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Azerbaycan Saytlari

 »  Home  »  Endodontic Articles 12  »  Temporization for endodontics
Temporization for endodontics
Gutta-percha - Zinc phosphate cement - Polycarboxylate cement - Zinc oxide/calcium sulphate - Zinc o



Gutta-percha.
Base plate gutta-percha and temporary stopping guttapercha were amongst the first materials tested, with less than ideal characteristics. Using dye and bacterial penetration tests in extracted teeth, Parris et al. (1964) found that gutta-percha temporary fillings leaked when subjected to two temperature extremes, 4-60 8C. In an in vivo study, Krakowet al. (1977) re-made access cavities in successfully root-filled teeth. The cavities were chemicallydisinfectedwith15 mL sodium hypochlorite irrigation (concentration not stated) followed by 15 mL of 0.067 m phosphate buffer (pH 7.2). Cotton pellets were left in the cavities under the temporary fillings for at least 1week, after which the pellets were retrieved and cultured an aerobically. Six out of eight samples temporized with gutta-percha demonstrated gross leakage. Findings from these studies are consistent with findings reported by Kakar & Subramanian (1963) in which gutta-percha was inferior to ZOE with and without thermocycling. Gutta-percha is not a commonly used temporary restorative material, and is not recommended for this purpose in endodontics.

Zinc phosphate cement.
Studies have shown controversial results concerning the sealing ability of zinc phosphate cement. Access cavities temporized with this material showed no leakage in more than two-thirds of cases in an in vivo study (Krakowet al.1977). In another study using the fluid filtration method to test microleakage, zinc phosphate cement did not show significant microleakage when compared to the intact crown, but visible leakage was observed in some of the samples temporized with this material (Bobotis et al. 1989). In a study by Marosky et al. (1977), radioactive calcium was used as a tracer to test microleakage of commercially available products for temporary restorations. The root surfaces of extracted teeth were covered withtinfoil and nail polish leaving the temporarily restored crowns exposed. The teeth were then immersed in an aqueous solution of calcium chloride after which the test teeth were removed, cleaned and sectioned through the test materials. The teeth were placed with the cut surfaces on dental X-ray films to produce autoradiographs. It was found that zinc phosphate cement was inferior to a zinc oxide/calcium sulphate based material, Temp-Seal (Union Broach Co. Inc., Bethpage, NY, USA), Cavit (3MESPE DentalAG, Seefeld/Oberbay, Germany) and ZOE. Kakar & Subramanian (1963) also found that this cement provided an inferior seal when compared to properly condensed amalgam and ZOE. Zinc phosphate cement is not widely used for endodontic temporization, probably owing to the emergence of newer temporary filling materials with more predictable sealing characteristics.

Polycarboxylate cement.
This material has been tested as a temporary restoration in in vitro studies with conflicting results. Marosky et al. (1977) found polycarboxylate cement to provide the least desirable seal when compared to Temp-Seal, Cavit, ZOE, zinc phosphate cement and Intermediate Restorative Material (IRM; L. D. Caulk Co., Milford, DE, USA). On the other hand, Pashleyet al. (1988) using a fluid filtration method found that polycarboxylate cement at a powder to liquid ratio of 2 : 4 was not significantly different from Cavit-G, even after thermocycling. Polycarboxylate cement is not commonly used in endodontics and cannot be recommended, as its clinical effectiveness for endodontic temporization does not appear to have been well established.

Zinc oxide/calcium sulphate preparations.
