title: Solvent and water retention in dental adhesive blends after evaporation.
abstract: This study examined the extent of organic solvent and water retention in comonomer blends with different hydrophilicity (Hoy's solubility parameter for hydrogen bonding, delta(h)) after solvent evaporation, and the extent of tracer penetration in polymerised films prepared from these resins. For each comonomer blend, adhesive/solvent mixtures were prepared by addition of (1) 50 wt% acetone, (2) 50 wt% ethanol, (3) 30 wt% acetone and 20 wt% water and (4) 30 wt% ethanol and 20 wt% water. The mixtures were placed in glass wells and evaporated for 30-60s for acetone-based resins, and 60-120 s for ethanol-based resins. The weight of the comonomer mixtures was measured before and after solvent evaporation. Resin films were prepared for transmission electron microscopy (TEM) after immersion in ammonical silver nitrate. The percentages of solvent and water retained in the comonomer mixtures, and between the acetone and ethanol groups were measured gravimetrically and were statistically compared. In comonomer-organic solvent mixtures, the percentage of solvent retained in acetone and ethanol-based mixtures increased significantly with hydrophilicity of the comonomer blends (P < 0.05). In resin-organic solvent-water mixtures, significantly more solvent and water were retained in the ethanol-based mixtures (P < 0.0001), when compared to acetone-based mixtures after 60s of air-drying. TEM revealed residual water being trapped as droplets in resin films containing acetone and water. Water-filled channels were seen along the film periphery of all groups and throughout the entire resin films containing ethanol and water. The addition of water to comonomer-ethanol mixtures results in increased retention of both ethanol and water because both solvents can hydrogen bond to the monomers.
authors.affiliation: Department of Paediatric Dentistry and Orthodontics, Faculty of Dentistry, The University of Hong Kong, Prince Philip Dental Hospital, China.
authors.forename: Cynthia K Y
authors.initials: CK
authors.lastname: Yiu
authors.forename: Edna L
authors.initials: EL
authors.lastname: Pashley
authors.forename: Noriko
authors.initials: N
authors.lastname: Hiraishi
authors.forename: Nigel M
authors.initials: NM
authors.lastname: King
authors.forename: Cecilia
authors.initials: C
authors.lastname: Goracci
authors.forename: Marco
authors.initials: M
authors.lastname: Ferrari
authors.forename: Ricardo M
authors.initials: RM
authors.lastname: Carvalho
authors.forename: David H
authors.initials: DH
authors.lastname: Pashley
authors.forename: Franklin R
authors.initials: FR
authors.lastname: Tay
mesh_terms: D000042:Absorption; D011232:Chemical Precipitation; D003460:Crystallization / Q000379:methods*; D003738:Dental Cements / Q000032:analysis / Q000737:chemistry*; D008422:Materials Testing; D012997:Solvents / Q000032:analysis / Q000737:chemistry*; D014835:Volatilization; D014867:Water / Q000032:analysis / Q000737:chemistry*
chemical_list: D003738:Dental Cements; D012997:Solvents; D014867:Water