Gum disease increases the probability of bad breath by 3.6 times.

31.8% of people worldwide have halitosis (bad breath). The cause of bad breath could be from the mouth itself, that is the most common cause, with up to 90% bad breath originating from the mouth.  Bad breath could also originate from outside the mouth (from the stomach for example).

The most common part of the mouth where bad odour emanates from is from the back top part of the tongue, from inside gum pockets caused by gum disease, and from loose or poorly maintained dentures or bridgework. Other causes of bad breath include a dry mouth (xerostomia), oral yeast infection (candidiasis), oral infection, and oral cancer.

In a recent study by Yeon-Hee Lee in 2023, 104 patients were examined for bad breath, with healthy control patients, and patients with gingivitis and periodontitis. 

A specialized sensor called a gas chromatograph was used to measure hydrogen sulfide (H2S) and methyl mercaptan (CH3SH) which are the main Volatile sulfur compounds that cause a bad mouth smell. 

The total volatile sulfur compounds were significantly higher (186.72 ± 374.83 parts per million) for patients with gum disease versus  19.80 ± 40.19 parts per million for healthy patients without active gum disease. Both the mild form of gum disease (gingivitis) and the more advanced form (periodontitis) caused a significant increase in the volatile sulfur compounds that cause bad breath. 

More details here 

Lee, YH., Shin, SI. & Hong, JY. Investigation of volatile sulfur compound level and halitosis in patients with gingivitis and periodontitis. Sci Rep 13, 13175 (2023). https://doi.org/10.1038/s41598-023-40391-3

https://www.nature.com/articles/s41598-023-40391-3

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