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Underbites in Australian Labradoodles
The Australian Labradoodle does have one known genetic issue cropping up occasionally around the globe, many breeders have yet
to be able to stop it because it does involve 8 genes, any two randomly matching can cause it and just about fifty
percent of Australian Labradoodles seem to be carriers of one of the 8, so which random breeding partners express it in
a few of their offspring is always a surprize. What is this issue, the underbite. The underbite is far from a serious
 concern compared to Hip Dysplasia, Addisons, Eye Issues, Cardiac issues and all those at a life altering level,
however it does happen and it is visable. We are trying to breed away from it, however this may be a long road since the
underbite is a genetic issue of 8 genes requiring just one to be passed by both the mother and the father. A slight
underbite in a puppy is what makes a Australian Labradoodle a pet quality puppy. Rainmaker Ranch does inform all families
if this is expressed in a puppy, it is not possible to actually see until teeth come in around 6 to 7 weeks of age.
These are slight underbites, and are typically gone by the time the adult teeth come in. It is uncommon
in our program but does occasionally occur. We request that you call our vet at 561-439-7900 if you have questions
on slight underbites and if you are adopting a puppy with a slight underbite that you have your vet discuss the issue
with our vet before your puppy arrives. We have never had a serious under bite and consider this another issue entirely.
We do not discount a slight underbite as this is a very minor issue. We do have our vet look at the jaw and teeth, at
this point we are looking at the puppy teeth that have grown in from age 6 weeks to 4 months then they fall out
and the adult teeth come in. If he determines it is a positive approach to remove some of the puppy teeth while
under for spay/neuter to allow the jaw to grow correctly on its own, he will do so and we will cover the cost. In
addition we do offer to pay for your first teeth cleaning directly to your vet of record when the time comes whenever that may be, just in case the bite did cause any additional
wear that is yet to be identified. So basically your puppy had an orthodontist on us.
Link to Vet Dentistry
DefinedAn under bite (under shot, reverse scissors bite, prognathism, class 3) occurs when the
lower teeth protrude in
front of the upper jaw teeth. Some short muzzled breeds (Boxers, English Bull Dogs, Shih-Tzus, and Lhasa Apsos)
normally have an under bite, but when it occurs in medium muzzled breeds it is abnormal. When the upper and lower
incisor teeth meet each other edge to edge, the occlusion is considered an even or level bite. Constant contact
between upper and lower incisors can cause uneven wear, periodontal disease, and early tooth loss. Level bite is
considered normal in some breeds, although it is actually an expression of under bite.
So Bite Me: A Close Look at Canine Dentition
First printed in the Aussie Times, July-August 2002
by C.A. Sharp
Bite faults are one of the first hereditary defects a fledgling dog breeder
learns to recognize. Teeth are right out there where everybody can take a
look at them. Once you learn what is right for your breed, it isn’t
difficult to recognize what is wrong. Though a dedicated cheat may
“improve” a dog’s bite through orthodonture,
there are limits to what can be done. For the most part, what you see is
what you’ve got.
In order to fully understand
bite faults, you must also understand what is correct and why. This goes
beyond having the right number of the right teeth in the right places. A
dog’s dental equipment is a direct inheritance from his wild carnivorous
ancestor, the wolf. Dog dentition is also very similar to the wolf’s
smaller cousin, the coyote. Figure 1 is a coyote skull, exhibiting a normal
canine complement of teeth. Each jaw has six incisors at the front,
followed by two canines, then eight premolars (four to a side). When we
come to the molars, the top and bottom jaws differ. The lower jaw has six
and the upper only four. A normal dog will have a total of 42 teeth.
Have you ever wondered how paleontologists know what a particular dinosaur
did for a living? They look at the teeth. The number, shape, size and
position of teeth will tell a lot about what that dinosaur’s diet was. If
you know what it ate, you can draw some good conclusions about how it might
have behaved.
We know what wolves and coyotes eat. The toolbox for delivering their
self-serve meals is carried in their mouths. They don’t have a cat’s sharp,
retractable claws and inward-turning wrists for grasping prey. Feet and
legs get the wolf or coyote to the table, but they don’t serve the bacon.
That must be done with the teeth and each type has a specific purpose.
The canines are most critical to catching and holding prey. Readers
familiar with police K9s or Schutzhund will know
that the preferred grip is a “full mouth bite:” The dog grasps the
suspect’s arm or leg well into its mouth, between its molars and premolars
and behind the canines. This is not the way a wolf does it, for reasons
that will be explained shortly.
Fig 2 Note how the canines overlap and
cross in their alignment. Wild canids, like
this coyote, use the canines to grip their prey. The interlocking
teeth prevent the prey from pulling free.
