In vitro evaluation of marginal microleakage of class II bonded amalgam restorations using a dentin adhesive and a glass ionomer cement

Avaliação in vitro da microinfiltração marginal em restaurações de amálgama tipo classe II usando adesivo dentinário e cimento de ionômero de vidro

Materiais Dentários

In vitro evaluation of marginal microleakage of class II bonded amalgam restorations using a dentin adhesive and a glass ionomer cement^*

Avaliação in vitro

da microinfiltração marginal em restaurações de amálgama tipo classe II usando adesivo dentinário e cimento de ionômero de vidro

Edmêr Silvestre PEREIRA JÚNIOR^**

Maria Francisca Thereza Borro BIJELLA^***

Salete Moura Bonifácio da SILVA^****

Bernardo Gonzales VONO^*****

PEREIRA JUNIOR, E. S.; BIJELLA, M. F. T. B.; SILVA, S. M. B.; VONO, B. G. In vitro evaluation of marginal microleakage of glass II bonded amalgam restorations using a dentin adhesive and a glass ionomer cement. Rev Odontol Univ São Paulo, v. 13, n. 2, p. 103-109, abr./jun. 1999.

The purpose of this study was to evaluate in vitro the effectiveness of the dentin bonding system All Bond 2 associated with Resinomer (Bisco), and of Vitrebond (3M) glass ionomer cement fresh-mixed, both used in the bonded amalgam technique, to prevent short-term microleakage in class II cavities restored with Dispersalloy (Dentsply), an admixed alloy. The control group utilized the Copalite (Cooley & Cooley) varnish. Forty five sound human extracted premolars were used. Class II cavity preparations were made on the mesial and distal surfaces of non-carious teeth, with the gingival margins wall established 1mm under the cementum enamel junction. The specimens were divided randomly into three groups with thirty cavities in each group. The teeth were stored in distilled water for 24 hours and were thermocyled through 500 cycles in distilled water between 5°C and 55°C with a dwell time of 15 seconds. The apices and roots of the teeth were sealed. They were placed in a 37°C bath of 0.5% basic fuchsin dye for 24 hours. The teeth were washed in tap water for 24 hours and cut. The microleakage scores per restoration were averaged and three values of various test groups were subjected to the Kruskal-Wallis and Dunn test at a significance level of p < 0.05. The All Bond 2/Resinomer showed significantly less microleakage at gingival margins than the Vitrebond and Copalite lined to amalgam restorations. The Vitrebond fresh mixed, lined to amalgam restorations, showed significantly less microleakage than the Copalite lined to amalgam restorations.

UNITERMS: Dental amalgam; Dental leakage.

INTRODUCTION

Amalgam is the dental restorative material most used in direct posterior restorations. This statement has been repeated, due to the satisfactory properties of the material, such as high resistance, stability, excellent physical and mechanical properties, insolubility in oral fluids, low cost and easy manipulation^{4,5,9,14,17,25,27}.

However, the amalgam dental restorative material has certain disadvantages, such as nonadhesion to tooth structure, which forces the professional to use mechanical retention in the form of pins, posts or grooves to retain the amalgam restorations. These mechanical retentions provide adequate retention, but can lead to a weakening of the tooth structure^2,8,19. In deciduous teeth restorations it is even worse; they present a smaller enamel and dentine thickness, and a contact face, instead of a contact point, which increases the proximal box of the restoration, making it more fragile to fracture.

When exposed to the oral environment, the newly placed amalgam restoration is subjected to corrosion, and the products of this corrosion are deposited in the gap between tooth and restoration, resulting in reduced microleakage, during a long period of time. The high copper alloy does not contain the g₂ phase and does not form these corrosion products, allowing postoperative sensitivity, recurrent caries and potential pulpal involvement. This reaction, reported by KELSEY; PANNETON¹⁶ (1988) and ELEY¹¹, (1997) happens because the chlorine and the oxygen of saliva react with tin, and such elements attack the amalgam phase, mainly the g₂ phase, forming oxides of tin chlorides that penetrate in the tooth/amalgam interface. However, the high cooper content alloy possesses better physical characteristics when compared to the conventional alloy resulting in less border and body fractures, presenting a better clinical behavior.

The marginal microleakage can be defined as bacterias, fluids, molecules or ions penetration between the restoration and the cavity walls. The microleakage in the tooth/amalgam interface is one of the factors responsible for recurrent caries, post operative pain and pulpal pathosis, promoting the same failure type.

