The effect of fluoride on orthodontic tooth movement in humans. A two- and three-dimensional evaluation.

Abstract

The aim of the present study was to determine whether high and low fluoride concentrations in drinking water affected the early stages of tooth movement when heavy and light orthodontic forces were applied for 4 weeks. A further aim was to compare and evaluate the resulting two-dimensional (2-D) and three-dimensional (3-D) orthodontic tooth movement.
The sample consisted of 96 maxillary upper first premolars from 48 patients who required premolar extractions as part of their orthodontic treatment. Patients were selected from two different cities in Turkey with low and high fluoride concentrations of 0.05 and 2 ppm, respectively. The patient sample was divided into four groups according to the magnitude of force applied to the first premolars and the concentration of fluoride in the public water supply; Group 1, High fluoride intake (> or = 2 ppm)-Heavy force (225 g); Group 2, Low fluoride intake (< or = 0.05 ppm)-Heavy force; Group 3, High fluoride intake-Light force (25 g); and Group 4, Low fluoride intake-Light force. A light or heavy buccal tipping orthodontic force was applied to the upper first premolars for 4 weeks. The first three palatal rugae were used for the superimposition of patient casts in a 2-D and 3-D evaluation of generated movements.
It was found that heavy force application and fluoride intake increased the average rate of tooth movement. It was further shown that age was negatively correlated with tooth movement in the 2-D and 3-D measurements.
The average rate of tooth movement was found to be greater in the heavy force and high fluoride intake group (Group 1HH). Age was negatively correlated with orthodontic tooth movement. Two- and three-dimensional methods were accurate for the assessment of tooth movement after four weeks of buccal tipping force application when the palatal rugae were used for superimposition.

Full text

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Australian Orthodontic Journal Volume 27 No. 2 November 2011
94
© Australian Society of Orthodontists Inc. 2011
Aims: The aim of the present study was to determine whether high and low fluoride concentrations in drinking water affected
the early stages of tooth movement when heavy and light orthodontic forces were applied for 4 weeks. A further aim was to
compare and evaluate the resulting two-dimensional (2-D) and three-dimensional (3-D) orthodontic tooth movement.
Methods: The sample consisted of 96 maxillary upper first premolars from 48 patients who required premolar extractions as part
of their orthodontic treatment. Patients were selected from two different cities in Turkey with low and high fluoride concentrations
of 0.05 and 2 ppm, respectively. The patient sample was divided into four groups according to the magnitude of force
applied to the first premolars and the concentration of fluoride in the public water supply; Group 1, High fluoride intake (≥ 2
ppm)-Heavy force (225 g); Group 2, Low fluoride intake (≤ 0.05 ppm)-Heavy force; Group 3, High fluoride intake-Light force
(25 g); and Group 4, Low fluoride intake-Light force. A light or heavy buccal tipping orthodontic force was applied to the upper
first premolars for 4 weeks. The first three palatal rugae were used for the superimposition of patient casts in a 2-D and 3-D
evaluation of generated movements.
Results: It was found that heavy force application and fluoride intake increased the average rate of tooth movement. It was
further shown that age was negatively correlated with tooth movement in the 2-D and 3-D measurements.
Conclusions: The average rate of tooth movement was found to be greater in the heavy force and high fluoride intake group
(Group 1HH). Age was negatively correlated with orthodontic tooth movement. Two- and three-dimensional methods were
accurate for the assessment of tooth movement after four weeks of buccal tipping force application when the palatal rugae were
used for superimposition.
(Aust Orthod J 2011; 94-101)
Received for publication: December 2010
Accepted: July 2011
The effect of fluoride on orthodontic tooth
movement in humans. A two- and three-
dimensional evaluation
Ersan Ilsay Karadeniz,* Carmen Gonzales,† Selma Elekdag-Turk,+ Devrim Isci,+
Aynur M. Sahin-Saglam,± Huseyin Alkis,‡ Tamer Turk+ and M. Ali Darendeliler†
Department of Orthodontics, The University of Sydney, Sydney, Australia;* Department of Orthodontics, The University
of Sydney, Sydney Dental Hospital, South Western Sydney Area Health Service, Sydney, Australia;† Department of
Orthodontics, Faculty of Dentistry, Ondokuz Mayis University, Samsun, Turkey;+ Inci-Dent Dental Hospital, Isparta,
Turkey± and Department of Orthodontics, Faculty of Dentistry, Suleyman Demirel University, Isparta, Turkey‡
Introduction
Due to its protective ability against demineralization,
fluoride in public water supplies is widely recognised
as an effective means of preventive dentistry. Fluoride
is almost entirely stored in human calcified tissues1
and is actively involved in bone metabolism. Its
concentration in calcified tissues increases with age2
and is directly related to the fluoride concentration in
consumed water.3
Orthodontic treatment moves teeth through alveolar
bone by remodelling and adaptive changes of the
paradental tissues.4 The early phase of tooth movement
occurs due to a sterile inflammatory response and the
activation of several mediation pathways. The rate of
movement is governed by several variables related to
the magnitude, direction, distribution and duration
of force application, initial tooth displacement
coupled with stress, strain, and biologic changes in
Ersan Ilsay Karadeniz: eikdeniz@hotmail.com; Carmen Gonzales: gonzales_carmenb@yahoo.com; Selma Elekdag-Turk: elekdagturk@yahoo.com
Devrim Isci: devrimisci@yahoo.com; Aynur M. Sahin-Saglam: asahinsaglam@yahoo.com; Huseyin Alkis: husam_DT_34@hotmail.com
Tamer Turk: turkset@superonline.com; M. Ali Darendeliler: ali.darendeliler@sydney.edu.au

