Ad. Wilder et al., EFFECT OF POWDER LIQUID RATIO ON THE CLINICAL AND LABORATORY PERFORMANCE OF RESIN-MODIFIED GLASS-IONOMERS/, Journal of dentistry, 26(4), 1998, pp. 369-377
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.