Historical theories of etiopathogenesis
Before modern concepts were established, researchers proposed various theories regarding the origin of caries. Each of them contributed to the understanding of the disease, although each had its weaknesses.
- Chemicoparasitic theory (W. Miller, 1883)
Considered the basis for modern views. The process is divided into two phases: chemical (lactic acid from carbohydrate fermentation dissolves the inorganic tooth substance) and bacterial (enzymes break down dentin organics). Main drawback: normal saliva pH ranges between 6.8–7.0 and, without additional local factors, cannot drop low enough to dissolve enamel.
- Physicochemical theory (D.A. Entin)
The tooth is viewed as a semipermeable membrane through which osmotic currents flow due to pressure differences between blood and saliva. Normally, currents flow from the inside out (centrifugally), nourishing the tooth. In pathology, they reverse to centripetal, drawing harmful agents inward.
- Biological theory (I.G. Lukomsky)
The root cause is damage to odontoblasts, which impairs metabolism. Culprits: vitamin D and B₁ deficiency, fluoride, phosphorus, and calcium imbalance, as well as ultraviolet deficiency.
- A.E. Sharpenak's theory
Emphasis on the depletion of proteins in enamel. Due to a deficiency of amino acids (arginine and lysine), proteins break down rapidly and synthesize slowly. Provoking factors include pregnancy, pneumonia, tuberculosis, hyperthyroidism, nervous agitation, and high ambient temperature.
Role of biofilm and the modern hypothesis
Today, the modern multifactorial hypothesis is recognized as the most reliable. According to this view, the onset of caries requires the simultaneous coincidence of four factors. The main one is the presence of cariogenic microflora in dental plaque, specifically Streptococcus mutans.
A key role in pathogenesis is assigned to microbial dental plaque. The process unfolds as follows:
- Even with good hygiene, an acquired pellicle forms on the tooth (a film composed of salivary glycoproteins and mucopolysaccharides). It attaches via an electrostatic mechanism.
- Bacteria attach to the pellicle. If the plaque is not brushed away, colonies of microorganisms grow.
- Bacteria begin to ferment dietary sugars (glycolysis). Carbohydrates here act as a substrate for acid production.
- Fermentation products (organic acids) lower the local pH level in the plaque to a critical level (4.5–5.0).
- It is precisely at this acidity level that enamel demineralization and lesion formation begin.
Risk factors and localization
The rate and probability of tooth destruction are influenced by additional factors:
- Cariogenic diet: an abundance of sugars and carbohydrates provides bacteria with nutrition for growth and adhesion.
- Decreased tooth resistance: arises from systemic changes in the body or environmental influences.
- Dentoalveolar system characteristics: dental crowding, tooth shape, as well as the properties of oral fluid (remineralizing capacity, buffering properties, protective factors).
Plaque most commonly accumulates where physiological self-cleansing (by the tongue, saliva, and cheeks) is difficult and where a toothbrush has trouble reaching. Typical zones: fissures on masticatory surfaces, contact points between adjacent teeth, and cervical areas.
Stages of caries and initial lesion
In clinical practice, the most convenient classification is clinical-topographic, dividing the process into 4 stages:
- Caries in the spot stage (macula cariosa)
- Superficial caries (caries superficialis)
- Moderate caries (caries media)
- Deep caries (caries profunda)
Features of caries in the spot stage: Clinically, this is a localized area (3–5 mm) of enamel color change ranging from white to brown or black. Enamel integrity is not yet breached: upon probing, the instrument slides over it. Symptoms and pain from sweet/cold stimuli are absent. At the microscopic level, the orientation of hydroxyapatite crystals in the enamel is disrupted, their shape changes, intercrystalline bonds weaken, and atypical crystals appear.
Differential diagnosis: The spot stage must be distinguished from fluorosis and hypoplasia. In fluorosis, spots are symmetrical and uniform in shape, whereas in hypoplasia they are extensive and appear as rings. The most accurate testing method is staining with an indicator solution. A carious spot will take up the stain, while non-carious lesions (fluorosis, hypoplasia) will not.
Briefly: answers to topical questions
What four obligatory factors cause the onset of caries according to the modern multifactorial hypothesis?
The onset of caries requires the simultaneous coincidence of four main factors, though only one is named in the sources.
- Presence of cariogenic microflora (Streptococcus mutans, etc.) — localized in dental plaque.
The listing of the remaining three factors is cut short. Meanwhile, factors contributing to the development of caries include:
- Cariogenic diet — high carbohydrate content acting as a substrate for acids.
- Decreased tooth resistance — arises from shifts in the body's condition.
- Predisposing features of the dentoalveolar system — tooth anatomy and oral fluid properties.
What types of bacteria, besides Streptococcus mutans, play a leading role in caries progression and dentin destruction?
In addition to Streptococcus mutans, other types of microorganisms participate in the progression of the carious process and the destruction of tooth tissues. The leading causative agents also include:
- Lactobacilli (Lactobacillus) — play an important role in the development of the disease.
- Streptococci (Streptococcus sanguis, Streptococcus oralis, Streptococcus gordoni, Streptococcus mitis) — participate in the destruction of hard tissues.
- Veillonellae (Veillonella) — are among the primary causative agents.
- Actinomycetes (Actinomyces) — are present in the microbial landscape.
Additionally, bacteria of the genus Bacteroides (Bacteroides melaninogenicus, Bacteroides intermedius, Bacteroides denticola, Bacteroides loescheii) produce pigments, large accumulations of which indicate the destruction of the dentinoenamel junction and dentin.
What instrumental methods are used to detect hidden carious lesions on the contact surfaces of teeth?
To detect hidden carious lesions on the contact (approximal) surfaces of teeth, primary and supplementary instrumental methods are used.
- Probing — performed using a sharp dental explorer that catches in the hidden cavity.
- Transillumination — transilluminating tooth tissues with light (caries appears as a dark hemisphere).
- Luminescent diagnostics — detecting lesions under ultraviolet radiation.
- Luminescent-histological diagnostics — using surgical microscopes with a quartz emitter.
- Radiography — the leading method for primary diagnosis of dental diseases.
A dental mirror is also used to examine hard-to-reach areas and direct light.
To remember the authors of historical theories of caries, use the acronym MELSH: Miller (chemical theory), Entin (osmosis theory), Lukomsky (odontoblast theory), Sharpenak (proteolytic theory).
Class and exam questions
Why is Miller's theory considered incomplete?
Miller hypothesized that tooth inorganics are dissolved by lactic acid, but the pH of normal saliva (6.8–7.0) never drops on its own to the level at which enamel destruction occurs. The formation of local dental plaque is required.
Does pain occur in caries at the spot stage?
No. At the macula (spot) stage, there is no response to temperature and chemical stimuli whatsoever, and the integrity of the enamel is preserved.
How to reliably differentiate a carious spot from fluorosis?
The main differential criterion is staining. When an indicator solution is applied, a carious spot remains stained after rinsing, whereas a fluorosis spot does not take up the stain.
What else to study on this topic
- The remaining three factors of the modern multifactorial theory of caries
- Specific and non-specific protective factors of oral fluid
- Clinical presentation of superficial, moderate, and deep caries
- Structure and chemical composition of enamel hydroxyapatite crystals
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