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Azerbaycan Saytlari

 »  Home  »  Endodontic Articles 12  »  Temporization for endodontics
Temporization for endodontics
Influence on final restoration - Temporization of broken down teeth.

Influence on final restoration.
Materials used for provisional restorations in endodontics can affect the polymerization and adhesion obtained with composite resins and other materials used to permanently restore endodontically treated teeth. Many studies have proved that residual eugenol may have a deleterious effect on the physical properties of composite resin restorations such as surface roughness, microhardness and colour stability. Other studies demonstrated that residual eugenol reduced the bond strength or even precluded bonding of the composite resin (Macchi et al. 1992). Hansen & Asmussen (1987) showed that the incidence and the extent of marginal gaps were markedly increased in cavities previously temporized with ZOE temporary fillings. This is, in fact, more closely related to possible marginal microleakage. In a similar more recent study using two newer dentine bonding systems, it was demonstrated that neither IRM nor Cavit interfered with the dentine or enamel bond strength or increased the mean value of wall-to-wall contraction (Peutzfeldt & Asmussen 1999). These findings were explained by the differences in the technique required for each particular bonding system, namely the total-etch procedure. A study using migration of streptococci in vitro indicated that a eugenol containing root-canal sealer had no significant effect on the sealing ability of a light- and dual-curing bonding system (Wolanek et al. 2001). The use of 3 0-35% phosphoric acid for 15 s may result in demineralization of dentine to a depth of approximately 10 mm, and removes any residual cement or contaminated enamel. From the clinical point of view, the influence of the temporary restorative materials on the physical properties and bond strength of permanent restorations are not the only factors that should be accounted for. More important in endodontics is the marginal seal at the permanent filling-tooth interface. Woody & Davis (1992) showed that both eugenol containing or eugenol-free temporary cements increased microleakage at the dentine-restoration interface but not at enamel margins. Thus, it seems that the negative effect was mainly because of the residual cement rather than the eugenol it self. This can be further consolidated by the fact that Cavit also adversely influences the composite resin bond strength (Macchi et al. 1992). Removal of eugenol-free or eugenol-containing temporary restorations such as IRM may not be complete and remnants may be left behind in microscopic surface irregularities. Accordingly, and owing to the conflicting findings in the literature and the availability of many different bonding systems, it is preferable to avoid the use of ZOE temporary restorations in cavities to be restored permanently with composites. It is also recommended to use bonding systems that rely on the total-etch procedure. Glass-ionomer cement bond strength is not effected by either IRM or Cavit temporary restorations (Capurro et al.1993); however, this does not imply that glass-ionomer cement would provide a good marginal seal following the use of a eugenol-containing temporary cement. The insertion of a coronal barrier of sufficient thickness may provide an additional, more predictable coronal seal for endodontically treated teeth than can be achieved with just one of the available restorative materials (Wilcox & Diaz-Arnold1989, Diaz-Arnold &Wilcox1990).

Temporization of broken down teeth.
Many teeth requiring endodontic therapy have lost considerable coronal tooth structure. During the course of multivisit endodontic treatment the pulp-canal system must be sealed to preclude the ingress of oral fluids and the subsequent contamination of the root-canal system and leakage of intracanal medicaments into the mouth. Proper endodontic temporization may also serve some other purposes.
Root-canal treatment requires adequate isolation of the area of operation. Proper placement of the rubber dam on a mutilated tooth is often impossible because of extensive loss of tooth structure. In the past, temporary cements, copper bands, orthodontic bands and temporary crowns have been used. These methods cannot provide an adequate seal and a pleasing aesthetic result (Walton 2002). In addition, the methods are time consuming, and gaining an access into cements can run the risk of introducing and blocking a canal with cement particles. It is also quite difficult, if not impossible, to obtain acceptable restoration contours, marginal adaptation and occlusion (Abdullah Samani & Harris 1979, Kahn1982, Brady 1983). Pin-retained amalgam or composite resin as interim restorations to aid isolation have been suggested (Messing 1976, Kahn 1982). However, this practice may influence future restorative options, and introduces the risks involved in pin placement and their possible removal. Other retentive means for the interim restoration have been advised. Brady recommended the use of retention grooves or locks with composite resin materials for build-ups for isolation and cavity sealing between appointments (Brady1983).The use of retention grooves may provide more flexibility in the future restoration, but at the expense of sacrificing valuable tooth structure. Crown-lengthening surgery may be indicated.
Following the introduction of glass-ionomer cements, this material has found a wide and increasing use in dentistry (Wilson & Kent1972). The material has the ability to bond to prepared and unprepared tooth surfaces with significant increase in bond strength after preparation with polyacrylic acid (Powis et al. 1982). More recent research has demonstrated that polyacrylic acid pretreatment does not significantly enhance the dentine- glass-ionomer restorative bond strength, but produces more consistent results (Hewlett et al. 1991). Furthermore, glass-ionomer sealability of the unconditioned access cavity is almost equal to the sealability of reinforced ZOE cement (Lim1990). Nevertheless, it is preferable to condition the exposed surfaces with polyacrylic acid and to protect the filling material after insertion with varnish or unfilled resin as these steps improve the long-term sealing ability (Lim 1987, 1990). The use of glass-ionomer cement as a provisional build-up to aid in endodontic isolation and coronally seal the root canal was suggested recently (Bass & Kafalias1987, Morgan & Marshall 1990, Rice & Jackson 1992). The advantages are: providing adequate seal with the tooth structure and sufficient strength and retention to withstand the forces of the application of the rubber-dam clamp. The material is also radiopaque and can be rapidly and easily inserted with the possibility to commence endodontic treatment at the initial appointment (Bass & Kafalias1987, Morgan &Marshall1990, Rice &Jackson 1992). The disadvantages of the material are its cost and the aesthetic result that makes it less than ideal for use on anterior teeth. After the material sets, formal endodontic access can be created and root-canal instrumentation and obturation can proceed in the usual manner. Another technique to provide long-term provisionalization was described using resin-modified glass-ionomer cement, reinforced with a rounded wire tailored to allow direct entry to the pulp chamber. The disadvantage oft his method is the need to involve the occlusal surfaces of the adjacent teeth to which the reinforcing wire will be cemented (Liebenberg1994).
Composite resins have also been used for temporization of badly broken down teeth. The material enjoys wide acceptance because of its superior aesthetic results and micromechanical bonding to the prepared tooth structure (Abdullah Samani & Harris 1979, 1980). Composite resin does not always offer an acceptable material tooth interface seal, especially with poor moisture and contamination control (Derkson et al. 1986). Composite resins cannot be recommended as the ideal option for interim build-up and temporization of severely damaged teeth (Rice & Jackson 1992). Fracture of crown or root is a risk for teeth of this type, and the use of a stainless steel band has been shown to reduce cusp flexure and to double fracture strength (Pane et al. 2002). This, together with the use of a command-set resin-modified glass-ionomer cement and taking the tooth‘out of occlusion’may be appropriate management for badly broken down posterior teeth.