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Canine Dental Disease
0195-5616/98 $8.00 + .00.
CANINE DENTISTRY
CANINE DENTAL DISEASE Steven E. Holmstrom, DVM
Oral disease is important for the maintenance of the patient's overall health (article 2). A complete oral examination is necessary for the diagnosis of canine dental disease. Often, examination of the oral cavity is difficult because of patient resistance, movement, difficulty in visualization, and the small size of the oral structures. General anesthesia is often required for a complete dental examination that includes radiography. In addition, recognition of disease takes practice and experience. With time, this can be mastered, and it is not unusual for small animal practices to have a veterinary dental caseload producing in excess of 20% of the total practice medical and surgical income. This article will give an overview of dental anatomy, the structures of the teeth and diseases associated with teeth, the diseases and treatments of the pulp, the diseases of the tooth supporting tissues, and finally the remainder of the oral cavity (Figs. 1-12). It is meant to be an overview as an introduction to the articles in the remainder of this issue. The primary (deciduous) canine dentition is made up of 28 teeth. In the maxilla and mandible on each side are three incisors, one canine, and three premolars. The majority of problems caused by the primary teeth are caused by their failure to exfoliate. The generally accepted rule is: "Do not permit more than one tooth of the same kind in the same place at the same time!" Generally, the primary teeth should be extracted as soon as the adult teeth start to erupt. Failure to do so may cause deflection leading to orthodontic or periodontal problems. Fractures of primary teeth may also lead to disease and should be extracted as soon after the fracture occurs as possible. The adult dog has 42 secondary teeth, 20 in the maxilla and 22 in the mandible. The incisal bone makes up the forwardmost portion of the upper jaw and contains six incisors (three on the right side and three on the left side). The incisors are used for gnawing, grooming, and severing umbilical cords. The facial bone, which contains teeth, is the maxilla. Each side of the maxilla has one canine tooth for puncturing, holding, and tearing. The incisors and canine teeth each have one root. Moving distally (away from the center of the dental
From the Companion Animal Hospital, San Carlos, California
VETERINARY CLINICS OF NORTH AMERICA: SMALL ANIMAL PRACTICE VOLUME 28 • NUMBER 5 • SEPTEMBER 1998
1049
1050
HOLMSTROM
Figure 1. The incisors and canine teeth of a young healthy dog. This patient has a slightly protrusive mandible. Figure 2. Gingivitis is inflammation of the gingiva and is very common. It is caused by accumulation of dental plaque. Figure 3. Patients with active periodontitis show evidence of loss of attachment in an area of the tooth that also shows severe gingival inflammation. Figure 4. Active periodontitis can occur on all teeth. In this patient, the maxillary fourth premolar is involved. Figure 5. Active periodontitis of the incisor teeth. Although this patient had periodontitis throughout its whole mouth, some patients may have localized periodontitis. Some areas such as the palatal surface of the maxillary incisors are difficult to see. Figure 6. Quiescent periodontitis. This patient shows a loss of attachment with recession of the gingiva and root exposure, but there is no evidence of severe inflammation or ongoing destruction present at this time.
CANINE DENTAL DISEASE
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
1051
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
1052
CANINE DENTAL DISEASE
1053
Figure 7. A fracture of the maxillary primary canine tooth has caused this stoma or fistula to be formed. Careful exodontia of t~e primary canine tooth is indicated. Figure 8. This patient suffers from multiple fractures of the maxillary fourth premolar. There is a slab fracture that has split the crown vertically. The cusp of the tooth has been forced through the split crown. This injury was caused by eating cow hooves. Figure 9. Trauma to the tooth may cause the rupture of blood vessels inside the tooth. Blood leaks into the dentinal tubules causing the tooth to be discolored red. As time goes by, the tooth turns to purple and then tan. Figure 10. This patient has a carious lesion of the mandibular first and second molar. Exodontia or endodontia is indicated as treatment. Figure 11. Chronic chewing of tennis balls has caused table wear of this patient. Radiographs are indicated to evaluate and formulate a treatment plan. Figure 12. This is the end result of years of chewing skin on the back. The incisors have been worn to the point where they have caused tongue lacerations.
Color reproduction courtesy of Pfizer Animal Health. Photographs: Steven E. Holmstrom, DVM.
