Trench Mouth is a disease of sudden onset, with necrosis of the gingival papilla and ulcers seen around the gingival tissues of the mouth. It is extremely painful with fetid breath. It is so painful that it becomes difficult to eat. The gum tissue is swollen, red and bleeds easily. The disease in called Acute Necrotizing Ulcerative Gingivitis. The disease represents a group of various normal oral bacteria that becomes overgrown with a significant quantity of anaerobic bacteria, Spirochetes and Fusobacteria. Historically it was believed to be contagious, even though it is not.
Life in WW1 trenches provided the needed catalyst for this disease to become a problem. The pathology is something like this. Normal oral flora consisted of numerous bacteria, both gram negative and gram positive. Normal oral flora also contains funguses and viruses. Generally, if the oral hygiene is good there is no problem. However, if for some reason the situation changes, as life in the trenches has been shown to do, the trenches provided the catalyst necessary to proceed from health to disease.
Poor oral hygiene allows for a huge build up of oral bacteria. After 10 to 14 days with poor oral hygiene, the oral bacterial will shift from a gram positive bacteria to a more gram negative bacteria. This shift begins the process of gingivitis and periodontal disease, but at this time there is usually no pain. Now bring in the environmental factors of the trenches, and you can have chronic painless problem become an acute problem with severe oral pain. Stress both physical and mental is known to enhance the condition of Trench Mouth. In modern times Trench Mouth was seen in college towns during final week. Students not sleeping, smoking, not eating properly and stressed over final exams always provided a few cases of Trench Mouth. The immune system slightly depressed would also allow for an overgrowth of harmful bacteria.
In WW1 the treatment would have been salt water rinses, hydrogen peroxide mouth washes, particularly in the infected portion of the mouth and improved oral hygiene. An added benefit would be removal of the victim from the trench life away from the filth, and stress and all that trench life involved.
Poor nutrition, filth and numerous other factors related to trench life, helped enhance disease in the trenches.
For more info about diseases in the trenches, check out the other parts of my series: