Download Enamel fluoride levels after orthodontic band cementation with glass

European Journal of Orthodontics 18 (1996) 81-87
O 1996 European Orthodontic Society
Enamel fluoride levels after orthodontic band cementation
with glass ionomer cement
Sevil Akkaya*, Oktay Oner*, Alev Alagam**, and Tuncer Degim***
Departments of 'Orthodontics, and **Pedodontics, Faculty of Dentistry, and ***Department of
Pharmaceutical Technology, Faculty of Pharmacy, Gazi University, Ankara, Turkey
The aim of this investigation was to examine the fluoride uptake by enamel after
application of glass ionomer cement for orthodontic band cementation compared with zinc
phosphate cement.
The study was conducted on 21 children whose mean age was 14 years. All the children
were reared in the Middle Anatolian cities where the water fluoride concentration was below
the level of 0.50 ppm. The subjects were randomly divided into three groups. The first
experimental group, had seven subjects whose teeth were topically fluoridated with 2 per
cent NaF solution, before orthodontic band cementation with zinc phosphate cement. The
second experimental group also had seven subjects whose orthodontic bands were
cemented with a glass ionomer cement. The third group, consisted of seven control subjects
and no dental procedures were performed in this group. All the participants were followed
for 3 months and at the end of this period maxillary first premolars, which were in the ninth
developmental stage according to Nolla (1960), were extracted for orthodontic purposes.
The enamel fluoride concentrations were determined on the left maxillary first premolars
at three successive etch depths by means of a fluor ion electrode, whereas the calcium
concentrations were determined with an atomic absorption spectrophotometer.
The results of this investigation showed that in both cementation groups enamel fluoride
concentrations at three successive etch depths were highly increased compared with the
control group. However, the difference between the cementation groups was not statistically
significant.
SUMMARY
Introduction
Since the inception of fixed orthodontic
appliances, discussions about their role on subsequent demineralization, cavitation and caries
has continued (Norris et al, 1986; Akkaya
and Alacam, 1990; Rezk-Lega et al, 1991).
According to Norris et al (1986), in addition
to seal breakdown, inadequate structural and
bonding strength, the solubility of currently
used dental cements in oral fluids, and poor
oral hygiene also contribute to the initiation of
decalcification.
It is clear that oral hygiene and other preventive measures can combat these effects. On the
other hand, most recent investigations have
concentrated on dental materials. Consequently,
the addition of fluorides to zinc phosphate
cements, to polycarboxylate cements and to the
bonding systems for resulting anticariogenic and
antibacterial benefits of fluoride release became
popular (Wei and Sierk, 1971; Retief et al,
1984; Tanaka et al, 1987; Temin et al, 1989;
Horsted-Bindslev and Larsen, 1990). Fluoride
has anticariogenic properties resulting from the
formation of less soluble fluoroapatite in the
outer enamel layer (Norris et al, 1986). Zinc
phosphate cements which have become the
standard cement used for cementation of orthodontic bands over the years, have some disadvantages, being brittle, having a relatively high
solubility in the mouth and weak adherence to
tooth substance.
Other dental cements have been developed
by researchers to overcome these drawbacks.
Polycarboxylate cements reacting chemically
with dental enamel and stainless steel were
presented as suitable cements for orthodontic
treatment. However, short setting time and high
viscosity became the main problems affecting
82
the popularity of these cements (Rich et al,
1975; Norris et al, 1986).
Glass ionomer cements, which were introduced in 1971, are based on the hardening
reaction between an aqueous solution of monomers or copolymers of acrylic acid and powdered calcium aluminosilicate glass (Hotz et al.,
1977). Via calcium bridges, hydrogen bonds or
other Van der Waal forces and phosphate substitution by which glass ionomers are bound
to enamel, glass ionomer cements provide a
stronger bond strength (Kopel and Batterman,
1976; Norris et al, 1986; Rezk-Lega et al. 1991).
