External Tooth Resorption in Cats, Part 2: Therapeutic Approaches
Jan Bellows, DVM, Diplomate AVDC & ABVP (Canine & Feline)
All Pets Dental, Weston, Florida
Tooth resorption in cats is prevalent, affecting 28% to 68% of mature cats, depending on the population researched.1 One study found histologic evidence of resorption in all teeth among cats with at least one resorptive lesion; this led to the hypothesis that given enough time, all teeth of affected cats will develop tooth resorption.2
External tooth resorption, or root resorption, is the breakdown or destruction and subsequent loss of the root structure of a tooth, while internal root resorption occurs when the integrity of the outermost layer of pulp tissue is broached. In feline patients, external root resorption is far more common than internal root resorption.3
Whether the clinician identifies tooth resorption clinically or by radiography (see Classifying Tooth Resorption by Anatomy & Radiographic Appearance), treatment options can be confusing. Fortunately, solid evidence-based concepts can guide the practitioner toward 2 treatment options:3
- Crown amputation followed by gingival closure
Other therapeutic options—the merits of which are discussed in this article—include monitoring, tooth restoration, and crown/root atomization.
Read the first article of this 2-part series—External Tooth Resorption in Cats, Part 1: Pathogenesis, Classification, & Diagnosis—published in the January/February 2016 issue of Today’s Veterinary Practice at tvpjournal.com.
TOOTH RESTORATION: An Outdated Remedy
Before tooth resorption in cats was differentiated from caries (cavities) in humans, restoration with glass ionomer cement was the treatment of choice. At first glance, it would appear that filling the defect with a substance that bonds to dentin and releases pain-relieving fluoride made sense.4 However, this therapy does not resolve disease because the lesion commonly begins just below the cementoenamel junction and undermines dentin, exposing crown enamel. Filling the lesion only cosmetically treats the surface defect.
WATCHFUL WAITING: A Conservative Approach
Conservative management of nonpainful external root resorption may be chosen when the lesion is confined to the root and has not extended into the pulp chamber, root canal, or exposed oral cavity. This approach requires semi-annual monitoring, at minimum, because resorptive lesions are considered progressive; monitoring includes intraoral radiography and clinical examination.5
TR 5 features no clinically recognized inflammation of the gingiva, and only wisps of dental hard tissue are seen radiographically. This stage of resorption can be managed conservatively, with follow-up radiographs obtained at the time of future professional oral hygiene visits (Figure 1).
Classifying Tooth Resorption by Anatomy & Radiographic Appearance
The American Veterinary Dental College (avdc.org) has adopted stage and type classifications for tooth resorption. These classifications help practitioners categorize lesions both anatomically for record keeping (Table 1 and Figure A) and radiographically for treatment decisions (Table 2).6
CROWN/ROOT ATOMIZATION: Not Recommended
Crown and/or root atomization is not recommended as a therapy option for tooth resorption. Root atomization is performed using a round bur on a water-cooled, high-speed handpiece that blindly eliminates root fragments. This procedure is fraught with potential iatrogenic negative outcomes, including nasal cavity, mandibular, or infraorbital canal perforation; sublingual soft tissue trauma; and subcutaneous emphysema.
EXTRACTION: Treatment of Choice for T1 & T3
Extraction is the treatment of choice for tooth resorption involving teeth with roots that have not been replaced by the surrounding bone (T1 and T3). Proper extraction removes painful dentin exposure and eliminates the route for bacteria to enter into the root canal.
It is important to understand the dental hard tissue anatomy above and below the gingiva. In cats:
- Canines, incisors, and often maxillary second premolars are single-rooted.
- Maxillary first molars, even though anatomically double- or triple-rooted, can be treated as single-rooted due to root fusion.
- The maxillary fourth premolar has 3 roots.
- All remaining premolars and mandibular first molars have 2 roots.7
See Extraction: What You Will Need.
- Intubate and stabilize the patient under anesthesia.
- Prepare the oral cavity by rinsing with 0.12% chlorhexidine gluconate, scaling and polishing the visible teeth, and then rinsing again. Chlorhexidine gluconate helps reduce bacterial exposure to the patient and veterinary team.
- Expose full intraoral survey radiographs and examine them to evaluate crown and root morphology.
