title: The influence of storage time and pH variation on water sorption by different composite resins.
abstract: OBJECTIVE
  The objective of this work was to assess the influence of storage time and pH cycling on water sorption by different composite resins.
  
  
  METHODS
  Nine resin brands were selected and divided into groups: G1-ROK (SDI), G2-ICE (SDI), G3-GLACIER (SDI), G4-Z350 (3M/ESPE), G5-Z250 (3M/ESPE), G6-TPH 3 (DENTSPLY), G7-ESTHET X (DENTSPLY), G8-SUPRAFILL (SSWHITE), and G9-MASTERFILL (BIODINΒMICS). Ninety specimens, ten per group, were obtained using an aluminum matrix. Specimens measured 10 mm diameter × 2 mm width. The groups were divided into subgroups according to the immersion solution: A - control (n = 05) stored in artificial saliva pH = 7.0 and B-test (n = 05) submitted to seven consecutive days of pH cycling (cariogenic challenger) that consisted of immersion in a pH° = 4.3 solution for 6 h followed by immersion in a pH¹ =7.0 solution for 18 h and stored in artificial saliva pH = 7.0 until the end of the experiment. The specimens were weighed on six occasions: T 0 (after fabrication), T 1 (24 h), T 2 (7 days), T 3 (15 days), T 4 (30 days), T 5 (60 days), and then analyzed. The water sorption was determined by the weight difference between the specimens at the time intervals.
  
  
  RESULTS
  The mean weight gain was exactly the same for both the subgroups within group G4. The highest means for the control subgroup were found in groups: G1, G5, G7, G8, and G9. For the pH cycling subgroup, the highest means were found in G2, G3, and G6; however, significant differences between the subgroups compared to the mean-weight gain were found for G1, G5, and G7.
  
  
  CONCLUSIONS
  The water sorption of composite resins is dependent upon their storage time. The pH cycling created a significant impact on resins G1, G5, and G7. The sorption and solubility of composite resins vary according to their chemical composition.
authors.affiliation: Federal University of Pernambuco, Av. Prof. Moraes Rego, Recife, Brazil.
authors.forename: George Mário de Araújo Silva
authors.initials: GM
authors.lastname: Gusmão
authors.forename: Thiago Vinicius Veras
authors.initials: TV
authors.lastname: De Queiroz
authors.forename: Guilherme Ferrer
authors.initials: GF
authors.lastname: Pompeu
authors.forename: Paulo Fonseca
authors.initials: PF
authors.lastname: Menezes Filho
authors.forename: Cláudio Heliomar Vicente
authors.initials: CH
authors.lastname: da Silva
mesh_terms: D000042:Absorption; D000327:Adsorption; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002326:Cariogenic Agents / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D006801:Humans; D006813:Humidity; D006863:Hydrogen-Ion Concentration; D007101:Immersion; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D053758:Nanoparticles / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry; D012464:Saliva, Artificial / Q000737:chemistry; D012995:Solubility; D013499:Surface Properties; D013997:Time Factors; D014867:Water / Q000737:chemistry*
chemical_list: D002326:Cariogenic Agents; D003188:Composite Resins; D003764:Dental Materials; C466112:Esthet-X; C444701:Filtek Z250; D008689:Methacrylates; D011109:Polymethacrylic Acids; D011140:Polyurethanes; D012464:Saliva, Artificial; C485361:Suprafil; C113300:TPH hybrid; C533204:filtek Z350; C471182:glacier hybrid composite; D014867:Water; C029824:urethane dimethacrylate luting resin; C020946:triethylene glycol dimethacrylate; C041979:2,2-bis-(4-(2-methacryloxyethoxy)phenyl)propane; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate