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Microleakage between composite-wire and composite-enamel interfaces of flexible spiral wire retainers. Part 2: comparison of amorphous calcium phosphate-containing adhesive with conventional lingual retainer composite.

The aim of this study was to test the hypothesis that there is no difference in the microleakage values of a newly developed amorphous calcium phosphate (ACP)-containing adhesive and a conventional lingual retainer composite at the composite-enamel and composite-wire interfaces of flexible spiral wire retainers (FSWRs). Sixty freshly extracted human mandibular incisors separated into three equal groups were used in this study. Multi-stranded 0.0215 inch diameter wire was bonded to enamel using conventional orthodontic adhesive (Transbond LR, 3M Unitek) and ACP-containing composite (Aegis Ortho, Harry J. Bosworth Co.), with or without the use of a primer. The specimens were sealed with nail varnish, stained with 0.5 per cent basic fuchsine for 24 hours, sectioned and examined under a stereomicroscope, and scored for microleakage at the composite-enamel and composite-wire interfaces from the mesial and distal margins. Statistical analyses were performed with Kruskal-Wallis and Mann-Whitney U-tests with a Bonferroni correction. Little or no microleakage was observed between the composite-enamel interface for any of the three groups, and any difference was not statistically significant. The amount of microleakage at the wire-composite interface was higher than that at the enamel-composite interface. Multiple comparison testing showed statistically significant differences in microleakage between Transbond LR and the ACP-containing adhesive used with primer at the composite-enamel and composite-wire interfaces (P < 0.001). ACP-containing adhesive used with primer showed the highest microleakage scores at the composite-enamel (mean: 0.39 +/- 0.42 mm) and composite-wire (mean: 1.66 +/- 0.47 mm) interfaces. The hypothesis is rejected. The ACP-containing composite used with or without primer showed significantly higher leakage at the composite-wire interface, while conventional lingual retainer composite showed lower microleakage scores.