Influence Of Adhesive Systems On The Bonding Of Dental Amalgam To The Glass Ionomer ** Dr. R. Nageshwar Rao Prof. & H.O.D
* Dr. Ravikumar K. (Post Graduate)
Abastract Two adhesive systems All-Bond II Clearfill Liner Bond II were used to evaluate the bonding strength of amalgam to the glass ionomer. Glass ionomer cement was mixed into a paste and applied to the retentive cavity of acrylic matrix. Adhesives are prepared according to the manufacturer’s recommendation and applied on to the surface glass ionomer cement and amalgam was condensed over the adhesives with counter matrix in position. Bonded assemblies were stored in 24 hour and 30 days period in 37 degree and 100% humidity. Specimens were loaded in tension to failure on a universal testing machine with a cross head speed of 6mm per min. the result obtained were analysed statistically and mean tesnile strength was compared with two adhesives and two different storage periods. There was no significance change observed. The adhesive systems between amalgam and glass ionomer cement in this study proved to be useful in providing retention for amalgam restorations.
Influence Of Adhesive Systems On The Bonding Of Dental Amalgam To The Glass Ionomer Introduction The development of restorative bonding materials used in posterior teeth has not met all necessary conditions to be considered an ideal dental restorative technique. Amalgam has served effectively as a dental restorative material since its introduction. It has many advantages, including ease of manipulation, long clinical service, and low cost, compared with most other materials. However amalgam has got its own set of disadvantages, such as its colour, possible mercury toxicity. In particular, lack of adhesion to tooth structure is the short coming that has omitted its effective use in certain situations. With falling level of dental carious in the population and ja greater awareness of the shortcomings of restorations in carious management. The dental profession is becoming more aware of the need to define precise criteria for placing or replacing restorations. At the same time cavity design and perception of the requirements of cavity preparation continue to evolve and there appears to be a global trend towards the teaching of increasingly conservative cavity preparations. This relates partly to the greater use of adhesive systems for restorative procedures involving a variety of materials. Glass ionomers are being used increasingly as liner/bases under amalgam restoration as they leach fluoride, bond to dentin, and have a low coefficient of thermal diffusivity. If an adhesive bond could be formed between the amalgam and the glass ionomer then the performance of amalgam restorations might be improved further. The purpose of this study is to evaluate tensile bond strength of the amalgam to the glass ionomer under the influence of two adhesive systems All-Bond II (Bisco Dental) and Clearfill Liner-Bond II.
Materials and method Materials use were 1. Glass ionomer cement (Fuji II) 2. ALL-Bond II adhesive (Bisco dental) 3. Clearfill Liner Bond II (Kurray Co.) 4. Zinc free high copper amalgam alloy (DPI Non-Gamma-2) Twenty eight experimental samples were divided in to two groups: 1. All Bond II and 2. Clearfill Liner Bond II of this seven repetition of each for 24 hour and 30 days storage period. The glass ionomer was prepared in accordance with the manufacturer’s instructions. (The standard powder to liquid is 2.7/1.0 gm one level scoop of powder to one drop of liquid). The mix was applied to the interior of a retentive cavity of a clear acrylic matrix (2mm height and 5x5 mm area) Acrylic counter matrix was adopted to the matrix to provide 1mm of overlap in the height of the glass ionomer cement test specimen. The glass ionomer cement was cured for 20 min. The adhesive systems All-Bond II and Clearfill Line Bond II were manipulated according to the manufacturer’s recommendations and applied on the glass ionomer cement. Before the initial set matrices were juxtaposed and the dental amalgam was immediately condensed. Silver amalgam alloy and mercury were proportioned at 1:1.1 in weight in accordance with the manufacturer’s recommendations and then mixed for 10 sec with a mechanical mixer (Degussa) and a standard technique was used to manually condense the amalgam triturate on to the adherent surface of the glass ionomer cement. After 24 hour and 30 day storage period in an environment of 37 degree and 100% relative humidity. The samples were tested in a Universal Testing Machine at cross head speed of 6mm
per minute. The test specimen was loaded in tension to failure and bond strength was calculated from the load required to cause de-bonding divided by the area of the adherent surface. Results The table no. 1 and 2 represents the mean tensile strength value of the two different adhesive systems. According to the storage period of bonded assembly. To compare between the two adhesives and storage period student t-test was applied to test significance difference between two material and storage periods. It has showed that there is no significance difference between 24 hour and 30 days storage period on two adhesives separately at 5% level significance (p>0.05) and also between adhesives on 24 hour and 30 days showing statistically non significant difference at same level of significance (p>0.05) as shown in the table. Table No. 1: Comparison of means of tensile strength between 24 hour and 30 days by two adhesive materials separately (In Kilograms / Square cm.) Material
Days
Mean
S.D.
