In vitro investigation of indirect bonding with a hydrophilic primer

The aim of this in vitro investigation was to evaluate bond strength for a custom base indirect bonding technique using a hydrophilic primer on moisture-contaminated tooth surfaces. Stainless steel brackets were bonded to 100 permanent bovine incisors using a light-cured custom base composite adhesive, a chemically cured sealant, and the hydrophilic primer Transbond MIP (3M-Unitek, Monrovia, Calif). Five groups (A-E) of 20 teeth each were formed according to the time of contamination (before or after application of the primer) and the type of contaminant (distilled water or saliva): A, control group with no contamination; B, contamination with saliva before application of the primer; C, contamination with water before application of the primer; D, contamination with saliva before and after application of the primer; and E, contamination with water before and after application of the primer. Mean bond strength for the group without contamination (A) was 15.07 +/- 4.14 MPa and was not significantly different from bond strengths for groups B (14.91 +/- 3.99 MPa) and C (16.12 +/- 3.67 MPa), in which contamination occurred before application of the hydrophilic primer. Average bond strength in group D was 11.92 +/- 4.76 MPa. The lowest mean bond strength was measured for group E (9.85 +/- 3.77 MPa) and was significantly lower than for groups A, B, and C. Contamination after primer application resulted in an increased risk of bond failure at clinically relevant levels of stress.