title: Surface roughness of etched composite resin in light of composite repair.
abstract: OBJECTIVE
  In search for clinically effective composite repair protocols, the effect of various etching protocols on the surface roughness of composite resins with different filler composition were investigated.
  
  
  METHODS
  Of two composite resins (hybrid-filled Clearfil AP-X; nano-filled Filtek Supreme XT) specimens of 3mm thick with a diameter of 7 mm were prepared (n=24). The top surface was polished with 4000-grit SiC-abrasive paper and subjected to one of eight surface treatments: (n=3): negative control (NC), 37% phosphoric acid for 20s (37PA-20s), 3% hydrofluoric acid for 20s (3HF-20s), for 120 s (3HF-120 s), 9.6% hydrofluoric acid for 20s (9.6HF-20s), for 120 s (9.6%HF-120 s), 37PA-20s followed by 9.6%HF for 120 s (37PA-20s/9.6HF-120 s) and 9.6%HF for 120 s followed by 37PA-20s (9.6HF-120s/37PA-20s). Roughness (S(a)) was measured using a 3D noncontact optical interferometer (WYKO) and surface topography imaged by SEM. Multilevel models were used to estimate the variances within a sample and between samples in each group. Using the resulting overall variances and the means for each group, the eight groups were compared consecutively using t-tests (p<0.05).
  
  
  RESULTS
  The hybrid-filled composite resin demonstrated a significantly rougher surface than the nano-filled (p<0.05). For both composites 9.6%HF-120 s, 37PA-20s/9.6HF-120 s and 9.6%HF-120 s/37PA-20s resulted in a large increase in roughness compared to the other groups (p<0.05). For the hybrid-filled, the succeeding groups (37PA-20s, 3HF-20s, 3HF-120 s and 9.6HF-20s) resulted in a statistically significant increase in surface roughness (p<0.02). For the nano-filled only a statistically significant increase in roughness was found between 3HF-20s and 3HF-120 s (p<0.001) and between 9.6HF-20s and 9.6HF-120 s (p<0.001). SEM surface characterization revealed that the hybrid-filled composite resin was much more affected by etching than the nano-filled.
  
  
  CONCLUSIONS
  Composite resins should not be seen as a group of materials having identical properties when it comes to repair. The effect of etching will depend on the composition of the filler particles.
authors.affiliation: College of Dental Science, Department of Preventive and Restorative Dentistry, Radboud University Nijmegen Medical Centre, The Netherlands. b.loomans@dent.umcn.nl
authors.forename: B A C
authors.initials: BA
authors.lastname: Loomans
authors.forename: M V
authors.initials: MV
authors.lastname: Cardoso
authors.forename: N J M
authors.initials: NJ
authors.lastname: Opdam
authors.forename: F J M
authors.initials: FJ
authors.lastname: Roeters
authors.forename: J
authors.initials: J
authors.lastname: De Munck
authors.forename: M C D N J M
authors.initials: MC
authors.lastname: Huysmans
authors.forename: B
authors.initials: B
authors.lastname: Van Meerbeek
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods*; D000704:Analysis of Variance; D017609:Barium Compounds; D003188:Composite Resins; D058250:Dental Restoration Repair / Q000379:methods; D008422:Materials Testing; D008689:Methacrylates; D008855:Microscopy, Electron, Scanning; D053761:Nanocomposites; D010316:Particle Size; D012822:Silicon Dioxide; D018709:Statistics, Nonparametric; D013499:Surface Properties; D015040:Zirconium
chemical_list: D017609:Barium Compounds; C112828:Clearfil AP-X; D003188:Composite Resins; C474035:Filtek Supreme; D008689:Methacrylates; C102738:barium glass filler; D012822:Silicon Dioxide; D015040:Zirconium; C028541:zirconium oxide