Chapter 7 Endodontics

GENERAL COMMENTS

• The pulp is the innermost part of the tooth. The functional cells of the pulp are the odontoblasts, which produce dentin throughout the life of the tooth, creating a progressively thickened dentinal wall. Dental pulp consists of blood vessels and nerves that support the odontoblasts and provide internal sensory and metabolic function to the interior of the teeth.¹^–⁴

• The objective of endodontic therapy is to maintain a vital tooth or, failing that, to alleviate discomfort and infection from the tooth and periapical tissues by obliteration of the root canals.⁴^–⁹ It may also be considered preventive treatment in a patient without symptoms when a dead tooth is treated to prevent subsequent abscess, bone lysis, and possible infections and invasion into other areas. The ultimate goal is to salvage the tooth and, in doing so, the therapy should be as least invasive and remove as little structural tooth substance as is possible while returning the tooth to its former form and function.⁴

Standard of Care

• As stated in Chapter 1, the best prophylaxis for malpractice is good records. Records are the single most critical evidence that can be presented in court at any level, as confirmation of accurate diagnosis and proper treatment. A standard of care does not require perfection, but rather a reasonable degree of skill, knowledge, and competence exercised by doctors under similar circumstances. As the level of veterinary dentistry rises during the twenty-first century, it behooves general practitioners to either develop an increased level of dental skill or at least increase their knowledge to a point of being able to refer a case in need of treatment to an appropriate clinician. Today the locality rule, which provides for different standards in different communities, is becoming rapidly outdated. The trend today, because of advances in continuing education, nationally published literature, internet communication, and increased availability of transportation of patients, is to move toward state standards for generalists and to national standards for veterinary specialists, including those who are not but advertise themselves as such.

Justifications for Endodontic Therapy

• People often do not perceive that their pet is in pain when a tooth has been damaged. Animals often do not exhibit pain once pulp death has occurred ^4,^10,¹¹ until periapical pathology occurs.

• Shortly after pulp has become exposed in a fractured tooth, the exposed dentinal tubules become sealed by a smear layer of tooth debris, plaque, or dirt, making the patient more comfortable until a pulpal or periapical abscess occurs. Only initially, after a fracture, when the tubules are open and the pulp is exposed, does the patient exhibit signs of pain. The pain is a result of fluid pressure changes experienced either through open dentinal tubules or direct pulp exposure.¹²

Signs of Endodontic Pain ¹³

• Flinching when the tooth is percussed.

• Shearing or macerating food only on the side of the mouth opposite to the one with the injured tooth or teeth.

• Drooling on the injured side (pain causes increased salivation).

• Increased plaque and calculus on the injured side.

• Refusal of hard treats or chewing them only on the opposite side of the mouth.

• Sensitivity may be noticed during toothbrushing or oral palpation.

• Reluctance to accept or carry favorite objects.

• Temperament becomes more irritable, especially if the patient is handled about the mouth or sometimes even petted on the top of the head.

• Hunting dogs may refuse training dummies.

• Utility dogs may refuse their dumbbells.

• Apprehensive dogs may either hesitate to bite or bite and release repetitively.

• Loss of concentration or attention to task.

• Reduced sense of smell, due to nasal infection.

• Moaning, which might be mistaken for arthritis, when the animal stands up.

• Inexplicable circling toward the injured side.

Challenges of Endodontic Treatment

• To overcome potential lack of equipment, knowledge, or clinical experience.

• Requires a certain amount of inventoried supplies, equipment, continuing education, staff training, and client education.

Algorithm Outline for Endodontic Pathology

Following is an algorithm outline for endodontic treatment planning of teeth in which the pulp has been compromised.

Nonfractured Tooth

I. No visible, radiographic, or detectable change requires no treatment.

II. No visible change, but hypersensitivity of tooth.

B. Diagnostic tests: standard root canal therapy if pulp compromise is indicated by any of the following tests:

1. Radiographs: periapical lucency, internal pulp resorption, or root end resorption.

2. Percussion: hypersensitivity of the tooth in question, compared with adjacent teeth.

3. Transillumination: tooth is opaque when backlighted in a darkened room.

4. Pulp testing: hypersensitivity.

Fractured Tooth

• Basrani classification, which takes into account the extent of tooth damage).²

I. Class A1 (crown: enamel only).

A. Client elects no treatment: take radiographs in 6 months.

B. Client elects treatment: restore the defect and recheck, take radiograph in 9 to 12 months.

II. Class A2a (crown: enamel and dentin).

A. Client elects no treatment: take radiographs in 6 months.

B. Client elects treatment.

1. If sufficient dentin remains (>0.5 mm) between defect and pulp, place indirect pulp cap with restoration, and take a radiograph in 9 to 12 months.

