Elevation of a periosteal flap with irrigation of the bone for minor oral surgery reduces the duration of action of infiltration anesthesia.

The aim of this study is to assess the difference in duration of action after infiltration anesthesia when elevation of a periosteal flap (EPF) was accomplished with water or saline irrigation versus nonelevation of a periosteal flap (NEPF). The 57 patients in this study were under conscious sedation. A long treatment time of more than 1 hour was used. Instances where peripheral nerve block or opioids were administered and infiltration anesthesia over 2 fields were excluded before the study. Patients were included in either an EPF group (n = 29) or an NEPF group (n = 28). Statistically significant differences were detected in the initial dose of anesthetic (EPF: 4.3 +/- 1.4 mL, NEPF: 1.8 +/- 0.9 mL), the time until initial supplemental anesthesia (EPF: 38 +/- 26 minutes, NEPF: 65 +/- 27 minutes), and the frequency of anesthesia administration (EPF: 2.5 +/- 1.2 times, NEPF: 1.3 +/- 0.7 times). These results suggest that the duration of anesthesia action in EPF decreases to half compared with NEPF, even if the anesthetic was infiltrated in double the amount. Although supplemental anesthesia is required frequently in EPF, it is not efficacious. We speculated that the residual anesthetics in tissue were washed out by irrigation and hemorrhage and that supplemental anesthesia became ineffective because of leakage from the opened flap. Elevation of a periosteal flap reduces the effect of infiltration anesthetics.