Until caries progresses, a person may not be aware of it. The earliest sign of a new carious lesion, referred as incipient decay, is the appearance of a chalky white spot on the surface of the tooth, indicating an area of demineralization of enamel. As the lesion continues to demineralize, it can turn brown but will eventually turn into a cavitation, a "cavity". The process before this point is reversible, but once a cavitation forms, the lost tooth structure cannot be regenerated. A lesion which appears brown and shiny suggests dental caries was once present but the demineralization process has stopped, leaving a stain. A brown spot which is dull in appearance is probably a sign of active caries.
As the enamel and dentin are destroyed further, the cavitation becomes more noticeable. The affected areas of the tooth change color and become soft to the touch. Once the decay passes through enamel, the dentinal tubules, which have passages to the nerve of the tooth, become exposed and cause the tooth to hurt. The pain can be worsened by heat, cold, or sweet foods and drinks. Dental caries can also cause bad breath and foul tastes. In highly progressed cases, infection can spread from the tooth to the surrounding soft tissues which may become life-threatening, as in the case with Ludwig's angina.
Causes of caries formation
There are four main criteria required for caries formation: a tooth surface (enamel or dentin); cariogenic (or potentially caries-causing) bacteria; fermentable carbohydrates (such as sucrose); and time. The caries process does not have an inevitable outcome, and different individuals will be susceptible to different degrees depending on the shape of their teeth, oral hygiene habits, and the buffering capacity of their saliva. Dental caries can occur on any surface of a tooth that is exposed to the oral cavity, but not the structures which are retained within the bone.
The minerals in tooth enamel, especially hydroxyapatite, will become soluble when exposed to acidic environments. Enamel begins to demineralize at a pH of 5.5. Dentin and cementum are more susceptible to caries than enamel because they have lower mineral content. Thus, when root surfaces of teeth are exposed from gingival recession or periodontal disease, caries can develop more readily. Even in a healthy oral environment, the tooth is susceptible to dental caries.
The anatomy of teeth may affect the likelihood of caries formation. In cases where the deep grooves of teeth are more numerous and exaggerated, pit and fissure caries are more likely to develop. Also, caries are more likely to develop when food is trapped between teeth.
Bacteria which are tiny colonies of living organisms are constantly found in the human mouth. It is normal for millions of bacteria to be in your mouth. The mouth contains a wide variety of bacteria, but only a few specific species of bacteria are believed to cause dental caries: Streptococcus mutans and Lactobacilli among them. Particularly for root caries, the most closely associated bacteria frequently identified are Lactobacillus acidophilus, Actinomyces viscosus, Nocardia spp., and Streptococcus mutans. Mutans streptococci are able to grab any sugar that enters the mouth. Bacteria in a person's mouth convert sugars (glucose and fructose, and most commonly sucrose - or table sugar) into acids such as lactic acid through a glycolytic process called fermentation. This changes the pH in the mouth and forms acid on the teeth. It is this acid that causes teeth to decay. The lactobacilli are more able to survive in an acid environment. Bacteria changes all foods into acid. Sugars and starches are favourites of bacteria. Plaque is formed by bacteria, acid, food debris, and saliva. Plaque is a sticky substance that sticks to the teeth. Plaque is easily detected on the grooved chewing surfaces of the back molars, just above the gum line, and at the edges around fillings. When plaque is not removed from the teeth it becomes tartar.
There is acid in the plaque. It is this acid that dissolves the enamel surface of the tooth and creates holes in the tooth. Most of the bacterial activity occurs within twenty minutes after eating. This is when the acid is most active. The bacteria multiply faster and the plaque grows in size and thickness. This makes it harder to wash the bacteria away with saliva. Bacteria will use the sugars found in candy and other sweet foods as well as the natural sugars found in fruits and milk. They also use the carbohydrates found in potato chips, pasta, and bread.
Our teeth are able to repair the damage done to the enamel by the acid in a process called remineralization. The minerals found in the saliva try to repair the damaged areas of the tooth surface. But, the rate of destruction of the tooth enamel by acid is much faster than the natural remineralization that occurs.
If left in contact with the tooth, these acids may cause demineralization, which is the dissolution of its mineral content. The process is dynamic, however, as remineralization can also occur if the acid is neutralized; suitable minerals are available in the mouth from saliva and also from preventative aids such as fluoride toothpaste, dental varnish or mouthwash. Caries advance may be arrested at this stage.
Prevention of caries
Personal hygiene care consists of proper brushing and flossing daily. The purpose of oral hygiene is to minimize any etiologic agents of disease in the mouth. The primary focus of brushing and flossing is to remove and prevent the formation of plaque. Plaque consists mostly of bacteria. As the amount of bacterial plaque increases, the tooth is more vulnerable to dental caries. A toothbrush can be used to remove plaque on most surfaces of the teeth except for areas between teeth. When used correctly, dental floss removes plaque from areas which could otherwise develop proximal caries. Other adjunct hygiene aids include inter-dental brushes, water picks, and mouthwashes.
