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Dental caries
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Dental caries (Latin, "rot"), also known as tooth decay or a cavity,
is an infection, bacterial in origin,
that causes demineralization and
destruction of the hard tissues of the teeth (enamel, dentin and cementum). It is a result of the production of acid by bacterial fermentation of food debris accumulated on the tooth
surface. If demineralization exceeds saliva and other
remineralization factors such as from calcium and fluoridated toothpastes,
these once hard tissues progressively break down, producing dental caries (cavities
or carious lesions, that is, holes in the teeth). Today, caries
remains one of the most common diseases throughout the world.
Cariology is the study of dental
caries.
Signs and
symptoms
(A) A small spot of decay visible on the surface of a tooth. (B)
The radiograph reveals an extensive region of demineralization within the
dentin (arrows). (C) A hole is discovered on the side of the tooth at
the beginning of decay removal. (D) All decay removed.
Discovery and History
In 1924 in
London, Killian Clarke described a spherical
bacterium in chains isolated from carious lesions which he called Streptococcus mutans.
Although Clarke proposed this organism was the cause of caries the discovery
was not followed up. Later, in the 1950s in the USA,
Keyes and Fitzgerald working with hamsters
showed that caries was transmissible and caused by an
acid-producing Streptococcus. It was not until the late 1960s
that it became generally accepted that the Streptococcus isolated from
hamster caries was the same as S. mutans described by Clarke.
A
person experiencing caries may not be aware of the disease. The earliest sign
of a new carious lesion is the appearance
of a chalky white spot on the surface of the tooth, indicating an area of demineralization of enamel. This is referred to as a
white spot lesion, an incipient carious lesion or a "microcavity". As
the lesion continues to demineralize, it can turn brown but will eventually turn into a cavitation
("cavity"). Before the cavity forms,
the process is reversible, but once a cavity forms, the lost tooth structure
cannot be regenerated. A lesion that appears dark brown and shiny
suggests dental caries were once present but the demineralization process has
stopped, leaving a stain. Active decay is lighter in color and dull in
appearance.
As the enamel
and dentin are destroyed, the cavity 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, resulting in pain that can be transient, temporarily
worsening with exposure to heat, cold, or sweet foods and drinks. A tooth
weakened by extensive internal decay can sometimes suddenly
fracture under normal chewing forces. When the decay has progressed
enough to allow the bacteria to overwhelm the pulp tissue in the center of the
tooth a toothache can result and the pain will become 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. Complications such as cavernous
sinus thrombosis and Ludwig angina can be life-threatening.
Causes of Dental caries
There are four main criteria required for caries formation:
2-
caries-causing bacteria,
4-
time.
The bacteria most responsible for
dental cavities are the mutans streptococci, most prominently Streptococcus
mutans
and Streptococcus sobrinus, and lactobacilli. If left untreated, the disease can lead to pain, tooth loss and infection.
Tooth
decay disease is caused by specific types of bacteria that produce acid in the presence of fermentable carbohydrates such as sucrose, fructose, and glucose. The mineral content of teeth is
sensitive to increases in acidity from the production of lactic acid. To be specific, a tooth
(which is primarily mineral in content) is in a constant state of
back-and-forth demineralization and remineralization between the tooth and surrounding saliva.
All caries occur from bacterial acid
demineralization that exceeds saliva and fluoride remineralization, and acid
demineralization occurs where bacterial plaque is left on teeth. Areas that are
easily cleansed with a toothbrush, such as the front and back surfaces (facial
and lingual), develop fewer cavities.
Bacteria
The mouth contains a wide variety of oral bacteria,
but only a few specific species of bacteria are believed to cause dental
caries: Streptococcus mutans and Lactobacilli among them. These organisms can produce high levels of
lactic acid following fermentation of dietary sugars, and are resistant to the
adverse effects of low pH, properties essential for cariogenic bacteria. As the
cementum of root surfaces is more easily demineralized than enamel surfaces, a
wider variety of bacteria can cause root caries including Lactobacillus
acidophilus, Actinomyces spp., Nocardia spp., and Streptococcus mutans. Bacteria collect around the teeth and gums in a sticky,
creamy-coloured mass called plaque,
which serves as a biofilm. Some sites collect plaque more commonly than others, for
example sites with a low rate of salivary flow (molar fissures). Grooves on the
occlusal surfaces of molar
and premolar
teeth provide microscopic retention sites for plaque bacteria, as do the
interproximal sites. Plaque may also collect above or below the gingiva
where it is referred to as supra- or sub-gingival plaque, respectively.These
bacterial strains, most notably S. mutans can be inherited by a child
from a caretaker's kiss or through feeding premasticated food.
Fermentable carbohydrates
Bacteria in a person's mouth convert
glucose,
fructose,
and most commonly sucrose (table sugar) into acids such as lactic acid
through a glycolytic process called fermentation.[14]
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 by saliva or mouthwash. Fluoride toothpaste or
dental varnish may aid remineralization.
If demineralization continues over time, enough mineral content may be lost so
that the soft organic material left behind disintegrates, forming a cavity or
hole.
Prevention:-
Oral hygiene
Personal hygiene care
consists of proper brushing and flossing daily.[2] 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 or dental biofilm. Plaque
consists mostly of bacteria As the amount of bacterial plaque increases, the
tooth is more vulnerable to dental caries when carbohydrates in the food are
left on teeth after every meal or snack. A toothbrush can be used to remove
plaque on accessible surfaces, but not between teeth or inside pits and
fissures on chewing surfaces. When used correctly, dental floss removes plaque
from areas that could otherwise develop proximal caries but only if the depth
of sulcus has not been compromised. Other adjunct oral hygiene aids include interdental brushes, water picks, and mouthwashes.
Professional hygiene care
consists of regular dental examinations and professional prophylaxis
(cleaning). 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 (e.g. "bitewing" x-rays which
visualize the crowns of the back teeth).
Common dentistry trays used to
deliver fluoride. Fluoride is
sold in tablets for cavity prevention.
Calcium, as found in food such as milk and green vegetables,
is often recommended to protect against dental caries. Fluoride helps prevent
decay of a tooth by binding to the hydroxyapatite crystals in enamel. The
incorporated calcium makes enamel more resistant to demineralization and, thus,
resistant to decay. Topical fluoride is now more highly recommended than
systemic intake such as by tablets or drops to protect the surface of the
teeth. This may include a fluoride toothpaste
or mouthwash or varnish. After brushing with fluoride toothpaste, rinsing
should be avoided and the excess spat out instead. This leaves a greater
concentration of fluoride residue on the teeth. Many dental professionals
include application of topical fluoride solutions as part of routine visits and
recommend the use of xylitol and Amorphous
calcium phosphate products. Vaccines
are also under development.
An amalgam used as a restorative material in a tooth.
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