R.E. KERBY, L.A. KNOBLOCH, B. GREGG, and S. SCHRICKER, Ohio State University, Columbus, USA
Objective: The flexural strength (FS), flexural
modulus (Ef), water sorption (WS) and water solubility (Wsol) of seven urethane
dimethacrylate resins (three aliphatic [UHP, UTP and UTB], two aromatic
[UXY and UXB], and a cycloaliphatic [UCY] urethane, two of which contain
pendant phenyl ether moieties [UHP and UTP], and the commercially available
aliphatic resin [UDMA]) were evaluated. Method: Resins were filled
(20% w/w) with silanated colloidal silica. Beam shaped specimens (25mm x
2.5mm x 2.5mm) (n=10) were prepared (LC 80 sec) and stored in 37°C ± 2°C
distilled water and tested at seven days on an Instron utilizing a three-point
loading jig at a 0.75 mm/min displacement rate. Disc shaped specimens
(15mm x 0.5mm) (n=3) were light cured and desiccated to a constant mass.
Specimens were then placed in 37°C distilled water for 7 days, weighed, and
re-desiccated to a constant mass. Results: Mean values for
flexural strength (MPa), flexural modulus (GPa), water sorption and solubility
(ug/mm3) with standard deviations are listed below:
|
Resin
|
FS
|
E(f)
|
WS(7 days)
|
Wsol(7 days)
|
|
UDMA
|
117.5 (7.6)
|
3.03 (0.18)
|
33.6 (2.6)
|
8.0 (0.5)
|
|
UXY
|
111.1 (9.5)
|
3.60 (0.21)
|
31.9 (1.3)
|
8.3 (0.9)
|
|
UCY
|
98.3 (14.1)
|
3.36 (0.23)
|
36.4 (0.5)
|
11.4 (0.5)
|
|
UTB
|
91.1 (9.2)
|
2.46 (0.15)
|
22.8 (1.8)
|
5.5 (0.5)
|
|
UTP
|
79.3 (8.0)
|
2.60 (0.23)
|
19.5 (0.5)
|
8.9 (0.5)
|
|
UHP
|
78.0 (11.3)
|
2.64 (0.46)
|
18.6 (1.0)
|
8.6 (1.0)
|
|
UXB
|
74.2 (7.2)
|
3.08 (0.18)
|
25.0 (0.8)
|
5.9 (1.4)
|
Conclusions: ANOVA (p<0.001) and Ryan-Einot-Gabriel-Welsch
Multiple Range Test (p<0.05) indicated significant differences between
resins for all four parameters. Lower molecular weight resins, which
would result in increased crosslinking, exhibited higher mean flexural
strengths. Resins with pendant phenyl ether and ethyl groups tended to
show decreased water sorption.
|