Dental caries affects the tooth itself and its consequences are well known to most people particularly those aged 30 years or over. Most people growing up as children in Ireland in the '40s, '50s and '60s have experienced the blackened appearance of decayed teeth, toothache and "gumboils". Most would also have experienced the extraction of teeth, frequently under general anaesthetic. Caries begins with a small patch of demineralised (softened) enamel at the tooth surface, often hidden from sight in the fissures (grooves) or in between the teeth. The destruction spreads into the dentine (the softer, sensitive part of the tooth beneath the enamel). The weakened enamel then collapses to form a cavity and the tooth is progressively destroyed. Caries can also attack the roots of teeth should they become exposed by gum recession. This is more common in older adults.
Dental caries is caused by the action of acids on the enamel surface.
The acid is produced when sugars, mainly sucrose in the diet either in foods or drinks, react with bacteria present in the plaque or soft film on the teeth. This reaction leads to a loss of calcium and phosphate from the enamel; this is called demineralisation. When it occurs frequently over many months there is a breakdown of the enamel surface leading to a cavity. Fluoride, when present in the mouth, slows down the process of demineralisation, particularly on non-biting surfaces of the teeth; fluoride is less effective on the biting or fissure surfaces.
Recently there has been some concern about possible damage to health from use of mercury amalgam material which is used to fill cavities caused by decay. In fact extensive research has shown that there is no link between the presence of amalgam fillings in the mouth and systemic disease. Alternative tooth coloured filling materials are currently being researched which may prove in the long-term to be viable alternatives to amalgam.
Prevention of Dental Caries
The prevention of dental caries can be approached in four ways:
- Use fluorides
- Reduce frequent consumption of sugars
- Control plaque
- Seal fissures
Fluorides
In Ireland 73 per cent of the population reside in communities served with water supplies which contain 1 part per million fluoride. This measure was introduced over 30 years ago and its beneficial effect is seen in the improvement of dental health of children and adults. In addition toothpastes containing fluoride now occupy over 95% of the toothpaste sales in this country and provide added benefit. Also sales of mouthrinses have increased considerably over the last 10 years and many of these contain fluoride.
Fluoride works mainly by slowing down the process whereby the enamel loses calcium and phosphate when exposed to acid following ingestion of food and drinks which contain sugars. It also helps to "heal" surfaces which show early signs of calcium or phosphate loss, such as an opaque appearance. Hence, most benefit is obtained if the level of fluoride is maintained at an elevated level in the mouth throughout the day. The main advantage of water fluoridation is that its caries reducing effects are available to everybody on the fluoridated water supply. Bottled drinking water contains highly variable amounts of fluoride depending on the source. Fluoride toothpastes are also an important source of fluoride and these should be used twice a day to maintain the level of fluoride in the mouth; fluoride mouthrinses are particularly useful for people who are prone to high levels of decay and also for people wearing orthodontic braces. Another alternative is a fortnightly fluoride mouthrinse - such mouthrinse programmes are used in a number of schools in non-fluoridated areas.
Reduce Frequent Consumption of Sugars
Dietary advice should be aimed at limiting the frequency of sugar intake. Food and drinks containing sugars should be recognised and their frequency of intake reduced especially between meals (see charts for details). Detailed advice on nutrition and oral health is given in Chapter 4.
Control Plaque
Although caries cannot develop except in the presence of plaque, plaque removal by toothbrushing cannot alone be advocated for caries prevention. Firstly normal brushing inevitably leaves some plaque in fissures and other stagnation sites where caries occurs, and secondly plaque rapidly begins to reform on cleaned tooth surfaces. Hence, while toothbrushing is important for maintaining gingival health, numerous studies have failed to establish a clear association between toothbrushing and caries incidence.
However, brushing with a fluoride toothpaste is the most important method of delivering fluoride to the tooth surface. Other suggested methods for plaque removal such as eating fibrous foods like apples and carrots have been shown to be ineffective.
Seal Fissures
A further way of helping to prevent dental caries is for a plastic film to be professionally applied to pit and fissure surfaces of teeth as soon as possible after they erupt into the mouth. This prevents access of plaque and plaque acids to the enamel surface. Numerous clinical trials have shown that sealants can be well retained and do prevent caries. However, they are only effective on the biting surfaces of teeth and should be seen as only one part of a comprehensive preventive plan.
When devising a strategy for the control of dental decay for an individual patient or for a community it is strongly recommended that a combination of the above strategies should be used taking into account the cost and effort required by the consumer.
