Dental Caries is an infectious microbial disease that results in localized dissolution and destruction of calcified tissues of the teeth. The enzymes produced by the bacteria act upon the fermentable carbohydrates to produce acids. These acids react with the enamel leading to dental caries as a result of demineralization.
Tooth decay, also known as dental caries or cavities, is a disease that causes the breakdown of tooth enamel.
Once tooth decay has eroded the enamel, cavities can start to form.
Epidemiology :-
Dental caries may be considered a disease of modern civilization. Studies revealed that the skulls of men from Pre Neolitic period (12,000 BC) did not exhibit dental caries but skulls from Neolithic period (12.000 to 3000 BC) contained carious teeth. Dental caries was also found in the skulls of Neanderthal age (3000 BC-750 BC). Evidence of caries was found in about one half of the 24 skulls of the prehistoric race, which lived in Central Europe about 15,000 years ago.’
FIOLOGY OF DENTAL CARIES :-
Theories :
1) The Legend of the Worm
The earliest reference to tooth decay and toothache came from the ancient Sumerian text known as “The Legend of the Worm’. It was obtained from the Mesopotamian areas which dates to about 5000B.C.The early history of India, Egypt and the writing of Homer also makes reference to the worm as the cause of toothache. Chinese and Egyptians used fumigation devices for treatment of dental caries,
2. Endogenous Theories :-
1. Humoral Theory:
The four humors of the body were blood, phlegm, black bile and yellow bile. According to Galen, the ancient Greek physician and philosopher, “dental caries is produced by internal action of acrid and corroding humors”. Hippocrates, the father of medicine, while favouring the concept of humoral pathology, also referred to the accumulated debris around teeth and to their corroding action. He also stated that stagnation of juices in the teeth was the cause of toothache.
2. Vital Theory:
Proposed during the 18th century. According to this theory it is postulated that tooth decay originated like bone gangrene, from within the tooth itself.
3. Exogenous theories :-
Chemical (Acid) Theory:
In the 17th and 18th, there emerged the concept that teeth were destroyed by acids formed in the oral cavity by fermentation of food particles around teeth.
2. Parasitic (Septic) Theory:
Indicated that microorganisms were associated with the carious process.
3. Miller’s Chemicoparasitic Theory (Acidogenic theory):
This theory was proposed by W.D. Miller in 1890. The microorganisms found in the oral cavity produce enzymes that act upon the fermentable carbohydrates to produce acids (like lactic acid, butyric acid, formic acid, succinic acid). These acids act upon the enamel of the tooth resulting in its demineralization leading to dental caries.”
4. Proteolysis Theory:
Proposed by Gottileb in 1934. According to this theory, the organic matrix would be attacked, before the mineral phase of the enamel. The proteolytic enzymes liberated by the oral bacteria destroy the organic matrix of enamel, loosening the apatite crystals, so they are eventually lost and tissue collapses.
5. Proteolysis Chelation Theory: Originated by Schatz & Martin in 1955. It proposes that some of the products of bacterial action on enamel, dentin, and salivary constituents can form chelates with calcium. Since chelates can be formed at neutral or alkaline ph, the theory suggested that demineralization of the enamel could arise without acid formation.
According to the American Dental Association (ADA), a tooth consists of 3 layers :-
Enamel:
Enamel is the hard outer layer that protects the inner layers of a tooth. Tooth enamel contains no living cells and is the hardest structure in the human body.
Dentin:
Dentin is the second layer of a tooth. When the enamel is damaged, it may expose the dentin. Small tubes within the dentin allow hot and cold food to stimulate the nerves of the tooth. The stimulation of these nerves can cause pain and sensitivity in the tooth.
Pulp:
The pulp is the center of the tooth. The pulp contains blood vessels, nerves, and connective tissue.
Tooth decay can occur in varying degrees of severity. Damage from tooth decay can range from causing wear to the enamel to painful abscesses within the pulp of the tooth.