1054
HOLMSTROM
arch), there are four premolars. The premolars are used for shearing and grasping food. The most mesial (toward the center of the dental arch) on each side is the first premolar. The first premolar has one root. The most distal premolar is the fourth premolar with three roots and is known as the carnassial tooth. Carnassial translates from Latin and means "flesh chewing." Shearing is a characteristic of the canine. The remaining premolars have two roots. Moving distally, there are two maxillary molars. Molars are used for grinding food. Each of the maxillary molars has three roots. The lower jaw is made up of two mandibular bones. There are three incisors on each side, one canine tooth, four premolars, and three molars. Working in pairs with the opposing maxillary teeth, their function is identical. The incisors, canines, first premolar, and last (third) molar each have one root. The remaining mandibular premolars and molars normally have two roots. Teeth may be visually missing caused by spontaneous resorption, failure to develop, failure to erupt, or by traumatic loss. The failure of a tooth to erupt may lead to cyst formation. Retained fractured roots may become infected and also lead to abscess formation. There may also be supernumerary teeth. Generally, when this occurs, it is in the incisor or premolar area. There also may be abnormal teeth known as peg teeth. Fusion of teeth roots or crowns can occur as they are developing. Dental radiology (articles 3 and 4) is one of the best methods to evaluate for missing or abnormally shaped teeth. The normal occlusion is a scissor bite where the mandibular teeth occlude palatal to the maxillary teeth. Normally, the cusp of the mandibular incisor comes to rest on the cingulum of the palatal side of the maxillary incisors. The mandibular canines occlude in the diastema (space) between the lateral incisor and maxillary canine teeth. The cusp of the mandibular first premolar occludes midway between the maxillary canine tooth and first premolar. The remainder of the premolars interdigitate in a similar fashion, the lower teeth one-half a tooth rostral to their upper counterparts. Orthodontic diseases occur when-the mandible or maxilla is either too long or too short, or when one or more teeth are out of proper alignment. This may cause discomfort for the patient. Orthodontic disease and treatment is adequately discussed in other texts and is not covered in this issue. Fractures of the maxilla and mandible can occur, and by using dental materials, the mandible and maxilla can be restored to health (article 14). TOOTH STRUCTURE Enamel
Teeth are covered with a layer of enamel. Enamel is the hardest substance in the body and is principally formed by hydroxyapatite crystals, magnesium, and other ions. Normally it is a translucent white, but it is subject to staining and shine-through color change by transmission of color from the underlying discolored dentin. Enamel is subject to wear, known as attrition, when rubbed against another tooth or abrasion when the wear is against an external substance such as chewing hair and skin. Even wear that creates a flat surface may occur from chewing tennis balls or cloth Frisbees. This may be due to dirt being trapped in the cloth adding into the abrasiveness. This wear can penetrate to the deeper layers of the teeth. Enamel hypoplasia can result from high fever during infectious diseases. It can also result iatrogenically, secondary to the extraction of primary teeth or
CANINE DENTAL DISEASE
1055
other traumatic events. The two most common types of caries in the dog are Class I and Class V. Class I caries occur on the pits and fissures of teeth on the occlusal surfaces. Class V caries occur on the gingival third of the tooth on the buccal (outside) or lingual (inside) surface. Protecting further wear and damage to the tooth may be accomplished by crown therapy (article 13) and extensive wear may require extraction of the tooth (article 15). Enamel is also subject to fractures, which, if deep enough may require restoration (article 12). Dentin
Dentin is the next tooth layer. In the adult, it makes up the bulk of the tooth and is covered by enamel supragingivally and by cementum subgingivally. Dentin is made up of hydroxyapatite crystals, collagen fibers, mucopolysaccharide substance, and water. Although grossly it appears to be solid, it is actually porous, made up of dentinal tubules that contain cellular extensions from the odontoblasts lining the pulp canal. Exposure of the dentinal tubules may cause sensitivity. Pulp Canal
The pulp canal is the inner layer of the tooth. It is made up of blood vessels, nerves, and cells. The odontoblasts line the pulp canal and are responsible for the formation of dentin. If the pulp canal is traumatized, the inflamation and swelling increases pressure in the pulp and may cause death of the odontoblasts. This may result in ruptured blood cells and leakage of blood into the dentinal tubules. As a result, the tooth will become pink tinged and later, corresponding to the breakdown of blood components, take on a purple hue. Fractured teeth with near or direct pulp exposure will in time develop disease. These are indications for endodontic therapy (articles 9-11) (Figs. 7-12). Periodontium