In an in vitro study Retief et al. (1984) showed
fluoride uptake of enamel and cementum from
a glass ionomer cement. Also, Horsted-Bindslev
and Larsen (1990) concluded that the release
of fluoride was reduced by time in their investigation, although the fluoride concentrations
remained higher than necessary and were maintained for a long time.
This investigation aimed to examine the in
vivofluorideuptake by enamel at three different
depths, before and after band cementation,
using a fluoride releasing cement and a zinc
phosphate cement, the latter of which was used
after the application of topical fluoride, in order
to establish the biocompatibility of fluoride for
orthodontic cementation.
Subjects
Clinical phase
The study was conducted on 21 male children
whose mean age was 14 years. Their maxillary
first premolar teeth were in the ninth developmental stage according to Nolla (1960). All the
children were reared in Middle Anatolian cities,
where the water fluoride concentration was
below 0.50 ppm. The children in need of orthodontic treatment and whose healthy maxillary
first premolars were to be extracted for orthodontic purposes were randomly divided into
three groups. The first experimental group had
seven subjects whose teeth were topically fluoridated with 2 per cent sodium fluoride (NaF)
solution four times at weekly periods, before
orthodontic band cementation with zinc
phosphate cement (Adhesor®, Spofa Dental,
Czechoslovakia). The second experimental
group also had seven subjects whose ortho-
S. AKKAYA ET AL.
dontic bands were cemented with a glass ionomer cement (Voco Meron®, Voco, Cuxhaven,
Germany). The third group consisted of seven
control subjects and no dental procedures
were performed. The experimental teeth were
extracted after 3 months. Following careful
removal of the orthodontic bands and cements,
the teeth were cleaned of debris with pumice
and then rinsed with deionized water. They
were then stored in polyethylene tubes containing distilled water at 4°C until the analysis.
Laboratory phase
Enamel samples of left maxillary first premolar
teeth were obtained from the demarcated biopsy
sites by means of a modified acid etch microbiopsy procedure (McLean and Wilson, 1977;
Vogel et al, 1983; Soyman et al, 1984; Chow
etal, 1985; Retief et al, 1985).
A 3-mm length of adhesive tape was placed
on the vestibular surface of the teeth where
the orthodontic bands had previously been
applied. The remaining surfaces were covered
with Eudgarit s90 (Rohm Pharma GMBH,
Darmstadt, Germany) diluted in acetone. The
adhesive tape was removed and the teeth were
immersed and rinsed in the tubes containing
1 ml 0.5 M perchloric acid. After 60 seconds
4-ml aliquots of 0.5 M Total Ionic Strength
Adjustment Buffer (TISAB; Orion Research
Inc., Cambridge, MA, USA) was added to
perchloric acid and in this way 5 ml of biopsy
aliquot was prepared (first layer). This biopsy
technique was repeated separately three times
for each tooth (second and third layers).
Consequently, 25 ml TISAB solution was added
to each of the individual etch solutions and
fluoride was measured with a fluoride ion electrode (Bilmar model 101 ph mV tempmeter,
Russel model 96-6099 combined ion selective
electrode). Calcium concentration was measured with an atomic absorption spectrophotometer (Model 603, Perkin-Elmer, Norwalk,
CT, USA).
The weight and the volume of enamel
removed by each acid etch and the corresponding fluoride concentration were calculated by
use of the values of 2.95 for human enamel
density and 37 per cent for calcium content
(Wei and Sierk, 1971; Tanaka et al, 1987;
Temin et al, 1989). From the data obtained,
the depth of each biopsy was calculated by
means of the following equations (Aasenden
83
FLUORIDE UPTAKE FROM GLASS IONOMER CEMENT
and Moreno, 1971; Benediktsson et al, 1982;
Soyman et al., 1984):
mass of enamel=/*g Ca + + x (1 + 1000)
x (1 - 1000) x (100 -=- 37)g enamel
Depth of etch (cm) =
mass of enamel (g)
density of enamel x biopsy area (cm2)
The result of the equation must be multiplied
by 10000 in order to express the depth of etch
in fan. Usually, concentrations of trace elements
are expressed in parts per million (ppm), so the
following formula was used to state the ppm
fluoride in the biopsy samples:
Fluoride in the aliquot (fig)
Fluoride (ppm) =
Enamel in the aliquot (g)
Because the biopsy depth is an uncontrollable
variable, regression analysis was carried out by
using the enamel's three different depth levels
and the linear ppm fluoride in these depths. Via
the regression equation, ppm fluoride concentrations were adjusted to standardized depths
of 20, 40, and 60 /an. The evaluation of the
biopsy data of the groups for these three successive depths were statistically analysed by
Student's f-test and the mean ppm fluoride concentrations of the groups in relation to adjusted
enamel depths were compared by paired Mests.