Symptoms : –
Symptoms of tooth decay can vary depending on the severity of the damage caused.
According to the National Institute of Dental & Ceaniofacial Research Trusted Source some people in the early stages of tooth decay may feel no symptoms. However, as tooth decay advances, a person may experience the following:
•Tooth sensitivity to sugary, hot, or cold food
•Constant tooth pain
•White or dark spots on the teeth
•Bad breath
•Loose fillings
•Cavities in teeth
•Food frequently trapped in teeth
•Difficulty biting certain foods
•Abscesses on teeth that cause pain, facial swelling, or fever.
EPIDEMIOLOGICAL TRIAD
Host factors
Tooth: Composition:
The enamel consists of 96% inorganic matter and 4% water and organic. The dentine consist of 35% of organic matter and water and 65% of inorganic matter. The cementum consists of 45to 50% of inorganic matter and 50 to 55% of organic matter and water.
Morphology:
Presence of deep, narrow, occlusal fissures or buccal and lingual pits tend to trap food, bacteria and debris. Since defects are common in the base of fissures, caries may develop rapidly in these areas. Conversely, as attrition advances, the inclined planes become flattened, providing less opportunity for entrapment of food in the fissures and caries predisposition diminishes. Alteration of tooth structure by disturbance in formation or in calcification is of only secondary importance in dental caries. The rate of caries progression may be influenced, but initiation of caries is affected very little.
2. Saliva:
It helps in removal of bacteria & food debris by its flushing action. The quantities of inorganic and organic constituents of saliva varies from person to person.
Calcium and Phosporous:
The quantity of calcium and phosporous is inversely related to the rate of flow. Its quantity is less in case of caries active individuals.
Ammonia:
As the quantity of ammonia decreases, caries activity increases, because ammonia retards plaque formation and neutralizes acid.
Urea:
Urea gets hydrolyzed to ammonium carbonate by urease which has a neutralizing effect.
Pryalin and amylase:
Help in the degradation of starches.
pH of saliva:
The pH of saliva depends on its bicarbonate content .As the flow rate of saliva increases the pH also increases. Saliva may be slightly acidic as it is secreted at unstimulated flow rates but it may reach a pH of 7.8 at high flow rates. Quantity of saliva secreted normally is 700 to 800 ml/day. As the viscosity of saliva increases the caries activity also increases. The saliva also contains a number of antibacterial substances or enzymes like lactoperoxidase, lysozyme, lactoferrin, and IgA.3
3. Sex:
Most of the studies have shown that dental caries is more common in females
4. Race:
Dental caries is more in whites compared to the blacks.
5. Age:
Though dental caries is considered to the disease with universal prevalence, it is more commonly seen in childhood. Over 60 years of age, root caries is seen which is mainly due to gingival recession and deterioration of oral clearance ability.
6. Familial heredity:
Inheritance of a characteristic tooth structure has lesser influence than environmental factors.
7. Developmental disturbances:
The presence of deep pits & fissures, enamel hypoplasia and enamel defects make the tooth more prone to dental caries.
8. Economic status:
In young primary school children dental caries decreases with increase in income. Among adults as income decreases there is decrease in dental caries.
9. Concomitant disease:
Dental caries is found to be less in controlled diabetes.
10. Oral hygiene habits:
Dental caries is found
to be less among those who maintain good oral hygiene.
H. Agent Factors :-
Consists of dental plaque forming streptococci (Streptococcus mutans).
Roleof Micro Oganisms in caries
1. They are a prerequisite for caries initiation.
2. A single type of micro organism is capable of inducing caries.
3. Acid production is a prerequisite for caries, but not all acidogenic organisms are cariogenic.
4. Streptococcus strains produce extracellular dextrans or levans.
5. Organisms vary greatly in their capacity to induce caries.
Properties of cariogenic plaque
1. The rate of sucrose consumption was higher.
2. Synthesize more intracellular poly- saccharides.
3. More lactic acid is formed.
4. Twice as much as extracellular saccharide is produced.
5. Higher levels of Streptococcus mutans.
6. Lower levels of Streptococcus sanguis & Actinomyces.
III. Environmental Factor :-
1. Diet
Diet is defined as the types and amounts of food eaten daily by an individual. Difference in caries incidence was noted among populations with dissimilar diets. Some dietary studies are given below.
