Metal strength of direct bonding brackets.

Because the strength of direct bonding brackets is both important and difficult to measure, a related property, microhardness, has been investigated. Twelve popular U.S. brands of direct bonding brackets have been tested with a Vickers-Hanemann microhardness apparatus. The tests have shown a consistently wide difference in hardness between brands, the highest values being exhibited by those using the precipitation hardened steel known as PH 17-4, and the lowest by those using the austenitic 316L. As the first steel proved to be significantly less corrosion resistant than the last one, it seems that today there are too few attachments that are both strong and chemically resistant.