title: The effect of bleaching agents on the surface hardness of tooth colored restorative materials.
abstract: OBJECTIVE
  The aim of this study was to evaluate the effect of at-home (Opalesence/Dr. kit 15%, Ultradent, Products, Inc. South Jordan, UT, USA) and in-office (Superoxol 35%, Sultan Chemists, Inc., Englewood, NJ, USA) bleaching on the surface hardness of the following tooth colored restorative materials: composite resin, Point-4 (P4), Kerr Corporation, Orange, CA, USA; ormocer, Admira (AD),VOCO, Germany; compomer Dyract AP (DY), Dentsply DeTrey GmbH, Germany; and resin modified glass ionomer cement, Fuji II LC (FL), GC Corporation, Japan.
  
  
  METHODS
  Sixty specimens were prepared; 15 specimens of each material (each group n = 5, control after 15 days, at-home and in-office). All specimens were stored in distilled water at room temperature for 24 hrs before testing. A universal testing machine (Micromet 2100 series micro hardness testers) was used for testing Vicker's surface hardness for the three groups for every tested material. All results were statistically analyzed with one way analysis of variance (ANOVA), Post hoc Tukey HSD tests (P < 0.05), and percentage changes for Tukey.
  
  
  RESULTS
  All the tested materials showed an increase in Vicker's surface hardness between base line (24 hrs) and the control group after 15 days storage in distilled water except DY which showed a decrease in surface hardness. All tested materials showed a decrease in surface hardness from control group after 15 days and both at-home and in-office bleaching agents except DY which showed increased values.
  
  
  CONCLUSIONS
  At-home as well as in-office bleaching agents have a softening effect on some tooth colored restorative material, and the patient must be aware before using them.
authors.affiliation: Department of Restorative Dental Science, College of Dentistry, King Saud University, Riyadh, Saudi Arabia. nmataher@hotmail.com
authors.forename: Nadia Malek
authors.initials: NM
authors.lastname: Taher
mesh_terms: D000704:Analysis of Variance; D000077463:Carbamide Peroxide; D002516:Ceramics / Q000737:chemistry; D020770:Compomers / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003793:Dental Restoration, Permanent / Q000379:methods*; D003799:Dental Stress Analysis; D004338:Drug Combinations; D005899:Glass Ionomer Cements / Q000737:chemistry; D006244:Hardness; D006861:Hydrogen Peroxide / Q000737:chemistry; D008422:Materials Testing; D063225:Organically Modified Ceramics; D016877:Oxidants / Q000737:chemistry*; D010545:Peroxides / Q000737:chemistry*; D012117:Resins, Synthetic / Q000737:chemistry; D012821:Silanes / Q000737:chemistry; D014073:Tooth Bleaching; D014508:Urea / Q000031:analogs & derivatives / Q000737:chemistry
chemical_list: D020770:Compomers; D003188:Composite Resins; D004338:Drug Combinations; C088486:Dyract; C079765:Fuji II LC cement; D005899:Glass Ionomer Cements; D063225:Organically Modified Ceramics; D016877:Oxidants; D010545:Peroxides; D012117:Resins, Synthetic; D012821:Silanes; C451741:point 4 composite resin; D000077463:Carbamide Peroxide; D014508:Urea; D006861:Hydrogen Peroxide