Aims: The aim of this study was to evaluate the vestibular-palatal diffusion of 4% articaine with epinephrine 1:100,000 and 1:200,000, in impacted maxillary third molar extractions, without palatal injection. Materials and Method: Two hundred teeth were selected from patients age 15 to 46. Patients were divided into 4 groups: 1A, were anesthetized with 4% articaine 1:100,000 and the surgery was initiated 5 minutes following anesthesia. 1B, used 4% articaine 1:100,000 but the surgery was started 10 minutes after anesthesia. 2A, used 4% articaine 1:200,000 the surgery was started 5 minutes after. 2B, used 4% articaine 1:200,000 but 10 minutes was allowed for anesthetic diffusion before the initiation of in groups (50 extractions each) only buccal vestibule anesthesia was initially administered (i.e. no palatal injections were used). Results: The rate of sufficient vestibule-palatal diffusion, as determined by the lack of necessity of supplemental palatal anesthesia, was: 1A(84%), 1B(98%), 2A(78%), 2B(82%). Chi-square (X2) and residual analyses showed that a higher vestibule-palatal diffusion was obtained using 4% articaine 1:100,000 with a period of 10 minutes (p<0.05). Conclusions: Most of the extractions could be performed only with vestibule anesthesia. However, vasoconstrictor concentration and the time interval between administration of the anesthetic and initiation of surgery did influence buccal vestibule-palatal diffusion of 4% articaine in the extraction models used.