Caries

Definition

Dental caries is defined as a microbiological disease of the hard structure of teeth, which results in localized demineralization of the inorganic portion and destruction of the organic substances of the tooth.

Cariology is a science which deals with the study of etiology, histopathology, epidemiology, diagnosis, prevention and treatment of dental caries.

Destruction of a tooth by dental caries and disease

Factors Affecting Incidence of Caries

Dental caries is an ecological disease in which the diet, the host and the microbial flora interact in a way which increases demineralization of the tooth structure with resultant caries formation.

Some races have higher incidence of dental caries, e.g. white American and English people. Some races (e.g. Indians and black Americans) due to hereditary patterns have lower incidence of dental caries. There are some local factors which can easily alter the manifestation of caries activity based on heredity pattern.

The difference in occurrence of dental caries in different individuals of same age, sex, race and geographic area, diet, and similar living conditions is because of various factors that manipulate the etiology of caries.

Host

• Lack of enamel maturation or the presence of developmental defects in enamel may result in increase the caries risk. These defects increase plaque retention, increase bacterial colonization, and in some cases, the loss of enamel make it more susceptible to tooth demineralization.
• The physical characteristics of teeth like deep and narrow occlusal fissures, deep buccal or lingual pits and enamel hypoplasia, etc. affect the initiation of dental caries.
• Fluoride content is lesser in carious enamel and dentin as compared to a sound tooth. In carious enamel and dentin it is 139 ppm - 223 ppm, whereas in sound enamel and dentin it is 410 ppm - 873 ppm, respectively.
• If a tooth is out of position, rotated or in any abnormal position, it becomes difficult to clean, and hence retains more food and debris.

Environment of the Tooth

Saliva

• Saliva contains salivary proteins which get deposited onto the tooth surface which help the enamel against acid dissolution. This protective layer is referred to as the pellicle.
• Since saliva is rich in calcium, phosphate and fluoride, these materials help in remineralization of the enamel.
• Saliva acts as cleaner of teeth as it quickly washes away food debris from the mouth and to buffer the organic acids that are produced by the bacteria.
• Any salivary dysfunction, effect of medication or radiotherapy can result in decreased quantity and quality of saliva which further promotes caries.
• When salivary flow is reduced or absent, there occurs the increased food retention. Since salivary buffering capacity is lost, an acid environment is encouraged which further promotes the growth of aciduric bacteria. These aciduric bacteria savor the acid conditions and metabolize carbohydrates in the low-pH environment. This results in initiation of the caries.

Diet

• Physical nature of diet: In the earlier times, the primitive man used to eat rough and raw unrefined foods which had self-cleansing capacity. But in present times, soft refined foods are eaten which stick stubbornly to the teeth and are not removed easily due to lack of roughage. This is the reason for higher incidence of dental caries nowadays than the past.
• Nature of carbohydrate content of the diet: To cause demineralization of dental enamel, it is essential for fermentable carbohydrates and plaque to be present on the tooth surface for a minimum length of time. These need to be retained in the mouth long enough to be metabolized by oral bacteria to produce acid.
• It is seen that acids produced by fermentable carbohydrates cause a rapid drop in plaque pH to a level which results in demineralization of the tooth structure. But since acids produced in plaque diffuse out of the plaque combined with buffering capacity of saliva exerting a neutralizing effect, this acidic nature of plaque remains for sometime only, and with in 30-60 minutes, plaque returns to its normal pH. However, repeated and frequent consumption of sugar will keep plaque pH depressed which results in demineralization of the teeth. Stephan has shown the relationship between change in plaque pH over a period of time following a glucose rinse in form of a graph. This graph is called a “Stephan curve” (Stephan and Miller, 1943). The drop in pH is the result of fermentation of carbohydrates by plaque bacteria. The gradual return of the pH occurs because of buffers present in plaque and saliva. This drop in pH can demineralize tooth structure depending on the absolute pH decrease, as well as the length of time that the pH is below the “critical pH” level. The critical pH value for demineralization usually ranges between 5.2 to 5.5. Caries occurs when the process of remineralization is slower than the process of demineralization and there is a net loss of mineral into the environment. It can be prevented by restricting the intake of dietary sugars, and removing plaque.

"Stephan curve", showing sudden decrease in plaque pH following glucose rinse, which returns to normal after 30–60 min. Net demineralization of dental hard tissues occurs below the critical pH (5.5), shown in yellow.

Tooth remineralization can take place if the pH of the environment adjacent to the tooth is high due to:

1. Lesser number of cariogenic bacteria
2. Availability of fluoride
3. Lack of substrate for bacterial metabolism
4. Elevated secretion rate of saliva
5. Strong buffering capacity of saliva
6. Presence of inorganic ions in saliva
7. Quick washing of retained food.