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THE EFFECT OF FLUORIDE ON ORTHODONTIC TOOTH MOVEMENT
the periodontium.5-7 The effect of fluoride on these
processes is unclear.
Fluoride is well known to influence osteoblastic
activity,8-10 but there are conflicting findings regarding
the effect of fluoride on clast cell activity and their
crucial role in orthodontic tooth movement. While
previous studies have shown that fluoride reduces the
rate of orthodontic tooth movement in animals,11,12
the effect of fluoride on tooth movement has not been
studied in humans. Therefore, the aim of the present
study was to determine whether high and low levels of
fluoride in drinking water affected orthodontic tooth
movement under heavy and light force application.
A secondary aim was to compare the resulting
tooth movement in a 2-dimensional (2-D) and a
3-dimensional (3-D) evaluation.
Materials and methods
Ninety-six premolars from 48 patients (23 male, 25
female; Mean age: 15.27 years; Range 11.75 - 20 years)
were selected from two different cities in Turkey, each
having a concentration of 0.05 and 2 ppm fluoride
in the public water supply, respectively. Patients were
selected using the following criteria: 1) no previously
reported or observed dental treatment to the teeth to
be extracted as part of an orthodontic treatment plan;
2) no previous reported or observed trauma to the teeth
to be extracted; 3) no previous reported orthodontic
treatment; 4) no past or present signs or symptoms
of periodontal disease; 5) no past or present signs
or symptoms of bruxism; 6) no significant medical
history; 7) no physical abnormality concerning the
anatomy of the craniofacial or dentoalveolar complex;
8) apexification completed on all teeth, and 9) patient
residing in a particular city from birth.
Ethics approval was provided by the Medical Faculty
Ethics Committee of the Ondokuz Mayis University
in Turkey. All subjects and their guardians consented
to participate in the study after receiving verbal and
written explanations.
Twenty-four subjects from each of the low and
high fluoride areas were randomly divided into two
groups to receive either a light or heavy level of force
application. There were four groups (12 subjects in
each) comprising Group 1HH, High fluoride intake-
Heavy force; Group 2LH, Low fluoride intake-Heavy
force; Group 3HL, High fluoride intake-Light force
and Group 4LL, Low fluoride intake-Light force
(Figure 1). The patients’ maxillary first premolars were
exposed to either light (25 g; Groups 3HL and 4LL) or
heavy (225 g; Groups 1HH and 2LH) buccal tipping
orthodontic force over 4 weeks. Polyvinylsiloxane
impressions (Imprint II Regular Body/Light Body, 3M
ESPE, St Paul, MN, USA) were taken at the beginning
(T0) and at the end of the 4-week period (T1).
Appliance design
Speed brackets with a 0.022 inch slot (Strite Industries,
Cambridge, ON, Canada) were bonded onto the buc-
cal surfaces of the maxillary first permanent molars and
first premolars (Figure 2). Self-ligating brackets were
selected to allow for standardised ligation of the experi-
mental teeth. Subjects in Groups 3HL and 4LL had
25 g of buccally-directed force delivered to their premo-
lars by a 0.016 inch beta-titanium-molybdenum alloy
cantilever spring (Rematitan, Dentaurum, Ispringen,
Germany). Subjects in Groups 1HH and 2LH had 225 g
of buccally-directed premolar force delivered by a 0.017
x 0.025 inch beta-titanium-molybdenum alloy cantile-
ver spring (Beta III Titanium, 3M Unitek, Monrovia,
CA, USA). The force magnitude was measured and
checked using a strain gauge (Dentaurum). Light-cured
band cement (Transbond Plus, 3M Unitek) was bonded
onto the occlusal surfaces of the mandibular first perma-
nent molars to increase the subject’s vertical dimension
and therefore minimize occlusal trauma to the maxil-
lary first premolars during the experiment (Figures 2b
and c).
Figure 1. Study design.

