Investigations into the Genetic Mutations Causing Two Different Dental Anomalies in Shelties
“Lance” Canine Teeth and Abnormal 3rd Incisor Teeth
January, 2010
Dr. Gary S. Johnson of the Animal Molecular Genetic Laboratory, Department of Pathobiology, the
College of Veterinary Medicine, The University of Missouri, has graciously agreed to search for genetic mutations
underlying two different dental anomalies that occur in Shelties. Dr. Johnson’s research group has been the
recipient of several AKC Health Foundation research grants, and this group is actively working on identifying the
underlying genetic causes of various conditions in several breeds. One of the recent breakthroughs was
identification of a genetic mutation responsible for degenerative myelopathy, a progressive condition causing
irreversible paralysis, in Welsh Corgis, German Shepherd Dogs, and other breeds. Their work has resulted in DNA
tests that can be used by breeders.
The two dental conditions (“lance” canine teeth, and abnormal upper 3rd incisor teeth) are described below.
Participation of Sheltie breeders and owners are essential to the success of these studies.
Investigation of Rostrally Displaced, “Lance”, Canine Teeth in Shetland Sheepdogs
Description of the anomaly written by Mary Mahaffey, DVM, Chair, ASSA Research Advisory Committee
Background: A rostrally displaced maxillary (upper) canine tooth is one in which the adult canine tooth is displaced
forward toward the nose (rostrally) so that it comes in contact with the 3rd incisor tooth, and it is located in front of
the mandibular (lower) canine tooth rather than behind as is should (Figs. 1 & 2). The long axis of an affected tooth
is more parallel to the hard palate rather than nearly perpendicular as for a normal canine tooth. In some dogs, the
lance canine tooth can be so horizontal that the tip rubs on the upper lip. The deciduous (baby) canine teeth of
affected dogs are normally positioned; however, the abnormal position of a lance canine tooth becomes evident as
the adult tooth erupts. Because an affected tooth points forward like a lance or spear, it is commonly called a lance
canine tooth.
The abnormal position of a lance canine tooth may prevent the mouth from closing completely, and may force the
lower canine tooth to point outward causing the tip to rub the inside of the upper lip potentially causing ulceration.
Also, food and tartar tend to accumulate between the lance canine tooth and the adjacent incisor tooth increasing the
likelihood of periodontal disease between the two teeth. Although treatment is not required in all affected dogs,
therapy is necessary in some. Treatment alternatives include extraction or crown shortening of the affected canine
tooth and orthodontic repositioning which can cost several thousand dollars.
The condition is more commonly seen in Shetland Sheepdogs than other breeds and is considered to be heritable, so
affected dogs should not be bred. The goal of this study is to identify gene(s) causing lance canine teeth and to
develop a DNA test that can be used to identify adult carriers and affected puppies before the adult teeth erupt.
Fig. 1A
Fig. 1B
Fig. 1A&B. Photos of the left (A) and right (B) sides of the mouth of a 4-year-old Shetland Sheepdog with a lance
left canine tooth. The left upper canine tooth is displaced forward so that it is in front of the lower canine tooth and
its tip touches the upper 3rd incisor tooth. Compare to the normally positioned right upper canine tooth in which the
lower canine tooth is in front of the one. The right upper 2 nd premolar tooth is absent. Periodontal disease between
the lance canine tooth and the adjacent incisor tooth was avoided by daily tooth brushing.
Fig. 2: A young Sheltie with a lance left upper canine tooth that is in the process of erupting. The forward position
of the abnormal tooth is more severe than that of the dog in Figure 1. The abnormal position of this tooth was so
extreme that orthodontic repositioning was not a treatment option. The tooth was removed surgically and bone
grafting was necessary to close the communication between the nasal cavity and the space occupied by the tooth
root.
What is needed for this study:

