Effect of powder/liquid ratio on the clinical and laboratory performance of resin-modified glass-ionomers.
OBJECTIVE
To compare the effects of powder/liquid (P/L) ratio and surface wetness on retention of adhesive Class V restorations.


METHODS
One-hundred and six Fuji II LC restorations were placed at two clinical 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 moist. The restorations were evaluated at baseline, 1 and 2 years at both sites, and at 3 years at one site. The P/L ratio effects on viscosity and wetting were evaluated in vitro by determining the film thickness possible at different ratios.


RESULTS
At 2 years the retention levels at the two sites differed significantly (p < or = 0.1). Site B ('low-wet' group) exhibited 100% retention, and Site A ('high-dry' group) exhibited 78% retention. At 3 years Site A exhibited 74% retention, and nine of the 12 retention failures occurred in patients 65 years and older. Laboratory measurements demonstrated that the viscosity of 'low-wet' mixtures permitted film thickness that were one-half those of the 'high-dry' group.


CONCLUSIONS
The study demonstrated that a higher powder/liquid ratio and a drier dentine surface compromised wetting by a resin-modified glass-ionomer resulting in a decline 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 mixtures which promote wetting. In the 'high-dry' dentine group there was still 74% retention at 3 years, indicating that factors other than wetting affect retention.
Wilder
A D
AD
Department of Operative Dentistry, School of Dentistry, University of North Carolina, Chapel Hill 27599-7450, USA. aldridge_wilder@dentistry.unc.edu
Boghosian
A A
AA
Bayne
S C
SC
Heymann
H O
HO
Sturdevant
J R
JR
Roberson
T M
TM
D000269:Adhesives / Q000737:chemistry; D000328:Adult; D000367:Age Factors; D000368:Aged; D001840:Dental Bonding; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent / Q000145:classification; D003804:Dentin / Q000648:ultrastructure; D017220:Dentin-Bonding Agents / Q000737:chemistry; D005260:Female; D005500:Follow-Up Studies; D005899:Glass Ionomer Cements / Q000737:chemistry*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011208:Powders; D012117:Resins, Synthetic / Q000737:chemistry*; D012996:Solutions; D013499:Surface Properties; D014783:Viscosity; D017155:Wettability
D000269:Adhesives; D017220:Dentin-Bonding Agents; C079765:Fuji II LC cement; D005899:Glass Ionomer Cements; D011208:Powders; D012117:Resins, Synthetic; D012996:Solutions