t-value
p-value
Significance
All Bond II
24 hrs
33.3586
2.0893
1.6277
>0.05
NS
30 days
34.9529
1.5329
24 hrs
32.9227
1.6617
1.2537
>0.05
NS
30 days
34.3214
2.4393
Clearfil Liner Bond II
Table No. 2: Comparsion of means of tensile bond strength between two adhesives by 24 hours and 30 days period (In Kilograms / Square cm.) Days
Material
Days
Mean
SD
t-value
p-value
Significance
24
All Bond II
24 hrs
33.5386
2.0893
0.4318
>0.05
NS
Clearfil Liner Bond II
30 days
32.9227
1.6617
All Bond II
24 hrs
34.9529
1.5329
0.5799
>0.05
NS
Clearfil Liner Bond II
30 days
34.3214
2.4393
30
Discussion In case of deep carious lesion which are to be restored with dental amalgam restorations cement base are provided to act as thermal insulations. There are various types of materials are used as base for amalgam restorations. Presently glass ionomer cements are being used as a base. By using glass ionomer we can achive some retention for amalgam. Recently as the adhesive systems are findings more applications in the dental restorative procedure, like in case of large carious lesions which are to be restored with amalgam restorations. Removal of carious will not always result in a cavity preparation with enough resistance and retention form to hold the amalgam effectively in the cavity. A procedure that All Bond II and Clearfill Liner Bond II adhesive to promote silver amalgam bonding to the tooth has recently been used and results demonstrated a bonding strength similar to those obtained from composites. There are studies conducted by Mauro A. De. Arrodo. Nobillo and Y.E.Y. Aboush., R.J. Elderton on bonding amalgam to the glass ionomer using adhesives. In evaluating influence of adhesives in bonding amalgam to glass ionomer our study showed no significant difference between All-Bond II adhesive and Clearfill Liner Bond II adhesive and also no significant difference obtained in comparing these adhesives with 24 hour storage period and
30 days storage period. It has been reported by Stainec M. Holt M. that the bonding mechanism of adhesives to metallic structures consists of mechanical retention and chemical interaction through hydrogen bridges and same mechanism of bonding reported with bonding dental amalgam. This can be explained through the development of large cement tag formation with the amalgam structures. When it is condensed in the cavity while the adhesive cement is still plastic demonstrates that mechanical interlocking occurs. Ideally these adhesives are developed in accordance with heterogeneous tooth structures consisting of organic and inorganic material where as glass ionomer presents homogenous surface for these adhesives when different adhesives systems are used. It may be due to this factor that there was no significant difference obtained in the tensile strength between the two adhesive systems when used between amalgam and glass ionomer. When the glass ionomer powder and liquid are mixed to form paste calcium aluminium sodium and fluoride ions are leached into the aqueous medium. The polyacrylic chains are cross linked by the calcium ions and forms a solid mass within 24 hours a new phase forms in which aluminium ions become bound within the cement mix. This leads to a more rigid set cement. During this maturing process if adhesives are applied, water that is being used as the medium may slowly hydrates both cross linked matrix and part of the adhesives simultaneously there by increasing the adhesive strength between glass ionomer and adhesives. Conclusion Bond can be achieved with the help of adhesive systems which may enhance the retentive ability of amalgam restorations thus in near feature it might be possible to recommend even more conservative cavity designs using glass ionomer and amalgam in combination with adhesives to achieve better results.
References
1. Maure Antonio de Arruda Nobilo, Simonides Consani MS, and Mario Fernando de Goes. Influence of adhesive systems on the bonding of dental amalgam to glass ionomer cement. J. Prosthet Dent. 1997; 77:127-30. 2. Y.E.Y. Aboush, and R.J. Elderton. Bonding dental amalgam to a lightcuring glass-ionomer liner/base. Br. Dent. J., 1991; 170-219. 3. Anusavice K.J. (ed) Quality evaluation of dental restorations. Pp 411-415. Chicago; Quintessence Publishing, 1989. 4. Smith D.C., Ruse N.D. Acidity of glass ionomer cements during setting and its relation to pulp sensitivity. J. Am. Dent. Assoc. 1986; 112 : 654-657. 5. Stainec M., Holt M. Bonding of amalgam to tooth structure: Tensile adhesion and microleakage tests. J. Prosthet. Dent. 1988; 59: 397-402. 6. Lacy A.M., Staninec M.A. The bonded amalgam restoration. Quintessence Int. 1992; 8 : 259-264.