Influence of ceramic thickness on mechanical properties and polymer structure of dual-cured resin luting agents.
OBJECTIVE
To investigate the influence of ceramic thickness on the mechanical properties and polymer structure (degree conversion and cross-linking density) of three dual-cured resin luting agents.


METHODS
Three dual-cured resin luting agents [Linkmax HV (GC), Nexus 2 (Kerr), and Variolink IIHV (Ivoclar-Vivadent)] were polymerized with or without 800 mW/cm2 irradiation through 0-3-mm-thick GN-I (GC) machinable ceramic. Bar-shape specimens were subjected to three-point bending to determine flexural strength (FS) and elastic modulus (EM) after dry storage at 37 degrees C for 24 h. Knoop hardness was measured on the irradiated surface of disk-shaped specimens before (KHN1) and after (KHN2) storage of 100% ethanol solution at 37 degrees C for 24 h. KHN1 and KHN2 were estimated as indirect indicators of degree of conversion (DC) and cross-linking density, respectively. Data were analyzed by one-way ANOVA and Student-Newman-Keuls test for each luting agent, and four mechanical properties were subjected to regression analysis.


RESULTS
For three resin luting agents with dual-cured mode, FS, EM, KHN1, and KHN2 decreased with the increase of ceramic thickness. FS except for Nexus 2 and EM for three resin luting agents had a positive linear relationship with both KHN1 and KHN2.


CONCLUSIONS
The variables tested behaved differently. When the ceramic thickness increased, the chemical cured components of dual-cured resin luting agents did not produce significant compensation for all variables. Mechanical properties and polymer structure of dual-cured resin luting agents was dependent on the intensity of light irradiation.
Division of Applied Prosthodontics, Nagasaki University, Graduate School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki 852-8588, Japan.
Xiangfeng
X
Meng
Keiichi
K
Yoshida
Mitsuru
M
Atsuta
D000538:Aluminum Silicates / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry / Q000528:radiation effects; D003776:Dental Porcelain / Q000737:chemistry*; D017220:Dentin-Bonding Agents / Q000737:chemistry* / Q000528:radiation effects; D004548:Elasticity; D000431:Ethanol / Q000737:chemistry; D006244:Hardness; D006801:Humans; D008027:Light; D008422:Materials Testing; D018583:Pliability; D011108:Polymers / Q000737:chemistry / Q000528:radiation effects; D019279:Resin Cements / Q000737:chemistry* / Q000528:radiation effects; D012997:Solvents / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors
D000538:Aluminum Silicates; D003188:Composite Resins; D017220:Dentin-Bonding Agents; C470486:Linkmax; C433206:Nexus; D011108:Polymers; D019279:Resin Cements; D012997:Solvents; D003776:Dental Porcelain; C078519:leucite; C103502:Variolink; D000431:Ethanol