- Provide local nerve block anesthesia before making any incisions.7
Extraction: What You Will Need
- Disposable #11 or #15 scalpel blade and #3 handle
- Periosteal (Freer and Molt #2) elevator to reflect and retract periosteum from bone surface
- Curved Iris scissors, 11 cm
- Winged elevators (1–5 mm), sharpened before, and often during, the procedure
- Castroviejo needle holder to allow controlled suturing of delicate flaps
- Miller surgical bone curette #10 (EX2, cislak.com)
- Bishop-Harmon tissue forceps
- #6 India sharpening stone (autoclavable)
- Monocryl (ethicon .com) or chromic gut 5-0 suture with P-3 needle
1. Make the initial vertical incision rostrally 1 to 2 mm coronal to the mucogingival junction. One mesial releasing incision is preferred to prevent interruption of the distal blood supply. Place the incision in the attached gingiva to help preserve the blood supply during and after surgery (Figure 2).
2. Angle the blade tip toward the root, incising 360 degrees into the pocket or sulcus.
3. Use a freshly sharpened periosteal elevator (#2 Molt preferred) to expose the alveolar bone by freeing the attached gingiva and alveolar mucosa past the mucogingival junction (Figure 3).
4. Use a #1 or #2 carbide round bur on a water-cooled, high-speed handpiece to remove the coronal half to three quarters of the buccal alveolar plate from the tooth root. Occasionally, radiographs reveal a bulbous root apex, which requires additional widening of the overlying alveolus (Figure 4).
5. Section multi-rooted teeth into single-rooted crown-root segments using a cross-cut fissure or small #1 round bur. Begin the sectioning at the furcation and carry it coronally until the tooth is split into single-rooted segments. When extracting mandibular teeth, note that the mandibular canal lies immediately beneath the cheek tooth apices. Marked hemorrhage and damage to the mandibular nerve may occur when the mandibular canal is entered. Digital pressure and closure of the gingival defect can usually control excessive hemorrhage.
6. If needed, use a winged elevator to stretch the periodontal ligament and gently elevate the tooth root from the alveolus. Introduce the blade between the root and alveolus, and maintain each movement of rotation for at least 10 seconds. The tooth or segments can usually be delivered from the alveolus with the operator’s fingers or through gentle torsion with extraction forceps. If the root fractures during the extraction procedure, create a trench around the root fragment with a 701L cross-cut taper fissure or round bur to provide a purchase area for a dental elevator or root-tip pick (Figure 5).
7. After extraction, contour the remaining rough edges of alveolar bone and smooth them with a round bur placed in a water-cooled, high-speed handpiece (Figure 6).
8. Expose and examine a radiograph to confirm extraction.
9. Use a bone curette to clean out alveolar socket debris.
10. Suture the gingiva without tension (Figure 7).
CROWN AMPUTATION: Treatment of Choice for T2
In T2 root replacement resorption, bone- and cementum-like tissue replaces the periodontal ligament, dentin, and pulp. In these cases, crown amputation with intentional partial root retention, followed by gingival closure, is the treatment of choice because the root is already resorbing and considered nonpainful to the cat.
This procedure should be done only after evaluation of intraoral radiographs to confirm that extraction of the entire root is not possible (Figure 8), as evidenced by a marked decrease in root opacity and absence of the periodontal ligament space.8
Contraindications for this procedure include:
- Periodontal disease, as shown by horizontal or vertical bone loss
- Endodontic disease
- Positive retroviral status.9
Step-by-Step: Crown Amputation with Intentional Partial Root Retention & Gingival Closure
1. Follow the preparation outlined under Initial Steps.
2. Create a triangular flap—see Periodontal (Gingival) Flap Creation—with 2 vertical releasing incisions labially or buccally by initially making a vertical incision several millimeters interproximally mesial and distal to the affected tooth (Figure 9).
3. Use a fine periosteal elevator to expose the cementoenamel junction and alveolar margin (Figure 10).
4. Incise vertically into the periodontal ligament space, through the sulcus, 360 degrees around the tooth.
5. Remove the exposed crown and 1 to 2 mm of the coronal root apical to the alveolar margin using a #2 sterile or cross-cut fissure bur on a high-speed, water-irrigated handpiece (Figure 11).
6. Remove sharp alveolar margin projections with a round bur (Figure 12).
7. Suture the surgical site with 4-0 or 5-0 absorbable sutures (Figure 13).
8. Perform radiography on operative area to document the postoperative result (Figure 14).
Periodontal (Gingival) Flap Creation
Tooth extraction and crown amputation with gingival closure require removal of several millimeters of the coronal buccal alveolar bone underlying the attached gingiva, which is accomplished through periodontal flap exposure.