Cavit is a premixed temporary filling material that contains zinc oxide, calcium sulphate, zinc sulphate, glycol acetate, polyvinylacetate resins, polyvinyl chloride acetate, triethanolamine and pigments. As a hygroscopic material, Cavit possesses a high coefficient of linear expansion resulting from water sorption. Its linear expansion is almost double that of ZOE, which explains its excellent marginal sealing ability (Webber et al. 1978). Body discoloration oft his material was observed in fresh samples allowed to set in vegetable dye indicating sorption of the dye rather than body leakage (Widerman et al. 1971). However, it was proved later that this material showed body leakage even when allowed to set in water before immersion in dye (Todd & Harrison 1979, Tamse et al.1982, Kazemi et al.1994). It was also suggested that the marked body discoloration resulting from sorption or body leakage could influence the marginal leakage observed (Teplitsky & Meimaris 1988, Kazemi et al.1994, Jacquot et al.1996, Uranga et al.1999).Assessment of immediate and early sealabilityof Cavit revealed that after placement, marginal penetration can be considered as a potential pathway for oral contaminants (Todd & Harrison 1979). Cavit’s compressive strength is approximately half that of ZOE, so there is a need for sufficient bulk to overcome poor strength qualities and provide an adequate seal (Widerman et al. 1971, Webber et al. 1978). Temperature fluctuations did not influence the sealability of Cavit products, indicating good dimensional stability (Gilles et al. 1975, Oppenheimer & Rosenberg1979).When left in contact with metacresylacetate, camphorated mono-chlorophenol (CMCP) and formocresol intracanal medicaments for1and 7 days, the surface hardness of Cavit did not differ significantly to the material left in contact with saline (Olmsted etal.1977).
The sealing ability of Cavit has been tested in many studies, both in vitro and in vivo, with generally favourable results. In in vitro studies, Webber et al. (1978) tested the thickness of Cavit required to prevent methylene blue dye leakage. It was found that at least 3.5 mm of the material was required to prevent dye leakage. Comparing sealing ability in parallel or divergent class I cavity preparations, Cavit proved more effective than Temporary Endodontic Restorative Material (TERM, L. D. Caulk Co., Milford, DE, USA) and IRM in that order. However, the difference between Cavit and TERM and the effect of the two cavity designs did not reach significance (Barkhordar & Stark 1990). In in vivo studies, no leakage or minor leakage was found in 27 out of 32 cases when Cavit was used to temporize access cavities in anterior teeth and only15% of cases tested showed gross leakage (Krakow et al. 1977). In another study, Cavit in a 4-mm thickness provided the best seal over a 3-week temporization period when compared to IRM and TERM (Beach et al.1996). A2-mm thickness of Cavit was tested in anterior teeth of monkeys over 2,7 and 42 days. This thickness was not effective in preventing bacterial microleakage over the experimental period, and the longer the restoration stayed in the mouth the more bacterial contamination was detected (Lamers et al. 1980). These findings further confirm the need for sufficient bulk oft his material and are in agreement with the previous ¢findings (Webber et al. 1978). Other studies have also shown that Cavit can provide an acceptable seal when compared to other materials (Chohayeb & Bassiouny1985, Pashley et al.1988, Kazemi et al.1994).
Cavit-G and Cavit-Ware varieties of Cavit that differ in the content of resin and their resulting hardness and setting. The hardness and dimensional stability of Cavit, Cavit-Wand Cavit-G decrease, respectively. It was found that Cavit and Cavit-Wprovided almost equal watertight seals, which was significantly superior to the seal provided by Cavit-G (Jacquot et al. 1996). Cavidentin (Laslo Laboratories, Natanya, Israel) is another calcium sulphate-based material, which has a similar formula to Cavit but with the addition of potassium aluminium sulphide as catalysts and thymol as an antiseptic. In an in vitro study, a 5-mm thickness of Cavidentin provided superior sealing ability compared with IRM, Kalzinol (a reinforced ZOE preparation, De Trey,Weybridge, UK) and Cavit. Cavidentin and Cavit-G were almost equally effective (Tamse et al.1982). Coltosol is a zinc oxide, zinc sulphate and calcium sulphate hemihydrate-based material (Coltene Whaledent, Mahwah, NJ, USA). The surface of Coltosol hardens within 20-30 min when in contact with moisture and according to the manufacturers the filling can be subjected to mastication pressure after 2-3 h. This material is designed for short term temporization not exceeding 2 weeks; it does not appear to have been tested as a temporary restoration for endodontics.
A recent paper compared Cavit and Caviton (zinc oxide, Plaster of Paris and vinyl acetate, GC Corporation, Tokyo, Japan) with Fermin (a zinc sulphate cement, Detax GmbH & Co. KG, Weisendorf, Germany) and Canseal (a noneugenol cement requiring mixing, Showa Yakuhin Kako Co. Ltd.,Tokyo, Japan) in a leakage study using methylene blue (Cruz et al. 2002). The best seal was provided by Fermin, followed by Caviton, Cavit and Canseal. The study indicated that thermal cycling procedures influenced seal more than load cycling.
