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[[File:Dog teeth occlusion 2.jpg|right|200px|thumb|Occlusal assessment – mandibular incisors occlude on the palatal aspect of the maxillary incisors (known as a scissor bite), the mandibular canine interdigitates half way between the maxillary canine and third incisor, and the premolars interdigitate in a “picking shear” effect.<small>''© Lisa Milella 2013''</small>]]

[[File:Dog teeth occlusion 2.jpg|right|200px|thumb|Occlusal assessment – mandibular incisors occlude on the palatal aspect of the maxillary incisors (known as a scissor bite), the mandibular canine interdigitates half way between the maxillary canine and third incisor, and the premolars interdigitate in a “picking shear” effect.<small>''© Lisa Milella 2013''</small>]]

[[File:Dog incisor occlusion.jpg|right|200px|thumb|Occlusal assessment of the incisors of a dog.<small>''© Lisa Milella 2013''</small>]]

[[File:Dog incisor occlusion.jpg|right|200px|thumb|Occlusal assessment of the incisors of a dog.<small>''© Lisa Milella 2013''</small>]]

By definition, malocclusion is an abnormality in the position of the [[:Category:Teeth - Anatomy & Physiology|teeth]]. The clinical significance of malocclusion is that it may cause discomfort and sometimes pain to the affected animal. In some cases, it may be the direct cause of severe oral pathology.  

By definition, malocclusion is an abnormality in the position of the [[:Category:Teeth - Anatomy & Physiology|teeth]]. The clinical significance of malocclusion is that it may cause discomfort and sometimes pain in the affected animal. In some cases, it may be the direct cause of severe oral pathology.  

===Normal Occlusion===

===Normal Occlusion===

The '''ideal relationship''' with the [[Oral Cavity Overview - Anatomy & Physiology|mouth]] closed can be defined by the following:

The '''ideal relationship''' with the [[Oral Cavity Overview - Anatomy & Physiology|mouth]] closed can be defined by the following:

:Maxillary incisor teeth all positioned rostral to the corresponding mandibular incisor teeth.  

:*Maxillary incisor teeth all positioned rostral to the corresponding mandibular incisor teeth.  

:Mandibular canine tooth is inclined labially and bisects the interproximal space between the opposing maxillary third incisor tooth and canine tooth.

:*Mandibular canine tooth is inclined labially and bisects the interproximal space between the opposing maxillary third incisor tooth and canine tooth.

:Maxillary premolar teeth do not contact the mandibular premolar teeth.

:*Maxillary premolar teeth do not contact the mandibular premolar teeth.

:The mesial crown cusp of the maxillary fourth premolar tooth is positioned lateral to the space between the mandibular fourth premolar tooth and the mandibular first molar tooth.

:*The mesial crown cusp of the maxillary fourth premolar tooth is positioned lateral to the space between the mandibular fourth premolar tooth and the mandibular first molar tooth.

This is described as '''orthoclusion'''.

This is described as '''orthoclusion'''.

===Skeletal Malocclusion===

===Skeletal Malocclusion===

'''Mandibular prognathic bite''': In the mandibular prognathic bite <font color="red">(pic4 malocclusion)</font color>, often called ‘undershot’, the [[Skull and Facial Muscles - Anatomy & Physiology|mandible]] is longer than the [[maxilla]] and some or all of the mandibular teeth are rostral to their normal position. If the dental interlock prevents the mandible from growing rostrally to its full genetic potential, lateral or ventral bowing of the mandible may occur to accommodate the length. This results in an open bite and is characterized by increased space between the premolar cusp tips. In addition, the caudal angle of the mandible is caudal to the temporomandibular joint to accommodate the extra length of the mandible.

'''Mandibular Prognathic Bite''': In the mandibular prognathic bite <font color="red">(pic4 malocclusion)</font color>, often called ‘undershot’, the [[Skull and Facial Muscles - Anatomy & Physiology|mandible]] is longer than the [[maxilla]] and some or all of the mandibular teeth are rostral to their normal position. If the dental interlock prevents the mandible from growing rostrally to its full genetic potential, lateral or ventral bowing of the mandible may occur to accommodate the shortening in length. This results in an open bite and is characterized by increased space between the premolar cusp tips. In addition, the caudal angle of the mandible is caudal to the temporomandibular joint to accommodate the extra length of the mandible.

'''Mandibular brachygnathic bite''': A mandibular brachygnathic bite, often called ‘overshot’, occurs when the mandible is shorter than normal. This will often result in the mandibular canine [[Category:Teeth - Anatomy & Physiology|teeth]] contacting the [[Hard Palate|palate]], causing trauma. <font color="red">(pic 5malocclusion)</font color>

'''Mandibular Brachygnathic Bite''': A mandibular brachygnathic bite, often called ‘overshot’, and occurs when the mandible is shorter than normal. This often results in the mandibular canine [[Category:Teeth - Anatomy & Physiology|teeth]] contacting the [[Hard Palate|palate]], causing trauma. <font color="red">(pic 5malocclusion)</font color>

'''Wry bite''': A wry bite occurs if one side of the head grows more than the other side. In its mildest form a one-sided prognathic or brachygnathic bite develops. In more severe cases, a crooked head and bite develop with a deviated midline. An open bite may also develop in the incisor region so that the affected teeth are displaced vertically and do not occlude. <font color="red">(pic6 malocclusion)</font color>

