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Animal Dentistry Offers Practice Opportunities
By Unknown Author
Source: Norden News, pp. 24-28, issue unknown
Leading "a dog's life" isn't as arduous as it used to be - but dogs may be paying for their comfort with an increasing number of dental problems. Soft diets and selective breeding to reduce breed sizes are two factors which contribute to deteriorating canine dental health, according to Dr. Burton C. Roe, a California veterinarian who specializes in animal dentistry. One of a handful of such specialists in the United States, Dr. Roe feels that dental care offers veterinarians an opportunity to expand their practices in the years ahead.
"Canine dentistry is in its infancy," Dr. Roe says, "but in our affluent society, people are willing to spend money on dental care for their animals. It's just a matter of educating the public to the availability of such services."
Dental work makes up about a third of Dr. Roe's practice at the Glendale Small Animal Hospital in Glendale, California, near Los Angeles. He treated his first dental patient 16 years ago at the request of a dentist friend, and the success of that experience stimulated an enduring interest in animal dentistry. Since there is no formal veterinary training or board certification available in his specialty, Dr. Roe has had to adapt most of his techniques from human dentistry. He has attended numerous dental seminars and American Dental Association meetings, and maintains close ties with local schools of dentistry. Although his technical knowledge has become increasingly sophisticated through education and experience, Dr. Roe continues to consult with a D.D.S. on specific problems.
Dr. Roe treats an average of 20 dental patients during a typical week, most of whom are referred to him by other veterinarians. An area of his hospital has recently been set aside exclusively for dental work, and a standard dental chair has been modified to hold animals. "Having the proper equipment makes a tremendous difference," Dr. Roe stresses. Almost all the hospital's dental patients are dogs. Only 1% of Dr. Roe's dental work is performed on cats, and he has never been asked to treat exotic species. Both routine dental work and orthodontia are performed, depending on the needs of the patient and the desires of the client.
PET'S TEETH REQUIRE MAINTENANCE, REPAIR
Most of the procedures performed on household pets are similar to those undergone by their owners on a routine visit to the family dentist. These include cleaning, root canal work, and repair of damaged teeth. Canine dental caries are rarely seen, chiefly because a dog's teeth are occluded in such a fashion that few spaces exist where food can collect. Gum disease, however, can be a problem for dogs. Dr. Roe believes that most clients can relate to the pain and distress of a pet with such dental problems since they have had similar experiences themselves.
Occasionally, a more unusual procedure is necessary. For example, Dr. Roe has attempted several times to reimplant teeth which have been accidentally dislodged. "All conditions must be perfect for the reattachment to succeed," he says. "The tooth must have been stored in a weak saline solution at low temperatures, and reattachment should be attempted within 24 hours of the dislodgement. Because these conditions are so strict, the reattachment often fails." One of Dr. Roe's most memorable cases proved to be an exception to this rule. Three days after a Samoyed lost a tooth in a dog fight, the dog's owner found the tooth lying on the floor of her home and came to Dr. Roe for help. After cleaning both tooth and socket thoroughly, the veterinarian reinserted the tooth and sewed the dog's gums around it. To everyone's surprise, the reattachment succeeded, and after 4 years the tooth is still in place.
SHOW ANIMALS BENEFIT FROM ORTHODONTIA
Treatment of household pets is only one part of Dr. Roe's canine dental practice. Approximately half of his cases involve orthodontic procedures performed on show dogs to help the dogs conform more closely to breed standards. Selective breeding for reduced size have given many purebred dogs a smaller jaw, but tooth size generally remains unchanged. The resultant overcrowding is a major cause of malocclusion in show animals. Dr. Roe selects such cases carefully. He will not attempt to correct serious hereditary defects, such as a severely undershot jaw or other profound malocclusion.
"It would be deceptive to disguise a negative trait which can be passed on in breeding," he says. "However, if the jaw is basically normal, and the only problem is a slight misalignment of 1 or 2 teeth, I'll work on the dog."
Many such dogs require braces, and here Dr. Roe follows human dental procedures quite closely. A model of the dog's mouth is first made from an alginate impression, and the model is sent to a dental laboratory where an orthodontic appliance is fabricated. Since standard orthodontic materials do not always work for dogs, Dr. Roe has had to experiment extensively with a variety of products and techniques. For example, precut band material will not fit a dog's teeth, so all of the bands for braces must be made individually.
Tooth extraction to create more space in the mouth, a common practice in human dentistry, is not always feasible when working with show dogs. Breed standards often prescribe desirable tooth conformation, and missing teeth may mean points lost in judging. Dr. Roe's solution is to shave the tooth enamel, reshaping the teeth on each side to gain space for realignment. Since mechanical blockage caused by the deciduous teeth often affects later occlusion of the adult teeth, an alert veterinarian may be able to forestall serious overcrowding. If an 8 to 10 week old puppy shows signs of malocclusion, Dr. Roe recommends extraction of the deciduous teeth. "Little puppies don't chew much anyway," he comments, "and the adult teeth will come in by the time they're needed."
