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3 "Fracture toughness"
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Research Article
Effect of high irradiance and short exposure curing time on the fracture toughness of bulk-fill resin-based composite: an in vitro study
Beatriz Ometto Sahadi, Tainah Oliveira Rifane, Carolina Bosso André, Vitaliano Gomes Araújo-Neto, Richard Thomas Bengt Price, Marcelo Giannini
J Korean Acad Conserv Dent ;Published online April 20, 2026
DOI: https://doi.org/10.5395/rde.2026.51.e23    [Epub ahead of print]
AbstractAbstract PDFPubReaderePub
Objectives
This study aimed to determine the effect of high irradiance and short exposure time on the fracture toughness of bulk-fill resin-based composites (RBCs).
Methods
Three RBCs were tested: Tetric PowerFill (TPF; Ivoclar Vivadent), Opus Bulk Fill APS (OBF; FGM Dental Group), and Filtek One Bulk Fill (FOB; Solventum). Sixty single-edge-notched disc specimens were prepared using a fracture toughness mold. Each group consisted of 20 samples, divided into two subgroups (n = 10). The RBCs were lightcured either for 3 seconds in high-irradiance mode (‘3s cure’) or for the manufacturer-recommended times (TPF, 10 seconds; OBF, 30 seconds; FOB, 20 seconds) in ‘high power’ mode using the Bluephase PowerCure (Ivoclar Vivadent). The peak spectral wavelength was measured using a spectrophotometer. Specimens were tested on a universal testing machine, and data were analyzed by two-way analysis of variance and Bonferroni test (α = 0.05).
Results
Radiant exposure values (J/cm²) were 9.5 for the 3-second mode and 12.4, 24.8, and 37.1 for 10, 20, and 30 seconds (high power mode), respectively. FOB (4.22 and 3.79 MPa∙m0.5 for 20 and 3 seconds) had the highest mean fracture toughness, while OBF showed the lowest (2.01 and 2.10 MPa∙m0.5 for 30 and 3 seconds). TPF produced intermediate results (2.72 and 2.70 MPa∙m0.5 for 10 and 3 seconds). Exposure time did not affect TPF and OBF, while the 3-second exposure significantly reduced the fracture toughness for FOB.
Conclusions
The RBCs tested had different fracture toughness values regardless of exposure time. High irradiance and short exposure can reduce fracture toughness depending on the RBC tested.
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Basic Research
The study of fractural behavior of repaired composite
Sang-Soon Park, Wook Nam, Ah-Hyang Eom, Duck-Su Kim, Gi-Woon Choi, Kyoung-Kyu Choi
J Korean Acad Conserv Dent 2010;35(6):461-472.   Published online November 30, 2010
DOI: https://doi.org/10.5395/JKACD.2010.35.6.461
AbstractAbstract PDFPubReaderePub
Objectives

This study evaluated microtensile bond strength (µTBS) and short-rod fracture toughness to explain fractural behavior of repaired composite restorations according to different surface treatments.

 Materials and Methods

Thirty composite blocks for µTBS test and sixty short-rod specimens for fracture toughness test were fabricated and were allocated to 3 groups according to the combination of surface treatment (none-treated, sand blasting, bur roughening). Each group was repaired immediately and 2 weeks later. Twenty-four hours later from repair, µTBS and fracture toughness test were conducted. Mean values analyzed with two-way ANOVA / Tukey's B test (α = 0.05) and correlation analysis was done between µTBS and fracture toughness. FE-SEM was employed on fractured surface to examine the crack propagation.

 Results

The fresh composite resin showed higher µTBS than the aged composite resin (p < 0.001). Mechanically treated groups showed higher bond strength than non-mechanically treated groups except none-treated fresh group in µTBS (p < 0.05). The fracture toughness value of mechanically treated surface was higher than that of non-mechanically treated surface (p < 0.05). There was no correlation between fracture toughness and microtensile bond strength values. Specimens having high KIC showed toughening mechanism including crack deviation, microcracks and crack bridging in FE-SEM.

 Conclusions

Surface treatment by mechanical interlock is more important for effective composite repair, and the fracture toughness test could be used as an appropriate tool to examine the fractural behavior of the repaired composite with microtensile bond strength.

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Original Article
A study on fractural behavior of dentin-resin interface
Gil-Joo Ryu, Gi-Woon Choi, Sang-Jin Park, Kyung-Kyu Choi
J Korean Acad Conserv Dent 2007;32(3):208-221.   Published online May 31, 2007
DOI: https://doi.org/10.5395/JKACD.2007.32.3.208
AbstractAbstract PDFPubReaderePub

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.

Citations

Citations to this article as recorded by  
  • The study of fractural behavior of repaired composite
    Sang-Soon Park, Wook Nam, Ah-Hyang Eom, Duck-Su Kim, Gi-Woon Choi, Kyoung-Kyu Choi
    Journal of Korean Academy of Conservative Dentistry.2010; 35(6): 461.     CrossRef
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