ORIGINAL ARTICLE Buffered 2% articaine versus non-buffered 4% articaine in maxillary infiltration: randomized clinical trial Klinger Souza Amorim 1 & Vanessa Tavares Silva Fontes 2 & Anne Caroline Gercina 1 & Francisco Carlos Groppo 1 & Liane Maciel Almeida Souza 2 Received: 3 September 2020 /Accepted: 29 October 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract Objectives This randomized, triple-blind, crossover clinical trial aimed to evaluate the efficacy, onset, length of pulp and soft tissue anesthesia, and pain during injection of 2% buffered articaine and 4% non-buffered articaine solutions. Methods Each volunteer received two maxillary supraperiosteal anesthesia infiltrations in canine area. The infiltrations were performed at two different sessions using a different local anesthetic solution for each session, and the anesthetic injection speed was always 1 mL/min. The assessment of the onset and length of pulpal and soft tissue anesthesia was performed with the pulp electrical test “pulp tester” and the esthesiometer kit, respectively. Volunteers marked pain during injection on a visual analog scale (VAS). The anesthetics solutions pH was evaluated through the pH meter equipment. Results There was no difference between the two anesthetic solutions (onset of soft tissue anesthesia, p = 0.5386; length of soft tissue anesthesia, p = 0.718; onset of pulpal anesthesia, p = 0.747; length of pulpal anesthesia, p = 0.375), except for pain during the injection which was lower when buffered 2% articaine was used (p = 0.001) and the pH. The pH analysis revealed that the solutions differed from one another (p < 0.01). Conclusion The 2% buffered articaine solution provided the same anesthetic properties then 4% unbuffered articaine with a great reduction in pain during injection. Clinical relevance The possibility of use 2% buffered articaine solution instead of 4% articaine maintaining the same anesthetic properties with a great reduction in pain during injection and half of the anesthetic salt concentration. Keywords Buffering . Articaine . Pain . Local anesthetic . Buccal infiltration Introduction As first obtained in the laboratory, local anesthetics are bases compound, weak soluble in water, and unstable when exposed to the air. In order to make feasible their injection, these bases are combined with hydrochloric acid to form local anesthetic salt, in which form they are quite soluble in water and comparatively stable, becoming mostly a solution with an approximate pH of 5.9 [1, 2]. Usually, epinephrine is added into local anesthetics solu- tion at a ratio of 1:100,000 or 1:200,000 to balance blood vessel dilatation, leading to blood vessel constriction at the site of application, prolonging anesthesia duration. However, the sodium bisulfite is added as an antioxidant to stabilize that kind of vasoconstrictor, which makes the solution even more acidic (pH approximately 3.5). Injection of these acidic solu- tions may consequently present negative effects, such as burn- ing, some degree of tissue injury, relatively slow-onset anes- thesia, and unsatisfactory activity in the presence of infection and inflammation (even lower pH) [1, 3]. For instance, in a solution with a pH of approximately 3.5, only a small amount of the local anesthetic will be in its base form available to cross through the axon membrane and act immediately after injection. To compensate for the low pH, the organism itself performs a physiological buffering * Vanessa Tavares Silva Fontes vanessa.tavares.se@gmail.com 1 Pharmacology, Anesthesiology and Therapeutics Department, Piracicaba Dental School, University of Campinas, 901 Limeira Avenue, Piracicaba, São Paulo 13414-903, Brazil 2 Oral surgery and anesthesiology area of Dentistry Department, Federal University of Sergipe, St Cláudio Batista, Cidade Nova, Aracaju, Sergipe 49060-108, Brazil Clinical Oral Investigations https://doi.org/10.1007/s00784-020-03674-x