Este trabalho foi realizado no Laboratório de Pesquisa de Endodontia, Departamento de Odontologia Restauradora da Faculdade de Odontologia de Ribeirão Preto, Universidade de São Paulo, Brasil. Ribeirão Preto, 1996, 33p.

Introduction

 Temporary filling materials are used widely in dentistry. They are used in restorative procedures to protect tooth surfaces until the final restoration is placed (Parris et al, 1960).

In Endodontics, the function of a temporary filling material is two-fold; First, to prevent the saliva with its micro-organisms from gaining entrance into the root canal, thus preventing infection or re-infection; second, to prevent medicaments placed in the pulp chamber from escaping into the oral cavity, thereby preserving the effectiveness of the intracanal medication and preventing any chemical burn to the oral mucosa.

 If these criteria are to be met, the sealing qualities of a temporary filling material are of primary importance in Endodontic therapy (Webber et al, 1978), especially if this therapy requires multiple appointments.

 Many temporary filling materials are available and the effectiveness of each to microleakage varies considerably. Much research has been undertaken into which is the most effective material, however, there still remains much controversy between researchers

 The microleakage of temporary restorative materials has been tested using several methods of investigation, including dyes, radioisotopes and micro-organisms. Investigations have been performed using temperature changes to try and simulate the “in vivo” situations.

 At the beginning of this century, studies were being performed on the sealing properties of temporary filling materials. One such study carried out by Grossman (1939), was designed to determine the permeability of temporary filling materials to methylene blue dye, saliva and test organisms (Oppenheimer and Rosenberg, 1979). In this study, the materials examined were temporary stopping, base plate gutta-percha, oxyphosphate of zinc cements, “Pro Tem”, and zinc-oxide/eugenol cement. Combinations of these materials were also tried, such as a double layer of gutta-percha, and a layer of oxyphosphate cement over the base plate gutta-percha (Grossman, 1939).
The author concluded that out of the temporary filling materials he tested “in vitro”, zinc phosphate cements showed the worst sealing properties, gutta-percha fillings were intermediate and zinc-oxide/eugenol cements the best. In fact, he demonstrated that zinc-oxide/eugenol showed no leakage and he attributed this finding to the expansion property of the material in the presence of moisture.

Following his research, Grossman (1939) recommended the use of zinc phosphate cement placed over gutta-percha to seal posterior teeth and for the anterior teeth, he recommended zinc-oxide/eugenol.

 Following Grossman’s (1939) study, Fischer (1949), using an iontophoresis technique found that copper-phosphate and silicate cements, gold inlays and foil, and acylates and amalgam all allowed a certain degree of infiltration.

 Armstrong and Simon (1951) also tested some of the above temporary cements using radiocalcium (Ca45). They also confirmed Fischer’s (1949) results.

 The effect of thermal stress on the microleakage of temporary filling materials was tested by Nelson et al (1952). They subjected their testers to the upper and lower limits of thermal tolerance of the oral cavity (60o C to 4o C) and found a crevice 10?m in diameter
could develop at the margin during the cooling phase. This crevice although very small is infact five to twenty times as large as the size of commonly found bacteria in the oral cavity (e.g. Streptococcus 0.5?m). This was found to be true when all the materials tested including zinc-oxide/eugenol and amalgam underwent thermal stress.

 Massler and Østrovsky (1954) carried out an “in vitro” study using glass tubes and a dye solution. They found marginal leakage within 24 hours with base plate gutta-percha, temporary stopping, zinc phosphate cement and acrylic resin. The study showed that silicate cements preserved their marginal seal for up to 13 days. Zinc-oxide/eugenol showed 2-3 mm penetration along the 5 mm wall of the test cylinder, and amalgam exhibited less than 0.1 mm penetration (Oppenheimer and Rosenberg, 1979).