Clinically, Cavit and its relatives have the advantages of ease of manipulation, availability in premixed paste and of being easily removed from access cavities after setting. Additionally, it is clear that Cavit can provide adequate seal of an access cavity between appointments. However, its hardness, wear resistance, slow-setting reaction, and deterioration with time are key disadvantages (Widerman et al. 1971, Todd & Harrison 1979, Lim 1990). For these reasons, Cavit can be recommended for short-term temporization in small cavities. A double seal using Cavit as an inner layer and IRM as an outer layer has been recommended to compensate for the undesirable physical properties of Cavit. Furthermore, this combination showed better dentine adaptation when compared to IRM alone (Paiet al.1999).

Zinc oxide and eugenol preparations.
Many temporary restoration products are ZOE based, with or without reinforcement. Plain ZOE with a powder to liquid ratio of4 :1 (g mL_1) as commonly used results in a poor initial seal, which shows some improvement after 1 week. A lower powder to liquid ratio of 2 :1 gives better initial sealability but this seal may slightly deteriorate with time (Pashley et al.1988). Simple ZOE temporary cement was found less effective in precluding radioactive tracer leakage when compared to Cavit and Temp-Seal, but superior to zinc phosphate cement, IRM and polycarboxylate cement (Marosky et al. 1977). Commercial products based on ZOE such as Dentemp (a ZOE-based material that lacks reinforcement; Majestic Drug Co., Bronx, NY, USA) and Kalsogen Plus (a ZOE based material that lacks reinforcement; DeTrey, Dentsply, York, PA, USA) have been tested and compared with other materials. After thermocycling, Dentemp proved less effective in preventing silver nitrate penetration when compared to TERM and three different Cavit preparations, but almost equally effective when compared to IRM (Noguera & McDonald 1990). Kalsogen was also found less effective in preventing dye penetration when compared to Cavit and TERM after thermocycling and mechanical loading (Mayer & Eickholz1997).
Kalzinol is a ZOE-based cement reinforced with 2% by weight polystyrene polymer to double its compressive strength. Using an electrochemical technique to test microleakage, it was reported that this cement provided better sealing properties when compared to Cavit-W and was almost equal to glass-ionomer cement used in unconditioned cavities (Lim1990). IRM is a ZOE cement reinforced with polymethyl methacrylate. This reinforcement provides the restoration with improved compressive strength, abrasion resistance and hardness (Blaney et al. 1981, Anderson et al. 1990). The manufacturers recommend the use of IRM as a temporary restoration for cavities for up to 1 year using a powder to liquid ratio of 6 :1 (g mL_1). Following these recommendations usually results in a less than ideal seal but provides more optimum physical properties. The use of less powder provides a better seal at the expense of minimally compromising the physical properties (Pashley et al. 1988, Anderson et al. 1990). In addition, a softer mix exhibits greater antibacterial activity due to hydrolysis and the subsequent increase in the release of eugenol, an antibacterial agent which may prevent bacterial colonization if leakage takes place (Chandler & Heling 1995). In this regard, IRM is also supplied in pre-measured capsules for mixing in an amalgamator. Leakage of IRM increased when subjected to thermal stress, which was attributed to its dimensional instability (Gilles et al. 1975, Anderson et al. 1988, 1990, Bobotis et al. 1989,). IRM was assessed and compared to other temporary restorative materials in a number of studies both in vivo and in vitro with conflicting findings. In an in vivo study, IRM performed almost equally to Cavit for temporizing class I access cavities in human teeth using a 4-mm thickness over a 3-week period (Beach et al. 1996). In an in vitro study, IRM allowed to set next to CMCP prevented Proteus vulgaris penetration significantly better than Cavit set next to both CMCP and saline solution (Blaney et al.1981).These findings are of special interest knowing that CMCP significantly reduced the surface hardness of IRM whilst it did not influence the hardness of Cavit (Olmsted et al.1977). Using the fluid filtration method, IRM microleakage was not significantly different from intact crowns except at 7 days and after thermocycling (Anderson et al. 1988, Bobotis et al. 1989). Other in vitro studies using radioisotope and electrochemical methods showed more favourable results with IRM compared to Cavit (Friedman et al. 1986, Jacquot et al.1996). On the other hand, several in vitro studies using silver nitrate as an indicator (Barkhordar & Stark 1990, Noguera & McDonald 1990), calcium chloride radioisotope (Marosky et al. 1977), dye penetration (Lee et al. 1993, Kazemi et al. 1994, Mayer & Eickholz 1997), fluid filtration method (Anderson et al.1988, Pashley et al. 1988, Bobotis et al.1989) and bacterial penetration (Deveaux et al. 1992) all demonstrated that IRM provides sealing properties inferior to those of Cavit.
