Holes in teeth are the result of our modern diet, particularly sugars and carbohydrates. A certain type of microbe feeds upon sugars, excreting acids that bore into enamel. After a hole is formed in a tooth, the acid-generating bacteria live in it and continue their dirty work: they form their own ecological niche, and eventually they make the cavity worse.
Dental caries (decay) is one of the most prevalent infectious diseases of man. It is a localized, progressive demineralization of the hard tissues of the crown (coronal enamel, dentine) and root (cementum, dentine) surfaces of teeth.
The pit-and-fissure surfaces of teeth are more susceptible to decay than are the smooth surfaces. It it is no surprise to find that the rear molar and premolar teeth that have pit-and-fissure surfaces are more susceptible than the front teeth. Based on epidemiologic studies, the pit-and-fissure biting surfaces of molar teeth usually decay within three years of eruption or not at all.
Incidence; Causes and Development; Contributing Risk Factors
Although great international and regional differences exist, the incidence and prevalence of coronal dental caries have declined in industrialized countries over the past 20 years. This change has been well documented for children and adolescents, and many children now have experienced no decay or fillings at all. In the U.S. in 1986-87, 50% of 5-17 year old children were completely free of decay and of restorations in their permanent teeth
In adults, there have been small reductions in the number of decayed, missing and filled teeth and in the rate of total tooth loss. Amongst adults who have teeth, the decline in missing teeth has been more substantial. While it is believed that the marked improvement in dental caries status and greater tooth retention experienced by children will eventually be evident in adults, a long transition period of about 40 years will be required before improvement is evident in all adult age groups.
The extensive decline in dental caries has not benefited all children equally. U.S. data reveal that 20-25% of children still have high decay levels - the so-called high-risk children. Adults not yet benefiting from this decline still have decay and fillings characteristic of a previous era. Secondary decay around old fillings, replacement fillings and breakage of tooth cusps due to extensive fillings are commonplace in this age group and represent a large treatment backlog.
Demineralization is caused by acids produced by bacteria
, particularly mutans Streptococci
and possibly lactobacilli
, that ferment dietary carbohydrates
This process occurs within a bacteria-laden gelatinous material called dental plaque that adheres to tooth surfaces and becomes colonized by bacteria. Thus, caries results from the interplay of three main factors over time: dietary carbohydrates, cariogenic bacteria within dental plaque, and susceptible hard tooth surfaces. Dental caries is a dynamic process since periods of demineralization alternate with periods of remineralization through the action of fluoride, calcium
and phosphorous contained in oral fluids.
In June of 2012 it was reported in the New York Times that brushing within 20 minutes of a meal, or within 30 minutes of consuming acidic foodstuffs such as sodas, lemonade or orange juice, can do more harm than good. Acid from acidic drinks temporarily softens the enamel of the teeth, allowing brushing to drive the acid right into the dentin level below. It was concluded that the ideal time to brush teeth is within 30-60 minutes of a meal
Dental caries are age-related. Prevalence begins soon after tooth eruption in susceptible children and increases with age. Data from older Canadian studies, when dental caries were more prevalent, suggest that caries incidence had three peaks: at about age 7 years for coronal decay of the primary dentition; at about age 14 years for coronal decay of the permanent dentition; and, for root surface decay, incidence began at about age 30-40 years with steady increases thereafter.
Children and adults with special medical problems are at higher risk for dental caries. These include bulimics, those with Sjogren's syndrome, and those receiving therapeutic head and neck radiation, chemotherapy
, or prolonged treatment with drugs that reduce salivary
flow. Institutionalized and physically and mentally disabled persons are also at higher risk for dental caries.
Detailed reviews of the many risk factors and risk indicators for dental caries have been reported elsewhere. Age, socioeconomic status and past dental caries are strongly linked with dental caries incidence; oral hygiene as practised by most people is not strongly related to dental caries occurrence. Although past research indicated that sugar was a definite risk factor, more recent research findings about the effect of contemporary dietary practices on dental caries have given differing results except possibly for those at high risk because of high sugar intake and poor oral hygiene.
Diagnosis and Tests
Traditionally, the clinical detection of carious lesions
on tooth crowns has involved the use of a sharp explorer, a viewing mirror, an artificial light source and air-drying of tooth surfaces to improve visibility. This visual and tactile approach is often supplemented by the use of selected radiographs to help in the diagnosis of small (incipient) lesions on the hidden surfaces between adjacent teeth. The early clinical detection of incipient carious lesions has attracted increased interest recently because of the possibility that primary preventive procedures used by patients or by dental personnel may enhance remineralization and even arrest dental decay.
