Dental Cavities

• What are the causes of cavities?
• How can cavities be prevented?
• How are cavities filled?

Dental cavities (caries) are holes in the two outer layers of a tooth called the enamel and the dentin. The enamel is the outermost white hard surface and the dentin is the yellow layer just beneath enamel. Both layers serve to protect the inner living tooth tissue called the pulp, where blood vessels and nerves reside. Dental cavities are common, affecting over 90% of the population. Small cavities may not cause pain, and may be unnoticed by the patient. The larger cavities can collect food, and the inner pulp of the affected tooth can become irritated by bacterial toxins, foods that are cold, hot, sour, or sweet-causing toothache. Toothache from these larger cavities is the number one reason for visits to dentists.
What are the causes of cavities?

Cavity-causing bacteria in the mouth consume simple sugars, converting them into acid plaque. Acid plaque is different from the periodontal plaque that causes "Gum Disease." The acid plaque produced by these bacteria cause the hard inorganic layers of the enamel and dentin to soften. The softened layers are then dissolved by saliva, leaving a hole (cavity) in the tooth. Unless filled by a dentist, the cavity can continue to erode and damage the inner pulp of the tooth. Damage to the pulp can lead to pulp death, infection and tooth abscess. Therefore, pulp damage will necessitate either tooth extraction or a root canal procedure where the dying pulp is removed and replaced with an inert material.
The enamel on baby teeth are immature and porous. It takes seven years for the porous, chalky enamel to be replaced by more mature, dense, hard, shiny enamel. Therefore children are more prone to cavities than adults.
Cavity-causing bacteria are difficult to eradicate because they are very similar to the other harmless bacteria that live in the oral cavity. The many cavity-causing bacteria include:

1. Lactobacillus acidophilus bacteria reside in the pits and fissures of the chewing (occlusal) surfaces of teeth. These bacteria can cause rampant tooth decay in young children ages 3-12, causing cavities in both baby teeth and the first permanent molars that erupt around age 6.
2. Six species of streptococcus bacteria attack the smooth surfaces on the sides of the teeth. These sides are usually touching adjacent teeth, and cavities arising on these sides can be difficult to detect visually. These cavities are best detected by the use of x-rays.
3. Odontomyces viscoses bacteria live on the back of the tongue and attack exposed cementum. Cementum is the hard outer layer of the tooth root (the bottom two thirds of tooth that is normally buried in dental bone). In older patients and in patients with gum disease, the tooth root and cementum become exposed and vulnerable to attack by these bacteria.

How can cavities be prevented?

The number of cavities can be reduced by proper nutrition, good oral hygiene, fewer snacks in between meals, the use of oral or topical fluorides, and topical sealants.

1. Nutritional counseling - consuming less simple sugar (sucrose or table sugar) will reduce the number of acid- producing bacteria in the mouth. Adequate dietary calcium, phosphorous, vitamins A, D, and C promote healthy and strong enamel formation.
   
   
2. Home oral hygiene - brushing your teeth frequently helps reduce acid plaque damage to enamel, while frequent flossing removes the acid plaque from the smooth surfaces between teeth. If one cannot brush and floss immediately after a meal, he/she should try chewing self-cleaning foods at the end of the meal. These include apples and celery that are crunchy and help sweep away food debris and plaque. Chewing sugarless gum for a few minutes at the end of a meal can also help.
   
   
3. Eating fewer snacks in between meals - every snack is followed by an "acid attack" on the teeth. Therefore, snacking all day causes the teeth to be bathed in acid continuously. Fewer snacks and eating desserts only with meals help to reduce the number of "acid attacks" on teeth.
   
   
4. Fluorides - oral fluorides (fluoride tablets or fluoridated water) strengthen the developing enamel and dentin layers of children's teeth before they erupt. Topical fluorides fill in the pores of immature enamel or small early cavities and reduce cavities in already erupted teeth. Topical fluorides are usually painted on by the dentist, and later supplemented at home with topical fluoride gels.
   
   
5. Sealants - sealants are plastic coatings painted on the pits and fissures of chewing surfaces of back teeth (molars and bicuspids), and are highly effective in preventing cavities. Sealants are recommended for all permanent molars in children. They are also used to reduce cavities in baby teeth and in adult teeth that are cavity prone. The procedure is simple and painless, and no anesthesia is required

How are cavities filled?

Before a dentist can fill a cavity, it must be thoroughly cleaned by hand instruments and mechanical rotary instruments, called handpieces. The clean cavity is then filled with either dental amalgam, composite material, gold, or porcelain to restore the tooth to its original shape and size.
The most economical, time-honored material is the silver filling (also known as dental amalgam). It is composed of silver, tin, traces of metallic mercury, and other compounds. Dental amalgam has been used safely in dentistry for nearly 150 years. While some people have raised concerns over the health effect of mercury in the dental amalgam, the actual amount of metallic mercury in dental amalgam is less than the mercury found in seafood or polluted air. Swedish and American scientists could find no correlation between having new silver fillings and changes in the levels of mercury in the blood or urine. The American Dental Association still supports dental amalgam as a safe and effective filling material, especially for the cavities on the chewing surfaces of back teeth (bicuspids and molars). The amalgam can be a health problem if the patient has a true allergy to mercury (true allergy to mercury is rare, and the condition must be ascertained by a physician).
An alternative to amalgam is the use of composites. Composites are plastic resins mixed with quartz fillers or other hard minerals for strength. Composites are widely used to fill cavities in the front teeth because they come in various shades that match the natural tooth color. However they are less suitable for cavities in the back teeth because they are softer than amalgam and more prone to wear down and chip with chewing. If the composites are inadequately "cured" with the special composite light, leakage of bacteria and saliva can occur under the filling. Such leakage causes tooth sensitivity to cold and sweets. Leakage also causes the decay process to recur under and around the composite filling, causing subsequent fracture of the tooth.
Gold is an excellent material for filling teeth. It has good wear compatibility to the enamel of opposing and adjacent teeth. Gold adapts very well to the edges of a cavity and is totally inert or nontoxic. However gold is expensive, is unsightly in color, and is technically challenging to use. Therefore, gold fillings are rarely performed anymore.
A new filling material that is increasing in popularity is porcelain. Even though it is almost as expensive as gold, the color of porcelain filling can be matched to the natural tooth color. Two appointments are necessary to perform the porcelain filling. During the first appointment, the dentist cleans the cavity and takes an impression of the tooth. A dental laboratory then creates a stone model of the tooth and fabricates the porcelain filling from the tooth model. The porcelain filling is then cemented or "bonded" onto the tooth during a second appointment with the dentist.
source;medicinenet.com