What Causes Trismus?

Trismus is a condition where one or both front teeth are missing. There are two types of trismus: primary (in which only one tooth is affected) and secondary (where both front teeth are affected). Primary trismus affects the top front teeth while secondary trismus affects the bottom ones. These conditions may occur at birth, during childhood, adolescence, adulthood or even later in life.

The cause of trismus is not known but it appears to be hereditary. There have been cases when doctors were able to identify the gene responsible for causing trismus. Another theory suggests that trismus may result from a genetic defect in the jaw bone or teeth.

Other theories suggest that certain environmental factors may play a role in causing trismus. Some studies show that children born with trismus have a higher risk of developing other health problems such as asthma, allergies, diabetes and epilepsy.

Treatment Options for Trismus

There are no treatments available to correct trismus. If your child has had trismus before then there is nothing that can be done to prevent it from happening again. Treatment options include surgery, braces and orthodontics.

Even with treatment, the outcome is uncertain as there is a possibility that the teeth will relapse back to their original positions.

How Long Does Trismus Last?

Trismus tends to relapse. Even after successful treatment, the teeth may return to their original position. In some cases, the condition may even get worse when both top and bottom front teeth are affected. This occurs because the jaw stops growing but the teeth keep growing. This is called asymmetrical growth.

What Is The Long-Term Outlook Of Trismus?

When trismus is caused by genetic factors, the outlook is not very good. Even with treatment, there is a possibility that your child’s teeth will relapse back to their original position. There may also be a relapse of the condition even if your child does not suffer from it at birth.

What Are The Complications Of Trismus?

Trismus is not usually a life-threatening condition. However, since the condition involves the upper jaw, there is a higher risk of developing other conditions such as sleep apnea and temporomandibular joint dysfunction. The longer the condition lasts, the higher these risks become. If left untreated, the complications can affect your child’s quality of life in a negative way.

What Are The Long-Term Effects Of Trismus?

The long-term effects can vary from child to child. If left untreated, the condition can damage your child’s appearance as they grow older. Other than that, the condition may also cause speech problems especially when it affects both upper teeth. Children with trismus are more likely to experience difficulties with their social skills since they will not be able to smile or laugh properly. This will hinder their ability to communicate and socialize with other children.

What Is The Cause Of Trismus?

Trismus is a fairly rare condition. It occurs in only about 1 out of every 50,000 to 100,000 births. The exact cause of the condition is unknown but several theories have been put forward to explain it. Some doctors believe that trismus is a congenital defect while other believe it is caused by a combination of factors.


Other than genetics, no other risk factors have been identified. It is believed that children may be born with trismus if there is a defect in the muscles or bones that control the jaw. It has also been noted that children with cleft lips and palates are more likely to develop trismus.

Neurological factors

There are studies showing that certain neurological disorders can cause trismus. These may include muscular dystrophy and certain types of cerebral palsy.

How Is Trismus Diagnosed?

The easiest way to spot trismus in your child is to look at their smile. Children with the condition will have a forced smile that will cause their upper and lower front teeth to touch. It will mostly only be noticeable when your child opens their mouth wide.

Sources & references used in this article:

Criteria for trismus in head and neck oncology by PU Dijkstra, PM Huisman, JLN Roodenburg – International journal of oral …, 2006 – Elsevier

Trismus in head and neck oncology: a systematic review by PU Dijkstra, WWI Kalk, JLN Roodenburg – Oral oncology, 2004 – Elsevier

Radiation-induced trismus in head and neck cancer patients by ML Kent, MT Brennan, JL Noll, PC Fox, SH Burri… – Supportive care in …, 2008 – Springer

Trismus and pain after removal of impacted lower third molars by AG Garcia, FG Sampedro, JG Rey… – Journal of oral and …, 1997 – Elsevier

Trismus: aetiology, differential diagnosis and treatment by PJ Dhanrajani, O Jonaidel – Dental update, 2002 –

Exercise therapy for trismus in head and neck cancer by PU Dijkstra, MW Sterken, R Pater, FKL Spijkervet… – Oral oncology, 2007 – Elsevier