title: Influence of the bleaching interval on the luminosity of long-term discolored enamel-dentin discs.
abstract: OBJECTIVE
  The aim of this study is to investigate the influence of changing the sodium perborate-tetrahydrate (PBS-4) at a 4-day interval versus no change after 16 days of internal bleaching.
  
  
  METHODS
  Two hundred and ten bovine enamel-dentin discs were discolored for 3.5 years with 14 different endodontic materials. All groups with a discoloring index of ∆E (mean) ≥ 5.5 were included in the present investigation: ApexCal (APCA), MTA white + blood (WMTA+BL), Portland cement + blood (PC+BL), blood (BL), MTA gray (GMTA), MTA gray + blood (GMTA+BL), Ledermix (LED), and triple antibiotic paste containing minocycline (3Mix). Fourteen specimens of each group were randomly assigned into two treatment groups: (1) no change of the PBS-4 (n = 7); (2) change of the PBS-4 every 4 days (n = 7). Color measurements were taken at 10 different time intervals and the L*a*b* values were recorded with a spectrophotometer (VITA Easyshade® compact).
  
  
  RESULTS
  In the group 3Mix, significantly better results were achieved by changing the bleaching agent every 4 days (P = 0.0049; q = 0.04), while the group WMTA+BL indicated better results by no change of the bleaching agent (P = 0.0222, q = 0.09). All remaining groups showed no statistical difference between the two treatment procedures.
  
  
  CONCLUSIONS
  Moderate discolorations can be successfully treated without changing the bleaching agent over a period of 16 days. Changing the sodium perborate-tetrahydrate every 4 days is preferred in case of severe discolored enamel-dentin discs only.
  
  
  CONCLUSIONS
  This approach may offer a reduced number of clinical appointments and a secondary cost reduction to the patient.
authors.affiliation: Department of Periodontology, Endodontology and Cariology, University of Basel, Hebelstrasse 3, 4056, Basel, Switzerland. lucia.zaugg@unibas.ch.
authors.forename: Lucia K
authors.initials: LK
authors.lastname: Zaugg
authors.affiliation: Department of Reconstructive Dentistry and Temporomandibular Disorders, University of Basel, Hebelstrasse 3, 4056, Basel, Switzerland.
authors.forename: Patrik
authors.initials: P
authors.lastname: Lenherr
authors.affiliation: European Molecular Biology Laboratory, Computational and Structural Biology Unit, Meyerhofstrasse 1, 69117, Heidelberg, Germany.
authors.forename: Judith B
authors.initials: JB
authors.lastname: Zaugg
authors.affiliation: Department of Periodontology, Endodontology and Cariology, University of Basel, Hebelstrasse 3, 4056, Basel, Switzerland.
authors.forename: Roland
authors.initials: R
authors.lastname: Weiger
authors.affiliation: Department of Conservative Dentistry and Periodontology, University of Würzburg, Pleicherwall 2, 97070, Würzburg, Germany.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Krastl
mesh_terms: D017607:Aluminum Compounds; D000818:Animals; D001881:Borates; D017610:Calcium Compounds; D002417:Cattle; D002939:Ciprofloxacin; D003707:Demeclocycline; D003738:Dental Cements; D003743:Dental Enamel / Q000187:drug effects*; D003804:Dentin / Q000187:drug effects*; D004338:Drug Combinations; D066298:In Vitro Techniques; D008795:Metronidazole; D008911:Minocycline; D010087:Oxides; D011897:Random Allocation; D012387:Root Canal Filling Materials; D017640:Silicates; D013053:Spectrophotometry; D013997:Time Factors; D014073:Tooth Bleaching / Q000379:methods; D058205:Tooth Bleaching Agents / Q000737:chemistry*; D014075:Tooth Discoloration / Q000628:therapy*; D014222:Triamcinolone Acetonide
chemical_list: C551230:3Mix ointment; D017607:Aluminum Compounds; C546890:ApexCal; D001881:Borates; D017610:Calcium Compounds; D003738:Dental Cements; D004338:Drug Combinations; D010087:Oxides; D012387:Root Canal Filling Materials; D017640:Silicates; D058205:Tooth Bleaching Agents; C086631:mineral trioxide aggregate; D008795:Metronidazole; D002939:Ciprofloxacin; D003707:Demeclocycline; C001527:Ledermix; D014222:Triamcinolone Acetonide; D008911:Minocycline; C027707:sodium perborate
keywords: Bovine tooth model; Change interval; Discoloration; Internal bleaching; Sodium perborate-tetrahydrate