ORIGINAL ARTICLE
Effect of surface treatment and type of cement
on the retentive strength of orthodontic
bands on gold alloy crowns
Young-Ah Youn,a Yong-Keun Lee,b Dong-Yul Lee,c Na-Yeon Kim,d and Yong-Kyu Lime
Seoul, Korea
Introduction: The objective of this study was to evaluate the effect of surface treatment of gold alloy
crowns and type of cement on the retentive strength of orthodontic bands cemented on gold alloy
crowns. Methods: Two hundred eight crowns, made of type IV dental gold alloy, were divided into 16 groups
based on surface treatment (C, no treatment; S, sandblasting; V, V-Primer; and S ⫹ V, sandblasting and
V-Primer) and band cement (resin-modified glass ionomer cement, compomer, composite resin, and
adhesive resin cement). Bands were cemented on the crowns, and tensile loads were applied to measure the
retentive strength. Two-way analysis of variance (ANOVA) was performed for the retentive strength with the
factors of surface treatment and type of cement, and the Scheffé multiple comparison test was performed
as a post-hoc test (␣ ⫽ 0.05). Results: The retentive strength of the bands was influenced by surface
treatment and type of cement, and there was significant interaction between the 2 variables based on 2-way
ANOVA (P ⬍.05). Resin-modified glass ionomer cement showed the highest retentive strength regardless of
surface treatment (⬎1.26 MPa). Conclusions: Resin-modified glass ionomer cement is the most desirable
cement for attaching a band to a gold alloy crown. When an adhesive resin cement is used, sandblasting of
the gold crown is recommended. (Am J Orthod Dentofacial Orthop 2007;132:728.e9-728.e14)
A
lthough there have been great improvements in
direct bonding systems, banding on molars is
still popular1 because of the high rate of bond
failure in that area and the use of additional appliances
such as headgear or palatal arch.2 In the oral cavity,
retention of orthodontic bands is influenced by the
morphology and the surface condition of a tooth, and
the bond strength of band cements.3
Recent developments of orthodontic band cements
such as glass ionomer cement (GIC), resin-modified glass
ionomer cement (RMGIC), and polyacid-modified composite resin cement (compomer) were reported.4 Introduced in 1972,5 GIC has been used widely because of
its great retentive ability,6 chemical bonding property
a
Graduate student, Department of Dentistry, College of Medicine, Korea
University, Seoul, Korea.
b
Professor, Department of Dental Biomaterial Science and Dental Research
Institute, College of Dentistry, Seoul National University, Seoul, Korea.
c
Professor, Department of Dentistry, College of Medicine, Korea University,
Seoul, Korea.
d
Graduate student, Department of Orthodontics, College of Dentistry, Yonsei
University, Seoul, Korea.
e
Associate professor, Department of Dentistry, College of Medicine, Korea
University, Seoul, Korea.
Reprint requests to: Yong-Kyu Lim, Department of Dentistry, College of
Medicine, Korea University, 126-1, Anam-Dong, Sungbuk-Ku, Seoul, Korea;
e-mail, yklim@kumc.or.kr.
Submitted, October 2006; revised and accepted, January 2007.
0889-5406/$32.00
Copyright © 2007 by the American Association of Orthodontists.
doi:10.1016/j.ajodo.2007.01.016
to enamel,7,8 and anticaries effect.8,9 However, it has
several shortcomings, such as the need for a precise
powder-to-liquid ratio4,8 and the serious deteriorating
effect of water on setting.4,10
Composed of GIC and resin matrix,11 RMGIC sets
partly via an acid-base reaction and partly by photochemical polymerization.11,12 Therefore, RMGIC provides a
longer working time4,9,13 and higher resistance to water
on setting4,10 than GIC. RMGIC showed greater bond
strength on orthodontic banding than GIC.14 It was
reported, however, that there was no difference between GIC and RMGIC in the bond failure rates of
molar bands in another study.15
Compomer, a mixed material of resin matrix and
silica glass, sets via light-initiated polymerization of the
resin matrix.4,11 Although it releases less fluoride than
RMGIC, it still has an anticaries property.16 Saliva contamination was reported to decrease the bond strength of
compomer when used to cement orthodontic bands.17
In the prosthodontic field, many studies have attempted to improve the bond strength between dental
alloys and resin-based cements.18-24 To improve the bond
strength, various surface treatment methods for alloys
have been introduced,18-24 and several adhesive agents
with functional monomers were also evaluated.24
Restorations could influence the retention of orthodontic appliances when appliances are bonded on their
728.e9
728.e10 Youn et al
Table I.
