A comparison of fluoride release by resin-modified GIC and polyacid-modified composite resin

The objective of this study was to compare the fluoride release of 2 fluori de-containing orthodontic adhesives from bracketed teeth and adhesive disks , a resin-modified glass ionomer cement (Fuji Ortho LC, encapsulated; GC Am erica Corp, Aslip, III) and a polyacid-modified composite resin (Assure; Re liance Orthodontic Products, Itasca, III). A composite resin without fluori de (Transbond XT; 3M Unitek, Monrovia, Calif) was used as a reference contr ol. Metal brackets were bonded to the buccal surfaces of 120 human premolar s (40 teeth per adhesive), and disks were made from each adhesive. The deio nized storage water was changed, and fluoride release was measured at speci fied intervals up to 28 days for the bracketed teeth and up to 150 days for the disks. Fuji Ortho LC released 75% more accumulated fluoride than Assur e (6.61 mug/bracket vs 3.77 mug/bracket) from bracketed teeth over the 28-d ay observation period. Assure released more fluoride per day than did Fuji Ortho LC from the disks during the first 3 months. For the rest of the 150- day period, Fuji Ortho LC released more fluoride per day than did Assure. T he amount of fluoride released by these materials varied dramatically with different water-changing protocols, The large discrepancy between fluoride released from disks compared with that released from bracketed teeth sugges ts that caution must be used in extrapolating fluoride-release levels of ad hesive disks to in vivo treatment conditions.