• Frequency of carbohydrate intake: In a person with normal salivary function, after intake of fermentable carbohydrate foods or drinks, the acidic pH lasts 30-60 minutes. Greater time between acid attacks allows greater time for the repair process (remineralization) to occur.
• Vitamin content of the diet: As we know vitamin are essential components of daily diet. Deficiency of some vitamins increases the incidence of dental caries.

1. Vitamin A: Deficiency or excess are not related to dental caries.
2. Vitamin D: Vitamin D helps in normal development of teeth. Enamel hypoplasia can result due to vitamin D deficiency. It can result in early

attack of caries. It has been seen that supplement of vitamin D in children helps in the formation of healthy teeth and thus helps in reduction in the dental caries.

1. Vitamin K: Deficiency does not affect the dental caries incidence.
2. Vitamin B complex : Its deficiency may exert a caries protective influence on the tooth. Several types of vitamin B are important growth factors for

the oral acidogenic flora which serve as component of the co-enzymes involved in glycolysis. Vitamin B6 acts as an anticaries agent because it promotes the growth of noncariogenic organisms.

1. Vitamin C: Directly vitamin C does not help in protection of tooth against dental caries, but it is required for the normal health of the gingiva.

Bacteria

• Dental caries do not occur if the oral cavity is free of bacteria.
• Most commonly seen bacteria associated with caries are Streptococcus mutans, Lactobacillus spp., Veillonella spp. and Actinomyces spp.
• Streptococci mutans are considered main causative factors for caries because of their ability to adhere to tooth surfaces, produce abundant amounts of acid, and survive and continue metabolism at low pH conditions. Colonization with Streptococcus mutans at an early age is an important factor for early caries initiation.

Time Period

The time period during which all above three direct factors, i.e. tooth, microorganisms and substrate are acting jointly should be adequate to produce acidic pH which is critical for dissolution of enamel to produce a carious lesion. Time required for acid production from the fermentation of the carbohydrates by bacteria and for demineralization of tooth, is allowed by poor oral hygiene and not cleaning teeth immediately after eating.

Classification of Dental Caries

According to their Anatomical Site

• Pit and fissure caries: Pit and fissure caries occur on occlusal surface of posterior teeth and buccal and lingual surfaces of molars and on lingual surface of maxillary incisors.
• Smooth surface caries: Smooth surface caries occurs on gingival third of buccal and lingual surfaces and on proximal surfaces.
• Root caries: When the lesion starts at the exposed root cementum and dentin, it is termed as root caries.

According to Whether it is a New Lesion or Recurrent Carious Lesion

• Primary caries: denotes lesions on unrestored surfaces.
• Recurrent caries: Lesions developing adjacent to fillings are referred to as either recurrent or secondary caries.
• Residual caries is demineralized tissue left in place before a filling is placed.

According to the Activity of Carious Lesion

• Active carious lesion: A progressive lesion is described as an active carious lesion.
• Inactive/arrested carious lesion: A lesion that may have formed earlier and then stopped is referred to as an arrested or inactive carious lesion. Arrested carious lesion is characterized by a large open cavity which no longer retains food and becomes self-cleansing.

According to Speed of Caries Progression

• Acute dental caries: Acute caries travels towards the pulp at a very fast speed.
• Rampant caries: It is the name given to multiple active carious lesions occurring in the same patient, frequently involving surfaces of teeth that are usually caries free. It occurs usually due to poor oral hygiene and taking frequent cariogenic snacks and sweet drinks between meals. It is also seen in mouths where there is hyposalivation.
• Chronic dental caries: Chronic caries travel very slowly towards the pulp. They appear dark in color and hard in consistency.

Rampant caries caused by methamphetamine abuse

Based on Treatment and Restoration Design

It is given by GV-Black:

• Class I: Pit and fissure caries occur in the occlusal surfaces of premolars and molars, the occlusal twothird of buccal and lingual surface of molars, lingual surface of incisors.
• Class II: Caries in the proximal surface of premolars and molars.
• Class III: Caries in the proximal surface of anterior (incisors and canine) teeth and not involving the incisal angles.
• Class IV: Caries in the proximal surface of anterior teeth also involving the incisal angle.
• Class V: Caries on gingival third of facial and lingual or palatal surfaces of all teeth.
• Class VI: Caries on incisal edges of anterior and cusp tips of posterior teeth without involving any other surface.

GV-Black's Classification

Based on Pathway of Caries Spread

• Forward Caries: When the caries cone in enamel is larger or of same size as present in dentin, it is called as forward caries.
• Backward Caries: When spread of caries along dentinoenamel junction exceeds the adjacent caries in enamel, it is called backward caries (here caries extend from DEJ to enamel).

Based on Number of Tooth Surfaces Involved

• Simple caries: Caries involving only one tooth surface is termed as simple caries.
• Compound caries: If two surfaces are involved it is termed as compound caries.
• Complex caries: If more than two surfaces are involved it is called as complex caries.

