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Dentin Bond Strength of NX3 Resin Cement
X.J. Qian*, H. Bui, D. Tobia, Kerr Corporation, Orange, California, USA
INTRODUCTION
Dual-cure resin cement has been the material of choice for cementing
Extracted human teeth were embedded in cold-cure acrylics. A set of six specimens were prepared for each group.
various indirect restorations because it possesses many desirable
A low speed diamond saw was used to remove the crown and expose the occlusal dentin. The dentin substrates
Cement (self-cured) Adhesive/Primer System
Dentin SBS, MPa
properties such as excellent mechanical strength, high fracture toughness,
were polished with 240-grit and then 600-grit SiC paper. If a total-etch adhesive is used, then the dentin substrates
NX3
OptiBond Solo Plus
33.2±3.2a*
choice of curing mechanisms, and most importantly esthetic properties
were etched with 37% H3PO4 gel etchant (Kerr) for 15 seconds, rinsed thoroughly with water, and air dried for a few
(good translucency). However, most dual-cure resin cements use BPO
seconds. Each adhesive (or mixed adhesive/activator if an activator is recommended) was then applied to the
NX3
OptiBond All-In-One
32.6±5.5a
(benzoyl peroxide)/tertiary amine pair as their redox initiator system and
dentin surface according to the manufacturer’s instructions, air dried, and light-cured if indicated. The adhesive
Nexus 2
OptiBond Solo Plus+Activator
22.6±1.3b
suffers two serious drawbacks as a result: (1) significant long-term
covered substrate was then held securely by a bonding jig (Ultradent Inc.) with a cylindrical mold (Φ = 2.38 mm).
discoloration, making them unsuitable for cementing esthetic
The mold was then filled with each adhesive’s respective cement, and the cement was self-cured. The whole
RelyX ARC
Single Bond Plus
19.9±1.8b
porcelain/ceramic restorations; and (2) bond incompatibility with more
bonding assembly was conditioned at 37ºC in a high humidity chamber (85-90% relative humidity) to allow the
Calibra
Prime&Bond NT+Activator
17.8±2.1b,c
acidic single-bottle adhesives such as the 5th & 7th generation adhesives.
cement to self-cure for one hour before the bonding jig was removed. The prepared specimens were then stored in
de-ionized water at 37ºC for 24 hours before being subjected to debonding under shear force.
Multilink
Primers A+B
17.8±5.3b,c
The bond incompatibility between resin cement and more acidic single-
bottle adhesive is encountered when cementing metal-based or rather
Variolink
Excite DSC(+Activated brush)
12.0±6.6c
The specimens in each group were tested on an Instron mechanical tester (Model 4467, Instron Corporation) in
opaque restorations where there is limited or no light accessibility and the
shear mode using a notched (semi-circular) edge at a crosshead speed of 1.0 mm/min. Shear bond strength values
Panavia F2.0
ED Primers A+B
11.2±1.9c
cement has to be self-cured. This bond incompatibility could be attributed
in MPa were calculated by dividing the peak load by the bonding area.
to the inability of the BPO/Amine redox initiator system used in current
*Means with different letters are statistically different at p < 0.05.
resin cements to initiate polymerization in the dark and in the presence of
Statistical analysis was performed using One-way ANOVA and Bonferroni’s method for pair-wise comparison to
quite acidic monomers within the air-inhibited layer of light-cured
determine significant differences among groups (p<0.05).
adhesives as a result of an acid-based reaction. To minimize this
incompatibility problem, some manufacturers provided a separate Activator
that needs to be mixed with the single-bottle adhesive for enhanced dark-
cure efficiency. Although effective, the activator introduces complexity
Dentin Shear Bond Strength of Various Cements
into the bonding process in that there is an additional component and an
extra mixing step involved.
DISCUSSION
Panavia F2.0 + ED Primers A & B
Recently, a new dual-cure resin cement NX3 was introduced that employs a
The relative ranks of SBS for all cements in combination with
novel amine-free redox initiator system for improved bond compatibility and
their respective adhesives are as follow: NX3 (w/ OptiBond Solo
Variolink II + Excite DSC + Activated Brush
long-term color stability. NX3 can be used with both total-etch and self-etch
Plus) ≥ NX3 (w/ OptiBond All-In-One) > Nexus 2 ≥ RelyX ARC ≥
Multilink + Primers A & B
adhesives. It also simplifies cementation procedures by eliminating the self-
Calibra ≥ Multilink ≥ Variolink ≥ Panavia F2.0
cured activator for the single-bottle adhesive so that no mixing is required
Calibra + Prime&Bond NT + Activator
for the adhesive regardless of whether it is a total-etch or self-etch
ANOVA analysis revealed that, the dentin SBSs of NX3/OptiBond
RelyX ARC + Single Bond Plus
adhesive.
Solo Plus and NX3/OptiBond All-In-One are not statistically
(P>0.05) different from each other, but both are significantly
Nexus 2 + OptiBond Solo Plus + Activator
(p<0.05) higher than those of all other cements. This clearly
demonstrates NX3’s superior bond compatibility with both total-
NX3 + OptiBond All-In-One
etch and self-etch adhesives. This enhanced bond compatibility
NX3 + OptiBond Solo Plus
OBJECTIVE
Figure 1: Bonding Jig
for NX3 could be attributed to its proprietary amine-free redox
To test and compare the dentin shear bond strength (SBS) of NX3 in
system that is quite resistant to acidic monomers within the air-
combination with either a total-etch adhesive OptiBond Solo Plus (Kerr) or
inhibited layer of the light-cured adhesive. What is even more
noteworthy is the fact that the enhanced bond compatibility of
Shear Bond Strength, MPa
a self-etch adhesive OptiBond All-In-One (Kerr) without an activator, along
NX3 with both total-etch and self-etch adhesives is achieved
with several commercial resin cements in combination with their respective
without using an activator for the adhesives. As a direct
primers/adhesives/activator.
comparison, using the same OptiBond Solo Plus adhesive
system, NX3 (omitting the Activator for the adhesive) yielded
significantly (p<0.05) higher dentin SBS than Nexus 2 (using the
Activator for the adhesive). Without the need for an activator, NX3
MATERIALS
CONCLUSIONS
resin cement offers a much simplified cementation procedure
NX3/OptiBond Solo Plus (without activator) Kerr
with less component and less step (no mixing is required for the
NX3 dual-cure resin cement exhibited excellent bond compatibility with both total-etch and
NX3/OptiBond All-In-One (without activator)
adhesive). The mixing of an adhesive with an activator is
self-etch adhesives, and produced the highest dentin SBS among all cements/adhesive
Calibra/Prime&Bond NT (with Activator)
Denstply
required for most other cements included in this study. For
systems in this study. The superior bond compatibility between NX3 and adhesive is
Multilink/(Primers A + B)
some cements, severe bond incompatibility is encountered if the
achieved even without the need for an activator, resulting in a much simplified cementation
Nexus 2/OptiBond Solo Plus (with Activator)
activator for the adhesive is omitted. As an example, when the
procedure as no mixing is needed for the adhesive. NX3’s enhanced compatibility with both
Panavia F2.0/(ED Primers A + B)
Figure 2: Shear Bond Test Set-Up
activator was omitted for Calibra/Prime&Bond NT system, a
total-etch and self-etch single-bottle adhesive could be attributed to its proprietary amine-free
RelyX ARC/Single Bond
dentin SBS of 0 MPa (i.e. automatic debonding) was obtained,
redox initiator system.
Variolink II/Excite DSC (with Activated brush)
versus 17.8 MPa when the activator was used.

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