The main ingredient is some form of abrasive, which will mechanically remove debris and also help in the polishing process. Toothpastes may contain some form of detergent to aid the cleaning process and improve the wetting of the surface of the teeth. Therapeutic agents such as one of the various forms of fluoride and whitening agents are added to enhance the enamel surface. Calculus (tartar) control agents such as sodium pyrophosphate and potassium pyrophosphate are also incorporated as well as desensitizing agents such as strontium chloride, potassium nitrate and calcium sodium phosphosilicate. See Table 17.1 for a list of common toothpaste ingredients.

More recently there have been attempts to add antimicrobial agents such as triclosan, an antibacterial and antifungal agent that is effective in preventing gingivitis (Figure 17.1). Chemically, triclosan is a polychlorophenoxyphenol. These antimicrobial agents help to control bacterial growth by preventing the bacterial proliferation phase of plaque development. Many dentists recommend a toothpaste to their patients which contains fluoride, triclosan and some form of pyrophosphate for the reasons mentioned above and described in detail later.

Fig. 17.1 A toothpaste containing triclosan (Colgate Total Advanced).

Flavouring agents may also include saccharin and xylitol. These are sugar substitutes, and xylitol is associated with caries inhibition. A variety of tooth-whitening agents may also be added. These are generally based on peroxide chemistry. For further details of these bleaching agents, see Chapter 18.

The factors which influence the effect of a toothpaste on the teeth are shown in Box 17.1.

The primary mode of action is by occlusion of the dentine tubules on the exposed root surface. Therefore the tooth is treated with a physical or chemical agent that forms a layer that mechanically obstructs the orifice to the tubule. This prevents tubular fluid movement and leads to a reduction in sensitivity. An alternative method of reduction in sensitivity is by blockage of nerve activity. Potassium ions concentrated within the interior of the dentine tubules are thought to cause depolarization of the membrane of the nerve terminal and this will decrease sensitivity. Unfortunately, with both these approaches, the effects are short term as the abrasive in the toothpaste will not only remove plaque but will also remove some of the outer surface of the root face and the sensitivity will return. In addition, if the patient consumes acidic solutions such as orange or lemon juice or any highly acidic food, there is a risk of tooth surface erosion and loss of the occluding material.

Calcium sodium phosphosilicate, a bioactive glass, has been incorporated into one toothpaste to reduce sensitivity. It undergoes a chemical reaction when which exposed to an aqueous medium such as saliva, provides calcium and phosphate ions. These ions react with tooth tissue to form hydroxy-carbonate-apatite, a mineral that is chemically similar to the inorganic phase of enamel and dentine. This layer has been shown to be effective in preventing further tooth surface demineralization.

Three different types of fluoride are used in toothpastes: stannous fluoride, sodium fluoride and sodium monofluorophosphate. In all cases, the formulation of the toothpaste has required considerable care as the interaction between some of the ingredients reduces the fluoride effect. Both the simple fluoride salts are relatively reactive. The addition of stannous fluoride went out of fashion a number of years ago as there were stability problems with the toothpastes and the taste was not particularly pleasant. Some patients also developed intrinsic staining. However, more recently a stabilized form of stannous fluoride has been developed with much better results.

Stannous fluoride is frequently used in combination with sodium hexametaphosphate, providing 1100 ppm fluoride (Figure 17.2). Stannous fluoride has been demonstrated to

Fig. 17.2 A toothpaste containing stannous fluoride and sodium hexametaphosphate (Pro-Expert, Oral B).

One of the main advantages of stannous fluoride is that it can be used in conjunction with calcium-based abrasives. Sodium fluoride is an alternative to stannous fluoride, but the prime difficulty with its use was the need to change a large number of the abrasives in the standard toothpaste formulations as the use of calcium-based materials leads to degradation of the mixture.

Sodium monofluorophosphate has been used as an alternative as it is more stable and not so susceptible to degradation. Most currently available toothpastes use either 0.45% stabilized stannous fluoride or the equivalent sodium fluoride concentration of 0.24%. Both deliver 1100 ppm fluoride. As well as the well-proven success in reducing the incidence of caries, both these materials also appear to have some beneficial effect on gingival health. Higher levels of fluoride are provided in certain toothpastes, which are recommended for patients with a high caries incidence. These can produce the equivalent of 2400 and 5000 ppm fluoride (Figure 17.3).

