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Basics ⬇

Basics

Definition

  • Malocclusion: any deviation from normal occlusion due to abnormal positioning of a tooth (dental malocclusion) or due to asymmetry or deviation of bones that support the dentition (skeletal malocclusion).
  • Ideal occlusion:
    • Maxillary incisors positioned rostral to the mandibular incisors.
    • Mandibular canine is inclined labially and bisects the space between the opposing maxillary third incisor and canine.
    • Maxillary premolars do not contact the mandibular premolars: mandibular premolar crowns are positioned lingual to the maxillary premolars; mandibular premolar crown cusps bisect the interdental spaces rostral to the corresponding maxillary premolar.
    • Maxillary fourth premolar mesial cusp is lateral to the space between the mandibular fourth premolar and first molar.

Terms of Malocclusion (American Veterinary Dental College Nomenclature)

  • Neutroclusion (Class 1): a normal rostral-caudal relationship of the maxillary and mandibular dental arches with malposition of one or more individual teeth (dental malocclusion); rostral (anterior) crossbite; mesioversion (“lance tooth”) linguoversion (“base-narrow mandibular canine) and caudal (posterior).
  • Mandibular distoclusion (Class 2): an abnormal rostral-caudal relationship in which the mandibular arch occludes caudal to its normal position relative to the maxillary arch (skeletal malocclusion).
  • Mandibular mesioclusion (Class 3): an abnormal rostral-caudal relationship in which the mandibular arch occludes rostral to its normal position relative to the maxillary (skeletal malocclusion).
  • Asymmetrical skeletal malocclusion: maxillary-mandibular asymmetry that can occur in a rostro-caudal direction (unilateral abnormal relationship), in a side-to-side direction (loss of midline alignment), or in a dorso-ventral direction with abnormal vertical space between opposing dental arches (open bite).
  • “Wry bite”: a nonspecific term used to describe a variety of unilateral occlusal abnormalities.

Signalment

Species

Dogs and cats

Breed Predilections

Breed predilection for certain malocclusions

Mean Age and Range

Malocclusion usually apparent after eruption of teeth (permanent or deciduous).

Signs

  • Vary greatly according to type, extent, and consequent injuries caused by the malocclusion.
  • May be associated with open or closed bites or overcrowding of the teeth.
  • Periodontal disease-from crowding or misalignment of teeth.
  • Soft tissue defects-from traumatic tooth contact; may be seen in the floor of the mouth and palate; palatal trauma may eventually result in oronasal fistula formation.
  • Fractures or attrition (wear) of teeth-may result from improper tooth contact.

Class 1 Malocclusions

  • Rostral (anterior) crossbite-palatally displaced maxillary incisors or labially displaced mandibular incisors; level bite – maxillary and mandibular cusps contact directly.
  • Base-narrow canines-tips of mandibular canines touch palate lingual to normal contact point, just labial to the diastema between corner incisor and maxillary canine (linguoversion).
  • Lance teeth-mesioversion of maxillary canine(s); the diastema between the corner incisor and this canine is often diminished and may force the mandibular canine into an abnormal position. dolichocephalic breeds (e.g., shelties and collies).
  • Caudal (posterior) crossbite-most are due to reversal of the relationship (labial/lingual) between the upper and lower carnassial teeth; more common in dolichocephalic breeds (e.g., collies, shelties, some sight hounds).

Causes

  • Congenital or hereditary factors-skeletal malocclusions (Classes 2, 3, and 4) and breed predilection.
  • Impediment to tooth eruption-operculum; retention of soft tissue covering.
  • Delayed eruption of deciduous or permanent teeth.
  • Retention (persistent) or delayed loss of deciduous teeth; permanent mandibular canines will erupt lingual to persistent deciduous teeth.
  • Traumatic injury affecting the jaws or teeth.

Risk Factors

Hereditary predispositions

Diagnosis ⬆ ⬇

Diagnosis

Differential Diagnosis

  • Tooth displacement-due to trauma, oral masses, or other causes.
  • Mechanical block-due to jaw fractures, luxated or subluxated teeth, or foreign bodies causing open bite.
  • Examine breed standards to determine what might be acceptable for the breed.

