Why Dogs of Some Breeds Have Pronounced Underbites Explained

An underbite in dogs describes a jaw misalignment where the lower jaw and teeth protrude beyond the upper teeth. This unique facial trait often gives affected dogs a characteristic look that some owners adore, although it is technically a conformation flaw. While the typical dog bite sees the back and bottom teeth meeting evenly in a scissor bite, an underbite causes the lower teeth to jut out in front of the upper set.

This condition is most common in brachycephalic breeds — dogs with short muzzles and compressed facial features. Popular breeds known to commonly have an underbite include the English Bulldog puppies, Pug puppies, and Shih Tzu puppies, among others. This is mainly due to genetic factors and selective breeding for shorter skulls causing a mismatch in jaw length, medically known as Class-3 malocclusion or canine underbite. However, an underbite may also result from trauma, or irregular dental development such as retained baby teeth affecting the adult set’s position.

Understanding the Causes of Underbite in Dogs

Underbites arise from several causes:

• Genetics: The dominant cause is heredity, especially in brachycephalic dogs where selective breeding has shortened the upper jaw more than the lower one.
• Developmental Factors: Puppies might experience delayed or abnormal eruption of adult teeth, where retained baby teeth push adult teeth into misalignment causing an underbite.
• Trauma: Injury to the jaw in the growing stages may result in the jaw bones developing improperly, leading to underbite formation.
• Chewing Habits: Unusual or excessive chewing on hard objects can sometimes cause teeth to shift and create an underbite later in life.

Which Dog Breeds Are Most Affected?

Breeds particularly prone to underbites include:

• English Bulldogs
• Pugs
• Shih Tzus
• French Bulldogs
• Boxers
• Cavaliers
• Various terrier breeds

Dogs that carry genes from these breeds may also exhibit underbites. Responsible breeding practices now aim to minimise extreme underbite cases by selecting for healthier skull and jaw anatomies.

Potential Problems Caused by Underbites

Although many dogs with underbites lead normal, comfortable lives, severe cases can cause:

• Dental Issues: Unequal wear on teeth, increased risk of periodontal disease due to crowded or crooked teeth, and difficulty in cleaning.
• Jaw Discomfort: Uneven pressure on jawbones and joints which may cause pain or difficulty while chewing.
• Eating Difficulties: Trouble closing the mouth properly and inefficient chewing, which can affect nutrition.
• Associated Health Concerns: Many brachycephalic breeds with underbites also suffer from respiratory problems like Brachycephalic Obstructive Airway Syndrome (BOAS), impacting breathing and exercise tolerance.

What Can Be Done About an Underbite? Treatment & Care

Minor underbites typically require no treatment if the dog has no pain or eating problems. Regular veterinary dental check-ups and proper oral hygiene are essential to avoid secondary issues.

In cases of painful malocclusion, a vet may recommend:

• Dental extractions of retained or crowded teeth.
• Corrective procedures to manage tooth alignment.
• Supportive care for jaw discomfort or secondary infections.

Furthermore, from 2025 the UK Kennel Club and Crufts have introduced stricter health-entry requirements for brachycephalic breeds. These measures encourage ethical breeding to reduce the incidence of extreme underbites and related health problems, promoting better welfare for affected dogs.

How to Recognise an Underbite Early in Puppies

Quick Answer: Early signs of an underbite include visible protrusion of the lower jaw or lower teeth jutting beyond the upper row, often noticeable once adult teeth start to grow in, usually around 4 to 6 months of age.

Underbites frequently become apparent during a puppy's teething stage when the adult teeth replace baby teeth. Responsible owners should observe their puppy’s mouth development closely and consult a vet if they notice unusual jaw alignment or retained puppy teeth. Early intervention may prevent worsening dental problems and improve long-term comfort for the dog.

Is an Underbite a Health Concern?

Quick Answer: While minor underbites are usually not harmful, severe underbites can lead to dental issues, jaw pain, and difficulty eating, requiring veterinary evaluation and care.

Dogs with pronounced underbites sometimes face an increased risk of dental wear and periodontal disease due to misalignment and crowding. Additionally, uneven forces on jaw joints may cause discomfort or arthritis. If your dog has difficulty chewing or shows signs of oral pain, it's important to have a veterinary dental assessment. Proper management mitigates health risks and improves wellbeing.

Responsible Pet Ownership and Breeding Practices

Selective breeding should prioritise health over extreme appearance traits like underbites. Prospective dog owners looking for breeds prone to underbites should seek reputable English Bulldog breeders or breeders of other affected breeds who adhere to ethical breeding standards that promote healthier jaw alignment and overall health.

Ensuring puppies are raised with adequate veterinary dental care and monitoring helps in early detection and appropriate care for underbites. Owners should also provide their dogs with chew toys that are safe and appropriate to promote healthy jaw development.

Conclusion

A pronounced underbite in certain dog breeds mainly results from genetic factors linked to brachycephalic facial conformation. While often a benign and cosmetic trait, severe underbites can cause dental, jaw, and eating difficulties. Responsible ownership involves monitoring puppy development, providing proper veterinary care, and supporting ethical breeding practices to enhance the health and welfare of affected dogs.