Objectives: The purpose of this study is to report long-term bond strength (b.s.) data of an indirect composite resin, Belleglass^TM, bonded to metal, Captek^TM, after six month storage in 37 °C water with thermocycling.  Composite bonding to Captek^TM  is enhanced by the use of couplers, which are fine spherical, gold-coated particles, that provide micromechanical retention to the substrate surface.  Two versions of  Captek coupler, Ultimate Coupler Composite (UCC) and Ultimate Coupler Porcelain (UCP) were tested with Captek as a control (C).  Methods: The test method and short-term bonding data were presented in a previous paper, abst. # 581, J. Dent. Res. V.82, Special Issue A, March 2003.  For the six month data, eight samples in each substrate set were thermocycled 10,000X between 5-55°C before testing.  The results were analyzed by ANOVA to determine significant differences.  Means with the same letter are not statistically different at p<0.05.  Results:

	Adhesive Shear Bond Strength, MPa (S.D.)
	24 hours	30 days	6 months
Captek Control, C	17.1 (5.1)a	4.3 (2.4)c	3.9 (2.5)c
Captek + UCC	19.3 (2.3)a	19.6 (1.8)a	12.6 (2.1)b
Captek+ UCP	23.0 (3.5)a	21.6 (3.8)a	14.2 (2.4)b

 

There was significant reduction in b.s. in both UCC and UCP after six month storage in 37°C water with thermocycling.  Examination of the test specimens indicated that the failure mode did not change in UCP but some adhesive loss of coupler particles did occur in UCC.  In view of this, the reduction in b.s. is more likely attributed to water sorption in the composite.  The control had a low b.s. at six months similar to that at 30 days. 

Conclusion: There was significant reduction in b.s. in both UCC and UCP couplers after six months.    The micromechanical retention mechanism remained intact so the loss in b.s. is likely due to composite water sorption.