Head and Jaw Shape

The amazing variation of skull shapes in dogs!

The amazing variation of skull shapes in dogs!

Happy New Year all!  I hope everyone had a lovely holiday and is feeling energized for 2016!  Today I am marveling at the variety of patients we see here at Back on Track.  We have French Bulldogs, Great Danes, Papillons, Mastiffs, Corgis....dogs come in so many shapes!  While most wild dogs look relatively similar (medium sized body and hair length, long bushy tail, and cone shaped head), centuries of selective breeding and domestication of dogs have resulted in a wide variety of face and head shapes in our pets today.  Along with this variation comes a wide range of issues affecting the nose, eyes, brain, teeth, and airway, not to mention overall balance and coordination. 

There are three basic skull types in domestic breeds: long nosed (dolichocephalic), short-nosed (brachiocephalic) and medium (mesocephalic). Mesocephalic dogs tend to have the fewest head and neck related issues, which is probably why most wild dogs fall in this category.  Dolichocephalic breeds, like Greyhounds and Borzois, tend to have very narrow skulls, and may have problems with eye formation, overbites and not enough room for incisor teeth to fit properly. Brachiocephalic breeds, like Pugs and Bulldogs, often have exaggerated underbites. Whether lengthened or shortened, if the shape of the skull is distorted, the space into which the teeth erupt can be distorted as well. This results in teeth that don’t fit together properly, or “malocclusions.”

Besides being interesting, evaluation of bite and skull shape is important to appropriate posture and gaiting, because the teeth and temporomandibular joints (TMJ) are giving critical postural information to the brain. A well aligned bite results in neutral TMJs, which allow neutral posture.

Try this exercise: Stand on level ground with easy neutral stance, arms at your sides. Feel how your weight is centered between your feet. Thrust your lower jaw forward as far as you can voluntarily, creating an underbite. Wait, and feel the postural changes. Now pull the jaw back as far as you can. Most people will feel their bodies pitch forward and back with the movement of the jaw. You can experiment with side to side as well, and feel your weight shift from foot to foot. This is a cool “trick,” but it also illustrates how jaw position helps determine weight-bearing, because the top priority of the nervous system is to keep the brain safe by making sure the nearby TM joints are symmetrically stimulated, indicating that the head is level and symmetrically supported. When a dog has a congenital or genetic malocclusion, the rest of the body may have an altered posture-- which may make them susceptible to injuries over time.

Long term assymetric posture and gait leads to musculoskeletal problems like hip dysfunction, ACL tears, arthritis, and disc disease.  Besides that, a truly functional bite is also self-cleaning and evenly wearing, requiring less dental intervention over the lifetime of the dog and minimizing periodontal inflammation and infections. Take a look at your dog's head shape and bite and think about how it may affect his or her posture or balance.  As always, feel free to ask me questions too - I love this stuff!


 

Dr. G