Injectable materials in root canal therapy

In endodontic treatment, the aim is to completely seal the root canal. Traditionally this has been carried out with cones of gutta percha, also containing added zinc oxide, barium sulfate, plasticizers and coloring agents (Friedman et al, 1975), packed into the canal with a sealer - usually a cement containing zinc oxide and eugenol. A concern with this material system is that there is no adhesion between gutta percha and the sealer, or between the sealer and the tooth dentin. Further, complete adaptation of the material to completely obturate the root canal is not always achieved. 

Injectable thermoplasticized gutta percha systems have been developed in attempts to achieve good obturation - currently available systems have been reviewed by GUckman et al. (2000, 2001). These systems can be successful, but do not eliminate the need for careful shaping and cleaning of the root canal prior to filling. 

However, it is surprising and disappointing that there appears to be no rheological data on these materials in the literature. It would be of value to know the temperature dependence of rheological properties on temperature and shear rate, and if thixotropy occurs. It would also be desirable to know if the material had any viscoelastic properties. 

Alternative polymer systems have been developed for root canal obturation. These include a degradable polymer (polycaprolactone) and a bioactive glass (Elzubair et al., 2006). Similar to gutta percha, these materials are thermoplastic and can be heated and injected into the root canal. As before, however, there appears to be no rheological information about them in the literature. 

An alternative suggested approach to endodontic treatment is to use injectable bone substitute and calcium phosphate materials, which have been described as promising in terms of biocompatibility, bioactivity and rheological properties (Enkel et al., 2008). 

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