Gingival Retraction Procedure is Associated with Increased Gene Expression of TNF-α and TNF-α Receptors: A Pilot Study

Background: Gingival retraction procedure (GRP), a regularly practiced clinical procedure, displaces the gingiva from around the tooth, temporarily. It has been reported that increased tumor necrosis factor-alpha (TNF-α) levels in gingival crevicular fluid (GCF) were observed even after 30 days following GRP. TNF-α is a pro-inflammatory cytokine found in periodontally-diseased tissues and is associated with loss of connective tissue and bone. The effects of (TNF-α) are tightly regulated by TNF receptor-1 (TNFR1) and 2 (TNFR2). The object of these experiments was to test the hypothesis that up-regulation of TNF-α expression is associated with increased gene expression of its receptors, (i.e., TNFR1 and TNFR2).

Methods: In a GRP rat model, the gingival Index (GI) was recorded, the expressions of TNF-α, and associated genes TNFR1, and TNFR2 in gingival tissue were measured and hematoxylin and eosin (H&E) histological examination was performed.

Results: Expression of TNF-α and TNFR2-related genes demonstrated similar profiles. Both paralleled the profile of the GI. They peaked at day 1 after GRP, and were reduced but still remained at a higher level as compared to sham control at day 3 after GRP, and then returned close to normal at day 7. On the other hand, TNFR1 gene expression peaked at day 3 and remained elevated at day 7 after GRP.

Conclusions: The results indicate gene expressions of TNF-α and TNHR2 are closely associated with the time course of the gingival injury from the retraction procedure, while TNFR1 gene expression may have further long-term effects.