By Cynthia Smith, D.V.M
With the excellent care most of our pets get today, it's amazing that the oral cavity sometimes gets overlooked until problems are severe enough that they can't be ignored. By regularly examining and caring for your pet's teeth, you can notice initial signs of dental disease (calculus, odor) before they become excessive (strong halitosis, appetite loss, mobile teeth), as well as other problems such as broken teeth or tumors.
Peridontal disease is the most common oral problem seen, present in over 85% of animals two years of age and older. As bacteria in the mouth adheres to teeth to form soft plaque, an infection process begins. The plaque may be more noticeable once calcified to become tartar (calculus) on the crown of the tooth, but it's the softer material, particularly underneath the gum that causes the most damage due to the bacteria and the body's response to it. Mild changes may include reversible swelling of the gums (gingivitis), but if left untreated, loss of tooth attachment (soft tissue and bone) can mean irreversible peridontal disease that will eventually result in tooth loss.
Prevention of peridontal disease is possible with a combination of professional dental cleaning (prophylaxis) and regular home care (brushing). If training is started at a young age and gradually progressed, pets can readily accept a good dental hygiene program. As a puppy, it's helpful to get them more accustomed to regular handling of the mouth as part of a grooming/training program. Gently lifting the lips with one hand (with the other hand holding the muzzle closed or placed on top of the head) allows for visualization of the teeth with minimal restraint. Moving on to softly touching the teeth, with the finger either bare or wrapped in a gauze or soft washcloth, can then be followed by a gentle motion on the tooth surface. Initially the cloth can be moistened with water and even sprinkled with garlic powder (not salt) to make the experience a little more pleasant. Of course, progressing to a toothpaste would be recommended, especially if mouth odor is an issue. If toothbrushes are used,they should be soft, and replaced on a fairly regular basis to avoid excessive bacterial build-up.
Even with good home care, most individuals require a complete prophylaxis ona regular basis, anywhere from 3-18 months apart, depending on the amount of problems involved. In order to get the best cleaning of the tooth surface under the gum line (subgingival), full anesthesia is required with a cuffed endotracheal tube to protect the airways from fluid and debris. The use of isoflurane inhalant anesthetic has lessened the risk of general anesthesia.
In Shih Tzu dogs, as it is in most small breeds, the crowding of teeth in small jaw spaces can cause rotation and increased incidence of peridontal disease. That, coupled with the fact that any bone loss in a small animal can be very significant, increases the importance of preventative dental care. Regular dental care as well as a hard diet (as opposed to soft food) can help give the teeth a better chance.
Other problems seen in smaller breeds, particularly brachycephalic breeds with upper jaws proportionally shorter, may include various malocclusions. A "normal" bite usually indicates that the lower incisors are in the back of the upper incisors when the mouth is closed, which is termed a scissor bite. The relationship of the premolars in a pinking shear fashion is generally a more exact guideline when trying to assess the relative lengths of the upper and lower jaws.
Many breeds allow a level to slightlyundershot bite as their "normal," including Shih Tzu. Any form of malocclusion alters thestandard biting and chewing pattern, so periodontal disease may again be enhanced. While a good portion of malocclusions are directly controlled by hereditary influences, sometimes they are a result of individual teeth being misplaced. The most common cause of dental malalignments is retained deciduous teeth. When the primary, or baby, tooth remains in place until or even after the permanent one erupts, the adult tooth will be deflected into an abnormal position. The upper canine teeth will be moved forward, while the remainder of the canines and incisors will be moved toward the tongue. Gentle extraction of these retained teeth may help the teeth erupt into a more normal place. There are even times in younger puppies (7-10 weeks) with deciduous malocclusions that extraction of the abnormal teeth may allow for a more normal permanent tooth eruption. If the genetics for a malocclusion are present, however, this form of interceptive orthodontics will not change much.
Abnormal bites that are determined by heredity often result in a discrepancy in jaw length. Each of the fourth jaw quadrants (right and left upper, right and left lowers) are influenced by genetics independently of each other. Growth spurts in a young dog may cause a temporary malocclusion that might be corrected by a growth spurt in another portion of the jaw at a later date. This is another good reason to consider extraction of malpositioned primary teeth . The most common problems are seen when the entire upper or lower jaw is an aberrant length, but a condition may exist where one quadrant alone is significantly different, causing a deviation in the midline of that jaw. This "wry mouth" is most conspicuous when seen in the maxilla, or upper jaw, as the nose will be turned to one side, but the mandible, or lower jaw, may be affected as well.
No matter what condition your dog's teeth are in, the important thing to realize is that given an optimum program of regular home care and professional prophylaxis, it's dentition will be as healthy as can be expected. Knowing more about your pet's oral health can help alert you to problems in early stages before they become too advanced for treatment. As vital as the oral cavity is in an animal's daily function, a healthy mouth can contribute greatly to a healthy and happy dog.
From the ASTC Bulletin, October/November 1993