Effect of Low-Level Laser Therapy (LLLT) on Pain at Injection Site of Local Anesthetic Agent

Abstract

Background: Pain and anxiety associated with local anesthetic injection remain persistent challenges in dental practice, often deterring patients from seeking timely treatment. While various pharmacological and non-pharmacological approaches have been employed to mitigate injection-related pain, their effectiveness remains inconsistent. Low-level laser therapy (LLLT), a form of photobiomodulation, has demonstrated analgesic, anti-inflammatory, and tissue-healing properties in multiple clinical contexts, but its efficacy in reducing pain during anesthetic administration is inconclusive. Objective: This study aimed to evaluate whether pre-treatment with LLLT reduces pain intensity at the injection site of local anesthesia in adult patients undergoing endodontic procedures. Methods: A randomized controlled split-mouth trial was conducted on 30 adult patients requiring bilateral endodontic treatment. Each patient received LLLT (635 nm, 10 J/cm², 210 mW, four 25-second cycles) on one side before anesthetic injection, while the opposite side served as a control. Pain intensity was measured immediately after injection using a 10 cm Visual Analogue Scale (VAS). Data were analyzed with the Mann-Whitney U test for group comparisons and subgroup analyses by age and gender, with a significance threshold of p<0.05. Results: The mean VAS pain score was 6.80 ± 1.24 for the LLLT-treated side and 6.93 ± 1.46 for the control side, with no statistically significant difference (p=0.612). Female participants reported higher pain scores than males in both groups, and younger patients experienced more intense pain compared with older participants. No participant reported complete absence of pain. Conclusion: Pre-treatment with LLLT did not significantly reduce injection-site pain compared with standard practice. Age and gender appeared to influence pain perception, but these trends were not statistically significant. Larger, multicenter trials with optimized laser parameters and stratified analysis are recommended to further investigate the clinical utility of LLLT in dental pain management