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A correct and ideal slightly undershot Bullmastiff bite.

Bite the Bullet

Looking a prospective Bullmastiff winner in the mouth

AKC Bullmastiff Standard: Bite – Preferably level or slightly undershot. Canine teeth large and set wide apart.

The heredity of teeth and bite is mostly unknown in the canine, and it is not clear if it is dominant, recessive or polygenic for each abnormality. Teeth and bite faults can, however, be seen with a simple visual inspection by the age of 12 months.

Generally, a Bullmastiff’s puppy’s bottom jaw will continue to grow until approximately nine months old. The top jaw is also in transition and growing during this period. The bite can go either way, from level to undershot or from scissors to overbite, or from scissors to level bite. Mature bite ranges can be overshot to grossly undershot. It is a general observation in some breeds that a puppy which starts off with an overbite, even if it corrects later on, can have a higher incidence of producing more puppies with overbites. Bullmastiff puppies with undershot bites almost never correct themselves.

Abnormal bites vary in levels of severity. Some lines appear to have a higher incidence of bite faults than others, and some lines or individuals do produce more incorrect bites than breed averages, leading to a general familial inheritance pattern. Some researchers have suggested that the shortening of the muzzle and lower jaw might be responsible for incorrect bites and missing teeth in shorter-muzzled breeds such as Bullmastiffs, although I’ve never found missing teeth a problem. It has been noted that dogs with undershot bites can have parents with scissors bites, suggesting that the trait is recessive. After more than 40 years of breeding Bullmastiffs, however, I have found inheritance of bites to be totally random at times, with undershot bites and narrow underjaws producing wide underjaws and perfect bites; and, conversely, beautiful bites producing bad ones.

Upper- and lower-jaw structures appear to be independently inherited traits, and even the size of the incisors may play a role in occlusion. Trapped puppy teeth should be removed, as they can cause an incorrect misaligned bite. Abnormal size and overly vertical incisors can also create an incorrect bite.

Wry bite.


The ABA Bullmastiff Illustrated Standard suggests that there is no reason to penalize a dog that has a reverse scissors or slightly undershot bite. Because of its Bulldog background, however, the Bullmastiff with a reasonable amount of space between the upper and lower canines should only be penalized to the degree of the deviation. Wry mouth, which is a deformity, is unacceptable in Bullmastiffs as in any breed.

Large, wide set canines in the Bullmastiff are desirable and give the dog a greater holding ability, and a wider, very desirable broad underjaw. The teeth should be large and strong, with the canine teeth wide apart, and the six small teeth in front, between the canines, in an even, level row. Narrow underjaws and curved-patterned  incisors are very undesirable, as is the reversion to the Bulldog type of bite. The two jaw bones should terminate in a normal perpendicular level in the front, and the lower jaw should not protrude beyond the upper jaw, nor bend slightly upward. The repandus (bent upward) part of the underjaw with the lower lip (sometimes called the chin) must never rise above the front of the upper lip.

In judging the Bullmastiff, I see varying degrees of bites, but mainly good bites with wide underjaws and straight teeth. Missing teeth and dropped incisors are not uncommon, especially in the older dog.  I have noticed over the years that the canine teeth have gotten smaller, which I do believe is something that should be addressed in breeding programs. Without the holding power of the canines, the dog could not hold as effectively as he might with those big canines. Years ago you never saw small canines, and it was impressive to see a Bullmastiff’s mouth with huge canines and level bites. The evolution of the breed to a less moderate and more “bully” appearance has led to the reversion to the more Bulldog type of bite, although the perfect bite can and should be accomplished with the best of heads.


Ideal Bullmastiff heads.


As a breeder first, then as a judge, I have a great deal of tolerance for an imperfect bite, knowing that both the dog and bitch could do their job – as long as the bite is not wry or grossly undershot with canine teeth jutting out of the mouth. It is interesting to observe that even with a bad bite, a bitch can sever the umbilical cord, which is not done with incisors but the molars; and when a Bullmastiff jumps up and grabs your arm, he does it with his molars, not the incisors.

When mentoring new judges I never recommend going back to the bite in making a decision: There are far more important structural and type characteristics to take into consideration.


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