Optimizing filler content in an adhesive system containing pre-reacted glass-ionomer fillers.
OBJECTIVE
(1) To evaluate the optimal concentration of the calcium type pre-reacted glass-ionomer (PRG-Ca) fillers in experimental light-activated adhesives for bonding to tooth substrates and fluoride release; (2) to evaluate the polymerization reactivity of these experimental filled adhesives; and (3) to examine the ultrastructure of the resin-dentin interface bonded with the commercial version of this self-etching adhesive (Imperva Fluoro Bond, Shofu Inc., Kyoto, Japan).


METHODS
PRG-Ca fillers were prepared from the acid-base reaction of calcium type fluoroaluminosilicate glass with poly(acrylic acid) in water. Different experimental light-cured adhesives were prepared, with 0-57wt% PRG-Ca fillers and 3wt% aerosil silica incorporated in a resin matrix. Twenty-four hours shear bond strengths to bovine enamel and dentin were assessed using the adhesive with/or without accelerated aging. The cumulative amount of fluoride released from the cured adhesives and differential scanning calorimetry (DSC) measurements were also conducted. 180-grit SiC paper polished human dentin disks were treated with Imperva Fluoro Bond that contains 17wt% PRG-Ca fillers and prepared for TEM examination.


RESULTS
Increase in PRG-Ca filler content of experimental adhesives was highly correlated with the decrease in bond strengths to dentin (r=-0.96 to -0.99), the increase in cumulative fluoride release, (r=0.97) and the decrease in polymerization energy (cal/g) of the adhesives (r=-0.99) (p<0.001). A PRG-Ca content of 17wt% provided optimal bond strength to enamel and dentin after accelerated aging and fluoride release. TEM showed that salt-like matrices were present around the hydrogels and remnant glass cores of the PRG-Ca fillers. The commercial self-etching primer completely dissolved the smear layer and formed 2 micrometer thick hybrid layers in intact dentin.


CONCLUSIONS
The use of silanized PRG-Ca fillers provides good adhesion and a source of fluoride release in a commercially available self-etching adhesive system.
Ikemura
K
K
Department of Research and Development, Shofu Inc., 11, Kamitakamatsu-cho, Fukuine, Higashiyama-ku, 605, Kyoto, Japan. kfctay@netvigator.com
Tay
F R
FR
Kouro
Y
Y
Endo
T
T
Yoshiyama
M
M
Miyai
K
K
Pashley
D H
DH
D000704:Analysis of Variance; D000818:Animals; D002152:Calorimetry, Differential Scanning; D002417:Cattle; D003188:Composite Resins; D001840:Dental Bonding; D003738:Dental Cements / Q000737:chemistry*; D003804:Dentin / Q000648:ultrastructure; D003806:Dentin Permeability; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D005459:Fluorides / Q000737:chemistry; D005460:Fluorides, Topical / Q000737:chemistry*; D005899:Glass Ionomer Cements / Q000737:chemistry*; D016014:Linear Models; D008422:Materials Testing; D008854:Microscopy, Electron; D011108:Polymers / Q000737:chemistry; D033081:Shear Strength
D003188:Composite Resins; D003738:Dental Cements; D017220:Dentin-Bonding Agents; D005460:Fluorides, Topical; C072652:FluoroBond; D005899:Glass Ionomer Cements; D011108:Polymers; D005459:Fluorides