Chapter 17 Preventive and periodontal materials, implants and biomaterials
The old adage of prevention being better than cure is never truer than in dentistry. As dental tissues do not repair themselves readily, preventive dentistry has a critical role. Many of the vast range of products available on the market have a dual role, in that they are to prevent both dental caries and periodontal disease. This is mainly achieved by the control of dental plaque, by breaking down the biofilm and the killing of microorganisms. However, they may also perform additional functions, for example having a desensitizing effect on hypersensitive teeth. It is therefore not possible to categorize neatly these multifaceted products in a convenient way.
It is often the case that the sooner the diagnosis is made, the more favourable will be the outcome and prognosis for the patient. Of course it would be more preferable to identify patients who may be at a higher risk of developing a disease. This would allow preventive measures to be instigated, or the patient to be referred for specialist monitoring or treatment. A number of products are available on the market which may be used by the dental team at the chairside to this end. These range from disclosing solutions to identify dental plaque to products which stain potentially cancerous or malignant lesions.
For those patients with periodontal disease, a condition which still has no cure, products are available which either kill the microorganisms in the periodontal pocket or can be used to aid regeneration of the tissues that have been lost as a result of the disease process. There are many such biomaterials available and these may also be used in other oral surgical disciplines, as well as when placing dental implants to replace and aid regeneration of lost tissues.
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.
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.
Mode of action of desensitizing agents
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
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).
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).
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.
Children may be exposed to excessive fluoride if they swallow or ingest toothpaste or eat it. They should therefore put only a pea-sized amount of toothpaste on the toothbrush or even just a smear in the case of a toddler.
Commercially available products
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.
|Aquafresh Big Teeth||GlaxoSmithKline||6 + years; 1400 ppm fluoride|
|Aquafresh Fresh ‘N’ Minty||GlaxoSmithKline|
|Aquafresh ISO Active||GlaxoSmithKline|
|Aquafresh Little Teeth||GlaxoSmithKline||4–6 years and above, 1000 ppm fluoride|
|Aquafresh Milk Teeth||GlaxoSmithKline||0–3 years and above, 500 ppm fluoride|
|Arm and Hammer Advanced Whitening||Arm and Hammer||Baking soda base with micropolishing abrasives to polish the surface of the teeth|
|Arm and Hammer Enamelcare Whitening||Arm and Hammer||Contains calcium phosphate-based remineralizing system|
|Arm and Hammer Original Coolmint||Arm and Hammer||Abrasive is baking soda, so is less abrasive|
|Arm and Hammer Enamel Care Sensitive||Arm and Hammer||Addition of calcium phosphate-based agent to coat the foot surface|
|Colgate Proclincal White||Colgate||0.24% sodium fluoride|
|Colgate Cavity Protection||Colgate||0.76% sodium monofluorophosphate|
|Colgate Total Advanced clean||Colgate||Abrasive is silica|
|Colgate Oxygen Pure Freshness||Colgate|
|Colgate Sensitive Pro-Relief||Colgate||1450 ppm as sodium monofluorophosphate|
|Colgate Smiles Toothpaste||Colgate|
|Colgate Total Gum defence||Colgate||Triclosan copolymer added|
|Corsodyl Daily||GlaxoSmithKline||0.31% sodium fluoride (1400 ppm)|
|Crest||P&G Oral Health|
|Crest Complete||P&G Oral Health|
|Duraphat 2800 ppm||Colgate||Over 10 years (POM)|
|Duraphat 5000 ppm||Colgate||Over 16 years (POM)|
|Macleans White and Clean ISO-active||P&G Oral Health|
|Oral-B Children’s Toothpaste||P&G Oral Health||2–4 years of age|
|5–7 years of age|
|Oral B Pro Expert||P&G Oral Health||Over 12 years, stannous fluoride|
|Retardex||Rowpar Pharmaceuticals Inc.|
|Rembrandt Plus||P&G Oral Health|
|Rembrandt Sensitive||P&G Oral Health|
|Sensodyne Original||GlaxoSmithKline||Fluoride free|
|Sensodyne Rapid Relief||GlaxoSmithKline|
|Sensodyne Toothpaste Gel||GlaxoSmithKline||POM|
|Sensodyne Total Care Extra Fresh||GlaxoSmithKline|
POM, prescription only medicine. These toothpastes therefore should be prescribed by a dentist or doctor.
