title: Microhardness and surface topography of a composite resin cement after water storage.
abstract: OBJECTIVE
  The aims of this study were to assess changes in the microhardness and surface roughness of a dual-cured composite resin cement after water storage for different periods of time.
  
  
  METHODS
  Sixty specimens were divided into four groups comprising high- and low-viscosity cement specimens stored either dry or in water for 1 to 60 days. Microhardness and surface roughness measurements were made after 1, 7, and 60 days of storage.
  
  
  RESULTS
  It was found that that although interactions complicated the interpretation of the results, the water-stored samples had a significantly lower microhardness compared to the dry-stored specimens for every time interval. In addition, the high-viscosity specimens had a significantly higher microhardness compared to the low-viscosity specimens. An increased microhardness was found for all groups, except for the low-viscosity, water-stored specimens after 60 days of water storage, which was attributed to an effect of the chemical postcuring process. Although difficult to evaluate from a clinical point of view, the laser profilometry analysis revealed that a significantly increased surface roughness was found after water storage and increased storage time that was possibly caused by a deterioration of the resin-matrix surface.
  
  
  CONCLUSIONS
  For the permanency of the interfacial luting material, a high microhardness value seems to be important.
authors.affiliation: Department of Prosthetic Dentistry, Faculty Odontology, Göteborg University, Sweden. milleding@odontologi.gu.se
authors.forename: P
authors.initials: P
authors.lastname: Milleding
authors.forename: F
authors.initials: F
authors.lastname: Ahlgren
authors.forename: A
authors.initials: A
authors.lastname: Wennerberg
authors.forename: U
authors.initials: U
authors.lastname: Ortengren
authors.forename: S
authors.initials: S
authors.lastname: Karlsson
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry*; D016001:Confidence Intervals; D006244:Hardness; D006245:Hardness Tests / Q000379:methods; D013499:Surface Properties; D013997:Time Factors; D014783:Viscosity; D014867:Water / Q000737:chemistry*
chemical_list: D003188:Composite Resins; D014867:Water