Purpose: This study was conducted to evaluate the effects of the probiotic Lactobacillus paracasei in patients undergoing removal of impacted mandibular third molars, focusing on tumor necrosis factor alpha (TNF-α) levels in gingival crevicular fluid, pain, swelling, trismus, and interincisal distance.

Methods: Thirty patients were divided into two groups: (1) wound irrigation with the probiotic, and (2) irrigation with 0.9% normal saline. The data were collected at the baseline, and at 24 h and 7 days after the operation. The TNF-α level in gingival crevicular fluid was determined using the ELISA technique.

Results: In the experimental group, the probiotic L. paracasei MSMC39 reduced the TNF-α level in gingival crevicular fluid to a significantly greater degree than in the control group (P < 0.05). Pain, swelling and trismus evaluated in terms of a visual analog scale (VAS) score were lower in the experimental group than in the control group, but not to a statistically significant degree (P > 0.05). The mean interincisal distance in the experimental group was higher than that in the control group (P = 0.014).

Conclusion: The probiotic L. paracasei is able to reduce the level of TNF-α in gingival crevicular fluid and can ameliorate postoperative complications after mandibular molar removal.