Application of copal varnish is used with the purpose of decreasing the marginal microleakage in the tooth/amalgam interface. Applied to the cavity walls, it is capable to prevent the initial marginal microleakage in the margins of the amalgam restorations^11,23, and eventually is replaced by amalgam corrosion products, as this varnish solubilizes.

Recently, adhesive resins have been used as cavity liners²⁷, presenting advantages such as the conservation of the dental structure, the absence of postoperative sensibility, the non usage of additional retentions, strengthening the remaining structure, and reducing the marginal microleakage^9,10,13,27, in class II restorations. The adhesive is capable to increase the amalgam restorations retention to the dental structure. IMPARATO et al.¹⁴ (1993) considered that the adhesive has a successful interfering potential in the adhesion of the amalgam to the dental structure in deciduous teeth. CHARTON et al.⁹ (1992) have also reported the elimination of marginal microleakage using dentin bonding agents in amalgam restorations.

The use of glass ionomer cements as liners/bases under amalgam restorations due to the fluoride release bond to dentine and enamel, present biocompatibility and low thermal expansion coefficient, reducing microleakage. If an adhesion could be formed between the amalgam and the glass ionomer liner, the restorations performance would be improved^1,4,21. The prevention of microleakage under amalgam restorations with the use of a glass ionomer cement base was studied by JENSEN et al.¹⁵ (1990), MANDERS et al.²¹ (1990) and RABSCHINKY; DONLY²⁵ (1993), and the authors concluded that there is an effectiveness of the glass ionomer cement liners in the control of the marginal microleakage and in the recurrent caries in amalgam restorations. BALDISSERA et al.⁴ (1993) evaluated the microleakage in amalgam restorations with several intermediary materials such as copal varnish, glass ionomer cement and sticker, and concluded that the Vitrebond base showed the smallest microleakage levels.

The purpose of this study was to evaluate and to compare the marginal microleakage in class II bond amalgam restorations lined with a dentin adhesive and with a glass ionomer cement. A traditional copal varnish was used for comparison.

MATERIAL AND METHODS

Forty five sound human extracted pre-molars (extracted by orthodontic reasons) were cleaned with a scaler, followed by a rubber cup prophylaxis with a slurry of water and pumice flour. After the extraction, the teeth were stored in a 1% thymol solution at 4°C to inhibit bacterial growth, for no more than six month prior to the use.

All 45 teeth were randomly divided in to 3 groups with 15 teeth in each one (30 cavities), summing a total of 90 cavities. In each group, a different intermediary material was used, according to the manufacturers specifications.

Each tooth was prepared with two class II cavities, 4.0 mm wide and 1.0 mm deep, one the mesial and distal faces. A #245 tungsten carbide bur in a high speed hand-piece with air/water coolant was used to prepare the cavities, 1.0 mm under the cementum enamel juntion. The teeth were mounted in blocks of gypsum and wax, with three teeth in each, to simulate the proximal contact. The groups were divided in:

Group I: Amalgam lined with Copalite - Cooley & Cooley (Control)

Group II: Amalgam lined with All Bond 2/Resinomer (Bisco)

Group III: Amalgam lined with the Vitrebond (3M) glass ionomer cement

In group I (control) the teeth were dried with filtered air and then received one coat of Copalite which was dried with filtered air. A second coat was applied and dried. Dispersalloy dispersed phase alloy was grinded in a high speed amalgamator following the manufacturs’ specifications, thoroughly hand condensed into the preparation, and carved to the preparation cavosurface margins.

In group II the enamel and dentin were etched with a 32% phosphoric acid gel (All Etch, All Bond 2 adhesive system) for 15 seconds. The acid gel was removed with water spray. Teeth in group 2 were dried with air for 1 or 2 seconds. One drop of primer A and one drop of primer B were mixed and applied into preparation. The primer was applied in 5 coats. After that the cavity was dried for 5 seconds and the All Bond 2 adhesive was applied in a uniform layer to the primed enamel and dentin. The adhesive was light-cured for 20 seconds with Optilux Demetron. After light-curing, while the amalgam was being triturated, one part of Resinomer base was mixed with one part of Resinomer catalyst. The Resinomer was a applied with a brush in a uniform layer to the cavity walls and the Dispersaloy alloy was condensed, and carved to the cavosurface margins of the preparation. After the removal of the steel stainless matrix the margins were light-cured for 20 seconds.

