Welcome to the Clan Duncan Breeder's Notebook. All of us wear many "hats" as we travel through life. Here in the Breeder's Notebook, I put on two of my professional "hats," those of biologist and scientific illustrator, to bring you thoughts and perspectives from my own personal vision of the Sheltie. These pages are offered in a spirit of inquiry and with a desire to share.

If you are new to Shelties, I hope that this page will serve two functions: 1. better understanding of Sheltie excellences and faults, and 2. some understanding of how much knowledge, care, and planning goes into breeding a litter of good Sheltie puppies!

On this page of the Breeder's Notebook, I offer a look at Sheltie tooth alignment, bite, and jaw, including some of the common faults. I must give credit here to my very patient, sweetly tolerant Merlin, who had his lips pulled back and his mouth held open over and over again while I completed these drawings!

Note that the dental arch is smoothly rounded, not pointed or flattened. Teeth are not crowded. There is a distinct gap between the third incisor and the canine on the upper jaw. This is the slot for the lower canine to project into. This slot is absent in the lower jaw, since the upper canine projects down outside the gums. Notice that the lower jaw is narrower than the upper jaw, so that its teeth can fit inside the uppers, as we see happening in the third drawing above.

Here we see the correct Sheltie bite from the front. Note that the upper incisors are slightly in front of the lower incisors, barely touching them, so that the upper parts of the lower incisors are hidden behind the upper incisors. See how both upper and lower canines tip out to the sides, rather than being aligned straight up and down. The tops of the lower canines fit neatly into the gum slots in the upper jaws. The upper canines end outside the bottom lip, entirely outside the lower gums. The lower lip is tight to the teeth, neither sagging nor pulling tightly down away from the gums.

Correctly aligned teeth show little wear until old age, and Shelties with correctly aligned teeth are much more free of gum and tooth disease than Shelties with tooth alignment problems. Please note that many tooth alignment problems are really JAW problems.

Undershot and overshot bites are principally problems with jaw length. An undershot bite, of course, is a bite where the lower incisors are in front of the uppers. Undershot bites cause the lower canines to miss their slots in the upper jaw, placing these teeth in front of the slots. "Common knowledge" in Sheltie breeders has "known" for years that undershot bites are associated with the deeper, more well-rounded underjaws. However, I have not seen this to be a clear association. For more than 30 years, I have kept notes of undershot Shelties I have seen. My records show that of 123 undershot bites I have examined, 22 were associated with too-deep underjaw. 20 were associated with less-than adequate underjaw, and the remainder occurred with underjaws that I described as "correct in depth and roundness." Undershot jaw is caused by too long an underjaw, not too deep an underjaw. Undershot jaw causes several problems as the Sheltie ages. First, the lower incisors are not resting against and "contained" by the uppers (but instead may have the uppers "pushing" on them from behind), so they tend to float out of position and become crooked. Secondly, the lower lip tends to be pulled back tightly away from the lower gum because the lower jaw is a bit too long; a Sheltie with this problem may drool. The tips of the lower canines may "snag" the upper lip, causing incomplete closure, another cause of drooling. Also, the lower incisors may be visible when the mouth is closed. I have not illustrated "level bite," in which the tips of the incisors meet, but this is just a less extreme example of undershot bite, and results in severe incisor wear.

Overshot bites in Shelties are much more common than undershot bites. The upper incisors, of course, are SUPPOSED to be in front of the lowers, but just barely. Overshot bites can range from the nearly correct bite to grossly overshot, in which the lower jaw is an inch shorter than the upper. One individual I saw with a severely overshot bite had problems with dry palate. Her owner had resorted to putting vaseline on the front part of her Sheltie's palate several times a day to prevent the palate tissue from cracking and bleeding! Another problem with grossly overshot bites is that the tips of the lower canines may rub against the insides of the upper lips, causing sores. Also, the tips of the lower incisors may rub against the upper palate, causing more sores. "Common knowledge" in Sheltie breeders has "known" for years that overshot bites are associated with shallow, narrow underjaw. My own records show this association to be rather strong. With 464 undershot Shelties examined, 404 had underjaws I evaluated as less-than adequate, 51 had underjaws I thought were correct in depth and roundness, and only 9 had underjaws I classed as too deep. Overshot bite results from too short an underjaw. The tips of the upper canines and the upper incisors may be visible when the mouth of an overshot Sheltie is closed.

