Managing fractured and worn teeth (Proceedings)

A variety of dental lesions can occur as a result of chronic wear or acute trauma including severe dental attrition, fractured teeth, subluxated teeth, avulsed teeth and jaw fractures. The management of these lesions and injuries can be a diagnostic and therapeutic challenge. Proper management of these lesions and injuries can be a rewarding part of veterinary practice.

Dental Wear

Dental wear can be divided into two categories, attrition and abrasion. Dental attrition is the gradual and regular loss of tooth substance resulting from normal mastication. Excessive wear caused by malocclusion resulting in tooth-to-tooth contact is called pathologic attrition. Dental abrasion is the mechanical wear of teeth caused by mechanical wear other than by normal mastication or tooth-to-tooth contact such as wear caused by chewing rocks, cage bars, or wire. In cases of dental attrition the pulp responds to rapid wear by laying down tertiary or reparative dentin, which is visible as a dark brown spot on the affected tooth. The dark brown spot is solid and cannot be entered with a dental explorer. No therapy is usually required in these cases. Occasionally, very rapid dental attrition can result in pulpal exposure. These cases require endodontic therapy or extraction.

Cage-biter syndrome, a form of dental abrasion, can be seen in dogs who chronically chew on their cage bars. The unique pattern of dental wear associated with cage-biter syndrome includes dental wear on the distal aspect of the canine teeth. Dogs affected by severe wear on the distal aspect of their canine teeth may be affected with dentinal hypersensitivity, endodontic disease, and crown weakening resulting in dental fractures. Dental radiographs should be taken of teeth affected with cage-biter syndrome to help rule out the presence of endodontic disease. If endodontic disease is present affected teeth should be endodontically treated or extracted. Full or three-quarter prosthetic crowns can be placed on teeth affected with cage-biter syndrome. A three-quarter prosthetic crown is preferred in teeth that are not endodontically treated so that if endodontic treatment is required at a later date the ideal access site can be easily created without damaging the prosthetic crown.

Fractured Teeth

Fractured teeth usually result from external trauma. In cats, the tooth most frequently fractured because of trauma is the canine tooth. Fractured canine teeth in cats often result in pulpal exposure because of the extension of the pulp canal into the coronal tip of the canine tooth in felines. Pulpal exposure is confirmed if a fine dental explorer penetrates into the canal. The teeth most frequently fractured in the dog are the canine teeth, incisors, and the maxillary fourth premolars, however, any tooth may be fractured. Following pulpal exposure the following sequence of events may occur:

• Pulpal exposure → Bacterial pulpitis → Pulp necrosis → Apical granuloma → Periapical abscess → Acute alveolar periodontitis → Osteomyelitis → Sepsis

Radiographic evidence of chronic endodontic disease or pulpal necrosis include:

• Periapical lysis

• Apical lysis

• Large asymmetrical endodontic systems when compared to contralateral teeth

• Radiographic loss of tooth structure to the pulp chamber

• Secondary destruction of periodontal structures

• Gutta-percha point placed in draining tract pointing to apex of affected tooth

Fractured teeth should be endodontically treated or extracted. In cases of endodontically treated posterior teeth such as the upper fourth premolar or the lower first molar recommendations should be made to place a full crown on the treated tooth to help prevent refracturing of the tooth since nonvital teeth are more brittle than vital teeth and posterior teeth sustain tremendous amounts of force during mastication.

Several different endodontic procedures may be utilized to treat endodontically diseased teeth these techniques include: vital pulpotomy, conventional and surgical endodontic therapy. Whenever pulp disease is present it is important to decide which type of endodontic therapy is most appropriate based on the patient's age, time of exposure, and the gross anatomic features and vitality of the tooth. The most common and most successful type of endodontic therapy is conventional or nonsurgical endodontic therapy. Occasionally vital pulpotomy with direct pulp capping is recommended and rarely surgical or nonconventional root canal therapy is indicated.

A vital pulpotomy with direct pulp capping is indicated in vital teeth with traumatic pulpal exposure of less than 8 hours. This permissible exposure time may be extended to up to 2 weeks in very young animals with immature teeth. It is also indicated in crown shortening procedures as an alternative to conventional endodontic therapy in the treatment of mature permanent teeth. Ideally, vital techniques such as vital pulpotomy with direct pulp capping should be limited to use in incompletely developed permanent teeth with pulpal exposure. A vital pulpotomy with direct pulp capping in an animal less than 18 months of age will permit the tooth to remain vital at least temporarily so that additional dentin can be formed resulting in an increase in strength of the tooth that has been fractured. Additionally, it can allow the formation of the apex of a very immature tooth.