In group III the teeth were dried with air for 1 or 2 seconds. The Vitrebond glass ionomer cement was applied to axial walls and light-cured for 20 seconds with Optilux Demetron. After this coat a second coat of Vitrebond was applied in all cavities while the amalgam was being tritured. This second coat was applied in a thinner layer, using a small brush, to the untreated enamel and dentin parts of the cavity; this layer was not light-cured, as recommended¹. The amalgam was condensed over the plastic-phase glass ionomer cement. This glass ionomer cement is of dual-cure; the cure happens by chemical and base/acid reaction. After the removal of the stainless steel matrix, the margins were light-cured for 20 seconds.

The amalgam restorations used individual soft metal band matrix, 0.7 mm. Dispersalloy high copper alloy was tritured for 10 seconds in a Capmaster and condensed into the cavities using a small diameter condenser. The restorations were carvened with Hollembak 3S and burnished.

All specimens were then stored in destilled water at 37°C for 24 hours. After that, the root apices were sealed by a cavity preparation in each apex, coated with two coats Copalite varnish and filled amalgam to prevent dye penetration through the apex. The root surface was coated with two fingernail enamel layers 1.0 mm distant from the restoration margins. The teeth were thermocycled through 500 cycles between 5°C and 55°C in distilled water with a dwell time of 15 seconds in each bath and subsequently immersed in a 0,5% basic fuchsin dye aqueous solution at 37°C for 24 hours.

After immersion, the specimens were rinsed with tap water, and lightly pumiced to remove the superficial dye. The teeth were then longitudinally and mesiodistally sectioned through the restorations into three sections using a high speed diamond disc. Each section was then measured in micrometers in a x30 Mitutoyo microscope (instrument for very small and precise measurements) according to the extent of dye penetration at the tooth/amalgam interface (Figure 1).

FIGURE 1
- Scheme of the evaluation of dye penetration in each section at the gingival wall of the tooth/amalgam interface, using linear measurement in micrometer (Mitutoyo microscopic).

The mean microleakage values for the various test groups were subjected to the Kruskal-Wallis and Dunn multiple comparison tests at a significance level of p < 0.05.

RESULTS

Table 1 shows the microleakage results in this study. The All Bond 2/Resinomer (group II) dentin bonding system lined restorations demonstrated significantly less microleakage in dentin (gingival) than the other two groups. Copalite varnish (group I) showed significantly greater microleakage than All Bond 2/Resinomer (group II) and Vitrebond glass ionomer cement (group III). The Vitrebond glass ionomer cement (group III), showed significantly lesser microleakage than Copalite varnish and significantly more microleakage than All Bond 2/Resinomer.

TABLE 1
- Results of the Kruskal-Wallis test for three groups tested.

Figure 2 shows marginal microleakage mean values in each tested group, each intermediary material action could be observed.

FIGURE 2
- Mean microleakage of the three test groups.

Parameters of the KRUSKAL-WALLIS test shown in table 1, are extremely useful to decide if K independent samples come from different populations and if the mean differs among the populations or if there are cases to be expected among aleatory samples of the same population.

With H = 238.5, with 2 freedom degrees (used in the KRUSKAL-WALLIS test); it was accepted H₁ with HC(P) = 9.92.10^-53, there is evidence of significant differences among the groups averages.

With the DUNN test it was verified that all groups were different to each other (P < 0.05). There is significant difference among the groups: Copalite X All Bond2/Resinomer, Copalite X Vitrebond and Vitrebond X All Bond 2/Resinomer (Table 2).

TABLE 2
- Results of the Dunn multiple comparison individual.

* statistically different.

DISCUSSION

It is very difficult to compare the results of microleakage studies of dental materials when different techniques and procedures are used and the extent of the microleakage between the restoration and tooth structure depends on many factors.

The use of an adhesive resin used as a lining agent to amalgam has been suggested by STANINEC; HOLT²⁷(1988). The objective of bonded amalgam is to provide an adhesion between amalgam and tooth structure, and adhesive resins were proposed as the liners reduce the degree of microleakage that normally occurs at the interface between amalgam and tooth structure. The use of a bonding dentin as amalgam bonding agents has become a popular clinical pratice in the restorations of teeth with extensive caries and resultant loss of sound supportive tooth structure.

