title: Water-sorption kinetics of dental polymeric resin under tensile stressing conditions.
abstract: Water sorption tests were conducted on unfilled poly(methyl methacrylate) samples in distilled water at 5, 37, and 60 degrees C under three different tensile stress ratios (sigma appl/sigma ys = 0%, 5%, and 10%). Each sample was placed in a modified Hoffman open-side tubing clamp and subjected to four-point bending at pre-determined stress level for 1 day, 3 days, 1 week, 2 weeks, and 4 weeks. Water sorption was measured by weight change calculations, without accounting for any weight loss due to solubility of uncured monomer. A generalized diffusion equation can be used to express both stress-free and stress conditions; D = D0exp[-E (sigma)/kT]. It was found that the activation energy for water sorption diffusion was linearly related to applied stress ratios; i.e., E = 1.15 sigma appl/sigma ys + 10.76 (kJ/mol), with the correlation coefficient r = 0.97. Since the proportional pre-exponential constant, D0, is independent of temperature, it is speculated that the loading percentage of reinforcing filler elements in composite resin materials can be related to this constant.
authors.affiliation: Department of Restorative Dentistry, Indiana University School of Dentistry, Indianapolis, USA. yoshida@iusd.iupui.edu
authors.forename: Y
authors.initials: Y
authors.lastname: Oshida
authors.forename: J
authors.initials: J
authors.lastname: Gorthy
mesh_terms: D001672:Biocompatible Materials; D004058:Diffusion; D007700:Kinetics; D008422:Materials Testing; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D012044:Regression Analysis; D013314:Stress, Mechanical; D013696:Temperature; D013718:Tensile Strength; D014867:Water / Q000737:chemistry*
chemical_list: D001672:Biocompatible Materials; D014867:Water; D019904:Polymethyl Methacrylate