Understanding Cat Malocclusion (Overbite and Underbite)

1 Overview

What is feline malocclusion?

Malocclusion is one of the three most common oral diseases. Caused by genetics, disease, dysfunction, or teething problems, it leads to misalignment of teeth, jaws, and craniofacial structures — called malocclusion.

Simply put, feline malocclusion means the upper and lower teeth aren’t in normal position and don’t bite properly.

Malocclusion can cause oral injury, periodontal disease, repeated soft-tissue bites, excessive wear and fractures, tooth death, and sometimes even oronasal fistula.

Types of feline malocclusion

A cat has 26 deciduous and 30 permanent teeth. The transition starts with the front incisors at 3–4 months and ends with the rear molars at 4–6 months.

If abnormal, the upper and lower teeth mesh poorly and interfere. If some teeth grow oddly or the jaws are uneven in length, alignment is off and biting fails. This is ‘incorrect bite.’

Cats’ incorrect bites include the following.

1. Crossbite

A condition where the jaw bones are normal but some teeth are misaligned.

2. Overbite (deep overjet)

Upper jaw longer than lower. Simply called ‘overbite,’ close to human deep overbite/overjet.

3. Underbite (overjet too shallow)

Underbite means the lower teeth cover the upper — the upper front teeth sit behind the lower ones, the front teeth lose biting function, and the upper jaw and lip recede, commonly called an ‘underbite.’

4. Level (edge-to-edge) bite

The upper and lower incisors line up in a straight line.

5. Wry bite

Uneven growth left vs right, making the jaw look crooked.

Causes of feline malocclusion

The main causes are:

Generally, malocclusion is linked to skull growth!

Skull of overbite

Skull of underbite and wry bite

① Genetics:

Skull shape is closely tied to genetics, so part of malocclusion is inherited.

Especially in flat-faced breeds like Persians and Exotics, the very short muzzle makes upper/lower jaw imbalance more likely. These malocclusions come from selective breeding by humans.

② Injury or trauma:

If a kitten suffers injury around the temporomandibular joint, like fracture or dislocation, it can cause uneven blood supply and left-right tooth growth, resulting in a wry bite.

③ Poor nutrition in youth:

Malnutrition can hinder bone development and cause bite problems.

④ Retained deciduous teeth

During teething, if baby teeth fall out later than permanent teeth erupt, the permanent teeth struggle to emerge. The baby teeth linger and interfere with permanent tooth growth.

Treatment of feline malocclusion

1. Extraction:

Assess upper and lower jaw length and check by 6 weeks of age. If the lower jaw is too short relative to the upper, lower teeth can pierce the upper palate and cause pain, so extract them. Also, if a tooth tilts toward the tongue, extract it, since otherwise permanent teeth may grow in the same direction.

From 4 to 6 months after adult teeth come in, check for retained baby teeth. If any remain, they interfere with permanent teeth and should be removed promptly.

2. Orthodontics:

If malocclusion is found after permanent teeth grow in, orthodontics is possible — when there’s a biting tendency, or lower canines drop lingually and damage the palate, and misalignment causes severe pain. Most methods use the cat’s chewing force to push teeth back into place. As a highly specialized field, not all vet clinics do it.

3. Do not breed cats with malocclusion:

If a cat has malocclusion, the next generation likely will too, so the best approach is not to breed it.