Bite (Occlusal) Evaluation In Cats And Dogs
Do you know the normal number of teeth in cats and dogs?
To evaluate the bite and to determine if it is right, you should know the correct number of teeth and their normal alignment. The number of teeth and correct alignment are discussed below.
Normal Bite in Dogs
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Normal scissors bite; upper incisors overlap lower incisors (front view).
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Normal scissors bite; lower canine fits between upper third incisor and the upper canine. Also notice the interdigitation of upper and lower premolar teeth (side view).
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Normal Bite in Cats
Cats are carnivores like dogs. Their normal occlusion is similar to dogs with significant differences. The upper and lower incisor teeth normally align similar to dogs, with the upper incisors slightly overlapping the lower incisors. In some breeds the incisors align tip to tip (or level). This is sometimes referred to as a "level bite". Notice in the photo below that the lower canines align similar to dogs with the lower canine between the upper canine and the upper third incisor. This is viewed from the front rather than from the side as in dogs.
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(new photo)
Cat with normal bite; upper incisors just overlap the lower incisors (also with periodontal disease).
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(new photo)
Same cat as above with normal premolar relationship.
The upper premolars interdigitate with the lower premolars as in dogs.
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The upper maxilla (jaw) is slightly wider than the lower mandible (jaw). This alignment allows the shearing of food. All of cat's teeth have pointed tooth crowns.
Abnormal occlusions are abnormal bites!
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Persistent lower canines or "mixed dentition" Never "wait" to remove the primary teeth!
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Persistant upper canine and incisor teeth in a "mixed dentition". Dr. Kressin removed these primary teeth and the supernumerary upper fourth premolar teeth!
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Harry Potter front view. Harry has a malocclusion. Both jaws are shorter than normal and the right mandible (lower jaw) is longer than the left mandible.
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Harry Potter left side view.
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Harry Potter right side view.
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Harry Potter front view of the bite. Left mandible (jaw) is shorter than the right. The left lower primary (baby) canine tooth "locks" with the left upper primary canine tooth. The left jaw has stopped growing forward and is shorter than normal. The right lower jaw is also shorter than normal but longer than the left side. This is called "wry" bite.
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Notice three of the four primary canine teeth have failed to exfoliate (fall out). This results in misalignment of the canine teeth.
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This view from the underside of Harry Potter demonstrates the "crooked" or "wry" alignment of the lower mandibles (jaws).
Dr. Kressin recommends the removal of the primary teeth when the secondary teeth are erupting to help avoid the interlock of teeth.
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After the primary teeth have been extracted, the jaw length discrepancy may normalize. If trauma persists from the malocclusion, crown reduction with vital pulpotomy and pulp capping, or are viable treatment options. We want to provide a comfortable bite.
Dogs have teeth, and it is useful to know the correct number and alignment of teeth!
Puppies have 28 teeth and adult dogs normally have 42 teeth (dental chart). It is very important to monitor the transition from the primary (baby) dentition to the secondary (adult) dentition. During this transition period, the dentition is called a "mixed dentition" (see photos above). Abnormal bites (malocclusions) can develop as a result of failure or slow exfoliation (loss) of the primary teeth, or failure or slow eruption of the secondary teeth. Abnormalities of this transition from the primary to the secondary teeth can result in minor or major malocclusion that may potentially be painful for these dogs. The primary teeth need to be removed immediately in an attempt to avoid the development of malocclusions! To perform these procedures appropriately, dental radiographs are required.
Cats have teeth, and it is useful to know the correct number and alignment of teeth!
Kittens normally have 26 teeth and adult cats have 30 teeth (dental chart). The transition from the primary (baby) teeth to the secondary (adult) teeth is quicker in cats than in dogs. Our clinical experience of malocclusions is significantly lower in cats than in dogs, however, malocclusions do occur in cats. These abnormal occlusions (bites) can result in problems for cats. Teeth hitting teeth or soft tissues, can be uncomfortable.
The question is... Is the bite right?
The bite is right when it is normal. The "scissors bite" refers to the normal relationship between the upper and lower teeth. This is also called the normal occlusion. The upper incisors overlap the lower incisors when the mouth is closed (top photo). The lower incisor crown tips rest on the inside cingulum of the opposing upper incisor teeth. The lower canine teeth fit in between the upper third incisor and the upper canine without touching either of them with the mouth closed. In viewing the teeth from the side with the mouth closed, the premolar teeth of the upper and lower dental arcades interdigitate very much like the teeth of a "sheers scissors" (see photo above). Additionally; the upper fourth premolar tooth, overlaps the lower first molar tooth. These teeth function to tear food apart when chewing. These teeth are frequently referred to as carnasial teeth and are often injured (fractured) when very hard objects are chewed by dogs. We recommend prevention of chewing hard objects in an attempt to avoid fractured teeth!
