Effect of Duration of Contamination with Saliva on Shear Bond Strength of Orthodontic Brackets to Tooth Surfaces

Contamination with saliva is an important factor in reducing the shear bond strength of orthodontic brackets to tooth surfaces. One of the most important disadvantages of bonding techniques is their sensitivity to contamination with saliva. The aim of this study was to evaluate the effect of duration of contamination of tooth surfaces covered with unfilled resin with saliva on shear bond strength orthodontic brackets.
In this experimental study, 110 extracted human intact premolar teeth were divided into 5 main groups and 11 subgroups. In the control group the brackets were bonded to tooth surfaces with no saliva contamination. In other groups, after applying the unfilled resin, the samples underwent saliva contamination as follows: group B, 1, 5 and 15 seconds of contamination; group C, 1, 5 and 15 seconds of contamination and drying with air current; and group D, 1, 5 and 15 seconds of contamination and washing and drying with air current, followed by bonding of the brackets. In group E, according to the manufacturer's instructions, after contamination, washing and drying, unfilled resin was applied again and then the brackets were bonded. The shear bond strength of brackets to tooth surfaces was measured by an Instron machine. Data were analyzed with ANOVA (α = 0.05).
The highest bond strength was recorded in the control group (4.21 MPa) and the lowest in the fourth subgroup (15 seconds of contamination without washing) (3.8 MPa). There were significant differences in the mean bond strengths of brackets bonded to enamel surfaces between the main groups (p value = 0.001).
Contamination with saliva reduces bond strength. Proper isolation is necessary to achieve a stronger bond between orthodontic brackets and tooth surfaces.