It is very strange that the hardest tissue of the body – the enamel, which is indestructible otherwise, can disintegrate in the oral environment. Caries (Latin meaning ‘dry rot’) is the name given to the prcess of slow disintegration that may affect any of the biologic tissues by bacterial action. Usually, such disintegration also affects the tooth, that is why the term ‘Dental Caries’ is common. In a simple manner, Dental Caries can be defined as ‘the irreversible, slow progressing decay of hard tissues of the tooth’.
Dental caries can be classified according to 3 major factors:
a. According to tooth Morphology –
- Pit and Fissure Caries
- Smooth Surface Caries
- Root Caries
- Linear Enamel Caries
b. According to severity and progress of the lesion –
- Incipient Caries
- Rampant Caries
- Arrested Caries
- Recurrent Caries
- Radiation Caries
c. According to Age pattern –
- Nursing bottle Caries
- Adolescent Caries
- Geriatric Caries.
ETIOLOGY OF DENTAL CARIES –
Dental Caries is a multifactorial disease. There are 4 factors contributing to the caries process, which is explained below,
1. Host Factor
a. Tooth Factor
- Morphology and position in the arch
- Chemical nature
- Composition, pH, antibacterial activity
- Quantity and viscosity of salivary flow
2. The Microflora
3. The substrate/diet
- Physical nature
- Chemical nature
1. The Host Factor
- Morphology, and position in the arch –
Deep pits and fissures in any tooth make them susceptible to decay because of food impaction and bacterial stagnation. That is the reason for occlusal surfaces to be an easy target for decay. Irregularities in the arch form, crowding of the teeth also favors development of caries. Partially impacted third molars are more prone to caries and so are the buccally or lingually placed teeth.
Surface enamel is more caries resistant than subsurface enamel. The surface enamel has more minerals and less water content, compared to the deeper layers. In addition certain elements such as Fluoride, chloride, zinc lead etc. accumulates more on the enamel surface than the subsurface. With the passage of time, teeth become more resistant to caries because of decrease in permeability and increase in nitrogen and fluoride content.
- Composition, pH, antibacterial activity –
Caries prone individuals have low calcium and phosphorous levels. Caries immune people have greater ammonia content in saliva, probably because the higher ammonia content in saliva retards plaque formation and neutralizes acid formation to a certain extent.
The pH at which saliva ceases to be saturated with calcium and phosphorous is called critical pH. Under normal conditions, the critical Ph is 5.5. Below this value, the inorganic content of the tooth may dissolve. A fall in the buffering capacity of saliva leads to increase in caries incidence.
Lysozyme, an antibacterial agent in saliva, can inhibit airborne and water borne organisms in the oral cavity to some extent. It is effective against cariogenuc micro organisms maintiaining the etiologic balance of oral flora.
- Quantity and Viscosity of salivary flow –
Human beings suffering from decreased flow of saliva or lack of salivary secretions (Xerostomia) usually experience increased rate of tooth decay. This is evidenced in various diseases such as Sjogren’s syndrome, Sarcoidosis, Diabetes etc.
Under decreased salivary flow, it has been observed that there occurs an alteration in the microflora due to decreased salivary buffering capacity which favors the growth of more aciduric yeasts.
Tooth decay cannot occur without the presence of micro organisms.
3. The substrate or diet
- Physical nature of diet –
The diet of primitive man consisted of raw food including sand, soil coatings, which led to attrition and also cleansing the teeth off the debris, thereby reducing caries. Modern diet includes, refined foods, soft drinks, and eatables which lead to collection of debris predisposing to more caries.
- Chemical nature of diet -
The main ingredient is carbohydrate, which is accepted as one of the most important factor in dental caries process. Basically, following factors are responsible as far as diet and dental caries is concerned,
i. Particle size or roughness of diet
ii. Palatability of diet
iii. Eating and drinking pattern; after diet and within diet
iv. Retention and clearance of diet
v. Age at which diet is offered.