Malocclusions
Malocclusions are variations of the bite from the above described normal scissors bite. Malocclusions are classified based on the dental relationships.
They are numbered one through three, with a fourth group that does not fit the first three. They are designated "Mal 1", "Mal 2" and "Mal 3".
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Mal 1; note the upper first left and right incisors rest behind the lower first and second incisor teeth. This is called "anterior crossbite".
Go to orthodontic therapy to view Dr. Kressin's management of this case.
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Class 1 (Mal 1) Notice the upper fourth premolar tooth is positioned in an abnormal position inside the lower first molar tooth. This condition is referred to as "posterior crossbite". This condition did not require treatment as the pet had a comfortable and functional occlusion (bite). Class 1 (Mal 1) malocclusions are occlusions where one or more teeth are not in the normal scissors alignment. The above two photos are examples of Class 1 malocclusion (anterior and posterior crossbite).
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Class 2 Malocclusion (Mal2). Note the upper jaw is substantially longer than the lower jaw and deeppalatal defects have developed due to trauma. This condition is sometimes called an "overbite". The mandibles are short relative to the maxillas or the maxillas are long relative to the mandibles. This also has been called mandibular brachygnathism.
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Mal 2: This dog's lower jaw was more than 1 inch shorter than the upper jaws. The lower canines caused deep puncture holes behind the upper canine teeth.
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Dental radiographs provide important information to help avoid problems.
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Post surgical radiograph demonstrates the fragile jaw structure and confirms complete extraction of the lower canines and incisor teeth.
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Class 3 Malocclusion (Mal 3). Notice the lower jaw is relatively longer than the upper jaw (viewed from under the jaw). Malocclusions that involve jaw length discrepancy are generally believed to be inherited conditions, however, this author is not aware of research or documentation to prove this belief. This malocclusion is sometimes referred to as an "underbite". The mandibles may be too long or the maxillas are too short in relation to the mandibles.
It is also called maxillary brachygnathism.
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Mal 3; Pre-operation dental radiograph.
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Dental radiograph after surgery confirms no tooth roots or fractured bone remains within the alveoli (tooth sockets).
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Harry Potter "wry bite" or class 4 malocclusion.
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We routinely see patients with class two and three malocclusions that have painful bites. We refer to this as "traumatic occlusion". Our treatment goal is to provide a comfortable bite for these patients. Treatment options are discussed in detail to allow for informed decision making during the initial consultation.
Malocclusions may be treated with orthodontic appliances or by oral surgery.
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Eli had an uncomfortable malocclusion.
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Eli's normal comfortable right side.
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Eli's left side is not comfortable. Traumatic occlusion.
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Eli has teeth striking teeth.
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Eli's malocclusion close up view.
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This malocclusion could be treated with orthodontic appliances but due to the travel distance to our office, the owner chose to treat by oral surgery.
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Surgical view; flap and alveoplasty exposed the canine and third upper incisor for careful removal.
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Surgical flap was closed.
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This is another Sheltie with a similar malocclusion treated a little differently.
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Zorro had the lower left canine tooth tipped out toward the lip.
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This side view demonstrates severe tipping. The malocclusion was caused by a retained primary (baby) left upper canine. The secondary canine was positioned too far forward. This resulted in the tipping of this canine tooth.
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Extraction of the canine was elected!
This is the pre-operative X-ray.
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This is the post operative X-ray.
Orthodontic treatment was also possible!
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This is the one week follow up view of the surgical site.
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Orthodontic Dental Services
Malocclusion can be very uncomfortable for companion animals. Treatment for these conditions requires an accurate diagnosis in all cases. Treatment planing is based directly on the diagnosis. Some cases are appropriate for "braces" (orthodontics).
Informed consent is critically important. Dr. Kressin requires a dental consultation to help make the best choice for the client and their pet.
If the bite is not right, there may be problems other than malocclusion! An abnormal bite is most often a dental malocclusion. Other potential reasons for an abnormal bite may be TMJ luxation, TMJ fracture or TMJ dysplasia, and jaw fracture.
Dental radiology provides very high detail to differentiate between mandibular jaw (bone) fracture from TMJ (joint) problems. This differentiation is not possible from a physical evaluation alone.
Dr. Kressin frequently uses CT imaging ("Cat scans") for accurate diagnosis of these TMJ problems. The great news is that the cost of CT imaging has been reduced due to the case volume we see, and the greater efficiency from increased volume of cases.
Braces (orthodontics)
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