Surrounding the subgingival portion of the tooth is cementum, which is made up of half organic and half inorganic materials. Cementum is the tooth structure to which the periodontal ligament attaches by its fibers. The other end of the periodontal ligament is attached to the alveolar bone surrounding the teeth. The periodontal ligament suspends the tooth within its socket like a shock absorber. Immediately surrounding the teeth and covering the bone is the gingiva, which is made up of two types. The free gingiva (also known as marginal gingiva) is that portion of gingiva that is not attached directly to the tooth. The attached gingiva is the portion of gingiva directly adherent to the tooth. The area between the free gingiva and the tooth is the sulcus in healthy tissue and the periodontal pocket where there is attachment loss and periodontal disease. The gingiva is attached to the tooth through a series of hemidesmosomes at the epithelial attachment at the bottom of the sulcus. In summary, the periodontium consists of cementum, periodontal ligament, alveolar bone, and gingiva. This is the area of focus in the prevention and treatment of periodontal disease (articles 5-7) (Figs. 1-6). In severe cases, a treatment modality called "Guided Tissue Regeneration" (article 8) may be appropriate. Foreign bodies can get trapped by the teeth and cause periodontal disease,
1056
HOLMSTROM
or they may be placed there by clients or breeders in misguided attempts for orthodontic correction. Oral Cavity
The oral cavity is bound anteriorly by the lips, laterally by the cheeks, dorsally by the hard and soft palates, ventrally by the floor of the mouth, and caudally by the oral pharynx. The vestibule is the space between the lips and cheeks and the teeth and gums. Incomplete development of the lip, neoplasia, and trauma are conditions that may need surgical treatment. The ventral portion of the oral cavity is filled with the tongue. This area is subject to infection, neoplasia, trauma. Oral surgical techniques may be the indicated treatment. By completing an oral examination, many subtle conditions can be diag~ nosed. Using the information and techniques described in the following chapters, the reader will be able to better treat the veterinary patient. References 1. Harvey CE, Emily PP: Small Animal Dentistry. St. Louis, Mosby, 1993, pp 266-296 2. Holmstrom SE, Frost P, Gammon RL: Dental prophylaxis. In Veterinary Dental Techniques. Philadelphia, WB Saunders, 1992, pp 339-387 3. Wiggs BB, Lobprise HB: Dental and oral radiology. In Wiggs RB, Lobprise HB (eds): Veterinary Dentistry Principles and Practice. Philadelphia, Lippincott-Raven, 1997, pp 435-481 Address reprint requests to: Steven E. Holmstrom, DVM Companion Animal Hospital 255 Old County Road San Carlos, CA 94070
[email protected]
CANINE DENTISTRY
CANINE DENTAL DISEASE Steven E. Holmstrom, DVM
Oral disease is important for the maintenance of the patient's overall health (article 2). A complete oral examination is necessary for the diagnosis of canine dental disease. Often, examination of the oral cavity is difficult because of patient resistance, movement, difficulty in visualization, and the small size of the oral structures. General anesthesia is often required for a complete dental examination that includes radiography. In addition, recognition of disease takes practice and experience. With time, this can be mastered, and it is not unusual for small animal practices to have a veterinary dental caseload producing in excess of 20% of the total practice medical and surgical income. This article will give an overview of dental anatomy, the structures of the teeth and diseases associated with teeth, the diseases and treatments of the pulp, the diseases of the tooth supporting tissues, and finally the remainder of the oral cavity (Figs. 1-12). It is meant to be an overview as an introduction to the articles in the remainder of this issue. The primary (deciduous) canine dentition is made up of 28 teeth. In the maxilla and mandible on each side are three incisors, one canine, and three premolars. The majority of problems caused by the primary teeth are caused by their failure to exfoliate. The generally accepted rule is: "Do not permit more than one tooth of the same kind in the same place at the same time!" Generally, the primary teeth should be extracted as soon as the adult teeth start to erupt. Failure to do so may cause deflection leading to orthodontic or periodontal problems. Fractures of primary teeth may also lead to disease and should be extracted as soon after the fracture occurs as possible. The adult dog has 42 secondary teeth, 20 in the maxilla and 22 in the mandible. The incisal bone makes up the forwardmost portion of the upper jaw and contains six incisors (three on the right side and three on the left side). The incisors are used for gnawing, grooming, and severing umbilical cords. The facial bone, which contains teeth, is the maxilla. Each side of the maxilla has one canine tooth for puncturing, holding, and tearing. The incisors and canine teeth each have one root. Moving distally (away from the center of the dental
From the Companion Animal Hospital, San Carlos, California
VETERINARY CLINICS OF NORTH AMERICA: SMALL ANIMAL PRACTICE VOLUME 28 • NUMBER 5 • SEPTEMBER 1998
1049
1050
HOLMSTROM
Figure 1. The incisors and canine teeth of a young healthy dog. This patient has a slightly protrusive mandible. Figure 2. Gingivitis is inflammation of the gingiva and is very common. It is caused by accumulation of dental plaque. Figure 3. Patients with active periodontitis show evidence of loss of attachment in an area of the tooth that also shows severe gingival inflammation. Figure 4. Active periodontitis can occur on all teeth. In this patient, the maxillary fourth premolar is involved. Figure 5. Active periodontitis of the incisor teeth. Although this patient had periodontitis throughout its whole mouth, some patients may have localized periodontitis. Some areas such as the palatal surface of the maxillary incisors are difficult to see. Figure 6. Quiescent periodontitis. This patient shows a loss of attachment with recession of the gingiva and root exposure, but there is no evidence of severe inflammation or ongoing destruction present at this time.
