Bacterial infections are a common occurrence in dental practice, often resulting in the formation of abscesses where anaerobic bacteria are predominant. Both oxygen and metronidazole are considered as effective agents for eliminating anaerobes. However, regardless of the dominance of anaerobes, abscesses will always be polymicrobial, also including facultative anaerobes such as Enterococcus faecalis. The aim of this study is to evaluate the efficacy of metronidazole in managing abscesses and to assess the potential of oxygen exposure to control E. faecalis activity. This study combines two complementary research approaches: (1) a study of medical records following metronidazole monotherapy for abscess treatment, and (2) an in-vitro analysis examining the impact of oxygen circulation on E. faecalis. Following metronidazole monotherapy, 93.33% of abscess cases demonstrated significant clinical improvement upon follow-up assessment. In vitro analysis indicated the absence of gas or odor production under oxygenated treatment conditions, whereas anaerobic conditions within the E. faecalis growth medium resulted in gas and odor formation. Enterococcus faecalis is a prevalent commensal bacterium commonly found in the human microbiota. Due to its inherent resilience, total elimination of E. faecalis is exceedingly challenging, and potentially unachievable. The complex anatomy of the root canal system, characterized by accessory canals and apical deltas, offers a protected niche for E. faecalis, making it inaccessible to conventional therapeutic interventions. Consequently, a paradigm shift may be necessary, transitioning from an eradication-based approach to a strategy centered on controlling the microorganism's proliferation and utilizing its commensal properties that also interact with the immune system to mitigate potential harm, rather than striving for absolute sterility.