Dr. Charlier brings to dentistry continuing education more than 35 years of small animal practice, specialty practice, and ownership experience. She has received the Peter Emily Outstanding Candidate Award and the Fellow of the Year award. In 2004, she created VDENT (Veterinary Dental Education, Networking & Training) to educate the entire veterinary healthcare team about the value of oral health and its effects on all of our patients. In 2017, she was named the NAVC Small Animal Speaker of the Year.Read Articles Written by Cindy Charlier
In the May/June issue of Today’s Veterinary Practice, “Intraoral Radiographs: Identifying Normal Anatomy” reviewed the first step in learning how to interpret intraoral radiographs. This article describes the steps involved in making clinical decisions regarding dentistry cases and recognizing radiographic findings associated with common oral diseases.
Making treatment decisions during dentistry procedures should include evaluation of intraoral radiographic findings as well as clinical oral examination findings. A clinical oral examination under general anesthesia is essential for evaluating soft tissue changes, including inflammation, gingival recession, furcation exposure, and periodontal pocket formation. Also included in the clinical examination is evaluation of the tooth itself, checking for tooth resorption, fractured teeth, worn teeth, pulp exposure, caries, and missing teeth. All abnormal clinical findings should be noted on an oral examination chart. Intraoral radiograph interpretation should be recorded in the patient’s medical record.
To determine the appropriate treatment for each tooth in each patient, consider the following questions:
- What do I see clinically during the intraoral examination? (Gingival recession? Furcation exposure? Periodontal pockets? Mobility? Tooth resorption? Fractured teeth? Abrasion/attrition? Caries? Missing teeth? Oral mass?)
- What are the intraoral radiographic findings? (Horizontal or vertical bone loss? Periapical lucency? Pulp cavity that is not consistent with the age of the patient? Changes in bone structure? Tooth resorption?)
- What tooth is involved? (Is it a strategic tooth for this patient?)
- Who is the patient? (Age? Breed? Medical history?)
- What is the client’s commitment to the pet’s oral health care? (Annual dentistry procedures? Home care? Desire to save teeth?)
Common Dental Pathology
Periodontitis is a disease of the supporting structures of the teeth (the periodontium). The periodontium includes the gingiva, periodontal ligament, cementum, and alveolar bone. The word periodontitis literally means inflammation around the tooth (perio = around, dontitis = inflammation of the tooth).
Evaluating loss of periodontal tissue support in patients with periodontitis involves radiographically assessing bone levels in combination with clinical attachment levels.1 The alveolar bone margin, the most coronal portion of the alveolar bone, is normally parallel to the plane of occlusion and 1 to 2 mm apical to the cementoenamel junction. Alveolar bone loss is a common sequela of periodontitis and may be radiographically evident as vertical or horizontal bone loss or both (BOX 1).2 Studies show that horizontal bone loss is the most common radiographic pattern of periodontal bone loss in cats.2
- Reduced alveolar crest height
- Parallel to cementoenamel junction 2 or more teeth typically involved
Vertical bone loss (FIGURE 2)
- Apical direction along the tooth root
- Perpendicular to the cementoenamel junction
- Base of the defect apical to the surrounding bone
- Associated with an infrabony pocket
A clinical examination (probing and charting) in combination with intraoral radiographs is necessary to properly diagnose periodontal disease. Subtle changes in the angle of the x-ray beam can obscure mild bone loss and stage 1 furcation exposure. Bone loss confined to the buccal or palatal side of maxillary teeth may be difficult to detect radiographically due to superimposition of other bony structures on the tooth roots (FIGURE 3).
An oronasal fistula is a direct communication between the oral and nasal cavities and occurs secondary to advanced periodontal disease affecting any of the maxillary teeth. Diagnosis requires a clinical examination and periodontal probing (FIGURE 4). The palatal surface of maxillary canine teeth in dogs cannot be evaluated with a lateral and occlusal radiograph alone due to a radiographic artifact created by the ridge in the interalveolar margin between the maxillary canine teeth and third incisors.3
Alveolar Bone Expansion in Cats
Alveolar bone expansion describes the thickening or widening of the alveolar bone commonly associated with 1 or more canine teeth in cats.4 Bone expansion results in firm swelling on the buccal surface of the canine teeth. Periodontal disease, extrusion, or tooth resorption may be associated with alveolar bone expansion. A study suggests that buccal bone width of the canine teeth up to 2 mm may be considered normal.2 On the other hand, a buccal bone width greater than 2 mm may reflect a pathologic process as 10 of 11 cats in the study with moderate or severe buccal bone expansion at 1 or more canine teeth also had severe vertical bone loss. Radiographically, alveolar bone expansion appears as a thickening of the bone affecting 1 or more canine teeth in the cat. Alveolar bone expansion may be associated with severe vertical bone loss and present as a spherical appearance to the alveolar bone (FIGURE 5).2
The term endodontic comes from the Greek words endo, meaning inside, and dontic, meaning pertaining to teeth. Endodontic disease refers to disease affecting the pulp cavity (inside part of the tooth). Tooth trauma, the most common cause of endodontic disease, results in pulp inflammation and leads to pulp necrosis and apical periodontitis (inflammation of the tissue around the apex of the tooth).
