Normal Occlusion and Malocclusions

Question 1

In a “normal” occlusion, describe how the incisors should be oriented/arranged.

Answer 1

maxillary teeth rostral to corresponding mandibular teeth
crown cusps of mandibular incisors contact cingulum of maxillary incisors

Question 2

In a “normal” occlusion, describe how the maxillary and mandibular premolars and molars should be oriented/arranged.

Answer 2

perfect interdigitation of upper and lower premolars and molars

maxillary and mandibular premolars do NOT contact each other, but the crown cusps of the mandibular premolars bisect the interdental spaces ROSTRAL to the corresponding premolar tooth.

crown cusps of mandibular premolars are LINGUAL to maxillary premolars.

the mesial crown cusp of maxillary fourth premolar (108 and 208) are positioned lateral to the space between the mandibular 4th premolar and mandibular 1st molar

Question 2

In a “normal” occlusion, describe how the canines should be oriented/arranged.

Answer 2

mandibular canine inclined labially and bisects interdental space between opposing maxillary 3rd incisor and canine.

Question 3

__________ is any deviation from normal occlusion. This can be due to abnormal positioning or due to symmetry or other deviations in bones that support dentition.

Answer 3

malocclusion

Question 4

Why are malocclusions a problem?
4 reasons

Answer 4

1. can cause trauma to the bone or tooth on tooth trauma and subsequent attrition
2. discomfort and pain
3. periodontal disease and tooth loss
4. compromised function

Question 5

What are the 4 treatment options for malocclusions?

Answer 5

1. nothing!
2. surgical extraction
3. crown reduction
4. orthodontic therapy (braces)

Question 6

A dog presents to your clinic with retained deciduous canines. This is causing the dog to have rostrally-tipped maxillary canines. What type of malocclusion is this?

Answer 6

Class 1 malocclusion

Rostrally-tipped maxillary canines are also called “lance canine” or “spear tooth”. These are common in shelties and are GENETIC!

Question 7

Which malocclusion type is characterized by: a normal maxilla and mandible length and occlusion, but 1+ misplaced or rotated teeth

Answer 7

Class 1 malocclusion

Examples are: dental crowding, rotated teeth, base narrow mandibular canines (linguoversion), rostrally-tipped maxillary canines (mesioversion), and anterior or posterior crossbite

Question 8

A dog presents to your clinic and on exam, you notice that its mandibular canines are linguoverted. What specific is this malocclusion?

Answer 8

Class 1 malocclusion – base narrow mandibular canines

Question 9

A cat presents to your clinic and you notice that the canines and premolars occlude normally, but a few of the lower incisors are in front of the upper incisors.
This is known as an anterior crossbite (malocclusion class 1).

These can be inherited, but what are these generally secondary to?

Answer 9

retained deciduous teeth

Question 10

What breed(s) commonly have crowded or rotated teeth (class 1 mal)?

Answer 10

toy and brachycephalic

Question 11

what can be a consequence of base narrow mandibular canines?

Answer 11

trauma to the palate

Question 12

Is base-narrow mandibular canines genetic?

Answer 12

yes

Question 13

What is the purpose of ball therapy?

Answer 13

Give a passive force orthodontic device (simple, smooth, rubber ball) to the animal and have them try to hold it in their mouth as much as possible. The most ideal time to do this is around 5 months when adult teeth are just breaking through.

This treatment helps fix the class 1 malocclusion base-narrow mandibular canines.

Question 14

What is the purpose of crown reduction and vital pulp therapy in a dog with base narrow mandibular canines?

Answer 14

cut the crown of the mandibular canines down in order to remove the trauma on the palate.

This is usually done because extraction of healthy canines is a difficult thing to do and comes with risks.

Question 15

What is inclined plane therapy?

Answer 15

placing a peice of specifically created plastic onto the maxillary canines tp redirect the mandibular canine in its normal position (in the interdental space between the maxillary canine and the maxillary 3rd incisor).

Question 16

What are other names for rostrally tipped maxillary canines?

Answer 16

mesioversion
lance canine
spear tooth

Question 17

Mesioversion (aka rostrally tipped maxillary canines) is genetic. What breed is this common in?

Answer 17

shelties.

Question 18

what is the treatment for anterior crossbite?

Answer 18

extraction of malpositioned teeth or orthodontic devices.

Question 19

___________ is when one or more posterior mandibular premolars is located buccal to its maxillary counterpart.

Answer 19

posterior crossbite (malocclusion class 1)

Question 20

What is a class II malocclusion or mandibular distoclusion?

Answer 20

overbite – due to SHORT mandible.
Mandibular premolars and molars will be caudal to the normal position.

Question 21

What is a class III malocclusion or mandibular mesioclussion?

Answer 21

underbite – due to LONGER mandible
mandibular premolars and molars are rostral to the normal position

commonly seen in shih tzus, boston terriers, pugs, boxers as a breed standard. Although its the breed standard, this does not mean it is healthy or comfortable.

Question 22

What is a class IV malocclusion or wry bite?

Answer 22

an asymmetric skeletal malocclusion – caused by the difference in length of the 2 maxillae and mandibles.

Question 23

What is the treatment for Class IV malocclusions?

Answer 23

early intervention to avoid “locked teeth”
extraction and/or crown reduction