Table 1 Fluoride uptake values (ppm) in standardized enamel depths of 20, 40, and 60 /on in control
group.
Tooth no.
20 /an
40 /an
60 /an
1
2
3
4
5
6
7
12888
7614
9116
6959
26386
4531
13866
12421
7633
8828
6337
19831
3031
13571
11971
7653
8549
5769
14905
2028
13283
Table 2 Fluoride uptake values (ppm) in standardized enamel depths of 20, 40, and 60 /an in glass
ionomer cementation group.
Tooth no.
20 /an
40 /an
60/an
1
2
3
4
5
6
7
55183
19587
47871
46454
18143
64917
19405
41019
18026
39797
41725
16587
62861
17944
30491
16589
33084
37478
15164
60870
16593
Table 3 Fluoride uptake values (ppm) in standardized enamel depths of 20, 40, and 60 /an in
zinc phosphate cementation group after topical
fluoridation.
Results
Tooth no.
20 /an
40/an
60/an
Mass of enamel (ng), depth of etch (/mi), /mi
fluoride in these depths, the disassociation
of ppm fluoride and calcium (fig) according to
samples after three biopsy applications in the
control group, in the group of glass ionomer
cementation, and in the topical fluoride
applicated group before zinc phosphate
cementation were calculated. Fluoride uptake
values in standardized enamel depth of 20, 40,
and 60 /xm are given in Tables 1, 2, and 3.
Mean ppm fluoride values at standardized
depths of enamel and the results of statistical
significance of the differences in the groups are
shown in Table 4 and Fig. 1. Mean ppm fluoride
at 20 /an depth was found to be 33 940 in the
glass ionomer cementation group, and 23115 in
the topically fluoridated group. These fluoride
concentrations were found to be statistically
significantly different from the control group
(P<0.05). However, the mean fluoride values
in the glass ionomer cementation group were
1
2
3
4
5
6
7
19019
27258
48482
14667
21331
12404
18644
18099
26197
43953
13162
20170
11753
16562
17224
25177
38848
14812
19072
11136
14712
not statistically significantly different from the
topically fluoridated group, although the results
were higher.
The results of mean ppm fluoride values at
the etch depths of 40 and 60 fan were parallel
to the results of the first etch depth. It was
observed that the mean fluoride concentrations
of the application groups were relatively higher
than in the control group, whereas the difference
between the application groups was not statistically significant. Furthermore, it was noted that
the ppm fluoride values decreased according to
the increase in depths in all the groups.
84
S. AKKAYA ET AL.
Table 4 Mean ppm F values at standardized depths
of enamel and the results of statistical importance
between the groups of glass ionomer cementation,
topical fluoridation before zinc phosphate cementation and control.
Glass
ionomer
cementation
Topical
F+ZnPO 4
cement
Control
S.I
20 fan
33940
SD: 22614
23115
SD: 12156
11623
SD: 7291
1-2:*
1-3:"
2-3:"
40/jm
33994
SD: 17280
21414
SD: 11018
10236
SD: 5535
1-2:*
1-3"
2-3"
60 fan
30038
SD: 16321
20283
SD: 9679
9165
SD: 4526
1-2:*
1-3**
2-3**
Depth
*: not significant.
**: significant at/><0.05 level.
Discussion
The presence of white spot lesions under orthodontic bands represents a serious problem of
clinical importance. Recent studies have shown
that glass ionomers may inhibit this type of
40
Control
lesion development and this outcome is generally attributed to the fluoride released from the
cement (Kvam et al, 1983; Valk and Davidson,
1987; Rezk-Lega et al, 1991).