A wolf grips with the front of
his mouth. The four canine teeth puncture the prey. Their overlapping
structure (see Fig. 2,combined with jaw strength,
prevents the prey animal from pulling free. When catching bad guys, the
idea isn’t to poke them full of holes and have them for dinner, but to hang
on until the guy with the gun and the handcuffs arrives
Once the prey is down, the premolars are used for biting off chunks of meat
that are swallowed hole. The 4th upper premolar and the first lower molar
on each side are especially developed for this task. (Fig. 3) The carnasals are the most massive teeth in the canine jaw.
They are very sharp and their location mid-way down the length of the jaw
puts them at the point where jaw pressure is greatest.
The incisors, located at the front of the mouth, are for delicate work.
They nibble the last bits of meat off bones and are also handy for
scratching an itch or pulling something bothersome out of the coat or from
between the pads.
Fig 3 The carnasals
(fourth upper premolar and first lower molar) are the largest canine
teeth, designed for shearing off chunks of meat. The molars, other
than the lower carnasals, are flat for
grinding.
Molars (Fig. 3), other than
the lower carnasals, are flat for grinding plant
matter. Wolves and coyotes will eat some amount of fruits, grasses and
other plant matter. This food needs to be chewed a little to start the
digestive process. Cats, by contrast, are strict carnivores. The only plant
matter they eat is whatever happens to be inside the animal they are
eating. Cats have no molars.
All these specialized teeth are not independent entities. Their position in
the jaw is determined by their function and they require a properly formed
skull and lower jaw to function efficiently. The muzzle must be long enough
and broad enough to accommodate the teeth in their proper locations. The
animal must have sufficient bite strength to hold onto whatever it has
grabbed, be it prey or perpetrator. Jaw strength comes not only from the
muscles, but the shape of the skull.
Fig 4 Australian Shepherd (above) and
coyote (below). Aussies have a normal skull conformation, as can be
seen from the similarities between these two.
Figure 4 shows the skulls of a
coyote and an Australian Shepherd. Aussies have normally-shaped heads, so
the shape of its skull is very similar to that of the coyote. The jaw
muscles attach to the lower jaw and along the sagittal
crest, the ridge of bone along the top and back of the skull. In between it
passes over the zygomatic arch, or cheekbone.
Wrapping around the cheekbone gives the bite much more strength than would
a straight attachment from topskull to jaw. This
attachment also serves to cushion the brain case from the flailing hooves
of critters that don’t want to become dinner or get put in a pen.
You will note that the crest on the coyote is more pronounced than on the
Aussie and its teeth are proportionally larger. This is a typical
difference between domestic dogs and their wild kin. Wild canids need top efficiency from their dental equipment
to survive. We have been providing food for our dogs for so long that the
need for teeth as large and jaws as strong as their wolf ancestors has long
passed.
Fig 5 Coyote (left) and Aussie (right).
Note the straighter angulation around the zygomatic arch (cheekbone) of the Aussie. Jaw strength is reduced in the
dog by a less acute angle around the zygomatic
arch. Note the more pronounced angle in the coyote as compared to the
Aussie. (Fig. 5) This is another typical difference between wolf or coyote
and dog skulls. The larger sagital crest allows
for a larger, and therefore stronger, muscle. The only breed with an angulation around the zygomatic
arch that approaches that of the wolf is the American Pit Bull
Terrier/American Staffordshire Terrier. Pit/AmStaffs
also have a relatively short jaw, giving their heads a more cat-like
structure: Broad + Short + Strong Muscles = Lots of Bite Strength.
Breeds with long, narrow heads have even straighter angulation
around the cheekbone, and therefore an even weaker jaw. The narrow jaw may
also cause crowding of the incisors. Toy breeds with round heads often have
little or no sagittal crest and very weak jaws.
Short-muzzled breeds may not have room for all their teeth resulting in
malocclusion, meaning they don’t come together properly. The jaws of
short-muzzled breeds may also be of unequal lengths.
The more we have altered skull and jaw shape from the norm, the less
efficient the mouth has become. In some cases, this isn’t particularly
important. There is no reason for a Collie or a Chihuahua to bite with the strength of a
wolf. However, jaws that are so short it is impossible for all the teeth to
assume normal positions and undershot bites that prevent proper occlusion
of the canines and incisors are neither efficient nor functional, despite
volumes of breed lore justifying those abnormalities in breeds where they
are considered desirable.
For most breeds, like the Australian Shepherd, the skull shape has remained
relatively normal. The short muzzle of the Pug and the undershot bite of a
Bullmastiff, while quite acceptable in those breeds, would be deemed severe
faults in Aussies and other normal-skulled breeds.
