Dental caries

Process and incidence of dental caries

Dental caries ( tooth decay ) is a pathological process resulting in localised destruction of tooth issue.
The disease begins with demineralisation of the hard tissue of the tooth by organic acid.
Bacteria resident in dental plaque produce these acids by fermenting carbonhydrates in food.

The incidence of dental caries has declined in most developed countries over the last three decades, largely due to use of fluorides. However, the incidence has now plateaued, and there are some indications that the rate of caries may be increasing in children. Therefore, although preventable, dental caries remains a major worldwide public health problem.

Pathology of dental caries

Dental plaque must be present for caries to develop. Dental plaque is complex biofilm that builds up on teeth. It includes a mixed community of bacteria and their by products. These bacteria have variable capacities to produce organic acids ( eg acetic, lactic and formic acids) from fermentable carbonhydrates ( particularly dietary sugars). Frequent exposure to fermentable carbonhydrates leads to an increase in the population of cariogenic bacteria ( eg streptococcus mutans and Lactobacillus species) in the biofilm. These bacteria survive readily in an acidic environment and, when exposed to sugars, are prolific producers of organic acids, particularly lactic acid.
This causes the pH of the biofilm to fall below the critical pH for maintaining enamel mineral content ( carbonated hydroxyapatite) and results in enamel demineralisation.

Frequent exposure to fermentable carbonhydrates maintains th plaque pH below the critical pH for extended periods, leading to net subsurface enamel demineralisation and the formation of " White spot" carious lesions. These lesions have relatively intact surface, but continued subsurface demineralisation can progress to cavitation. If untreated, larger and deeper cavities form. Once cavitation occurs within dentine, caries gradually progresses towards the dental pulp, leading to pulpitis. Once pulpitis is established, pain is experienced with various stimuli. Eventually, if the caries is still untreated, pulpitis will be followed by pulp necrosis and infection of root canal system, which progresses to inflammation of the periapical tissues ( known as apical peridontitis ) Infection of the root canal system can also give rise to periapical abscess.

The ability of plaque bacteria to demineralise the tooth surface can be modified by several factors, including:

* diet - patterns of consumption ( frequency) and type of diet ( eg high sugar content)
* Plaque amount and composition - the level of cariogenic bacteria in plaque and their capacity to produce a sustained low pH environment.
* Saliva composition and characteristics ( eg flow, buffering capacity; antimicrobial factors: calcium, phosphate, hydroxide and fluoride ion concentrations: the effect of drug therapy)
*tooth resistance ( eg exposure to remineralising agents such as topical fluoride and casein phosphopeptide- armophous calcium phosphate ( CPP- ACP) )

Management of dental caries

Individual caries risk assessment

Changing perceptions on management favour treating dental caries as an infectious disease, with an emphasis on individual caries risk assessment, preventive strategies and minimal intervention.

Individual caries risk assessment involves quantification of risk factors such as saliva quality and quantity, plaque characteristics, diet, oral hygiene habits and the use of fluoridated products. Early modification of these factors is part of the primary preventive strategy.

Minimal intervention involves early diagnosis and interception of carious lesions ( including chemical treatment of lesions) minimally destructive methods of removing infected tooth structure after cavitation has occurred, and restoration of cavities with adhesive dental materials that do not require removal of sound tooth tissue for their retention in the prepared cavity.

Early " white spot" lesions can be accurately detected and quantified by traditional methods ( eg visual and radiographic techniques ) as well as newer technologies involving laser and light - induced fluorescence. This allows an assessment of the effect of preventive interventions over time.
It is now recognised the carious lesions can be identified before a " white spot" can be seen, through careful drying of enamel or by using enhanced visual methods. Early recognition of carious lesions in enamel maximises the opportunities for their arrest and reversal. Similar considerations apply to lesions that develop on exposed root surfaces, which undergo softening over a broad front.

General considerations

In early stages of caries, before a cavity forms, several strategies can be used to arrest further decay and promote remineralisation:
* plaque reduction by cleaning of teeth:
- brushing at least twice a day with toothpaste containing fluoride
- flossing , preferably immediately before brushing
- using other interdental cleaning aids
* dietary modification, particularly avoiding sucrose in sticky forms or as snacks between meals, and limiting the intake of acidic drinks containing sucrose and other fermentable carbonhydrates between meals.
* Plaque modifications, to reduce the level of cariogenic bacteria, by using antimicrobial products ( eg chlohexidine gel0 , or topical fluoride at high concentrations and in an acidualated form, which has an antimicrobial effect.
* tooth surface modification by application of remineralising agents such as fluoride and casein phosphopeptide amorphous calcium phosphate ( CPP- ACP), and by the placement of fissure sealants and other adhesive materials that cover and protect the tooth surface
* increased salivary flow and buffering capacity by using low acid, sugar free chewing gum or lozenges, or nonacidic coarse food. ( eg carrots).

After cavitation has occurred, the infected tooth structure must be removed and cavity restored. Following restoration of the tooth, strategies must be used to decrease caries risk and prevent further decay.

Fluoride

In randomised controlled clinical trials, the use of toothpastes and mouthwashes containing fluoride significantly reduced in incidence of caries. The efficacy of these products has been attributed to their ability to incorporate fluoride ions into plaque - several studies have shown an inverse relationship between plaque fluoride concentrations and caries. Onece plaque fluid or the incipient carious lesion fluid becomes supersaturated with fluoride, the fluoride ions immediately promote enamel remineralisation through the formation of fluoride - containing apaties ( eg Fluorhydroxyapatite and / or fluorapatite) , which are more resistant to future acid challenge than the carbonated hydroxyapatites of normal tooth enamel.

