Malocclusions in Dogs – When Teeth Don’t Align

Dogs normally have twenty-eight deciduous (primary or baby) teeth, which erupt during the first six months of life, and forty-two adult teeth. Dogs have four types of teeth:

1. Incisors are the smaller teeth located between the canines on the upper and lower jaws. They are used for grasping food and they help keep the tongue within the mouth.
2. Canine teeth are located on the sides of the incisors and are used to grasp food and other objects. 
3. Premolars are located behind the canines and are used to shear or cut food.
4. Molars are the most caudal teeth in the mouth. They are used for grinding food for entry into the esophagus.

 What does occlusion mean?

 Occlusion is a term used to describe the way teeth align with each other. “Normal” occlusion occurs when the upper (maxillary) incisors just overlap the lower (mandibular) incisors (scissor bite), when the lower canines are located equidistant between the third incisor and the maxillary canine teeth, and when the premolar crown tips of the lower jaw point between the spaces of the upper jaw teeth.

Flat-faced breeds (Boxers, Shih-Tzu, Boston Terrier, Lhasa Apso, Persians) have “abnormal” bites that are recognized as being “normal” for their breed, where the lower jaw protrudes in front of the upper jaw and alters the above tooth-to-tooth relationships.

What is malocclusion? 

Malocclusion refers to abnormal tooth alignment. There are two tupes of malocclusion: skeletal and dental. A skeletal malocclusion results when an abnormal jaw alignment causes the teeth to be out of normal orientation.  A dental malocclusion, or malposition, occurs when one or more teeth are out of normal alignment but the jaws are normally aligned.

When a dental or skeletal malocclusion causes trauma to other teeth or oral soft tissues, the condition is termed non-functional and treatment is needed. Therapy options include:

• extraction,
• moving the offending or offended tooth/teeth, or
• surgically creating additional space for the malpositioned tooth to occupy.

What are some common forms of skeletal malocclusion? 

• Mandibular distoclusion – also known as an overbite, overjet, overshot, class 2, and mandibular brachygnathism. It occurs when the lower jaw is shorter than the upper and there is a space left between the upper and lower incisors  when the mouth is closed. The upper premolars will be displaced rostrally (toward the nose) compared to the lower premolars.
   
• Mandibular mesioclusion – also known as an underbite, undershot, reverse scissor bite, prognathism, and class 3. It occurs when the lower teeth protrude in front of the upper teeth. If the upper and lower incisor teeth meet each other edge to edge, the occlusion is an even or level bite.
   
• Maxillary mandibular asymmetry – also known as a wry bite. It occurs when one side of the jaw does not grow as equally as the other side. 

What are some common forms of dental malocclusion? 

Rostral cross bite – occurs when the canine and premolar teeth on both sides  of the mouth are normally aligned, but one or more of the lower incisors are  positioned in front of the upper incisors.

Mesioverted mandibular canines – also known as lingually displaced canines or base narrow canines. It occurs when the lower canine teeth protrude inward, impinging or penetrating the maxillary gum line.  Often this condition is due to retained deciduous teeth and can usually be corrected through tooth movement, crown reduction and restoration, or extraction.

Rostroverted maxillary canine – may be inherited (Sheltie) or developmental, secondary to retained deciduous teeth.