Now that we know what is “right,” for most breeds, anyway, and why it is
right, let’s look at what can be wrong, why it is wrong and what, from a
breeding standpoint, can be done about it. Most breeds with normal skull
structure were originally developed to perform a function (herding,
hunting, guarding, etc.) Since that structure is the most efficient it was
maintained, with minor variations, in most functional breeds. Typical
dental faults in these breeds are missing teeth and malocclusions. It is
evident that these faults are inherited, but not a great deal is known
about the specifics of that inheritance. In some breeds, some defects
appear to have a simple mode of inheritance, but this is not the case
across all breeds. That, plus the complex nature of dental, jaw and skull
structure, indicates that in most cases the faults are likely to be
polygenic, involving a group of genes.
Missing teeth obviously are not there to do the work they are intended for.
They should be considered a fault. The degree of the fault can vary,
depending on which teeth and how many are missing. The teeth most likely to
be absent are premolars, though molars and sometimes incisors may
occasionally fail to develop. Missing a first premolar, one of the smallest
teeth, is much less a problem than missing an upper 4th premolar, a carnasal.
The more teeth that are missing, the more
faulty and less functional the bite becomes. If you have a dog with missing
teeth, it should not be bred to other dogs with missing teeth or to the
near relatives of such dogs. Though multiple missing teeth are not
specifically faulted in either Australian Shepherd standard, you should
think long and hard before using a dog that is missing more than a couple
of premolars.
Fig 6 Undershot bite.
While the molars and some of the premolars occlude properly, the
incisors and canines don't even meet and are essentially useless.
This is a farmed silver fox. Malocclusions this severe are extremely
unusual in wild foxes. (photo courtesy Lisa McDonald) Malocclusions most frequently
result from undershot and overshot bites, anterior crossbite
and wry mouth. An undershot bite occurs when the lower jaw extends beyond
the upper. This may happen because the lower jaw has grown too long or the
upper jaw is too short. Selecting for shorter muzzles can lead to underbites. An overshot bite is the opposite, with the
upper jaw longer than the lower. In either case, the teeth will not mesh
properly. With slight over or undershot bites, the incisors may be the only
teeth affected, but sometimes the difference in jaw length is extreme (Fig.
6) leaving most or all of the teeth improperly aligned against those in the
opposite jaw. A bite that is this far off will result in teeth that cannot
be used at all, teeth that interfere with each other, improper wear and, in
some cases, damage to the soft tissues of the opposite jaw by the canines.
In wry mouth, one side of the lower jaw has grown longer than the other,
skewing the end of the jaw to one side. The incisors and canines will not
align properly and may interfere. It is sometimes confused with anterior crossbite, in which some, but not all, of the lower
incisors will extend beyond the upper incisors but all other teeth mesh
properly.
Minor malocclusions, including “dropped” incisors and crooked teeth, also
occur in some dogs. Dropped incisors are center lower incisors that are
shorter than normal. Sometimes they will tip slightly outward and, when
viewed in profile, may give the appearance of a bite that is slightly
undershot. Dropped incisors tend to run in families and are therefore
hereditary. Crooked teeth may be due to crowding in a too-small or
too-narrow jaw or the result of damage to the mouth, though the former is
more likely..
Fig 7 Even (level) bite. This is a wolf. Some consider an even, or level, bite to be a type of
malocclusion. Breed standards vary on whether they do or do not fault it.
In the Australian Shepherd, the ASCA standard faults it while the AKC
standard does not. There is clearly no consensus among dog people. Those
who fault the even bite claim that it causes increased wear of the incisors,
but there is little evidence to support this. A number of years ago the
author, upon coming across a wolf with an even bite (Fig. 7), undertook a
survey of wolf dentition. Teeth and jaws were inspected on 39 wolves, 9 of
which were captive and the balance skulls of wild wolves trapped over a
wide span of time and geography. Of the 39, 16 had even bites. This
included five of the captive group, all of whom were related. Even
discounting those, fully a third of the wild wolves had even bites. No structural
fault is tolerated to this degree in a natural species, particularly in a
feature so critical to the survival of that species.
As stated previously, bite faults and missing teeth are likely to be
polygenic in inheritance. Each is also variable in the degree of fault
between individuals. Dogs that have dental faults bad enough to be
considered disqualifications under the breed standard ought not to be bred.
Minor bite faults have only minimal impact on the dog’s ability to
function. Before it is bred, the degree of a dog’s dental faults will have
to be weighed along with all the other virtues and faults the dog has. If
the dog is then considered worthy for breeding, it should not put to mates
of similar pedigree (where genes for the fault clearly lurk,) or to mates
from families where the its dental fault is known
to occur. If, when being so bred, the faulty dog throws multiple offspring
with the same dental fault, or produces affected pups with different mates,
then it should probably be withheld from any further breeding.
The normal relatives of dogs with dental faults can be bred, but since they
may carry some genes for the fault. If you own such a dog, you will want to
select mates from families where this is not known to be a problem in order
to reduce risk of perpetuating the fault.
