Our goal is to compare the amount of pain from immediate and delayed palatal injection following buccal infiltrate injection. In this randomized triple blinded, clinical trial, 92 patients referring to the dental school of Kermanshah University of Medical Sciences will be chosen. Inclusion criteria: People of 18 to 50 years of age, needing restorative treatment of maxillary premolar teeth. Exclusion criteria: use of sedatives and anti-depressant medications during two weeks prior to the injection. Patients are randomly divided into two groups of 46. Buccal injection will be performed using lidocain in one group and articaine in the other group; while palatal injection will be performed using lidocain in both groups. For each patient, injections will be performed twice with an interval of two weeks. Once, the palatal injection will be randomly performed immediately after the buccal injection, while the other time, it will be performed with a 10 minute delay. During the buccal injection, 1.8 milliliters of anesthetic agent, during 60 seconds, at 3 to 4mm penetration depth at the maxillary premolar vestibule will be delivered by the first operator, and during the palatal injection 0.3 milliliters will be delivered during 10 seconds, and 1cm far from the marginal gingiva of premolar teeth, at 3 to 4mm penetration depth by the second operator. The extent of pain from injection will be measured after buccal and palatal injections using the Visual Analogue Scale of pain. Palatal injection will be delivered by the second operator who will not be present in the room during the buccal injection. A dark tape will cover each anesthetic cartridge.