Comparison of anterior middle superior alveolar (AMSA) injection and buccal infiltration as single-injection anesthetic techniques for orthodontic extraction of maxillary first premolars: a randomized split-mouth clinical trial.

Background: Pain and anxiety regarding local anesthetic injections are common concerns during orthodontic tooth extraction. Single-injection anesthetic techniques may reduce patient discomfort while maintaining adequate pain control by eliminating the need for separate buccal and palatal injections. This study compared the anesthetic efficacy, pain perception, onset and duration of anesthesia, and postoperative analgesia linked to anterior middle superior alveolar (AMSA) injection versus buccal infiltration for maxillary first premolar extraction. Methods: This assessor-blinded randomized split-mouth clinical trial enrolled 42 orthodontic patients (mean age, 18.5 ± 3.12 years; range, 13-24 years) requiring bilateral extraction of maxillary first premolars. The participants received an AMSA injection and buccal infiltration in the contralateral quadrant during two visits, spaced 10 days apart. Both techniques utilized 1.2 mL of 4% articaine with adrenaline (1:100,000) via a 30-gauge needle. The outcomes included anesthetic success, pain during injection and extraction assessed on a visual analog scale (VAS; 0-100 mm), onset and duration of anesthesia, and postoperative analgesia. Anesthetic success was defined as completion of extraction without supplemental anesthesia. Supplemental anesthesia was administered when intraoperative pain exceeded 44 mm on the VAS, and the primary anesthetic technique was classified as unsuccessful. McNemar's test and the paired Student's t-test were used for statistical comparisons. Results: Anesthetic success rates were 85.7% for AMSA injection and 78.6% for buccal infiltration, with no significant difference (P = 0.58; matched OR 1.60, 95% CI 0.52-4.92). AMSA injection produced a significantly faster onset and longer duration of palatal anesthesia, whereas buccal infiltration produced a significantly faster onset and longer duration of buccal anesthesia (P < 0.001). AMSA injection caused greater injection-related pain (P < 0.001; Cohen's dz = 0.68), but lower extraction-related pain (P < 0.001; Cohen's dz = 0.82). Buccal infiltration achieved a longer postoperative analgesia duration (P = 0.006; Cohen's dz = 0.57). Conclusions: Both techniques are effective single-injection options for maxillary first premolar extraction. AMSA provided superior intraoperative comfort and palatal anesthesia, but inflicts greater injection discomfort, while buccal infiltration offered greater injection comfort and longer postoperative analgesia.