Diagnosis of dental caries and treatment planning in clinical practice is idiosyncratic and plagued with considerable variation among dentists. This has been demonstrated when the same group of patients and the same set of radiographs were examined.
Treatment and Prevention
There are four types of primary prevention: fluorides; fissure sealants; dietary counselling; and oral hygiene.Systemic Fluorides
This topic is covered here despite the belief by many that fluoride is not only ineffective but in fact harmful.
Despite the apparent reduction in effectiveness of water fluoridation due to declining caries levels (from about 50% reduction in decay to 20-40%), fluoridation of the water supply remains, according to many dentists, the single most effective, equitable and efficient means of preventing coronal and root dental caries. The impact of water fluoridation on coronal decay in children, adolescents and adults has been studied in numerous community trials and economic evaluations and the impact on root caries has been evaluated in case-control studies. Because of the widespread availability of fluorides (in dentifrices, water, vitamin supplements, manufactured beverages and food), there is now concern about increases in the prevalence of (usually) very mild fluorosis in children's teeth. Although mild fluorosis is usually neither unsightly nor easily visible, it is, nevertheless, evidence of excess fluoride intake.
A principal reason for the observed increase in fluorosis appears to be inappropriate prescribing of systemic fluoride supplements by dentists and physicians and/or overzealous use of these supplements by parents for their children. More recent modifications to the supplemental dose schedule to avoid fluorosis suggest lower intakes of fluoride supplements because of increased use of fluoride toothpastes and ingestion of other food and beverage sources of systemic (and topical
) fluoride that were not widely available when previous guidelines were formulated.
Professionally-applied topical fluorides, e.g. acidulated phosphate F gel in trays, have been proven efficacious in randomized clinical trials in children, though there have been few trials since 1980, the era of decline in caries incidence. It has now been established that there is no need for a cleaning of the teeth prior to the application of a topical fluoride but similar evidence for biannual rather than annual applications is lacking.
Today, costly professionally-applied topical fluoride cannot be recommended for use with most children in communities with water fluoridation or, indeed, for most children generally because of the dental caries decline. However, this form of fluoride therapy is recommended for persons with active decay and those at high risk, for those undergoing head and neck radiation therapy
and for older adults experiencing root caries.
Self-applied fluorides include the widely-used fluoride dentifrices that are strongly recommended because of their ease of use, low cost and effectiveness on coronal and root caries prevention based on randomized clinical trials. The primary reason for the caries decline in developed countries is invariably ascribed to fluoride dentifrices. However, concerns about a possible increase in mild tooth fluorosis have prompted recommendations to use less dentifrice and supervise the toothbrushing of young children.
Fluoride mouth rinses were recommended a few years ago for general use. However, because of the decline in caries and concerns about excess fluoride ingestion, they are now recommended only for those at high risk to dental caries and for those not regularly using a fluoride dentifrice. None of these rinses are intended for use in children under age 5.Fissure Sealants
These are resins applied by dental personnel to the pit-and-fissure surfaces of posterior teeth. They have been extensively tested since 1979 in randomized clinical trials and have proven to be effective in reducing this most common form of surface decay. Because of their high cost, the general decline in decay and differential tendencies for certain fissures to decay, sealants should be applied selectively to high risk patients and to permanent molars only, within 2-3 years after tooth eruption.Dietary Counselling
Encouragement to reduce sucrose intake and use dentally 'safe' substitutes may be less important now for the majority of persons. Two cohort dietary studies revealed that dental caries incidence was low among study children despite their high sugar consumption. In one study, the only apparent causative role of sugar was related to decay of smooth surfaces between the teeth; however, this type of surface decay has rapidly declined in children recently. The effectiveness of dental counselling in inducing behaviour change is suspect. Since sugars are one of the etiologic factors in the caries process, selective counselling limited to high-risk children may still be indicated. Similarly, because of the high risk of severe decay to infants' teeth due to this practice, the majority of studies do not advise the nocturnal or other prolonged use of baby bottles containing liquids other than water.Oral Hygiene
Oral hygiene procedures consist of personal plaque removal by toothbrushing and/or flossing as well as the professional prophylaxis that often precedes a periodic dental examination. As ordinarily practised, in neither case is there evidence that these lead to caries reductions. Daily personal oral hygiene (toothbrushing and flossing) is recommended in the interest of good hygiene and for the control of gingival disease. Toothbrushing is also required for the self-application of fluoride dentifrice, a proven caries preventive.