulation which may result in incompatible.

7.          Colouring Agents:

They are used in concentration of less than 0.01% as permitted by the EEC Cosmetics Directive. They can be used generally in combination with a portion of a white creamy base. They are mainly in order to influence consumer preferences and increase the purchase intent.

8.             Whitening Agents:

Whitening agents such as Titanium dioxide (TiO₂) shall be preferentially added in order to provide additional whiteness and brilliance to the paste.

9.          Preservatives:

Preservatives are used in the formulation in order to maintain the properties of the product throughout the storage period and to improve the shelf-life of the product. Generally, a mixture of 5% methyl paraben and 0.02% propyl paraben is the most effective and commonly used combination preservatives. Sodium benzoate is not preferred due to its incompatibility with some of the therapeutic agents.

10.           Therapeutic Agents:

Therapeutic agents are included in toothpastes in order to provide additional beneficial effects besides normal cleansing properties.

Examples:

(a)         Anticaries Agents:

Example: Fluoride derivatives like NaF, Na2FPO3, etc,

(b)         Antiplaque Agents:

Example: Chlorohexidine, Triclosan etc,.

(c)         Antitartar Agents that prevent the Colouring of Teeth :

Example: Zn salts, Pyrophosphate ions, Tetra sodium pyrophosphate, Disodium dihydrophosphate.

(d)         Sensitive Dentine Agents:

Example:   Strontium   chloride,   Strontium   acetate, Formaldehyde etc,.

(e) Optical Brightness:

Example:   Substituted   coumarins   in   long   chain alkylamines.    

(e)                       Bleaching Agents:        

Example: H 2 O 2 , Sodium peroxide.

(g) pH Regulators: 

Example: Zirconium silicate.     

Toothpaste Formula:

Formula-1   Quantity for 100 g

Calcium carbonate (adhesive agent)    28 g

sodium lauryl sulphate (surfactant)     0.5 g

Glycerin (humectants)      11 g

Gum tragacanth (binding agent) 0.75 g

Water (liquid phase)         9.7 g

Saccharin sodium (sweetening agent)  0.05 g

Flavor (flavoring agent)    q. s

Preservative (for storage) q. s