In vitro comparison of frictional forces of a new polycrystalline ceramic bracket versus metal-insert ceramic bracket before and after aging.

OBJECTIVE

The purpose of this study was to compare the friction of two types of polycrystalline ceramic brackets before and after aging.

METHODS

A total of 60 second-upper right premolar brackets were divided into two groups: Clarity™ Advanced (3M Unitek, Monrovia, CA) and Clarity™ (3M Unitek). All brackets had a nominal 0.022-in slot size and a McLaughlin Bennett Travesi (MBT) prescription. Each bracket was submitted to a friction test, using the YL01 UTM universal testing machine (YLE GMBH, Germany) before and after thermocycling. All tests were carried out in the presence of artificial saliva, using .019×.025-in. rectangular stainless steel (SS) archwires (3M Unitek). Bracket slot surfaces were observed under an optical microscope (Olympus CX41, Tokyo, Japan) before and after aging.

RESULTS

Before aging, the Clarity Advanced group showed significantly lower friction than the Clarity group (P=0.011). After aging, the friction of the Clarity Advanced bracket decreased significantly (P<0.001), whereas the friction of the Clarity bracket increased significantly (P<0.001). The microscopic qualitative evaluation showed that the slot surfaces of all aged Clarity brackets revealed important pit corrosion when compared with the original brackets.

CONCLUSIONS

The new Clarity Advanced ceramic bracket shows good physical friction properties due to the various modifications added by the manufacturers.