Comparison of conventional and self-adhesive orthodontic bonding systems in white spot lesion formation: an in vitro...

To compare the susceptibility of enamel to white spot lesion formation following the application of two orthodontic bonding protocols: a conventional three-step adhesive system and a two-step self-adhesive system with primer integrated into the resin.

Thirty extracted premolars were randomly allocated to two groups: Transbond XT (three-step system) and GC Ortho Connect (two-step self-adhesive system). After 7-day pH cycling, demineralization was assessed using Witec a300R confocal Raman microscopy. Phosphate intensity at 960 cm-1 was measured along a 130-µm enamel profile and normalized.

Measurements by two operators showed high intraoperator and interoperator reliability (intraclass correlation coefficient = 0.82-0.92). GC samples exhibited a continuous decline in phosphate intensity, indicating extensive demineralization, while XT samples showed a midenamel plateau, suggesting mineral preservation. Spline modeling confirmed significantly higher phosphate retention in the XT group at middepth (P < .001), with both groups showing surface demineralization near 130 µm (P = .005).

The three-step adhesive system (Transbond XT) showed greater resistance to subsurface enamel demineralization than the self-adhesive system (GC Ortho Connect). These results suggest that using a separate primer may better protect enamel beyond the immediate bracket interface.