The high-copper alloy has been commonly used, because this alloy is superior to the conventional alloys. However, the high-copper alloy does not readily produce corrosion products at the interface due to the absence of the g₂ phase, exhibiting remarkable marginal microleakage. Consequently, the "self-sealing" property of these alloys is almost eliminated, and the use of intermediary material to reduce microleakage has been recommeded BEN-AMAR et al.⁷, (1995); LEINFELDER¹⁸ (1994) and POWELL; DAINES²³ (1987) since intermediary material provides a more effective sealing, when used with high-copper content.

The Copalite varnish has been the most recommended varnish in the literature to reduce microleakage in amalgam restorations^16,23. The results in table 1 for the group I are in agreement with the researches of COOLEY et al.¹⁰ (1991) and SAIKU et al.²⁶ (1993) in which that varnish resulted in significanty more microleakage than with other liners. Other works with very similar methodologies, differing from this study only in the used evaluation method, also showed that the varnish allowed a total marginal microleakage^3,13,17,27. CHARLTON et al.⁹, (1992); TANGSGOOLWATANA²⁹ also found results that support this study, even with quite different methodologies.

TORII et al.³⁰ (1989), evaluating the capacity of caries inhibition around bonded amalgam restorations, considered that the varnish presented 0.95 mm of dye penetration, and in the work was found a dye penetration of 1.035 mm. Although the methodologies of these works were different, the results for the copal varnish were similar. However, BEN-AMAR et al.⁸ (1994) presented different results from the present study; Copalite was not statistically different from the adhesive in periods of 14 days, six months and of one year of evaluation.

In the experimental group II, the use of the adhesive system All Bond 2/Resinomer in bond amalgam was effective in reducing microleakage of freshly placed amalgam restorations, as can be verified in figure 2. The results of the present study are in agreement with other studies^{9,10,13,17,27} where the reduction in the marginal microleakage of the gengival wall of bond amalgam restorations was higher than the control group, although the adhesives used were not the same as in the present study.

Even the works that used All Bond 2 without association to Resinomer, with the purpose of decreasing marginal microleakage in restorations of bond amalgam obtained smaller marginal microleakage with All Bond 2 and Amalgambond Plus when compared the other materials and the copal varnish. It can be stressed that there were no significant differences between the employed adhesives^2,17.

Adhesives that use load in their composition as Resinomer, have been promising. According to the results of the present study TANGSGOOLWATANA et al.²⁹, (1996) found that All Bond 2/Resinomer was the most effective adhesive, both in preventing the marginal microleakage and increasing the adhesion followed by Panavia 21. Although there are differences in methodology, the authors also used All Bond 2 associated to Resinomer, and according to them, the use of this adhesive material as middleman for amalgam restorations is suitable. The study of HOLLIS et al.¹³, (1996) also shows that All Bond 2/Resinomer followed by Detastic/Resiment and by Amalgambond Plus were the better adhesives in the marginal sealing, when compared to other adhesives.

In this study, besides of the materials previously mentioned, Vitrebond glass ionomer cement light-cured was used, according to the technic of ABOUSH; ELDERTON¹, (1991) and the suggestions of AL-MOAYAD et al.³; NOBILO et al.²², (1997) suggest that the glass ionomer cement is a good material for being used under the dental amalgam with the purpose of bonding this material to the dental structure.

JENSEN et al.¹⁵; (1990) MANDERS et al.²¹, (1990) PRATI et al.²⁴ (1994) and RABSCHINKY; DONLY²⁵ (1993) observed the good performace of Vitrebond glass ionomer cement, used as liner in the prevention of the marginal microleakage in amalgam restorations. Other researchers as LEINFELDER¹⁹ and GARCIA-GODOY; JENSEN¹² (1990) consider the glass ionomer cement as a great material for liner restorations, due to its fluoride release.

Glass ionomers cements, used as liners under amalgam restorations, are the most effective materials in reducing the appearing decays and preventing the marginal microleakage, when compared to the copal varnish^12,15,21,25. These data are supported by the results of this study (Figure 2).

BALDISSERA et al.⁴ (1993) evaluating the marginal leakage in amalgam restorations, using several liners, concluded that the glass ionomer cements Vitrebond and Chelon Silver were the best sealers, when compared to the adhesive system XR Bond. However, HOLLIS et al.¹³ (1996) considered the Fuji Duet glass ionomer cement less effective than All Bond 2/Resinomer in preventing the marginal microleakage, which is in agreement with the present study, although the used glass ionomer cement and methodologies are different and the authors didn’t verify statistically significant differences among the appraised materials.