So now you know not only what can be wrong with a bite, but why. Bite
faults are one of the easier hereditary problems to deal with. Even if you
are a relative beginner, with an understanding of dental structure and
function you can evaluate the quality of not only your own dog’s dentition,
but that of any other dogs whose mouths you might gaze into. Check out as
many as you can and remember who has (or does not have) what and who they
are related to. Armed with this knowledge, you can make informed breeding
decisions for your own dogs.
Genetics
Underbites ...Mode of inheritence
Fri Nov 24, 2006 09:00
written by Mary F Burkovich, Australian Labradoodle breeder
I had a heck of a time finding any information on the internet in regards to the mode of inheritance for underbites.
I have tried to reaseach this subject given I have produced underbites in one of my lines
My one vet seem to understand it say he understands the mode of inheritance very well so here is his explanation.
Underbites are EXPRESSED in offspring due to recessive genes only. It is not passed DOMINATELY.
There are 4 genes that control the degree of the underbite....hence underbites are graded by degree of severity from grade 1-4.
Just for the sake of those who do not understand how a recessive disorder works...it means that you need 2 copys of the gene instead of just one copy. Diseases or disorders that are dominantly expressed only need one copy.
Recessive genes are always reprented by 'lowercase' letters and dominate genes by 'capital' letter.
Example would be the color chocolate. It is a 'recessive color' which means it is represented by a lowercase 'b' and you need 2 copies in order for the color to be expressed 'bb'.
Dominate expression only needs one gene from either parent and are expressed as a 'capital' letter.
Just like the color Black is a dominate color and only needs one 'B' for a pup to be Black.
OK...back to underbites. For the sake of example...lets say that the 4 genes that control the degree of underbites is genes 'w' 'x' 'y' and 'z'.
The worst underbite like a Bulldog would be carrying 'ww' 'xx' 'yy' 'zz'
A dog with NO underbite AND not carrying any recessive genes would be 'WW' 'XX' 'YY' 'ZZ'.
Naturally I am not going to go into all the possible combinations or examples that could produce underbites as it would be too lengthy...but here are a few examples of different senerios
Seneraio 1
Dam has no Underbite but is carrying only one recessive gene ..lets say she is 'Ww' 'XX' 'YY' 'ZZ'
Sire has no underbite but is carrying only one recessive gene also..lets say he is 'WW ' 'XX' 'Yy' 'ZZ'
Result = NO pups with underbites but some may be carries of 'w' and/or 'y'
Using the same example above lets' say the sire is also carrying 'w' like the dam.
Results = you COULD have a puppy with a slight underbite IF mom passed her 'w' AND the dad passed his 'w' also. The pups with the slight underbite would be 'ww'
Senerios 2)
Dam HAS an SLIGHT Underbite and is NOT carrying other single recessives ..lets say she is 'ww' 'XX' 'YY' 'ZZ'
(she has an UNDEBITE because she is 'ww')
Sire has no underbite and is NOT carrying ANY recessive gene also..lets say he is 'WW ' 'XX' 'YY' 'ZZ'
Result = NO pups with underbites but ALL would be carriers of 'w' 'Ww' 'XX 'YY' 'ZZ"
Senerios 3)
Dam has no Underbite but is carrying several reessive genes ..lets say she is 'Ww' 'Xx' 'Yy' 'ZZ'
Sire has no underbite but is carrying several recessive gene also..lets say he is 'Ww ' 'Xx' 'YY' 'Zz'
Result = Some pups could be Grade1 underbites, some could be Grade 2, some carriers and some not carriers.
An example of a Grade 2 would be a pup that inheritated
One 'w' from both mom and dad and one 'x' from both mom and dad which resulted in the pup being
'ww' 'xx' 'YY' 'ZZ' This pup could also be a carrier for 'y' if mom passed her 'y' instead of her 'Y'
AS you can see the combinations and possibilites seem endless and the fact that it's a recessive disorder makes it's near impossible to irradicate.
If you wanted to find out if your lines are carrying underbites...then perhasp breed to another known carrier.
Problem with this type of test breeding is...
BOTH dogs would have to be carrying some of the SAME recessives.
If one dog is carrying 'w' and 'x' and the other is carrying 'y' and 'z'...you still will NOT have pups with underbites!
It's those DANG recessives that end up being every breeders worst enemy! There is nothing worst than trying to irradict something you can't see especially when it involves severeal possible genes.
These senerios are similar to why 2 Parents with Excellent hips, but are carriers of various HD genes that can line up and can create HD pups.
ANyways...this is how Underbites were explained to me.
I can't prove if this explanation that was given to me is the gospel truth since I can't find anything in my research.
If anyone can come across modes of inheritance for underbites that can prove or disprove what I have shared...I would appreciate it if you can pass your info along .
doodles helping doodles,
Mary
(c)1995-2007 Photos and Text, reprinted with permission
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