Canine orthodontia seldom involves radical movement of the teeth, so correction can usually be achieved quite rapidly. Bands are commonly left on a dog's teeth for 2 to 3 months, and are surprisingly well-tolerated by the animal. To prevent irritation and minor infection, clients are instructed to flush the area between the dog's braces and gums regularly, using a bulb syringe or dental irrigating device (e.g. "Water Pic"). In approximatley 1 case out of 5, realigned teeth drift slightly after band removal, necessitating application of the braces for an additional month. The use of a retainer to hold teeth in place - also common in human orthodontia - does not work well with canine patients. "Dogs don't like much in their mouths, especially if the material isn't glued in place," Dr. Roe explains.
Dr. Roe administers a general anesthetic to nearly all of his dental patients, having found it impossible to perform extremely fine work on a conscious animal. Intravenous administration of sodium thiopental (Penthothal®) is most common, but occasionally a procedure demands some degree of tension in the animal's jaw muscles. "Incomplete muscle relaxation gives a better idea of how the dog's mouth will occlude when he's awake. This can be especially important when fitting a dental jacket," Dr. Roe says. For such cases, he uses xylazine (Rompun®).
DENTAL WORK BUILDS PRACTICE
Dr. Roe feels that dental work has had a measurable impact on the profitability of the Glendale Small Animal Hospital. Though fees for dental services vary, the charge for moving several teeth over a period of 2 or 3 months may range from $450 to $750, and a gold or porcelain jacket may cost the client from $175 to $250. Dr. Roe also believes that his dental cases build the total practice of the hospital, since clients who are satisfied with dental procedures tend to return for their other animal health care needs.
Because his specialty is so unusual, Dr. Roe has received ample publicity in the Los Angeles area. "People really find these dental procedures interesting," he says. "They can't believe that dogs have braces or artificial teeth. And once they are informed, they frequently have a positive attitude toward dental care for their own animals." Professional acceptance has also been excellent. Dr. Roe receives telephone calls almost every day from veterinarians who want to apply a specific dental care technique to their own practice.
In the years ahead, Dr. Roe hopes to devote 100% of his practice to dental work, referring general cases to his 4 associates. Predicting a bright future for animal dentistry, he advises other veterinarians to become involved in the field. "I believe that growing public acceptance of these services will make it profitable for most veterinarians to offer dental care on a routine basis," he concludes.
Original Doc: stca#3.doc
Histopathology Of Canine Ulcerative Stomatitis: A Review Of 65 Cases
Jamie G. Anderson, RDH, DVM, MS, DipAVDC
Colin E. Harvey, BVSc, FRCVS, DipACVS, DipAVDC
University of Pennsylvania
School of Veterinary Medicine
3900 Delancey Street
Philadelphia, PA 19104-6010
Telephone: (215) 8983350
Telefax: (215) 898-9937
To date, the clinical and histopathologic features of canine ulcerative stomatitis have been described in veterinary textbooks and in a limited number of journal articles1,2. The increasing importance of oral medicine and dentistry to the veterinary practitioner requires better characterization of the relatively common canine ulcerative lesions.
The purpose of this retrospective study was to better define ulcerative lesions as to particular histopathologic characteristics, infiltrating cell types and etiologic agents.
MATERIALS AND METHODS
Sixty-five cases of canine ulcerative stomatitis were evaluated by the biopsy service of the University of Pennsylvania, School of Veterinary Medicine. Where appropriate, in order to make a definitive diagnosis, extraoral tissues and additional oral biopsies were taken to include the interface of ulcerated and non-ulcerated tissue.
The ulcerative lesion most often seen in older animals associated with dental calculus is described as a large area of central ulceration with a smaller peripheral zone; the ulcerated area is covered by a fibrinous exudate, with an underlying bed of fairly mature granulation tissue with a modest infiltration of neutrophils. No underlying etiology is typically identified.
The histopathologically suggested etiologies for ulcerative lesions of the canine oral cavity include: plaque and calculus association, trauma, autoimmune, infectious, inflammatory, salivary hypersensitivity reaction, allergic, eosinophilic granuloma complex, and idiopathic. No etiology could be identified for 45% of the lesions. Table I describes the number of cases assigned to each suggested etiology.
A fibrinonecrotic exudate was found overlying 32% of the ulcers. In 42% of the cases where a fibrinonecrotic exudate was found, no underlying etiology was detected. Table II describes the correlation of the presence of a fibrinonecrotic exudate overlying the lesion and the final histopathologic assessment.
The cell types infiltrating the submucosal tissues primarily consisted of neutrophils, or lymphocytes and plasma cells. Macrophages and eosinophils were identified less frequently. The degree of infiltration (mild, moderate, severe) and the responsible cell type are depicted in Table III.
In six cases, extra-oral biopsies were also evaluated; skin (4), testicles/epididymis (1), small intestine (1). In only one case did the extra-oral diagnosis shed light on the etiopathogenesis of the oral ulceration; pathology seen in the oral cavity was felt to be secondary to sepsis associated with parvovirus infection. Table IV describes the histopathologic diagnosis for cases where oral and extra-oral tissues were biopsied.
Twelve percent of the lesions were felt to be autoimmune in etiology based on histopathologic evidence of some degree of separation at the level of the basal lamina. In 50% of these cases, a second oral biopsy was requested to include the interface of the ulcerated and non-ulcerated tissue so that a definitive diagnosis could be made. None of these lesions were assigned a definitive diagnosis of autoimmune disease on oral histopathology.
