Effect of refrigerant-spray cold treatment on orthodontic bracket debond strength

There have been numerous studies testing the effect of heat to facilitate or ease orthodontic bracket removal to reduce potential enamel damage during bracket removal/debonding.  Cold treatment using a refrigerant spray (Endo Ice) has also been recommended by bracket manufacturers as another option to facilitate bracket debonding.  However, there has been no research to test this proposed methodology.  Objectives: The purpose of this investigation was to evaluate the effect of refrigerant spray-induced cold treatment on bracket shear debond strength and debond location at the enamel/adhesive/bracket interface.  Methods: Universal twin-wing stainless steel brackets precoated with Transbond XT adhesive (3M Unitek) were bonded to 20 pairs of extracted human mandibular third molars in an environmental chamber to simulate oral temperature and humidity.  Following 24-hr storage in 0.9% phosphate buffered saline at 37°C, one tooth-bonded bracket from each pair was randomly assigned to the cold treatment or the control group (N=20/group).  For the cold treatment group, a cotton pellet saturated with refrigerant spray was held to the buccal surface of the bonded bracket for 15 s prior to shear debonding of the bracket with a universal tester.  With the control group, no cold treatment was applied prior to bracket debonding.  Shear debond strength was recorded, and the amount of adhesive remaining on the tooth after bracket removal was scored using the Adhesive Remnant Index (ARI).  Results: A dependent t-test indicated there was no statistically significant effect (p>0.05) of the refrigerant spray cold treatment on bracket debond strength as compared to the control group.  There was also no statistically significant effect (p>0.05) of refrigerant spray on the ARI score.  Conclusions: The evidence suggests cold treatment does not ease orthodontic bracket removal and thus, there is no rationale to support including this methodology in clinical practice.  Supported by UMKC SOD Summer Scholars Program