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Disorders of Dental Hard Tissues in Dogs Brook A

Disorders of Dental Hard Tissues in Dogs Brook A

Peer Reviewed Practical

Disorders of Dental Hard Tissues in Dogs Brook A. Niemiec, DVM, FAVD, Diplomate AVDC Southern California Veterinary Dental Specialties, San Diego, California

A B any types of pathol- ogy affect small animal veteri- Mnary patients. Many of these are caused by a form of trauma, but acidic degradation, infection, and genetics also play a role.

ENAMEL HYPOCALCIFICATION/ HYPOPLASIA1-4 Figure 1. Dental radiographs of (A) left maxillary fourth (208) of dog Enamel is a very thin (< 1 mm) mate- with generalized enamel hypocalcification—the is nonvital as evidenced rial on the surface of the tooth . by the periapical lucencies (red arrows) and wider endodontic system in the distal root (blue arrow) compared to the palatine root of first (green cells initiate enamel forma- arrow), and (B) mandibular second and third (306 and 307), dem- tion, and are only present during this onstrating significant root hypoplasia—note the short roots of the second and process.5,6 Enamel is created prior to third premolars (red arrows), that the canine root only extends to the first pre- and cannot be natu- molar (second premolar root is normal), and the normal first premolar. rally repaired after teeth erupt. are listed in Table 1. These signs emphasize that prompt Causes & Development therapy is critical to the health of the patient. Hypoplasia/hypocalcification results from disruption of Prior to therapy, dental radiographs must be exposed to normal enamel development.7,8 evaluate whether tooth nonvitality or root malformation • Enamel hypocalcification occurs when normal (Figure 1) is present. amounts of enamel are produced, but are hypomineral- ized, making the enamel softer than normal. Treatment Options • occurs when the enamel produced Treatment goals include: is hard, but thin and deficient in amount. • Removing sensitivity Enamel hypocalcification can result from trauma to an • Avoiding endodontic infection by occluding the dentinal unerupted tooth, which can affect one or several adjacent tubules teeth, and is the most common acquired cause. While this • Smoothing the tooth to decrease plaque accumulation. defect may originate from external trauma, it is often as- sociated with extraction of . Enamel hypoplasia may result from a hereditary condi- Table 1. Clinical Signs of Enamel Defects tion known as imperfecta,9 which results • Affected areas stained tan to dark brown; may when a decreased amount of enamel matrix is applied to appear pitted and rough (Figure 2, page 98)10 teeth during development. In these cases, nearly all teeth, • Hard tooth surface, not soft or sticky and all surfaces, are involved. (characteristics of caries lesions) A severe systemic infectious (for example, canine distem- • Exposed as areas of malformed enamel per virus infection that occurs in puppies before the teeth exfoliate; this exposure results in significant patient have erupted) or nutritional condition may also result in discomfort11,12 improper enamel production.9 • Stained dentin, since it is porous • Increased plaque retention due to tooth 13-15 Clinical Signs & Diagnosis roughness (results in early ) • Potential infection via the dentinal tubules Common signs of enamel hypocalcification/hypoplasia

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A B

Figure 2. Dental pictures of (A) left (204) of dog with localized hypoplasia, and (B) left in dog with generalized enamel hypocalcification. Figure 3. Composite restoration applied to the tooth in Figure 2A.

Composite restoration is the most effective way to accomplish these goals (Figure 3), and it also improves tooth appearance. However, this therapy only provides a small amount of strength. Crown therapy can be performed if damage is severe and the client is in- terested in a permanent correction (Figure 4).1 Smoothing and bonded sealant application can be considered for minor areas of disease or nonstrategic teeth, and in patients whose owners have fi- nancial concerns (Figure 5). For more information on this procedure, see Bonded Sealant Application for Crown (July/August 2011), avail- able at tvpjournal.com. Extraction may be performed, but it is generally not recommended. Figure 4. Cast metal crown applied to left (304) in dog with significant localized hypoplasia. PERTINENT TOOTH ANATOMY6,12

Enamel The tooth crown is protected by a thin shell of enamel. Enamel thick- ness in cats and dogs varies from approximately 0.1 mm to 1 mm.16

Pulp Tooth is a soft tissue that contains blood vessels, nerves (sensory only), and other types of cells, including , fibroblasts, and fibrocytes. Blood enters the tooth through the apical delta, along with the nerve bundles. Figure 5. Dental picture of right Dentin side of a dog’s mouth, following full- Dentin is arranged in tubules—these extend from the pulp to either the mouth bonded sealant application for area where dentin and enamel meet () or the root generalized enamel hypocalcification. where and enamel meet (). Dentinal tubules are filled with fluid and odontoblastic tendrils, which are cytoplasmic extensions of odontoblasts. These tubules are major pathways for dif- fusion of material across dentin—a concept known as dentin permeability.17