SIGNS AND SYMPTOMS
An individual affected by the dental decay is usually unaware about it. The carious lesion starts, as a small chalky white spot on the enamel surface, which is asymptomatic. This early sign of enamel demineralization is called incipient decay. This eventually progress to a full blown cavity. once the cavitation takes place, the process becomes irreversible. A brown, shiny lesion indicates that dental caries was present there, which has undergone remineralization, which is also called arrested caries A dull appearance on the contrary suggests, an ongoing demineralization process.
Once the decay passes through enamel, the dentinal tubules, which have passages to the nerve of the tooth, become exposed and elicits pain. Fctors like heat, cold, sweet foods or drinks can aggravate the pain.
a. Visual Examination:
- Includes, looking for cavitation, surface roughness, opacification and discoloration.
- Teeth are cleaned and dried with compressed air, and viewed under adequate light source.
b. Tactile Examination:
Tip of the Dental Explorer used for diagnosis of Caries
- Includes, determing roughness or softness of the tooth surface, with a sharp explorer.
- Both, penetration and resistance of an explorer tip (catch) have been interpreted as an evidence of demineralization.
Various aids for diagnosis of caries include –
I. Radiographic methods:
- Conventional Radiography
- Xero Radiography
- Digital Imaging
- Computer Image Analysis
- Subtraction Radiography
II. Electrical Resistance:
- An instrument called ‘Van Guard Electronic Cries Detector’ has been designed to measure the electrical conductivity of the tooth.
- The electrical conductivity is directly proportional to the maount of demineralization that has occured.
- Electrical resistance is measuring the electrical conductivity through the pores.
III. Ultraviolent Illumination:
- Ultraviolent light (UV) has been used to increase the optical contrast between the carious region and the surrounding sound tissue.
IV. Laser Auto Fluorescence (LAF)
- Endoscopic technique is based on observing the fluorescence that occurs when tooth is illuminated with blue light in the wavelength range of 400-500nm.
- Difference is seen in the fluorescence of sound enamel and carious enamel.
VII. Ultrasonic imaging:
- Ultrasonic imaging was introduced for detecting early carious lesions in smooth surfaces. The demineralization of natural enamel is assessed by ultrasound pulse echo technique.
VIII. Dye Penetration Method.
Topical fluoride application helps in remineralization of small incipient lesions. The goal of treatment is to preserve tooth structures and prevent further destruction of the tooth.
Some Prescription medications—may be required in some cases to relieve pain during or following treatment or to relieve anxiety during treatment. In a cavity, large portions of the decayed material from the tooth is removed using the dental handpiece (drill). A spoon excavator is used, manually to scoop out the soft carious material, from the depth of the cavity. After complete removal of the decay, the tooth is ready for restoration. This helps the tooth to regain its function and aesthetic condition.
Restorative materials include dental amalgam, porcelain, composite resins, gold. Composite resin and porcelain can be made to match the color of a patient’s natural teeth and are thus used more frequently when aesthetics are a concern. Composite restorations are not as strong as dental amalgam and gold; some dentists consider the latter as the only advisable restoration for posterior areas where chewing forces are great.
In case of extensive decay, there may not be enough tooth structure to retain a restoration. in such cases, placement of crowns becomes mandatory. This restoration appears similar to a cap and is fitted over the remainder of the natural crown of the tooth. Crowns are often made of gold, porcelain, or porcelain fused to metal.
If the decay has proceeded to involve the dental pulp. the tooth will need to undergo a root canal treatment, which involves removal of the necrotic pulp tissue by thorough debridement, and replaced by Guttapercha points. This leaves the tooth non-vital and devoid of any living tissue. This is then followed by crown placement, to protect the tooth. may be necessary for the restoration of a tooth.
If the tooth is too far destroyed from the decay process to effectively restore the tooth, tooth extraction is advised. Extractions may also be preferred by patients unable or unwilling to undergo the expense or difficulties in restoring the tooth.