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KARADENIZ ET AL
Two-dimensional evaluation
Impressions were taken of each patient at the
beginning and end of the 4-week treatment period
and poured in type 1 dental stone to produce study
casts. Medial and lateral ends of the first three palatal
rugae were identified as stable reference points on the
casts. Buccal and palatal cusps of each premolar were
marked with a 0.3 mm lead pencil. The casts were
scanned (Expression 1600 flatbed color image scanner,
Epson Australia Pty Ltd., Chatswood, Australia)
at 1200 dpi and 16-bit grey scale from an occlusal
perspective (Figures 3a and b). The superimposition of
the samples was done manually in Adobe Photoshop
software by matching the previously-marked reference
points (Figure 3c). In order to calculate the rate of
tooth movement, the buccal and palatal cusps were
measured separately (Figures 3d and 3e) and averaged.
Each measurement was repeated four times and the
mean value was determined for each sample.
Three-dimensional measurements
After the 2-D evaluation, the T0 and T1 casts were
scanned by OpenScan 3-D Laser Scanner (Laserdenta
GmbH, Germany) at a resolution of 20 microns (0.02
mm). The high-resolution scans were stored as Surface
Tesselation Language (STL) formatted files and
processed with VG Studio Max version 2.1 (Volume
Graphics, Germany) (Figure 4). The same reference
points used in the 2-D evaluation were superimposed
by the software and the amount of movement at the
buccal and lingual cusps was calculated and averaged
(Figures 4c, d and e). Each measurement was repeated
four times and the mean value was determined for
each sample.
Statistical analysis
All statistical analyses were undertaken with the
Statistical Package for the Social Sciences software
(SPSS for Windows, version 16, SPSS, Chicago, IL,
USA). A Univariate Analysis of Variance (ANOVA)
between the groups was performed. Bonferroni
corrections were applied for multiple comparisons
and a Pearson correlation coefficient was used to
evaluate possible correlations between age, gender,
root resorption and orthodontic tooth movement.
Statistical significance was set at the p ≤ 0.05 level. All
measurements were done by the same researcher (EK).
Results
Calculated using ANOVA and derived from the mean
square error, the standard error of measurement for
the 2-D evaluation was found in Group 1HH to be
0.060 mm; Group 2LH, 0.025 mm; Group 3HL,
0.060 mm and Group 4LL, 0.050 mm (Table I). The
3-D error evaluation was found in Group 1HH to be
0.095 mm; Group 2LH, 0.090 mm; Group 3 HL,
0.080 mm and Group 4LL, 0.035 mm, respectively.
Two-dimensional evaluation
After the 2-D analysis of tooth movement, the
following results were recorded. Teeth in Group 1HH
moved 1.60 mm; Group 2LH, 1.33 mm; Group 3
HL, 1.25mm and Group 4LL, 1.02 (Table I). The
average rate of tooth movement was found to be
greater in heavy force groups (Groups 1HH and 2LH).
However, this effect was only statistically significant in
Group 1HH when compared with Group 4LL (p =
0.004) (Figure 5). There was no significant difference
between heavy and light forces.
Figure 2. Appliance in situ. (a) Maxillary occlusal view, (b) Lateral view (right), (c) Lateral view (left).
(a)(b)(c)

