This study assessed whether systemic antibiotics are beneficial or harmful in patients who present with an acute periodontal abscess or pericoronitis, with or without systemic involvement, and, if antibiotics are beneficial, which type, dosage, and duration are the most effective. Medline, Embase, and the Cochrane Library were screened from 1948 up to 1 April 2022 for systematic reviews, randomised clinical trials (RCTs), and other studies. Dedicated websites were consulted for systematic reviews, clinical practice guidelines, and health technology assessments on the topic. Outcomes of interest comprised tooth survival, swelling, pain, tooth mobility, periodontal probing depth, suppuration, adverse effects, quality of life measurements, and medication required for pain relief. Overall, five guidelines, seven systematic reviews, 15 RCTs, and 34 other studies were identified and selected for full-text assessment, but none of them fulfilled the inclusion criteria. At present there is no single randomised or non-randomised controlled trial assessing the harms and clinical effectiveness of systemic antibiotics in adults with a periodontal abscess or pericoronitis.