[Study on color stability of composite resins for a facing crown polymerized with high output photo-curing unit].
OBJECTIVE
This study investigated the color stability of composite resins for a facing crown cured with a high output photo-curing unit (Hyper LII, YAMAHACHI DENTAL MFG., CO.).


METHODS
Four brands of composite resins for a facing crown after polymerization with Hyper LII were immersed in coffee. Color measurement was carried out before and 1, 2, and 4 weeks after immersion, and the results were compared.


RESULTS
1. After immersion in coffee, the L* values decreased gradually, the a* values showed little change, and the b* values increased gradually in all resins. 2. The difference in the color difference values (deltaE*ab) between each material became greater with time; the deltaE*ab after 4 weeks immersion were from 3.0 [Dentacolor (DEC), dentin specimen] to 6.3 [Solidex (SOL), enamel specimen] on polished surfaces, and from 0.9 [Gradia (GRA), dentin specimen] to 5.2 (SOL, enamel specimen) on non-polished surfaces. However, the deltaE*ab were 1/3 to 1/5 better than those of our previous studies. 3. The enamel specimens showed larger color differences than the dentin specimens. 4. When polished surfaces were compared with non-polished surfaces, Cesead II (CEII), DEC and SOL showed almost equal color differences while GRA showed larger color differences.


CONCLUSIONS
This study suggests that composite resins for a facing crown cured with a high output photo-curing unit result in a decrease of color changes with time and an improvement of color stability.
Yoshimoto
Namie
N
Department of Prosthodontics, Showa University School of Dentistry. namie@senzoku.showa-u.ac.jp
Akasaka
Ayako
A
Warita
Kenji
K
Ishiura
Yuichi
Y
Higuchi
Daisuke
D
Hu
Shuhai
S
Kawawa
Tadaharu
T
D000180:Acrylic Resins; D003116:Color; D003188:Composite Resins; D003442:Crowns; D011108:Polymers; D011140:Polyurethanes
D000180:Acrylic Resins; C029012:Composite Dental Resin; D003188:Composite Resins; D011108:Polymers; D011140:Polyurethanes