American Journal of Orthodontics and Dentofacial Orthopedics
December 2007
Cement materials studied
Code
Brand name
Batch number
Manufacturer
FOL
UBL
TBX
SBC
Fuji Ortho LC (RMGIC)
Ultra Band Lok (compomer)
Transbond XT (composite resin)
Superbond C&B (adhesive resin cement)
0402231
0600053
5NA
Monomer, LR1 Catalyst, LS1 Powder, LK1
GC, Tokyo, Japan
Reliance, Itasca, Ill
3M Unitek, Monrovia, Califs
Sun Medical, Moriyama, Japan
surfaces. When orthodontic brackets were bonded on
dental alloys, lower retentive strength was observed compared with that on natural teeth.25,26 Therefore, various
attempts were made to increase the bond strength between
dental alloys and orthodontic brackets.
To increase the bond strength, the gold alloy surface was roughened with a greenstone,25 but it was
ineffective. However, roughening the gold alloy surface
with sandblasting was found to be an efficient method
for improving bond strength.26
Metal primers are specific adhesive monomers used
to increase the bond strength between resin cement and
dental alloys. V-Primer (Sun Medical, Moriyama, Japan) was developed as an interim adhesive agent for
precious metal alloys.27,28 In studies that used metal
primers, it was found that the primer groups had higher
bond strengths between dental alloy and resin cement
than the groups without primers.27-29
Although there have been many studies on the bond
strength between dental gold alloys and resin cements1824,27,28 and the influence of surface treatments of dental
gold alloys and brackets on the bond strength,25,26 few
studies have determined the retentive strength of orthodontic bands cemented on clinically simulated dental
gold alloy crowns. Our aim in this study was to
evaluate the retentive strength of orthodontic bands
cemented on crowns of type IV dental gold alloy after
various surface treatments on crowns with 4 types of
band cements. The null hypothesis was that the surface
treatment and type of cement do not influence the
retentive strength of orthodontic bands cemented on
gold alloy crowns.
MATERIAL AND METHODS
Crowns for maxillary right first molars were made
of type IV dental gold alloy (B20; Heesung Engelhard,
GyeongGi, Korea). The composition of the alloy is
75% gold, 3% palladium, and 18% silver.
Sandblasting of the gold crown surface was carried
out by using a sandblasting machine (Microetcher;
Danville Engineering, San Ramon, Calif) with 50-m
aluminum oxide powder. V-primer, which is specific
for precious alloys, was chosen as an interim adhesive.
Fig 1. Cast gold crown with orthodontic band mounted
on resin block.
Four band cements were studied: an RMGIC (FOL)
(Fuji Ortho LC, GC, Tokyo, Japan), a compomer
(UBL) (Ultra Band Lok; Reliance, Itasca, Ill), a composite resin cement (TBX) (Transbond XT; 3M Unitek,
Monrovia, Calif), and an adhesive resin cement (SBC)
(Superbond C&B; Sun Medical) that is set by autopolymerization (Table I).
Two hundred eight full gold crowns, shaped to fit a
maxillary first molar with several inner hooks, were
fabricated. The hooks were added to enhance the
binding of a gold crown to the resin block used as an
abutment. The inner space of the gold crown was filled
with an orthodontic resin (Ortho-Jet; Lang Dental,
Garden City, NY), and the same resin was used to make
a resin block that was fixed to the grip of a universal
testing machine (4465; Instron, Canton, Mass).
