Introduction: A resin-paint has been developed to modify the shade of completed resin composite prostheses at chair side. This study evaluated the bond strength of the resin-paint to a prosthetic resin composite after cyclic thermal stressing. Materials and methods: The resin-paint (Master Palette, Kulzer) used was a flowable resin containing 40wt% fillers. A resin composite (Dentacolor Sirius, Kulzer) was photo-polymerized into a disc shape (10mm diameter, 3mm high). Bonding surfaces of the disc specimens were polished with a 600-grit Si-C paper and pre-treated with; 1) immersion in methylene chloride (MC), 2) airborne particle abrasion with 50µm aluminum oxide (AB), 3) application of C＆B liquid (Kulzer) after AB (CB), and 4) application of EG-bond (Sun Medical) after AB (EG). A piece of tape with 5 mm diameter opening was used to provide bonding area. The resin-paint was applied (0.5 mm thick) and photo-polymerized, then Dentacolor Sirius was photo-polymerized (6mm diameter, 2.0mm thickness) onto it as a loading handle. Shear bond strengths were measured at a 1.0 mm/min crosshead speed before and after thermo-cycling (4-60℃, 50,000cycles). All data were statistically analyzed by 2-way ANOVA and Scheffe’s F-test (p<0.05). Results: The shear bond strengths for each group are presented in the table. Bond strengths of groups CB and EG were significantly higher than that of group AB after 50,000 thermo-cycles (p<0.05). Conclusions: Applications of C＆B liquid and EG-bond after airborne particle abrasion are effective to obtain better bonding of the resin-paint.

Table. Shear bond strengths of each group; Mean (SD), Unit: MPa, n=5.

	MC	AB	CB	EG
Before thermo-cycling	6.0 (2.2)	17.9 (2.2) a, b	22.9 (2.2) a, c	20.3 (2.1) a, d
After 50,000 thermo-cycles	0	14.5 (1.9) b	18.6 (2.2) c, e	16.6 (0.5) d, e

Values with the same alphabet were not significantly different (p>0.05).