Objective: This study aimed to analyze the influence of storage conditions of local anesthetic solutions in the inflammatory reaction after injection in rats.
Study design: Twenty-four rats received in their oral mucosa the injection of 2% lidocaine with epinephrine 1:100.000 solutions (LA) submitted to the following storage conditions during a twelve-month period: G1--inside the original packaging, in refrigerator (5±1°C); G2--inside the original box, under light shelter, at room temperature; G3--outside the original box at room temperature (exposed to artificial light for 12 hours/day) and G4--brand new solution. For the controls tests, 0.9% sodium chloride solution was injected in the opposite side. After 6 and 24 hours, three animals of each group were sacrificed and their maxilla along with the soft tissue were removed and submitted to histological analysis (HE).
Results: The pH of LA was measured before and after the storage period and no statistically differences were observed between G1 and G4, but both were different from G2 and G3. All the scores of the testing solutions were higher than their respective negative controls, except for G1 at 6 hours. The order of the scores of inflammation after 6 hours was G3>G4>G2=G1. After 24 hours the order was G3>G2>G1>G4.
Conclusion: The study showed that the method of storage can influence the pH and the level of inflammatory reaction after the injection of 2% lidocaine with epinephrine 1:100.000.