Relief of Injection Pain During Delivery of Local Anesthesia by Computer-Controlled Anesthetic Delivery System for Periodontal Surgery: Randomized Clinical Controlled Trial. 
Pain from local anesthetic injection makes patients anxious when visiting a dental clinic.  This study aims to determine differences in pain according to types of local anesthetizing methods and to identify the possible contributing factors (e.g., dental anxiety, stress, and sex).  Thirty-one patients who underwent open-flap debridement in maxillary premolar and molar areas during treatment for chronic periodontitis were evaluated for this study.  A randomized, split-mouth, single-masked clinical trial was implemented.  The dental anxiety scale (DAS) and perceived stress scale (PSS) were administered before surgery.  Two lidocaine ampules for each patient were used for local infiltration anesthesia (supraperiosteal injection).  Injection pain was measured immediately after local infiltration anesthesia using the visual analog pain scale (VAS) questionnaire.  Results from the questionnaire were used to assess degree of pain patients feel when a conventional local anesthetic technique (CNV) is used compared with a computer-controlled anesthetic delivery system (CNR).  DAS and PSS did not correlate to injection pain.  VAS scores were lower for CNR than for CNV regardless of the order in which anesthetic procedures were applied.  VAS score did not differ significantly with sex.  Pearson coefficient for correlation between VAS scores for the two procedures was 0.80, also indicating a strong correlation.  Within the limitations of the present study, relief from injection pain is observed using CNR.