Contamination of enamel by blood during bonding lowers the shear bond strength of orthodontic brackets, according to an animal study in the British Journal of Oral and Maxillofacial Surgery (July 22, 2010).
Researchers from the University of Pavia divided 160 bovine permanent mandibular incisors into 8 groups of 20 specimens each. Both orthodontic brackets (Step brackets, Leone) and bondable buttons (Flat orthodontic buttons, Leone) were tested on four different enamel surfaces: dry, contamination with blood before priming, after priming, and before and after priming.
Brackets and buttons were bonded to the teeth and subsequently tested using a universal testing machine. Shear bonding strength and the rate of adhesive failures were recorded and analyzed using three methods.
The researchers found that uncontaminated enamel surfaces showed the highest bonding strengths for both brackets and buttons. When they were contaminated with blood, orthodontic brackets had significantly lower shear strengths than bondable buttons (p = 0.0001).
"Contamination of enamel by blood during bonding lowers the strength of the bond, more so with orthodontic brackets than with bondable buttons," the researchers concluded.
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