Blood samples from two groups of dogs o
o
o



Shetland Sheepdogs with lance canine teeth (either one or both canine teeth affected)
Close relatives (siblings, sire, or dam) of one of the above dogs with normally positioned canine
teeth.
The goal is to obtain blood samples from at least 25 dogs in each group.
Pedigree of the above dogs or copy of the registration certificate.
If possible, either hard copy or digital photographs of the right and left sides of the upper canine teeth.
Completed Individual Dog Information & Survey Form (see below link).
All genetic and contact information collected for each dog will remain confidential. Specifically, your participation
in the study, your dog’s pedigree, health information you provide, and any data obtained from your dog’s DNA
sample will not be disclosed to any breeders, ASSA Club personnel, or to the AKC.
Thank you in advance for your time and effort. The sample you provide will be instrumental in helping to identify
the genomic mutations associated with lance canine teeth. It is hoped that this study will lead to a genetic test for
lance canine teeth that can be used by breeders to decrease the incidence of the problem in Shelties and identify
affected dogs at a very early age. The work would not be possible without your participation and dedication to this
wonderful breed.
Click on this link for information on sample submission and the Individual Dog Information & Survey Form.
Please contact Liz Hansen, Laboratory Coordinator, by phone (573-884-3712) or e-mail (HansenL@missouri.edu)
with any questions or concerns you may have.
Investigation of Abnormal Upper 3rd Incisor Teeth in Shetland Sheepdogs
Description of the anomaly written by Mary Mahaffey, DVM, Chair, ASSA Research Advisory Committee
Background: Over the years, Sheltie breeders have occasionally observed Shelties in which one or both of the upper
3rd incisor (I-3) teeth in adult dogs are different in size, shape, and position than normal adult I-3 teeth.1 (The I-3
teeth are the incisor teeth adjacent to the canine teeth).
In affected Sheltie puppies, only 4 - to 5 upper incisor teeth are present at 4 wks rather than the normal
number of 6. The central 4 incisors are present, but one or both I-3 teeth may be absent (Fig. 1 A&B). Around 12 –
16 wks of age, abnormal I-3 teeth erupt in most affected dogs; however, these teeth are larger than normal deciduous
teeth, but smaller than normal adult incisor teeth. When erupted, the abnormal I-3 teeth may point outwardly and
some may be rotated 90 degrees, as shown in Figs 2 B&C, 3C, & 4. The abnormal I-3 teeth may be retained
indefinitely or may be shed months or years later. If shed within a few weeks of eruption, normal adult I-3 teeth
may replace the abnormal ones; however, in older dogs, normal adult incisor teeth never appear.
Owners and judges may not recognize the presence of these abnormal I-3 teeth since they are similar to,
but slightly smaller in size than, the central four incisor teeth. However, there are distinct differences in the
appearance of the abnormal and normal adult I-3 teeth.
Normal adult upper I-3 teeth (Fig 3A):



The distal tips point down and backward toward the tips of the upper canine teeth.
They are larger than the other maxillary incisor teeth.
The caudal margins (surfaces that normally face the adjacent canine teeth) are smooth.
Abnormal upper I-3 teeth:



