EFFECT OF POWDER LIQUID RATIO ON THE CLINICAL AND LABORATORY PERFORMANCE OF RESIN-MODIFIED GLASS-IONOMERS/

Objectives: To compare the effects of powder/liquid (P/L) ratio and su rface wetness on retention of adhesive Class V restorations. Methods: One-hundred and six Fuji II LC restorations were placed at two clinica l trial sites. In the 'high-dry' group (Site A), Fuji II LC was mixed at a P/L ratio of 3.0 and applied to dentine that was visibly dry, but not desiccated. In the 'low-wet' group (Site B), Fuji II LC was mixed at a P/L ratio of 2.25 and applied to dentine that was glisteningly m oist. The restorations were evaluated at baseline, 1 and 2 years at bo th sites, and at 3 years at one site. The P/L ratio effects on viscosi ty and welting were evaluated in vitro by determining the film thickne ss possible at different ratios. Results: At 2 years the retention lev els at the two sites differed significantly (p less than or equal to 0 .1). Site B ('low-wet' group) exhibited 100% retention, and Site A ('h igh-dry' group) exhibited 78% retention. At 3 years Site A exhibited 7 4% retention, and nine of the 12 retention failures occurred in patien ts 65 years and older. Laboratory measurements demonstrated that the v iscosity of 'low-wet' mixtures permitted film thicknesses that were on e-half those of the 'high-dry' group. Conclusions: The study demonstra ted that a higher powder/liquid ratio and a drier dentine surface comp romised wetting by a resin-modified glass-ionomer resulting in a decli ne in retention from baseline to 3 years. This study suggests that the dentine surface should be kept hydrated to promote bonding, and that the powder/liquid ratio should be low enough to create low-viscosity m ixtures which promote wetting. In the 'high-dry' dentine group there w as still 74% retention at 3 years, indicating that factors other than wetting affect retention. (C) 1998 Elsevier Science Ltd. All rights re served.