Colorimetric evaluation of the influence of five different restorative materials on the color of veneered densely sintered alumina.
OBJECTIVE
Since the introduction of densely sintered alumina ceramic material in prosthetic dentistry for the fabrication of all-ceramic crowns, no scientific data have been presented on the color of these restorations in combination with different restorative materials. The purpose of this in vitro study was to evaluate the influence of five different restorative materials used for implant abutments or posts and cores on the color of veneered densely sintered alumina.


METHODS
Sixty discs, 0.6 mm in thickness and 10 mm in diameter, were made out of densely sintered alumina ceramic material (Procera, Nobel Biocare, Gothenburg, Sweden) and veneered using feldspathic porcelain (AllCeram, Ducera, Rosbach, Germany) for a total thickness of 2 mm. Ten of the discs were evaluated colorimetrically using the CIE, L*, a*, b* system (control group). In addition, 50 discs, 3 mm in thickness and identical diameter, were fabricated using the following restorative materials (five different materials used on 10 specimens each): (1) high-precious gold alloy, (2) aluminum-oxide ceramic material, (3) titanium metal alloy, (4) yttrium-stabilized zirconium dioxide ceramic material, and (5) glass-ceramic material. The 50 veneered densely sintered alumina specimens were bonded to the 50 restorative specimens using an autopolymerizing luting composite. L*, a*, b* color coordinates were measured 10 times for each veneered densely sintered alumina specimen. Color differences were calculated using the equation DeltaE = [(DeltaL*)2 + (Deltaa*)2 + (Deltab*)2] 1/2. DeltaE values correspond to differences between the control group and each of the five materials groups.


RESULTS
Mean color differences (DeltaE) and SDs for each group were as follows: DeltaE (1) = 1.42 +/- 0.5, DeltaE (2) = 1.53 +/- 0.5, DeltaE (3) = 1.55 +/- 0.4, DeltaE (4) = 1.95 +/- 0.5, DeltaE (5) = 1.23 +/- 0.3. All restorative materials induced changes to the densely sintered alumina color relative to the original color. One-way analysis of variance (ANOVA) tests showed statistically significant differences in DeltaE between the groups; however, the Student-Newman-Keuls test revealed that the only statistically significant difference was between groups 4 and 5. Color differences between the groups were not visually perceivable (DeltaE < 2).


CONCLUSIONS
Within the limits of this in vitro study, veneered densely sintered alumina adhesively fixed with dentine-like cement, successfully masks the shade of different metal or ceramic restorative materials.
Department of Operative Dentistry, School of Dentistry, National and Kapodistrian University, Athens, Greece. koutayas@otenet.gr
Spiridon-Oumvertos
SO
Koutayas
Aphrodite
A
Kakaboura
Amr
A
Hussein
Jörg-Rudolf
JR
Strub
D000537:Aluminum Oxide / Q000737:chemistry*; D000704:Analysis of Variance; D003116:Color; D003124:Colorimetry; D003722:Dental Alloys / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design; D003801:Dental Veneers; D005898:Glass / Q000737:chemistry; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D016876:Metal Ceramic Alloys / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D014025:Titanium / Q000737:chemistry; D015019:Yttrium / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry
C105314:AllCeram; D003722:Dental Alloys; D003764:Dental Materials; D006047:Gold Alloys; D016876:Metal Ceramic Alloys; C077451:Procera; D019279:Resin Cements; D003776:Dental Porcelain; D015019:Yttrium; D015040:Zirconium; D014025:Titanium; D000537:Aluminum Oxide; C028541:zirconium oxide