MSDS
Technique
Data
0027
Bonding
of Some Self-etch Adhesives to Unground Enamel
F.R. TAY1, D.H. PASHLEY2, N.M. KING1, J. TSAI1, C.N.S. LAI1, R.M. CARVALHO3,
and L. MARQUEZINI, Jr.3, 1 The University of Hong Kong, China, 2 Medical
College of Georgia, Augusta, USA, 3 University of São Paulo,
Bauru, Brazil
Objectives: Manufacturers of mild self-etch adhesives such as
Clearfil SE Bond (SE: Kuraray) recommend adjunctive phosphoric acid-etching
when bonding to unground enamel. Some of the recently introduced self-etch
adhesives are more acidic in nature and are claimed to bond well to
both enamel and dentin. This study examined the ultrastructure and microtensile
bond strengths (mTBS) of two of these more aggressive versions, Xeno
III (XE: Dentsply), a 1-step self-etch adhesive, and Simplicity (JK:
Apex Dental Materials), a 2-step self-etch adhesive to unground enamel.
SE was used as the negative control, and One-Step (OS: Bisco), a total-etch
adhesive bonded to 32% phosphoric acid-etched unground enamel was used
as the positive control. Methods: The adhesives were applied
to unground enamel on the mesial and distal surfaces of extracted human
molars, coupled with light-cured composites, and then thermocycled between
5-55°C for 1000X. For TEM, bonded specimens were sectioned without
resin-embedding, producing separation of the enamel hybrid layer from
the underlying unbonded enamel by a stiffness-toughness mismatch. For
bond testing, composite-enamel beams (N=24) were sectioned and tested
with a universal testing machine at a crosshead speed of 1 mm/min.
Results: Enamel hybrid layer thickness (mm): OS (9.6±1.3)A,
JK (3.3± 0.5)A,B, XE (1.0±0.2)B,C, SE (0.3±0.1)C
[P<0.05]. Dissolution of enamel crystallites on the surface of enamel
hybrid layers varied from being barely dissolved (SE) to superficial
dissolution (XE; JK) to internal dissolution with central hole regions
(JK; OS). mTBS results showed that OS, JK and XE were not significantly
different from each other, but were all significantly higher than SE
[P<0.001]. There was no correlation between hybrid layer thickness
and mTBS. Conclusion: The more aggressive self-etch adhesives exhibit
similar bond strength as a total-etch adhesive to unground enamel, making
them potentially useful as pit-and-fissure sealants and bonding of orthodontic
brackets.
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