2. If insufficient dentin remains (<0.5 mm) between defect and pulp, place pulp cap with restoration and take a radiograph in 9 to 12 months.

III. Class A2b (crown, enamel, dentin, and pulp exposed).

V. Class C (fracture involving both crown and root).

A. Extraction.

INDIRECT PULP CAPPING

General Comments

• Indirect pulp capping is indicated when a cavity or restorative preparation occurs within 1 to 2 mm of the pulp.

• During deep-decay cavity preparation, a layer of carious dentin can be left over the pulp. This layer will be sterilized with the application of calcium hydroxide, as shown by Aponte, Hartsook, and Camp in the 1960s (still valid information).¹⁴ Pulpitis of deep cavity preparation, secondary to chemical or thermal burns, can be partially prevented by application of cavity varnish, liners, or a base preparation to the tissue closest to the pulp.¹⁵ This is a highly controversial topic in human dentistry in which investigators found that even a double layer of Copalite did not prevent bacterial leakage and growth on cavity walls.¹⁶

Indications

• Deep-cavity preparations where the pink hue of pulp is seen shining through the dentin.

• Extensive crown restorations on vital teeth.

Objective

• A protective layer of calcium hydroxide or glass ionomer is placed, as a lining base, in a vital tooth as a covering, on the floor of a restorative preparation or cavity preparation close to the pulp tissue, to protect the pulp from thermal or chemical insult and to prevent sensitivity.

Technique

Step 1—The mechanically prepared cavity preparation or restoration site is irrigated with sterile saline to remove dentinal debris and is air dried (Fig. 7-1, A).

Fig. 7-1

Substep 1—A dentin tooth conditioner is applied to the dentinal surface with a Getz brush for the manufacturer’s recommended time, rinsed with water, and air dried (Fig. 7-1, B).

Substep 2—For deep-cavity preparations, it is desirable to use a calcium hydroxide and glass ionomer cavity liner. A minimum layer 1 mm deep should be placed. The calcium hydroxide should be placed first. The tooth conditioner can be used superficial to the calcium hydroxide product to prepare the dentinal walls for the glass ionomer. If possible, avoid getting the liner on the walls of the cavity coronally in the area of the final restoration.

Step 2—The cavity liner is applied to the fundus of the cavity or restorative preparation in a thin layer, using a Getz brush or plastic working instrument (Fig. 7-1, C), and is allowed to dry. Bonding of the final restoration will be inhibited if the liner coats the walls of the cavity preparation (Fig. 7-1, D). If the walls are coated inadvertently, they should be prepared again.

Substep 1—When using a light-cured glass ionomer liner, the material is cured with a visible light gun for the prescribed length of time (Fig. 7-1, E).

Step 3—In deep restorations, another layer of a glass ionomer can be placed to reduce the thickness of the final restoration (Fig. 7-1, F). This reduces the polymerization shrinkage that occurs as the restoration material cures.

Step 4—The restorative procedure is continued (Fig. 7-1, G), as described in Chapter 8.

Postoperative Care

• Follow-up radiographs at 6 and 12 months to evaluate pulp chamber size and evidence of apical abscess formation by comparison with other teeth.

INDIRECT PULP CAPPING: CROWN THERAPY

General Comments

• Due to rules about altering heritable anatomy in most dog show organizations, ceramic crown installation should not be performed on dogs intended to be entered in conformation-type dog shows.

• It is the best treatment to prevent further damage to the crown.

• A full-coverage crown (Fig. 7-2, A) or half-coverage crown (Fig. 7-2, B) may be placed to afford protection to the tooth to prevent chipping or further wear.

Fig. 7-2

Indications

• Teeth that have fractures that have not exposed the pulp chamber.

• Teeth that have had excessive wear from such activities as carrying or chewing tennis balls or chewing on hard objects.

Objective

• To prevent further trauma and wear.

• To regain grasping function in service, competitive obedience, hunting, or field trial dogs.

• Cosmetics in certain instances.

Materials and Technique

• See Chapter 8.