To evaluate a tooth for endodontic disease, radiographs are needed because the endodontic system of the tooth is completely hidden from view. Radiographs must include the apex of the tooth and the surrounding bone. In patients with endodontic disease, radiographic changes may be observed in the tissues around the tooth root or associated with the tooth itself (BOX 2).5
- Periapical lucency
- Increased width of the periodontal ligament space
- Loss of the lamina dura
- Diffuse or well-defined periapical lucency
Changes in the tooth itself (FIGURE 7)
- Arrested tooth maturation (nonvital tooth)
- Pulp cavity size not consistent with age of the animal or contralateral tooth
- External inflammatory root resorption affecting the tooth apex
- Internal resorption
Combined Periodontal and Endodontic Lesion
A lesion is considered combined when periodontal disease and endodontic disease affect the same tooth (FIGURE 8). A periodontal/endodontic lesion develops when bone loss resulting from periodontal disease allows bacteria to enter the pulp cavity through a lateral canal or the apex of the tooth, resulting in apical periodontitis. An endodontic/periodontal lesion occurs when a periapical lesion dissects coronally along the side of the root to exit in the sulcus.5
All teeth that appear to be missing clinically need to be radiographed. Teeth may appear to be missing for several reasons:
- Missing since birth
- Previously extracted
- Lost as a result of trauma
- Fractured below the gingival margin
- Impacted or embedded teeth
- Retained Tooth Roots
Retained tooth root fragments in dogs and cats are a common radiographic finding.6,7 Tooth roots may be retained as a result of poor extraction technique or may be fractured as a result of trauma or tooth resorption. Retained tooth roots can act as a nidus of inflammation and infection and may cause draining tracts, gingival inflammation, osteomyelitis, infection, and chronic pain.6 A recent study found that most retained tooth root fragments were associated with inflammation and supported the current recommendation for extraction of retained root fragments whenever feasible.8 For all extraction cases, postoperative radiographs are required to confirm complete extraction of all tooth root fragments (FIGURE 9).
A dentigerous cyst is a benign, non-neoplastic, well-circumscribed, cystic lesion associated with an impacted tooth. The fluid-filled cyst forms around the tooth crown and is attached to the neck of the unerupted tooth. The resulting expansile lesion can cause significant bone loss and may require extensive surgery or result in a pathologic fracture (FIGURE 10 A–D). Brachycephalic breeds are most affected. Studies show that a dentigerous cyst was associated with 29.1% to 44.4% of unerupted teeth and that the most commonly unerupted tooth was the mandibular first premolar.9,10 Early detection is critical. In young patients, it is important to count teeth after eruption to confirm the presence of all permanent teeth. Early radiographic evaluation of missing teeth can enable prevention of large dentigerous cyst formation in unerupted teeth (FIGURE 10 E AND F).
Tooth resorption is a common dental condition in cats, although the exact cause is undetermined. The lesions are characterized by odontoclastic resorption of enamel, dentin, and cementum.
Intraoral radiographs may show a focal or multifocal radiolucency on the crown of the tooth and/or roots that are being replaced by alveolar bone. A clinically visible defect in the tooth that may or may not be covered with inflamed gingival tissue usually corresponds to the radiolucency on the crown. Pulp involvement associated with odontoclastic resorption lesions does not seem to be associated with radiographically detectable periapical lucencies.11 Cats with tooth resorption are more likely than cats without tooth resorption to have severe focal vertical bone loss.2 The radiographic characteristics of the 3 types of tooth resorption in cats are described in BOX 3 and shown in FIGURE 11.
- Tooth roots are of normal density and easily distinguished from surrounding bone
- Periodontal ligament space and lamina dura are well defined
- Associated horizontal or vertical bone loss may be present
- Root structure is replaced by alveolar bone; radiodensity is similar to surrounding bone
- Periodontal ligament space or lamina dura are not visible
- Periodontal disease is not a common finding
- Multirooted tooth has type 1 resorption in 1 root and type 2 resorption in a different root
Although tooth resorption is often thought of as a feline disease, it also occurs in dogs. A comprehensive review of tooth resorption in dogs is beyond the scope of this article. In dogs, some types of tooth resorption are believed to be incidental findings (external replacement resorption), and others are associated with common dental conditions (external inflammatory resorption) (FIGURE 12). The characteristics of tooth resorption in dogs are described in BOX 4.
