Effects of saliva and water contamination on the enamel shear bond strength of a light-cured glass ionomer cement.

The purpose of this study was to evaluate the shear bond strengths of Fuji Ortho LC (GC Corp., Tokyo, Japan), a light-cured resin-reinforced glass ionomer, used for direct bonding of stainless steel and ceramic brackets under four different enamel surface conditions: (A) nonconditioned and dry, (B) conditioned with polyacrylic acid and moistened with saliva, (C) conditioned with polyacrylic acid and moistened with water, (D) nonconditioned and wet. Stainless steel lingual buttons and two types of polycrystalline ceramic brackets, with either mechanically or chemically retentive bracket bases, were evaluated. The brackets were bonded to 120 freshly extracted bovine incisors; after storage in tap water at room temperature for 24 hours, they were subsequently tested in a shear mode with a universal testing machine. The maximum bond strength and the site of bond failure were recorded. With stainless steel brackets, subgroup B produced the highest bond strength (23.8 MPa), which was significantly (p < 0.05) higher than all the other enamel conditions tested. With ceramic brackets, the highest bond strengths (20.9 MPa and 25.4 MPa, respectively) were measured with subgroup C. Bond failure analysis revealed that each bracket type failed predominantly at the enamel-adhesive interface, except for Transcend 6000. The results indicate that the shear bond strength of Fuji Ortho LC is significantly enhanced by contaminating the enamel surface with either saliva or water after conditioning, depending on bracket type used. Even water contamination of nonconditioned enamel surfaces does not seem to preclude clinically acceptable bond strengths of both stainless steel and ceramic brackets, allowing, at the same time, a safe debonding without enamel damage.