VITAL PULPOTOMY AND DIRECT PULP CAPPING

General Comment

• In patients younger than 18 months, it is frequently desirable to achieve additional dentin formation to increase the strength of a tooth that has been fractured. For recent fractures, vital pulpotomy with direct pulp capping is the treatment of choice. The technique will be the same, but the difference between a vital pulpotomy and a direct pulp cap is that in a direct pulp cap, a portion of healthy pulp is removed to make room for the restorative materials. In a vital pulpotomy, it is unhealthy pulp that is removed. A vital pulpotomy is also referred to as a partial coronal pulpectomy. Patients that have received this treatment should be monitored closely with radiographs to observe changes in pulp health. Root canal therapy is indicated if death of the pulp is evident on follow-up examination.

Indications

Vital Pulpotomy

• Fractured tooth crowns with pulp exposure of less than 2 weeks’ duration in patients younger than 18 months.

• Fractured tooth crowns with pulp exposure of less than 48 hours’ duration in patients older than 18 months.

Objective

• Protect the pulp by stimulating dentinal repair with secondary dentin by using calcium hydroxide, as an irritant, directly on the pulp tissue and placing a restoration over the pulp access site.

Technique

Step 1—The oral cavity, particularly the tooth to be treated, is disinfected with an antiseptic solution (0.12% chlorhexidine). Aseptic technique is used throughout the procedure. If a sterile delivery system is not built into the handpiece system, coolant can be delivered by an assistant using a sterile solution in a syringe sprayed on the site.

Step 2—A #701L cross-cut, tapered-fissure bur in a high-speed or low-speed handpiece with sterile physiological saline or sterile water cooling is used to amputate a tooth crown (Fig. 7-2, C) or hemisect a multirooted tooth (Fig. 7-2, D). (When disarming animals, the canine teeth are shortened to the level of the adjacent incisors) (Fig. 7-2, E). A 3/4-inch diameter double-sided diamond disc, with a disc guard to protect the adjacent soft tissue, is another option (Fig. 7-2, F).

Step 3—A bur approximately equal in size to the diameter of the pulp chamber (round, pear, or tapered-fissure) is used in a high-speed handpiece to remove the coronal portion of the pulp from the amputated tooth, removing 5 mm of the pulp from the remaining endodontic system (Fig. 7-3, A).

Fig. 7-3

Step 4—Hemostasis may be achieved using sterile saline lavage and the blunt end of multiple sterile, dry, paper points. Leaving a paper point in place for 2 to 3 minutes is often sufficient to control hemorrhage. In cases with persistent hemorrhage, lavage with a local anesthetic solution containing epinephrine ¹⁷ or 20% ferric sulfate (Viscostat, Pulpdent) can be used. Caution should be used if employing a halothane (Fluothane) anesthetic agent. If hemorrhage continues, the coronal portion of the canal should be inspected to be sure all pulp tissue coronal to the area cleaned out in step 3 has been removed. Any filaments of inflamed pulp left may cause continued bleeding.^14,^17,¹⁸ Excessive hemorrhage at an exposure site or during the procedure indicates severe inflammation, and treatment adjustment should be considered, either changing the therapy to pulpectomy or to extraction.¹⁴ A coating of calcium hydroxide powder on the paper point may also help control hemorrhage (Fig. 7-3, B).

Step 5—When bleeding is controlled, calcium hydroxide paste is applied over the exposed pulp for a depth of 1 to 2 mm using the applicator syringe provided (Fig. 7-3, C). The paste is tamped against the pulp stump with the blunt end of a sterile paper point. If using a calcium hydroxide powder, a sterile retrograde amalgam carrier can be used to gently place a layer of powder against the pulp. More recently mineral trioxide aggregate (MTA) (ProRoot, Dentsply Tulsa Dental, Tulsa, Okla.) has been advocated because of its retention and resistance to leakage. MTA is a compound somewhat similar to Portland cement. It is mixed with water or physiologic saline and applied directly to the pulp with an amalgam plugger or other suitable instrument. It has been used successfully and is recommended by the manufacturer for use in vital pulpotomies, direct pulp caps, and retrograde root canal therapy.

Step 6—An intermediate filling material, such as glass ionomer, is placed over the calcium hydroxide paste (or MTA) with an injection syringe or jiffy tube and is allowed to cure (Fig. 7-3, D).

Step 7—The pulpal access (cavity) opening is prepared (Fig. 7-3, E) for the desired filling material, and the restoration is completed (Fig. 7-3, F).

Postsurgical Care

• Postoperative antibiotics should be administered for 7 days.

• Radiographic follow-up at 6 months and 12 months, or at appropriate intervals, is necessary to detect pulp death and subsequent apical changes indicating the need for root canal therapy. (Compare with contralateral tooth.)

DIRECT PULP CAPPING WITH DENTAL ADHESIVES

• Dentin adhesive.