The infiltration of colour-producing micro-organisms through the margins of acrylic and amalgam restorations was tested by Seltzer (1955). The tests were performed both at constant body temperature and after a temperature cycle. The author discovered that no infiltration occurred in the restorations maintained at constant body temperature. He did, however find that infiltration occurred in those teeth that underwent the temperature cycle.

 Hirsch and Weinreb (1958) investigated the cavity-sealing properties of silicate cements, acrylic filling materials and amalgam under conditions simulating those found “in vivo”. Their results showed that both the silicate cements and acrylic filling materials allowed infiltration following repeated temperature changes. The silicate cements also allowed this infiltration prior to the temperature changes.

The infiltration was attributed to the difference in thermal expansion between the tooth and the acrylic restoration. Of the materials tested, only amalgam maintained its good marginal seal after repeated temperature change (Parris and Kapsimalis, 1960).

 Going and associates (1960) used Crystal Violet and radioactive iodide (I131 ) in their study and tested the marginal infiltration of various temporary filling materials. The following year, Phillips et al (1961) used autoradiographs produced by Ca45. Both studies agreed with previous research in that zinc phosphate cement allows gross marginal leakage.

 Parris and Kapsimalis (1960) compared nine temporary filling materials (8 temporary and amalgam) in their study and were the first to evaluate the effect of temperature changes on the sealing properties of these temporary filling materials. The test was carried out at  room temperature and also after cycles of temperature
change (60 to 4º C).

 The ability of a 2% aqueous solution of aniline blue dye to penetrate the margins of the filled cavities was used as a means of comparing their cavity-sealing properties. This penetration was detected as a blue discoloration of cotton fibres placed beneath the test filling. Their results concluded that both zinc phosphate cement and zinc-oxide/eugenol showed marginal leakage when subjected to thermal stress thought to simulate “in vivo” situations. They found that only Cavit maintained an effective marginal seal.

 Marosky et al (1977) conducted a study for the purpose of comparing the sealing ability of several popular, commercially available products recommended for the temporary restoration of teeth undergoing endodontic treatment. The effects of time and temperature change on the materials was studied. The leakage patterns were demonstrated by using calcium chloride (Ca45) as the radioactive tracer to produce the autoradiograph.
 From the study, Marosky concluded that of the materials tested, two pre-mixed cements (Temp-Seal and Cavit) showed superior sealing ability, with Temp-Seal being the best overall. Premixed zinc-oxide/eugenol cement without an accelerator added provided the next best seal. Zinc phosphate, IRM and polycarboxylate showed significantly more leakage than the others. However, zinc phosphate, was superior to IRM and IRM showed less leakage than did the polycarboxylate cement (Marosky et al, 1977).

 Also in this year, Krakow et al (1977) undertook a study which contradicted previous studies and found that zinc phosphate cement allowed little or no leakage. In his study, the author used bacterial penetration in evaluating the seal of temporary filling materials “in vivo”. This method was also employed by Parris et al (1964), Blaney et al (1981) and Keller et al (1981).

 Friedman et al (1986) compared the sealing ability of four commonly used temporary filling materials using a radionuclidic model. This model involved studying the leakage of radiosodium from the pulp chambers of teeth into an external medium. Their research led them to conclude that zinc-oxide/eugenol based materials sealed better than calcium-sulphate based materials (e. g. Cavit-G) and that statistically significant differences were established between the sealing ability of the two types of materials.

 Pécora and Roselino (1982) developed a method for testing the dimensional stability of temporary filling materials. Their method involved the infiltration of Nickel ions through the walls of the access cavities into the root canal. Contact of these Nickel ions with a revealing solution (1% dimethylglyoxime) used to treat the paper points in the root canal, led to the formation of a red Nickel-dimethylglyoxime complex. It was the formation of this complex that was used to indicate whether infiltration occurred. In their study they tested three temporary filling materials; gutta-percha, zinc-oxide/eugenol and Cavit-W and subjected them to thermal stress. The application of this method produced results which led them to conclude that all the materials investigated allowed marginal infiltration between the dentine/material interface. gutta-percha showed the greatest dimensional alteration by permitting the greatest infiltration when subjected to temperature change. Cavit-W was shown to be the most dimensionally stable material when subjected to temperature change and Zinc-oxide/eugenol was intermediate in its dimensional stability, between gutta-percha and Cavit-W (Pécora and Roselino, 1982).

