An in vitro investigation into the use of resin-modified glass poly(alkenoate) cements as orthodontic bonding agents

This in vitro study was designed to determine the effect of time on the mea sured mean force to debond when brackets were bonded using resin-modified g lass poly(alkenoate) cements and to compare them with a light-cured diacryl ate. Changes in surface topography and composition of the cements were also investigated. Stainless steel orthodontic brackets were bonded to 160 uppe r premolar teeth in four test groups: Transbond, Fuji Ortho LC, and 3M Mult i-Cure with and without enamel etching. Shear bond testing to failure was p erformed after 1 hour, 1 week, 1 month, and 1 year. The first three groups were then rebonded and stored for the same time periods before being shear tested again. Debond force was recorded in Newtons and the locus of bond fa ilure was scored using the Adhesive Remnant Index (ARI). Surface topography and composition of the test materials were also studied at time periods of 1 day, and 1, 6, and 18 months, using scanning electron microscopy (SEM) a nd energy dispersive X-ray analysis (EDAX). The mean force to debond (N) was observed to increase with time in all four test groups, with there being little significant difference between the gr oups. When the same brackets were rebonded, the mean force to debond reduce d. Surf ace topography and compositional changes over time were only observ ed with the resin-modified glass poly(alkenoate) cements. Resin-modified gl ass polylalkenoate) cements have a mean force to debond comparable with dia crylate bonding agents. However, unlike diacrylates they undergo surface ch anges with time, the significance of which is unknown.