Dental caries, also known as cavities, are caused due to the breakdown of teeth by bacterial activity. Dental caries are very common and affect people from all walks of life and all parts of the world. In fact, more than 2 billion people suffer from dental caries. Dental caries affect 60 to 90% of schoolchildren and the vast majority of adults. The World Health Organization (WHO) estimates that almost all adults will have dental caries at some point in their lifetime. Brushing the teeth twice daily, flossing regularly and using a medicated mouthwash can reduce the risk of dental caries significantly. Taking a diet low in sugar and small amounts of fluoride can also reduce the risk of dental caries.
Signs and symptoms of dental caries
The following are the common signs and symptoms of dental caries:
- Tooth ache
- Increased tooth sensitivity
- Sharp pain when eating something sweet, hot or cold
- Visible holes in the teeth
- Brown or black staining on the teeth surfaces
- Pain when you bite or chew food
Often, dental caries do not present any observable signs and symptoms in the initial stages. In fact, a person having caries may not even be aware of the disease. Dental caries begin as white spots on the surface of the teeth. These white spots are caused due to demineralization of the enamel of the teeth. This is known as a white spot lesion or microcavity. The lesion will continue to demineralize and turn brown in color. It eventually turns into a cavity. Before formation of the cavity, the process can be reversed. However, once the cavity develops the chances of regeneration of lost tooth is low.
The cavity becomes more noticeable if the enamel and dentin are affected. The affected portions of the tooth change color and become soft. As the decay progresses through the enamel into the dentin, pain and sensitivity will be experienced. This is because the dentin layer contains nerves. The pain may become worse when the tooth comes into contact with hot or cold foods. Dental caries also weaken the teeth and can result in sudden fractures. When the decay progresses to the center of the tooth, a tooth ache results.
Dental caries also cause bad breath. In some cases, infection can also spread to the tissues surrounding the teeth. In fact, there is also a growing body of research which indicates that tooth decay can cause cardiovascular problems.
Causes of dental caries
There are four requirements for dental caries to develop:
- Availability of surface i.e. enamel or dentin (of course!)
- Fermentable carbohydrates such as sucrose
In the absence of any of these four factors, dental caries cannot develop. Dental cavities are formed due to dental plaque. Dental plaque is a layer of bacteria that is formed on the surface of the teeth. Bacteria present in the dental plaque break down carbohydrates and produce acid. This acid destroys the teeth surface and causes cavities.
Bacteria that cause dental caries
The mouth contains large number of different kinds of bacteria. However, only a few specific species of bacteria cause dental cavities. These bacteria include Streptococcus mutans and lactobacillus. These bacteria synthesize more acid by fermenting sugars present in the food, leading to formation of dental caries.
Bacteria present in the mouth convert dietary sugars such as glucose, fructose and sucrose (table sugar) into lactic acid by fermentation. This acid dissolves the mineral content of the teeth when left in contact. This process is dynamic and the dissolved mineral is replaced to some extent. When demineralization continues over time, a cavity or hole is formed in the tooth.
Sucrose (table sugar) is more harmful than glucose and fructose. This is because bacteria can derive more energy from sucrose. Bacteria also convert sucrose into a sticky substance called dextran polysaccharide which aids in the formation of bacterial biofilm or plaque. Therefore taking sugary foods increases the risk of dental cavities. On the other hand, fruits which contain fructose do not significantly increase the risk of dental caries.
Other factors that can cause dental caries
Reduced salivary flow can increase the risk of dental caries. Saliva balances the pH and also washes away the bacteria present in the mouth. Therefore, it is responsible for prevention of dental caries and other dental problems. Certain diseases or drugs can affect the secretion of saliva and lead to dryness of the mouth. They increase the risk of dental caries significantly. Examples of diseases that reduce the secretion of saliva include diabetes and sarcoidosis. Medications that decrease salivary secretion and increase the risk of dental cavities include certain antihistamines and antidepressants.
The use of tobacco products can also increase the risk of cavities. Tobacco increases the risk of periodontal disease which causes the gingiva to recede. Gingival recession causes the exposure of the root surface of the teeth. Unlike the enamel, the cementum which covers the root surface of the teeth is easily demineralized by acids. Therefore the risk of root caries is very high in tobacco users. Since tobacco products also have other health consequences, it is best to totally avoid them.
Diagnosis of dental caries
Dentists employ a number of techniques and instruments to diagnose caries. Dental caries appear initially as a small chalky spot and then develop into a cavitation. Sometimes dental caries are directly visible. However, X-rays may be employed less visible caries and to find out the extent of damage to the tissues of the teeth.
The dentist will diagnose dental caries by inspecting all the teeth surfaces using a light source, dental mirror and an instrument known as explorer (also known as sickle probe). He/she may take an X-ray scan of your teeth to detect dental caries before they are otherwise visible. X-rays detect smaller lesions and caries that are situated between the teeth. Sometimes, laser speckle image (LSI) techniques may also be used to detect dental caries.
