Etiology and Classification
The development of inflammation can be triggered by infection (predominantly bacterial) or physical and chemical factors. In the latter case, it is referred to as sterile pulpitis: traumatic, radiation, decompression, thermal (e.g., during aggressive tooth preparation), or toxic.
Depending on the localization, coronal, radicular, and total involvement are distinguished. From a clinical perspective, the most critical criterion is the response to therapy: the pathology can be reversible or irreversible. The transition to an irreversible course is usually driven by bacterial invasion of the tissue.
Acute Forms of Pulpitis
- Serous: Begins as a focal process (often near the floor of the caries cavity), then may become diffuse. It is often a sterile and reversible condition lasting only a few hours and culminating in restitutio ad integrum (complete recovery). Without treatment, it progresses to purulent or chronic pulpitis.
- Purulent focal (pulp abscess): Develops with direct tissue infection.
- Purulent diffuse (pulp phlegmon): Involves both the coronal and radicular pulp. Macroscopically, the tissue acquires a grayish tint with multiple small yellow foci. A paradoxical decrease in pain intensity in the late stages is characteristic, explained by the destruction of nerve endings by purulent exudate.
Chronic Forms of Pulpitis
Chronic inflammation can develop primarily (against the background of dental caries) or as an outcome of acute inflammation. It invariably leads to atrophy and loss of function.
- Granulating: Tissue is replaced by granulation tissue, odontoblasts die, and dentin undergoes lacunar resorption with the formation of osteodentin. A special variant is a pulp polyp (chronic hypertrophic pulpitis)—a mushroom-like protrusion of granulation tissue from the carious cavity, typical of children and young adults.
- Fibrous: Forms during the maturation of granulation tissue. The pulp chamber is filled with whitish, dense scar tissue. The process is accompanied by sclerosis, stromal hyalinosis, formation of calcifications, pseudocysts, and colliquative necrosis of odontoblasts.
- Gangrenous (gangrene of the pulp): A conditionally chronic, rare form. It represents tissue necrosis within an exposed pulp chamber, accompanied by the formation of gray-black detritus, which subsequently undergoes compaction.
Reactive Changes of the Pulp
Any non-inflammatory processes in the neurovascular bundle of the tooth are termed reactive changes. They are divided into three main categories:
- Alterative (injuries): hydropic and fatty degeneration of odontoblasts, mucoid and fibrinoid swelling of blood vessels (often in rheumatic diseases), local or systemic hyalinosis. The extreme degree is tissue death: necrosis (with a closed pulp chamber) or gangrene (with an open chamber).
- Circulatory disturbances: local or generalized disorders of blood and lymph circulation.
- Adaptive: reticular atrophy, formation of pseudocysts, production of secondary (reparative) dentin. A crucial role is played by calcifications—deposition of petrificates (necro-, fibro-, and thrombocalcinosis) and the formation of denticles. The latter are dentin inclusions that can be intrapulpal (free), parietal (attached), or interstitial (embedded within the dentin layer).