Assessing the efficacy of the comfort-in needle-free injection system for managing pain and anxiety during pediatric dental injections: a randomized split-mouth clinical trial

Abstract Background Conventional local anesthesia may increase pain and anxiety in pediatric dental patients. This randomized split-mouth clinical trial compared the Comfort-in needle-free injection system with conventional dental injection in children undergoing primary molar pulpotomy. Methods Sixty children aged 5–8 years requiring bilateral pulpotomy of primary first molars were included. Each child received conventional local anesthesia and Comfort-in anesthesia in separate sessions at least one week apart. Physiological parameters were recorded before anesthesia, after anesthesia, and after pulpotomy. Pain was assessed using the Face, Legs, Activity, Cry, Consolability (FLACC) scale and the Wong-Baker Faces Pain Rating Scale (WBFS). The amount of anesthetic solution, duration of soft-tissue anesthesia, postoperative complications and patient preference were recorded. Results Observer-rated pain during anesthesia administration was significantly lower with Comfort-in than with conventional injection (p = 0.006). No statistically significant differences were detected between the two injection techniques in pain scores recorded during the pulpotomy procedure (p > 0.05). Systolic blood pressure before and after anesthesia was significantly higher in the conventional injection group (p = 0.015 and p = 0.029, respectively). Comfort-in required significantly less anesthetic solution (p < 0.001) and was associated with a shorter duration of soft-tissue anesthesia (p = 0.002). Postoperative complications were significantly more frequent after conventional injection (p = 0.031). Conclusion Comfort-in was associated with lower observer-rated pain during anesthesia administration, whereas no differences were observed in self-reported pain or pain during pulpotomy procedures. Although some physiological differences were statistically significant, their absolute magnitude was small. Patient preference was equally distributed between the two techniques. These findings indicate differences between the injection techniques in specific outcomes but do not demonstrate an overall advantage of either technique. Trial registration The trial was retrospectively registered with ClinicalTrials.gov (NCT07585812). First submitted: April 30, 2026.