Difficulties with opening the mouth (trismus; also known as jaw hypomobility) are common. These problems range from minor disturbances all the way to complete inability to open the mouth. Trismus can be a temporary problem (of varying severity) on a short time scale, but can also last for a considerable period of time, or may be permanent.
Trismus can be a symptom or a consequence of disease, or may arise as a consequence of treatments (in particular radiotherapy or some surgical interventions). Depending on the severity and duration of difficulties with opening the mouth, a number of potentially serious additional health issues can arise. Severe and lasting forms of trismus not only have a negative impact on quality of life in general, there can be issues with malnutrition from eating problems, oral hygiene can be difficult and lack of it can lead to problems with gum disease and dental decay. Dental treatment in these circumstances can be challenging, in some cases even impossible. Severe trismus also affects speech negatively and altogether can be a cause of long term mental health issues. It is therefore important for those at risk to make any reasonable attempt to prevent trismus from developing mental health issues in the first place.
Trismus can be caused (or made more likely to develop) by several different conditions. These include infections, trauma, surgical treatment, dental treatment, joint disorders, radiotherapy, some drugs, congenital conditions and some other rare disorders.
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