The effect of saliva contamination on shear bond strength of orthodontic brackets when using a self-etch primer

The purpose of this study was to assess the effect of saliva contamination on the shear bond strength of orthodontic brackets, at various stages of the bonding procedure using a new self-etch primer. Brackets were bonded to 52 extracted human molars according to one of the following four protocols. Group I (uncontaminated control): A self-etch acidic primer, Angel I (3M/ESPE Minneapolis, Minn) was placed on the enamel for 15 seconds, gently dried with air, and light cured for 10 seconds. Precoated brackets APC II (3M Unitek, Monrovia, Calif) were then placed on the teeth and light cured for 20 seconds. Group II: The enamel surface was first contaminated with human saliva for 10 seconds, blown off with an air syringe for five seconds. The bonding procedure was then repeated as in group I. Group III: The self-etch primer was applied for 15 seconds, gently dried with air, and light cured for 10 seconds. The surface was then contaminated with human saliva for 10 seconds, blown off with an air syringe for five seconds. The precoated brackets were then bonded as in groups I and II. Group IV: The enamel surface was contaminated with human saliva for 10 seconds, blown off with an air syringe for five seconds. The self-etch primer was applied. The surface was then re-contaminated with human saliva for 10 seconds, blown off with an air-syringe for five seconds. The precoated brackets were then bonded as in groups I, II, and III. The results of the analysis of variance (F = 4.79) indicated that the shear bond strengths of the four groups were significantly different (P = .005). Tukey HSD tests indicated that contamination both before and after the application of the acid-etch primer resulted in a significantly lower (=1.7+/-1.4 MPa) shear bond strength than either the control group (=6.0+/-3.5 MPa) or the groups where contamination occurred either before (=4.8+/-3.3 MPa) or after (=4.8+/-3.3 MPa) the application of the primer. The new acid-etch primer can maintain adequate shear bond strength if contamination occurs either before or after the application of the primer. On the other hand, contamination both before and after the application of the primer significantly reduced the shear bond strength of orthodontic brackets.