Veterinary orthodontics: Some cases require braces

The primary objective of veterinary orthodontics is to provide a comfortable bite for companion animals. Cosmetics are often improved, however orthodontic care is never provided for deceptive purposes. Our ethical priority is to provide genetic counseling to avoid future problems associated with malocclusions. Traumatic malocclusions are painful for pets and painfully expensive for owners.

Veterinary orthodontic services may be interceptive (directed at prevention) or involved in the application of forces to move teeth to establish a functional and more comfortable bite.

What characterizes a normal occlusion (bite)?

Seven characteristics are useful for the evaluation of the bite in companion animals:

• Head dimension or shape dictates whether the occlusion is functionally acceptable: mesaticephalic (medium length and width e.g. German Shepherd), brachiocephalic (short, wide head e.g. Boxer) or dolichocephalic (long, narrow head e.g. Whippet or Saluki).

• A "scissors bite" refers to the incisor occlusal relationship (Photo 1).

Photo 1: Scissors bite.

• The canine interlock suggests a proper fit of the upper and lower dental arcades (Photo 2).

Photo 2: Canine interlock.

• The premolar interdigitation refers to the "pinking shear" appearance from a side view (Photo 3).

• The carnassial teeth alignment allows for a functional bite.

• A consistent "freeway space" is a result of the relationship between the upper and lower arcades.

• Head symmetry helps determine relationships between dental arcades.

Photo 3: Premolar interdigitation.

There is variability between breeds in evaluating a "normal" or acceptable occlusion. This is the reason for consideration of the head dimension or shape. An acceptable bite for a Boxer is not acceptable for a German Shepherd.

A "scissors bite" refers to the proper occlusal relationship between the upper and lower incisors. All six upper incisors should be just rostral to and overlap the six lower incisors. The cusp tips of the lower incisors should rest on the cingulum of the upper incisors. The cingulum is a shelf-like surface of the distal (caudal) aspect of the incisor teeth. If you don't find a "scissors bite", you are very likely looking at a malocclusion. This malocclusion may be a traumatic occlusion where there is tooth-on-tooth or tooth-on-soft-tissue contact (Photo 4). These conditions can be tremendously painful even in patients who demonstrate no discomfort. It has been postulated that companion animals avoid demonstrating pain to avoid being culled from the pack. When you identify a traumatic malocclusion, the patient deserves prompt dental care.

Photo 4: Traumatic malocclusion; note persistent deciduous canine.

Canine interlock is important for normal development. The interlock physically directs and maintains the appropriate upper-to-lower jaw length relationships in the growing animal. Lack of this interlock suggests a discrepancy in jaw lengths and a malocclusion. In the normal occlusion, the lower canines will fit in the space between the upper canine and the corner (lateral or third) incisor and there will be no physical contact between these teeth as shown in Photo 3.

Premolar interdigitation and the alignment of the developmental grooves of the carnassial teeth are also useful in the evaluation of jaw-length relationships. The last characteristics of evaluation are the "freeway space" between the dental arches and the head symmetry. The patient is viewed from each side for symmetry and consistency of the freeway space. Consistency of the freeway space confirms the lack of bowing in either the upper or lower arcades. Viewing the patient from the front and the top can help evaluate head symmetry. The upper and lower incisors should line up at the midline. If they don't, you may be looking at a "wry bite". The zygomatic arches should be equidistant from the midline.

Malocclusion questions

What are malocclusions, and when should they be treated?

Photo 5: Traumatic malocclusion; note the short mandible.

Photo 6: Interceptive orthodontics; lower canines and incisors extracted.

Malocclusions are occlusions that can be characterized as abnormal or unacceptable for the breed. They should be treated immediately if there is a traumatic occlusion in the deciduous or permanent teeth. In very young patients, early interceptive treatment may be appropriate to maintain the normal canine dental interlock or to release any interlock that will prevent normal development (Photos 5, 6). Alternately, it may be desirable to wait until the patient is 8-10 months when active-force orthodontics is planned.

What are some common malocclusions?

• Lance canines are common in Shetland Sheepdogs and some cat breeds. The upper canines are positioned more rostral (or mesial) than normal. The result is a malocclusion where the mandibular canine cannot fit into the space between the upper canine and the adjacent corner incisor. The lower canine often will become malpositioned and strike the lip. The condition may be unilateral, however it is usually bilateral. The condition often causes crowding, resulting in plaque retention and the development of periodontal disease.