A. Vipeholm Study:
It was conducted by Gustafsson et al in 1954.It was a five year investigation of 436 adult inmates in a mental institution at the Vipeholm hospital, Sweden. The institutional diet was nutritious, but contained little sugar, with no provisions for between meal snacks. The dental caries rate in the inmates was relatively low. The experimental design divided the inmates into seven groups that is a control group, a sucrose group, a bread group, a chocolate group, a caramel group, an 8 toffee group, a 24 toffee group.”
Conclusions of the study were
1. Increase in carbohydrate increased the level of dental caries.
2. The risk of caries is greater if food was in a form that will be retained on the tooth surfaces.
3. The risk of caries was greater if sugar is consumed between meals.
4. The increase in caries activity varies between individuals.
5. Increased caries activity rapidly disappears upon withdrawal of sugar rich foods.
6. A high concentration of sugar in solution and its prolonged retention on tooth surfaces leads to increased caries activity. correlates
7. The clearance time of the sugar closely with caries activity. Physical form & frequency of intake is important in cariogenicity than total amount ingested.
B. Hopewood House Study :-
This study was conducted by Sullivan in 1958.The dental status of children between 3 and 14 years of age residing at Hopewood House, New South Wales was studied longitudinally for 10 years. The absence of meat and a rigid restriction of refined carbohydrate were the two principal features of the Hopewood House diet. It was found that 53% of the children at the Hopewood House were caries free whereas only 0.4% of the 13 years old, state school children were free from caries. The children oral hygiene was poor and gingivitis was prevalent in 75% of them. This work shows that, in institutionalized children, at least, dental caries can be reduced by diet, without the beneficial effects of fluoride and in the presence of unfavourable oral hygiene,
C. Turku Sugar Study :-
This study was conducted by Scheinin, Makinen et al in 1975.In a 2 year feeding study, 125 young adults, divided into three groups, consumed the entire dietary intake using these sugars exclusively: sucrose group 35 people, fructose group 38 people and xylitol group 52 people. A dramatic reduction in the incidence of dental caries was found after 2 years of xylitol consumption. Fructose was as cariogenic as sucrose for the first 12 months but became less so at the end of 24 months. It was also found that frequent between meal chewing of a xylitol gum produced an anticariogenic effect.
D. Seventh-Day Adventist Children Study:
The Seven Day Adventist had certain restrictions in their diet which included the limitation of
1. Sugar sticky elements
2. Highly refined starches
3. Between meal snacking
All the studies showed that the level of dental caries was much lower in the Seven Day Adventist group compared to the other children.
E. Hereditary Fructose Intolerence:-
Persons affected with this rare metabolic disorder had learned to avoid any food that contains fructose or sucrose, because the ingestion of these foods causes symptoms of nausea, vomiting, tremor etc. It was noted that the level of dental caries was lower in this group compared to others.
Vitamins like A, D, K. B Complex (B), and calcium & phosphorous, fluoride, amino acid like lysine & fats has an inhibitory effect on dental caries.
2. Geographic variations :-
DMFT is found to be decreasing in developed countries, and increasing in developing countries. The use of fluorides, oral hygiene practice and diet play a major role as a cause for this difference.
3. Soil :-
Selenium is said to increase dental caries whereas molybdenum & vanadium are said to decrease dental caries.
A. Urbanization :-
Dental caries is said to increase with urbanization.
5. Climate :-
Sunlight is said to decrease caries whereas rainfall is said to increase dental caries.