Lance canine is a condition in which the upper canines project forward before turning downward, so they interfere with the lower canines. (I have seen lower lance canine as well.) Most canine dental references state that lance canine is caused by retention of puppy canines that cause the emerging adult canines to be displaced forward as they come in. However, I have heard from many Sheltie breeders who assured me that their Shelties had had their puppy canines removed or naturally shed well before the emergence of the adult canines, and that the adult canines still came in with the lance misalignment. Sheltie adults I have seen with this problem have shown early wear on both upper and lower canines, and in many, the interference does not permit the mouth to close, so there is a gap between the upper and lower incisors when seen from the front. If the Sheltie does not have tight lips, this can cause drooling and/or protruding tongue.

Some Shelties have very, very narrow underjaws. In some, the underjaw may be deep but is still narrow. This is another degenerate characteristic. As you can imagine, a wild dog with such a narrowed underjaw could suffer fatal injury -- the underjaw snapping in two at the narrows -- when capturing vigorous prey or engaging in a fight. Breeders should keep an eye out for this problem, and breed away from it. The illustration is not an exaggeration of how narrowed the Sheltie underjaw can become. Like lance canine, narrowed underjaw causes interference among the canines (and can even affect the premolars and molars!), and can also result in an "open" bite and accelerated tooth wear. Narrowed upper jaw can cause the same interference.

Illustrated above are problems with slanted incisors. The correct scissors bite does have the incisors, particularly the lowers, slightly slanted forward, since the Sheltie is a breed with "nose forward," and the side outline of the muzzle falling away in a diagonal from the nose. However, incisors that slant too much do not provide for a bite that can nip and cut properly. Sometimes only the lowers are slanted forward, causing them to rub strongly against the backs of the uppers; after only a few years, the Sheltie's lower incisors are worn down nearly to the gumline. If both upper and lower incisors are slanted forward, extreme wear on all incisors results. Sometimes this condition is called "parrot mouth." though parrot mouth has also been used to describe the condition I call "Collie mouth."

Flattened dental arch, accompanied by crowding of the incisors, is a problem often seen in Shelties. This type of crowding can be made worse by narrowed jaw. I have found this problem to be most common in underjaws (as seen above). Crowding can also cause open bite and drooling, because crowded teeth often begin to float out of position as the dog ages, becoming even more crooked. This is especially true of the incisors closest to the lower canines, since they are forced to the "outside" of the underjaw by the flattening of the dental arch.

This is another Sheltie jaw problem that affects the teeth. Since it seems to be more common in Collies, I call it "Collie mouth." In Collie mouth, one or both jaws have a pointed, rather than a rounded, dental arch. This is not as strong a formation as a rounded structure. (If you have a plain round dowel sharpened at one end, which end is most likely to break off?) This would not be good in a wild dog, since the lower incisors would tend to break off or be pulled out. Since the "forward point" of the jaw is too narrow to support a tooth, the incisors tend to line up on each side of the "point," creating a gap between the right three incisors and the left three incisors. The center incisors tend to rotate or "fall" forward. As the Sheltie ages, the jaw becomes more and more pointed. By middle age, some of the lower incisors may rotate so far out of position that they are pointing straight forward (or even downward!), and/or may become quite crooked. This causes severe wear as they rub against the backs of the upper incisors. In many cases, the lower incisors project forward outside the lips, and they miss the upper incisors completely, causing open bite and drooling. Shelties with "Collie mouth" tend to lose lower incisors in middle age.

I haven't included every problem that occurs with Sheltie teeth and jaws, but Merlin says, "That's enough for now!"