TECHNIQUE

Root Canal Procedures in Bears  (Disease Investigation & Management - Treatment and Care)

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Summary Information
Type of technique Health & Management / Disease Investigation & Management / Techniques:
Synonyms and Keywords Root filling (including pulpectomy, i.e. total removal of pulp tissues from the tooth). (B452.8.w8)
Description

NOTE: Although the procedure is described below as accurately as possible, this is NOT a substitute for learning the procedure by watching and assisting a veterinarian who is already experienced in the technique.

Preparation
  • Anaesthetise the bear. See: Treatment and Care - Anaesthesia
  • Intubate and place on inhalational anaesthesia .
  • Place a wooden block or other suitable instrument to keep the mouth open.
  • Place a rubber dam over the tooth.
    • This helps to maintain asepsis.
    • The dam also reduces debris and blood reaching the throat and being aspirated into the lungs during recovery from anaesthesia. (P1.1979.w4)
Clean out the pulp cavity
  • Clean out the whole pulp cavity.
    • Enlarge access to the canals using a round bur. (J432.15.w1)
      • If most of a canine tooth is still intact, working from the tip will not give a straight line access to the apex. 
        • An access cavity is made on the mesial surface of the tooth using a round or pear-shaped burr to give straight line access. (B470.16.w16)
    • Confirm the working length of the root canal e.g. by inserting a radiopaque instrument into the canal and taking a radiograph. (J432.15.w1)
    • Debride the root canal with root canal reamers and K files of increasing size. (J432.15.w1)
      • Mark the working length onto each file using a rubber endodontic file stop. (J432.15.w1)
    • Start with smaller files and work up to larger files. (B10.34.w41)
    • Use a debridement paste with the files. (B10.34.w41)
    • All debris must be removed; keep cleaning until the material coming out appears clean and vital. (B10.34.w41)
    • Measure advancement to the root apex using radiographs. (B10.34.w41)
    • Do not perforate the proximal tip of the root. (B10.34.w41)
  • Irrigate the pulp chamber with 3% hydrogen peroxide solution, alternated with 2.5% or 3% sodium hydroxide solution. (P64.26.w6, B10.34.w41, J432.15.w1)
  • Dry the canal:
    • First irrigate the pulp chamber with 70% ethyl alcohol. (P64.26.w6, B10.34.w41, J432.15.w1)
    • Remove any remaining moisture using sterile pipe cleaners, cotton-tipped swabs and paper points. (B10.34.w41, J432.15.w1)
    • Irrigate the canal with compressed air to finish the drying. (B10.34.w41)
Pack the canal
  • Usually, gutta-percha points plus a root canal sealer are used to pack the canal. (B470.16.w16)
    • Fill with sealed-coated gutta-percha points using a lateral step-back condensation technique. (J432.15.w1)
    • To fill the large canine teeth of a bear, the leading gutta-percha point can be thickened and lengthened by adding two 30 mm points, heating, and rolling the points together. (J432.15.w1)
    • Seal with zinc oxide-eugenol or bismuth (II) oxide-silver-methenamine-resin. (J432.15.w1)
  • Or: 
    • Mix zinc oxide powder: 2-3 g zinc oxide powder to one drop liquid eugenol and one drop foracresol. This produces a dry, malleable putty which can be used to fill the canal. (P64.26.w6)
    • Use a dental filler or root-canal sealant. (B10.34.w41)
    • To reach the root apex it may be necessary to use a flexible needle or plastic catheter. (B10.34.w41)
Restoration
  • 1) make a retentive shallow undercut in the dentine, line the cavity with zinc phosphate cement, condense silver amalgam into the preparation, shape and polish. (J432.15.w1) OR
  • 2) etch the enamel and dentin with 30% phosphoric acid, restore using a light curing compound, a dentine primer and a bonding agent. (J432.15.w1) OR
  • 3) Re-drill the cavity to a depth of 3 mm, making sure there is an undercut.
  • Mix a dental restorative resin as indicated by the manufacturer and use this to pack the cavity.
  • Apply firm finger pressure to the restorative for 30 seconds, then allow to air dry.

(P64.26.w6, B10.34.w41)

Appropriate Use (?)
  • Treatment of tooth fractures which have exposed the pulp tissue. (B10.34.w41)
    • Not including vertical fractures. (V.w6)
  • Treatment of teeth with severe attrition exposing the pulp. 
  • Treatment of broken canines with a horizontal fracture of the crown of the tooth, without fracture extension subgingivally or affecting the root, a closed root apex, and no evidence of periodontal disease. (J60.12.w1)
  • Note: bears maintain root-fillings well if the fillings are properly applied. (B407.w18)
Notes
  • The principles of root fillings are:
    • Complete access to the contents of the root canal;
    • Debridement of the canal, removing all tissue (e.g. necrotic pulp, vital pulp, pus).
    • Preparation of the canal, removing infected dentine, smoothing irregularities and widening the canal to a proper diameter for filling.
    • Disinfection, to reduce to a minimum the presence of microorganisms.
    • Obturation - hermetic sealing of the canal with a permanent filling material, so that no microorganisms can penetrate the canal and multiply in a dead space.
    (B452.8.w8)
  • The filling material (e.g. gutta-percha points) should reach all the way to the apex of the tooth root. (J432.15.w1)
Complications/ Limitations / Risk
  • Care must be taken not to perforate the proximal tip of the root. (B10.34.w41)
  • In some cases post-operative radiographs indicate that the apical area is not reached with the gutta-percha points. (J432.15.w1)
  • This procedure is not suitable for teeth where the fracture extends subgingivally (under the gum) or affects the root, the root apex is open, or if there is evidence of periodontal disease. (J60.12.w1)
  • If there is a vertical crack affecting the pulp cavity and extending below gumline, the tooth needs to be removed, not filled. (V.w6)
Equipment / Chemicals required and Suppliers
  • General anaesthetic agents and appropriate equipment for anaesthetic administration and monitoring.

  • Appropriate dental instruments and compounds.

Expertise level / Ease of Use
  • This procedure should be carried out by personnel with experience and training in dental surgery in animals. (V.w6)
Cost/ Availability
  • The costs of this procedure include the costs of the personnel required (minimum one suitably qualified person to carry out the dental work and one to monitor the anaesthetic), and costs of appropriate equipment.
  • Appropriate dental equipment to carry out this procedure properly on bears may be expensive.
Legal and Ethical Considerations
  • In some countries there may be legislation restricting the use of this type of technique to licensed veterinarians. For example in the UK: "The Veterinary Surgeons Act 1966 (Section 19) provides, subject to a number of exceptions, that only registered members of the Royal College of Veterinary Surgeons may practice veterinary surgery." (see: LCofC1 - RCVS Guide to Professional Conduct 2000 - Treatment of Animals by Non-Veterinary Surgeons).).
Author Debra Bourne MA VetMB PhD MRCVS (V.w5)
Referee Suzanne I. Boardman BVMS MRCVS (V.w6)
References B10.34.w41, B452.8.w8, B470.16.w16, P1.1979.w4, P64.26.w6, J432.15.w1

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