A mouthwash is a liquid solution used to deliver active chemicals to the teeth and the oral soft tissues. They are also referred to as mouthrinses and are most effective when used after brushing. They consist of an active agent which is dissolved in a carrier such as water or alcohol. The active agent may be antimicrobial or may confer protection against dental caries, in which case it will contain a fluoride preparation such as sodium fluoride. Mouthwashes also contain surfactants to improve the wetting ability of the mixtures as some of the ingredients have a relatively high surface tension. Additionally, flavourings are added to make the mouthwash more acceptable. Some mouthrinses have been specially designed for use in patients with xerostomia.
Some products contain alcohol, which acts as a preservative as well as the carrier. However, due to its erosive effects it may cause non-carious tooth surface loss. Similarly, resin-containing dental restorative materials may also be damaged by prolonged alcohol exposure from mouthrinses as the resins may soften. The use of alcohol-containing mouthrinses is unacceptable in child patients and for those whose culture precludes the use of alcohol. They should also be avoided in patients with mucositis as the alcohol will cause a painful ‘stinging’ reaction on the inflamed mucosa.
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.
• Its main drawback is that is stains teeth quickly because it is adsorbed onto the tooth surface and chemicals which stain are attracted to it. This is more pronounced with certain substances such as tea, coffee and red wine. The margins of resin-based composites may stain as will any rough surfaces. If this occurs then care is required when removing the stain that no damage to the resin composite restoration ensues. If the product is used on a toothbrush rather than as a mouthwash then the staining and unpleasant taste is reduced. To facilitate this, a gel presentation is available (Figure 17.7). Should staining occur, it is reasonably easily removed by a professional cleaning (see Chapter 19 for information on products used for this purpose).
• Its efficacy may be compromised by certain other chemicals added to products. Chlorhexidine is cationic in nature. Anionic compounds, particularly surfactants, such as sodium lauryl sulphate which is used in toothpaste to reduce staining, reduces the efficacy of chlorhexidine.
• It has a very poor penetration of the subgingival biofilm and so its use in anaerobic environments like deep periodontal pockets is limited. Furthermore, it is flushed out from the pockets by crevicular fluid too quickly and neutralized by inflammatory products such as immunoglobulins.
• It has a taste which is very difficult to mask by other chemicals, so preparations containing chlorhexidine may not have a pleasant taste. Many patients complain that it has a slightly metallic taste. Attempts to improve the taste at 0.2% have affected the efficacy.
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.
Other fluoride products
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.
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.
Some fluoride varnishes contain colophony. This is another term for rosin (see Chapters 12 and 16). Patients may have hypersensitivity to colophony and so the dentist should enquire about this when taking the medical history if one of these products is being considered for use. Colophony is also contraindicated in patients with bronchial asthma.
Hypersensitivity to hot and cold foods and drinks may be associated with pain and may be debilitating for the patient. The dentinal tubules are filled with fluid and contain nerve terminal endings. Exposure to hot or cold stimuli causes the fluid to move within the tubules so effecting a neural response. As there are only pain receptors in the dental pulp, this response is interpreted by the brain as pain. As described above, desensitizing agents work in one of two ways:
In order to enhance the desensitizing effect of toothpastes marketed for sensitivity, the patient should be advised to place the toothpaste on the affected tooth surface last thing at night after brushing. If the toothpaste is allowed to dwell for a longer period on the surface of the tooth (i.e. during the night) its effect will be seen more quickly.
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.
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, />