Stability of the bonded lingual wire retainer-a study of the initial bond strength

Bonded lingual retainers (individually adjusted multistranded wires with one bond site per tooth) are used extensively to maintain the orthodontic treatment result. Failure or loss often leads to a relapse. The bond strength of bonded lingual retainers has not yet been studied in respect of the loads that can be withstood by them through deflection of the interdental archwire region. Furthermore, human anterior teeth have never before been used for a study of this kind. Six different wire/composite combinations were studied (wires: Dentaflex co-axial 0.018", Dentaflex multistranded 0.018", and Respond Dead Soft straight, length 0.0175"; composites: Tetric Flow and Heliosit Orthodontic) by bonding 1 cm lengths of wire to the lingual surfaces of 360 extracted lower anterior teeth. Using an Instron 6025 universal testing machine, vertical shear bond strength tests at the bond site as well as vertical shear bond strength tests and horizontal tensile strength tests were performed. The failure characteristics after failure at maximum force were evaluated by light microscopy, scanning electron microscopy, and morphometry. Most failures were observed at the enamel/composite interface. The selected wires displayed no significant differences; Tetric Flow proved to be the most stable resin; and no enamel tear-outs were observed.