CANINE DENTAL DISEASE
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
1051
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
1052
CANINE DENTAL DISEASE
1053
Figure 7. A fracture of the maxillary primary canine tooth has caused this stoma or fistula to be formed. Careful exodontia of t~e primary canine tooth is indicated. Figure 8. This patient suffers from multiple fractures of the maxillary fourth premolar. There is a slab fracture that has split the crown vertically. The cusp of the tooth has been forced through the split crown. This injury was caused by eating cow hooves. Figure 9. Trauma to the tooth may cause the rupture of blood vessels inside the tooth. Blood leaks into the dentinal tubules causing the tooth to be discolored red. As time goes by, the tooth turns to purple and then tan. Figure 10. This patient has a carious lesion of the mandibular first and second molar. Exodontia or endodontia is indicated as treatment. Figure 11. Chronic chewing of tennis balls has caused table wear of this patient. Radiographs are indicated to evaluate and formulate a treatment plan. Figure 12. This is the end result of years of chewing skin on the back. The incisors have been worn to the point where they have caused tongue lacerations.
Color reproduction courtesy of Pfizer Animal Health. Photographs: Steven E. Holmstrom, DVM.
1054
HOLMSTROM
arch), there are four premolars. The premolars are used for shearing and grasping food. The most mesial (toward the center of the dental arch) on each side is the first premolar. The first premolar has one root. The most distal premolar is the fourth premolar with three roots and is known as the carnassial tooth. Carnassial translates from Latin and means "flesh chewing." Shearing is a characteristic of the canine. The remaining premolars have two roots. Moving distally, there are two maxillary molars. Molars are used for grinding food. Each of the maxillary molars has three roots. The lower jaw is made up of two mandibular bones. There are three incisors on each side, one canine tooth, four premolars, and three molars. Working in pairs with the opposing maxillary teeth, their function is identical. The incisors, canines, first premolar, and last (third) molar each have one root. The remaining mandibular premolars and molars normally have two roots. Teeth may be visually missing caused by spontaneous resorption, failure to develop, failure to erupt, or by traumatic loss. The failure of a tooth to erupt may lead to cyst formation. Retained fractured roots may become infected and also lead to abscess formation. There may also be supernumerary teeth. Generally, when this occurs, it is in the incisor or premolar area. There also may be abnormal teeth known as peg teeth. Fusion of teeth roots or crowns can occur as they are developing. Dental radiology (articles 3 and 4) is one of the best methods to evaluate for missing or abnormally shaped teeth. The normal occlusion is a scissor bite where the mandibular teeth occlude palatal to the maxillary teeth. Normally, the cusp of the mandibular incisor comes to rest on the cingulum of the palatal side of the maxillary incisors. The mandibular canines occlude in the diastema (space) between the lateral incisor and maxillary canine teeth. The cusp of the mandibular first premolar occludes midway between the maxillary canine tooth and first premolar. The remainder of the premolars interdigitate in a similar fashion, the lower teeth one-half a tooth rostral to their upper counterparts. Orthodontic diseases occur when-the mandible or maxilla is either too long or too short, or when one or more teeth are out of proper alignment. This may cause discomfort for the patient. Orthodontic disease and treatment is adequately discussed in other texts and is not covered in this issue. Fractures of the maxilla and mandible can occur, and by using dental materials, the mandible and maxilla can be restored to health (article 14). TOOTH STRUCTURE Enamel
Teeth are covered with a layer of enamel. Enamel is the hardest substance in the body and is principally formed by hydroxyapatite crystals, magnesium, and other ions. Normally it is a translucent white, but it is subject to staining and shine-through color change by transmission of color from the underlying discolored dentin. Enamel is subject to wear, known as attrition, when rubbed against another tooth or abrasion when the wear is against an external substance such as chewing hair and skin. Even wear that creates a flat surface may occur from chewing tennis balls or cloth Frisbees. This may be due to dirt being trapped in the cloth adding into the abrasiveness. This wear can penetrate to the deeper layers of the teeth. Enamel hypoplasia can result from high fever during infectious diseases. It can also result iatrogenically, secondary to the extraction of primary teeth or
