Indian Journal of Dental Research

: 2011  |  Volume : 22  |  Issue : 2  |  Page : 252--255

Microleakage of bonded amalgam restorations using different adhesive agents with dye under vacuum: An in vitro study

Abhishek Parolia, M Kundabala, Vaibhav Gupta, Mudita Verma, Chandni Batra, Ramya Shenoy, N Srikant 
 Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences, Mangalore Manipal University, Karnataka, India

Correspondence Address:
Abhishek Parolia
Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences, Mangalore Manipal University, Karnataka


Aim: In an effort to minimize tooth preparation, yet provide additional retention to compromised tooth structure, bonded amalgam restorations were introduced. Various resin-based adhesives have been tried earlier under bonded amalgam restorations. Still there are controversies regarding the outcome of bonded amalgam restorations regarding their adaptability to the tooth structure and microleakage. Therefore, this study was undertaken to compare the microleakage of bonded amalgam restorations using different adhesive materials. Materials and Methods: Standard Class I cavities were prepared on occlusal surfaces of 60 human molars. Teeth (n=60) were divided into three groups according to the material employed, as follows: group I: amalgam with glass ionomer cement (GIC) (type I); group II: amalgam with resin cement (Panavia F 2.0) and group III: amalgam with Copalex varnish as a control. Following restoration, the teeth were submitted to thermal cycling. The teeth were subsequently immersed in 2% rhodamine B dye under vacuum for 48 hours and sectioned to allow the assessment of microleakage under stereomicroscope. Results: The values were tabulated and the results were statistically analyzed using analysis of variance (ANOVA), Tukey«SQ»s post hoc test and Kruskal-Wallis test. Amalgam with type I GIC showed the least leakage with no statistically significant difference (P value 0.226) when compared to amalgam with Panavia F 2.0 and amalgam with varnish (P value 0.107). Conclusion: It can be concluded that bonded amalgam with type I GIC is a good alternative to amalgam with resin cement (Panavia F 2.0) and amalgam with varnish for large restorations, with the added advantages of GICs. Clinical Significance: Bonded amalgam restorations prevent over-preparation and reduce the tooth flexure. GIC type I under amalgam provides chemical bonding in between amalgam and tooth structure and thus reduces the microleakage.

How to cite this article:
Parolia A, Kundabala M, Gupta V, Verma M, Batra C, Shenoy R, Srikant N. Microleakage of bonded amalgam restorations using different adhesive agents with dye under vacuum: An in vitro study.Indian J Dent Res 2011;22:252-255

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Parolia A, Kundabala M, Gupta V, Verma M, Batra C, Shenoy R, Srikant N. Microleakage of bonded amalgam restorations using different adhesive agents with dye under vacuum: An in vitro study. Indian J Dent Res [serial online] 2011 [cited 2022 Dec 6 ];22:252-255
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Full Text

Dental amalgam has been used successfully for almost 200 years as a restorative material. Despite the poor esthetic characteristics and potential mercury exposure, this material still provides strong, durable and the best cost-effective direct posterior restoration. [1] However, amalgam in complex restorations shows some disadvantages which include microleakage, lack of adhesion to the tooth structure and post-operative sensitivity. [2],[3],[4] The use of boxes, locks, channels, or pins for added retention in large amalgam restorations requires the removal of additional tooth structure and weakens the remaining enamel and dentin. In an effort to minimize tooth reduction, yet provide additional retention to compromised tooth structure, bonded amalgam restorations were introduced in the late 1980s. In the bonded amalgam technique, a dentin bonding system is used in conjunction with a viscous resin liner. The viscous liner physically mixes with the amalgam and forms chemical as well mechanical union to enhance the amalgam's retentiveness to tooth structure. [5],[6] Bonded amalgam restorations seem to offer many advantages like its substantial ability to retain amalgam without compromising tooth structure, a reduction of initial postoperative sensitivity, microleakage and reduction of cusp flexure. [7],[8],[9],[10],[11] Though there are controversies regarding the outcome of bonded amalgam restorations regarding its adaptability to the tooth structure and microleakage, [12] still various studies support the use of bonded amalgam restoration in large cavities for added retention. [13],[14] To obtain the best outcome of bonded amalgam restorations, the tooth surface must be well prepared to assure the adaptability of the adhesive and the amalgam, the adhesive must be strong and resistant to breakdown and the amalgam must be selected wisely and correctly manipulated to expect long-term service. Various adhesives have been tried earlier under bonded amalgam restorations. [15],[16] Hence, the purpose of this study was to compare the microleakage between bonded amalgam restorations using different adhesive materials with dye under vacuum.

