An ex vivo investigation into the fluoride release and absorption profiles of three orthodontic adhesives

Prevention of peri-bracket decalcification is essentially mediated by effective oral hygiene, which is patient dependent. The potential to compensate for poor oral hygiene may be through the release of free fluoride ions from direct bonding agents. It is well established that glass ionomer cements (GICs) release free fluoride ions which may be replenished by exposure to fluoride containing solutions. The aim of this ex vivo study was to compare the fluoride release and absorption profiles of a recently developed low fusion, monophase GIC, Limerick glass, with two materials in common clinical use, namely, Fuji-Ortho (TM) L.C. and Concise (TM). Ten test specimens of each material were fabricated and stored in deionized water at 37 degreesC. The concentration of fluoride release was measured daily for the first 7 days after immersion and then weekly for 5 weeks. On day 42 the test specimens were recharged in 2 per cent sodium fluoride solution and fluoride release was measured initially after 24 hours and then every 48 hours. The recharge regimen was repeated for 3 weeks. Both Limerick glass and Fuji-Ortho (TM) L.C. demonstrated the characteristic fluoride release pattern of GIC with a rapid elution of fluoride after the first 24 hours followed by a more gradual release profile over the following 2 weeks. Fuji-Ortho (TM) L.C. released the greatest quantity of fluoride but the release profile of Limerick glass was more sustained. Concise (TM) released negligible amounts of fluoride. Limerick glass and Fuji-Ortho (TM) L.C. showed an increase (P < 0.01) in fluoride release following exposure to 2 per cent sodium fluoride that decreased both with time and subsequent exposures to fluoride supplement.