Abstract
BACKGROUND: Pain and anxiety during palatal infiltration remain barriers to patient cooperation. The anesthetic delivery system may influence subjective outcomes and physiological stress responses, yet robust comparative data are lacking. MATERIAL AND METHODS: In this randomized, parallel-arm superiority trial, 200 healthy adults (≥18 years) were equally allocated into five groups (n=40) by block randomization with concealed allocation. Tested systems were conventional dental syringe (CDS), manual pressure syringe (MCJ), spring-activated pressure syringe (PCJ), needle-free jet injector (NFI), and computer-controlled local anesthetic delivery system (CCLAD). Each participant received 0.4 mL of 4% articaine with epinephrine (1:100,000) via standardized palatal infiltration by a single calibrated operator. The study was single-blind: outcome assessors and statisticians were blinded to allocation. The primary outcome was post-injection pain (VAS, 0-10cm). Secondary outcomes were dental fear (VAS pre/post), pulse rate, and oxygen saturation, recorded at baseline, during, and after injection. RESULTS: Mean VAS pain did not differ significantly across groups (overall p=0.380); adjusted analyses (ANCOVA including injection duration as covariate) confirmed no clinically relevant mean differences [95% CI within ±0.5 cm; Hedges' g <0.20]. MCJ showed slightly higher discomfort. All systems significantly reduced fear (p<0.05), with PCJ showing the largest reduction (ΔVAS-2.7). Pulse rate varied across groups (p<0.001), peaking in CCLAD and remaining most stable in MCJ; oxygen saturation was unchanged. No adverse events were observed. CONCLUSIONS: All systems were clinically safe and effective but differed in psychophysiological impact. Devices that reduce fear and stabilize vital responses, particularly those targeting PCJ and CCLAD, may help improve patient cooperation and the overall treatment experience.