A pulpotomy with direct pulp capping should never be performed in nonvital teeth, when the pulpal exposure is prolonged and in teeth in which the pulp is severely traumatized or grossly contaminated. In fact, it is best to limit vital pulpotomy procedures to immature teeth with recent exposure and teeth requiring crown reduction procedures.

The objective of a vital pulpotomy with direct pulp capping is to protect the pulp following pulpal exposure by stimulating formation of secondary dentin over the pulpal tissue and covering over the access site with a restorative material.

The steps involved in the performance of a vital pulpotomy with direct pulp capping are listed below: (1) Preoperative radiograph of the affected tooth and the contralateral tooth. (2) Disinfection of the tooth with 0.2% chlorhexidine solution. (3) An appropriately sized sterile diamond pear-shaped bur on a high speed handpiece is used to remove the coronal portion of the pulp. (4) The remaining pulp is gently flushed with sterile saline and the blunt end of paper points are used to achieve hemostasis. (5) A layer of MTA (a new pulp capping material) is gently placed over the pulp. (6) An intermediate layer of glass-ionomer is placed over the MTA. (7) A composite material is used to fill the access site.

Postoperative care for animals following a vital pulpotomy with direct pulp capping includes antibiotic therapy for 1 week postoperatively. Owners should be informed that a vital pulpotomy with direct pulp capping may necessitate conventional endodontic therapy in the future if pulpitis and pulpal necrosis develops. The patient should be monitored for clinical signs associated with endodontic disease. Oral examination by the owner and veterinarian may reveal problems associated with a failed vital pulpotomy with direct pulp capping including: discolored teeth, soft tissue fistulas, teeth that are painful on percussion or lost restorations. Dental radiographs should be taken at 6 and 12 month intervals postoperatively and then annually during regular dental appointments. Radiographic findings indicative of pulpal necrosis include: periapical or apical lysis, failure of symmetrical dentin deposition compared to the contralateral normal tooth and endodontic resorption. Radiographic findings consistent with pulpal necrosis necessitate the performance of conventional endodontic therapy or extraction of the affected tooth.

Conventional endodontic therapy or nonsurgical endodontic therapy is performed through the crown of the tooth and is the most frequently performed endodontic therapy. This procedure is indicated whenever there is pulpal death of a tooth secondary to inflammation, infection or trauma. The purpose of root canal therapy is to preserve the function of the tooth while preventing it from causing adverse effects because of its presence. This is achieved by removing the necrotic or infected pulp and filling the pulp canal with an inert material. A properly performed root canal procedure will prevent infection or inflammatory products from extending from the tooth into the tissues that surround the apex of the tooth. There are several basic steps involved in performing conventional endodontic therapy. These steps include: (1) preparation, (2) access, (3) debridement, (4) drying, (5) filling, and (6) restoration.

Surgical endodontics or nonconventional endodontic therapy refers to the application of endodontic therapy with an approach through soft tissue and bone rather than through the crown of the tooth. Surgical endodontic therapy is always performed in conjunction with nonsurgical or conventional endodontic therapy. Surgical endodontics is not a substitute for good nonsurgical endodontic therapy. The long-term success rate with surgical endodontics has not been shown to be superior to nonsurgical endodontic therapy. A properly prepared and obturated root canal can be adequately sealed with conventional endodontic therapy in most cases.

Subluxated and Avulsed Teeth

Tooth luxations are the displacement or partial displacement of teeth from their alveoli. Dental avulsions are the loss of teeth from their alveoli. Teeth accidentally avulsed or luxated from their alveoli by trauma should be reimplanted or repositioned as soon as possible, ideally within 30 minutes. Teeth that are luxated or avulsed because of advanced periodontal should not be reimplanted. Until reimplantation of traumatically avulsed teeth is possible, affected teeth may be briefly stored in saliva or milk. Following reimplantation the tooth is held in position with a figure-of-eight wire and an interdental splint. The prognosis for luxated teeth is better than avulsed teeth because of less damage to the periodontal tissues. Endodontic therapy is recommended 2 weeks after correction of luxations and avulsions. In addition, these teeth should be stabilized with an interdental splint for approximately 6 weeks.