title: Effect of powder/liquid ratio on the clinical and laboratory performance of resin-modified glass-ionomers.
abstract: 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.
authors.affiliation: Department of Operative Dentistry, School of Dentistry, University of North Carolina, Chapel Hill 27599-7450, USA. aldridge_wilder@dentistry.unc.edu
authors.forename: A D
authors.initials: AD
authors.lastname: Wilder
authors.forename: A A
authors.initials: AA
authors.lastname: Boghosian
authors.forename: S C
authors.initials: SC
authors.lastname: Bayne
authors.forename: H O
authors.initials: HO
authors.lastname: Heymann
authors.forename: J R
authors.initials: JR
authors.lastname: Sturdevant
authors.forename: T M
authors.initials: TM
authors.lastname: Roberson
mesh_terms: 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
chemical_list: D000269:Adhesives; D017220:Dentin-Bonding Agents; C079765:Fuji II LC cement; D005899:Glass Ionomer Cements; D011208:Powders; D012117:Resins, Synthetic; D012996:Solutions