There are a few situations where the application of rubber dam may present difficulties, although the cautious clinician may consider whether root canal treatment is then either appropriate, or may be severely compromised.
The broken down tooth
The broken down tooth may be tackled in a variety of ways. Many molar teeth with large deficiencies may have rubber dam applied, providing the right clamp is used; the author recommends a W8a (see Fig. 2). With an appropriate length of floss as described earlier, the clamp is placed directly on to the tooth, so that there is a four-point contact between the jaws of clamp and the root. Once in position, the clamp is checked for stability by pressing on the bow. If firm, the rubber dam may be stretched over the clamp using the wingless technique described.
The broken down tooth
The broken down tooth may be tackled in a variety of ways. Many molar teeth with large deficiencies may have rubber dam applied, providing the right clamp is used; the author recommends a W8a (see Fig. 2). With an appropriate length of floss as described earlier, the clamp is placed directly on to the tooth, so that there is a four-point contact between the jaws of clamp and the root. Once in position, the clamp is checked for stability by pressing on the bow. If firm, the rubber dam may be stretched over the clamp using the wingless technique described.
It is also feasible to build up the tooth before commencing root canal treatment using glass ionomer (for example, Vitremer). Alternatively, an orthodontic band may be cemented around the tooth. On occasion, a clamp may be fitted on to a broken down tooth, but only if the gingival tissue encroaching on to the margin is first removed with electrosurgery or a surgical blade.
As part of the restorative treatment, periodontal crown lengthening, or orthodontic extrusion, may be indicated. These procedures should be carried out prior to commencing the root canal treatment.