 Materials and Methods

Sixty human molar teeth were selected in the present study. The teeth were examined under magnification to ensure that they were free of any fracture, caries or any structural defect. The teeth were cleaned and stored in 0.5% thymol at room temperature. Class I cavities on the occlusal aspect of these teeth were prepared using a high-speed hand piece with air-water spray and a # 245 carbide bur. Cavity dimensions were 4Χ6Χ3 mm with a flat pulpal floor, smooth and flat lateral walls with slight convergence occlusally, a 90° cavosurface angle (butt joint) and well-defined internal line angles. Each preparation was cleaned with air-water spray from triple syringe for 10 seconds and air dried. Then, the teeth were randomly divided into three groups (20 teeth each) according to the adhesive used under amalgam restoration as follows.

Group I: Cavities were conditioned with polyacrylic acid for 20 seconds. Powder and liquid of glass ionomer cement (GIC) (Type I) (GC corporation, Tokyo, Japan) were mixed in a luting consistency and a thin layer was applied to the cavity using an applicator.

Group II: Panavia F 2.0 (Kuraray Medical Inc., Okayama, Japan) self-etching primer was applied to the enamel and dentin and cured. Panavia F 2.0 cement was mixed and applied in a thin layer to the entire cavity using a brush.

Group III: Copalex varnish (Dentsply India Pvt. Ltd.) was applied in two thin layers, allowing the first layer to air dry for 30 seconds prior to applying the second layer.

Following the application of these adhesives, amalgam [admixed dispersed phase alloy powder (Dentsply India Pvt. Ltd.) triturated with mercury (Deepak Enterprise, Mumbai, India) in an amalgamator (Dentomat, Degussa, Brazil)] was condensed into the cavities before the adhesive materials set. Amalgam was condensed in horizontal increments using Ward and Hollenback condensers before setting of the adhesive materials. Carving was performed using 3S Hollenback carvers. In group II after restoration, light curing procedure was performed with a light curing unit (SmartLiteΤPS, Dentsply DeTrey GmbH, Germany) with a light intensity of 600 mW/cm2. All the restored teeth were stored at 37°C in 100% relative humidity for 24 hours before finishing and polishing. The teeth were thermocycled 500 times between 5°C and 55°C with a dwell time of 1 minute at each temperature. The root apex of each tooth was sealed with resin composite (3M ESPE, St. Paul, MN, USA). The entire surface was then painted with two coats of nail varnish, except for the restorations and the 1.0 mm surrounding them. The specimens were immersed in 2% rhodamine B dye solution and placed under vacuum pressure of 75 torr and allowed to remain in the dye for 48 hours. After exposure to the dye, the samples were rinsed with running water to remove the dye and the nail varnish was gently removed with a sterile #15 disposable scalpel blade (Lister, India). The specimens were then sectioned longitudinally with a water-cooled diamond saw. The dye leakage was assessed and graded by two calibrated examiners using a 30Χ stereomicroscope (Olympus) and the depth of penetration was measured using an ocular micrometer. The dye penetration was analyzed qualitatively according to 0-3 scale (0 = no dye infiltration; 1 = dye penetration up to one-third of the cavity depth; 2 = dye penetration up to two-thirds of the cavity depth; 3 = dye penetration up to the pulpal floor) and quantitatively in millimeters. [15]


The experimental data were subjected to statistical analysis using analysis of variance (ANOVA), Tukey's post hoc and Krukal-Wallis tests. All statistical testing was performed at significance level P<0.05. Specimens in group I (amalgam with type I GIC) showed less leakage (mean leakage 1.52 mm) with no statistically significant difference with group II (amalgam with Panavia F 2.0) (1.96 mm) and group III (amalgam with varnish) (2.06 mm). Specimens in group II showed less leakage than specimens in group III, but there was no statistical difference [Table 1] and [Table 2]. 40% of specimens in group I, 10% in group II and 25% in group III showed dye penetration up to one-third of the cavity depth, while 20% in group I, 35% in group II and 20% in group III showed dye penetration up to two-thirds of the cavity depth, and 40% in group I, 55% in group II and 55% in group III showed dye penetration up to the pulpal floor [Figure 1].{Table 1}{Table 2}{Figure 1}