Fig. 17.3 Two dentifrices with higher levels of fluoride for use by patients with high caries risk (Duraphat 2800 and 5000, Colgate).

They should be used with care as overzealous use can potentially lead to enamel fluorosis (Figure 17.4) if too much is swallowed. Similarly some toothpastes are available which contain a lower concentration of fluoride and are intended for use by children and infants (Figure 17.5).

Fig. 17.4 ‘Mottled’ appearance of incisors indicative of enamel fluorosis.

Fig. 17.5 A dentifrice containing a lower concentration of fluoride. This product contains 1000 ppm of fluoride and is meant for the use by children and infants 0–3 years of age.

These are usually either tetra sodium or tetra potassium pyrophosphates. They inhibit growth of hydroxyapatite crystals and this in turn inhibits calculus formation above the gingival margin. Anticalculus agents have a bitter taste and flavourings are added to toothpastes to mask this taste. Sodium hexametaphosphate is a more recent addition to the list of anticalculus agents and appears to be as effective as the older materials.

The abrasives in toothpastes carry both benefits and risks for the teeth. The benefit is that the abrasive helps remove the debris but the risk is that if the abrasive is too effective it will also remove tooth substance. This problem is compounded by the fact that there are three different tooth tissues which may come in contact with the abrasive, all of which have different hardnesses and resistance to abrasion. Enamel is highly resistant to abrasion, dentine is more prone to abrasion while dental cementum is very easily abraded. Fortunately, toothpastes do not need to be too abrasive.

The standard toothpastes use calcium salts with the addition of alumina, whereas those where sodium fluoride is added use silica and mica, a sheet silicate (phyllosilicate) mineral, together with, in some cases, polymer beads, which may also act as an abrasive. The size and shape of the abrasive will influence the abrasiveness of the paste.

Table 17.2 and Figure 17.6 show representative examples of commercially available toothpastes. It is apparent that many international pharmaceutical companies sell a variety of toothpastes under different brand names. Many are claimed to carry out similar processes.

Table 17.2 Some toothpastes currently available on the market

POM, prescription only medicine. These toothpastes therefore should be prescribed by a dentist or doctor.

Fig. 17.6 Some of the many toothpaste products available on the market.

Chlorhexidine gluconate is used extensively to treat periodontal diseases. It has already been discussed in Chapter 13 as many dentists use it during the chemo-mechanical preparation of the root canal system. It is widely regarded as the gold standard active agent in periodontal treatment. It is used in a 0.2% solution and it is bacteriostatic as it inhibits growth of plaque bacteria. It has excellent substantivity as it remains active for up to 12 hours after the first application.

Chlorhexidine is so effective that if used long term, it can sterilize the mouth in effect. Furthermore, as it kills bacteria at higher concentrations, the dead bacteria can act as seeding agents in the mouth and increase calculus formation. Its use may also mask the patient’s own oral hygiene efforts. For these reasons, unless necessary, one bottle should be used as directed (rinse 10 ml for 60 seconds twice daily) and then the treatment discontinued for a period of 2–3 weeks. However, for certain patients, such as those on radiotherapy or chemotherapy, the long-term use of chlorhexidine products is recommended.

Unfortunately, chlorhexidine has some disadvantages:

Fig. 17.7 A gel containing chlorhexidine digluconate, which may be applied to the teeth with a toothbrush.

Clearly products containing chlorhexidine should not be used on patients who have a hypersensitivity to chlorhexidine. Hexetidine (an oral antibacterial and antifungal agent based on 5-amino-1,3-bis(2-ethylhexyl)hexahydro-5-methylpyrimidine) and cetylpyridinium chloride (a cationic quaternary ammonium compound) are also used in mouthrinses but their substantivity is lower than that of chlorhexidine. Rarely parotid swelling may occur with these products.

Table 17.3 and Figure 17.8 show some of the currently available commercial mouthwashes.

Fig. 17.8 Examples of commercially available mouthwashes.

Fluoride gels are products that are professionally applied in the surgery as their fluoride content is high. These gels are aimed at patients undergoing orthodontic treatment or patients with a high caries risk where individual treatment is more appropriate. Care must be taken in prescribing these, as fluoride levels in the water where the patient lives together with the additional fluoride provide by the product can result in the level of fluoride in the teeth exceeding the recommended level of 1 ppm. This may lead to enamel fluorosis.