CBC/Biochemistry/Urinalysis

Generally normal

Imaging

  • Oral photography-pre-, peri-, and post-therapy.
  • Intraoral radiography-to evaluate roots and abnormalities, jaw anatomy, root maturity

Diagnostic Procedures

  • Complete oral examination to assess other oral abnormalities, including persistent deciduous teeth.
  • Impressions and models-for evaluation and appliance manufacture.

Treatment ⬆ ⬇

Treatment

Appropriate Health Care

  • The accurate assessment of abnormalities of occlusion will help determine if treatment is warranted and what treatment is appropriate.
  • Extraction of offending teeth can many times be an effective alternative to more classic orthodontic treatments.
  • Not every malocclusion needs orthodontic correction. If the bite is functional and non-traumatic to the animal, treatment may not be necessary. Additionally, extraction (or crown reduction with pulp capping) of offending teeth often can be an effective alternative to more classic orthodontic treatments. Orthodontic treatment is usually based on prevention of improper contact trauma, wear, or injury to hard or soft tissues, and should only be performed by a trained individual.

Diet

Soft diet with appliances

Client Education

Home Care with Appliance

  • Examine the appliance twice daily.
  • Flush the mouth with an oral hygiene solution or gel.
  • Prevent chewing of items and provide a soft diet until the appliance is removed.

Surgical Considerations

Permanent Tooth Class 1 Malocclusion

  • Treatment primarily involves tipping movements of the teeth, although extrusion may be required to provide proper retention.
  • Rostral crossbite-arch crowding: may require odontoplasty to thin teeth (to allow room for movement.
    • Movement can be accomplished but is likely complicated and should be handled by a specialist.
  • Base-narrow canine teeth-treatment is aimed at prevention of contact trauma, pain and discomfort, and oronasal fistula formation.
    • The diastema (space between the maxillary third incisor and canine) must be sufficient for the mandibular canine to fit; once occluding correctly in the diastema, the closed bite serves as a natural retainer.
    • If the mandibular canines have just started to erupt into a lingual position, manual manipulation or “ball therapy” may influence a more buccal eruption sequence; the deciduous teeth and roots must be completely absent.
    • A hard rubber ball (hand ball, etc.) can be placed in the mouth and of a size that will help “slide” the canines laterally; apply the ball with gentle mouth closing pressure two to three times daily, a few minutes at a time, and encourage play with the ball.
    • If the tip of the mandibular canine barely touches the edge of the maxillary mucosa, gingivoplasty or gingivectomy in the diastema may release the contact.
    • Moderate cases may be easily managed by building a false crown extension with composite material that will splay the false tip lateral to the gingival margin, with eventual correction of the positioning.
    • More severe cases (extreme linguoversion, inadequate diastema or rostral or distal deviation of the mandibular canine) may require an orthodontic appliance (incline plane):
    • Movement can be accomplished but is likely complicated and should be handled by a specialist.
    • Mandibular canine extraction or crown reduction with vital pulpotomy can provide the patient with a comfortable bite.
  • Maxillary canine mesioversion (Lance tooth):
    • Movement can be accomplished but is likely complicated and should be handled by a specialist.
  • Caudal (posterior) crossbite-in most cases, no treatment is necessary, as the bite is typically functional; in traumatic situations, extraction of one of the offending teeth; orthodontic correction is long and tedious and requires more advanced orthodontic appliances and blocking the bite open.

Permanent Tooth Class 2, 3, and Asymmetrical Malocclusion

  • Based on providing a functional, non-traumatic occlusion for the animal's medical health; treatment may not be necessary.
  • May require advanced orthodontic and surgical procedure and is generally best handled by a specialist.

Deciduous Tooth Class 1 Malocclusion

Careful and gentle extraction of the maloccluded deciduous tooth (interceptive orthodontics) to remove inappropriate physical impediment in hopes that the permanent tooth will erupt in the appropriate position; when performed at least 4 weeks prior to permanent tooth eruption, success rate >80% is not uncommon.