Of the 65 cases evaluated histopathologically, only 3 lesions (4.6%) were felt to be plaque/calculus associated. The prognosis was reported as good for these lesions.
When no etiologic agent was identified, the conclusion was made in 17% of cases that the lesion was probably traumatic in origin. The value of a detailed clinical history submitted with oral biopsies is emphasized.
There was no evidence of tumor in any of the oral ulcerative lesions. Neoplasia should be placed low on the list of differentials for patients presenting with ulcerative stomatitis.
A Type III hypersensitivity reaction to saliva was noted in three cases. These lesions were characterized by an infiltration of eosinophils. Eosinophilic granuloma complex, usually only seen in Arctic dogs was observed in a Huskie with ulcerative lesions. Histopathologic differentiation of eosinophilic granuloma complex from saliva hypersensitivity reaction is based on collagen degeneration in the former. The one lesion with an allergic component was characterized by an infiltration of both eosinophils and mast cells.
The fibrinonecrotic exudate found overlying 32% of the ulcers was not significantly related to a specific final diagnosis.
In the eight cases (12%) where autoimmune disease was suspected, a second biopsy was requested to include the interface of ulcerated and non-ulcerated tissue in an attempt to make a definitive diagnosis. The antinuclear antibody (ANA) status was not evaluated.
Because twenty-nine cases (45%) had no identifiable etiology, other diagnostic modalities including immunofluorescence assays, virus isolation, and microbiologic culturing should be considered to more clearly define the etiopathogenesis of canine ulcerative stomatitis.
Like canine ulcerative stomatitis, histopathology of the human ulcerative stomatitis lesions are non-diagnostic. As well, routine serum ANA's in people are generally negative. In 1990, a new association was made for human chronic ulcerative stomatitis utilizing immunofluorescence assays 3. Chronic oral ulceration was associated with a stratified epithelium-specific antibody (SES-ANA) that reacts predominantly with the basal layer of the epithelium 4-6. Description of a specific immunologic marker (SES-ANA) for canine ulcerative stomatitis has not been made. Immunofluorescence evaluation of canine ulcerative lesions is in progress (Anderson, JG) with the hope that better definition of the lesion will allow for more specific therapy.
TABLE I Suggested Etiologies for Ulcerative Lesions of Oral Cavity
# cases/% of total
# cases/% of total
TABLE II Correlation of fibrinonecrotic exudate overlaying lesion and final histopathologic assessment
Suggested Etiologies for Oral Ulcerative Lesions
# with fibrinonecrotic exudate/% of total
Salivary hypersensitivity reaction
Eosinophilic granuloma complex
TABLE III Number of cases, Degree and Cell Type Infiltrating Submucosal Tissue
TABLE IV Etiopathogenesis of Biopsies from Extra Oral and Oral Ulcerative Lesions
2. McKeever PJ, Klausner JS: Plant Awn, Candidal, Nocardial, and Necrotizing Ulcerative Stomatitis in the Dog. JAAHA 22:17-24, 1986.
3. Jaremko WM, Beutner EH, Kumar V, et. Al: Chronic ulcerative stomatitis associated with a specific immunologic marker. J. Am. Acad. Dermatol. 22:215-220.
4. Beutner EH, Jaremko WM, Kumar V, et. Al: Stratified epithelium specific antinuclear antibodies (SES-ANA) in chronic ulcerative stomatitis (CUS): Is SES-ANA associated CUS a new clinical entity: J. Invest. Dermatol. 92:403, 1989.
5. Beutner EH, Chorzelski TP, Parodi A, et. Al: Ten cases of chronic ulcerative stomatitis with stratified epithelium-specific antinuclear antibody. J. Am. Acad. Dermatol. 24: 781-782, 1991.
6. Church LF, Schosser RH: Chronic ulcerative stomatitis associated with stratified epithelial specific antinuclear antibodies. Oral Surg. Oral Med. Oral Pathol. 73:579-582. 1992.
Original Doc: stomatit.doc
Proper Canine Dental Care
(VETERINARY NEWS - Edited by Marjorie Danser)
Pets are living longer and experiencing more dental and oral disease. Experts around the country warn that dental disease is the most common problem in the pet population, while its care is one of the most neglected areas of pet health today. Owners and veterinarians can work together to insure healthy teeth and gums in their dogs. As with humans, this requires lifelong attention - the best time to start treatment is during a puppy's first examination.
Vets recommend bringing pets in one or two times per year for professional teeth cleaning, which usually involves scaling - removal of the built-up calculus and plaque around the tooth using a hand scaler or an ultrasonic tip - followed by polishing. In most cases, the dog will be placed under general anesthesia for the cleaning. Afterward, the owner should flush the dog's mouth with a special rinse once a day for two weeks.
For home dental care, a soft toothbrush or cloth should be used to remove plaque once a week. Baking soda and water or specialized pastes for dogs should be used - never human toothpaste, which can upset a dog's stomach. Changing a dog's diet to include more dry dog food, kibble, dog biscuits and rawhide chew bones can help to reduce plaque and calculus build-up.
