Due to the analgesic effect of laser, researchers studied the effect of LLLT diode laser in reducing the injection pain associated with dental local anesthesia. Previous studies used different pain scales; either modified behavioral pain scale (MBPS) [14], or FACES Scale [15], or visual analog scale (VAS) [16] [9] [17] [14], or Face, Legs, Activity, Cry, Consolability (FLACC) scale [10]. In our study FACES Scale was adopted because it shows a close linear relationship with visual analogue pain scales for kids of three-year age and older. It is easy to administer and requires no equipment except for the photocopied faces [13]. And this scale measures how children feel, and pain degree has not been assessed by another person, so this added more reliability for pain degree evaluating.
Researchers used different variables trying to find the most appropriate parameters to get the best effect. To the best of our knowledge, there was no published study tried LLLT diode laser of 635 nm for 120 seconds as preanesthetic factor to decrease pain of injection. So, the current research adopted this wave length and conducted this clinical trial in children because most of prior research were conducted on adults, except few published studies were directed in children, such as Seraj, Bavaghar et al. 2023 besides the study of Shekarchi, F., et al., 2022, and Uçar, G., Ü. Şermet Elbay, 2022. Thus, we compared our study results with similar available studies in both adults and children.
The current study revealed a lower mean of pain degree in LG (1.20) than that of CG (2.50), and this result disagree with Tuk, van Wijk et al. 2017 study which conducted in adults and indicated that preinjection LLLT did not effectively decrease the pain felt during local anesthetic injections before third molar surgery,; where targeted injection site was irradiated twice with 198 mW continuous wave for 30 seconds with a 0.088 cm2 focal spot at an applied energy of 5.94 J and fluence of 67.50 J/cm2 [18], and this disagreement may due to the different parameters used in each study.
While the current study agree with that of Sattayut, 2014 (790 nm, 2 minutes), Jagtap et al.,
2019 (660 nm, 3 minutes) and Ghabraei, S., et al., 2020 (980 nm, 1 minute) in adults [16] [9] [17]. As well as, agree with the study of Shekarchi, F., et al., 2022 (808 nm, 1 minute), Uçar, G., Ü. Şermet Elbay, 2022 (810 nm, 20 seconds), and Seraj, Bavaghar et al. 2023 (810 nm, 13 seconds) in children [15] [10] [14]. However, the difference in pain degree between laser group and control group was statistically significant in only two of those above-mentioned studies, in Jagtap et al., 2019 in adults and Uçar, G., Ü. Şermet Elbay, 2022 in children [9] [10], and it was statistically significant in our study as well.
Thus, according to previous results, LLLT diode laser (635 nm; continuous mode; 100 mW; 48.0 J/cm2) decreased pain level of local anesthesia injection with superiority over 20% Benzocaine topical anesthetic gel.
In this research there was no effect of the order of technique, patient gender, place of injection, and previous dental experiment on pain degree in both methods. As well as; there was no significant difference between positive and absolute positive children in pain degree evaluation of both methods. Unfortunately, there was not any available research about using LLLT in topical anesthesia that studied those variables, so we could not compare our results with similar research. However, maybe we could not find any effect of those variables on pain degree due to choosing only cooperative children.
It is important to shed light on the positive effect of the basic behavior management techniques, like tell-show‐do, and the distraction impact of the protective glasses were used during LLLT administration, which may affect the assessment of pain degree by the child, and this psychological factor may tip the equation in favor of the laser.
Unfortunately, our sample size was small because it was so difficult to convince parents with safety of LLLT, on the other hand it was not easy to find cooperative children to accept treatment procedure. Thus, we recommend to do further studies with larger sample size.