Methionine challenge test: methyl mercaptan (CH3SH) response in periodontitis

Abstract

Halitosis, frequently associated with volatile sulfur compounds (VSCs) produced by oral microbiota, affects a large proportion of adults. Among VSCs, methyl mercaptan (CH3SH) is a critical biomarker for periodontitis-related halitosis due to its strong correlation with periodontal pocket depth and attachment loss. This study investigated the utility of a methionine challenge protocol to selectively stimulate CH3SH production and enhance the standardization of oral air-based screening for periodontal disease. Thirty adults were enrolled and divided equally into control and periodontitis groups. Mouth air samples were collected from oral cavity air using a straw-based sampling method connected to a portable gas-sensing device, which continuously monitored VSCs, including CH3SH and hydrogen sulfide (H2S), across eight time points. Participants underwent an 8 h fast prior to baseline oral air collection, followed by standardized toothbrushing. After a 60 min rest period, they swilled with a methionine solution, with oral air samples collected immediately after and at 10 min intervals for 40 min. Both groups showed increased CH3SH levels following methionine stimulation, with the periodontitis group exhibiting a significantly greater increase from pre- to post-stimulation (p < 0.001) and higher cumulative exposure (p < 0.001). In contrast, H2S levels remained consistently elevated in the periodontitis group but did not fluctuate significantly over time. Furthermore, correlations between CH3SH and H2S decreased immediately post-stimulation and gradually recovered in the periodontitis group. These findings indicate that the methionine challenge effectively induces CH3SH production linked to periodontal dysbiosis, supporting its potential as a non-invasive screening and indicator tool for the presence of periodontitis, rather than for staging disease severity. The protocol offers a promising approach to improve diagnostic accuracy while minimizing variability related to oral hygiene. (The study is registered with the Clinical Research Information Service under number KCT0010328.).