Bariatric surgery (BaS), used to treat severe obesity, may increase the risk of bad breath and dental diseases, including gum disease and caries. This study was recently published in the International Dental Journal.
Furthermore, bariatric surgery, combined with periodontitis, may reduce gut microbial diversity and worsen alveolar bone loss, emphasizing the need for coordinated care between dental and bariatric teams, the authors wrote.
“BaS exacerbates obesity-related microbial dysbiosis, increasing the risk of periodontal and dental diseases,” wrote the authors, led by Aaya Shahin of the Hebrew University of Jerusalem (Int Dent J, November 22, 2025, Vol. 76:1, 104026).
The study investigated how obesity and bariatric surgery affect oral health and intestinal flora in adult patients with obesity and in mice with induced experimental periodontitis. Periodontitis was triggered after an antibiotic regimen followed by a three-day washout period. Mice were grouped by treatment type and by when their microbiome samples were collected before and after surgery. Oral plaque samples were gathered before and after the procedure, they wrote.
In the human case-control study, researchers included 36 presurgery patients, 14 postsurgery patients, and 56 controls, conducted dental exams at designated timepoints, and collected both subgingival and supragingival plaque samples.
Obese mice that underwent bariatric surgery showed increased oral microbial diversity. Experimental periodontitis alone significantly reduced gut microbiome diversity, regardless of bariatric surgery. Comparing pre- and postsurgery samples revealed similar trends, including a significant rise in microbial diversity (p = 0.002) and the development of distinct microbial communities (p = 0.001), they wrote.
In the mouse model, bariatric surgery combined with experimental periodontitis caused similar microbial shifts and substantial alveolar bone loss. In humans, pre-bariatric surgery patients had higher oral microbial diversity and more periodontitis-associated bacteria than the controls. These levels, along with caries- and halitosis-associated bacteria, increased further after surgery.
However, the study had limitations. The clinical cohort was small and had a short follow-up period, which may have made it harder to detect long-term changes, the authors noted.
“Larger, long-term studies are needed to confirm these findings and further elucidate the biological mechanisms linking obesity, BaS, oral dysbiosis, and systemic health outcomes,” they wrote.