Professional hygiene care consists of regular dental examinations and cleanings. Sometimes, complete plaque removal is difficult, and a dentist or dental hygienist may be needed. Along with oral hygiene, radiographs may be taken at dental visits to detect possible dental caries development in high risk areas of the mouth.
For dental health, the frequency of sugar intake is more important than the amount of sugar consumed. In the presence of sugar and other carbohydrates, bacteria in the mouth produce acids which can demineralize enamel, dentin, and cementum. The more frequently teeth are exposed to this environment, the more likely dental caries are to occur. Therefore, minimizing snacking is recommended, since snacking creates a continual supply of nutrition for acid-creating bacteria in the mouth. Also, chewy and sticky foods (such as dried fruit or candy) tend to adhere to teeth longer, and consequently are best eaten as part of a meal. Brushing the teeth after meals is recommended.
It has been found that milk and certain kinds of cheese like cheddar can help counter tooth decay if eaten soon after the consumption of foods potentially harmful to teeth. Also, chewing gum containing xylitol (wood sugar) is widely used to protect teeth in some countries, being especially popular in the Finnish candy industry. Xylitol's effect on reducing plaque is probably due to bacteria's inability to utilize it like other sugars. Chewing and stimulation of flavour receptors on the tongue are also known to increase the production and release of saliva, which contains natural buffers to prevent the lowering of pH in the mouth to the point where enamel may become demineralised.
Fluoride therapy is often recommended to protect against dental caries. It has been demonstrated that water fluoridation and fluoride supplements decrease the incidence of dental caries. Fluoride helps prevent decay of a tooth by binding to the hydroxyapatite crystals in enamel. The incorporated fluoride makes enamel more resistant to demineralization and, thus, resistant to decay. Topical fluoride is also recommended to protect the surface of the teeth. This may include a fluoride toothpaste or mouthwash. Many dentists include application of topical fluoride solutions as part of routine visits.
Furthermore, recent research shows that low intensity laser radiation of argon ion lasers may prevent the susceptibility for enamel caries and white spot lesions. Also, as bacteria are a major factor contributing to poor oral health, there is currently research to find a vaccine for dental caries. As of 2004, such a vaccine has been successfully tested on non-human animals, and is in clinical trials for humans of May 2006.
Tooth decay prevention
There are several things that can be done to prevent tooth decay. The timing of your snacks is critical to preventing cavities. After snacking the acid that is produced is neutralized by the saliva and is cleared from the mouth. After the acid is removed the minerals present in saliva crystallize on the enamel and begin to repair the areas that were damaged by the acid. The longer the interval between meals and snacks provides more opportunity for the acid to be neutralized and more time for the damage to be repaired. When frequent snacking takes place there is a constant attack on the tooth surface by the acid. There is also less time for tooth repair to take place.
Fluoride has been called a wonder of modern dentistry. It incorporates itself into the enamel of the tooth and strengthens it and makes it more resistant to attacks by acid. Fluoride works with the saliva in the mouth to restore, or remineralise the decayed spot on the tooth. The pH level in the mouth is lower after eating. It is during this time that fluoride is able to reduce the activity of the mutans streptococci. Fluoride is found in many tooth cleaners as well as being applied to the teeth by the dentist at regular visits.
There are many toothpastes that promise better results in cleaning tooth surfaces as well as helping to control plaque growth and tartar control. The cleaning power of a toothpaste depends on its ability to remove stains from the surface of the tooth. Toothpastes contain gentle abrasives to help clean tooth surfaces. Most toothpastes contain fluoride. Some use stannous fluoride while others use sodium fluoride or sodium monofluoroshosphate. Tartar control toothpastes contain pyrophosphates to slow the build-up of tartar above the gumline. The most important factors to reduce the build-up of plaque on tooth surfaces is regular brushing, twice a day and flossing to remove debris that is between the teeth.
Measures of Hardness
There are many different aspects of materials which could be considered as a measure of hardness. Hardness can mean resistance to scratching, indentation, bending, breaking, abrasion, cleavage, or fracture. It is easy to confuse durability or toughness with hardness. A very simple example is to consider a glass ball and a rubber ball. Glass is harder than rubber, but rubber is more durable. Try bouncing both on a hard floor, the glass ball will shatter, whereas the rubber ball will bounce. The aspect of hardness which is measured by Moh's test is the scratchability of a mineral.
In 1822, Friedrich Moh, a German mineralogist devised a crude but practical method of comparing hardness or scratch resistance of minerals. It has become universally known as Moh's scale.
It should more accurately be called a table, because it is not to scale, that is the numbers allocated to different minerals are not proportional to their actual scratch resistance, so that the scale is really an ordered list.
Moh took ten well known, easily available minerals, and arranged them in order of their "scratch hardness". If a specimen to be tested can be scratched by a known mineral from the list, it is softer than that mineral. If it in turn will scratch another known mineral, it is harder than that mineral. This gives a very quick and easy field test for hardness. As such is it very useful for mineralogists. It is too destructive to be commonly used in gemmology, but is available, and can be valuable on rough gemstones.