 In the years that followed, it seemed to be a common finding in the research that Cavit had superior sealing properties compared to other temporary cements. However, it can be seen that the majority of the studies performed involved testing the microleakage of the same group of materials namely, zinc-oxide/eugenol and calcium-sulphate based temporary filling materials.

 Cruz Filho et al (1996) designed an experiment based on the method developed by Pécora and Roselino (1982) to evaluate the dimensional stability of several synthetic temporary sealants “in vitro”. These sealants were based on polyvinyl resins and photopolymerised resins. The materials used were easily manipulated, but whether this was at the expense of the physical properties was to be determined. The study involved testing 70 recently extracted maxillary human canine teeth. A double seal was used with gutta percha and each of the cements (Cavit, Cimpat, Coltosol, Lumicon, Cavitec and Sermit).

The teeth underwent a 72 hour temperature cycle inorder to simulate the “in vivo” environment. The results were obtained using a method of classification developed by Pécora and Roselino (1986). They concluded from their study that not one of the materials tested was capable of preventing marginal infiltration during the time of the study.

 Much of the research carried out in the past has used the same basic methods and techniques. However, the techniques employed, still remain very limited and may have lead to the conflicting results in the research.

Purpose of the Study
 

 The purpose of this study was to verify the microleakage of four temporary filling materials, Cavit-W, Kalzinol, T.E.R.M. compules and IRM capsules “in vitro”, using the method devised by Pécora and Roselino (1982).
 
 
 

Materials & Methods
 
 

Tooth Preparation

 Forty recently extracted, non-carious mandibular and maxillary human canine teeth were randomly selected for this study. They were stored in 0.1% Thymol solution until the point of use. During the actual experiment, the teeth were kept dry and not stored in solution.

 All forty teeth were selected with previously prepared occlusal access cavities and the pulp extripated prior to the study.

 The working length of each tooth was estimated to be approximately 1 mm from the anatomical apex of the tooth measured using a size 15 k-flex file (Maillefer).

 Each tooth was then prepared endodontically using the Maillefer K-flex files, starting with a size 15 and proceeding up to a size 50 (15, 20, 25, 30, 35, 40, 45, 50) to the working length.

 During instrumentation, each tooth was irrigated using 15 ml of distilled water.

 Following the endodontic preparation, each tooth was coated all over to within a
2.5 mm circumference of the access cavity with cyanoacrylate resin (Super Bonder?), careful attention being paid to the apex. A second coat was then applied to the root surface and apex only. The purpose of this resin was to avoid infiltration of the nickel ions through lateral canals, the apex and any cracks present.

Preparation of Chemical Solutions

 A 1% alcohol solution of Dimethylglyoxime. P. A (VETEC) was made using 1g of material dissolved in 100 ml 96% alcohol solution.

 Forty cotton wool pledgets and paper points (HERPO) of various sizes were then placed in a petri dish containing this 1% Dimethylglyoxime alcohol solution. This petri dish was then placed at 37º C until all the alcohol solution had totally evaporated. The 1% Dimethylglyoxime alcohol solution, the paper points and the cotton wool pledgets impregnated with this alcohol solution are shown in figure 1.

Figure 1. The 1% Dimethylglyoxime alcohol solution, the paper points and the cotton wool pledgets impregnated with this alcohol solution.

  Next, a 5% solution of Nickel Sulphate (green) was made. A spot test was carried out to show that on contact of the Nickel Sulphate solution (green) with the dimethylglyoxime solution (colourless), a Nickel-dimethylglyoxime complex (red) would be produced.