- Expose the alveolar bone and underlying root surface
- Preserve attached gingiva
- Allow suturing in a fashion that reduces the periodontal pocket and promotes reattachment of soft tissue to the root surface
- Include a pedicle, with a base that maintains attachment and circulation.
Flap design should:
- Allow maximum use and retention of keratinized gingival tissue
- Be long enough to permit full evaluation of the root surface not covered with bone
- Create a flap base 1.5 times as wide as the coronal aspect to allow adequate vascularity. Tissue tags should be removed to allow rapid healing and prevent formation of undesired granulation tissue.
Full thickness flaps:
- Are used to gain visibility and access for osseous surgery, root planing, and pocket elimination; in both tooth extraction and crown amputation with gingival closure procedures, these flaps include the periosteum
- Can be elevated by blunt dissection using a periosteal elevator in a rocking motion until the periosteum is peeled away from the underlying bone
- Include flap closure sutures that are placed tension-free from moveable to nonmovable tissue when possible, with surgical knots not on the incision line.
Triangular flap design for extraction (figure):
- A pedicle flap is created with 2 vertical releasing incisions extending past the mucogingival line.
- This flap should include the papilla, which is incorporated in the mesial or distal extent of the incision to make repositioning and suturing easier.
Triangular flap design for crown amputation:
- A triangular flap is raised, extending apically to the point needed to allow gingival closure without tension.
- A second vertical releasing incision can be made to allow greater exposure.
When a tooth fractures during the extraction process, the root fragment can usually be retrieved after removal of more alveolar bone and elevation with a small root-tip pick elevator. Avoid displacement of root fragment(s) into the mandibular or infraorbital canal, nasal cavity, or maxillary sinus. In cases of oropharyngeal inflammation, it is essential that no root fragment remains. If a root fragment is left in place, inform the owner and arrange radiographic follow-up.
The patient’s diet should be softened for at least 1 week after surgery. This can be accomplished by instructing the client to wet the animal’s food for about 20 minutes before feeding, allowing it to soften. A 0.12% chlorhexidine solution can be sent home with the owner for twice daily application as an oral rinse for 1 week.
External Tooth Resorption Treatment Concepts
- If the radiographic lesion appears small and confined to the tooth root, it may be monitored or extracted. Because tooth resorption is considered progressive, careful clinical and radiographic monitoring of these teeth at least every 6 months can be chosen as an alternative to immediate extraction.
- When the lesion is clinically evident and T1 or T3 radiographic lesions are present, flap exposure and extraction are indicated.
- When there is extensive T1 or T3 root resorption, flap exposure and extraction are indicated.
- When T2 tooth resorption is present, flap exposure of the proximal root and crown amputation followed by gingival closure are indicated.
- Mestrinho LA, Runhau J, Bragança M, Niza MM. Risk assessment of feline tooth resorption: A Portuguese clinical case control study. J Vet Dent 2013; 30(2):78-83.
- Lommer MJ, Verstraete FJM. Prevalence of odontoclastic resorption lesions and periapical radiographic lucencies in cats: 265 cases (1995–1998). JAVMA 2000; 217(12):1866-1869.
- Gorrel C. Tooth resorption in cats: Pathophysiology and treatment options. J Feline Med Surg 2015; 17(1):37-43.
- American Veterinary Dental College. AVDC Nomenclature Committee. avdc.org/nomenclature.
- Zetner K, Steurer I. Long-term results of restoration of feline resorptive lesions with micro-glass-composite. J Vet Dent 1995; 12(1):15-17.
- Gorrel C, Larsson Å. Feline odontoclastic resorptive lesions: Unveiling the early lesion. J Small Anim Pract 2002; 43(11):482-488.
- Reiter A, Soltero-Rivera MM. Applied feline oral anatomy and tooth extraction techniques: An illustrated guide. J Feline Med Surg 2014; 16(11):900-913.
- Dupont G. Crown amputation with intentional root retention for advanced feline resorptive lesions—a clinical study. J Vet Dent 1995; 12(1):9-13.
- Dupont GA. Crown amputation with intentional root retention for dental resorptive lesions in cats. J Vet Dent 2002; 19(2):107-110.