The gold crowns were divided into 4 groups by
surface treatment method: C, no treatment; S, sandblasting; V, V-Primer; and S ⫹ V, sandblasting and V-Primer.
Sandblasting was done at a distance of 1 cm
between the nozzle and the gold crown; 50-m aluminum
oxide powder was sprayed for 3 seconds under pressure of
7 kg per square centimeter. Then the crown surface was
washed and dried. V-Primer was coated once according to
the manufacturer’s instructions.
Orthodontic bands of the same size (UR 17; Tomy,
Tokyo, Japan) were fitted on each crown. Orthodontic
lingual sheaths (601-60; Tomy) were welded on the
buccal and lingual surfaces of the bands (Fig 1) to fix
Youn et al 728.e11
American Journal of Orthodontics and Dentofacial Orthopedics
Volume 132, Number 6
Table II. Comparison of retentive strength according to
cement type and surface treatment
FOL
UBL
TBX
SBC
C
V
S
S⫹V
1.26 (0.20)a/A
0.15 (0.08)a,b/C
0.20 (0.08)a/C
0.49 (0.07)a/B
1.33 (0.30)a/A
0.16 (0.09)a,b/C
0.23 (0.06)a/C
0.89 (0.23)b/B
1.54 (0.21)a/A
0.25 (0.11)b/B
0.24 (0.05)a/B
1.36 (0.26)c/A
1.39 (0.31)a/A
0.14 (0.07)a/B
0.24 (0.07)a/B
1.40 (0.29)c/A
In each row, means with same lower-case letters were not significantly different according to surface treatment method (P ⬎.05).
In each column, means with same capital letters were not significantly different according to type of band cement (P ⬎.05).
Standard deviations are in parentheses.
Table III. Homogenous subsets by surface treatment
regardless of type of band cement based on Scheffé
multiple comparison test
Subset for ␣ ⫽ 0.05
Fig 2. Experimental setup.
the orthodontic ligature wire, which was used to connect to the load cell of the testing machine. Each of the
4 groups sorted by the surface treatment method was
divided into 4 subgroups by the band cements used. In
each subgroup, 13 specimens were tested.
Band cements were mixed according to the manufacturers’ instructions. Bands were seated by using a
band pusher with hand pressure by an operator
(Y-A.Y.) using the same pressure, and excessive cement was removed with a dry gauze swab.
The specimens cemented with RMGIC, compomer,
and composite resin cement were polymerized with a
visible light-curing unit (XL-3000; 3M Unitek, St Paul,
Minn). The light was irradiated at the mesial, distal,
buccal, and lingual sides of the crown for 10 seconds each.
The specimens cemented with SBC were left at room
temperature for 15 seconds for autopolymerization.
After cementation, all specimens were stored in a
37°C water bath for 24 hours and then thermocycled in
a thermocycling machine (KD-TCS 30; Kwangduk,
Seoul, Korea) between 5°C and 55°C for 1000 cycles.
The buccal and lingual sheaths of the band were
connected with orthodontic ligature wires (.012 in;
Ormco, Orange, Calif), and the retentive load of the
Surface treatment
n
1
C
V
S⫹V
S
P
52
52
52
52
0.53
2
3
0.65
1.000
1.000
0.79
0.85
1.000
Means for groups in homogenous subsets are shown.
Based on type III sum of squares.
Error term, mean square (error) ⫽ .033; ␣ ⫽ .05.
band was measured with the testing machine in tensile
mode with a cross-head speed of 1 mm per minute (Fig 2).
Testing proceeded until the band was removed completely from the gold crown. The maximum debonding
force recorded on the force/time curve was converted to
a retentive strength value (MPa) by dividing the maximum force by the band surface.