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THE EFFECT OF FLUORIDE ON ORTHODONTIC TOOTH MOVEMENT
Figure 3. Two-dimensional analysis.
(a)(b) (c)
(d)(e)
Figure 4. Three-dimensional analysis.
Sex AgeTooth movement -Two dimensions (mm)Tooth movement - Three dimensions (mm)
N Male Female Average Range MinimumMaximum Mean SD SEMinimum Maximum Mean SDSE
Group 1 HH 125715.411.8-21.30.393.131.600.88 0.060.343.181.610.88 0.10
Group 2 LH1266 15.O14.0-17.0 0.722.91 1.330.53 0.03 0.64 2.361.31 0.50 0.09
Group 3 HL 1266 15.413.1-17.80.69 1.90 1.250.36 0.06 0.46 1.981.150.44 0.08
Group 4 LL 126615.113.5-16.50.381.83 1.02 0.34 0.050.30 1.671.06 0.39 0.04
Table I. Descriptive statistics.
Group 1HH, High fluoride intake-Heavy force; Group 2LH, Low fluoride intake-Heavy force; Group 3HL, High fluoride intake-Light force and Group 4LL,
Low fluoride intake-Light force.
SD, standard deviation; SE, Standard error of measurement
(a)(b)(c)
(d)(e)

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KARADENIZ ET AL
The rate of tooth movement was higher in subjects
with a high fluoride intake (Groups 1HH and 3HL).
Under a heavy force, high fluoride intake patients
showed 20 per cent (Group 1HH) more tooth
movement than low fluoride intake patients (Group
2LH) while under light force this difference was 22
per cent. However, this effect was not statistically
significant except for Groups 1HH and 4LL
(Figure 5).
Three-dimensional evaluation
Similar results were recorded after the 3-D evaluation.
The average rate of tooth movement was determined to
be 1.61 mm for Group 1HH, 1.31 mm for Group 2LH,
1.15 mm for Group 3HL and 1.06 mm for Group 4LL
(Table I). Heavy force groups showed a higher rate of
tooth movement than light force groups. There was a
significant difference between Group 1HH and Group
3HL and Group 1HH and Group 4LL with p values of
0.015 and 0.05, respectively (Figure 6).
High fluoride intake patients had a higher rate of
tooth movement than low fluoride patients under
both heavy and light force application. Under heavy
force, this rate was 22 per cent higher while under
light force it was 8 per cent.
Comparison of the methods
No difference was found between the 2-D and 3-D
evaluation of tooth movement. The difference in the
rate of tooth movement between the two methods was
found to be: in Group 1HH, 0.01 mm; Group 2LH,
0.02 mm; Group 3HL, 0.1 mm and in Group 4, 0.04
mm. The p values between the methods in each group
were 0.917, 0.813, 0.267 and 0.338, respectively
(Figure 7). The accuracy of the methods increased
when the rate of tooth movement was high (Groups
1HH and 2LH).
It was found that heavy force application and fluoride
intake increased the average rate of tooth movement.
However, no statistically significant difference was
observed between fluoride concentration and the rate
of tooth movement between the groups. It was further
determined that age was negatively correlated with
tooth movement in both 2-D and 3-D measurements.
However, no significant correlation was found between
gender and tooth movement (Table II).
Figure 5. Rate of tooth movement in two-dimensional analysis.
Mean difference significant at *0.05 level
Figure 6. Rate of tooth movement in three-dimensional analysis.
Mean difference significant at *0.05 level
Figure 7. Comparison of tooth movement in two- and three-dimensional
analysis.

