Instruments for tooth extraction

Routes of pulp and periodontal infection

A healthy tooth pulp is reliably protected by enamel and dentin and is completely sterile. Infection of periapical tissues occurs through three main pathways:

1. Direct pathway. Occurs when hard tissues are destroyed as a result of caries, trauma (cracks, fractures), or dental interventions. The presence of exposed pulp is the most common factor initiating an endodontic infection.
2. Infection with an intact crown. Bacteria penetrate through microcracks into a tooth with an already necrotic pulp. Confined in a closed space without access to the periodontium, they exhibit low invasiveness, but upon reaching the root canal, they obtain conditions for active proliferation.
3. Periodontal pathway. Microorganisms from gingival pockets enter the root canals via blood vessels of the periodontal ligament during periodontal inflammation. Anachoresis—hematogenous seeding of a necrotic pulp—is also possible.

Specific periodontal microflora

In chronic periodontitis, dental plaque forms on the root cementum, consisting of filamentous gram-positive bacteria, motile gram-negative microorganisms, and spirochetes. Its calcification leads to calculus formation.

Highly virulent specific microorganisms include:

• Aggregatibacter actinomycetemcomitans
• Porphyromonas gingivalis
• Spirochetes: Treponema denticola, Treponema lecithinolyticum
• Gram-negative anaerobes: Tannerella forsythia, Prevotella intermedia, Fusobacterium nucleatum

The severity of periodontitis directly depends on the quantity of these pathogens. Additionally, Epstein-Barr virus and cytomegalovirus play a certain role in the etiology of periodontal diseases.

Mechanisms of periapical tissue destruction

Apical periodontitis never resolves spontaneously because microbes are securely sheltered within the root canal—out of reach of the immune system. Bacterial survival depends on their synergism, immune evasion, and the release of lipopolysaccharides (LPS) and enzymes.

The pathogenesis of bone destruction is immune-mediated:

1. Bacterial toxins (LPS, proteases) interact with immune cells.
2. Osteoclasts are activated.
3. Bone resorption mediators are released.
4. Surrounding tissues are destroyed.

At the initial stage of acute inflammation, neutrophils phagocytose pathogens and release mediators that attract macrophages. The death of a vast number of neutrophils leads to the release of enzymes that damage the extracellular matrix. This destruction has a protective function—it prevents the generalization of the infection.

Molecular inflammatory mediators

The development and maintenance of the inflammatory focus are regulated by a complex network of cytokines and eicosanoids.

Cytokines:

• IL-1 and TNF-α: Amplify the vascular response, stimulate osteoclasts, and inhibit bone formation. They exert systemic effects (elevation of acute-phase proteins).
• IL-6: Counteracts the effects of IL-1, but together with it activates hematopoiesis to mobilize neutrophils.
• IL-8: A potent chemoattractant for neutrophils in the acute phase.

Eicosanoids: Synthesized from arachidonic acid of cell membranes.

• Prostaglandins (PGE2, PGI2): Formed with the participation of cyclooxygenase (COX). PGE2 is synthesized predominantly by polymorphonuclear leukocytes and is a potent osteoclast activator. Administration of indomethacin (a COX inhibitor) can prevent initial bone resorption.
• Leukotrienes (LTB4): Formed with the participation of lipoxygenase, causing leukocyte adhesion to the endothelium.

Chronization of the process and periapical granuloma

With prolonged influx of bacteria from the canal, the focus transforms. The neutrophil infiltrate is replaced by a lesion surrounded by a collagen capsule, with a predominance of macrophages and T-lymphocytes. A periapical granuloma is formed—an asymptomatic lesion that keeps the antigen localized.

In 45% of cases, the granuloma undergoes epithelization: the epithelium can grow into the canal orifice, forming a plug. The dense fibrous capsule is firmly fused to the root, so during tooth extraction, the lesion is removed in its entirety.

Tissue healing and regeneration

A prerequisite for successful regeneration is complete debridement and obturation of the root canal. Tissue remodeling lasts from several months to years and proceeds from the periphery to the center:

1. Formation of a fibrin blood clot.
2. Replacement with richly vascularized granulation tissue.
3. Synthesis of bone matrix by osteoblasts.
4. Formation of secondary cementum.
5. Restoration of periodontal fibers.

When the cortical plate is damaged, the periosteum participates in repair; when the bone is intact, the endosteum participates.

What else to study on this topic

• Mechanisms of matrix destruction: osteoclastic, phagocytic, and the role of matrix metalloproteinases (MMPs).
• Colony-stimulating factors (CSFs) and their effect on cell proliferation in the bone marrow.
• The role of immunoglobulins (especially IgG) and plasma cells in apical periodontitis.
• Functions of transforming growth factor-beta (TGF-β) in angiogenesis and periodontal healing.

Other topics in "Chapter 14. Tooth Extraction"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.