Canis ISSN: 2398-2942

Teeth: orthodontic and bite problem

Contributor(s): Alex Smithson, MarkThompson

Introduction

  •  Gnathi = jaw; often used to refer to the mandible: prognathic refers to a longer lower jaw relative to the upper jaw Mandibular prognathism 01 Welsh Terrier - left side of mouth Mandibular prognathism 02 10 month old Welsh Terrier - right side of mouth Mild mandibular prognathism undershot Teeth class 3 malocclusion. 'Relative maxillary prognathism' may be described.
  •  Cephali c= skull: brachycephalic refers to a shortening of the skull relative to the lower jaw Skull brachycephalic Teeth class 2 malocclusion jaw disproportion Teeth class 2 malocclusion.
  • Normal occlusal pattern is termed orthognathism.
  • Deviation from normal is termed malocclusion Dental malocclusion.
  • Cause: congenital Dental disease: congenital or developmental.
  • Many problems may be inherited. Malocclusions may be skeletal or dental or a combination of both. It may be difficult to differentiate the specific contribution of each however skeletal malocclusion is considered heritable while dental malocclusion may be developmental.
    Animals exhibiting skeletal malocclusion should not be used for breeding purposes.
  • Signs: may be purely cosmetic or may lead to other problems associated with overcrowding/overlap of teeth and occlusal trauma. This may affect deciduous and/or permanent teeth. Commonly an untreated malocclusion evident in the deciduous dentition will be followed by malocclusion of the permanents. Assess all teeth and soft tissues to identify abnormality and potential trauma. Perform this with a conscious animal, mouth closed or (briefly!) without an ET tube in the anesthetized animal. Any obstruction to full mouth closure (eg a tongue or ET tube) will render the assessment inaccurate.
  • Treatment: depends on defect and secondary problems. Many preferable alternatives exist to extraction, however referral to a suitably qualified colleague is required for appropriate assessment and advanced procedures. Examples include surgical intervention, tooth shortening and tooth movement. Simply cutting teeth down or applying bands is contra-indicated.
  • Summary: the key to occlusion or to the type of bite is seen in the relationship of the maxilla to the mandible in the premolar teeth, although four separate sites should be examined for a bite appraisal:
    • The incisors should exhibit scissor bite.
    • The canines should interdigitate: the mandibular canine should fit centrally within the diastema between the upper corner incisor (I3) and the maxillary canine. There should be no tooth-tooth contact and no soft tissue trauma. The crown of the mandibular canines should be angled in a mesio-labial ('rostro-lateral') direction.
    • The upper PM1 lines up in a slot between the lower PM1 and PM2, providing a 'pinking shear' effect continued between all premolars of the maxilla and mandible. The presence of this indicates harmony between the relative maxillary and mandibular lengths. It is rarely seen in many breeds!.
    • The skull should be symmetrical in the sagittal plane.
      Ethical considerations: to safeguard the ethical position and to prevent treatments being performed that are not in the best interests of the breed, owners should be asked to sign an orthodontic release form.

Normal dental architecture

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Malocclusion

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Further Reading

Publications

Refereed papers


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