 If the temporary sealing material suffers any dimensional alteration then the indicator Nickel Sulphate solution will penetrate the interface of the tooth and the filling material and will meet the cotton wool pledget impregnated with the 1% dimethylglyoxime alcohol solution, also referred to as the revealing solution (Pécora and Roselino, 1986) as follows:

5% Nickel sulphate  (Green) + 1% Dimethylglyoxime solution  (Colourless) = Ni-dimethylglyoxime (Red)
 

Figures 2. Spot test: In A and B above, one drop (20ml) of 5% Nickel Sulphate solution was placed.

Figure 3. A) 20ml of distilled water was dropped onto the filter paper, no colour change resulted. B) 20ml of 1% dimethylglyoxime solution was dropped onto the filter paper. On forming the Nickel-dimethylglyoxime complex, a red colour change resulted.
 Temporary Filling Materials

 Four commonly used temporary filling materials were used in this experiment.
 

Group 1. Cavit-W (Premier Dental Products Co/, Norristown, PA).
This product contains zinc-oxide, calcium sulphate, zinc sulphate, glycol acetate, poly-vinyl chloride acetate, triethylnolamine and a white pigment.

Group 2. Kalzinol (Dentsply-DeTrey).
This product is in a powder/liquid form, containing zinc-oxide/eugenol cement.

Group 3. T.E.R.M.TM  Compules?  Tips (L. D. Caulk Division).
This product is a visible light cure Endodontic Restorative Material.

Group 4. IRM?  capsules TM (L. D. Caulk Division).
This product is an Intermediate Restorative Material. It contains zinc-oxide/eugenol and is reinforced with polymethylmethacrylate.

The temporary filling materials used in the study are shown in figure 4.
 

Figure 4. The temporary filling materials used in the study.
 

 Manipulation of Materials

 One paper point impregnated with the 1% Dimethylglyoxime solution was carefully placed in each tooth to within approximately 2 mm of the anatomical apex. A cotton wool pledget also impregnated with the Dimethylglyoxime solution, was then placed above this paper point carefully making sure to leave 2.5 mm of the coronal access free for the temporary filling material.

 Four groups each containing 10 teeth were then prepared with each temporary cement according to the manufacturers instructions and then placed in a petri dish containing the 5% Nickel Sulphate solution and labelled with the appropriate group, for example, Group 1. Cavit W, 37º C.

 The four groups were then ready to undergo the temperature change cycle. They were placed in an oven at 37º C for 8 hours.

 The teeth then underwent a cycle during which they were placed at 37º C for
5 minutes, 7º C for 5 minutes, and 60º C for 5 minutes respectively. They were alternated through these temperatures for a total of 30 minutes. This cycle was performed every 8 hours and the whole process took a total of 72 hours. During the cycling process, the teeth were kept in the 5% Nickel Sulphate solution at all times.

 On completion of the temperature change cycle, the teeth were washed in tap water for one hour inorder to remove the Nickel ions from their surface. The temporary cement was carefully removed from each tooth. The cotton wool pledgets and paper points were removed and placed in a clean petri dish labelled with the appropriate group. The corresponding tooth was split longitudinally along its axis using a carborundum abrasive disc and placed next to its paper point and cotton wool pledget.

 A piece of gauze soaked in ammonium hydroxide (NH4OH) solution was placed in each petri dish in order to fix the colour on the pledgets and paper points.

 The microleakage of each tooth for each material was calculated from the colour change observed, using the method of classification described by Pécora and
Roselino (1986).

  Evaluation of the ionic infiltration was carried out in this form:
 

0-No appropriate colour change;
1-Colour change in the cotton wool pledget;
2-Colour change in the cervical region of the paper point;
3-Colour change to the middle of the paper point;
4-Colour change extending to the apex.

 The classification of the ionic infiltration is shown in figure 5.
 

Figure 5. Classification of the ionic infiltration.

