Gutta percha points

For a tooth in which the pulp is too damaged by trauma or infection to survive, the usual clinical procedure is extirpation of the pulp, followed by sealing of the root system of the tooth. This procedure is aimed at preserving the structure of the tooth despite its loss of vitahty, and typically employs pre-formed gutta percha points to prove the bulk of the obturation. There is also some sort of sealing material employed as well [73]. 

The main material used for obmration of the cleaned and disinfected root canal in contemporary endodontics is gutta percha. This is used because it is plastic and will take up the shape of the root canal when pressed into place [74]. A sealant is used in association with these gutta percha points, and its function is to fill any gaps between the points and the canal walls. This has the effect of improving the quality of the overall seal at the tooth root [73]. 

The most widely used means of obturating tooth roots following extirpation of the pulp is with gutta percha points which can be compressed into irregularly shaped root canals using either lateral or vertical compaction techniques (Fig. 10.1). These gutta percha points are usually warmed with a heated plugger, with an initial master point placed first, followed by accessory points as necessary to complete obturation [6]. 

Table 10.1 Composition of typical commercial gutta percha points [7]...

Studies have shown that the composition of gutta percha points varies between manufacturers [7], In particular, the proportions of gutta percha polymer and zinc oxide filler may differ widely. These differences may lead to variations in mechanical properties and also in the ease of flow on heating between different proprietary brands. 

It should be noted in passing that the possibility of using only one of the materials (eg, gutta percha points or sealer paste) has been considered for endodontic therapy [17]. The concept has been called monoblock . However, though it would be advantages in the clinic if it were feasible, it has not proved possible to develop the approach for practical use. Either gutta percha or sealer alone cannot produce a seal of sufficient soundness or durability to give acceptable clinical results. 

Leakage around calcium hydroxide sealers has been studied experimentally, and findings have generally been satisfactory [34-36]. However, there have been some adverse reports [37], and these variations have been attributed to crucial differences in experimental methods [38]. Leakage appears to be related to both the solubility of the material and the questionable adhesion to both the dentine walls and the gutta percha points. The calcium hydroxide sealer Apexit, for example, was found to have a high solubility when set compared with other types of endodontic sealer [39] and, in some studies, sealer particles have been found to occur with the tissues at a considerable distance from the sample [40,41],... 

F. Goldberg, J. Gurfunkel, Analysis of the use of Dycal with gutta percha points as an endodontic filling technique, Oral Surg. Oral Med. Oral Pathol. 47 (1979) 78-82. 

Which will have the higher softening point (a) gutta percha or (b) hevea rubber ... 

This polymer is a hard plastic that occurs naturally as gutta-percha or balata. Since the trans isomer packs better than the cis isomer, it has a higher specific gravity, a higher degree of crystallinity, and a higher melting point (67 C) than the ds isomer of polyisoprene. The chemical and the solvent resistance of the trans polymer are simitar to those of the ds polymer. 

Natural rubber is a polymer of isoprene- most often cis-l,4-polyiso-prene - with a molecular weight of 100,000 to 1,000,000. Typically, a few percent of other materials, such as proteins, fatty acids, resins and inorganic materials is found in natural rubber. Polyisoprene is also created synthetically, producing what is sometimes referred to as "synthetic natural rubber". Owing to the presence of a double bond in each and every repeat unit, natural rubber is sensitive to ozone cracking. Some natural rubber sources called gutta percha are composed of trans-1,4-poly isoprene, a structural isomer which has similar, but not identical properties. Natural rubber is an elastomer and a thermoplastic. However, it should be noted that as the rubber is vulcanized it will turn into a thermoset. Most rubber in everyday use is vulcanized to a point where it shares properties of both, i.e., if it is heated and cooled, it is degraded but not destroyed. 

Dental root treatment commonly comprises removal of the necrotic pulp or its remnants, cleaning, widening, and sterilization of the root canal, and filling of the prepared canal with core and sealing materials. Popular core materials are silver, gutta-percha, and silicon rubber points, and these are sealed in place by a cement sealer. 

Materials employed as points are usually fabricated from gutta percha, though other materials have been considered (see Sections 10.2 and 10.3). Materials for sealers may be cements, including acid-base cements, or methacrylate monomer-based materials of the type used in composite resins. However, more commonly in modem endodontics, cements based on tricalcium silicate systems that set by hydration processes are used. This chapter discusses the wide variety of possible materials that can be used for this purpose, with some indication of the clinical effectiveness. 

Gutta percha is the most widely used material for endodontic points, for the reasons already described. However, other materials have been used, of which until recently, silver was the most important [13], and silver points had the advantage of being inherently bactericidal. 

Gutta percha is the most widely used material for points. It is a semi-solid with excellent biocompatihihty properties. 

Friedman C M, Sandrik J L, Heuer M A, Rapp, G W (1975) Composition and mechanical properties of gutta-percha endodontic points. JDent Res, 54, 921-925. 

For the purpose of illustration, the way in which structural factors of apparently minor importance may be decisive for the existence of high-elasticity may be pointed out. Referring to p. 35, where the chemical formulae of rubber and gutta percha are shown to be different only, in that one is the cis and the other the trans form of poly-isoprene, it may be asked why the first is rubbery elastic at room temperature, while the other only possesses this property after being heated above 60 C. Gutta is crystalline at room temperature and melts at 60° C, proving that at this temperature the micro-Brownian motions of the chain elements become so intense, that the lattice forces are insufficient to keep these parts fixed. 

Meyer returned to sound thermodynamic analysis in the discussion of the dependence of the melting point on tension for lightly vulcanized gutta-percha. The classic curve is shown in Fig. 3.12. 

Fig. 3.12 Tension dependence of the melting point of gutta-percha [16] (Interscience, by permission)...

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