title: The effect of bleaching agents on the surface topography of ceramometal dental alloys.
abstract: OBJECTIVE
  To study the effect of bleaching agents on the surface topography of ceramometal alloys.
  
  
  METHODS
  Three types of ceramometal alloys were used (gold, Ni-Cr, Co-Cr-Ti), and two types of bleaching agents (an agent intended for home use, one intended for use in the dental office) were studied. Forty-five specimens were constructed and divided according to the alloy type into three main groups, 15 specimens per group. Each group was further subdivided into three subgroups according to the type of bleaching agent used. The first subgroup (five specimens) was not subjected to any bleaching agent. The second and third subgroups were subjected to home and in-office bleaching agents, respectively.
  
  
  RESULTS
  Au alloy showed the least surface roughness when subjected to either of the two bleaching agents. Ni-Cr alloys showed the highest surface roughness for both the control and home bleached subgroups, and Co-Cr-Ti alloy showed the highest surface roughness in the in-office bleached subgroup. No statistically significant difference was found between the control subgroup and the home-bleached subgroup for either the Au alloy or the Co-Cr-Ti alloy. For the two alloys, both the control and home-bleached subgroups were statistically different from the in-office bleached subgroups. There was a statistically significant difference between the Ni-Cr control subgroup and the other two bleached subgroups, while there was no difference between the two bleached subgroups. Results also showed that increasing the concentration of bleaching agents increased the surface roughness of all the tested alloys. There was a statistical difference between the Ni-Cr alloy and the other two alloys in all tested subgroups except the in-office bleached subgroup, for which no difference between the surface roughness of the Ni-Cr alloy and the Co-Cr-Ti alloy was found. Scanning electron microscopic examination revealed surface deteriorations in the two bleached subgroups for all tested ceramometallic alloys.
  
  
  CONCLUSIONS
  Surface topographic alterations occurred as a result of the application of bleaching agents. These alterations increased with the increase of the carbamide peroxide concentration.
authors.affiliation: Department of Fixed Prosthodontics, Faculty of Dentistry, Minia University, Giza, Egypt. cherif.mohsen@gmail.com
authors.forename: Cherif A
authors.initials: CA
authors.lastname: Mohsen
mesh_terms: D000704:Analysis of Variance; D000077463:Carbamide Peroxide; D002858:Chromium Alloys; D003035:Cobalt; D006047:Gold Alloys; D008422:Materials Testing; D016876:Metal Ceramic Alloys; D008855:Microscopy, Electron, Scanning; D016877:Oxidants; D010545:Peroxides; D013499:Surface Properties; D014025:Titanium; D014073:Tooth Bleaching; D014508:Urea / Q000031:analogs & derivatives
chemical_list: D002858:Chromium Alloys; D006047:Gold Alloys; D016876:Metal Ceramic Alloys; D016877:Oxidants; D010545:Peroxides; D000077463:Carbamide Peroxide; D003035:Cobalt; D014508:Urea; D014025:Titanium