Results

 The results obtained using the forementioned method of classification are shown in Table 1
 

 The photographs observing the microleakage are shown in figures 6, 7, 8 and 9.

Figure 6. The microleakage observed using Cavit-W temporary filling material.

Figure 7. The microleakage observed using Kalzinol temporary filling material.

Figure 8. The microleakage observed using T.E.R.M. Compules.

Figure 9. The microleakage observed using IRM Capsules.

  The Kruskal-Wallis statistical analysis test (GMC) was used to determine whether there was a significant difference in microleakage between the different temporary cements. The results of this test are shown in Table 2

 The Kruskal-Wallis test showed there to be no difference between the materials used in this experiment, but we continued the test and compared the materials two in two and this is observed in Table 3.

 The results suggest that there is a significant difference (a>0.05) between the materials Cavit-W and Kalzinol, and between Cavit-W and IRM capsules, but Kalzinol, T.E.R.M. and IRM capsules show no significant difference (a=0.05).

Discussion
 

 It can be seen from the data obtained during the study that not one of the temporary filling materials was ideal as all underwent microleakage to some degree following thermal stress.

 It has been reported that “in vitro” studies of microleakage should be regarded as setting a theoretical maximum amount of leakage that may or may not occur “in vivo”. There is generally a poor correlation between the extent of microleakage found “in vitro” and the clinical success of a material. However, if a material placed “in vivo” does not exhibit microleakage, there is a higher probability of clinical success than if it showed leakage “in vitro” (Pashley, 1990).

 Many studies have shown that Cavit provides a good seal to restore endodontic access cavities. One such study, carried out by Tamse, Ben-Amar and Gover (1982), showed that Cavit sealed better than IRM and Kalzinol. Our results agree with these findings although this material is by no means fool proof at preventing microleakage.
 One of the factors affecting the dimensional stability of the temporary filling material is its water content (Tamse, Ben-Amar and Gover, 1982). Cavit has a high linear expansion, probably caused by water absorption during setting. It is documented that the setting reaction for Cavit is initiated in part by saliva, the reaction of water with calcium sulphate and with zinc-oxide/eugenol sets hygroscopically (Oppenheimer and Rosenberg, 1979). This hygroscopic expansion enhances the contact between the material and the access cavity walls, and also produces a better seal (Widerman et al, 1971).

 However, it has been found that “in vivo”, Cavit has a high solubility and a disintegration value of 9.7%, leading to a rapid deterioration of the surface of the restoration producing the washed out appearance commonly observed in Clinical Practice, especially when used in complex endodontic access preparations (Anderson et al, 1989).

 It has been suggested in the past that at least a 3.5 mm thickness of Cavit should be used inorder to prevent leakage (Webber et al, 1978). As our study used only a 2.5 mm thickness, this could have enhanced the microleakage of this material.

 The Cavit-W used in the study was a single paste material. Mixing of the components was not necessary, thus limiting any discrepancy in the manipulation of the materials.

 According to the manufacturers instructions, a maximum incremental thickness of 4 mm of T.E.R.M. temporary filling material can be used. Thus, our study closely followed these specifications. However, microleakage was found to occur in this group. The cause of this infiltration is debatable. It could be due to the incremental thickness being too great so that not all of the material is cured with the visible light, or dimensional change could have occurred due to the temperature cycling process leading to contraction and expansion of the material, or the actual photocuring process itself, may have led to a slight contraction of the material towards the light, thus leading to the creation of a space between the material and the walls of the cavity, allowing infiltration of the Nickel ions.

 It has been shown that the seal of this material improved with time, but after a certain point microleakage did occur. Thus, following the manufacturers recommendations for the duration of the temporary dressing within the cavity is essential (Anderson et al, 1989).

