Effect of fluoride exposure on cariostatic potential of orthodontic bonding agents: an in vitro evaluation

The aims of this in vitro study were to compare the cariostatic potential of a resin modified glass ionomer cement (Fuji Ortho LC) to that of a resin control (Transbond) for bracket bonding and to compare the effect of extrinsic fluoride application on the cariostatic potential of each material.

Ex vivo study.

Orthodontic brackets were bonded to 40 extracted premolars, 20 with Fuji Ortho LC and 20 with Transbond. The teeth were subjected to pH cycling, pH 4.55, and pH 6.8, over a 30-day period. Ten teeth bonded with each material were immersed in a 1000 ppm fluoride solution for 2 minutes each day. Fluoride release was measured throughout the study from all teeth. After 30 days, the teeth were assessed visually for signs of enamel decalcification.

Significant differences in decalcification existed macroscopically between all four groups of teeth, with the exception of those bonded with Fuji Ortho LC alone compared with Transbond alone (P = 0.22), and Fuji Ortho LC alone compared with Transbond with added fluoride (P = 0.3). Fluoride release from Fuji Ortho LC alone fell to minimal values, but with the addition of extrinsic fluoride the levels fell initially and then followed an upward trend. There was minimal fluoride release, from Transbond alone, but with daily addition of extrinsic fluoride, subsequent fluoride release was increased. Significant differences existed in the amount of fluoride released between all groups, except comparing Fuji Ortho LC alone and Transbond with added fluoride.

The results of this study have indicated that with an in vitro tooth-bracket model, the creation of white spot inhibition could best be achieved by the use of a resin-modified glass ionomer cement, supplemented with fluoride exposure. The least protection was afforded by the composite control. The resin-modified glass ionomer cement alone and the composite with added fluoride demonstrated equivalent protection.