Effect of Diphenhydramine Mouthwash on Pain During Inferior Alveolar Nerve Block Injection

Introduction: Pain management in dental procedures is a central concern, as discomfort during local anesthesia injections often reduces patient compliance and increases procedural anxiety. The inferior alveolar nerve block (IANB) is a commonly employed technique for mandibular anesthesia but is frequently associated with injection pain. Diphenhydramine, an antihistamine with local anesthetic properties, has recently gained attention as a topical analgesic agent. However, evidence on its clinical efficacy in reducing injection pain during IANB is limited. This study aimed to evaluate the effect of diphenhydramine mouthwash on pain perception during inferior alveolar nerve block injection in patients undergoing oral surgical procedures. Materials and Methods: In this randomized clinical trial, 39 patients requiring bilateral IANB at the Faculty of Dentistry, Alborz University of Medical Sciences (2024), were enrolled. Using a split-mouth design, one side of the mandible was randomly assigned to rinsing with 15 mL diphenhydramine mouthwash for 30 seconds, while the contralateral side was rinsed with normal saline. Pain intensity during injection was assessed 5 minutes after rinsing using a 10-point Visual Analogue Scale (VAS). Statistical analysis was performed using paired t-tests, with significance set at p < 0.05. Results: The mean VAS pain score was significantly lower in the diphenhydramine group (3.31±0.86) compared to the control group (4.92±0.84) (p < 0.001). The analgesic effect was consistent across age groups (19–79 years), genders, and different types of surgical procedures (tooth extraction, implant placement). Conclusion: Diphenhydramine mouthwash effectively reduced pain during IANB injection and may serve as a simple, low-cost adjunct to improve patient comfort in oral surgery. Future studies should focus on optimizing dosing protocols and confirming long-term clinical benefits. Keywords: Diphenhydramine mouthwash; Inferior alveolar nerve block; Local anesthesia; Pain management; Clinical trial.