A symptom of periodontal disease is halitosis in an otherwise healthy dog. In a dog suffering from infection and pain, eating can be affected and weight loss may occur. Also, since the teeth have a direct connection with the sinuses, oral-nasal fistulas as well as chronic tonsillitis may develop. A dog in pain may begin to display aggressive behavior or withdraw, making it difficult to handle as well.
Besides gingivitis, inherited dental abnormalities can cause occlusion and chewing problems, which only worsen if left untreated. Dogs with teeth chipped as a result of accident or injury are susceptible to bacteria and infection entering the tooth. Root canal therapy may be necessary to block it off.
Tetracycline antibiotics administered to puppies can cause a permanent discoloration of their tooth enamel: a pregnant bitch may pass that antibiotic on to her pups, who may then be born with discolored teeth. (Consult your veterinarian before administering tetracycline to pregnant bitches or puppies.) Luckily, cavities are not a common problem in dogs, nor are dogs adversely affected by tooth extractions.
The majority of dental problems can be prevented or minimized by regular at-home care and visits to the veterinarian. (Animal Health Newsletter, Volume 6, Number 10.)
Editor’s note: There are cases where necessary dental procedures might require disqualitication from the show and obedience rings. Even if such procedures as braces to correct a bite, caps or bonding to repair a broken tooth, etc., are recommended by a veterinarian in order to protect the health of a dog, they would also have the effect of changing the dog’s appearance, possibly improving it, and making it impossible for a judge to evaluate the dog on its natural condition. Some breed standards also call for the faulting or disqualification of a dog with missing teeth, which would be applicable regardless of why the teeth were removed.
Original Doc: stca#1.doc
Occlusions And Malocclusions
Jan Bellows, DVM
Diplomate, American Veterinary Dental College
Diplomate, American Board of Veterinary Practitioners
All Pets Dental Clinic
Pembroke Pines, Florida 33024
Orthodontics is the science of monitoring and malocclusions (abnormal spatial relationships). Orthodontic care in veterinary dentistry is not used solely for cosmetics but rather to provide a functional and pain-free mouth.
There are three basic anatomic categories of muzzle structures in dogs. Some breeds (Collie, Greyhound, Borzoi, Saluki, Whippet) have elongated facial profiles and are called dolichocephalics. On the other end of the spectrum are the brachycephalics (Pug, Boxer, Bulldog), which have flat facial profiles. The mesocephalics (Golden Retriever, Labrador Retriever, German Shepherd, Beagle) have medium- sized facial profiles.
The canine jaw enlarges in spurts, and each quadrant (right and left uppers and lowers) develops independently. It is important to monitor each dog's growth individually because malocclusions can develop suddenly (within days) or may quickly correct without need for intervention.
TYPES OF MALOCCLUSION
Malocclusions can develop as soon as the teeth erupt (deciduous or puppy malocclusion), once all the adult teeth have erupted (permanent or adult malocclusion), or when there is a combination of deciduous and permanent teeth involved in an abnormal bite (mixed malocclusion). Two additional types of malocclusion are also described: Dental malocclusion exists when the jaw bones are normal in size and rela- tionship but the teeth are malpositioned; skeletal malocclusion exists when the teeth are normal but the jaw bones are unequal. Most dental malocclusions are developmental, whereas most skeletal malocclusions are genetic. Dental malocclusions are easier to treat than are skeletal ones.
Many terms are used to categorize malocclusions. The "Angle" (named after Dr. Angle) classification defines five main categories of dental relationships:
*Class 0 is considered normal (i.e., orthoclusion; Figures 1 and 2).
-Type 1: True normal
-Type 2: Variant normal
-Type 3: Normal class III (brachycephalic breeds)
Figure 1 A Figure I B
Figure 1. Scissors bite. Note how the upper incisors lie just in front of the lower incisors.
Figure 2. Normal interdigitation of premolars. Note the lower Figure 3. Crowded left mandibular second and third incisors.
premolar crown tips point to the interspace between the upper
Figure 4. Overjet (Class 11 malocclusion). Figure 5. Undershot occlusion with lower canine in front
of lateral upper incisor.
*Class I malocclusion, also called neutroclusion, occurs when there is neither an overbite nor an underbite but nevertheless some or all of the teeth are malpositioned. There is a normal premolar/molar relationship, although there may be a slight shift in premolar orientation, such as 1/3 to 1/2 a tooth being in front of or behind its normal position. The lower posterior (cheek) teeth are directed in front of their counterparts, while the cusp tips point to the center of the opposing interproximal spaces. This is the single most important malocclusion that serious breeders need to detect because it contains very subtle changes in the dental relationship (Figure 3).
-Type 1: Anterior crossbite
-Type 2: Posterior crossbite
-Type 3: Facial (wide) cuspids
-Type 4: Lingual (base narrow) cuspids
-Type 5: Crowded or rotated teeth
*Class II malocclusion, also termed distoclusion, brachygnathism, retrusive mandible, pig mouth, overjet, or overshot jaw, occurs when some or all of the upper jaw teeth are located markedly in front of their lower jaw counterparts (Figure 4). The upper first premolar often will oppose the first lower premolar.
