Definition of dental caries
Dental caries is a pathological process in the hard tissues of the tooth that occurs after its eruption and is accompanied by demineralization and proteolysis, followed by the formation of a cavity defect. Development occurs under the influence of general and local cariogenic factors. The specification that it occurs after eruption is fundamental: a number of hard tissue pathologies (e.g., hypoplasia) form during the period of tooth development, prior to eruption, and are not classified as caries.
Miller's chemicoparasitic theory
The modern concept is based on Miller's chemicoparasitic theory, which distinguishes two stages of the carious process:
- The first stage — carbohydrate food debris serves as a substrate for microorganisms; the fermentation process releases acids, primarily lactic acid, which destroy the inorganic components of enamel and dentin.
- Second stage — proteolytic enzymes of microorganisms destroy the organic matter of dentin.
The merit of the theory is the recognition of the role of microorganisms, carbohydrates, and the composition of saliva. A significant drawback is the idea that the pH of all saliva changes, whereas in reality, the key importance lies in the local pH reduction beneath the dental plaque. Normally, the pH of saliva is 6.8–7.2.
Cariogenic situation and general factors
Cariogenic situation — a state of decreased resistance of tooth tissues to cariogenic influences due to a disruption of the body's nonspecific resistance against the background of somatic diseases. This is the first link in pathogenesis.
General cariogenic factors include:
- unbalanced diet, abundance of carbohydrates, lack of fluoride in drinking water;
- chronic somatic diseases;
- extreme influences — stress, radiation, extensive trauma, surgical interventions;
- heredity, which determines the inferiority of the structure and biochemical composition of the hard tissues of the tooth;
- changes in the composition, quantity, and quality of saliva.
Local cariogenic factors
- Dental plaque containing microorganisms;
- dental calculus — mineralized dental deposits;
- poorly designed prosthetic and orthodontic structures, defective fillings;
- dentofacial anomalies (tooth crowding) that impede hygiene and promote the retention of food debris;
- the condition of the dental pulp.
Pathogenesis: from the pellicle to the carious cavity
Against the background of a cariogenic situation, microorganisms attach to the pellicle — an acquired organic sheath composed of salivary glycoproteins that covers the enamel. The pellicle performs a protective function, but in the absence of hygiene, it becomes the basis for bacterial colonization.
Next, soft dental plaque forms — an amorphous substance consisting of microorganisms, their metabolic products, desquamated epithelial cells, leukocytes, and food debris. The plaque has a porous structure: on the one hand, carbohydrates enter it, and on the other hand, saliva partially neutralizes and washes out the acids.
If cariogenic conditions persist, metabolic products of microorganisms accumulate, and plaque turns into dental plaque — a structure devoid of porosity and impermeable to oral fluid. Organic acids, primarily lactic acid, accumulate beneath the plaque, leading to a local decrease in pH to critical values of 4–5.
The acidic environment causes the dissolution of hydroxyapatite crystals: the processes of demineralization begin to prevail over the processes of remineralization, which are normally balanced. Caries in the spot stage is formed, and then — a defect in the form of a carious cavity.
Black's classification
The classification reflects the localization of the carious process:
- Class I — occlusal (masticatory) surfaces of molars and premolars, as well as blind pits of the maxillary lateral incisors and the vestibular surface of the mandibular first molars;
- Class II — contact surfaces of molars and premolars;
- Class III — contact surfaces of incisors and canines without involvement of the incisal edge and crown angle;
- Class IV — contact surfaces of anterior teeth involving the incisal edge and crown angle;
- Class V — cervical cavities of all tooth groups on the vestibular and oral sides;
- Class VI (added later) — atypical cavities in the area of the incisal edges of incisors and the tips of the cusps of canines, premolars, and molars.
ICD-10 classification
In practice, ICD-10 is used, where dental caries is coded as K02:
- K02.0 — enamel caries (including white spot lesion / caries in the spot stage and superficial caries);
- K02.1 — dentin caries;
- K02.2 — cementum caries.
The existence of cementum caries emphasizes that the hard tissues of the tooth are represented not only by enamel and dentin.
Key points
- Caries is a pathological process of the hard tissues of the tooth that occurs after its eruption and is accompanied by demineralization and proteolysis.
- The modern concept of caries is polyetiological and relies on Miller's chemicoparasitic theory.
- Cariogenic factors are divided into general (diet, somatic diseases, stress, heredity) and local (plaque, calculus, malocclusion, poor dental restorations).
- The key mechanism is a local pH drop to 4–5 under dental plaque, rather than a change in the pH of the entire saliva.
- Demineralization prevails over remineralization, which leads to the destruction of hydroxyapatite and the formation of a carious cavity.
- Black's classification includes 6 classes and describes the localization of carious cavities.
- ICD-10 distinguishes enamel caries (K02.0), dentin caries (K02.1), and cementum caries (K02.2).