Dentin–Pulp Complex Due to the interdependent relationship between pulp and dentin, these two tissues are best considered as one entity: the den- tin–pulp complex. Pulp and dentin function Figure. as one unit because odontoblasts, which line Medical the pulp cavity wall, project their extensions illustration into dentin. Also, odontoblasts are respon- of a sible for formation of dentin. In turn, pulp tis- maxillary sue is dependent on dentin for protection. canine in a dog

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CARIES1,2,9 Caries (in humans, commonly called A “cavities”) occur when acid dissolves the hard structures of the teeth. Reports on prevalence vary widely, which may be due to overdiagnosis of discolored surfaces,18 but caries are fairly rare in dogs and almost unheard of in cats. A study that evaluated dogs seen at a veterinary dental referral Figure 6. Caries lesion on the occlu- facility found a prevalence of 5.3%.19 sal surface of the right maxillary first

B Disorders of Dental Hard Tissues in Dogs molar (109). Causes & Development Caries lesions begin in areas where food becomes trapped (Table 2); bac- terial digestion of the food produc- es acid, which initiates the lesion.20 Therefore, home care can help avoid these lesions. Development of caries can ultimately affect the endodontic system. 1. The initial lesion—a surface decalci- Figure 9. Composite restoration of fication of the enamel—is caused by Figure 7. on the occlusal left (209)—(A) a drop in pH . surface of right maxillary first molar Pre-operative picture demonstrating 2. Demineralization follows the direc- (109); note the dark staining, which caries, and (B) postoperative picture tion of the enamel rods. mimics a caries. When touched with of composite restoration. 3. Eventually, caries breaks through a sharp explorer, this lesion was the enamel and invades the dentin. hard, in contrast to the sticky feeling with “tug back” expected with caries. damage is likely significant—creat- Once this occurs, the lesion expands ing teeth susceptible to fractures. laterally fairly quickly, as dentin is • Extraction can also be considered. less mineralized than enamel. 4. Once dentin is destroyed, the Early to moderately advanced caries: unsupported enamel will collapse, • Removal of all diseased tooth expanding the lesion. structures is required prior to res- 5. These lesions can progress into the toration. endodontic system, resulting in • Composite resin restoration is pain and infection. generally the best choice (Figure 9). • , however, is also a valid Table 2. Locations of option. Dental Caries Figure 8. Classic radiographic Lesions at or below the gingival • Occlusal surface of maxillary appearance of caries lesion on distal margin: first molars (most common) aspect of left . • ionomer restoration is most • Occlusal surfaces of other likely the best treatment.21 molars and maxillary fourth of the defect with a sharp explorer premolars (Figure 7). Healthy tooth structure is DISCOLORED (INTRINSICALLY • Deep developmental grooves solid, whereas caries is soft and sticky. STAINED) TEETH • Sides of tooth, especially When penetrating the caries, the Intrinsically stained teeth are dis- contact surfaces (smooth explorer will experience “tug back.” colored teeth in which the abnormal surface caries) Prior to therapy, dental radiographs color stems from inside the tooth, • Tooth roots must be exposed to determine the size specifically the dentin–pulp complex. of the defect and evaluate tooth vital- 1,2 Clinical Signs & Diagnosis ity. Caries appear as radiolucent areas Causes & Development Outwardly, caries appear as a discol- (Figure 8). In dogs, intrinsic staining most often ored tooth defect (Figure 6). Discol- results from blunt trauma of suffi- oration is usually brown to black, but Treatment Options cient force to cause pulp hemorrhage, can be white very early in develop- Evidence of endodontic disease: but not enough to the tooth. ment. Early lesions can mimic wear, • therapy is required However, in other dogs, there may be and are best diagnosed by tactile feel prior to restoration. no history of trauma and discoloration • Crowns are recommended since occurred for other reasons. For exam- tvpjournal.com May/June 2014 Today’s Veterinary Practice 99 | Practical Dentistry

