Orthograde root-canal-filling materials.
C. H. J. Hauman & R. M. LoveDepartments of Oral Rehabilitation and Stomatology, School of Dentistry, University of Otago, Dunedin, New Zealand.Solid filling materials.Gutta-percha.
Gutta-percha is the main filling material used in rootcanal treatment although it only forms about 20% of the composition of modern gutta-percha cones. Zinc oxide is the main component (60-70%) of the cone and provides a major part of the radiopacity. The remaining 10% is not specified, as it is proprietary information but consists of a mixture of resins, waxes and metal sulphates (Spngberg1999).
Gutta-percha is considered to have acceptable biocompatibility with a low degree of toxicity, a view based on findings in animal studies involving implanted pieces of gutta-percha (Spngberg 1969a, Wolfson & Seltzer 1975). These studies describe the formation of a collagenous capsule around the implants with very little or no inflammatory host response. Gutta-percha cones have however, been shown to be cytotoxic in in vitro tests. Spngberg (1969a) suggested that toxic agents bound to water-insoluble substances are responsible for the toxicity of gutta-percha cones. These substances are set free when gutta-percha is dispersed into small particulate fractions.
Wolfson& Seltzer (1975) found that with the exception of a calcium hydroxide and a chloroform-containing product, the toxic effects of natural occurring guttapercha (trans-polyisoprene) are similar to those of commercial gutta-percha. Munaco et al. (1978) and Pascon & Spngberg (1990) regarded the cytotoxic effect of commercial gutta-percha to be due to the high content of zinc oxide. Contrary to this belief, results from the study by Sunzel et al. (1997) showed that the addition of zinc reduced the toxicity of rosin and resin acid and appeared to be cytoprotective.
Complement activation was applied as a parameter to determine the inflammatory potential of four different brands of gutta-percha and nine ingredients of one of those products (ZnO,TiO2, BaSO4) in vitro (Serene et al. 1988). Each investigated brand of gutta-percha and all individual gutta-percha components stimulated the complement system. It was concluded from this data that overextension of gutta-percha might contribute to pain and periapical inflammation although this has never been shown clinically.
Holland et al. (1982) investigated the long-term reaction of rat connective tissue to silver and gutta-percha points over a period of1 year. One brand of gutta-percha and the silver points were well tolerated. The other brand of gutta-percha points caused pronounced effects with thick fibrous capsules and severe chronic inflammation of the surrounding connective tissue. This observation is in line with the inflammatory potential of guttapercha as shown in the study by Serene et al. (1988).
In a study by Sjogren et al. (1995) the tissue reaction to gutta-percha in the form of large, fine and rosin-chloroform- dissolved particles was tested. Large gutta-percha particles were well encapsulated and the surrounding tissue was free of inflammation. Fine particles and those treated by rosin-chloroform evoked an intense, localized tissue response, characterized by the presence of macrophages and multinucleated giant cells. The authors concluded that the size and surface character of guttapercha determine the tissue reaction to the material.
Calcium hydroxide-containing gutta-percha points and their efficacy comparable with calcium hydroxide pastes have been demonstrated (Holland et al. 1996). In an in vitro study by Podbielski et al. (2000) calciumhydroxide containing gutta-percha points demonstrated good inhibitory action on the bacterial growth of three of the four test organisms. Iodoform gutta-percha cones, introduced by Martin & Martin (1999) had a negligible effect on Enterococcus faecalis, but demonstrated a significant inhibitory effect on Streptococcus sanguis (Silver et al.2000).
Warm gutta-percha techniques impose the additional complication of heat generated during obturation which may have a deleterious effect on the periodontium. A temperature rise of 10 8C above normal body temperature is regarded as a critical level at which irreversible damage to periodontal tissues can occur (Gutmann et al.1987, Saunders1990). Studies have shown that the temperature hardly ever exceeded an increase of 10 8C at the external root surface during themoplasticized gutta-percha obturation techniques (Gutmann et al. 1987, Silver et al.1999, Sweatman et al.2001) and as such should not pose a problem.
Obturation with gutta-percha requires the use of sealing cement and although gutta-percha has been shown to be cytotoxic, the sealers are normally the most toxic element of the filling.