title: Evaluation of pH Levels and Surface Roughness After Bleaching and Abrasion Tests of Eight Commercial Products.
abstract: OBJECTIVE
  This in vitro study evaluated the effect of different bleaching protocols and the variation of pH levels of bleaching gels regarding roughness and wear of bovine enamel, after in-office bleaching protocols and brushing.
  
  
  METHODS
  Ninety fragments were randomly divided into nine groups: C, control; WHP15, 35% hydrogen peroxide (HP) (Whiteness HP, FGM) three gel applications of 15 min each, three sessions with 1 week intervals; WHP45, 35% HP (Whiteness HP) one application/45 min, three sessions with 1 week intervals; LPS, 35% HP (Lase Peroxide, DMC) plus hybrid light (HL) [light-emitting diode (LED)/diode laser], four applications/7 min 30 sec (6 min of HL activation), one session; LPSII, 25% HP (Lase Peroxide II, DMC) plus HL, four applications/7 min 30 sec (6 min of HL activation), one session; LPL, 15% HP (Lase Peroxide Light, DMC) four applications/7 min 30 sec (6 min of HL activation), one session; WO, 35% HP (Whitegold Office, Dentsply) three applications/15 min, three sessions with 1 week intervals; WBC40, 35% HP (Whiteness HP Blue Calcium, FGM) one application/40 min, three sessions with 1 week intervals; and WBC50, 20% HP (Whiteness HP Blue Calcium) one application/50 min, three sessions with 1 week intervals. The median pH values were determined utilizing a pH meter during the initial and final gel applications. A rugosimeter was utilized to evaluate the surface roughness (Ra) before and after bleaching and brushing (100,000 strokes), and the surface wear after brushing.
  
  
  RESULTS
  For the results of the pH values, there was a decrease in the pH levels from the initial to the final bleaching time, except for the WBC50. The WO and WBC40 groups exhibited higher pH values. For the results of roughness and wear, there was an increase in surface roughness and wear among the groups.
  
  
  CONCLUSIONS
  The pH values tended to decrease from the initial to the final bleaching. After tooth brushing, bleaching procedures with lower pH products provided a significant increase in enamel wear and surface roughness.
authors.affiliation: Department of Operative Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São Paulo , Bauru, São Paulo, Brazil .
authors.forename: Ana Carolina
authors.initials: AC
authors.lastname: Trentino
authors.affiliation: Department of Operative Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São Paulo , Bauru, São Paulo, Brazil .
authors.forename: Ana Flavia
authors.initials: AF
authors.lastname: Soares
authors.affiliation: Department of Operative Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São Paulo , Bauru, São Paulo, Brazil .
authors.forename: Marco Antonio Hungaro
authors.initials: MA
authors.lastname: Duarte
authors.affiliation: Department of Operative Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São Paulo , Bauru, São Paulo, Brazil .
authors.forename: Sérgio Kiyoshi
authors.initials: SK
authors.lastname: Ishikiriama
authors.affiliation: Department of Operative Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São Paulo , Bauru, São Paulo, Brazil .
authors.forename: Rafael Francisco Lia
authors.initials: RF
authors.lastname: Mondelli
mesh_terms: D000818:Animals; D002417:Cattle; D003743:Dental Enamel / Q000187:drug effects* / Q000528:radiation effects*; D005782:Gels; D006861:Hydrogen Peroxide / Q000494:pharmacology; D054023:Lasers, Semiconductor; D028022:Low-Level Light Therapy; D013499:Surface Properties / Q000528:radiation effects; D046509:Tissue Culture Techniques; D014073:Tooth Bleaching; D058205:Tooth Bleaching Agents / Q000494:pharmacology*
chemical_list: D005782:Gels; D058205:Tooth Bleaching Agents; D006861:Hydrogen Peroxide