Another way to classify malocclusions is as traumatic or nontraumatic. In other words, if the malocclusion causes problems for the dog, it is classified as traumatic. The problems associated
with malocclusions include trauma to oral soft tissues or teeth, inability to close the mouth, and difficulty eating. Some
of these problems may become serious, such as oronasal fistula formation. A severely undershot (class III) malocclusion may
or may not be traumatic. A condition such as linguoversion (base narrow) of the mandibular canine teeth, in which the teeth
are displaced to the lingual side of the proper occlusal position and can puncture the hard palate, is traumatic.
ETHICAL CONCERNS ABOUT ORTHODONTIC CORRECTION
Correcting malocclusions can entail ethical considerations related to breeding and participation in dog shows. Almost all
malocclusions have a genetic basis, and the owners of dogs with malocclusions must be counseled regarding the implications
of breeding these animals. And as mentioned above, the American Kennel Club prohibits dogs that have received orthodontic
treatment from competing in its dog shows.2
BASIC ORTHODONTIC PRINCIPLES AND ERRORS
Orthodontic movement is achieved by creating a force on the targeted tooth or teeth. The direction and magnitude of the force
is controlled and can be either sustained or intermittent. Over time, this force helps move the teeth through the jawbone
and into the desired location. This movement, which is influenced by the compressive or tensile forces transferred through
the periodontal ligament, is accomplished by the actions of osteoclasts and osteoblasts.
The course of orthodontic treatments in dogs is much shorter than in people, generally one to three months. In general, most
dogs tolerate properly installed and managed orthodontic appliances well. Only veterinarians who are trained in the principles
and practice of orthodontics should perform orthodontic treatments.
Many problems can arise during the course of an orthodontic treatment. These problems often result from technical errors,
such as too much force or improper direction of force applied to the tooth or inadequate anchorage of teeth with subsequent
movement of teeth that were not intended to be moved. Other problems can arise as a result of management errors, such as failure
to keep the orthodontic appliance in the dog's mouth or failure to maintain good oral hygiene.
COMMON PROBLEMS REQUIRING ORTHODONTIC TREATMENTS
Following is a discussion of common orthodontic problems in dogs and their typical treatment. Other types of malocclusion
may also warrant treatment, and other forms of management are available.
Persistent deciduous teeth
As a rule of thumb, an erupted permanent tooth and its deciduous predecessor should never exist together. When persistent
(retained) deciduous teeth is diagnosed, the persistent deciduous teeth should be extracted immediately. Persistent deciduous
teeth can prevent permanent teeth from occupying a correct position in the mouth (Figures 2A & 2B), which can lead to potentially traumatic malocclusions. Food and bacterial deposits can also accumulate between the retained
deciduous tooth and its permanent counterpart and cause periodontitis. When extracting persistent deciduous teeth, be careful
to avoid root tip fracture and other complications.
Figure 2A. A persistent deciduous mandibular canine tooth (arrow) is occupying the space where the permanent mandibular canine
tooth should be. A persistent deciduous maxillary canine tooth is occupying the space where the permanent maxillary canine
tooth should be, resulting in crowding and leaving little space for the mandibular canine tooth. 2B. Lingually displaced mandibular
canine teeth (arrows) will often migrate into their normal positions if persistent deciduous canine teeth are extracted in
a timely fashion.