CANINE DENTAL DISEASE
1055
other traumatic events. The two most common types of caries in the dog are Class I and Class V. Class I caries occur on the pits and fissures of teeth on the occlusal surfaces. Class V caries occur on the gingival third of the tooth on the buccal (outside) or lingual (inside) surface. Protecting further wear and damage to the tooth may be accomplished by crown therapy (article 13) and extensive wear may require extraction of the tooth (article 15). Enamel is also subject to fractures, which, if deep enough may require restoration (article 12). Dentin
Dentin is the next tooth layer. In the adult, it makes up the bulk of the tooth and is covered by enamel supragingivally and by cementum subgingivally. Dentin is made up of hydroxyapatite crystals, collagen fibers, mucopolysaccharide substance, and water. Although grossly it appears to be solid, it is actually porous, made up of dentinal tubules that contain cellular extensions from the odontoblasts lining the pulp canal. Exposure of the dentinal tubules may cause sensitivity. Pulp Canal
The pulp canal is the inner layer of the tooth. It is made up of blood vessels, nerves, and cells. The odontoblasts line the pulp canal and are responsible for the formation of dentin. If the pulp canal is traumatized, the inflamation and swelling increases pressure in the pulp and may cause death of the odontoblasts. This may result in ruptured blood cells and leakage of blood into the dentinal tubules. As a result, the tooth will become pink tinged and later, corresponding to the breakdown of blood components, take on a purple hue. Fractured teeth with near or direct pulp exposure will in time develop disease. These are indications for endodontic therapy (articles 9-11) (Figs. 7-12). Periodontium
Surrounding the subgingival portion of the tooth is cementum, which is made up of half organic and half inorganic materials. Cementum is the tooth structure to which the periodontal ligament attaches by its fibers. The other end of the periodontal ligament is attached to the alveolar bone surrounding the teeth. The periodontal ligament suspends the tooth within its socket like a shock absorber. Immediately surrounding the teeth and covering the bone is the gingiva, which is made up of two types. The free gingiva (also known as marginal gingiva) is that portion of gingiva that is not attached directly to the tooth. The attached gingiva is the portion of gingiva directly adherent to the tooth. The area between the free gingiva and the tooth is the sulcus in healthy tissue and the periodontal pocket where there is attachment loss and periodontal disease. The gingiva is attached to the tooth through a series of hemidesmosomes at the epithelial attachment at the bottom of the sulcus. In summary, the periodontium consists of cementum, periodontal ligament, alveolar bone, and gingiva. This is the area of focus in the prevention and treatment of periodontal disease (articles 5-7) (Figs. 1-6). In severe cases, a treatment modality called "Guided Tissue Regeneration" (article 8) may be appropriate. Foreign bodies can get trapped by the teeth and cause periodontal disease,
1056
HOLMSTROM
or they may be placed there by clients or breeders in misguided attempts for orthodontic correction. Oral Cavity
The oral cavity is bound anteriorly by the lips, laterally by the cheeks, dorsally by the hard and soft palates, ventrally by the floor of the mouth, and caudally by the oral pharynx. The vestibule is the space between the lips and cheeks and the teeth and gums. Incomplete development of the lip, neoplasia, and trauma are conditions that may need surgical treatment. The ventral portion of the oral cavity is filled with the tongue. This area is subject to infection, neoplasia, trauma. Oral surgical techniques may be the indicated treatment. By completing an oral examination, many subtle conditions can be diag~ nosed. Using the information and techniques described in the following chapters, the reader will be able to better treat the veterinary patient. References 1. Harvey CE, Emily PP: Small Animal Dentistry. St. Louis, Mosby, 1993, pp 266-296 2. Holmstrom SE, Frost P, Gammon RL: Dental prophylaxis. In Veterinary Dental Techniques. Philadelphia, WB Saunders, 1992, pp 339-387 3. Wiggs BB, Lobprise HB: Dental and oral radiology. In Wiggs RB, Lobprise HB (eds): Veterinary Dentistry Principles and Practice. Philadelphia, Lippincott-Raven, 1997, pp 435-481 Address reprint requests to: Steven E. Holmstrom, DVM Companion Animal Hospital 255 Old County Road San Carlos, CA 94070
[email protected]