'''Wry Bite''': A wry bite occurs if one side of the head grows more than the other side. In its mildest form a one-sided prognathic or brachygnathic bite develops. In more severe cases, a crooked head and bite develop with a deviated midline. An open bite may also develop in the incisor region so that the affected teeth are displaced vertically and do not occlude. <font color="red">(pic6 malocclusion)</font color>

'''Narrow mandible''': In some animals, the mandible is too narrow with respect to the upper jaw. The result is that the lower canines impinge on the maxillary [[Gingiva|gingivae]] or the [[Hard Palate|hard palate]] instead of fitting into the diastema between the upper third incisor and upper canine on either side. The animal may not be able to close its mouth and injury to the gingivae or palatal mucosa commonly occurs. In severe, untreated cases an oronasal communication may develop over time. This condition is seen in both the primary (deciduous) and permanent dentition. Persistent mandibular primary canines will further exacerbate the condition, as the permanent mandibular canines erupt medially to their primary counterparts. The incorrect dental interlock will interfere with the normal growth in width and length of the developing mandible. The condition can also be caused by persistent primary mandibular canines in a mandible of normal width. <font color="red">(pic 7 malocclusion)</font color>

'''Narrow Mandible''': In some animals, the mandible is too narrow with respect to the upper jaw. The result is that the lower canines impinge on the maxillary [[Gingiva|gingivae]] or the [[Hard Palate|hard palate]] instead of fitting into the diastema between the upper third incisor and upper canine on either side. The animal may not be able to close its mouth and injury to the gingivae or palatal mucosa commonly occurs. In severe, untreated cases an oronasal communication may develop over time. This condition is seen in both the primary (deciduous) and permanent dentition. Persistent mandibular primary canines will further exacerbate the condition, as the permanent mandibular canines erupt medially to their primary counterparts. The incorrect dental interlock will interfere with the normal growth in width and length of the developing mandible. The condition can also be caused by persistent primary mandibular canines in a mandible of normal width. <font color="red">(pic 7 malocclusion)</font color>

===Dental Malocclusion===

===Dental Malocclusion===

Dental malocclusion is malpositioning of [[:Category:Teeth - Anatomy & Physiology|teeth]] where there is no obvious skeletal abnormality, i.e. there is no jaw length or width discrepancy.

Dental malocclusion is malpositioning of [[:Category:Teeth - Anatomy & Physiology|teeth]] where there is no obvious skeletal abnormality, i.e. there is no jaw length or width discrepancy.

'''Anterior crossbite''': This is a clinical term used to describe a reverse scissor occlusion of one, several or all of the incisors. The condition can be secondary to persistent primary incisors. However, there is probably a skeletal origin as well, since affected animals often develop a mandibular prognathic bite. In other words, an anterior crossbite in an immature animal may be the first sign of a developing mandibular prognathism. The cause can either be a dental malocclusion (i.e. linguoversion of the upper incisors) or a skeletal malocclusion (i.e. mandibular prognathism or maxillary brachygnathism). <font color="red">Pic8 malocclusion</font color>

'''Anterior Crossbite''': This is a clinical term used to describe a reverse scissor occlusion of one, several or all of the incisors. The condition can be secondary to persistent primary incisors. However, there is probably a skeletal origin as well, since affected animals often develop a mandibular prognathic bite. In other words, an anterior crossbite in an immature animal may be the first sign of a developing mandibular prognathism. The cause can either be a dental malocclusion (i.e. linguoversion of the upper incisors) or a skeletal malocclusion (i.e. mandibular prognathism or maxillary brachygnathism). <font color="red">Pic8 malocclusion</font color>

'''Malocclusion of the canine teeth''': The two most common abnormalities in canine tooth position are:

'''Malocclusion of the Canine Teeth''': The two most common abnormalities in canine tooth position are:

* Rostral displacement (mesioversion) of the maxillary canines. Persistent primary canines may be responsible for this condition. A breed predisposition has been reported in the Shetland sheepdog. <font color="red">(pic9malocclusion)</font color>

* Rostral displacement (mesioversion) of the maxillary canines. Persistent primary canines may be responsible for this condition. A breed predisposition has been reported in the Shetland sheepdog. <font color="red">(pic9malocclusion)</font color>

* Medial displacement of the lower canines. <font color="red">(pic10mal)</font color>

* Medial displacement of the lower canines. <font color="red">(pic10mal)</font color>

'''Malocclusion of the premolars and molars''': Posterior crossbite is used to describe an abnormal relationship of the carnassial teeth, seen commonly in the dolicocephalic breeds, where the normal buccolingual relationship is reversed.

'''Malocclusion of the Premolars and Molars''': Posterior crossbite is used to describe an abnormal relationship of the carnassial teeth, seen commonly in the dolicocephalic breeds, where the normal buccolingual relationship is reversed.

==Classification of Malocclusion==

==Classification of Malocclusion==

===Class 1 Malocclusion===

===Class 1 Malocclusion===

Also called neutroclusion, this describes a normal rostral-caudal relationship of the maxillary and mandibular dental arches but there is '''malposition of one or more individual teeth'''.

Also called '''neutroclusion''', this describes a normal rostral-caudal relationship of the maxillary and mandibular dental arches but there is '''malposition of one or more individual teeth'''.

===Class 2 Malocclusion===

===Class 2 Malocclusion===