Misalignment of teeth, also known as malocclusion, can result in functional problems including poor oral hygiene, pain, and difficulties when eating and speaking

Misaligned teeth or jaws, or malocclusion, is when teeth do not meet correctly when bitten together. Typically classified into three major groups, these categories are:

Class 1 malocclusion

Class 1 malocclusion when the upper and lower jaw are in their proper position, but the teeth are overcrowded


Class II malocclusion

Class II malocclusion when the teeth protrude over the lower teeth;


Class III malocclusion

Class III malocclusion when the lower teeth and jaw overlap the upper teeth.

According to an article published in the European Journal of Paediatric Dentistry, malocclusion affects 56% of people worldwide.

In Malaysia, a study indicates that 48.6% of adults have Class I, while 16.2% and 26.8% have Class II and III malocclusion. In Singapore, according to another study, Class I, II, and III, malocclusions affect 48.1%, 26.3% and 22.4% of adult men, respectively.

While modern orthodontics categorise malocclusions according to whether or not the upper and lower teeth meet normally, Dato’ Dr How Kim Chuan, Consultant Orthodontist at the Imperial Dental Specialist Centre, classifies the condition based on how it affects the teeth, soft tissues, and bones.

“If a patient’s bite (occlusion) is normal, but they have dental misalignment or crowding, this is classified as level 1 malocclusion in my practice. Level 2 malocclusion is defined as patients, who, as a result of present dental problems, also have soft tissue discrepancies such as pursed upper lips, flared nostrils or inverted (turned down) lower lips. Level 3 malocclusion is considered the most severe as not only the teeth and surrounding soft tissues are affected, but also the bones as well”, says Dato’ Dr How.

How do the different classes and levels of malocclusion affect function?

The different stages of malocclusion result in a range of issues. If patients have dental crowding alone, this may cause oral hygiene problems due to difficulties in brushing and flossing, contributing to an increased risk of gum disease.

Class II/Level 2 malocclusion, or an overbite, can result in difficulties fully opening or closing the mouth, discomfort during eating, and breathing and speech challenges. Class III/Level 3 malocclusion, such as an underbite, can also cause speech, biting and chewing difficulties, and an increased likelihood of breaking or chipping the front teeth.

Dato’ Dr How reveals that patients with class/level II/2 and III/3 malocclusion, also experience a painful condition, known as temporomandibular joint (TMJ) syndrome.

“The TMJ is a hinge that connects the jaw to the skull. It combines swinging and sliding actions, like a door. If the upper and lower teeth do not properly occlude when the mouth is closed, patients have to force the lower jaw into the socket whenever they close to eat or speak,” he says.

“As a result of prolonged forcing, repeated impact can damage the joint’s protective cartilage that acts as cushion between the two bones. And once the cartilage is worn down or moves out of alignment, the skull and jaw bones can touch causing severe pain or result in joint dislocations.”

Dato’ Dr How Kim Chuan, Consultant Orthodontist at the Imperial Dental Specialist Centre


What is the importance of straightening teeth and who decides the need for orthodontic treatment?

Patients with severe dental crowding and jaw malocclusions are recommended orthodontic treatment because it not only improves their oral health and hygiene, but also addresses their various functional problems.

In Dato’ Dr How’s practice, the Index of Orthodontic Need (IOTN) is used to evaluate who requires orthodontic treatment and who doesn’t. The IOTN is a grading system which assesses the need for orthodontics based on individual dental health and aesthetic concerns.

If patients have severe malocclusions or dental crowding caused by defects from a cleft lip/palate, several unerupted and/or missing teeth, supernumerary teeth (excessive number of teeth), or increased dental, soft tissue or bone discrepancies resulting in functional setbacks, they will be classified as Grade 4 and 5, which signal a definite/true need for orthodontic treatment.

Patients with visible malocclusion, but with fewer functional problems, on the other hand, are classified as Grade 3, as they have a borderline need for treatment, while patients classified as Grades 2 and 1 have either a slight need or no need for treatment as their concerns are mainly aesthetic.

“If a patient’s condition is graded 4 or 5, your doctor will almost always recommend orthodontic treatment as present malocclusion either affects your oral hygiene or quality of life. Patients classified as Grade 3 can decide for themselves if they want orthodontic treatment, while those classified as Grades 1 or 2 may undergo treatment, as long as the choice for treatment is initiated by the patient,” Dato Dr How explains.

*This is part 1 of a 2-part article. Part 2 will explore the types of orthodontic treatments available, including their pros and cons, and how to care for them at home.


All photos courtesy of Dato’ Dr How Kim Chuan


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