The distal tips point outwardly (Fig 2 C) and somewhat forward (not toward the canine teeth).
They are similar in size or slightly smaller than the other adult maxillary incisor teeth, but they are larger
than normal deciduous (baby) I-3 teeth.
The caudal surfaces are notched (Fig 1B).
Thus, the abnormal I-3 teeth have features of deciduous teeth, but they are larger than normal deciduous
teeth and rarely followed by normal adult teeth. I am aware of one Sheltie in which an adult tooth erupted within the
hard palate behind the abnormal I-3 tooth.
What is known about the inheritance of this trait is that affected dogs and normal appearing dogs (with an
affected parent) when bred to normal ones (that probably don’t carry the trait), both normal and abnormal pups are
produced. Unless one is knowledgeable about whether or not this trait is present in the relatives of a normal dog,
one cannot tell by phenotype if the dog is a carrier.
Why bother trying to develop a DNA test for this trait? The good news is that the condition, in most dogs,
is cosmetic, rarely requiring surgical correction or interfering with function of the dog like other conditions such as
hip dysplasia. However, the teeth are definitely abnormal and the trait has not been reported in other breeds to my
knowledge. Empirically, the number of affected dogs in the show population is increasing as are reports of Shelties
with missing incisors (only 4 adult central incisors with no deciduous I-3 precursors ever appearing), and dogs with
missing 2nd upper incisor teeth. Perhaps, breeding 2 carriers or affected individuals would result in a greater
number of missing incisor teeth. If breeders are unaware of the condition and the number of affected dogs continues
to increase, the condition could become so prevalent that it would be impossible to eliminate or to keep it at a low
prevalence. Superior individuals carrying the trait may well be desirable for a breeding program, and a DNA test for
this anomaly would give breeders a mechanism for identifying normal appearing carriers, thereby allowing them to
use that information in breeding decisions.
Fig. 1 A – Six week old Sheltie pup with
missing right upper 3rd incisor tooth.
Fig. 1B – Same pup as in Fig. 1A.
Fig. 2: A – right side, B – left side, and C – front view of the upper incisor teeth of a 15 wk old Sheltie. Arrows
point to the 3rd incisor teeth. A – normal 3rd incisor tooth. B – abnormal 3rd incisor tooth that is rotated. Its tip is
directed forward. C – The tip of the abnormal left 3rd incisor tooth (arrow) is pointed more outward than that of the
normal right 3rd incisor tooth. The left upper I-3 tooth was missing at 6 wks of age and the abnormal tooth started to
erupt at 12 wks of age.
Fig. 3A - C: 10 mo old
Sheltie with an
abnormal left upper 3rd
incisor (I-3) tooth.
Same dog as in Fig. 2.
(3A) – The right upper
I-3 tooth (arrow) is
normal. Notice that
the I-3 tooth is larger
than the central incisor
teeth, the caudal
margin is smooth, and
the tip points slightly
backward toward the
tip of the upper canine
tooth.
(3B) – The left upper
I-3 tooth is abnormal.
The tooth is smaller
than the other incisor
teeth, and there is a
notch (arrow) in the
caudal margin. In
this dog, the tip of the
I-3 tooth points
slightly backward;
however, in many
affected dogs, the tip
is directed more
forward than seen in
normal I-3 teeth.
(3C) - View of the
front of the incisor
teeth. Notice that
the left I-3 tooth
(black arrow) is
smaller than the
right and its tip is
pointed more
outward than that
of the right I-3
tooth (white
arrow).
Incidentally,
several of the lower
incisor teeth extend
more forward than
normal.
Fig 4 –Sheltie with an abnormal upper left 3rd incisor tooth (I-3) that is smaller than the other incisors (I-1, I-2) and
abnormally positioned so that the tip points outwardly. The upper right 3rd incisor tooth is absent. (canine = canine
tooth).
1
Curry, Barbara A: Missing and crooked teeth. Sheltie International 13: 90, 1994.
What is needed for this study:

Blood samples from two groups of dogs o
o
o



Shetland Sheepdogs with abnormal upper I-3 teeth as described above (either one or both I3 teeth affected)
Close relatives (siblings, sire, or dam) of one of the above dogs with normal upper I-3 teeth.
The goal is to obtain blood samples from at least 25 dogs in each group.
Pedigree of the above dogs or copy of the registration certificate.
If possible, either hard copy or digital photographs of the right and left sides of the upper incisor
teeth.
Completed Individual Dog Information & Survey Form (see below link).
All genetic and contact information collected for each dog will remain confidential. Specifically, your
participation in the study, your dog’s pedigree, health information you provide, and any data obtained from your
dog’s DNA sample will not be disclosed to any breeders, ASSA Club personnel, or to the AKC.
Thank you in advance for your time and effort. The sample you provide will be instrumental in helping to identify
the genomic mutations associated with abnormal upper I-3 teeth. It is hoped that this study will lead to a genetic test
that would give breeders a mechanism for identifying carriers and allow them to make informed breeding decisions
regarding this trait. The work would not be possible without your participation and dedication to this wonderful
breed.
Click on this link for information on sample submission and the Individual Dog Information & Survey Form.
Please contact Liz Hansen, Laboratory Coordinator, by phone (573-884-3712) or e-mail- HansenL@missouri.edu
with any questions or concerns you may have.