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References

Wiskott HWA.London: Quintessence Books; 2011
Wassell RW, George G, Ingledew RP, Steele JG. Crowns and other extra-coronal restorations: provisional restorations. Br Dent J. 2002; 192:(11)619-630
Frederick DR. The provisional fixed partial denture. J Prosthet Dent. 1975; 34:520-526
Johnson WM. Material science of interim fixed restorations. In: Rosenstiel SF, Land MF, Fujimoto J (eds). St Louis: Mosby; 2006

A direct wax-up technique for an immediate provisional crown

From Volume 42, Issue 9, November 2015 | Pages 892-893

Authors

Stuart Campbell

BDS, MSc, MFDS, PGCert

General Practitioner, Loanhead Dental Practice, 50 Fountain Place, Loanhead, Midlothian, EH20 9DU

Articles by Stuart Campbell

Matthew Brennand Roper

BDS, MClinDent, MFDS, MJDF, MPros RCSEd

Specialist in Prosthodontics, Specialty Registrar in Restorative Dentistry, Edinburgh Dental Institute, Lauriston Building, Lauriston Place, Edinburgh EH3 9HA, UK

Articles by Matthew Brennand Roper

Article

The transitory function of provisional crowns means that these restorations are frequently fabricated directly in the mouth using comparatively inexpensive procedures.1

Many operators will use an alginate or silicone impression of the tooth to be prepared to produce a provisional crown that duplicates the form of the existing tooth.2 This matrix technique has proved popular, especially when a silicone impression is taken. Such materials enable the operator to retain a dimensionally stable index of the prepared tooth form, during the inter-appointment period, in case of failures. However, some situations will require a modification of this approach. These are, inter alia:

  • Unacceptable occlusal form due to restorative failures or tooth fractures;
  • Teeth that have been previously prepared and where the crown is subsequently lost;
  • Failed or lost provisional crowns when the pre-operative matrix is unavailable.

    • In such situations, the clinician has little to go on to help reproduce the external contours of the damaged tooth. Consequently, the shape of the tooth must first be improved before construction of a matrix (Figure 1).

    Figure 1. Damaged tooth requiring immediate provisional restoration.

    We present a simple procedure that has proved satisfactory in overcoming some of the challenges presented.

  • Soft red wax is formed into a ball (Figure 2).
  • To ensure retention of the wax, Copal varnish is applied to the damaged tooth and allowed to dry. The opposing teeth are greased with petroleum jelly.
  • The wax is moulded over the damaged tooth and the patient is instructed to close into the intercuspal position and to make lateral excursions. In this way, the cusps of the opposing dentition demarcate the occlusal surface design (Figures 3, 4).
  • Hand instruments are used to carve and shape the wax (Figure 5).
  • An impression of the intra-oral wax-up is recorded in silicone to form a new matrix (Figure 6).
  • The tooth stump is greased with petroleum jelly to ease removal of the acrylic provisional. If gingival control at the margin is poor, use retraction cord prior to forming the provisional to gain a precise marginal fit (Figure 7).
  • An auto-polymerizing Bis-acrylic resin (Protemp, 3M ESPE) is placed in the matrix and returned to the patient's mouth and allowed to set.
  • After removal from the mouth, the restoration is placed in a bowl of hot water (50ºC) to maximize polymerization.3,4 At this point, the thickness of the provisional can be measured to ensure that there is appropriate space for the desired restorative material.
  • Trim and polish the restoration, correcting any over contours from the wax-up (Figures 8, 9)
  • Evaluate the proximal contacts, marginal fit, occlusion and then cement. Ensure thorough removal of excess cement to prevent periodontal complications (Figure 10).
    • Figure 2. Ball of red wax prior to placement on the tooth.
    Figure 3. Soft red wax moulded over damaged tooth.
    Figure 4. Opposing cusps demarcate occlusal pathways into wax.
    Figure 5. Wax is shaped intra-orally.
    Figure 6. Impression of wax-up. Note over-contoured areas, which can be removed when trimming the provisional restoration.
    Figure 7. Tooth preparation is refined.
    Figure 8. Provisional after removal from mouth.
    Figure 9. Provisional after trimming and polishing.
    Figure 10. Cemented direct immediate provisional.

    This procedure requires no special equipment, is relatively simple and is particularly suited for the construction of provisionals when the pre-operative external contour of the tooth is unknown; due to lost restorations, loss of tooth structure, or when a pre-operative matrix is unavailable.

    Discussion

    Red ribbon wax was used in this technique tip, since it is easy to handle, inexpensive and widely available. This does not imply that other materials cannot be considered.

    Resin composite and poly-ethyl acrylic are two such materials that can also be used to similar effect. While the former is surely available to almost all practitioners, the increased cost, together with the need to employ effective moisture control techniques, represent disadvantages when this material is compared to red ribbon wax.

    Self-curing acrylics have a long track record for use as direct provisional restorations, however, their use has declined in recent years, owing to the popularity of alternatives such as Bis-acryl.1 Consequently, it seems reasonable to infer that not all practitioners will choose to stock self-cure acrylics in practice. As well as such issues with availability, poly-ethyl acrylics undergo an exothermic setting reaction and the potential trauma to the pulp cannot be ignored. A further disadvantage is that acrylic requires significant time to set fully as compared with the wax technique.