Statistical analysis
Two-way analysis of variance (ANOVA) was performed for the retentive strength with the variables of
surface treatment and type of cement at the significance
level of 0.05 (version 12.0; SPSS, Chicago, Ill). Means
were compared with the Scheffé multiple comparison test
(␣ ⫽ 0.05).
RESULTS
Values for the retentive strengths of the bands are
listed in Table II. The retentive strength of the bands was
influenced by surface treatment method and type of band
cement, and there was significant interaction between 2
variables based on the 2-way ANOVA (P ⬍.05).
Homogenous subsets for the retentive strength of
the bands by surface treatment regardless of type of
728.e12 Youn et al
American Journal of Orthodontics and Dentofacial Orthopedics
December 2007
Fig 3. Comparison of retentive strength according to
type of band cement in each surface treatment group.
Table IV.
Homogenous subsets by type of cement regardless of surface treatment based on Scheffé multiple
comparison test
Subset for ␣ ⫽ 0.05
Type of cement
n
1
UBL
TBX
SBC
FOL
P
52
52
52
52
0.17
0.23
2
3
1.03
0.503
1.000
1.38
1.000
Means for groups in homogenous subsets are shown.
Based on Type III sum of squares.
Error term, mean square (error) ⫽.033; ␣ ⫽ .05.
cement are listed in Table III. Groups S and S ⫹ V
showed the highest retentive strengths without a significant difference between them; ie, the application of the
V-Primer on the sandblasted gold surface did not
further increase retentive strength. On the other hand,
only the group that used SBC as a band cement with
sandblasting had a significant improvement in the
retentive strength of the band (Table II).
V-Primer showed a significant increase of retentive
strength only in the SBC groups. In the groups that used
UBL as a band cement, V-Primer decreased the effect
of sandblasting. Figure 3 shows the type of cement
groups according to surface treatment with their respective retentive strengths.
Homogenous subsets for the retentive strength of
the bands by type of cement regardless of surface
treatment are listed in Table IV. The RMGIC (FOL)
showed the highest retentive strength, with the adhesive
resin cement (SBC) the next highest. The retentive
strength of each surface treatment group according to
type of band cement is shown in Figure 4.
Fig 4. Comparison of retentive strength according to
various surface treatments in each cement group.
DISCUSSION
There have been many studies on the effect of
dental gold alloy surface treatments on the bond
strength of brackets.25,26,30,31 However, few studies
have evaluated the effects of various surface treatments
of the gold alloy surface on the retentive strength of
orthodontic bands. Therefore, the retentive strength of
orthodontic bands cemented on dental gold alloy
crowns with several band cements and different surface
treatments were evaluated in the present study.
SBC, which has 4-methacryloxy-ethyl-trimellitateanhydride and methyl methacrylate as main components, and tri-n-butylborane as an initiator, polymerizes
to polymethyl methacrylate. It has great bond strength
to teeth, metal, and composite resins, and it also shows
high bond strength to dental gold alloy surfaces by
making an oxide layer on the alloy surface.32,33 In the
present study, SBC had higher retentive strength than
the compomer and the composite resin groups. When
sandblasting was performed, this cement group had the
highest retentive strength along with the FOL group.
Orthodontic bands cemented on extracted human
third molars with the RMGIC (FOL) showed higher
retentive strengths (1.72 MPa) than the compomer
(Transbond Plus, 0.42 MPa).34 But in another study, it
was reported that there were no significant differences
between the RMGIC (FOL, 1.54 MPa) and the compomer (UBL, 1.58 MPa).35 In the present study, all
groups that used FOL as a band cement and the SBC
group treated with sandblasting had retentive strengths
comparable with bands cemented on natural teeth,34,35
but TBX and UBL had lower retentive strengths when
they were used on dental gold alloys. Herion et al36
reported that the shear-peel bond strength of orthodontic bands on porcelain teeth was lower (⬍0.9 MPa) than
the values found on natural teeth regardless of the type
Youn et al 728.e13
American Journal of Orthodontics and Dentofacial Orthopedics
Volume 132, Number 6
of band cement. The shape of the teeth and the surface
characteristics of porcelain were mentioned as possible
causes.