-Type 1: Short mandible (also known as mandibular brachygnathism, mandibular retrognathism, mandibular retrusion, wry bite)
-Type 2: Long maxilla (maxillary protrusion, maxillary prognathism, wry bite)
*Class III malocclusion (mesioclusion, prognathism, protrusive mandible, or undershot jaw) occurs when some or all of the upper jaw teeth are markedly positioned behind the lower jaw counterparts (Figure 5). The upper premolars are often situated behind their normal position, while the upper first premolar may oppose the lower second premolar.
*Class IV occlusion occurs when part of the jaw is in front of and part in back of the opposing jaw.
There are six criteria commonly used for bite evaluation in mesocephalic or dolichocephalic breeds:
• Incisor relationship-The upper incisors should normally overlap the lower jaw incisors, and the inside surface of the upper incisors should barely touch the front surface of the lower incisors. A level bite is acceptable in some breeds.
• Canine relationship-The lower canines should interdigitate in the interproximal space between the upper lateral incisors and upper canine teeth. There should be no contact between the lower canine and either upper tooth.
• Premolar interdigitation-The cusps of the second lower premolars should point directly into the interproximal spaces between the first and second premolars. The third lower Premolars should point between the upper second and third premolars. The space between the upper and lower cusps should be level. The cusps of the upper fourth premolars should be lateral to the lower first molars.
Figure 6. Normal fourth premolar relationship. Figure 7. Anterior crossbite with the right upper central
incisor in reverse scissors bite.
Figure 8. Posterior crossbite in which the lower first Figure 9. Misdirected upper canine tooth.
Molar is abnormally located in the outside of the
upper forth premolar.
Figure 10. Level bite. Note abnormal wear pattern on Figure 11. Base narrow canines. Note the lower canine penetrating the opposing incisers. upper palate.
•Lower fourth premolar relationship-The cusp of the lower fourth premolar should be centered between the upper third and fourth premolars (Figure 6).
•Head symmetry-Perfect symmetry of the head, nasal cavity, and dentition is expected. A deviation in the growth to one side or the other is a sign of wry mouth.
•Temporal mandibular joint angle-The coronoid process and the lower jaw should form a right angle. If this angle is less than 90 degrees, there is a tendency for the jaw to be overshot; if the angle is greater than 90 degrees, there is a tendency for an undershot jaw.
The following terms and phrases are used to describe dental abnormalities:
*Anterior crossbite-A common malocclusion in which one or more of the upper incisors develop in a reverse scissors orientation. The premolar relationship should be normal. This condition can be caused by trauma from tug-of-war games, retained baby teeth, or impacted roots. It is not considered a genetic or inherited defect (Figure 7).
*Posterior crossbite-One or more of the maxillary premolars or molars occlude inside the mandibular premolars or molars rather than in the normal position on the outside (Figure 8).
*Displacement-A tooth's crown and root have moved in the same direction to lodge in an abnormal position in the mouth. Mesial displacement occurs when a tooth is displaced toward the midline of the arch and distal displacement when the tooth moves away from the midline of the arch. Lingual displacement occurs when tooth movement is directed towards the tongue. Facial displacement describes movement of a tooth away from the tongue (Figure 9).
*Level bite-incisor teeth meet edge to edge or premolars meet cusp to cusp. A level bite is actually an expression of a class III malocclusion. Even though this is an acceptable bite in some breeds, it can cause abnormal wear of the incisal (cutting) edge of opposing incisor teeth. The continual trauma that results from the incisal edges rubbing against each other can create inflammation around the tooth roots. Level bites can predispose a dog to periodontal disease and eventual tooth loss (Figure 10).
*Lingually displaced mandibular canine teeth (also called base narrow canines)-Usually occur when deciduous teeth are retained but can also develop when the lower jaw is shorter than the upper jaw. In this condition the lower canines frequently penetrate the upper palate. If left untreated, the condition can progress to form a permanent hole between the oral and nasal cavities (Figure 11).
*Open bite-An area in the mouth where a space is created by malocclusion. The teeth will not meet properly when the mouth is closed (Figures 12 to 14).
Figure 12. Open bite caused by undershot jaw. Figure 14. Extraction of upper incisor, leaving room for canine and therefore eliminating open bite.
Figure 13. Lower canine interfering with upper Figure 15. Underbite.
incisor, creating an open bite.
Figure 16. Wry bite. Note triangular defect in the incisor area.
•Overbite (vertical overlap)-The upper teeth vertically extend over the lower teeth. What is commonly referred to as an overbite is really an overjet.
•Overjet (horizontal overlap)-The upper teeth horizontally extend over the lower teeth. The upper premolars are displaced at least 25% further forward when com- pared with the lower premolars. An overjet malocclusion is never considered normal in any breed and is a genetic fault. The most commonly affected breeds are those with elongated muzzles (Collies, Shetland Sheepdogs, Dachshunds, and Borzoi).
•Rotated tooth-One or more teeth may rotate on their long axis toward or away from the tongue.
*Scissors bite (normal occlusion in doliochocephalic and mesocephalic skull breeds)-Typified by lower incisors resting on the inside surface of the upper incisors. There is a smooth curve from canine to canine without misplaced or rotated teeth. The lower canines should lie exactly between the upper lateral incisors and upper canines without touching either. Premolar crown tips should point to a space between the crowns of the opposing premolars. A reverse scissors bite exists when the lower incisors are located in front of the upper incisors. The lower canines and premolars will also be shifted forward.