Classification According to the Severity

• Incipient caries: Involves less than half the thickness of enamel.
• Moderate caries: Involves more than half the thickness of enamel, but does not involve dentinoenamel junction.
• Advanced caries: Involves the dentinoenamel junction and less than half distance to pulp cavity.
• Severe caries: Involves more than half distance to pulp cavity.

Graham Mount’s Classification

This classification system is based on two simple parameters:

1. Location of carious lesion
2. Size of carious lesion

Graham Mount’s Classification

Cavity site	Size 1 (Minimal)	Size 2 (Moderate)	Size 3 (Enlarged)	Size 4 (Extensive)
Site 1 (Pit and fissure)	1.1	1.2	1.3	1.4
Site 2 (Contact area)	2.1	2.2	2.3	2.4
Site 3 (Cervical region)	3.1	3.2	3.3	3.4

Prevention of Dental Caries

Methods to Reduce Demineralizing Factors

Diet has been considered one of the main step in influencing the dental caries. Different nutritional substitutes are:

• Sugar substitutes:

1. Xylitol
2. Sorbitol

• Fibrous food: It has been seen that intake of raw vegetables, fruits and grains increases caries protective mechanism as they contain natural phosphates, phytates and non-digestable fibers, moreover they do not stick to teeth.
• Low caloric sweeteners: In this, several sweetener such as aspartame, saccharin and cyclamate considered to have some role.
• Fats: Fats used to form a protective barrier on enamel or on carbohydrate surface so that it is less available for bacteria.
• Cheese is considered responsible for:

1. Increasing the salivary flow
2. Increasing the pH
3. Promoting the clearance of sugar.

All these factors help in reducing the incidence of caries.

• Trace elements:

Trace elements

Effect	Mineral
Cariostatic	Fluoride (F), phosphate (PO4)
Mild cariostatic	Fe, Li, Cu, B, Mo, V, Sr, Au
Doubtful	Co, Zn, Br, I
Caries inert	Al, Ni, Ba, Pd
Caries promoting	Mg, Cd, Pb, Si

Methods to Improve Oral Hygiene

• Dental prophylaxis: In dental prophylaxis, polishing of roughened tooth surfaces and replacement of faulty restorations is done so as to decrease the formation of dental plaque, therefore, resulting in less incidence of caries.
• Toothbrushing: Toothbrushing is considered to be the most reliable means of controlling plaque and provide clean tooth surface. Many toothbrushing techniques have been described and being promoted as being effective. Bass technique is most recommended as it emphasizes sulcular placement of bristles

while in periodontal cases, sulcular technique with vibratory motion is preferred.

• Interdental cleaning aids:

1. Dental floss and tape : Used in persons with normal proximal contact between their teeth.
2. Woodsticks and interdental brushes: They are indicated in patients with wide interdental spaces because of gingival recession and/or loss of periodontal attachment.

Chemical Measures

• Substances interfering with carbohydrate degradation through enzymatic alterations

1. Vitamin K: Vitamin K, synthetically made, has been found to prevent acid formation, when added in incubated mixtures of glucose and saliva.
2. Sarcocide: It has also been found to have some role in caries prevention.

• Substances interfering with bacterial growth and metabolism

1. Chlorhexidine: Chlorhexidine has highly positive charge, which is responsible for reducing the number of Streptococcus mutans.
2. Urea and ammonium compounds: Urea is usually degraded by urea which releases ammonia, neutralizes the acids and also interferes with bacterial growth.
3. Glutaraldehyde: It has been shown that a two minutes daily application of glutaraldehyde reduces mineral loss in dentin caries.

Methods to Increase Protective Factors

Methods to Improve Flow, Quantity and Quality of Saliva

In patients with hyposalivation, the mouth rinse prepared by mixing two teaspoons of baking soda in eight ounce of water is used.

Chemicals Altering the Tooth Surface or Structure

• Fluorides: Fluoride, inorganic component, is important part of natural diet for humans. Fluoride ions increase the resistance of the hydroxyapatite

in enamel and dentin to dissolution by plaque acids. The dentin requires higher levels of fluorides for remineralization (100 ppm) than enamel (5 ppm).

Sodium fluoride tablets

Fluoride reacts with enamel and dentin and produce different effects:

1. Formation of fluoroapatite (less soluble than hydroxyapatite)
2. Inhibits demineralization
3. Induces remineralization
4. Inhibition of bacterial metabolism
5. Inhibition of plaque formation

Clinical fluoride products:

1. Professional topical fluorides
2. Fluoride varnishes
3. Mouthrinses
4. Dentifrices
5. Supplements in form of fluoride tablets and drops
6. Fluoridated salt.

Management of Dental Caries

The restoration of a decayed tooth involves the use of a drill, low or high speed for preparation cutting. But nowadays other procedures have also been used for removal of caries like air abrasion, chemomechanical caries removal, atraumatic restorative therapy (ART) and latest with lasers.

Amalgam restoration

Caries Resources
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