Fluoride ions have an antimicrobial effect at very high concentrations. Formulations with low pH ( eg acidulated phosphate fluoride) also have some antimicrobial activity.

Toothpastes and other topical applications containing fluoride should be used with are in children less than 6 years of age to minimise the ingestion of fluoride. Excessive ingestion of fluoride during the tooth forming years damages the enamel forming cell resulting in an irreversible mineralisaton disorder of the teeth known as dental fluorosis.
In patients with dental fluorosis, the porosity of the subsurface enamel is increased and the teeth may have white spots, various discolourations and / or mottling of the enamel.

Children less than 18 months of age frequently swallow toothpaste so they should have their teeth cleaned with a child sized soft toothbrush but with no toothpaste, unless they are at high risk of caries and toothpaste is used on the prescription of dentist .

Adults and children more than 18 months of age can benefit from using a toothpaste containing fluoride twice daily.
After brushing , toothpaste should be spat out and not swallowed: the mouth should not be rinse:

children 18 months to less than 6 years - toothpaste containing fluoride 400 to 550 ppm( 0.4 to 0.55 mg/g), a small pea sized amount applied to child sized soft toothbrush, twice daily if risk of caries is low.

adults and children 6 years or more - toothpaste containing fluoride 1000 ppm ( 1 mg/g) twice daily.

Children less than 6 years at high risk of caries may require the use of adult strength toothpaste under parent supervision, as prescribed by their dentist.
Parents should be advised of the risk of dental fluorosis.
Table below shows examples of topical fluoride applications and they can be used to reduce caries in patients at high risk of caries. Fluoride supplements in the form of drops or tablets are no longer recommend because of risk of dental fluorosis and limited efficacy.
Community water fluoridation is supported by scientific evidence as an effective , inexpensive and safe community health measure to prevent dental caries.

Chlohexidine

Chlohexidine has a role in caries susceptible children and adults. It does not reduce established plaque, but helps prevent plaque formation on a cleaned tooth surface. The anionic detergent sodium lauryl sulfate used in standard toothpaste inactivates chlohexidine, so chlohexidine should not be used immediately before or after standard toothpaste.

Chlohexidine gel is preferred for caries control as it has fewer adverse effects than the mouthwash and can be used weekly.

Casein phosphopeptide amorphous calcium phosphate ( CPP- ACP).

Calcium and phosphate ions are required with hydroxy and fluoride ions for the formation of fluorhydroxyapatite, with fluoride ions for the formation of fluorapatite. In the healthy mouth, the low concentrations of calcium and phosphate ions can limit the remineralising action of fluoride, and this calcium limitation is exacerbated in dry mouth ( hyposalivation). The intraoral persistence of calcium and phosphate ions is limited as they combine rapidly into insoluble and nonbioavailable forms.
Casein phosphopeptide amorphous calcium phosphate ( CPP- ACP) contains high concentrations of calcium and phosphate ions stabilities in a bioavailable form using phosphopeptides from the milk protein casein. This form of bioavailable calcium phosphate can help slow the progression of caries and promote regression in the early stages of the disease. CPP- ACP is available in a sugar- free chewing gum and in creams

CPP-ACP should be avoided in patients with allergies to milk proteins.

Examples of topical applications and how they can be used to reduce caries in patients at high risk of caries.

* Fluoride vanish 22600 ( 22.6 mg/mL) : Apply in the dental surgery to all at risk dental surface at the clinician's discretion, usually twice a year depending on caries risk.

* Acidulated phosphate fluoride gel or foam 1500 to 12300 ppm( 1.5 to 12.3 mg/g): Can be used by adults and children aged 10 years or more. Apply in the dental surgery for 4 minutes trays- evacuate excess, and spit out residual gel after tray removal. Adults can use the geo daily at home by brushing on the teeth , or apply it using customised trays. While the use of gels is still relatively common, they have largely been replaced by concentrated fluoride vanishes in dental surgeries.
Concentrated fluoride toothpastes and other remineralising pastes are preferred for home use.

Acidulated gel or foam is preferred as it has better enamel uptake: however, it is better to use neutral gel or foam in patients with ceramic crown and bridgework, direct restorations containing glass particles, or poor salivary flow ( eg those undergoing head and /or neck irradiation).

* Fluoride mouthwash 200ppm( 0.2 mg/mL): Can be used daily by adults and children aged 6 years or more. After rinsing , the mouthwash should be spat out and not swallowed.

* Neutral fluoride mouthwash 900 ppm ( 0.9 mg/mL) : Can be used weekly or daily by adults and children aged 6 years or more. After rinsing, the mouthwash should be spat out and not swallowed.

* Neutral fluoride toothpaste 5000 ppm( 5mg/mL) : Can be used daily by adults and children aged 10 years or more.

* Chlohexidine 0.2% gel: Can be used weekly or daily by brushing on the teeth ( pea- sized amount on a soft toothbrush) for 7 to 14 days.

* Casein phosphopeptide - amorphous calcium phosphate ( CPP- ACP).

+ CPP- ACP sugar- free gum : Can be used 4 times daily, preferably after meals and after cleaning teeth with a toothpaste containing fluoride.
+ CPP-ACP cream : Apply in the dental surgery after dental procedures and after topical fluoride applications. Adults can apply the cream nightly to teeth after tooth- cleaning and not rinse out.