Inflammatory cytokines in normal and irreversibly inflamed pulps: A systematic review

Objective: To review the available literature in regard to the inflammatory process and pulpitis. Setting forth to evaluate if differences in the levels of various cytokines (TNF-alpha, IL-1 beta, IL-2, IL-6 and IL-8) can be observed in clinically diagnosed normal and irreversibly inflamed pulps that could serve as possible markers and/or diagnostic tools to predict and differentiate between certain states of inflammation. Methods used to measure and assess levels of cytokines have been limited to two protein quantification methods ELISA and/or Multiplex Array. Design: The databases PubMed, EMBASE/Ovid, The Cochrane Central Register of Controlled Trials, Cochrane Reviews and Scopus were consulted for the electronic literature search. Screening of titles and abstracts followed the PRISMA guidelines while data extraction and the assessment of the full texts were carried out in accordance to the GRADES assessment. Results: The review showed that significant increases in levels of IL-1 beta, IL-2, IL-6, IL-8 and TNF-alpha in irreversible pulpitis samples exist, in comparison to normal pulp samples which serve as a good basis for potential markers. Due to larger discrepancies in available literature, IL-2 seems rather unsuitable at the moment, while IL-6 and TNF alpha seem to be more promising. Conclusion: It may be concluded that even by combining two protein quantification methods inconsistencies between studies exist. At the moment it is difficult to select just one specific cytokine suitable for testing, rather it supports the rationale that further high-quality clinical studies are needed.