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TABLE 1: UNIVERSAL ADHESIVES
Universal adhesive
|
Manufacturer
|
Base
|
pH
|
VLC
|
Dual cure activator
|
Act as silane
Scotchbond Universal Adhesive
| 3M ESPE
| Water
| 2.7 | Yes, pre-cure | Yes *
| Zirconia, glass ceramics, metals
Adhese Universal
| Ivoclar
| Water
| 2.5 | Yes, pre-cure | None required
| No
All-Bond Universal
| Bisco
| Water, ethanol | 3.2 | Yes, pre-cure | None required
| Zirconia, glass ceramics
Clearfil Universal Bond
| Kurary
| Water
| 2.3 | Yes, pre-cure | Yes
| Zirconia, glass ceramics
Futurabond U
| VOCO
| Water
| 2.3 | Yes, pre-cure | None required
| Zirconia, glass ceramics, metals
Optibond XTR (2-bottle system) | Kerr
| Water
| 3.4 | Yes, pre-cure ** | None required
| Zirconia, glass ceramics, metals
Prime & Bond Elect
| Dentsply Caulk | Acetone
| 2.5 | Pre-cure
| Yes
| Glass ceramics, metals
* Not for 3M ESPE products | ** Optional with NX3
bonding with hydroxyapatite, with the added feature of being able
to create a chemical bond to metals and zirconia. Other phosphate
esters, such as PENTA-P and GPDM, also are primary functional
monomers in universal adhesives.
Although in vitro adhesive bonding studies are generally
performed on fresh dentin fromnon-erupted, extracted teeth, clini-
cally it is very common to bond to sclerotic dentin. Sclerotic dentin
is a more highly mineralized, complex substrate with reduced
numbers and size of dentinal tubules that decrease bond strength.
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Weaker acids in self-etching adhesives have a much greater diffi-
culty creating effective bonds to sclerotic dentinwithout a chemical
bond. Universal adhesives may be preferred on sclerotic dentin
since they tend to contain additional functional monomers for
chemical bonding as well as being compatible with total etching.
An innovative development for several of the universal adhe-
sives is the option to use it as a silane coupler for chemical bonding
to glass ceramics. This would be a very convenient application, as
it would permit the use of one material as both tooth adhesive and
silane coupler. Some in vitro studies have questioned whether the
silane monomer may be unstable in the acidic environment of the
adhesive or combined with other monomers.
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The conservative
clinician would be well served to use a dedicated silane coupler on
glass ceramics until clinical evidence for the use of these universal
adhesives as silane couplers is available.
Universal adhesives are indicated for both direct composite
restorations and cementation of bonded indirect restorations.
This leads to the recent discussion of whether the adhesive needs
to be cured on the tooth prior to placement of the resin cement
(pre-cured) or simultaneously with the resin cement. Maximum
light energy is delivered to the adhesive when it is directly
exposed to the curing light, advocating for the pre-cure technique
for maximum sealing and bond strength. However, the adhesive
does have a film thickness with the perceived risk of incomplete
seating of the restoration if the adhesive is pre-cured.
This is the reason many clinicians tend to cure simultaneously
with the resin cement in spite of the manufacturers' instruc-
tions and recommendation. And this risk was very real for 3rd
and 4th generation adhesives. One in vitro study compared 3rd
generation adhesives with a self-etching primer (A.R.T. Bond and
Syntac), a 4th generation adhesive with total etching (Scotch-
bond Multi-Purpose Plus), and 5th generation one-bottle adhe-
sives (Syntac Single Component and Prime & Bond 2.1) used with