It is important to stress that a material, before used in the daily clinic, has to be tested in experimental studies that simulate the conditions of the oral cavity. However, the main recognition of the effectiveness of the technique or of the restorative material is their long term clinical performance. The clinical evaluations of BEARN et al.⁵, (1994) BELCHER; STEWART⁶, (1997) STANINEC; LOWE²⁸ (1997) considered that the technique of the bond amalgam seems to be promising, and there are no long-term clinical evaluations. MAHLER et al.²⁰ (1996) don’t recommend bonded amalgam in traditional class I and II cavities until the effectiveness is demonstrated.

Other long term clinical researches are needed to demonstrate the materials effetiveness in bond amalgam restorations, regarding the marginal microleakage and the resistance and retention of the restorations. Also, it is important to study the use of bonded amalgam for restorating atypical cavities in deciduous teeth, where the conventional amalgam restoration cannot be used.

CONCLUSIONS

In our experimental conditions and in agreement with the used evaluation approaches, we conclude that:

1. all tested groups presented marginal microleakage;

2. the All Bond 2/Resinomer (group II) adhesive system and Vitrebond (group III) glass ionomer cement, used as liners in bond amalgam restorations, significantly reduced the microleakage at the gingival wall of class II fresh high-copper alloys restorations when compared to the lined Copalite varnish (group I);

3. the All Bond 2/Resinomer (group II) adhesive system, was more effective in the prevention of marginal microleakage when compared to the Vitrebond (group III) glass ionomer cement, and the difference was statistically significant.

PEREIRA JÚNIOR, E. S.; BIJELLA, M. F. T. B.; SILVA, S. M. B.; VONO, B. G. Avaliação in vitro da microinfiltração marginal em restaurações de amálgama tipo classe II usando adesivo dentinário e cimento de ionômero de vidro. Rev Odontol Univ São Paulo, v. 13, n. 2, p. 103-109, abr./jun. 1999.

O objetivo deste estudo foi avaliar in vitro a efetividade na prevenção da microinfiltração do sistema adesivo All Bond 2 associado ao Resinomer (Bisco), e do cimento de ionômero de vidro Vitrebond (3M), sem polimerização, em amálgama adesivo classe II, restauradas com Dispersalloy (Dentsply). No grupo controle utilizou-se o verniz cavitário Copalite (Cooley & Cooley). Para tanto, 45 pré-molares humanos íntegros e extraídos, com finalidade ortodôntica, receberam cavidades classe II, sendo uma na face mesial e outra na face distal de cada dente, com a parede cervical localizada a 1mm além da junção cemento-esmalte, sendo 30 cavidades em cada grupo. Após as restaurações os dentes foram estocados em água destilada por 24 horas, sofreram termociclagem em água destilada com 500 ciclos à temperatura de 5°C e 55°C, sendo de 15 segundos em cada banho. Após o selamento dos ápices e raízes, os espécimes foram imersos em solução de fucsina básica a 0,5%, à temperatura de 37°C por 24 horas, lavados em água corrente por 24 horas e sofreram o seccionamento. A microinfiltração marginal na parede cervical foi avaliada e os resultados analisados estatisticamente pelo teste de Kruskal-Wallis e de Dunn. Os testes estatísticos demonstraram que houve diferença estatisticamente significante entre os grupos experimentais e o grupo controle (Copalite), e entre o grupo do All Bond 2/Resinomer e grupo do Vitrebond. O sistema adesivo dentinário All Bond 2 associado ao Resinomer obteve porcentagem menor de microinfiltração marginal quando comparado ao cimento de ionômero de vidro Vitrebond.

UNITERMOS: Amálgama dentário; Infiltração dentária.

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29. TANGSGOOLWATANA, J.; COCHRAN, M. A.; MOORE, B. K. Microleakage evaluation of bonded amalgam restorations: confocal microscopy versus radioisotope. J Dent Res, v. 75, p. 22, 1996. Special issue. [Abstract n. 1235]

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Recebido para publicação em 13/05/98

Reformulado em 04/10/98

Aceito para publicação em 08/04/99

** Student of Pediatric Dentistry - Alfenas School of Pharmacy and Dentistry, Alfenas, Minas Gerais.

*** Professor, **** Doctor Professor e ***** Chairman of Pediatric Dentistry - School of Dentistry, University of São Paulo, Bauru, SP.

*

Thesis - Master degree.

Publication Dates

• Publication in this collection
  08 Dec 1999
• Date of issue
  Apr 1999

History

• Reviewed
  04 Oct 1998
• Received
  13 May 1998
• Accepted
  08 Apr 1999