Successful obturation requires the use of materials capable of densely filling the entire root canal system and providing a tight seal of the apical segment of the canal.
The root filling is a combination of sealer (or cement) with core material (silver point, gutta-percha, etc.). The core acts as a piston on the flowable sealer, causing it to spread, fill internal irregularities of root canal system and to attach to the instrumented dentin wall. Ideally, the sealer should come into contact with root canal wall; only occasionally does the gutta-percha protrude from the sealer and touch the dentin.
Both sealer and core material should possess specific properties.
Many materials for obturation are available on the market. Dr. Louis I. Grossman (fig. 24.1), one of the founders of the specialty of endodontics, determined the ideal properties of obturation materials (table 24.1). This list of desirable properties of root filling materials is a classic and is known as Grossman's criteria.
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Fig. 24.1. Dr. Louis I. Grossman and his famous aphorism (image source: dentaltown.com)
Table 24.1. Requirements for Ideal Root Filling Material (Grossman, 1978)
Ideal root filling material should show the following features: |
1) easily introduced into the canal; |
2) seal the canal laterally as well as apically; |
3) impervious to moisture; |
4) bacteriostatic or at least not encourage bacterial growth; |
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6) sterile, or quickly and easily sterilized before insertion; |
7) easily removed from the root canal if necessary |
Ideal root filling material should NOT: |
1) shrink after being inserted; |
2) stain tooth structure; |
3) irritate periapical tissue |
While each property may be desirable in itself, it must be clear that technically and practically, and even some of the biologically desirable properties must be subordinate to the primary functions of the root illing: illing and sealing.
Taking these into consideration, the clinician should realize that material composition, toxicity and physical properties are controlled by the manufacturers. The clinician's choice of obturation materials should be based on clinical situation; and those that best match the instrumentation and obturation techniques should be used.