Some of these studies provided semi-quantitative results where dye penetration was assessed in one longitudinal section, which limits three-dimensional penetration to a two-dimensional section (Lee et al. 1993, Mayer & Eickholz1997). Others did not take into consideration dye penetration into the body of the material, which may effect the overall microleakage values (Barkhordar & Stark1990). Furthermore, data obtained from semi-quantitative methods depends on the subjective interpretation of the evaluator rather than providing numerical data for statistical analysis. Radioisotope penetration studies also provide semi-quantitative results where the measurements were done at the filling- tooth interface only, without assessing the body penetration (Marosky et al.1977). Studies using the fluid filtration technique showed better results with Cavit when compared to IRM (Anderson et al. 1988, Pashley et al.1988, Bobotis et al.1989).The fluid filtration method is an accurate quantitative method to test microleakage of temporary restorative materials. The measurements can be repeated at different intervals and before and after thermocycling without destroying the sample. However, this method may be accurate in measuring the marginal microleakage but probably not the body leakage of the material because the time of measurement was often too short.
The majority of in vivo and in vitro studies employing bacteria demonstrated almost equal or better seal with IRM (or ZOE) than with Cavit (Parris et al.1964,Krakow et al. 1977, Blaney et al. 1981, Beach et al. 1996, Barthel et al.1999). Only Deveaux et al. (1992) showed that Cavit was superior to IRM in preventing Streptococcus sanguis penetration. The authors related this finding to the presence of a growth-inhibiting factor (probably zinc ion) present in Cavit. However, in a pilot study with unpublished data, the authors found that IRM also demonstrated antibacterial effects as tested by agar diffusion tests. Therefore, it is possible to speculate that either the antibacterial effect of IRM could not prevent S. sanguis penetration, or that Cavit provided a better seal. When comparing P. vulgaris penetration, IRM set on a cotton pellet saturated with CMCP was more effective than IRM set next to saline and Cavit next to CMCP or saline in this order (Blaneyet al.1981).The bacterial penetration method in vitro is considered an acceptable approach for microleakage studies. It however, omits some clinical factors and does not directly reflect the sealability of the tested materials rather, a combination of leakage resistance and antibacterial effect. From the clinical point of view, microleakage studies of temporary filling materials should account for their antibacterial effect. In addition, the effect of intracanal medicaments on the setting and the subsequent leakage and the combined antibacterial effect of the temporary filling and intracanal medicament should be considered.
Based on the previous discussion and the results of in vivo studies, it can be stated that ZOE temporary restorative materials, including IRM, can provide adequate resistance to bacterial penetration during the course of endodontic treatment especially when used with a low powder to liquid ratio.

Glass-ionomer cement.
Glass-ionomer cements have a variety of applications in endodontics (Friedman 1999). Use of these materials as a temporary restoration during endodontic therapy has been investigated in a number of studies with favourable results. In one study using the fluid filtration method, glass-ionomer cement microleakage values did not differ significantly from the intact crown values after 8 weeks (Bobotis et al. 1989). In another in vitro study using an electrochemical technique, glass-ionomer cement placed in unconditioned cavities was almost equally effective compared to Kalzinol and superior to Cavit-W after a1-month experiment period (Lim1990). In amore recent study, glass-ionomer cement alone or on top of an IRM base provided a significantly superior seal against penetration of S. mutans when compared to Cavit, IRM and glass-ionomer cement on a Cavit base, over a1-month period (Barthel et al.1999).
