title: Surface integrity of solvent-challenged ormocer-matrix composite.
abstract: OBJECTIVE
  To investigate the surface integrity of solvent-challenged ormocer-matrix composites, photoactivated by different light exposure modes, through surface-hardness measurements at different periods of time; and to compare such behavior with dimethacrylate-based materials.
  
  
  METHODS
  One hundred percent ormocer-based matrix (experimental ormocer (ORM)), a commercial mixed dimethacrylate-ormocer-based matrix (Admira (ADR)) and two commercial dimethacrylate-based matrix composites (experimental controls, (Grandio (GRD) and Premise (PRE)) were evaluated. Disk specimens (4 mm × 2 mm) were prepared from each material and light-activated using either a standard (S) or soft-start (SS) light exposure protocol with an LED-curing unit. Top, irradiated surface Knoop hardness (KHN) was measured within the following experimental groups (n=5): Group 1: immediately after exposure; Group 2: after dry and dark storage, Group 3: after storage in distilled water, and Group 4: immersion in absolute ethanol. Hardness of Groups 2-4 were measured after 7 days storage. Immediate hardness values were submitted to Student's t-tests separately for each material. Hardness values after treatments were submitted to two-way ANOVA and Tukey's post hoc test to compare values among different storage media and light exposure mode protocols. Comparisons among materials were described using percentage of hardness change. Statistical testing was performed at a pre-set alpha of 0.05.
  
  
  RESULTS
  Immediate hardness values were not affected by the light exposure mode, regardless of the material. In general, exposure mode did not significantly affect hardness after 7 days storage, regardless of storage media or material. After 7 days dry storage, hardness values increased for all materials relative to immediate testing, and decreased after water and ethanol storage, with ethanol showing the greatest effect. The experimental ormocer-based material had the lowest percentage hardness change and thus proved more resistant to solvent degradation than the other materials, regardless of the light exposure method.
  
  
  CONCLUSIONS
  Irradiated surface hardness values and surface integrity were unaffected by light exposure mode, regardless of the material tested. The experimental ormocer-based material presented the least change in hardness as a result of solvent challenge than any of the commercial products: ormocer or conventional resin-based, and thus showed better surface integrity.
authors.affiliation: Biomaterials Research Group, The University of Manchester, School of Dentistry, UK. lara cavalcante@yahoo.com.br
authors.forename: Larissa Maria
authors.initials: LM
authors.lastname: Cavalcante
authors.forename: Luis Felipe J
authors.initials: LF
authors.lastname: Schneider
authors.forename: Nick
authors.initials: N
authors.lastname: Silikas
authors.forename: David C
authors.initials: DC
authors.lastname: Watts
mesh_terms: D002516:Ceramics / Q000737:chemistry* / Q000528:radiation effects; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects; D055117:Curing Lights, Dental; D003764:Dental Materials / Q000737:chemistry* / Q000528:radiation effects; D000431:Ethanol / Q000737:chemistry; D006244:Hardness; D006801:Humans; D008027:Light; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry / Q000528:radiation effects; D063225:Organically Modified Ceramics; D055668:Photochemical Processes; D011829:Radiation Dosage; D012821:Silanes / Q000737:chemistry* / Q000528:radiation effects; D012833:Siloxanes / Q000737:chemistry / Q000528:radiation effects; D012997:Solvents / Q000737:chemistry*; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D003188:Composite Resins; D003764:Dental Materials; C509998:Grandio; D008689:Methacrylates; D063225:Organically Modified Ceramics; D012821:Silanes; D012833:Siloxanes; D012997:Solvents; C479084:admira; C507210:premise composite resin; D014867:Water; D000431:Ethanol