The ultimate goal of any restoration is to preserve the vitality of the underlying pulp tissue. Microleakage has been identified as a significant problem with amalgam because of interfacial gap formation which can result in tooth discoloration, pulp irritation and secondary caries. [17] Conventionally, copal varnish liner has been used under amalgam restoration to reduce microleakage, [18] but its effectiveness to provide long-term seal is still a concern. [19] Several studies have demonstrated better sealing using adhesive liners than copal varnish under amalgam restorations due to the improvement in bonding between amalgam and tooth structure. [16],[20],[21],[22] In the present study specimens restored with amalgam and type I glass ionomer cement (GIC) showed the least leakage among all the other specimens though it was not statistically significant. Type I GIC is chemical-curing cement, during the condensation of amalgam when the cement is still in early stage of setting flows moderately and intermingles with amalgam. Therefore, it provides both mechanical interlocking with amalgam and chemical bonding with the tooth structure. [23] It has been found that it can also bond to metallic oxide, such as tin oxide and silver oxide. Since tin and silver are the components of dental amalgam, the bonding of freshly mixed glass ionomer to newly mixed amalgam can be expected. [24] The other added advantages of GIC are: fluoride release over a long period of time which prevents the occurrence of secondary caries, good compatibility with the pulp tissue, ease of manipulation, is cost-effective and additional curing unit is not required. Specimens restored with Panavia F 2.0 and amalgam showed lesser leakage than amalgam with varnish. These findings in the present study support the findings of previous studies in which Copalex varnish has been compared to resin-lined amalgam restorations. [16],[17] Panavia F 2.0 is a self-etching, self-adhesive, dual-cure, fluoride releasing resin cement. It contains sodium benzene sulfinate in the Primer B component and a proprietary sodium aromatic sulfinate in the universal paste of the resin cement to ensure that optimal polymerization of the cement occurs under an acidic environment. [25] Panavia F 2 provides mechanical bonding with amalgam and micro-mechanical with the tooth structure by forming a hybrid layer. In the present study, Panavia F 2.0 has been used first time as an adhesive liner in bonded amalgam restoration to get the benefit of its properties such as good bonding to tooth structure and fluoride release. Still, there are some disadvantages of resin-based adhesives such as high cost, need for an additional light-curing unit, increased technique sensitivity and polymerization shrinkage. Along with this, there are other multiple factors such as size of the condenser, the force of condensation, the choice of dental amalgam, the size of increment, the geometry of the preparation, strength of adhesive liner, film thickness of adhesive liner and the strength of bond between the adhesive and the tooth as well as amalgam which may affect the outcome of bonded amalgam restorations. [26],[27],[28] Various techniques have been used to evaluate microleakage, such as dye penetration, [29] bacterial leakage, [30] electrochemical method, [31] fluid filtration, [32] radioisotope labeling, [33] and scanning electron microscope analysis. [34] Among these techniques, dye penetration is the method most widely used to assess microleakage because of its sensitivity, ease of use, and convenience. [35],[36] Studies have reported that vacuum pressure decreases the volume of the entrapped air and allows complete dye penetration. [37],[38] Hence, in the present study, dye leakage under vacuum was performed for assessing the microleakage of the specimens. Rhodamine B dye was used in the present study because it presents greater diffusion on human dentin. [39] According to Francci, [40] its molecules are nanometric and are optimal to simulate enzymes and toxins of leakage resulting from bacterial metabolism. According to Azoubel and Veeck, [41] rhodamine B dye should be used in leakage studies because of its small particle size, ease of visualization, and large dissemination into dentinal tubules.

Clinical significance

Bonded amalgam restorations prevent over-preparation and reduce the tooth flexure. GIC type I under amalgam provides chemical bonding in between amalgam and tooth structure, thus reducing the microleakage.


In the present study, type I GIC as an adhesive liner in bonded amalgam restoration has shown comparable results to Panavia F 2.0 and varnish. Therefore, type I GIC can be considered an appropriate adhesive liner in bonded amalgam restorations to reduce microleakage, with its additive beneficial properties.


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