Potential Shifts in the Oral Microbiome Induced by Bariatric Surgery-A Scoping Review

Background: The oral microbiome differs in obese patients compared to normal-weight subjects. Microbiologic shifts very often appear after surgical interventions such as bariatric surgery (BS) and in immunocompromised patients. However, the oral microbiome composition and load in subjects after bariatric surgery are unclear. Aim: The aim of this review is to summarize the current state of the art related to the oral microbiome shift induced by bariatric surgery and to discuss its implications on oral cavity health. Methods: Electronic databases: PubMed/Medline, Web of Science, and Cochrane Library were searched for articles published up to March 30, 2025, describing prospective studies focused on changes in the oral microbiota of patients who underwent bariatric surgery. Results: Eight studies measuring the oral microbiome with different approaches-16S ribosomal RNA (16S rRNA) sequencing, polymerase chain reaction (PCR), culture, and matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI TOF MS)-were included in this review. The following bariatric techniques were used: sleeve gastrectomy, Roux-en-Y gastric bypass, Omega loop gastric bypass, and laparoscopic gastric plication. The follow-up period ranged from 3 to 12 months. The results of microbiologic studies were unequivocal. There was an increment in Streptococcus mutans reported, high levels of Candida species, and increased rates of some periodontitis-associated bacteria (Porphyromonas gingivalis) in the post-bariatric surgery period, though some studies suggested a shift towards non-pathogenic composition of the oral microbiome in prospective observations. Conclusions: The local oral microbial homeostasis becomes strongly impacted by the bariatric surgical treatment itself as well as its consequences in the further post-operative period. Therefore, obese patients undergoing BS require very careful dental observation.