title: Effect of at-home whitening strips on the surface roughness and color of a composite and an ormocer restorative material.
abstract: OBJECTIVE
  Oxygenating agents like carbamide peroxide or H(2) O(2) are commonly used whitening agents. They have varying influence on the color and surface roughness of resin-based restorative materials and teeth. The aim of this study was to evaluate the effect of an at-home peroxide whitening agent applied through a whitening strip on the color and surface roughness of a nanofilled composite resin and an ormocer-based resin.
  
  
  METHODS
  Disc-shaped (2 mm thick, 10 mm diameter) nanofilled resin composite (n = 10) and ormocer (n = 10) specimens were prepared. All specimens were treated with a whitening strip. Whitening procedures were performed applying a 6.5% hydrogen peroxide whitening strip (Crest White Strips Professional) for 30 minutes twice each day for a period of 21 consecutive days. During the test intervals, the specimens were rinsed under running distilled water for 1 minute to remove the whitening agents and immersed in 37°C distilled water until the next treatment. Surface roughness and color of the specimens were measured with a profilometer and a colorimeter, respectively, before and after whitening. Color changes were calculated (ΔE) using L*, a*, and b* coordinates. Repeated measures of variance analysis and Duncan test were used for statistical evaluation (α= 0.05).
  
  
  RESULTS
  The average surface roughness of composite increased from 1.4 Ra to 2.0 Ra, and from 0.8 Ra to 0.9 Ra for the ormocer material; however, these changes in roughness after whitening were not significant (p > 0.05). Also, when two materials were compared, the surface roughness of restorative materials was not different before and after whitening (p > 0.05). L* and b* values for each material changed significantly after whitening (p < 0.05). ΔE values (before/after whitening) calculated for composite (11.9) and ormocer (16.1) were not significantly different from each other (p > 0.05).
  
  
  CONCLUSIONS
  The tested whitening agent did not affect the surface roughness of either resin-based restorative material. Both materials became brighter after whitening. The behavior of the materials in the yellow/blue axis was opposite to each other after whitening. Each material had clinically unacceptable color change after whitening (ΔE > 5.5); however, the magnitude of the color change of materials was similar (p > 0.05). According to the results of this study, with the use of materials tested, patients should be advised that existing composite restorations may bleach along with the natural teeth, and replacement of these restorations after whitening may not be required.
authors.affiliation: Department of Prosthodontics, Faculty of Dentistry, University of Ankara, Ankara, Turkey.
authors.forename: Ayhan
authors.initials: A
authors.lastname: Gurbuz
authors.forename: Pelin
authors.initials: P
authors.lastname: Ozkan
authors.forename: Kerem
authors.initials: K
authors.lastname: Yilmaz
authors.forename: Burak
authors.initials: B
authors.lastname: Yilmaz
authors.forename: Rukiye
authors.initials: R
authors.lastname: Durkan
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate; D003116:Color; D003188:Composite Resins; D003793:Dental Restoration, Permanent; D006861:Hydrogen Peroxide; D008422:Materials Testing; D053761:Nanocomposites; D063225:Organically Modified Ceramics; D011092:Polyethylene Glycols; D011109:Polymethacrylic Acids; D017797:Prosthesis Coloring; D013499:Surface Properties; D058205:Tooth Bleaching Agents
chemical_list: D003188:Composite Resins; D063225:Organically Modified Ceramics; D011109:Polymethacrylic Acids; D058205:Tooth Bleaching Agents; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; D006861:Hydrogen Peroxide