- Frequency of tooth resorption in dogs is 53.6%
- External replacement resorption and external inflammatory resorption are most common
- Incidence of external replacement resorption increases with age and body weight
- External inflammatory resorption is associated with periodontal disease, endodontic disease, or both, and increases with age
Carnassial Tooth Malformations
A developmental abnormality that affects mandibular first molar teeth in dogs has previously been referred to as dens invaginatus or dens in dente. A recent study found that this developmental abnormality was not consistent with the findings of dens invaginatus in humans, and the authors recommended that malformations in the mandibular and maxillary carnassial teeth be referred to as carnassial tooth malformations until further information is available.14
The malformed teeth have abnormal mineralized tissue surrounded by disorganized dentin within the teeth. Malformed crowns have defects in the enamel and dentin that can open communication between the pulp and oral cavity. The communication may not be clinically obvious, and the tooth may appear grossly normal. The fissures or defects in the tooth allow bacteria to travel to the pulp, resulting in endodontic disease. Common features of carnassial tooth malformations are described in BOX 5.
- Frequently bilateral
- Furcation abnormalities
- Abnormalities in coronal enamel
- Abnormal radiopacity within the crown
- Root convergence
- Periapical lucencies and periodontal disease
Accurate diagnosis and treatment of oral diseases require a complete intraoral examination under anesthesia, including periodontal probing and charting and full mouth radiographs. Teeth that appear clinically normal may have pathology that is detectable only on intraoral radiographs.
The more you learn about oral pathology, the more oral pathology you will recognize in your patients and the better you will treat them.
Author’s Note: Special thanks to the veterinary nurses who obtained these radiographs and are an integral part of the oral healthcare team.
- Farook FF, Aldowene H, Alharbi R, et al. Reliability assessment between clinical attachment loss and alveolar bone levels in dental radiographs. Clin Exp Dent Res. 2020;6(6):596-601. doi: 10.1002/cre2.324
- Lommer MJ, Verstraete FJ. Radiographic patterns of periodontitis in cats: 147 cases (1998–1999). JAVMA. 2001;218(2):230–234.
- Tsugawa AJ, Verstraete FJ, Kass PH, Gorrel C. Diagnostic value of the use of lateral and occlusal radiographic views in comparison with periodontal probing for the assessment of periodontal attachment of the canine teeth in dogs. Am J Vet Res. 2003;64(3):255–261.
- D’Astous J. Periodontology: an overview of alveolar bone expansion. Can Vet J. 2015;56(3):295–300.
- DuPont G, DeBowes L. Endodontic disease. In: Atlas of Dental Radiography in Dogs and Cats. Philadelphia, PA: WB Saunders Co.; 2009;142–171.
- Moore JI, Niemiec BA. Evaluation of extraction sites for evidence of retained roots and periapical pathology. JAAHA. 2014;50(2);77–82.
- Verstraete FJM, Kass PH, Terpak CH. Diagnostic value of full-mouth radiography in dogs. Am J Vet Res. 1998;59(6):686–691.
- Ng KK, Fiani N, Tennant M, Peralta S. Frequency of clinical and radiographic evidence of inflammation associated with retained tooth root fragments and the effects of tooth root fragment length and position on oral inflammation. JAVMA. 2020;256(6):687–695.
- Babbitt SG, Krakowski Volker M, Luskin IR. Incidence of radiographic cystic lesions associated with unerupted teeth in dogs. J Vet Dent. 2016;33(40):226–233.
- Bellei E, Ferro S, Zini E, Gracis M. A clinical, radiographic and histological study of unerupted teeth in dogs and cats: 73 cases (2001–2018). Front Vet Sci. 2019;6:357. doi: 10.3389/fvets.2019.00357
- Lommer MJ, Verstraete FJ. Prevalence of odontoclastic resorption lesions and periapical radiographic lucencies in cats: 265 cases (1995–1998). JAVMA. 2000;217(12):1866–1869.
- DuPont G, DeBowes L. Tooth resorption. In: Atlas of Dental Radiography in Dogs and Cats. Philadelphia, PA: WB Saunders Co.; 2009;172–181.
- Peralta S, Verstraete FJM, Kass PH. Radiographic evaluation of the types of tooth resorption in dogs. Am J Vet Res. 2010;71(7):784–793.
- Ng KK, Rine S, Choi E, et al. Mandibular carnassial tooth malformations in 6 dogs – micro-computed tomography and histology findings. Front Vet Sci. 2019;6;464. doi: 10.3389/fvets.2019.00464