The inhibition of enamel demineralization
and also the increase in the initial rate of
remineralization are generally acknowledged to
be the major beneficial effects of fluoride (RezkLega et al, 1991). Kvam et al (1983) showed
less enamel demineralization under orthodontic
bands attached with a glass ionomer cement
than under bands attached with a conventional
phosphate cement. The failure rate for bands
cemented with glass ionomers was also
significantly lower than the rate recorded for
bands cemented with a polycarboxylate cement
(Mizrahi and Smith, 1969). Because of these
characteristics, in one of the experimental
groups, orthodontic band cementation was
undertaken with a glass ionomer cement.
It is suggested that a slight increase in fluoride
may be capable of rendering a tooth more
resistant to dental caries if the concentration of
fluoride in the outer most layer of enamel is the
critical factor (Heifetz et al, 1970). Brunn et al
(1983) demonstrated that the production of
Glass
ionomer
cementation
|
Topical fluoridation
before zinc phosphate
cementation
35
30
25
LL
20
15
10
40
Enamel depth dim)
60
Figure 1 The values of ppm F in 20, 40, and 60 itsa standardized enamel depths of experimental groups.
FLUORIDE UPTAKE FROM GLASS IONOMER CEMENT
soluble or insoluble products reduced caries
attack; thus, the need for removal of the alkali
soluble products, which include calcium fluoride
(potassium hydroxide) according to the method
described by Caslavska et al. (1975) should be
re-evaluated.
McLean and Wilson (1977) concluded that
while the cement becomes attached via ionic
and polar bonds to the enamel, the intimate
molecular contact facilitates fluoride ion
exchanges with the hydroxyl ions, whereas a
luting agent that does not adhere by molecular
interactions would leave gaps between the
cement and the tooth. Therefore, even if such a
luting agent were to release fluoride, ion
exchange would be inhibited. On the other
hand, in their in vivo investigation of two glass
ionomer cements, Rezk-Lega et al. (1991) have
concluded that although the cements had cariostatic properties, fluoride protection against
lesion development beneath orthodontic bands
could be weak, because the fluoride released
from the cement did not cover the enamel
crystallites completely. They pointed out that
another possible reason for poor response was
the magnitude of the cariogenic challenge
beneath the bands being so intense, as it is
known that below a pH of 4.5 fluoride would
have a limited effect.
Because of this, topical fluoride application
before cementation with a zinc phosphate
cement was preferred as an alternative in this
investigation. The reaction of topical fluoridation is known to be in two phases. Calcium
fluoride which is a soluble first reaction product
can change into tightly bound fluoride after
repeated applications (Cebe, 1973; Clarkson,
1991). In many investigations it has been
observed that the fluoride concentration on the
surface enamel showed individual differences
according to the area of its application and
enamel fluoride acquired from topical fluoride
treatment is inversely related to the enamel
fluoride content prior to its application (Heifetz
et al, 1970; RytSmaa et al, 1974; Benediktsson
et al., 1982). So, in comparative studies in which
fluoride acquired from topical fluoride agents
were evaluated, it would be preferable if teeth
with similar fluoride concentrations were used.
This investigation was conducted on children
reared in Middle Anatolian cities where the
water fluoride concentrations were below
0.50 ppm (Erkan et al, 1991). On the other
85
hand, analysis of fluoride in the micro-samples
of the enamel spectrophotometrically or by
means of fluoride ion electrode, gas chromatography and sensitive physical methods have
shown that there were three biologically important variables affecting the values; the origin of
the tooth, the particular tooth surface measured
and the position of the point analysed on a
single surface (Rytomaa et al, 1974).
The standardization of the donors' ages in
addition to the developmental stage of the teeth
was necessary as the fluoride acquisition of
young teeth was different from older ones and
enamel fluoride acquired was based upon maturation (Nolla, 1960). Since the enamel fluoride
concentration of boys was 10 per cent higher
than girls, and the fluoride concentrations of
different teeth were found to vary, the determination of tooth type and sex of donor were
also required (Jenkins, 1978).
