Published online May 31, 2007.
https://doi.org/10.5395/JKACD.2007.32.3.208
A study on fractural behavior of dentin-resin interface
Abstract
The fracture toughness test is believed as a clinically relevant method for assessing the fracture resistance of the dentinal restoratives. The objectives of this study were to measure the fracture toughness (K1C) and microtensile bond strength of dentin-resin composite interface and compare their relationship for their use in evaluation of the integrity of the dentin-resin bond.
A minimum of six short-rod specimens for fracture toughness test and fifteen specimens for microtensile bond strength test was fabricated for each group of materials used. After all specimens storing for 24 hours in distilled water at 37℃, they were tensile-loaded with an EZ tester universal testing machin. Statistical analysis was performed using ANOVA and Tukey's test at the 95% confidence level, Pearson's coefficient was used to verify the correlation between the mean of fracture toughness and microtensile bond strength. FE-SEM was employed on fractured surface to describe the crack propagation.
Fracture toughness value of Clearfil SE Bond (SE) was the highest, followed by Adper Single Bond 2 (SB), OptiBond Solo (OB), ONE-STEP PLUS (OS), ScotchBond Multi-purpose (SM) and there was significant difference between SE and other 4 groups (p < 0.05). There were, however, no significant difference among SB, OB, OS, SM (p > 0.05). Microtensile bond strength of SE was the highest, followed by SB, OB, SM, OS and OS only showed significant lower value (p < 0.05). There was no correlation between fracture toughness and microtensile bond strength values. FE-SEM examination revealed that dentin bonding agent showed different film thickness and different failure pattern according to the film thickness.
From the limited results of this study, it was noted that there was statistically no correlation between K1C and µTBS. We can conclude that for obtaining the reliability of bond strength test of dentin bonding agent, we must pay more attention to the test procedure and its profound scrutiny.
Figure 1
Schematic geography of fracture toughness specimen.
Figure 2
Each component of the mold.
Figure 3
Assembled mold.
Figure 4
K1C value of experimental groups.
Figure 5
µTBS value of experimental groups.
Figure 6
It showed that bevel formed by spacer and crack occurred along the bevel. C: Composite resin, CAD: Composite adhered to dentin
The resin surface of fractured K1C specimen of SM group (× 50).
Figure 7
The arrows showed that crack formed along the bevel move into the adhesive surface (see the black arrows).
The resin surface of fractured K1C specimen of OB group (× 500).
Figure 8
It revealed that the failure occurred between resin-infiltrated layer and adhesive layer. At the tip of the bonded surface(white arrow), failure occurred mainly within the adhesive resin layer. D: dentin, AR: Adhesive resin layer
The dentin surface of fractured K1C specimen of SB group (× 250).
Figure 9
The thickness of adhesive layer was 40 ~ 55 µm and dentinal tubules were running oblique direction. The adhesive layer was relatively thick and uniform.
The cross-sectional SEM photograph of bonded surface of SM group (× 1,000).
Figure 10
The thickness of adhesive layer was 14 ~ 25 µm and the dentinal tubules were filled with resin tags. Some of the dentinal tubules were empty, some of the resin tags had many branches. RT: Resin tag, ID: Intertubular dentin, PD: Peritubular dentin
The cross-sectional SEM photograph of bonded surface of SB group (× 3,000).
Figure 11
The thickness of adhesive layer was 50 ~ 60 µm and it was the thickest adhesive resin layer among the experimental groups. Most of dentinal tubules were filled with resin tags.
The cross-sectional SEM photograph of bonded surface of SE group (× 1,000).
Figure 12
Bond failure occurred predominantly between the resin-infiltrated layer and adhesive resin. The orifices of dentinal tubules were not seen clearly and irregular adhesive resin layer was showed at the dentin surface of fractured specimen.
The resin surface (left) and dentin surface (right) of fractured SM group (× 2,000).
Figure 13
Many broken resin tags were seen on the both specimens, the fracture of the resin tags mainly occurred at the upper part of the resin-infiltrated layer. RT: resin tag, DT: dentinal tubule
The resin surface (left) and dentin surface (right) of fractured OS group (× 2,000).
Figure 14
On the resin surface, many resin tags and adhesive resin layer was seen partially. The dentin surface of the fractured specimen showed relatively smooth appearance and many dentinal tubules filled with resin tags. The fracture of resin tags were occurred at the orifices of the dentinal tubules. AR: adhesive resin layer, RT: resin tag
The resin surface (left) and dentin surface (right) of fractured OB group (× 2,000).
Figure 15
Relatively short broken resin tags were seen on the resin side. Irregular adhesive resin layer and dentinal tubules obstructed with resin tag or covered with adhesive resin were seen on the dentin side of the fractured specimen.
The resin surface (left) and dentin surface (right) of fractured SB group (× 2,000).
Figure 16
Resin tags and dentinal tubules were seen rarely. Both sides showed very irregular appearance and bond failure occurred predominantly within the adhesive resin layer.
The resin surface (left) and dentin surface (right) of fractured SE group (× 2,000).
Table 1
Dentin bonding agents (DBA) used in this study and their compositions
Table 2
Instructions for use of dentin bonding agents(DBA)
Table 3
Fracture toughness(Mean ± S.D., MPa·m1/2) of 5 experimental groups
Table 4
Microtensile bond strength(Mean ± S.D., MPa) of 5 experimental groups
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