title: Effect of resin hydrophilicity and temperature on water sorption of dental adhesive resins.
abstract: This study examined the effects of copolymer hydrophilicity and temperature on water sorption and solubility characteristics of five copolymer blends of increasing degree of hydrophilicity using gravimetric measurements. Six resin disks (15 mm in diameter x 1 mm in thickness) were prepared from each copolymer blend and were stored in deionised water at 23, 37 and 55 degrees C. Water sorption and solubility of the resin disks were measured before and after water immersion and desiccation. Multiple regression analysis of water sorption was performed on two independent variables, copolymer hydrophilicity and temperature. Maximum water sorption increased significantly with Hoy's total cohesive energy density (delta(t)), Hoy's solubility parameter for polar forces (delta(p)) and hydrogen bonding (delta(h)), but was not influenced by temperature. However, a significant positive relationship was observed between diffusion coefficients (obtained using Fick's law of diffusion) and temperature. The water absorption activation energy was 10 kJ/mol for the most hydrophilic copolymer blend R5 and 35-51 kJ/mol for copolymer blends R1-R4. The positive relationship between maximum water uptake and copolymer hydrophilicity suggests that water molecules diffuse through the polymer matrices by binding successively to the polar sites via hydrogen bonding. Such water sorption may determine the durability of resin-dentine bonds.
authors.affiliation: Paediatric Dentistry and Orthodontics, Faculty of Dentistry, The University of Hong Kong, Prince Philip Dental Hospital, 34 Hospital Road, Pokfulam, Hong Kong SAR, China.
authors.forename: Cynthia K Y
authors.initials: CK
authors.lastname: Yiu
authors.forename: Nigel M
authors.initials: NM
authors.lastname: King
authors.forename: Marcela R O
authors.initials: MR
authors.lastname: Carrilho
authors.forename: Salvatore
authors.initials: S
authors.lastname: Sauro
authors.forename: Frederick A
authors.initials: FA
authors.lastname: Rueggeberg
authors.forename: Carlo
authors.initials: C
authors.lastname: Prati
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: D000269:Adhesives / Q000737:chemistry*; D003738:Dental Cements / Q000737:chemistry*; D019279:Resin Cements / Q000737:chemistry*; D012995:Solubility; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D000269:Adhesives; D003738:Dental Cements; D019279:Resin Cements; D014867:Water