Mini-interfacial fracture toughness as a new validated enamel-bonding effectiveness test.
Today׳s most commonly applied bonding effectiveness tests are criticized for their high variability and low reliability, the latter in particular with regard to measuring the actual strength of the adhesive interface.



in continuation of previous research conducted at dentin, we hereby aimed to validate the novel mini-interfacial fracture toughness (mini-iFT) test on its applicability to assess bonding effectiveness of contemporary adhesives when bonded to enamel.



The 3-step etch&rinse (E&R) adhesive OptiBond FL (Kerr), the 2-step self-etch (SE) adhesive Clearfil SE Bond (Kuraray Noritake) and the two multi-mode adhesives Clearfil S(3) Bond Plus (Kuraray Noritake) and Scotchbond Universal (3M ESPE), both used following a 2-step E&R and 1-step SE mode, were applied to clinically relevant, flattened enamel surfaces. A composite (Filtek Z100; 3M ESPE) build-up was made in layers. After 1-week water storage at 37°C, all specimens were sectioned perpendicular to the interface to obtain rectangular sticks. A mini-iFT notch was prepared at the adhesive-enamel interface using a thin diamond blade under water cooling. Finally, the specimens were loaded in a 4-point bending test until failure.



the mini-iFT onto human enamel was significantly higher for the adhesives applied in E&R mode versus those applied in SE mode. The lowest mini-iFT was found for the adhesives applied following a 1-step SE approach. SEM fracture analysis revealed that all fractures originated at the adhesive-enamel interface and that the induced crack propagated preferentially along this interface.



mini-iFT appeared a valid alternative method to assess the mechanical properties of adhesive-enamel interfaces.
KU Leuven (University of Leuven), Department of Oral Health Sciences, BIOMAT & University Hospitals Leuven, Dentistry, Leuven, Belgium; Mahidol University, Department of Operative Dentistry and Endodontics, Bangkok, Thailand.
Pong
P
Pongprueksa
KU Leuven (University of Leuven), Department of Oral Health Sciences, BIOMAT & University Hospitals Leuven, Dentistry, Leuven, Belgium.
Jan
J
De Munck
KU Leuven (University of Leuven), Department of Oral Health Sciences, BIOMAT & University Hospitals Leuven, Dentistry, Leuven, Belgium; KU Leuven (University of Leuven), Department of Mechanical Engineering, Biomechanics Section (BMe), BMGO, Leuven, Belgium.
Bruno C
BC
Barreto
National Science and Technology Development Agency, National Metal and Materials Technology Center (MTEC), Pathumthani, Thailand.
Kavin
K
Karunratanakul
KU Leuven (University of Leuven), Department of Oral Health Sciences, BIOMAT & University Hospitals Leuven, Dentistry, Leuven, Belgium. Electronic address: bart.vanmeerbeek@kuleuven.be.
Bart
B
Van Meerbeek
D003188:Composite Resins; D001840:Dental Bonding; D003743:Dental Enamel; D003799:Dental Stress Analysis; D003804:Dentin; D017220:Dentin-Bonding Agents; D006801:Humans; D008422:Materials Testing; D015203:Reproducibility of Results; D019279:Resin Cements; D013499:Surface Properties; D013718:Tensile Strength
C438313:Clearfil SE Bond; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D019279:Resin Cements; C041330:Scotchbond
Bonding effectiveness; FEA; Mini-iFT; Multi-mode adhesive; Universal adhesive