Orthodontic Treatment

Prevention and Treatment of Malocclusion

Prevention is always better than treatment. Early recognition of a problem is essential to avoid discomfort and pain to the animal and prevent the development of severe pathology. Malocclusion affecting the primary dentition may require interceptive orthodontics (usually extraction of the deciduous teeth). Malocclusion affecting the permanent dentition may need no treatment at all, if it is not causing the animal discomfort or any oral pathology. Malocclusion causing discomfort and pathology always needs treating.

Primary teeth involved in malocclusion should be extracted as early as possible, i.e. at 6–8 weeks of age. This will allow the maxilla and mandible to develop to their full genetic potential independently before the permanent dental interlock forms. The roots of primary teeth are longer and narrower than the roots of the permanent teeth. Extraction requires care and patience to avoid tooth fracture. It is essential not to fracture the root, as a remnant may continue to deviate the eruption pathway of the permanent tooth. Every attempt should be made to minimize the risk of iatrogenic damage to the developing permanent teeth.

The treatment options available for permanent teeth causing a traumatic malocclusion are orthodontics, tooth shortening or extraction. In many instances, tooth shortening or extraction are preferable to orthodontics on ethical grounds. Tooth shortening often requires pulpal exposure. In this situation, endodontic therapy of the shortened tooth is mandatory. Lingually displaced mandibular canines in young dogs can often be corrected by stimulating the dogs to play, as often as possible, with specific rubber toys of an appropriate size and shape.

Orthodontic movement of teeth can be described as prolonged application of pressure to the tooth, resulting in movement of the tooth as the bone around it remodels. Bone on the compression side undergoes lysis allowing the tooth to move and bone formation on the tension side ensures that the tooth stays in the new position. In the ideal situation bone lysis and bone formation should be in equilibrium. In most practical situations, there is an imbalance and lysis occurs more rapidly. A retention phase maintaining the tooth in the new position while allowing time for bone formation is, therefore, necessary in many cases. The optimal orthodontic force is one that moves teeth rapidly without resulting in structural damage, while causing the least amount of discomfort or pain. Factors that need to be considered for any orthodontic appliance are the magnitude of the force, the distribution of the force and the duration of the force. The ideal force is a light continuous force. Heavy continuous forces are most damaging and should be avoided. Apart from the orthodontic forces applied, normal growth processes and forces from the lips, cheeks and tongue resting on the teeth will determine the outcome of the treatment.

Indications

In humans, medical (predisposition to periodontal diseases), functional (alteration of mastication or speech) and psychological (alteration of esthetics) problems relating to malocclusion are the primary reason for orthodontic treatment. In human orthodontics, whether malocclusion is hereditary or acquired is not a consideration when planning treatment. This is in contrast to veterinary orthodontics where esthetics and ethical concerns are linked, and treatment for the sole purpose of showing dogs or cats cannot be encouraged. The aim of any treatment is primarily to make the animal comfortable; esthetics are a secondary consideration. It is essential to determine if the presenting malocclusion is hereditary or not. Orthodontic correction of a malocclusion is contraindicated where the malocclusion is hereditary unless the animal is also neutered. The rationale for this is to avoid spread of inherited malocclusion within a breed.

Contraindications

• Ethical considerations
• Show animals
• Lack of owner compliance
• Lack of patient tolerance and compliance

Complications

Possible complications of orthodontic movement of teeth include pulpal disease, external root resorption, tooth mobility and pain. In short, the outcome of an orthodontic procedure is rarely predictable and needs frequent monitoring based on clinical signs and radiography.

The most common orthodontic procedures in veterinary medicine include moving the mandibular canines when they are causing trauma to the palatal muocsa using an inclined plane (pics 36-38), or in the case of lance canines (pic39).