Photo 7: Lance canine; initial force directed ventrally.

Photo 8: Lance canine; force directed ventrally.

Photo 9: Lance canine; force directed distally (caudally).

The cause of lance canines is likely inherited since there are breeds that are over-represented with the condition. If the upper deciduous canines fail to exfoliate or exfoliate late, then the adult teeth can be deflected forward into the lance or spear-like position.

Active-force orthodontics is typically employed to move the lance canine distally (or caudally). For some patients, the initial force can be directed ventrally (Photos 7-8). Later, distal forces may be applied (Photo 9, view of opposite side). Oral surgery (extraction) or crown reduction with endodontic therapy are alternative treatments for some cases of lance canines.

• Base narrow canines (BNC) or lingually deviated lower canines are a common presentation. This condition may be unilateral or bilateral. The normal canine interlock is lost which may contribute to or result from jaw-length discrepancies. The lower canine teeth often strike the palatal soft tissue creating indentations, holes or oronasal fistulas. This traumatic occlusion can be quite uncomfortable. I have found patients with foreign material entrapped in the palatal defects (Photo 10). Chronic oronasal fistulas can cause chronic respiratory tract infections and poor overall health. These patients should be treated as soon as possible.

Photo 10: Traumatic palatal defect. Note imbedded debris.

The cause of BNC is often due to persistent (retained) or late exfoliation of the lower deciduous canine teeth. This problem may be an inherited condition. Any time you observe a deciduous and adult tooth of the same type at the same time, extract them immediately, even if they appear to be loose! Extraction of the entire tooth (very important) may be enough to prevent this malocclusion. It is imperative to watch the eruption path of the adult dentition to avoid patient discomfort.

Photo 11: Palatal incline plane; lower canines strike the sloped areas moving them in a more vestibular position.

BNC can be treated with a palatal incline plane (Photo 11), screw or spring mandibular active force appliances, gingival wedge resection or by surgical manipulation of malpositioned teeth. Mandibular canine crown reduction with endodontic therapy or surgical extraction are additional alternatives used to eliminate the traumatic occlusion. Patients treated by extraction or crown height reduction may experience tongue protrusion from the mouth. Clients should be advised of this potential complication.

Photo 12: Anterior cross bite.

Photo 13: Maxillary arch bar (side view).

Anterior crossbite is a malocclusion where one or more teeth are out of normal arch alignment. The condition may cause a traumatic occlusion or may only be a cosmetic problem. Late exfoliation of deciduous incisor teeth may result in this deviation from the normal "scissors" bite. I have most commonly observed the presentation of the upper central incisor teeth occluding caudal to the lower central incisors (Photo 12).

Photo 14: Maxillary arch bar (front view).

Photo 15: Maxillary arch bar (top view).

Correction of this condition typically involves the movement of the maxillary incisor teeth forward and ventrally using a maxillary arch bar (Photos 13-15) or another orthodontic appliance. The goal of treatment is to achieve a normal scissors bite (Photos 16-17).

Photo 16: Anterior crossbite corrected.

Photo 17: Anterior crossbite corrected (side view).

Posterior crossbite is a malocclusion where the carnassial teeth line up abnormally (Photo 18). The lower first molar tooth is positioned more vestibular (buccal) as compared to the upper fourth premolar tooth. The normal function of the carnassials may be lost in this condition. Posterior crossbite has not been treated orthodontically by this author. If posterior crossbite causes tooth-on-tooth or tooth-on-soft-tissue trauma, extraction of one or both carnassials may be indicated.

Some cases are appropriate for braces; others are not!

Photo 18: Posterior crossbite.

Treatment plans should be tailored to the individual patient's needs and client's desires. It is very important to choose orthodontic cases carefully. Excellent communication between the veterinarian and the client is essential. A clear understanding of the goals of treatment must be established. Familiarity with the animal's temperament and the client's ability to comply with directions are critical to avoiding complications. The client must be able to schedule and keep appointments.

Appropriate case selection, excellent communication and meticulous patient care lead to successful orthodontic treatment. Companion animals deserve comfortable mouths with a functional occlusion. Many cases are appropriate for braces and are professionally rewarding.

Dr. Kressin, a diplomate of the American Veterinary Dental College, operates a specialty dental and oral surgery service in Oshkosh, Wis., and Milwaukee. He is a fellow of the Academy of Veterinary Dentistry.

Dale J. Kressin