title: [The research on optical properties of four all-ceramic veneer materials].
abstract: OBJECTIVE
  To analyze the color parameters and translucency of four frequently-used veneer materials.
  
  
  METHODS
  Forty disc specimens[(1.00±0.01) mm in thickness, 10 mm in diameter] were fabricated according to the manufacturer's instructions with IPS Empress(®) CAD[A2, high translucency (HT)], IPS e.max(®) Press(A2, HT), IPS e.max(®) CAD (A2, HT) and VITABLOCS(®) Mark II (A2) respectively and were divided into Groups A, B, C, D. All of the specimens were ground and polished on a grinding machine. Then color parameters (L*, a*, b*) and transmittance (τ) were measured using spectrocolorimeter and transmissivity testing device. The color parameters of the specimens were compared to the color parameters of A2 shade of Ivoclar Vivadent A-D shade guide. The data were analyzed with one-way analysis of variance (ANOVA), and mean values were compared by the Tukey's test (α = 0.05).
  
  
  RESULTS
  There was no statistical difference between the color parameters L*, a*, b* and C*ab of Group A and Group D (P > 0.05). But the color parameters of those two ceramic materials were statistically different from the color parameters of Group B and Group C (P < 0.05). There was no statistical difference between color parameters b* and C*ab of Group B and Group C(P > 0.05). However, the color parameters L* and a* of the two materials were statistically different(P < 0.05). The color differences (ΔE) between Group A, B, C, D and standard A2 were 6.05±0.12, 5.11±0.27, 3.73±0.27, 6.30±0.38 respectively. The transmittances of Group A, B, C, D were (29.69±0.31)%, (25.83±0.36) %, (28.92±0.47)% and (26.94±0.33)% respectively.
  
  
  CONCLUSIONS
  The color parameters of these four materials are different. Their transmittance are relatively high but statistically different. The color difference (ΔE) between IPS e.max(®) CAD (A2, HT) and standard A2 is lowest among all the groups.
authors.affiliation: Department of Prosthodontics, Institute and Hospital of Stomatology, Nanjing University Medical School, Nanjing 210008, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Gao
authors.affiliation: Department of Prosthodontics, Institute and Hospital of Stomatology, Nanjing University Medical School, Nanjing 210008, China. Email: l_xiaoping@yahoo.com.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Luo
authors.affiliation: Department of Prosthodontics, Institute and Hospital of Stomatology, Nanjing University Medical School, Nanjing 210008, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Li
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry*; D003116:Color; D003188:Composite Resins / Q000737:chemistry; D003776:Dental Porcelain / Q000737:chemistry; D003801:Dental Veneers; D055620:Optical Phenomena; D011140:Polyurethanes / Q000737:chemistry
chemical_list: D000180:Acrylic Resins; D003188:Composite Resins; D011140:Polyurethanes; C513703:Vivadent; D003776:Dental Porcelain