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THE EFFECT OF FLUORIDE ON ORTHODONTIC TOOTH MOVEMENT
Discussion
The literature has identified biological, mechanical
and genetic factors which affect the rate of orthodontic
tooth movement.5-7,13,14 In the present study, it was
noted that inter-individual variation had a marked
effect (Table I) but applied force magnitude was also
revealed as significant.5,7,15 Heavy force application
produced more tooth movement compared with
light forces, which supported the findings of Yee
et al.7 Moreover, Owman-Moll16 found that when
continuous force was increased from 50 g to 200 g,
tooth movement increased 50 per cent. This effect was
also described by Paetyangkul et al.15 who reported that
after the application of heavy (225 g) and light force
(25 g) for 12 weeks, a two-fold increase in the rate
of tooth movement was observed in the heavy force
group. In contradistinction, Gonzales et al.5 found
that light force application produced more tooth
movement. An applied 10 g force produced more
movement than 25, 50 and 100 g in rats. However,
the conversion of these force levels into human terms
rendered them comparatively high. A relatively light
force (20 g) applied to rat molars matched a heavy
force level (225 g) in humans.
The identification of an optimal force for effective
tooth movement is problematic and controversial.
Proffit14 suggested that optimum force for buccal
tipping was between 30 and 60 grams. This was
criticized by Von Bohl,17 who stated that these values
ignored other parameters such as the surface area
of the roots, the alveolar bone and the geometry of
the periodontal ligament (PDL) related to force
application. In the present study, force levels of 25 g
and 225 g were considered as a light force and a heavy
force, respectively, and were selected in order to cover
the force range likely to be applied to a tooth during
orthodontic treatment. These considerations have
been substantiated by Schwartz18 and Proffit.14
Gonzales et al.5 and Yee et al.7 found that force
magnitude did not have an effect on tooth movement
after 14 days of application but a difference in tooth
movement was evident after 28 days. Therefore, 28
days was selected as an appropriate period likely to
reveal differences in force magnitude and fluoride
effects in the early phase of tooth movement. This
time period was further chosen as the shortest
experimental time to minimise force decay, as well
as control patient-related problems such as appliance
breakages.
Unfortunately, genetic
confounding influences. Iwasaki et al.19 postulated
that at least one copy of allele 2 at IL-1B (+3954)
was possibly associated with faster tooth movement
in humans. Moreover, Abass et al.20 demonstrated
that susceptibility to orthodontic root resorption
and its direct association with tooth movement15 is
a heritable trait in mice. In addition, Al-Qawasmi21
showed that genotype was a significant factor in the
response to an orthodontic force. In the present study,
systemic diseases and trauma to experimental teeth,
factors may provide
Tooth movement 2-D
Tooth movement 3-D
.827**
0
96
Age
-.279**
0.005
96
-.389**
0
96
Gender
0.169
0.096
96
0.088
0.399
96
-0.1
0.326
96
Tooth movement 2-D
Correlation
P
N
Correlation
P
N
Correlation
P
N
Correlation
P
N
Tooth movement 3-D
.827**
0
96
-.279**
0.005
96
0.169
0.096
96
Age
-.389**
0
96
0.088
0.399
96
Sex
-0.1
0.326
96
Table II. Correlations between sex, age and tooth movement.
** Correlation is significant at the 0.01 level

