Vol 21 No. 1

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J Bagh College Dentistry Vol. 21(1), 2009 The effect of amalgam… Fifteen minutes after condensation, the copper bands were carefully dislodged and removed. Samples Testing. After storage in distilled water at room temperature for 48 hours, the specimens were tested for tensile bond strengths between amalgam cylinders and dentin using a Zwick Universal Testing Machine with a loop attached to amalgam at cross head speed of 5 mm/minute until the amalgam separated from the tooth under the vertical retraction that was exerted on the bulk of the amalgam cylinders. The failure loads were in kilogram and transferred into Newtons by multiplying the value by 9.8 and divided it into the corresponding interface surface area in (mm 2 ) to get the tensile bond strengths in Mega Pascal (Mpa). RESULTS Tensile Bond Strength Values. The mean values and the standard deviations of the tensile bond strength (TBS) of each group are presented in table 1. By using the student-test for the Scotchbond Multi-Purpose group; the SBS mean value of hand condensation of amalgam was higher than that of mechanical condensation and the difference was highly significant (p
J Bagh College Dentistry Vol. 21(1), 2009 The effect of amalgam… mechanism for such adhesive to amalgam is micro-mechanical type that depends on the film thickness of the adhesive. Hand condensation effect may be more obvious than the mechanical condensation under these circumstances. Similarly, for the control groups, there was no bonding mechanism between the amalgam and dentin just the micro-mechanical adaptation enhanced by heavy hand condensation. This attribution is supported by the classic studies and recent reports about the hand condensation effects and the bonding mechanism of recent dentin bonding agents to amalgam (14). Sweeney (15) , Jorgensen (16) , and Mjor (17) contributed to such researches. Some of them found that the hand condensation performed better in reducing porosities at amalgam / dentin interface and it had better adaptability. Others reported that there were some kinds of mechanical interlocking between amalgam particles and dentin irregularities even that the self-sealing criteria of amalgam was not started yet . The Syntac adhesive / primer has 4-META and HEMA co-monomers that may bond the amalgam chemically and micro-mechanically. This “real” bonding may show the obvious effect of mechanical condensation to enhance the bonding of amalgam to dentin. This explanation is supported by the findings of Chapman & Crim (12) , which had already mentioned. The Use of Dentin Bonding Agents. For both types of condensation techniques and under the conditions of this study, there was highly significant difference between the different types of adhesives used on the one hand, and between the groups with the bonding treatment and that without bonding treatment (controls) on the other. These results are in agreement with several studies. Zardiackas & Stoner (2) , Shimizu et a1 (3) , and Varga et a1 (4) showed that the bonding of amalgam to tooth structure was possible under laboratory conditions with higher over the unbonded one . In addition, numerous clinical studies had reported favorable results, which were obtained when using amalgam bonding approach. Those studies were done by Summitt et a1 (18) , Setcos et a1 (19) , and Belcher & Stewart (35) . These results support the finding obtained by this about the bonding of amalgam to dentin by using dentin adhesive systems and with higher TBS than that of the controls. The differences in the bond strengths different generations of dentin binding agents have been shown in various studies. Under the circumstances of this study, the Syntac adhesive showed higher TBS to dentin than the Scotchbond Multi-Purpose. This finding is in agreement with that of Retief et a1 (14) , although the TBS values were higher than those of this study. However, Chappell & Eick (22) and Holtan et a1 (23) found that the Scotchbond Multi-Purpose had significantly better bond strength between the amalgam and dentin than the Syntac and Scotchbond Multi-Purpose may be due to the different chemistries of these bonding systems , although some similarities do exist. The similarity found in the pretreatment procedure in using the same chemical composition etchants 9355 phosphoric acid). The Scotchbond Multi-Purpose primer contains HEMA and polyalkenoata copolymer and the adhesive contains BIS-GMA and HEMA (14) . The Syntac-one bottle-contains 4- META and HEMA (24) . Examinations with an electron microscope have shown that the hydrophilic monomers connect with both organic dental hard tissue by forming ion complexes with calcium ions of enamel and dentin and hydrogen bridges with collagen fibers of dentin (25) . This complicated connection may be the reason for such higher TBS values obtained in this study over the Scotchbond Multi-Purpose. REFERENCES 1. Fayyad MA, Ball PC. Cavity sealing ability of lathecut, blend and spherical amalgam alloys: a laboratory study. Oper Dent 1984; 9: 86-93. 2. Zardiackas LD, Stoner GE. Tensile and shear adhesion of amalgam to tooth structure using selective interfacial amalgamation. Biomaterials 1983; 4: 9-13. 3. Shimizu A, Ui T, Kawakami M. Bond strength between amalgam and tooth hard tissues with application of fluoride, glass ionomer and adhesive resin cement in various combinations. Dent Mater 1986; 5: 225-32. 4. Varga J, Matsumura H, Masuhara E. Bonding of amalgam filling to tooth cavity with adhesive resin. Dent Mater 1986; 5: 158-64. 5. Staninec M, Holt M. Bonding of amalgam to tooth structure: tensile adhesion and microleakage tests. J Prosthet Dent 1988; 59: 397-402. 6. Edgren BN, Denehy GE. Microleakage of amalgam restorations using Amalgambond and copalite. Am J Dent 1992; 5: 296-8. 7. Clinical Research Associates: Adhesives: Silver amalgam. Clinical Research Associates Newsletter. 1994; 18: 2-3 cited by Ratananakin T, Denehy GE, Vargas MA. Effect of condensation techniques on amalgam bond strengths to dentin. Oper Dent 1996; 21: 191-5. 8. Philips RW. Dental amalgam alloys: Amalgam structures and properties and Chapter 18, Dental amalgam: Technical condensations. In skinner’s science of Dental Materials, 9 th ed. Philadelphia : W. B. Saunders Company , P. 303-25 and 327-47, 1991. 9. Craig R G. Restorative Dental Materials. 8 th ed. St. Louis: C. V. Mosby , P. 214-47, 1990. Restorative Dentistry 36
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