BONDING ORTHODONTIC RESIN CEMENT TO ZIRCONIUM OXIDE UNDER
ORTHODONTICS LOAD AND THERMOCYCLING EFFECT
bonding.
The specimens (N = 60), were randomly divided in two
subgroups. Half of the specimens with orthodontic load
(n = 30) and the other half without orthodontic load (n
= 30). The orthodontic load and the non-orthodontic
load specimens were further randomly divided into two
subgroups: thermo cycling (TC) group and non-thermo
cycling (non-TC) group (n = 15 per group) (Fig. 1).
2.2. Surface Conditioning Methods
All the specimen’s surfaces were conditioned using
air abrasion with an intraoral air-abrasion device
(Microetcher, Danville Engineering, San Ramon, CA,
USA) with 30 μm silica-coated Al 2 O 3 (CoJet Sand, 3M
ESPE, St Paul, MN, USA), perpendicular to the surface
from approximately 10 mm for 20 s in circling motions
at 2.8 bar. After air abrasion, the specimen surfaces
were air blown to remove the remnants of the powder.
2.3. Bonding Procedures
Specimen surfaces were coated with a thin layer of
Universal Primer (Monobond Plus, Ivoclar Vivadent) that
was left for 60 seconds to allow it to react, and then the
remaining excess was removed with a strong stream of
air. Each specimen was fixed to a bonding clamp with
a special mold (Ultradent Shear Bond Test, Ultradent
Products, Inc., South Jordan, UT, USA) to assure flat
substrate surfaces and to standardize the diameter (2.3
mm) of the resin composite. Orthodontic resin (Heliosit
Orthodontic, Ivoclar Vivadent) was applied to the surface
using the bonding mold. Composite was applied in the
mold and light cured (SmartLite Max, Dentsply Sirona,
York, PA, USA, 1400 mW/cm 2 , 40 s) (Fig. 2). All specimens
were stored in distilled water at 37 ± 1°C.
As next step, orthodontic brackets were bonded to
the acrylic next to the embedded specimens of the
load groups. The position was selected to apply a
force of approximately 70 ± 15 g (0.69 ± 0.14 N) with
an orthodontic wire (SS 0.14) (Fig. 3) to the bonded
composite cylinders. The force was measured by using a
Dontrix gauge (TP Orthodontics, Inc., La Porte, IN, USA).
The orthodontic load group and the non-orthodontic
load group were further randomly divided into two
subgroups (n = 15): the thermo cycling (TC) group and
the non-TC group (Fig. 1). Before testing the microshear
bond strength all the specimens of the TC group were
thermocycled in a Chewing Simulator device (CS-4SD
Mechatronic GmbH, Feldkirchen, Westerham, Germany)
for 5000 cycles between 5°C and 55°C with a dwell time of
30 seconds with the mechanical load component of the
machine turned off. At the same time, all the specimens
of the non-TC group were stored in distilled water at 37
± 1°C. The position of the brackets to be bonded to the
resin block is marked on both sides of the composite/MZ
sample. The specimens were subjected to µSBS test using
an universal machine (Instron 1125, Norwood, MA, USA,
Fig. 4) (crosshead speed 0.5 mm/min).
2.4. Statistical Analysis
Means and standard deviations of the shear bond
strength were calculated for all groups [9]. Microshear
bond strength data (MPa) were submitted to a two-
way ANOVA (SAS 9.4). Multiple comparisons were made
using the Tukey´s Studentized Range (HSD) Test (α =
104
Figure 1. Experimental sequence, MZ= Monolithic Zirconium oxide ce-
ramic, TC= Thermocycling effect.
Figure 2. The Pencil line is tangent to the composite cylinder and it is 0.5
mm higher than the position of the bracket on the both side of MZ, in order
to provide 70 ± 15 g (0.69 ± 0.14 N) load force by the orthodontic wire.
Figure 3. Top view showing the final design after adding orthodontic
wire to composite cylinder.
0.05) for shear used to determine significant differences
between the group dependent on the variable with
and without application of load and/or TC.
3. Results
Two-way ANOVA for µSBS values (MPa) showed highly
significant (p = 0.0004) effects, however highly signifi-
cant load/thermocycling interactions were found (Tab.
Stoma Edu J. 2018;5(2): 102-108 http://www.stomaeduj.com