Definition

Microstomia is a medical condition characterized by a small oral opening, which can create various challenges in performing daily activities. It can also result in impaired nutrition and quality of life, and may even be a cosmetic issue. However, defining microstomia is difficult because the optimal mouth shape is subjective and varies based on cultural and temporal factors. Infections or inflammations of the teeth may also make it difficult to open the mouth, but this does not fall under the category of macrostomia, as it is neither permanent nor caused by structural damage.

Individuals with microstomia experience limitations in both their physical capabilities and social interactions. Microstomia commonly leads to limited social contact and humiliation due to difficulties in speaking correctly and the shape of the mouth.

Causes

Microstomia can be caused by various factors, which may include:

• Burns to the mouth are caused by heat, electricity, or chemicals that cause scarring with contraction. Typically, these injuries are grade 3. This is the most common cause of microstomia.
• A facial trauma that results in contractures and scarring.
• Reconstruction after the excision of facial tumors or skin cancers is less frequent now that more advanced reconstruction techniques have been developed.
• Scarring-causing inflammation of the oral mucosa caused by Stevens-Johnson syndrome (an allergic reaction to the skin and mucosa, typically caused by medications).
• Jaw joint pathologies.
• Post cleft lip surgery.
• Radiation therapy to the head and neck.
• Genetic disorders such as Freeman-Sheldon syndrome, Hallermann-Streiff syndrome, mouth-palate dysplasia, Fine-Lubinsky syndrome, epidermolysis bullosa, Down syndrome, Plummer-Vinson syndrome, Treacher-Collins syndrome, Pierre-Robin syndrome, Fine-Lubinsky syndrome, Schwartz-Jampel syndrome, Burton skeletal dysplasia, Leopard syndrome, and Moebius syndrome are rare.
• Asthma, esophageal dysmotility disorders, sclerodactyly, and telangiectasia syndrome variants of scleroderma are some autoimmune diseases that can cause the skin on the face to contracture or shorten. This can cause microstomia.

Risk factor

Microstomia is more likely to occur in males and adolescents due to their age and gender.

Symptoms

Microstomia impairs the function of the oral cavity, leading to the following impacts:

• Strict mandible opening.
• Difficulties with speech, particularly articulation.
• Difficulties with swallowing result from a small mouth that cannot expand sufficiently to allow food to enter and be chewed. Dietary issues can lead to nutritional complications, including, but not limited to, weight loss, lethargy, fatigue, pallor, and growth disorders in children.
• A drinking disorder.
• Uncontrolled salivation is the cause of excessive drooling.
• The inability to brush teeth effectively contributes to poor oral hygiene, resulting in dental complications such as cavities and foul odor.
• Strange facial expressions.
• Additional symptoms may be attributed to genetic or autoimmune factors that are not conventional microstomia causes.

The decline in function differs among individuals based on their adaptation to the microstomia condition.

Diagnosis

It can be difficult to determine what is considered a small mouth due to the fact that the shape of the mouth varies from person to person. Generally, the distance between the upper and lower incisors during maximal mouth opening is used to diagnose this condition. In adults, the minimum distance that is considered normal is three to four fingers or 51 to 60 mm.

However, the diagnosis of microstomia is not solely based on mouth size, but also on the functional difficulties experienced by the individual. Once diagnosed, the underlying cause must be identified for proper treatment.

No particular laboratory, radiographic, or other further tests are available for microstomia. This examination is conducted to investigate microstomia, which is considered to be attributed to an underlying medical condition or genetic problem.

An ECG examination is necessary to identify cardiac damage and electrical conduction abnormalities in cases of microstomia resulting from electrical burns.

Management

Various guidelines are available for microstomia therapy, but none have achieved general acceptance. Non-surgical therapy mostly targets minor instances, namely by:

• Denture utilization.
• Prosthetics use.
• Utilize a mandibular splint.
• Exercises to aid patients in adjusting to microstomia.
• Physiotherapy can also be used to enlarge the mouth cavity.
• To facilitate oral hygiene, choose a toothbrush with a small head, use fluoride toothpaste, and rinse your mouth with 0.12% chlorhexidine. Regular application of fluoride gel using a cotton swab can help reduce the progression of tooth decay.

This non-invasive treatment can help reduce the restrictions created by microstomia, facilitating oral hygiene, eating, and speech, ultimately enhancing the individual's quality of life. If non-surgical treatments have been attempted and functional restrictions persist, surgery may be considered.

Microstomia can be fixed with surgery to restore the natural size of the mouth opening and improve the patient's appearance. Mild cases can be fixed easily, but severe cases may need a more complicated repair, sometimes done in more than one step. Surgical treatment is based on the cause and severity of microstomia, taking into account the disability it causes. Surgical therapy works best for treating microstomia caused by trauma.

Calcinosis cutis, Raynaud's phenomenon, esophageal dysmotility disorders, sclerodactyly, and telangiectasia syndrome are some of the factors that can cause microstomia. Surgery is not recommended for these conditions because the incision can be difficult to heal.

Complications

Dental decay, including cavities, and infections of the teeth and gums are the most frequent complications of microstomia, excluding cosmetic issues. This phenomenon arises from many factors, with challenging access to clean teeth being the foremost. Additionally, dryness of the buccal mucosa and gastric acid reflux are additional conditions that may be present in conjunction with microstomia. A visit to the dentist is advised every three to six months to ensure proper oral hygiene and good dental health.

Complications of surgery for microstomia may involve challenging intubation, surgical procedure failure, and the development of recurring scars leading to recurrent microstomia.

Prevention

There are several pieces of oral equipment available to help prevent microstomia.

Microstomia prevention devices are user-friendly and do not require a full teeth set. The dentist will decide on the procedure for using this equipment.

When to see a doctor?

If you notice symptoms of microstomia or struggle with mouth opening, it is recommended that you seek medical advice.