Normally, these gels are applied in a tray which is held in the mouth for a period of time or applied to the teeth after cleaning with a normal toothpaste. The residue is then spat out, care being taken to avoid ingestion of the gel. Ideally, the patient should not eat or drink anything for approximately 30 minutes after the application. These gels contain one of three chemicals: acidulated phosphate fluoride (APF), sodium fluoride and stannous fluoride. These products are based on the work undertaken by Brudevold, who observed that fluoride uptake was increased in an acid environment. He demonstrated that an acid preparation containing both phosphate and fluoride ions minimized the risk of enamel dissolution by the acid and enhanced fluoride uptake. Neutral sodium fluoride (2%) gels for professional use are produced by Dentsply and Colgate markets the Phos-Flur Gel, which contains 1.1% sodium fluoride, and Acidulated Phosphate Gel.

Fluoride gels are also available for home applications. Here, the fluoride concentration is substantially lower, with the most frequently used chemical being a 0.4% stannous fluoride solution. A commercially available product is ClinPro (3M ESPE).

Another gel product, Cervitec Gel (Ivoclar Vivadent) combines fluoride in the form of 900 ppm sodium fluoride and 0.12% chlorhexidine (Figure 17.9). It is indicated to protect exposed root surfaces, treat hypersensitive areas and reduce the bacterial load on the surface of the tooth. It has been shown in clinical trials to be useful to reduce the caries rate in children.

Fig. 17.9 A preventive gel containing both fluoride and chlorhexidine (Cervitec Gel, Ivoclar Vivadent).

A varnish presentation is a very convenient method for the application of fluoride to a tooth surface. The sticky nature of the varnish helps to retain the fluoride in contact with the tooth surface for longer than with a toothpaste or mouthrinse. A varnish is indicated in the prevention of caries, especially root caries and is also used to treat dentine hypersensitivity. The fluoride is mixed with an alcoholic solution of resins to form the varnish. This organic solvent then evaporates when applied to the tooth surface and the varnish sets when exposed to moisture. It forms insoluble calcium fluoride globules which occlude the dentine tubules.

The concentration of sodium fluoride is described as a 5% concentration. This means that 1 ml of the suspension contains 50 mg of sodium fluoride, which is equivalent to 22.6 mg fluoride. Due to the high concentration of fluoride in this material, the prescribing dentist needs to be aware of the concurrent use of other fluoride-containing products as overdose may result. The dentist should target the at-risk teeth or early carious lesions as the product should not be applied indiscriminately for the same reason. Usually, two applications a year are recommended for children over 3 years of age and adults. However, if a particular child is causing concern then it may be used up to three to four times yearly.

The best-known fluoride varnish is Duraphat (Colgate; Figure 17.10). This banana-flavoured varnish is presented in a tube or in ampoules for ease of application.

Fig. 17.10 A fluoride varnish (Duraphat, Colgate).

Fluoride varnishes are frequently used by dentists to treat dentinal hypersensitivity. The main indication is to apply high levels of fluoride to a particular surface in an attempt to arrest an early carious lesion. Varnishes are also very effective at reducing dentinal hypersensitivity. Probably the most commonly used product for this indication is Duraphat (Colgate), however, other varnishes are now available which are intended specifically for the treatment of dentinal hypersensitivity. One such product is Clinpro White Varnish (3M ESPE; Figure 17.11), which also contains fluoride. In most cases, the desensitizing effect is achieved by the occlusion of the tubules and remineralization of the surrounding tooth tissue.

Fig. 17.11 A varnish used to treat hypersensitive dentine (Clinpro White Varnish, 3M ESPE)

Other water-based varnishes act to occlude the dentinal tubules by forming insoluble calcium and protein precipitates, thus reducing dentinal permeability. VivaSens (Ivoclar Vivadent) is an acid varnish with a base of ethanol. Dimethacrylate and methacrylate modified polyacrylic acids are carried in this vehicle together with some potassium fluoride. The penetration of potassium fluoride is assisted by the presence of the acid, and the dimethacrylates are precipitated out as the alcohol evaporates. The mode of action is primarily tubular occlusion, />