Time-related bond strengths of light-cured and chemically cured bonding systems: an in vitro study

The immediate bond strengths achieved with a light-cured bonding system and those at selected time intervals over a 24-hour period were assessed and compared with the bond strengths produced by a chemically cured system over a similar period. Mesh-backed metal orthodontic brackets were bonded with the light-cured system to 60 teeth, and 50 teeth had similar brackets bonded with a chemically cured system. Shear/peel bond strengths for each were determined with the instron Universal testing machine (Instron Corp., Canton, Mass.) and these were compared statistically. The bond strengths for the chemically cured system were initially low, but these increased with time. The light-cured sample displayed initial bond strengths of sufficient magnitude to withstand the immediate application of orthodontic forces, and these bond strengths also increased with time. There was no significant difference between the bond strengths achieved by the chemically cured and light-cured systems at the 10-minute, 60-minute, and 24-hour intervals.