Water sorption/solubility of self-etching dentin bonding agents.
OBJECTIVE
The purpose of this study was to compare the water sorption/solubility, percent conversion and microtensile bond strength of three single-step self-etching adhesives with those of a two-step self-etching primer adhesive system.


METHODS
Solvent evaporation from the adhesives was determined gravimetrically. After removal of volatile solvents, the resins were cast into disks and polymerized. One-half of the disks were incubated in water while the other half were incubated in hexadecane. Repeated measurements of water sorption were made for 10 days followed by drying for 2.5 days to a constant weight. Percent conversion was done using FTIR spectroscopy. Microtensile bond strengths were measured 24h after bonding.


RESULTS
All of the adhesives lost 20-30% of their weight after 4 min of forced air except for Fluorobond II which lost no weight. All resins stored in water exhibited a time-dependent increase in water sorption and solubility. The resins stored in hexadecane showed very low sorption and solubility. Water sorption was highest for Absolute 2 (20.7%), intermediate for Fluorobond Shake One (10.2%) and lowest for Clearfil (3)S (8.9%) and Fluorobond II (7.5%). Percent conversions ranged from a low of 68.3% for Absolute 2 to a high of 87.4% for Clearfil (3)S. The two-step self-etching primer adhesive (Fluorobond II) gave the lowest water sorption and lowest solubility of any of the tested adhesives. SEM observations of resin disks incubated in hexadecane looked similar to unincubated controls. Incubating resin disks in artificial saliva covered the surfaces of the resins with mineral crystallites.


CONCLUSIONS
Single bottle self-etching adhesives show higher water sorption/solubilities than two-step self-etching adhesives. The former products would not be expected to function as well as the latter products.
Ito
Shuichi
S
Health Sciences University of Hokkaido, Division of Cariology and Endodontology, Department of Oral Rehabilitation, School of Dentistry, 1757 Tobetsu, Hokkaido 0610293, Japan. shu@hoku-iryo-u.ac.jp
Hoshino
Tomohiro
T
Iijima
Masahiro
M
Tsukamoto
Naohiro
N
Pashley
David H
DH
Saito
Takashi
T
D000042:Absorption; D000134:Acid Etching, Dental / Q000379:methods; D000473:Alkanes / Q000737:chemistry; D001840:Dental Bonding; D003799:Dental Stress Analysis; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D006244:Hardness; D008422:Materials Testing; D044367:Phase Transition; D019279:Resin Cements / Q000737:chemistry*; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared; D013718:Tensile Strength; D014835:Volatilization; D014867:Water; D017155:Wettability
D000473:Alkanes; D017220:Dentin-Bonding Agents; D019279:Resin Cements; D014867:Water; C007932:n-hexadecane