ple, another possible, but unlikely injury, the vast majority of discol- cause, is use in very young ored teeth are nonvital. patients; most, if not all teeth, become 3. Once the tooth becomes nonvital, discolored (yellow/brown). it often becomes infected via the Intrinsic staining results when ex- blood supply, in a process known as travasated blood is forced into the den- anachoresis. tinal tubules and then degenerates: 4. Once the tooth becomes infected, it 1. A tooth stained by degenerating acts as a bacterial fortress, allowing blood products following pulp hem- to create periapical infec- orrhage appears pink immediately tion, which may spread to the entire after the injury, eventually becoming body. darker brown or gray (Figure 10). 5. Intrinsically stained teeth can also 2. Although dental pulp can heal after cause clinical abscessation. The only exceptions to the above process are: Figure 11. Intrinsic staining of A • Young patients: The large end- tip of left mandibular canine (304). odontic system and good blood supply of these patients allow them A to recover from the inflammatory , and the tooth returns to normal color in a few weeks. If this does not occur, the tooth should be considered nonvital. • Patients with only discolored cusps (rest of the tooth unaffected) (Figure 11): These teeth should be radiographed and transilluminated; B B if both results are normal, the tooth should be monitored.

Clinical Signs & Diagnosis Clinical observation is generally diag- nostic. Transillumination should be per- formed if there is any question wheth- C er the tooth is discolored (Figure 12). Figure 12. Transillumination—(A) Note: As pulp cavity diameter decreas- normal transillumination of right max- es with age, transillumination becomes illary canine (104) (note that the light less reliable and eventually impossible. passes through fairly well), and (B) transillumination of the contralateral Dental radiographs should also be tooth (note the light from exposed to determine the condition of intrinsically stained dentin). the roots. • Nonvitality is indicated by change in width of the endodontic space or D periapical lucency (Figure 13). • Pulp necrosis is indicated by a larger root canal diameter than the contralateral tooth. • Generalized pulpitis is indicated by a smaller diameter root canal space than the contralateral tooth. • Periapical lucency is evidence of Figure 13. Dental radiograph of Figure 10. Discolored (intrinsically endodontic infection, causing bony intrinsically stained left maxillary stained) teeth—(A) left mandibular resorption. canine (204); this tooth is obviously canine (304), (B) right maxillary nonvital and infected, as evidenced Normal radiographs do not indi- canine (104), (C) left maxillary first by the widened endodontic system (201), and (D) left maxillary cate that the tooth is alive and not in- (blue arrows) and periapical rarefac- fourth premolar (208). fected, but some will argue that lack tion (red arrows). of radiographic changes indicates the

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Both of these lesions are created by • Improper reduction of a maxillo- chronic contact with a hard object. facial fracture. • Abrasion is caused by a - Abrasion can be caused by many ing against something foreign. different objects but, in general, is due • is caused by tooth-on- to very aggressive chewing, which is tooth contact. more common in large breed dogs. Attrition is caused by a malocclu- • Chronic chewing on toys, such sion in which the opposing teeth are as tennis balls, wears down the in contact, which may be due to: canines and premolars (Figure 17). • A level bite—a mild class III maloc- • Chronic chewing on the skin Figure 14. Thirteen-month recheck clusion (undershot) and most com- due to allergic dermatologic disease 25 radiograph of patient in Figure 13; mon cause (Figure 15) typically wears down the canines Disorders of Dental Hard Tissues in Dogs root canal success is evidenced by • Maxillary third creating and incisors, often to the gum line resolution of the periapical rarefaction attrition on the mandibular canines (Figure 18). (green arrows), and note the slight (Figure 16) endodontic overfill (blue arrows). A tooth has responded to the insult and is vital. However, radiographs are not very specific for diagnosing infected teeth22 because: • 30% to 50% of the must be lost before it is appreciated radiographi- cally23 • The endodontic system changes 5 very gradually in older pets. B A 2001 study by Hale demonstrated Figure 15. Significant dental attrition that only 40% of intrinsically stained to incisor teeth caused by a slight class III (level) bite. teeth had radiographic signs of end- 24 odontic disease. However, when A physically examined, 92.7% were non- vital and infected. In our experience (over 1000 cases), all discolored teeth have been nonvital and infected. Figure 17. Significant abrasion (A) to 1,2 Treatment Options left maxillary canine and premolars Discolored teeth (with the exceptions due to constant tennis ball chewing; noted earlier) are generally irrevers- note the exposed and necrotic canine ibly inflamed or necrotic. Once the tooth pulp despite reparative (tertiary) endodontic system becomes nonvital B dentin on the premolars. Significant and/or infected, the tooth must be abrasion (B) to right canines of a dog removed. There are 2 main options with a tennis ball habit; the teeth are for removal. severely worn, but the root canal is not exposed. Root canal therapy is the treatment of choice for larger teeth, such as ca- nines and carnassial teeth (Figure 14). Extraction is a viable alternative for small teeth, such as incisors and pre- molars; however, root canal therapy Figure 16. Significant class III maloc- is also indicated if the client wishes to clusion in a boxer (normal for breed). save the tooth. The significant jaw length discrepan- cy (A) has created contact between the maxillary third incisor and man- ABRASION/ATTRITION1 dibular canine, resulting in significant Figure 18. Severe abrasion to the These lesions are similar to uncom- attrition on the mesiolingual aspect of mandibular incisors and canines; plicated crown fractures; however, the mandibular canines (B). This tooth note that teeth are worn down to the they result from long-term wearing can be restored, but only following gumline and both canines, as well of the tooth as opposed to a 1-time extraction, or significant crown reduc- as 402 and 303, have direct pulp traumatic event. tion of the offending incisor. exposure and are nonvital.