In this study all the biological variables discussed were standardized as far as possible by
conducting the clinical phase on male children
whose mean age was 14 and the developmental
stage of their maxillary first premolars was the
same. Also the enamel samples of experimental
teeth were obtained from demarcated biopsy
sites on the vestibular surfaces by means of the
window technique. Although initial and final
enamel fluoride concentrations at specific points
of homologous teeth or at similar surfaces of
dissected teeth could be determined in vitro
(Guo et al, 1989; Fischer-Brandies et al, 1991;
Us, 1991), the results are questionable when
these conditions are provided in vivo (Eliades
et al, 1992; Seppa et al, 1992).
•On the other hand, it is concluded that caries
activity of the donor increases according to the
count of Lactobaccillus in the saliva due to
hygienic difficulties derived from orthodontic
treatment (Zachrisson and Brobakken, 1978;
Mizrahi, 1982; O'Reilly and Featherstone,
1987). Because of this, bilateral teeth were not
used as controls in this study. Consequently,
the results of this investigation should not be
compared with the results of similar in vitro
investigations.
The fluoride acquired by the enamel and
cementum from a glass ionomer cement in the
in vitro studies may largely be due to the topical
effect of the released fluoride in the synthetic
saliva. In the clinical situation a tooth is constantly bathed in saliva which is replenished by
86
the salivary flow. So, in vivo experimentally
observed enamel fluoride concentrations will be
less than the in vitro studies (Retief et al, 1984;
Horsted-Bindslev and Larsen, 1990).
It is considered that 1000 ppm enamel fluoride concentration through 30 /an depth seems
sufficient for a considerable preventive effect
(Cebe, 1973). This depth may be minimally
more or less. Fluoride concentration at superficial enamel level, in addition to 60 /an depth,
was observed to be greater than necessary for
a preventive effect in this study. The findings of
reduced fluoride level with an increase in depth
were in agreement with previous studies,
although statistically insignificant.
The results of this investigation showed that
fluoride concentration at three etch depths was
higher in the glass ionomer cementation group
than in the topical application group, although
there was no statistically significant difference.
On the other hand, it must be pointed out that
the increase in the number of the experimental
teeth might have affected the statistical
significance.
Both in vivo and in vitro studies have supported the finding that the release, of fluoride
was reduced by time for all; glass ionomer
cements (Olsen et al, 1989; (Hx>rsted-Bindslev
and Larsen, 1990; Koch' and HatibovicKofman, 1990; Hatibovic-Kofman and Koch,
1991). Therefore, it may be postulated that the
higher the release of fluoride, the higher the
caries inhibitory effect. The results of the present
study also confirm this hypothesis. However,
considering 1-3 ppm fluoride in solution was
sufficient for a preventive effect, the fluoride
concentrations were found to be adequate
even after 3 months in an investigation by
Horsted-Bindslev and Larsen (1990).
On the other hand Norris et al. (1986) concluded that the glass ionomer cements were
most effective in adhering to the tooth surface
in their experimental study, where the retention
of orthodontic bands with zinc phosphate, polycarboxylate, and glass ionomer cements were
evaluated. The investigators suggested that even
under loose bands, the glass ionomer cement
adhered to the enamel and, therefore, may offer
clinical protection against decalcification.
Supporting this idea, Koch and HatibovicKofman (1990) also showed that the prevalence
of S. mutans in saliva decreased after placement
of a glass ionomer cement restoration.
S. AKKAYA ET AL.
So, evaluating all these findings it is concluded that, glass ionomer cement is an alternative to topical fluoride application before
cementation with zinc phosphate cement. It has
a popular clinical application because of high
adhesion capacity to the tooth enamel and also
provides an increment in enamel fluoride
content.
Address for correspondence
Associate Professor Dr Sevil Akkaya
Gazi University
Faculty of Dentistry
Department of Orthodontics
06510 Emek
Ankara, Turkey
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