• Unfilled and filled light-cured resin.

• Light-cure gun.

Technique

The coronal portion of the tooth is prepared as in the preceding section. Hemostasis is obtained, and this technique begins after step 5.

Step 6—Provisionally cover the exposed pulp with a calcium hydroxide paste with a sterile materials application syringe. This material is applied to protect the pulp during the next step and must not be skipped.

Step 7—A 37% phosphoric acid gel (contained in the composite resin kit) is applied for 20 seconds.

Step 8—After 20 seconds, the gel is wiped onto the enamel for a brief 10 seconds and then rinsed off with sterile saline.

Step 9—The area is blotted dry.

Step 10—The entire preparation, including enamel, dentin, and pulp tissue, is treated with the dentinal primer for approximately 5 seconds, followed by 5 seconds of air drying.

Step 11—A light-cured unfilled resin is applied and activated.

Step 12—The filled resin is applied.

• See Chapter 8 for further information on composite dental restoration.

Complications

• A dead tooth may result from any vital pulp capping procedure.

• The risks should be explained to the client before treatment: (1) the tooth injury may be older or more severe than it was thought to be, (2) the undetectable overwhelming infectious organisms might have contaminated the pulp, and (3) the patient may further insult and injure the tooth with inappropriate oral behavior.

APEXIFICATION, APEXOGENESIS, HARD TISSUE FORMATION

General Comments

• Apexification is the process of stimulating the formation of a closed apex with hard tissue when a necrotic pulp is present in an incompletely developed young permanent tooth, whether delayed by infectious or noninfectious process.

• Apexogenesis describes the completion of normal developmental root lengthening in young, permanent vital teeth.

• Typically a pulp canal is cleaned and filled with a temporary paste to stimulate the formation of calcified tissue at the apex.¹⁴ Calcium hydroxide paste is the traditional medicament and may require intermittent replacement during the healing period if there is no radiographic evidence of hard tissue formation. After radiographic evidence of apical closure is seen, the temporary filling material is removed and a standard root canal procedure performed with gutta-percha.

• Hard tissue formation is usually seen in 3 to 6 months.

• Length of time to apexification has not been documented in dogs but can take 6 to 24 months in humans.^14,¹⁹ Osteoid or cementoid is the calcified material that forms over the apical foramen secondary to this process, as identified by investigators.²⁰^–²² The treatment is a definite challenge, both in technique and in achieving recall compliance with clients. The prognosis is guarded in immature animals due to the fragility of the thin tooth wall that is subject to fracture upon minimal trauma.

Step 3—A small file is placed in the canal to the approximate apical limit, and the tooth is radiographed again to determine a working length of the files, optimally to within 2 mm short of the apex, thus preventing injury to the periapical or apical tissues (Fig. 7-4, A).

Fig. 7-4

Step 4—The root canal is filed and shaped in a standard manner (described in the section Cleaning and Shaping the Canal), using only sterile water or saline for irrigation (Fig. 7-4, B).

Step 5—The canal is dried, using the blunt end of sterile paper points (to avoid perforation into the apex) (Fig. 7-4, C).

Step 6—The canal is filled with calcium hydroxide paste, using a spiral filler with a stop at the working length (Fig. 7-4, D) or a sterile needle with an endodontic syringe.

Step 7—The calcium hydroxide paste is forced to the apex by placing a cotton pellet over the paste and using a blunt plugger to condense it apically (Fig. 7-4, E). The cotton pellet is removed with an endodontic file or broach.

Step 8—The calcium hydroxide paste is removed 3 mm from the access area, and a fast-setting base is placed over the paste (Fig. 7-4, F).

Step 9—A restoration is placed according to standard techniques.

Postoperative Care

• Follow-up radiographs are taken every 3 months to evaluate apical closure or root healing.

• When the desired hard tissue formation or apical closure is seen, the calcium hydroxide paste is removed, the canal is irrigated with sterile saline, and the canal is dried. Obturation can be completed using a technique to fill a larger canal adequately (chloropercha, inverted cone, or thermoplasticized gutta-percha technique).

NONSURGICAL ROOT CANAL THERAPY: STANDARD, NORMOGRADE, and PULPECTOMY

General Comments

• When the tooth pulp has been traumatized, the pathogenesis culminates in apical root end resorption and abscess formation in the surrounding osseous tissue.²³^–²⁵

• The theory of standard root canal therapy is that if the source of the infection (the root canal) is cleaned, the body will eliminate any residual escaped periapical infection.

