A number of hypothetical mechanisms which may be responsible for pain and swelling before and during endodontic therapy are presented.
- Mechanisms include:
- Alteration of the local adaptation syndrome: Tissue adapts to chronic inflammation, but when a new irritant is introduced (medicaments, irrigants) a violent reaction may occur à liquefaction necrosis = pain/swelling.
- Changes in periapical tissue pressure: May cause exudate to place pressure on nerve endings OR if pressure changes in the apical area (<atm pressure), there may be aspiration of canal contaminants into the periapical tissues.
- Microbial factors: Production of enzymes and endotoxins (LPS) and teichoic acids of gram + organisms have been implicated in flare-ups and subsequent inflammation.
- Also B. melaninogenicus implicated as a microbial pain source
- Effects of chemical mediators: Histamine, serotonin, prostaglandins, leukotrienes, and lymphokines are capable of causing pain. Also, Hageman factor effectively activates bradykinin which =pain
- Changes in cyclic nucleotides: Transmitters, such as histamine, norepinephrine, and serotonin, during the inflammatory response, are capable of elevating cyclic AMP levels in tissues. This reduces nerve transmission. Cyclic GMP enhances nerve depolarization and mast cell degranulation which = pain.
- Immunological phenomena: Production of immunoglobulins, complement fixation, and plasma cell infiltration takes place and contribute to the destructive phase of inflammation and subsequent pain.
- Various psychological factors: Fear of dentists, anxiety, apprehension, and other factors may influence the patient’s pain perception and reaction thresholds.
Pain from flare-ups is a multifactorial issue.