Alveolar osteitis (AO) or dry socket after dental extractions is a common postoperative complication characterized by the presence of severe pain associated with an empty socket. Although some authors consider AO to be related to an alteration of the blood clot, the underlying etiology remains unclear, and recent reports suggest that bacteria might play an important role. A systematic review was made, compiling relevant references from PubMed, the Cochrane Library, Scopus and the Web of Science databases to determine which bacteria have been identified in AO sockets after dental extractions. Papers published between 1980–2019, identifying the bacteria present in AO sockets after tooth extractions, were included. Data were displayed in tables, and a descriptive analysis was carried out. After the screening process, four papers were analyzed, comprising a total of 138 samples from 138 patients with AO. The most commonly detected bacteria were Prevotella, Fusobacterium, Parvimonas and Peptostreptococcus. Two studies also showed the microbiota of patients that developed AO after dental extractions to be apparently different from that of patients without postoperative complications. These results indicate that bacteria may play an important role in the pathogenesis of AO, though further studies are needed to confirm these findings.