Understanding asymptomatic irreversible pulpitis: an update

Abstract

Background: With an extensive innervation of the pulp tissue, asymptomatic irreversible pulpitis (AIP) or "silent pulpitis" represents a puzzling clinical condition. Studies suggest that local endogenous analgesics inhibit the pulpal nociceptors and are responsible for the asymptomatic nature of AIP. Nevertheless, there is no a review that integrates AIP related mechanisms, and the last update is a clinical study of two decades ago. This review aimed to compile updated information on the factors involved in the mechanisms of analgesia underlying AIP. Highlights: Endogenous opioids, G protein-activated inwardly rectifying K+ channels, endogenous cannabinoids, γ-aminobutyric acid, and neuropeptides (somatostatin, cortistatin, galanin, and bombesin) are involved in AIP analgesia. Specialized pro-resolving lipid mediators (lipoxins, resolvins, maresins, and protectins), oxytocin, phoenixin, opiorphin, and adipokines may play a role in this puzzling clinical condition. Conclusion: This review provides updated information on the asymptomatic characteristics of AIP, including the potentially involved mechanisms. Nevertheless, the painless nature of AIP remains to be clarified and warrants further research.