In a study in which molar tubes were bonded on
extracted third molars and debonding was performed in
the occlusal direction, the RMGIC (FOL) showed the
highest bond strength (7.02 MPa), followed by the
compomer (UBL, 4.63 MPa) and composite resin
cement (Transbond, 3.04 MPa).37 These values were
higher than those in the present study (⬍2.0 MPa) and
those of Herion et al.36 However, it was difficult to
compare the bond strength of an orthodontic appliance
directly bonded to the tooth surface and the retentive
strength of orthodontic bands cemented on a dental
alloy crown.
When metal coping was bonded on a tooth, the
RMGIC showed the highest bond strength compared
with composite resin cement, GIC, and zinc phosphate
cement.38 In the present study, the RMGIC and the
adhesive resin cement showed higher bond strengths than
the other 2 cements; therefore, the RMGIC and the
precious metal alloy appeared to have high affinity.
Interim adhesives such as Metal Primer (GC, Tokyo, Japan) or V-Primer have specific adhesive monomers and are used to increase bond strength between
metal alloy and composite resin by simple application
after sandblasting the metal surface. V-primer is used
for precious metal alloys and contains 6-[4-vinylbenzylN-propyl]amino-1,3,5-triazine-2,4-dithione monomer.
The sulfur atom of V-Primer has a specific interaction
with gold.39
Interim adhesives were reported to increase bond
strengths between dental gold alloys and resin adhesives.39-42 V-Primer used with sandblasting was helpful
for increasing bond strength between the dental gold
alloy and the orthodontic bracket.31 But in another
study,27 type IV gold alloy treated with V-Primer did
not show improvement in bond strength when Imperva
Dual (Shofu, Kyoto, Japan) or Panavia 21 (Kuraray,
Kurashiki, Japan) was used as a resin cement, but bond
strength was improved when SBC was used as a
cement. In the present study, the groups treated with
V-Primer showed improved retentive strength only
when SBC was used as a band cement (P ⬍.05).
Therefore, it seems that application of V-Primer is not
always effective with all types of resin cements.
Sandblasting makes irregularities on metal surfaces,
increases the surface area, and mechanically removes
debris on metal surfaces.26,42 The size of the aluminum
oxide particles (110 and 50 m) did not make a great
difference in bond strength of the composite resin, but
the 110-m particles caused more damage on metal
surfaces.42
In the present study, sandblasting increased the
retentive strength of the band (P ⬍.05). However, the
effect of sandblasting was significant only in the group
that used SBC as a band cement (P ⬍.05) based on the
post-hoc test, which compared the retentive strengths of
each cement by the surface treatment. Further study is
recommended to determine why sandblasting was significantly effective only in SBC.
The groups that used SBC as a band cement showed
the greatest improvement in retentive strengths by the
surface treatment of the gold alloy. Among them, the S
and S ⫹ V groups had retentive strengths comparable
to the groups in which FOL was used as band cement.
Therefore, RMGIC is recommended when an orthodontic band is applied to a gold alloy crown, and, in the
case of adhesive resin cement, pretreatment of the
crown surface, such as sandblasting, is needed.
Because only 1 brand of each type of cement was
tested in this study, further studies with new materials
and surface conditioning methods of gold alloy are
recommended. In terms of force application, various
directions of force should be tested as in one’s oral
condition in further studies. Also, the effects of saliva
and solubility of cements could be studied.
CONCLUSIONS
The RMGIC groups showed the highest retentive
strengths of the orthodontic band regardless of surface
treatment. In the adhesive resin cement groups, retentive strength was influenced by the surface treatment
method. Sandblasting tended to increase the retentive
strength in each group with different cements. These
findings suggest that RMGIC is the most desirable
cement when a band is cemented on a gold alloy crown.
When an adhesive resin cement is used, sandblasting of
the crown surface is recommended.
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