The adhesion mechanisms of glass-ionomer cements explains their acceptable sealing ability (Watson 1999). Additionally, glass-ionomer cements possess antibacterial properties against many bacterial strains (Tobias et al.1985, Chonget al.1994, Heling& Chandler1996, Herrera et al.1999).The antibacterial activity of the material is attributed to the release of fluoride, low pH and/or the presence of c ertain cations, such as strontium and zinc in some cements. For these reasons, glass-ionomer cements can be considered as a satisfactory temporary endodontic restorative material and may also be used in cases requiring longer term temporization. The cost, speed of setting and the difficulty in differentiating glass iomomers from the surroufinding tooth structure during removal have presented problems. A new material, Fuji VII Command Set (GC Asia Dental, Singapore) addresses some concerns. It autocures in 4 min or cures with a halogen light in 20-40 s, and has a pink chroma for easy identification of margins. It also claims a higher fluoride release than other glass-ionomer cements. Metal-reinforced glass-ionomer cements (cermets) are only available with silver particles (Chelon-Silver, Ketac-Silver, 3M ESPE, Seefeld/Oberbay, Germany) and are recommended by manufacturers as temporary posterior materials. They do not appear to be in common use in endodontics, and whilst exhibiting increased wear resistance and higher flexural strength they have less fluoride release and lower bond strengths than other glass-ionomers.

Composite resin.
TERM is a relatively recently introduced temporary restorative for endodontics. This material is a single component light-curable resin that contains urethane dimethacrylate polymers, inorganic radiopaque filler, organic prepolymerized filler, pigments and initiators. Like other composite resins, this material undergoes polymerization shrinkage representing 2.5% of its volume. This contraction is usually followed by expansion owing to secondary water sorption (Deveaux et al. 1992). The minimum thickness for effective cavity sealing was investigated in vitro using thermocycling and the fluid filtration technique. It was found that 1-3- mm-thick TERM were as effective as a 4-mm thick one in providing a cavity seal after a 5-week interval and thermocycling. This does not represent an indication to use 1- or 2-mm-thick TERM clinically, as other factors not accounted for in the study may operate in vivo (Hansen & Montgomery 1993). It is generally accepted that TERM has higher hardness, tensile and compressive strengths than Cavit. Also, TERM’s sealability was not affected by certain intracanal medicaments (Rutledge & Montgomery1990).
Following its introduction, the material was investigated in several in vivo and in vitro studies with controversial findings. In an in vitro study, Teplitsky & Meimaris (1988) found that TERM provided an effective marginal seal in only 33.3% of cases compared with 91.7% for Cavit. Thermocycling did not adversely effect the sealability of Cavit, but led to an increased incidence of microleakage with TERM. In another study, Melton et al. (1990) found that TERM provided 67% sealability compared to 100% for Cavit when used to seal-etched and nonetched cavities without thermocycling. In vivo, it was found that TERM is inferior to IRM and Cavit in class I cavities when used in 4-mm thickness and for a 3-week temporization period (Beach et al. 1996). Many other studies have demonstrated similar effectiveness of TERM and Cavit. TERM was found to be as effective as Cavit for marginal seal and superior to IRM, but the authors stated that the physical properties of IRM were considered superior to those of TERM and Cavit (Barkhordar & Stark1990).These findings are in accordance with other reports (Deveaux et al. 1992) where both TERMandCavit were almost equally effective in preventing S. sanguis penetration before and after thermocycling. Findings from another in vitro study showed that after thermocycling, TERM provided better sealing ability when compared to Cavit, Cavit-G and Cavit-W (Noguera & McDonald1990).
TERM does not possess antibacterial activity when tested with S. sanguis on agar plates. The good sealing properties of TERM demonstrated in some studies can be attributed to the mode of insertion of this material. The material can be injected using a syringe with a fine compule end-piece, eliminating the possible inclusion of gaps within the body of the material or at the margins (Deveaux et al. 1992). In addition, dye leakage studies failed to show significant body penetration for this material (Teplitsky & Meimaris 1988, Noguera & McDonald 1990). Although TERM did not consistently provide better sealing ability than Cavit and IRM, it can be stated that TERM may have the potential to provide an adequate seal for temporization of an endodontic access cavity when used in sufficient bulk. Further clinical studies are required with standardized methodologies to confirm the effectiveness oft his material. The use of composite resin materials designed for permanent restorations to temporize access cavities has also been investigated. Uranga et al. (1999) found that composite resin and resin-modified glass-ionomer cement provided a better seal against methylene blue dye penetration after thermocycling when compared to Cavit and Fermit (Vivadent, Schaan, Liechtenstein), two temporary restorative materials.