May/June 2013 Today’s Veterinary Practice 77

DENTAL DIAGNOSISPeer reviewed

QuestionDuring a routine visit, it is discovered that the patient—a pug—is missing a mandibular first premolar (Figure 1); there is no swelling or discharge in the area. Based on the physical examination findings, what are your differential diagnoses and thoughts on further diagnostics and treatment?

Turn to page 79 for a list of differentials, associated therapies, and further diagnostic measures.

Case of the Missing TooThBrook A. Niemiec, DVM, FAVD, Diplomate AVDC

Read the following articles by Dr. Brook Niemiec at todaysveterinarypractice.com: • TheImportanceofDentalRadiography(November/December 2011)

•DentalExtractions:FiveStepstoImproveClientEducation,SurgicalProcedures,&PatientCare (May/June 2012)

• IntrotoOralNeoplasiainDogs&Cats(July/August 2012)

Brook A. Niemiec, DVM, FAVD, Diplomate AVDC, is chief of staff of Southern California Veterinary Dental Specialties. He is the author of Small Animal Dental, Oral and Maxillofacial Disease: A Colour Handbook (Manson Publishing)

and Veterinary Periodontology (Wiley Blackwell). He founded the veterinary dental telemedicine website vetdentalrad.com, lectures at national and international conferences, and is the coordinator and instructor of the San Diego Veterinary Dental Training Center (vetdentaltraining.com). He received his DVM from University of California–Davis.

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May/June 2013 Today’s Veterinary Practice 79

DENTAL DIAGNOSIS |

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It is exceedingly common for teeth to be absent in the dental arcades of veterinary patients. If the tooth is not seen above the gumline, do not assume it is truly absent or previously extracted.

Possible etiologies for “missing” teeth include:1

1. Congenitallymissing:2 This is generally considered to be a genet-

ic problem, but can also occur secondary to significant in utero or neonatal issues. Congenitally missing teeth are common in small, toy, and brachycephalic breeds,3 with a predisposition in the Chinese Crested and Mexican hairless breeds.1 Teeth most typically affected include premolars, maxillary second and mandibular third molars, and incisors. No specific therapy is necessary.

2. Previouslyexfoliatedorextracted: While rare in juvenile patients, this cause

is common in mature to geriatric animals. Exfoliation (ie, the tooth has fallen out “on its own”) typically results from periodontal disease, but may also be trauma related. In older animals, extraction is a more likely cause. In these cases, radiographs will usually reveal evidence of a healing alveolus. Again, no specific therapy is necessary.

3. Fracturebelowthegingivalmargin: This condition is also rare in the juvenile

patient, but common in adults. Subgingival tooth fractures may occur as a result of an incomplete extraction attempt, and retained roots are actually far more common than thought.4 Dental radiographs can confirm retained roots and potential infectious lesions. Surgical extraction is generally rec-ommended to alleviate pain and endodontic infection.

4. Impactedorembedded: These teeth may be malformed or normal,

but do not erupt into the dentition because they are blocked by a structure, such as bone or tooth (deciduous or permanent) or, most commonly, by an area of thick and firm gin-giva called an operculum. This condition is most common in the first and second premo-lars of brachycephalic breeds.

It is critical to note that the first two causes for “missing” teeth require no therapy, because the teeth are truly absent. However, the remain-ing two causes can be associated with significant pathology. Therefore, all “missing” teeth should be radiographed to determine whether the cause is true absence versus subgingival pathology.5

QuestionFigure 2 is a dental radiograph of the area of the absent mandibular first premolar. Based on the physical examination findings and radiograph, what is your diagnosis and treatment plan?

Turn to page 80 for the correct answers regarding diagnosis and treatment.

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Answer

| DENTAL DIAGNOSIS

Today’s Veterinary Practice May/June 201380

Continued from page 79.

AnswerThe radiographic image reveals an unerupted mandibular first premolar tooth (white arrow). In addition, there is a significant, smooth-edged lytic lesion surrounding the tooth (red arrows). Finally, many of the teeth have been displaced (blue arrows).

The primary diagnosis is a dentigerous cyst.

Treatment recommendations include: • Surgical enucleation (removal) of the

cyst and all affected teeth1 • Sampling and submitting the cyst

lining for histopathology • Addition of an osseopromotive

substance, which benefits treatment of large lesions, such as this

• Referral to a qualified veterinary dentist for best surgical outcome.

Whataredentigerouscysts?Dentigerous cysts arise from the enamel forming organ of the unerupted/impacted tooth. The incidence of dentigerous cyst development from impacted teeth is unknown in veterinary patients, but anecdotally is approximately 50%. In a human study, pathologic changes were noted in 32.9% of cases of unerupted/impacted teeth.6

Dodentigerouscystsnegativelyimpactdentalhealth?As a dentigerous cyst grows, this pressure causes bone loss. Cysts can grow quite large in a short period of time, resulting in weakened bone and, possibly, pathologic fractures of the jaw. In addition, the cyst can become infected and create significant swelling and pain. Malignant transformation can also occur.7

Whattherapeuticmeasuresshouldbepursued?Therapy for impacted teeth is surgical extraction. If cyst formation has occurred, en bloc removal or extraction of the tooth and meticulous curettage of the lining will prove curative. n

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References1. niemiec BA. Pathology in the pediatric patient. in niemiec BA (ed). Small Animal Dental, Oral, and Maxillofacial Disease: A Color

Handbook. London: Manson Publishing, 2010, pp 89-126.2. neville Bw, damm dd, Allen CM, Bouquot Je. Abnormalities of teeth. Oral and Maxillofacial Pathology, 2nd ed. Philadelphia: wB

saunders, 2002, pp 49-106.3. Harvey Ce, emily PP. occlusion, occlusive abnormalities, and orthodontic treatment. Small Animal Dentistry. st. Louis: Mosby, 1993,

pp 266-296.4. niemiec BA. Dental Extractions Made Easier. san diego: Practical veterinary Publishing, 2012.5. niemiec BA. Case based dental radiology. Top Companion Anim Med 2008; 24(1):4-19.6. raghoebar GM, Boering G, vissink A. Clinical, radiographic, and histological characteristics of secondary retention of permanent

molars. J Dent 1991; 19:164-170.7. neville Bw, damm dd, Allen CM, Bouquot Je. odontogenic cysts and tumors. Oral and Maxillofacial Pathology, 2nd ed. Philadelphia:

wB saunders, 2002, pp 609.