Crown Fracture – Complicated

Image: Fractured tooth.
Image: Fractured tooth with pulp exposed.

A complicated crown fracture is defined as an enamel/dentin fracture with pulp exposure. Clinical and radiographic examination reveals a loss of tooth structure with pulpal involvement. As with the non-complicated tooth fracture, the injured lips, tongue and gingival should be examined for tooth fragments and debris. Radiographic examination consists of periapical and occlusal radiographs of the injured teeth and of the injured soft tissues to rule out foreign body contamination. Pulp sensibility testing is not indicated initially since pulpal involvement is confirmed by sight. Subsequent monitoring is recommended.

Treatment objectives are to maintain pulp vitality and restore normal esthetics and function. The type of treatment rendered is dependent on pulp vitality and the stage of root development or resorption.

  • Primary teeth: If the root is in the process of resorbing, the suggested treatment is extraction. If the pulp tissue is vital, a pulpotomy is performed. Pulp capping is not a recommended procedure for primary teeth. If the pulp is non vital and the root structure is intact, a pulpectomy is performed. Follow up treatment consists of a clinical examination after one week and a radiographic examination at six to eight weeks and one year intervals.

  • Permanent teeth: Pulpal treatment is dependent upon the time elapsed since injury, size of the exposure and root development.

    • A tooth with either an open or closed apex may be treated with a pulp capping technique if the tooth is treated within four hours of the injury and the size of the exposure is pinpointed. The tooth is isolated with a rubber dam and decontaminated with chlorhexidine. A layer of calcium hydroxide paste is placed over the pulp exposure and the tooth is restored with a composite restoration.

    • In a tooth with an open (immature) apex with a pulp that has been exposed for an extended period of time (>4 hours) and/or the exposure is greater than 1mm, and the pulp is vital, a Cvek pulpotomy (apexogenesis) is performed. The tooth is isolated and decontaminated with chlorhexidine. The contaminated pulpal tissue is removed, using a round carbide bur or diamond mounted in a high speed handpiece using copious amounts of water. The pulp is removed to a depth of 2-3mm past the level of the exposure. Once complete hemostasis is achieved, a thin layer of calcium hydroxide paste or mineral trioxide aggregate (MTA) is applied to the wound and gently compressed. A thin layer of glass ionomer cement is placed over the dressing within the preparation and the tooth restored with composite resin. Follow up treatment consists of a clinical examination after one week, a radiographic examination at six to eight weeks and one year intervals to check for hard tissue barrier formation and continued root development.

    • A tooth with an open (immature) apex and non vital pulp requires extirpation of the entire infected pulp. The canal is prepared to within 1mm short of the radiographic apex. The canal is irrigated thoroughly with sodium hypochlorite (1% NaOCl) to dissolve pulp tissue remnants and to disinfect the canal. A calcium hydroxide paste is inserted into the canal with mild pressure using a cotton pellet and gutta percha point, taking care not to extend beyond the apex. Glass ionomer cement or zinc oxide eugenol is placed as a temporary dressing. The calcium hydroxide paste is replaced at three month intervals until a calcific bridge is formed at which time conventional endodontic treatment may be commenced.

    • Injured teeth with completed root development should undergo complete pulp extirpation and root canal therapy.

The disadvantages of calcium hydroxide apexification are that it requires multiple visits over 9-20 months. Even when successful, results in shortened roots with thin walls increase the likelihood of root fracture.

If a calcific bridge does not form in a timely manner or expedited treatment is desired, an alternative method is to use mineral trioxide aggregate (MTA) to “plug” the apical foramen. The technique is to remove the calcium hydroxide after three weeks and irrigate the canal with saline or sodium hypochlorite. Small increments of MTA are placed into the canal until a 4mm thickness is obtained. To allow setting of the MTA (4-6 hours), a moistened cotton pellet is sealed in the canal with a temporary filling material. At the next visit, the cotton pellet and temporary filling material are removed and the remainder of the canal is filled with MTA and/or gutta percha if a post is to be placed. Depending on the extent of the fracture the tooth is restored with composite or a crown.

In a similar manner to the calcium hydroxide apexification technique, the disadvantages are a tooth with shorter roots and thin walls. MTA does not strengthen or reinforce teeth.

A more current approach to treating immature teeth with pulpal necrosis is a “triple antibiotic” technique that allows for revascularization, regeneration, and revitalization of the necrotic pulp tissue. The regeneration of vital pulp tissue is based on the influx of mesenchymal stem cells, found in dental pulp, the apical papilla and even inflamed periapical tissue into the root canal after canal disinfection with a triple antibiotic paste and evoked bleeding after instrumentation. The stem cells from the dental pulp, apical papilla and periodontal ligament self-replicate and differentiate into specialized tissues that promote root development and apical closure. Continued maturation of the root is induced by remnant Hertwig’s epithelial root sheath cells from the remnant apical papilla or circulating stem cells.

The technique is conventional cavity access and orifice location after anesthesia administration and isolation. As the open root apex prohibits use of an electronic apex locator, length measurement is obtained by using a #15 file and radiograph. The canal undergoes minimal instrumentation, and tissue remnants are removed by irrigation of the canal with 3% sodium hypochlorite or 0.12% chlorhexidine. An ultrasonic tip can be used to agitate the irrigant.

The canals are dried with paper points. A creamy paste is prepared consisting of:

  • 250mg ciprofloxacin

  • 250mg metronidazole

  • 150mg clindamycin

  • Propylene glycol

The tablets are ground with mortar and pestle.

The paste is placed into the root canal with a Lentulo spiral up to the cementoenamel junction (CEJ), and the access is sealed with a sterile cotton pellet and glass ionomer cement.

After 3-4 weeks, the antibiotic paste is removed using sodium hypochlorite and an ultrasonic tip. A 90 degree bend is placed in a #15 file and the instrument is place into the canal 2-3mm beyond the apex. The instrument is agitated to stimulate bleeding. A clot is allowed to form as close to the CEJ as possible. A 3-4mm plug of white MTA is placed and sealed with a moist cotton pellet and GIC. The cotton pellet and glass ionomer cement are removed after 1-week and the tooth restored with composite. Apical closure with revitalized tissue is obtained in 6-24 months with a success rate of approximately 75%. It is not necessary to reenter the tooth after apical closure as the pulp tissue is vital. If post placement for crown retention is necessary, then routine endodontic therapy is necessary.

The prognosis of complicated crown fractures appears to depend primarily upon associated injuries to the periodontal ligament. The age and size of the pulp exposure and the stage of root development at the time of injury can also affect the tooth’s prognosis. Follow up treatment consists of clinical examination after one week and radiographic examination at six to eight weeks, and one year intervals.