Evaluation of the effects of photobiomodulation with different laser application doses on injection pain in children: a randomized clinical trial

The utilization of photobiomodulation (PBM) to decrease the experience of pain during the application of local anesthesia (LA) has been reported in a limited number of studies with children. However, currently, there is no complete consensus regarding its efficacy and application doses. The objective of the clinical trial was to assess the effects of PBM with three different laser application doses (with different power values) plus 10% lidocaine topical anesthetic and to compare them with placebo + 10% lidocaine topical anesthetic on LA injection pain in children. A prospective, parallel-arm, randomized, triple-blind clinical trial was conducted with 160 children aged 6 to 12 years (79 girls and 81 boys; 80 maxillary and 80 mandibular primary first molars). The children were divided into 4 groups with an equal number of subjects in each group. Before topical anesthetic usage, a laser with a power of 0.3 W, 0.4 W, and 0.5 W was applied in Groups 1, 2, and 3, respectively (a diode laser: 940 nm; continuous mode; 20 s for each group). The energy density was calculated as 69 J/cm², 92 J/cm², and 115 J/cm². A placebo laser was used in the fourth group. Injection pain was assessed subjectively and objectively with the Wong–Baker Faces Pain Rating Scale (PRS) and the Face, Legs, Activity, Cry, Consolability (FLACC) Scale. The data were analyzed using the Chi-square test (P < 0.05). The mean (± std) PRS scores were 1.35 ± 1.075, 1.37 ± 1.05, 1.07 ± 1.04, and 2.07 ± 1.09 for Groups 1, 2, and 3 and the placebo group, respectively. Additionally, the mean (± std) FLACC scores were 1.67 ± 1.50, 1.62 ± 1.90, 1.35 ± 1.74, and 2.75 ± 1.64 for Groups 1, 2, and 3 and the placebo group, respectively. Groups 1, 2, and 3 showed significantly lower pain scores than the placebo group (P = 0.02). However, no significant difference was observed between Groups 1, 2, and 3 according to either pain scale score (P = 0.948). In addition, no relationship was found in pain scores related to sex and jaw differences in any group (P = 0.321, P = 0.248). PBM delivered by a 940-nm diode laser plus 10% lidocaine topical anesthetic before the application of LA decreased injection pain regardless of the applied laser dose in this study.