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• Chewing on a chain link fence graphic), required treatment is root exposure are initially exceedingly damages the distal aspect of the canal therapy or extraction. painful, and then invariably become canines (Figure 19). Treatment of dental attrition is infected. These teeth can and should generally not necessary—unless there be restored. Treatment Options is evidence of endodontic disease (clin- Common options for restoration in- All teeth with attrition or abrasion ical or radiographic)—because slow- clude bonded sealants, composite res- should be radiographed to ensure ly exposed dentin generally becomes toration, and crowns. Most of these tooth vitality. If there are signs of sclerotic and subsequently impervious techniques are easy to learn, taught endodontic disease (clinical or radio- to pain and bacterial invasion. at certain training centers, and inex- • Slight odontoplasty with a fine pensive to initiate in practice. When diamond or white stone bur should the pulp is involved (including discol- be performed to alleviate any con- oration), treatment is directed at re- tact, followed by application of a moving the infected root canal system, bonded sealant. which can be accomplished by root • Extraction or odontoplasty with canal therapy or extraction. restorative or endodontic treat- Client education is the key to gain- ment should be performed before ing acceptance of treatment recom- restoration of deep defects, such as mendations. The article Dental Ser- those on the mandibular canines vices: Good Medicine for Patients & caused by maxillary third inci- Practices (September/October 2011), sors, because the malocclusion has available at tvpjournal.com, discuss- Figure 19. Severe distal abrasion to reached equilibrium—any restor- es the client education process with right canines (maxillary > mandibu- ative creates new contact and dis- regard to dentistry. n lar), secondary to dog chewing on a comfort. chain link fence; these teeth, espe- Treatment of dental abrasion, FIGURE CREDITS cially the maxillary, are very prone such as restorative therapy, is not Figure 1: Reprinted with permission from to fracture, and should be protected generally indicated because slow pro- Small Animal Dental, Oral, and Maxillofa- (see Figure 21). cial Disease—A Colour Handbook. Nie- gression of abrasion typically results miec BA (ed). London: Manson, 2010. in sclerotic dentin. Figures 2 to 7, 20, and 22: Reprinted with Behavior modification is the most permission from Restorative Dentistry important form of therapy, and may for the General Practitioner. Niemiec BA. include: Tustin, CA: Practical Veterinary Publish- • Supervising play time ing, 2013. • Changing toys to less abrasive ones Figures 12 and 13: Courtesy Dr. Jerzy Gawor. • Modifying the cage Figures 14 and 15: Reprinted with permis- • Treating allergic dermatitis. sion from Veterinary Dental Applications Cast metal crowns can help “build in Emergency Medicine & Critical or up” canine teeth if behavior modifi- Compromised Patients. Niemiec BA (ed). Figure 20. Postoperative picture of cation is not possible and the client Tustin, CA: Practical Veterinary Publish- cast metal crown placed on the wishes to protect the tooth and pro- ing, 2012. abraded canines in Figure 17B; vide more tooth surface (Figure 20). Figures 16 to 18: Provided by Rob Yelland and reprinted with permission from Veteri- these teeth are well protected and Full-coverage cast metal crowns are should last for the life of the patient. nary Orthodontics. Niemiec BA (ed). Tustin, strongly recommended to strength- CA: Practical Veterinary Publishing, 2012. en teeth in dogs that have significant damage on the distal aspect due to fence chewing, as they are in great danger of fracturing if not protect- Brook A. ed (Figure 21).1 I have had excellent Niemiec, long-term success with this technique DVM, FAVD, in military and police dogs. However, Diplomate some veterinarians favor a three-quar- AVDC, is chief ter crown to decrease the amount of of staff of 26 tooth structure removed. Southern California Veterinary Figure 21. Postoperative picture of Dental Specialties, with offices cast metal crown placed on the IN SUMMARY in San Diego and Murrieta, abraded canine in Figure 19; the Any time dentin is exposed, tooth California, and Las Vegas, sensitivity and inflammation results. tooth is well protected and should Nevada. last for the life of the patient. In addition, teeth with direct pulp

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