Abstracts of the Academy of Dental Materials Annual ... - IsiRed

e20 dental materials 26S (2010) e1–e84
and each wafer specimen were analyzed with a FTIR spectrometer
(BRUKER TENSOR 27, Germany) operating 16 scans at
4cm −1 resolution. Two and three way ANOVA were performed
on data of depth of cure and DC, respectively. Also, Tukey HSD
were performed at the 95% significance level.
Results: Statistical analysis revealed that the depth of cure
was affected by temperature and that the specimens cured at
37 ◦ C had statistically significant higher depth of cure compared
to the specimens cured at 5 ◦ C in both QTH and LED
groups (p < 0.01). Also, lower depth of cure was obtained with
QTH light curing system. Temperature increase also gave
higher DC. The results were statistically significant at three
different temperature groups (p < 0.05) regardless of the curing
unit. Also, a significant difference found between top and bottom
surfaces of specimens polymerized at room temperature.
However, no significant differences were found between top
and 2 mm depth on materials cured at 37 ◦ C and 5 ◦ C(p > 0.05).
Conclusions: Increasing the temperature of resin composites
has an important influence on its degree of conversion
and depth of cure. Thus, it may affect the physical properties.
Thus, increasing the shelf life of composites by storing
them in refrigerator may show a negative-influence on
polymerization.
doi:10.1016/j.dental.2010.08.049
42
Time-dependent fracture toughness of conventional glassionomer
cements
R. Belli, A. Petschelt, U. Lohbauer
Dental Clinic 1, University of Erlangen-Nuernberg, Germany
Objectives: To investigate the fracture toughness KIc of
three commercial dental glassionomer (GI) cements at different
storage intervals.
Materials and methods: Bars with dimensions of
25 mm × 2mm× 2 mm were produced out of Fuji IX GP
(GC Europe, Belgium), Ketac Molar (3M ESPE, Germany) and
Chemfil Rock (Dentsply, Germany) and stored for 3 h, 24 h, 7
days, and 21 days in water at 37 ◦C. After the storage periods,
sharp notches were cut on the lower side of the bars using
a diamond wheel saw blade and a razor blade. Fracture
toughness (n = 15) was measured in bending using the SENB
(single edge notched beam) method. The actual notch depth
for each specimen was measured after fracture under a
light microscope (40×). KIc values were analysed by two-way
ANOVA and mod. LSD test at p < 0.05.
Results: The major increase in KIc was measured between
3 h and 24 h for all the GI cements (p < 0.05). Chemfil
Rock presented the fastest initial toughness, reaching
0.44 ± 0.06 MPam0.5 after 3 h, whereas KIc for Fuji IX GP and
Ketac Molar were 0.36 ± 0.04 MPam0.5 and 0.34 ± 0.04 MPam0.5 ,
respectively at the same period. Final KIc at 21 days was
not statistically different from that of 24 h for Chemfil
Rock and Ketac Molar, while Fuji IX GP showed continuous
KIc increase over the test periods. However, final
(21 days) KIc were not statistically different for the three
GI systems (0.57 ± 0.05 MPam0.5 , 0.57 ± 0.08 MPam0.5 and
0.53 ± 0.09 MPam0.5 Molar, respectively).
for Chemfil Rock, Fuji IX GP and Ketac
Conclusions: Although fracture toughness development
has shown to be material-dependent, GI cements are
more prone to fracture before 24 h due to the early stage of
poly-acid/glass reaction kinetics. Since GI restorations are subjected
to normal chewing forces from first hours of placement,
fast fracture toughness development is of clinical relevance to
prevent early fracture. In this sense, Chemfil Rock has shown
to reach a statistically higher KIc at the earliest test period.
This study was supported by Dentsply, Germany.
doi:10.1016/j.dental.2010.08.050
43
Bond strength to enamel and flexural strength of fiberreinforced
composites
M. Beloica 1 , C. Goracci 2 , N. Chieffi 2 , A. Vichi 2 , Z.R.
Vulicevic 1 , M. Ferrari 2
1 University of Belgrade, Serbia
2 University of Siena, Italy
Objectives: To assess shear bond strength to enamel and
flexural strength of reinforcing fibers used in combination
with a flowable resin composite as splinting materials.
Materials and methods: Quartz Splint (RTD, QS), Triaxial
(Ribbond, TX), THM (Ribbond, THM), Construct (Kerr, CNS),
Connect (Kerr, CNN) and everStick PERIO (StickTech, ES) were
tested. QS, CNS, and CNN were impregnated with the proprietary
resin prior to application. Premise Flow (Kerr) was
used in combination. For shear bond strength testing 10 sound
extracted molars per group were selected. On the buccal surface
of each tooth enamel was etched with 37% phosphoric
acid and Optibond FL adhesive (Kerr) was applied. A 1 mmthick
increment of resin composite was layered in a cylindrical
mould and an adequately sized segment of reinforcing fiber
was placed on top. The fiber was then overlaid by another 1mm
thick layer of resin composite. Twenty-four hours after
preparation, the bonded cylinder of fiber-reinforced resin composite
was sheared off using a universal testing machine.
Failure modes were noted. For flexural strength assessment
10 bar-shaped specimens of fiber-reinforced composite per
group were prepared and tested according to ISO Standard
4049/2000. Shear bond strength and flexural strength
of Premise Flow without fiber reinforcement were measured
with the same methods. The ‘No fiber’ group served as control.
Between-group comparisons in shear bond strength,
failure modes distribution and flexural strength were statistically
evaluated (statistical tests: one-way ANOVA, Tukey;
Pearson’s chi-square; Kruskall–Wallis ANOVA, Dunn’s multiple
range, p < 0.05). Scanning electron microscope observations
were taken to visualize the structure of the reinforcing fibers.
Results:
Group Shear bond
strength (MPa)
Flexural strength (MPa)
Mean SD p < 0.05 Mean SD Median 25–75% p < 0.05
QS 15.4 5.2 A 24.9 4.5 13.7 10.6–14.3 A
TX 16.7 6.2 A 19.3 8.6 18.6 12.5–26.7 ABC
THM 18.6 5.6 A 12.4 3 24.7 21.2–25.9 CD
CNS 16 5.5 A 17.5 5.3 13.6 11–18.6 ABC
CNN 14.4 4.1 A 14.3 5.2 19.7 11.6–21.7 BCD
ES 4.6 3.2 B 18.5 2.6 19.3 18.4–19.5 ABC
No fiber 12.8 4.7 A 5.8 1.4 6.3 4.8–6.9 D