[The tensile bonding strength of metal plasma-coated bracket bases]

The tensile bond strength of bracket bases coated with metal plasma were examined. The aim was to investigate, whether the conditioning of bracket bases by metal plasma is a possible means to increase the tensile bond strength. Two typical orthodontic adhesives were used. Three test groups were differentiated: 1. Metal mesh bracket bases (coated and uncoated with metal plasma), 2. metal bracket bases without mesh (coated with metal plasma), 3. ceramic bracket bases coated with metal plasma. Metal bracket bases with mesh, coated with metal plasma showed superior bond strength in comparison to usual uncoated mesh bracket bases. The former were nearly four times stronger than the uncoated bases with reference to the first adhesive and two times stronger referring to the second adhesive. The primary source of the enhancement of adhesion is due to the enormous increase of the retentive active surface created by the metal plasma. This structure guarantees an excellent micromechanical interlocking for the adhesive. The mean tensile bond strength of titanium coated mesh bases was 20.03 N/mm2 (= 286 N/bracket). Plasma coated bases without mesh reached average interlocking forces comparable to conventional uncoated mesh bases. Ceramic bracket bases were found not to be suitable for plasma coating. As a result of these experimental findings metal plasma coating of metal bracket bases can be regarded as an excellent means to increase the tensile bond strength.