Deciduous Tooth Class 2, 3, and 4 Malocclusion

Careful and gentle extraction of the maloccluded deciduous tooth in hopes that the short jaws will be released from the bite interlock, allowing it to grow (if the genetic potential is present), prior to eruption of permanent teeth and reestablishment of bite interlock; performed at least 6 weeks prior to permanent tooth eruption, success rate <20% is common.

Follow-Up ⬆ ⬇

Follow-Up

Patient Monitoring

  • For the corrected occlusion to be stable, it needs to be self-retaining or it may tend to revert to malocclusion; examine at 2 weeks, 2 months, and 6 months after the treatment is complete to see if desired outcome is stable.
  • It is advisable at around 6 months post-therapy for radiographs to be taken and compared to the pretreatment films to determine if all teeth still appear vital (alive) and to evaluate any root changes that may have occurred due to the pressures of tooth and root movement during orthodontics.

Prevention/Avoidance

  • Careful selection of puppies, with oral and general examination, as well as examination and history of sire and dame, prior to purchase.
  • Selective breeding based on preferred breed characteristics.
  • Careful monitoring of deciduous and permanent tooth eruption for early detection and treatment, if required.

Possible Complications

  • Selective extraction of deciduous tooth-potential for injury to underlying permanent tooth buds either by direct injury with extraction instruments or subsequent traumatic inflammation affecting tooth growth and maturity; injuries may result in tooth buds dying, teeth becoming non-vital as they erupt, root dysplasia or dilaceration, crown hypoplasia, or hypomineralization.
  • Orthodontic movement of permanent teeth-several conditions may result, including root resorption, root ankylosis, or non-vitality of the tooth; these conditions are uncommon in properly managed orthodontic procedures.

Expected Course and Prognosis

  • Course of treatment may vary with the type of malocclusion and the animal's nature and habits (e.g., inappropriate chewing).
  • Generally, most cases take 1–7 months for movement and retention phase, depending on severity and if extrusion of tooth/teeth is required for stabilization of the bite. Prognosis is good to excellent in most treated patients.
  • Prognosis is fair to good in most untreated malocclusions.
  • Complications in untreated cases-periodontal disease; attrition or fractures of teeth; trauma to soft tissues; oronasal fistula formation; drying or desiccation of exposed tooth surfaces, resulting in beige to brown discoloration.
  • Some cases DO NOT need or require orthodontic intervention; only routine observation for early detection and treatment of any secondary complications (e.g., periodontal disease, worn or chipped teeth) is advised.

Miscellaneous ⬆

Miscellaneous

Associated Conditions

  • Lack of head symmetry
  • Oral soft tissue trauma
  • Chipped teeth
  • Desiccation of exposed tooth surfaces
  • Periodontal disease

Pregnancy/Fertility/Breeding

Although animals have the medical right to as functional and correct an occlusion as can be reasonably provided by therapy, animal club rules, professional association principles, and state and national laws may conflict with an animal's right to proper medical therapy. Some kennel club rules disqualify animals with modification to natural appearance (with certain exceptions), and owners should be made aware of this. If hereditary involvement is suspected, inform the owner. If treatment is being considered, the owner or agent should acknowledge his or her responsibility to inform anyone who has the right to know of such alterations. Additionally, the possibility of removing the animal from the genetic pool by appropriate methods should be discussed.

Internet Resources

http://www.avdc.org/Nomenclature.html.

Author Heidi B. Lobprise

Consulting Editor Heidi B. Lobprise

Acknowledgment The author and editors acknowledge the prior contribution of Robert Wiggs.

Client Education Handout Available Online

Suggested Reading

Lobprise HB. Blackwell's Five-Minute Veterinary Consult Clinical Companion-Small Animal Dentistry. Ames, IA: Blackwell, 2007 (for additional topics, including diagnostics and techniques).

Wiggs RB, Lobprise HB. Veterinary Dentistry: Principles and Practice. Philadelphia: Lippincott-Raven, 1997, pp. 457–463.