title: Effects of whitening dentifrice on yttria-stabilized tetragonal zirconia polycrystal surfaces after simulating brushing.
abstract: BACKGROUND
  The changes that occur after brushing yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) are unknown. These changes may favor the retention of microorganisms and chemisorption of water, impairing its longevity.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to evaluate the effects of a whitening dentifrice on Y-TZP surfaces after simulating 10 years of brushing.
  
  
  METHODS
  Seventy-two bar-shaped specimens (20×4×1.2 mm) were divided into 4 groups: storage in distilled water (SW, control), brushing with distilled water (BW), brushing with dentifrice (BD), and brushing with whitening dentifrice (BWD). Brushing was conducted using a linear brushing machine (878400 cycles, 0.98 N, soft toothbrush). The mean roughness (Ra) was analyzed with a profilometer and the superficial topography with scanning electron microscopy (SEM) at baseline and after treatment. Crystalline phases were characterized using x-ray diffraction. Baseline and posttreatment Ra were analyzed using the 1-way ANOVA and Tukey HSD multiple comparison test; the paired t test was used for intragroup comparison (all α=.05).
  
  
  RESULTS
  The Ra (μm) means (before/after treatment) were SW 0.28/0.28; BW 0.32/0.31; BD 0.28/0.36; BWD 0.30/0.20. No statistically significant difference was found for Ra at baseline (P=.108) than for posttreatment results (P<.001); the BD group had higher Ra values when compared with baseline (P=.019); the BWD group had the lowest values (P<.001). The BD surfaces showed pronounced scratches and detachment of the surface, while BWD showed smoother surfaces; similar crystallographic results among groups were observed.
  
  
  CONCLUSIONS
  Brushing Y-TZP with conventional dentifrice increased roughness, while brushing with whitening dentifrice reduced roughness. Neither dentifrice changed the crystallographic phases after brushing.
authors.affiliation: Professor, Department of Dental Materials and Prosthodontics, Araraquara School of Dentistry (UNESP) São Paulo State University, São Paulo, Brazil. Electronic address: laizamgfais@foar.unesp.br.
authors.forename: Lígia Antunes Pereira
authors.initials: LA
authors.lastname: Pinelli
authors.affiliation: Undergraduate student, Department of Dental Materials and Prosthodontics, Araraquara School of Dentistry (UNESP) São Paulo State University, São Paulo, Brazil.
authors.forename: Amanda Caroline
authors.initials: AC
authors.lastname: Gimenes Olbera
authors.affiliation: Graduate student, Department of Dental Materials and Prosthodontics, Araraquara School of Dentistry (UNESP) São Paulo State University, São Paulo, Brazil.
authors.forename: Lucas Miguel
authors.initials: LM
authors.lastname: Candido
authors.affiliation: Graduate student, Department of Dental Materials and Prosthodontics, Araraquara School of Dentistry (UNESP) São Paulo State University, São Paulo, Brazil.
authors.forename: Larissa Natiele
authors.initials: LN
authors.lastname: Miotto
authors.affiliation: Postdoctoral Researcher, Department of Physical Chemistry, Araraquara School of Dentistry (UNESP) São Paulo State University, São Paulo, Brazil.
authors.forename: Selma Gutierrez
authors.initials: SG
authors.lastname: Antonio
authors.affiliation: Postdoctoral Researcher, Department of Dental Materials and Prosthodontics, Araraquara School of Dentistry (UNESP) São Paulo State University, São Paulo, Brazil.
authors.forename: Laiza Maria Grassi
authors.initials: LM
authors.lastname: Fais
mesh_terms: D003802:Dentifrices / Q000009:adverse effects*; D066298:In Vitro Techniques; D013499:Surface Properties; D014099:Toothbrushing / Q000009:adverse effects*; D015019:Yttrium / Q000592:standards; D015040:Zirconium / Q000592:standards
chemical_list: D003802:Dentifrices; C499362:yttria stabilized tetragonal zirconia; D015019:Yttrium; D015040:Zirconium