A modern toothpaste has much more ingredients than those some years ago. New toothpaste ingredients have been introduced in order to provide effective protection against various dental conditions.
The most common active ingredients in toothpastes are :
This is the most popular active ingredient in toothpaste due to its proved ability to prevent cavities. Fluoride incorporates itself into tooth enamel making your teeth more resistant to acids produced by plaque bacteria, as well as acids found in fruit juices, soda (both regular and diet) and certain foods.
Most toothpaste brands use Sodium fluoride (NaF); some brands use Sodium Monofluorophosphate - SMFP (Na2PO3F). The concentration of fluoride in a toothpaste for adults is 1000 to 1450 ppm max.
2. Antimicrobial agents
These fight the bacteria of dental plaque. There are two kinds of antibacterial agents used as ingredients of toothpastes :
- bactericidal agents as Triclosan that kill bacteria. Triclosan induces damage and lesions to the cell wall of bacteria resulting in bacteriolysis (death of the cell).
- bacteriostatic agents as Zinc (Zinc chloride or Zinc citrate) that stop the growth of dental plaque bacteria by inhibiting their metabolism.
The combination of a bacteriostatic with a bactericidal agent as toothpaste ingredients is the most effective one to fight dental plaque and gum disease.
3. Surfactants (detergents) and Foaming agents
These help to carry away debris from the mouth and between the teeth. Foam keeps the toothpaste in our mouths, preventing it from dribbling out as we brush. Common foaming ingredients in toothpastes are Sodium Lauryl Sulfate (SLS) and ammonium lauryl sulfate. Unfortunately, SLS and other detergents have been linked to the promotion of canker sores (mouth ulcers) in susceptible individuals. The presence of bad-tasting detergents requires the use of strong flavorings to mask the bad taste.
4. Anti-tartar agents as Tetrasodium Pyrophosphate (TSPP).
Pyrophosphates are water-softening agents that remove calcium and magnesium from the saliva, so they can't deposit on teeth creating tartar (calcified plaque). Pyrophosphate does not remove tartar, it merely helps prevent its formation.
5. De-sensitising agents to relieve tooth sensitivity.
Strontium chloride works by blocking the tiny crevices (microtubules) that enable cold and heat sensations to reach the tooth's nerve. Potassium citrate and Potassium nitrate work in a different way by blocking the mechanism of pain transmission between nerve cells.
Abrasives give toothpaste its cleaning power. They remove stains and plaque, as well as polish teeth. Toothpaste should be abrasive enough to remove plaque and stains, but not abrasive enough to damage tooth enamel. Unfortunately, some toothpastes are too abrasive, and do damage tooth enamel. This leads to tooth sensitivity. Damaged tooth enamel also causes yellowing as the thinned enamel reveals the yellowish dentin layer below. Calcium phosphate (chalk) and alumina were used as the abrasive base of tooth pastes but they had the disadvantage of reacting with other chemical ingredients. Today the common abrasives are Silicon Dioxide (silica) and Titanium Dioxide. Hydrated silica is a transparent abrasive used not only in white opaque tooth pastes, but in gel toothpastes as well.
Baking Soda (Sodium bicarbonate) is a mild abrasive. It has a mild whitening action and helps to keep an alkaline environment (not friendly for dental plaque bacteria) in the mouth.
7. Teeth Whitening agents
The whitening toothpastes, except of the mechanical whitening action of toothpaste abrasives, use extra whitening ingredients as the Hydrogen Peroxide or Sodium carbonate peroxide that breaks down into sodium carbonate (washing soda) and hydrogen peroxide.
Toothpastes come in a variety of flavours, most often being some variation on mint. These are added to improve the taste of toothpaste. You may have noticed that toothpastes often have very strong flavouring. This is necessary to cover up the horrid taste of most detergents, especially SLS.
Humectants give toothpaste its texture as well as retain moisture so that your toothpaste does not dry out. Glycerin, sorbitol, and water are common humectants. Xylitol is an uncommon, but superior humectant, which also boosts fluoride's cavity-fighting power.
Thickeners also help to create the texture of toothpaste and determine how 'thick' your toothpaste is. Carrageenan, cellulose gum, and xanthan gum are common thickening agents.
Preservatives prevent the growth of micro-organisms in toothpaste. This eliminates the need to refrigerate toothpaste. Common preservatives include sodium benzoate, methyl paraben, and ethyl paraben.
Sweeteners also improve the taste of toothpaste. Most toothpaste sweeteners are artificial and contribute very little to cavity formation. Saccharin is a common toothpaste sweetener.
13. Colouring Agents
Some toothpastes would look down right disgusting if it were not for colouring agents. Colouring agents provide toothpaste with pleasing colours. Artificial dyes are used to make red, green, and blue toothpastes. Titanium dioxide is used to make some toothpastes white.