• Shortened tooth-The biting edge of the tooth has not reached normal height. Partial impaction is a common cause.
• Underbite-Class III malocclusion. Some short-muzzled breeds (Boxer, Bulldog, Shih Tzu, Lhasa Apso) normally have an underbite; when it occurs in medium- or long-muzzled breeds, it is considered abnormal (Figure 15).
• Wry mouth or wry bite-One side of the jaw grows differently than the other. Wry bites appear as triangular defects in the incisor area. Some of the incisors will meet their opposing counterparts while others will not. Wry bite is a severe, inherited defect (Figure 16).
WHAT CAUSES MALOCCLUSIONS?
There are numerous genetic and nongenetic reasons for teeth to appear abnormally in the mouth. About half of the malocclusions are developmental rather than genetic.
Genetic defects cause skeletal length abnormalities (overbite, underbite, wry bite) and atypical tooth sizes. Various genes determine the shape, size, and exact location of each tooth as well as shape and size of the jaws. Defects affecting individual tooth direction may or may not be related to genetic inheritance. In the puppy the lower jaw grows forward faster than does the upper jaw. For a puppy to be mildly overshot at a young age is of minimal concern; in fact, it is preferable. By the time the dog reaches maturity, the bite will usually be normal.
It is believed that small animal genetic malocclusions are inherited as recessive traits with incomplete penetrance. This means that even animals that are homozygous for the recessive trait of malocclusion may not exhibit the defect and such deviations may not be seen in every generation. It takes at least five defect-free generations to ensure that a malocclusion has been eliminated from a certain line.
Congenital malocclusions can occur during pregnancy and the postnatal period. Causes of congenital malocclusions include traumatic whelping, infectious diseases, glandular abnormalities, suckling habits, and trauma.
Many nongenetic developmental defects are the result of retained puppy (deciduous) teeth. When a retained puppy tooth remains in the same socket as a permanent tooth, the permanent tooth is forced out of its normal position. This is a common but treatable problem. Examples of malocclusions caused by retained puppy teeth include lingually or rostrally deviated canines and anterior crossbites (Figure 17).
Humans with poor dental appearance due to irregular teeth or discrepancies of upper and lower jaw position will suffer from social prejudice. The primary reason for treating malocclusions in humans is therefore cosmetic, although straightening teeth will help prevent periodontal disease. In dogs and cats, however, orthodontic correction is performed to enhance function and prevent disease. Poorly aligned teeth can traumatically impinge on gum tissues, causing damage and discomfort. Crooked and crowded teeth accumulate debris, which increase the likelihood of periodontal disease.
Malocclusions can be corrected at any age, but, as a rule, the younger the patient, the faster the alteration will be completed. Malocclusion repair can be divided into three general categories: preventative, interceptive, and corrective.
Extraction of the baby canines and/or incisors before problems become apparent can aid in pre- venting malocclusion. This is especially true in toy breeds (Yorkshire, Maltese, etc.), which have an increased likelihood of problems due to retained puppy teeth.
Figure 17. Retained baby upper canine, causing Figure 18. Elastics placed around lower incisors and canines.
A common procedure performed by some breeders is to "trim" the puppy teeth in hopes that they will be shed early, thus preventing orthodontic problems. However, by cutting the tooth in half, nerve and blood supplies are exposed to the oral environment, which eventually causes infection and tooth loss. Additionally, this procedure is not recommended because it causes pain for the animal and, potential for infection that can affect adjoining adult teeth. To remove puppy teeth properly, the puppy is anesthetized and the entire tooth is carefully extracted under sterile conditions by a licensed veterinarian.
Interceptive orthodontics is employed when teeth begin erupting. Removal of baby incisors prior to their normal time of exfoliation may allow the permanent incisors to advance normally without interference from the baby teeth.
During development of the mouth, independent growth of both jaws may be affected by environmental or internal nongenetic factors. In breeds in which scissors bites are normal, the upper jaw may interlock if the upper incisors become trapped behind the lower ones. Since puppies sleep most of the time with the jaw closed at rest, the lower jaw, which continues to grow at the same rate as the upper jaw, prevents independent growth. Using interceptive orthodontics, the interfering front teeth (varying from 2 canines to all 16 teeth) are extracted as soon as the problem is detected or, ideally, before the dog is 4 months old.
Interceptive orthodontics does not stimulate jaw growth but rather removes interference, allowing previously interlocked growth to catch up. Unfortunately, it will not cure a preexisting genetic problem.
Corrective orthodontics refers to the controlled movement of malpositioned teeth and their attachment apparatus through bone. The best way to achieve this is through light, continuous force applied at least 6 hours daily. Corrective orthodontics has active and retention phases. The active phase uses devices (appliances) to move teeth. Once the active phase is completed, retention is usually achieved by opposing teeth; however, a retainer device is sometimes employed.
Orthodontic appliances can be attached to one or more teeth to direct them into functional occlusion. Some appliances function by pulling abnormal teeth into normal location with elastics, buttons, hooks, and brackets. With the use of such appliances, teeth can usually be saved and returned to their normal anatomy (as opposed to extraction or crown reduction).