• Bacterial pulpal infection can occur in an intact tooth. When a systemic infection occurs, microorganisms can ascend through the apical delta to contaminate the pulp canal (anachoresis).

• Patients requiring root canal therapy may exhibit a variety of signs.

• Patients may be asymptomatic.^26,²⁷

• Patients may show signs such as fever, localized facial edema, a draining tract out of the skin or orally, drooling, reduced biting pressure (some trainers report attack dogs bite and release as they bite—typewriting), or reluctance to eat (they may pick up food, start to chew, and then drop the food). Other clients report patients licking in the air, circling, or displaying other stress patterns. Trained tracking dogs or dogs used for their sense of smell may lose their ability to perform their tasks; other service dogs may lose their concentration.

Objective

• To remove diseased or necrotic pulp tissue and achieve a hermetic seal at the apex to preserve a tooth. Root canal therapy consists of three basic procedures: (1) accessing the pulp canal, (2) cleaning and shaping the canal, and (3) obturating (filling) the canal. Each of these procedures will be covered as for a preparatory treatment, before restoring the tooth surface (see Chapter 8). Following are guidelines to adapt these general principles to individual tooth types.

• To create a cornucopia-shaped convenience form that is widest at the access site and permits shaping the access to the width of the pulp chamber, so that there are no overhangs of the root canal roof and the coronal walls to deflect the instruments during preparation.

Technique

Step 1—A preoperative radiograph is taken to identify landmarks, to evaluate canal size and position, and to confirm the treatment plan.

Step 2—Evaluate the tooth clinically to determine root angulation, cusp position, and surface anatomy to help determine appropriate position and angulation of the access site. (Access in specific teeth is outlined later in this chapter under specific tooth types.)

Step 3—The oral cavity is disinfected with 0.2% chlorhexidine solution.

Step 4—Using the desired cutting bur, a hole is drilled through the enamel layer with the bur positioned perpendicular to the tooth surface, so as to minimize “wandering” of the bur tip. This step is eliminated if an open fracture site allows straight-line access to the apex (Fig. 7-6, A).

Fig. 7-6

Step 5—Once the enamel has been perforated, the bur is repositioned and aligned parallel with the root canal, and the access site continues to be developed (Fig. 7-6, B).

Step 6—The access site is deepened until the pulp chamber is entered. When using a high-speed handpiece, a reduced resistance and a higher pitched drilling noise are noted when the pulp chamber is penetrated (Fig. 7-6, C).

Step 7—The access can be enlarged, using a #701L bur or Gates Glidden reamer, and shaped to expose the entire width of the pulp chamber, removing ledges so as to appropriately accommodate the endodontic files that will be introduced to debride the root canal (Fig. 7-6, D).

Step 1—Length determination. A small-diameter endodontic file (usually size 10, but 06 and 08 sizes are available) with preplaced endodontic stop is inserted into the root canal 2 mm short of the estimated canal length, as determined from a preoperative radiograph (Fig. 7-7, A).

Fig. 7-7

Step 2—Radiograph. A radiograph is taken to verify the file depth (how far the file has penetrated) and the working length (how far the file should penetrate). This apical stop indicates that the pulp canal does not extend beyond the file. The ideal working length is 1 mm short of the apex. The canal usually needs to be instrumented further, and the file may be inserted farther and additional radiographs taken until the working length is achieved. Once the working length is achieved, the endodontic stop is moved down the shaft of the file until it contacts the crown, with the file fully inserted. The length is noted (Fig. 7-7, B) and recorded. To provide consistency as to the measurement, the stop should be perpendicular to the file.

• In small canals, the liberal use of a chelating agent (RC Prep) alternated with sodium hypochlorite may help open up the canal, by softening the necrotic dentin, to allow more complete debridement and access for smaller pathfinder files.

• Subsequent files are fitted with endodontic stops at the predetermined file length (Fig. 7-7, C). If the file is not close to the desired depth, it is instrumented further, and a repeat radiograph is taken until the correct length is achieved. Canal preparation should not be considered complete until the master apical file is at least size 25. This will then permit size 15 to 20 filling materials, lightly buttered with sealer, to reach the apex of the canal.²⁹

Only gold members can continue reading. Log In or Register to continue

Stay updated, free articles. Join our Telegram channel

Tags: Veterinary Dental Techniques for the Small Animal Practitioner

Sep 22, 2016 | Posted by admin in SMALL ANIMAL | Comments Off

Fastest Veterinary Medicine Insight Engine

Endodontics

Share this:

Related

Related posts:

Stay updated, free articles. Join our Telegram channel

Full access? Get Clinical Tree