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Australian Orthodontic Journal Volume 27 No. 2 November 2011
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KARADENIZ ET AL
before or during the experiment, were the basis for
subject exclusion. Unfortunately, in human studies, it
is not possible to account for a genetic factor-related
response to orthodontic force application, which may
be considered as a shortcoming of the present study.
Therefore, the effect of fluoride on tooth movement
should best be evaluated over longer experimental
periods as well as under different types of tooth
movement.
The effect of age on orthodontic tooth movement
has been assessed in several human19,22,23 and animal
studies.24,25 The present study identified a significant
negative correlation between tooth movement and
age (Table II). This finding is in agreement with
Darendeliler et al.22 and Cheng et al.23 who previously
indicated the negative age correlation with orthodontic
tooth movement. Moreover, Iwasaki et al.19 showed
that tooth movement in growing patients was twice
that of non-growers. Unfortunately, the growth status
of the patients was not investigated in the present study.
The effect of fluoride on orthodontic tooth movement
was previously investigated by Hellsing and
Hammarstrom11 who reported that fluoride, delivered
via a subcutaneous osmotic pump in rats, reduced the
rate of tooth movement. In addition, it was found that
the number of osteoclasts on the pressure side of the
PDL decreased significantly. In an allied investigation,
Gonzales et al.12 examined the effect of fluoride on rat
orthodontic tooth movement from birth. It was again
found that the early administration of fluoride reduced
the amount of tooth movement as did the duration
of fluoride administration. The longer the fluoride
was administered via drinking water, the smaller
the amount of tooth movement. These findings are
at variance with the results of the present study and
may possibly be explained by the extremely high
concentration of fluoride (15 mg per 1000 g body
weight11 and 45 ppm12) delivered in previous studies.
These concentrations are known to be toxic in human
beings. The present study exposed subjects to 2 ppm
fluoride concentration provided via the public water
supply. In comparison with the fluoride intake used
in animal experiments, the concentration of natural
fluoride in the present study was extremely low.
Controversy surrounds the effect of fluoride on clast
cell activity as the responsible entity governing bone
resorption during orthodontic tooth movement.
Due to interactions between fluoride dosage, calcium
and vitamin D consumption, species differences,
duration of fluoride supply and individual sensitivity,
the issue remains multifactorial and undetermined.3
No previous study has shown the effect of fluoride
on orthodontic tooth movement in human subjects.
Therefore, more human studies should be performed
to validate the results of the present study.
The measurement of tooth movement was accom-
plished by two-dimensional and three-dimensional
methods. Past two-dimensional evaluations of tooth
movement have been hampered by difficulties in
identifying inherent landmarks in all dimensions.26 A
three-dimensional-analysis may be measured quickly
and with great accuracy using the palatal rugae as
reference areas during growth.27 However, the stabil-
ity of the palatal rugae has been questioned. Van der
Linden28 and Almeida et al.29 argued for palatal rugae
stability, while Friel et al.30 and Simmons et al.31 re-
ported contrary findings. Alternatively, Choi et al.26
advised that the superimposition of maxillary casts on
the palatal vault was accurate. As a future solution, it
is suggested that miniscrew placement be considered
as a stable reference point for superimposition of the
models.
In the present study, the area defined by the first three
palatal rugae was used for the superimposition of casts
and employed a surface to surface mathematical best
fit method. It was verified that there was no difference
between the 2-D and 3-D evaluation methods. This
was likely due to the short duration of the experiment
in which movement in the third dimension did
not affect mean tooth movement significantly. In
addition, due to the short experimental time period,
the potential effects of maxillary growth on palatal
rugae may be considered negligible.
Conclusions
The following conclusions have been drawn regarding
orthodontic tooth movement after four weeks of light
and heavy buccal tipping forces applied on maxillary
first premolars in subjects who live in regions of high
and low fluoride concentrations in the public water
supply:
1. The average rate of tooth movement was found
to be greater in the heavy force and high fluoride
intake group (Group 1HH).
2. Age was negatively correlated with orthodontic
tooth movement.
3. Two- and three-dimensional methods were accu-
rate for the assessment of tooth movement after

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THE EFFECT OF FLUORIDE ON ORTHODONTIC TOOTH MOVEMENT
four weeks of buccal tipping force application
when the palatal rugae were used for superimpo-
sition.
Corresponding author
Professor M. Ali Darendeliler
The University of Sydney
Faculty of Dentistry
Discipline of Orthodontics
Level 2, 2 Chalmers Street
Surry Hills, NSW 2010
Australia
Email: ali.darendeliler@sydney.edu.au
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