title: Discoloration of the mucosa caused by different restorative materials - a spectrophotometric in vitro study.
abstract: OBJECTIVE
  To evaluate the discoloration of the mucosa caused by different ceramic and metal-based materials.
  
  
  METHODS
  On six pig maxillae, trap-door flaps were prepared bilaterally. Different ceramic and metal-based specimens were placed underneath the flap. To simulate increasing mucosal thicknesses (MC), connective tissue grafts (CTGs) were harvested. Spectrophotometric measurements were performed prior to flap elevation (TBL) and for each material under the flap alone (1 mm MC) (TMC1), with a 1-mm CTG (2-mm MC) (TMC2) and with a 2-mm CTG (3-mm MC) (TMC3). Tested materials were as follows: Zr1 (zirconia), Zr2 (zirconia + pink ceramic), Zr3 (zirconia), Zr4 (fluorescent zirconia), Zr5 (zirconia), Zr6 (high translucent zirconia), Zr7 (low translucent zirconia) and Zr8 (low translucent zirconia), Gol (gold alloy), Ti1 (titanium alloy), Ti2 (anodized gold-shaded titanium alloy) and Ti3 (anodized pink-shaded titanium alloy). Color differences (ΔE) were calculated comparing the measurement of the native tissue (TBL) and the measurements with varying mucosal thicknesses (TMC1-3).
  
  
  RESULTS
  For ceramic materials, the median ΔE values for the different time-point comparison ranged as follows: 3.80 (Zr4) - 7.47 (Zr2) (pooled); 3.15 (Zr4) - 8.13 (Zr2) (TBL-TMC1); 3.39 (Zr4) - 7.24 (Zr2) (TBL-TMC2); 4.31 (Zr8) - 6.99 (Zr2) (TBL-TMC3). For metal-based materials, the median ΔE values were as follows: 4.20 (Gol) - 5.82 (Ti3) (pooled); 3.21 (Gol) - 13.56 (Ti1) (TBL-TCM1); 4.0 (Ti1) - 5.27 (Gol) (TBL-TCM2); 3.11 (Ti1) - 5.11 (Gol) (TBL-TCM2). The comparison of the materials and the time points showed in the nonparametric linear mixed model a significant interaction effect between material and time point (P < 0.001). The side was not a significant main effect, nor as term in an interaction with the other two effects.
  
  
  CONCLUSIONS
  Reconstructive materials result in an evident discoloration of the mucosal tissue, tending to decrease with increasing mucosal thickness. The use of fluorescent zirconia (ceramic materials) or gold alloy (metal-based materials) lead to the least discoloration.
authors.affiliation: Clinic for Fixed and Removable Prosthodontics and Dental Material Science, Center of Dental Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Alexis
authors.initials: A
authors.lastname: Ioannidis
authors.affiliation: Center of Dental Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Elena
authors.initials: E
authors.lastname: Cathomen
authors.affiliation: Clinic for Fixed and Removable Prosthodontics and Dental Material Science, Center of Dental Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Jung
authors.affiliation: Division of Fixed Prosthodontics and Biomaterials, Center of Dental Medicine, University of Geneva, Geneva, Switzerland.
authors.forename: Vincent
authors.initials: V
authors.lastname: Fehmer
authors.affiliation: Institute of Mathematical Statistics and Actuarial Science, University of Berne, Berne, Switzerland.
authors.forename: Jürg
authors.initials: J
authors.lastname: Hüsler
authors.affiliation: Clinic for Fixed and Removable Prosthodontics and Dental Material Science, Center of Dental Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Thoma
mesh_terms: D000818:Animals; D002516:Ceramics; D003116:Color; D003764:Dental Materials / Q000009:adverse effects*; D066298:In Vitro Techniques; D008422:Materials Testing; D008670:Metals; D009061:Mouth Mucosa / Q000473:pathology*; D013053:Spectrophotometry; D013552:Swine
chemical_list: D003764:Dental Materials; D008670:Metals
keywords: abutment; ceramic; color; dental implant; metal; spectrophotometer