 The zinc-oxide/eugenol temporary cements, i.e. Kalzinol and IRM capsules, both showed to be significantly different from the Cavit.
Previous studies also found the IRM capsules to permit significant microleakage before and after thermal stress (Anderson et al, 1990). The pre-measured capsules have a powder(P) to liquid(L) ratio of 5g/ml. If this ratio is reduced an excellent seal is obtained with only a small compromise to the physical properties (Anderson et al, 1990). It has also been reported that using these lower P/L ratios releases free eugenol. This eugenol has a good antimicrobial effect (Anderson et al, 1990).

 Like the single paste Cavit-W, the pre-measured IRM capsules prevent any variation in composition of the material and so omit manipulative variabilities. Kalzinol however, is a two component system requiring mixing of the powder and liquid. Although the manufacturers recommend specific P/L ratios there is much scope for error.

 The method used in this study (Pécora and Roselino, 1982) is very sensitive because the limit of identification of the Nickel ions by the 1% dimethylglyoxime is
0.16 ng (0.16 . 10-9 g; Feigl, 1958). The study has shown that not one of the materials investigated was able to impede microleakage, thus it is realised, that a single appointment to undertake root canal treatment is far superior than multiple appointments, due to the likelihood of re-infection.

Conclusion
 

 With the method used and the results obtained, it is possible to conclude the following:

1. Not one of the temporary filling materials was able to resist microleakage.

2. Cavit was found to show a significant statistical difference compared to Kalzinol and IRM capsules in 5%. The other materials, that is, Kalzinol, IRM capsules and T.E.R.M. compules are statistically of no importance in marginal leakage infiltration.

Summary

The dimensional stability of four temporary sealing cements was studied “in vitro” (Cavit-W, Kalzinol, T.E.R.M. compules and IRM capsules).

 The infiltration of a 5% Nickel Sulphate solution into the root canal through the walls of the access cavities and temporary filling materials was detected by the chemical reaction occurring between the above mentioned solution and a 1% dimethylglyoxime alcohol solution. This reaction involves a red colour change on forming a Nickel-dimethylglyoxime complex (Pécora and Roselino, 1982).

 The teeth were exposed to a 72 hour temperature cycle in order to simulate the
“in vivo” situation.

 With this method and the results obtained it is possible to conclude that not one of the temporary sealants investigated was capable of impeding microleakage at the interface of dentine/material during the time of the study.

 Resumo

Estudou-se “in vitro” a estabilidade dimensional de quatro materiais seladores provisórios sintéticos (Cavit-W, Kalzinol, T.E.R.M. compules e IRM em cápsulas).

Detectou-se a infiltração da solução de sulfato de níquel a 5% no interior do canal radicular através da cavidade de acesso obturada com os cimentos temporários por meio de uma reação química com a solução alcoólica de dimetilglioxima a 1%. Esta reação envolve uma mudança de cor devido à formação do complexo níquel-dimetilglioxima -vermelho- (Pécora & Roselino, 1982). Os dentes foram expostos à solução de sulfato de níquel a 5% por 72 horas, com ciclagem térmica simulando situação “in vivo”.

 Com base na metodologia aplicada e nos resultados obtidos, pode-se concluir que nenhum dos materiais seladores provisórios foram eficazes em impedir a infiltração na interface material/dentina.

References
 

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Anderson, R.W; Powell, B.J; Pashley, D.H: Microleakage of IRM used to restore endodontic access preparations. Endodontic Dent. Traumatol, 6: 137-141, 1990.

Bobotis, H.G; Anderson, R.W; Pashley, D.H; Pantera, E.A: A microleakeage study of temporary restorative materials used in endodontics. J. Endodontics, 15 (12): 569-572, December 1989.

Chohayeb, A.A; Bassio, M.A: Sealing ability of intermediate restorations used in endodontics. J. Endodontics, 11 (6): 241-244, June 1985.

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Pécora, J.D; Roselino, R.B: A study of the dimensional instability of temporary filling materials used in endodontics. Rev. Obras. Odont, 43 (2): 51-56, March/April 1986.

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