Pet owners often apply elastic ligatures around the canines and incisors in hopes of moving teeth back into a normal occlusion. The uncontrolled, constant pressure of elastics around the gumline, however, may cause mobile teeth that move but usually will not remain in the desired location. Additionally, such teeth are often lost due to the resulting periodontal disease. Orthodontic care by a trained veterinarian spares the gingiva from direct ligature trauma (Figure 18).
Figure 19. Class III occlusion (undershot). Figure 20. Ulcers on lower jaw caused by undershot upper jaw.
Figure 21. Extraction of crowded lower incisors and crown Figure 22. Orthodontic stone model displaying anterior reduction of upper incisors to relieve trauma to lower jaw. crossbite.
Figure 23. Fixed orthodontic appliance used to pull teeth Figure 24. Corrected anterior crossbite after 3 months.
into normal occlusion.
Figure 25. Inclined plane to correct base narrow canines. Figure 26. Flostrally deviated canine tooth causing lateral displacement of lower ca- nines.
Figure 27. Corrected rostrally upper deviated canine after elastic application.
Repairing Specific Abnormalities
Skeletal malocclusions (overbite, underbite) are often treated by reducing the height of interfering teeth to decrease trauma to the gums. After reducing tooth height, protective medication is placed on the pulp and acrylic bonding is applied to seal and restore the tooth to normal function (Figures 19 to 21).
Anterior Crossbite and Level Bite
Anterior crossbites and level bites can be corrected with expansion de- vices placed on the palate behind the incisors or with a wire arch placed in front of the incisors with elastics to pull the affected incisor(s) into normal occlusion. Premolar relationship creating the malocclusion should be evaluated for genetic causes before therapy. If only the incisors are involved and all other occlusal parameters are normal, retained baby teeth or trauma are probable causes and therapy should be instituted (Figures 22 to 24).
Base Narrow Teeth
Base narrow deflection of the lower canine teeth can be repaired using inclined planes inserted on the hard palate between the upper canines. The deviated lower canine(s) moves slowly to a functional position after repeated contacts with the incline. The appliance should be made with a telescoping attachment to allow for the pup's skull growth (Figure 25).
Rostrally Displaced Canine Teeth
Rostrally displaced canine teeth are commonly corrected with power chains and direct bond brackets. To reposition teeth, removable lingual buttons are cemented to the canine, upper fourth premolar, and first molar. An elastic chain is placed between the buttons. In time the canine is pulled back to normal occlusion (Figures 26 and 27).
AMERICAN KENNEL CLUB STANDARDS RELATING TO DENTAL CORRECTIONS
A dog is considered "changed in appearance by artificial means" if it has been subjected to any type of procedure that has the effect of obscuring, disguising, or eliminating any congenital or hereditary abnormality or any undesirable characteristic or that does anything to improve a dog's natural appearance, temperament, bite, or gait.
Even procedures that are absolutely necessary to the health and comfort of a dog shall disqualify that dog from competition if the former had the incidental effect of changing or even improving the dog's appearance, bite, or gait. Other kennel club standards should be consulted for variations.
Breed Dental Specification Supplied by the American Kennel Cluba
Compiled by Jan Bellows, DVM
Affenpinscher-undershot bite with lower teeth closing closely in front of upper teeth. Level bite is acceptable if the monkey-like expression is maintained. Teeth and tongue should not show when the mouth is closed.
Lower jaw should be broad enough for the lower teeth to be straight and even
Afghan Hound-mouth should be level (i.e., the teeth from the upper jaw and lower jaw match evenly-, i.e. neither overshot nor undershot). This is a difficult mouth to breed. A scissors bite can be more easily bred into a dog than can a level mouth; a dog that has a scissors bite, where the lower teeth slip inside and rest against the teeth of the upper jaw, should not be penalized
Airedale Terrier-teeth should be white and free from discoloration or defect. Bite should be either level or vise- like. A slightly overlapping or scissors bite is permissible without preference
Akita-scissors bite preferred; level bite acceptable Alaskan Malamute-upper and lower jaws should be broad with large teeth, and incisors should meet with a scissors grip. Overshot or undershot is a fault
aInformation from the American Kennel Club Web site: www.akc.org.