Dental caries can be easily prevented by maintaining oral hygiene and making certain changes to your lifestyle.
Brushing and flossing daily can significantly reduce the risk of dental caries. Both brushing and flossing prevent the formation of dental plaque. Plaque is a layer of bacteria that sticks to the surfaces of the teeth. Bacteria present in the plaque break down carbohydrates and produce acid by fermentation. This acid destroys the tooth surface and causes the formation of caries. Brushing removes the plaque from the tooth surfaces. However, since the bristles of a toothbrush cannot reach the gaps between the teeth, brushing is ineffective against plaque hidden there. Dental floss removes plaque hidden between the gaps of the teeth. Therefore, the combination of brushing and flossing is very effective against dental caries.
Using a medicated mouthwash is also suggested. Mouthwashes contain antibacterial agents and essential oils that act against bacterial populations in the mouth. Swishing mouthwash physically dislodges food particles that are stuck in the gaps between the teeth. Using a mouthwash twice daily along with brushing and flossing can almost entirely eliminate the risk of dental caries.
Taking foods rich in sugar increases the risk of dental caries. In the absence of sugars, the bacteria of the mouth cannot produce acid by fermentation. Minimizing foods rich in sugars and other carbohydrates prevents dental caries to a large extent. Sticky foods such as candy, potato chips and crackers should also be avoided. Similarly, aerated drinks or soda should also be avoided.
Some studies indicate that taking crunchy vegetables and fruits can be beneficial in preventing dental caries. This is because the fiber present in these foods physically dislodges the plaque from forming. Certain foods like milk and cheddar cheese have also been found to be beneficial if taken immediately after taking foods that are harmful to the teeth. These foods are believed to regulate the pH and prevent bacterial action. Foods rich in calcium, phosphorus and vitamin D make the teeth stronger and more resistant to dental cavities.
Dental sealants: A dental sealant is a plastic like coating that is applied to the teeth to prevent food particles from accumulating in the pits and fissures. Dental sealants are applied by a dentist and should be checked regularly as they are prone to wear and fail. Sealants are usually applied to children’s teeth as soon as they arrive. However, they can also be applied to teeth of adults.
Fluoride: Fluoride prevents teeth decay by binding with hydroxyapatite crystals present in the enamel of the teeth. Fluoride acts as a bacteriostatic agent in low concentrations. In higher concentrations, it kills bacteria directly. Fluoride makes the enamel more resistant to demineralization. Most toothpastes and mouthwashes available in the market contain fluoride. Many dentists apply topical fluoride solutions as part of routine visits.
Treatment of dental caries
If dental caries are detected in earlier stages, remineralization is possible by making certain changes to the diet, improving oral hygiene and regular application of fluoride. Treatment is possible without drilling on the tooth. This treatment approach is known as non-operative treatment.
Once a cavity is formed, remineralization is more difficult and operative treatment may be required. The tooth is drilled to remove all the portion that has decayed. Sometimes a small portion of the decay is left intact if there is a seal between the bacteria and the underlying substrate. Measures are taken to avoid the exposure of the dental pulp and minimize the amount of tooth surface which needs to be removed before the filling is placed. Damaged tooth structures do not regenerate but remineralization is possible to some extent. For smaller cavities, topical fluoride may be applied to encourage remineralization.
Drilling and filling are performed under local anesthesia. Nitrous oxide, commonly known as laughing gas, and other prescription medications may be used to relieve the pain during or after treatment and to reduce anxiety during the treatment. A dental drill is used to cut and remove the decayed portion of the tooth. A dental instrument known as the spoon is used to remove decay especially when the decay reaches near the pulp. Once the decayed portion is removed, dental restoration is performed to return the tooth to function and appear like normal.
Restoration is done using dental amalgam, porcelain, composite resin or gold. Porcelain and composite resin can be made to match the color of natural teeth and are more frequently used when appearance is not a concern. However, composite resins are not as strong and durable as dental amalgam and gold.
When the decay is too extensive, enough tooth structure may not be available for application of restorative material. In such a situation, a crown may be needed. A crown is like a cap that is fitted over the remainder of the natural tooth. Crowns may be made of gold, porcelain or metal.
In some cases, root canal treatment is necessary for restoration of the decayed tooth. Root canal treatment is performed if the pulp of the tooth is destroyed due to decay. In this treatment, the pulp of the tooth along with the nerves and vascular tissue is removed and filled with a rubber like material known as gutta percha. The tooth is then filled and a crown is put in place.
If tooth decay is too extensive and restoration is not possible, extracting the tooth may be a treatment option. Extraction may also be preferred by people who do not want to undergo the expense of restoring the tooth.
Long term effects of dental caries
If dental caries are not arrested in early stages, the resulting damage is not reversible. Tooth decay can lead to infection of other teeth and gums and result in tooth loss. It can also affect the growth of the body and cause deficiency diseases. There is also a growing body of research that indicates that dental caries and gum inflammation can increase the risk of cardiovascular diseases and diabetes.