title: The effect of polishing techniques on the surface roughness and color change of composite resins.
abstract: BACKGROUND
  Surface characteristics may affect the color change and surface roughness of composite resins.
  
  
  OBJECTIVE
  This study evaluated the surface roughness and color change of a hybrid, a microhybrid, and a nanohybrid composite resin polished with the use of polishing discs, wheels, and a glaze material.
  
  
  METHODS
  Fifty discs (10 x 2 mm) were fabricated for each composite resin (nanohybrid, Grandio; microhybrid, Filtek Z250; hybrid, Quadrant Universal LC) for a total of 150 discs, prepared using polyester strips and divided into 5 groups of 10. One of the groups served as control (C) and had no surface treatment (n=10). The specimens of the experimental groups were ground with 1000-grit silicon carbide paper. In 4 experimental groups (n=10), specimen surfaces were polished with polishing discs (D) (Sof-Lex), with polishing wheels (W) (Astropol), with polishing discs preceding the glaze application (DG) (Biscover), or with polishing wheels preceding the glaze application (WG), respectively. Color was assessed using a small area colorimeter. The color differences (DeltaE) values between the specimens of Group C and the experimental groups were calculated, and the data were compared using 2-way analysis of variance (ANOVA) (alpha=.05). Subsequently, the surface roughness (Ra) of the specimens was evaluated using a profilometer, and the data were analyzed by 2-way ANOVA followed by a Tukey multiple comparisons test (alpha=.05).
  
  
  RESULTS
  The polishing technique and type of composite resin significantly affected the Ra and DeltaE values of the composite resins (P<.001). While the use of polishing wheels produced the highest Ra values when compared to the other polishing techniques (P<.001), the nanohybrid composite resin showed the lowest Ra values compared to the other composite resins in the control groups (P<.001). All of the nanohybrid and microhybrid composite resin groups were found to be significantly different from each other in terms of color difference (P<.001).
  
  
  CONCLUSIONS
  The highest Ra values were obtained with hybrid composite resins due to the size of the filler particles that were exposed after polishing. Although the smoothest surfaces were obtained with polyester strips, the use of glaze material after polishing discs or polishing wheels resulted in significantly lower Ra and DeltaE values than the use of the latter alone. The glaze appears to fill the structural microdefects and provide a more uniform, regular surface.
authors.affiliation: Department of Prosthetic Dentistry, Faculty of Dentistry, Ondokuz Mayis University, 55139 Kurupelit, Samsun, Turkey. dsarac@omu.edu.tr
authors.forename: Duygu
authors.initials: D
authors.lastname: Sarac
authors.forename: Y Sinasi
authors.initials: YS
authors.lastname: Sarac
authors.forename: Safak
authors.initials: S
authors.lastname: Kulunk
authors.forename: Cagri
authors.initials: C
authors.lastname: Ural
authors.forename: Tolga
authors.initials: T
authors.lastname: Kulunk
mesh_terms: D000704:Analysis of Variance; D003116:Color; D003124:Colorimetry; D003188:Composite Resins; D003775:Dental Polishing / Q000379:methods*; D003793:Dental Restoration, Permanent; D018709:Statistics, Nonparametric; D013499:Surface Properties
chemical_list: D003188:Composite Resins; C444701:Filtek Z250; C509998:Grandio; C514243:quadrant universal LC