American Cocker Spaniel-teeth should be sound and not too small and should meet in a scissors bite
American Eskimo Dog-scissors bite. Jaw should be strong with a full complement of close-fitting teeth American Foxhound-teeth must meet squarely. Overshot or undershot jaw is a disqualification
American Staffordshire Terrier-upper teeth should meet tightly outside lower teeth. Undershot and overshot mouths are faults
American Water Spaniel-scissors or level bite
Anatolian Shepherd-teeth and gums should be strong and healthy. Scissors bite preferred; level bite acceptable. Broken teeth are not to be faulted. Overshot, undershot, or wry bite are disqualifications
Australian Cattle Dog-teeth should be sound, strong, and regularly spaced and should grip with a scissors-like action. The lower incisors should be close behind and just touching the uppers. Should not be undershot or overshot
Australian Terrier-scissors bite with teeth of good size
Australian Shepherd-full complement of strong white teeth should meet in a scissors bite or may meet in a level bite. Disqualifications include undershot or overshot greater than 1/8 inch. Loss of contact caused by short center incisors in an otherwise correct bite shall not be judged undershot. Teeth broken or missing by accident shall not be penalized
Basenji-evenly aligned teeth in a scissors bite
Basset Hound-teeth should be large, sound, and regular and should meet in either a scissors or even bite. Overshot or undershot bite is a serious fault
Bearded Collie-teeth should be strong and white and should meet in a scissors bite. Full dentition is desirable
Bedlington Terrier-large, strong, and white teeth. Level or scissors bite. Lower canines should clasp the outer surface of the upper gum just in front of the upper canines. Upper premolars and molars should lie outside those of the lower jaw
Belgian Malinois-a full complement of strong, white teeth should be evenly set and should meet in a scissors or level bite. Overshot and undershot bites are a fault. An undershot bite in which two or more of the upper incisors lose contact with two or more of the lower incisors is a disqualification. One or more missing teeth is a serious fault
Belgian Sheepdog-full complement of strong, white teeth should be evenly set. Should not be overshot or undershot. Should have either an even bite or a scissors bite
Belgian Tervuren-full complement of strong white teeth, evenly set, meeting in a scissors or a level bite. Overshot and undershot teeth are a fault. Undershot teeth such that contact with the upper incisors is lost by two or more of the lower incisors is a disqualification. Loss of contact caused by short center incisors in an otherwise correct bite shall not be judged undershot. Broken or discolored teeth should not be penalized. Missing teeth are a fault
Bernese Mountain Dog-upper and lower jaws should be broad with large teeth. The incisors should meet with a scissors grip. Overshot or undershot is a fault
Bichon Frise-scissors bite. Undershot or overshot is severely penalized. A crooked or out-of-line tooth is permissible; missing teeth are severely faulted
Black and Tan Coonhound-teeth should fit evenly with scissors bite. Excessive deviation from scissors bite is penalized
Bloodhound-teeth should fit evenly with scissors bite. Excessive deviation from scissors bite is penalized
Border Collie-teeth and jaws should be strong and meet in a scissors bite
Border Terrier-scissors bite and strong teeth that are large in proportion to size of dog
brachygnathism-almormally short mandible
gnath(o)--combining form referring to the jaw
Lingual-pertaining to the tongue; the tooth surface facing the tongue
malocclusion-mimproper allgnment of the teeth mandible-lowerjaw
mesial-located nearer the center of the dental arch
occlusion-the way teeth align
prognathism-abnormal protrusion of one or both jaws; usually used to refer to a protruding lower jaw
retrognathism-an underdevelopment ofthe jaw in which the lower jaw is located posterior to its normal relationship with other facial structures
*Since malocclusions can develop suddenly, each dog's growth should be monitored to ensure early detection.
*Both genetic and nongenetic factors can affect the way the teeth appear in the jaw; about half of all malocclusions are developmental rather than genetic.
*Orthodontic correction is performed in dogs to enhance and restore function and prevent disease. Procedures should not be attempted by lay people but rather should be performed by a competent veterinary dentist.
Information on American Kennel Club dental specifications for approximately 150 dog breeds is listed beginning on p. 9.
One of the finest articles on puppy dentition is found in a little paperback book, Dogs, Kennels & Profits written by Bob Bartos when he was the director of Friskies Research Kennels at Carnation, Washington. For years I have had this book and thumbed through it but never really studied it because I didn't consider that I had a kennel or that I was "in dogs" to make a profit. I took out the book regularly just to admire the picture of Ch. Barden Bingo on the cover and dream of the day when I would own (or breed) something on a par with that great Scot. The book was copyrighted in 1972 but the advice is just as sound today - as I have been told by those who have done a lot of breeding.
As you no doubt know, the milk teeth loosen and drop out about the fourth month. It is important that attention is given to the pup's mouth long before the fourth month. It is important to notice the placement of the baby incisors and be prepared to anticipate problems before they arise. An underbite - or even a good bite - is no guarantee that it will be the same when the permanent teeth reach their final position. If the milk teeth do not come out on schedule, it can hinder the permanent teeth from reaching the desired positions.
An excerpt from Bob Bartos' book:
"A bad mouth can be forestalled and a good mouth retained by the following method: As dentition time approaches, between the third and fifth month, the upper incisors should be loosened and extracted before they are ready to come out by themselves. At the same time leave the lower incisors in place as long as possible. This results in the upper permanent teeth coming through quickly while retarding the lower. The upper teeth actually deflect the lowers. The working principle of this method is that permanent teeth, if hindered in their progress by a retained tooth, always deflect to the inner rather than the outer side of the mouth. All incisor teeth have a tendency to move forward in the jaw. To retain the lower incisors they must be effectively trapped or held in position by the upper permanent incisors until complete dentition is accomplished and the teeth are firmly anchored.
If the lower canine teeth are retained too long, they will force the adult canine tooth to hit the upper jaw and prevent the mouth from closing. Otherwise the lower incisors can move forward and not be trapped by the upper incisors, and an undershot bite will develop. Remove the lower deciduous canine teeth as soon as possible.
Many times seemingly hopeless cases of undershot mouths can be corrected during this period. There are puppies who have a perfect bite while carrying their deciduous teeth but end up undershot."