Effect of air-drying and solvent evaporation on the strength of HEMA-rich versus HEMA-free one-step adhesives.
OBJECTIVE
The objectives of this study were (1) to clarify the relationship between the duration of air-drying of one-step self-etch adhesives (1-SEAs) and the evaporation degree (ED) of solvents, and (2) to evaluate the effect of ED on the ultimate micro-tensile strength (microTS) of the adhesives.


METHODS
The ED of one HEMA-rich 1-SEA, Clearfil S3 Bond (Kuraray), and two HEMA-free 1-SEAs, iBond (Heraeus-Kulzer) and G-Bond (GC), was determined without air-drying and after, respectively, 5- and 10-s air-drying using a gravimetric method. Next, the microTS of the adhesives at ED equivalent to 0-, 5- and 10-s air-drying was measured.


RESULTS
The ED increased with extension of air-drying time. Among the adhesives tested, iBond showed the largest ED, followed by G-Bond and Clearfil S3 Bond in this order. A longer air-drying time for 10-s resulted in a statistically significantly higher microTS for the HEMA-rich Clearfil S3 Bond. The microTS of the latter was higher than that of the other two HEMA-free adhesives for each air-drying time.


CONCLUSIONS
Air-drying of 1-SEAs had a significant effect on the degree of solvent evaporation (ED) and also on the mechanical properties (microTS) of the 1-SEAs upon setting. It is therefore beneficial to remove solvents of the 1-SEAs as much as possible by thorough, strong air-drying in order to achieve a strong adhesive layer at the interface.
Ikeda
Takatsumi
T
Department of Restorative Dentistry, Division of Oral Health Science, Hokkaido University, Graduate School of Dental Medicine, Kita 13 Nishi 7, Kita-ku, Sapporo 060-8586, Japan.
De Munck
Jan
J
Shirai
Kenichi
K
Hikita
Kazuhiro
K
Inoue
Satoshi
S
Sano
Hidehiko
H
Lambrechts
Paul
P
Van Meerbeek
Bart
B
D000096:Acetone / Q000737:chemistry; D000388:Air; D000465:Algorithms; D001840:Dental Bonding; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D003890:Desiccation; D000431:Ethanol / Q000737:chemistry; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry*; D019279:Resin Cements / Q000737:chemistry; D012997:Solvents / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D013997:Time Factors
C505694:Clearfil S3 Bond; D017220:Dentin-Bonding Agents; C498353:G-Bond; D008689:Methacrylates; D019279:Resin Cements; D012997:Solvents; C477386:iBond; D000096:Acetone; D000431:Ethanol; C005044:hydroxyethyl methacrylate