158

Introduction
Interproximal enamel reduction is a method in
orthodontics for the removal of minimal amounts
of enamel from the approximal tooth surfaces [1-4].
This method is appropriate and applicable for
patients with crowded anterior teeth, crowding of
the dental arches, problems with the morphology
and/or size of the dental crowns, and also for the
elimination of the black triangles to improve
smile aesthetics [5-8]. Interproximal enamel reduc-
tion, when performed appropriately and correctly,
creates wide enough contact surfaces, which may
improve stability after orthodontic treatment [1,3].
Excessive reduction of the enamel can lead to
hypersensitivity and irreversible damages of the
dental pulp [2,6]. The approximal tooth surfaces
are zones with active formation of plaque biofilm
[9-11] due to stagnation under the interdental con-
tact-points, which are difficult areas to self-cleanse
and brush. The plaque biofilm is also a factor in
caries development [12-14].
Therefore, it is important to establish whether
there is enamel damage on interdental surfaces
before performing enamel reduction and whether
there is further aggravation following enamel
reduction. It has been accepted that enamel reduc-
tion should be performed on patients with very
good oral hygiene and low caries risk [15-17]. It is
commonly held that stripping of the lower incisors
should not be more than 0.5 mm [18-21] of each
approximal tooth surface [22]. It is very important
to promote remineralisation of the enamel in order
to guarantee the success of this technique [22-25].
The assessment of the degree of surface dem-
ineralisation, if any, and an examination of the sta-
tus of the enamel after its partial removal are cru-
cial [26-29]. Visual methods for determining the
initial demineralisation and the remineralisation
Qualitative Evaluation of Changes In Vivo After Interproximal
Enamel Reduction
Panagiotis Michail Kanoupakis
1
, Milena Dimitrova Peneva
2
, Valentin Yordanov
Moutaftchiev
3
1
Candidate Ph.D, Department of Orthodontics, Faculty of Dental Medicine, Medical University, Sofia, Bulgaria.
2
Ph.D., D.M.D.
Professor, Department of Paediatric Dentistry, Faculty of Dental Medicine, Medical University, Sofia, Bulgaria.
3
Ph.D., D.M.D.
Professor, Department of Orthodontics, Faculty of Dental Medicine, Medical University, Sofia, Bulgaria.
Abstract
Aim: To use a laser fluorescence device to assess the qualitative changes in interproximal enamel after enamel reduction
(interproximal stripping). Methods: Fifty-three patients (32 females and 21 males) with an average age of 15.6 years
took part in the investigation. Five hundred and thirty-five tooth surfaces of upper and lower anterior teeth were
reassessed at three days, ten days, and one month after enamel reduction using a laser fluorescence method
(DIAGNOdent pen). Remineralisation was promoted by the application of fluoride gel and control of oral hygiene.
Results: The results showed that there is no risk for developing caries after stripping in cases where intact enamel sur-
faces registered values of between 0 and 3 when measured with the laser fluorescence method used in this study. Enamel
reduction appeared to be appropriate even for surfaces with initial demineralisation of the outer enamel, with values
between 4 and 6, because after fluoride application the enamel status returned to within a normal range (0-3).
Conclusion: The results from this study demonstrate that with correct diagnosis, as well as selection of intact or even
slightly demineralised enamel surfaces, successful implementation of enamel reduction within enamel is possible. This
technique, precisely planned, correctly executed, and followed by remineralisation procedures, eliminates the risk of
enamel demineralisation.
Key Words: Interproximal Enamel Reduction, Laser Fluorescence Method, DIAGNOdent Pen, Remineralisation
Corresponding author: Dr. Panagiotis Kanoupakis, Department of Orthodontics, Faculty of Dental Medicine, 1431, St.
Georgi Sofiiski Blvd, 1, Medical University, Sofia, Bulgaria; e-mail: panagiotis@abv.bg
159
OHDM - Vol. 10 - No. 3 - September, 2011
after treatment are difficult to apply to approximal
tooth surfaces. During the past years, instruments
for this type of diagnosis have been developed and
used mainly in vitro, based on different principles
such as laser fluorescence devices QLF (quantita-
tive light-induced fluorescence) [30,31] and
DIAGNOdent [31-34], ultrasound ULS [35], and
measurement of electrical conductivity ECM (elec-
trical conductivity method) [33].
The DIAGNOdent pen (Kavo Dental GmbH,
Biberach, Germany) has proved to be one of the
most practical instruments for this purpose, as it
includes an approximal flat-tip probe for detection
of initial enamel demineralisation on approximal
tooth surfaces [34-36].
Aim
The aim of this study was to assess the status of
enamel approximal surfaces in vivo with the help of
a laser fluorescence device, before and after enam-
el reduction, and its subsequent remineralisation.
Methods
A convenience sample of 53 patients (aged between
12 and 24 years) was collected out of 110 patients
who had been treated orthodontically by postgraduate
students over an 18-24-month period in the
Department of Orthodontics, Faculty of Dental
Medicine, Medical University of Sofia, Bulgaria.
The patients came from different regions of
Bulgaria and, with their parents consent where
appropriate, agreed to participate in the study after
receiving verbal and written information. Ethical
permission to conduct the study was obtained from
the Ethics Committee of the Medical University of
Sofia. One calibrated orthodontist collected and
performed all the measurements and readings.
Criteria for patients selection included opti-
mal alignment of anterior teeth during their ortho-
dontic treatment with brackets and, also, no prior
stripping procedures on these teeth. All patients had
good oral hygiene with an average plaque score of
0.56 before enamel reduction.
The follow-up period for all patients who had
been assessed with the DIAGNOdent pen was one
month after enamel reduction. Twenty-seven
patients were available nine months after enamel
reduction and were assessed again after this period.
Assessment of enamel status
The diagnostic laser fluorescence (LF) measure-
ments were carried out with a DIAGNOdent pen.
The DIAGNOdent pen is a mobile laser device
caries detector allowing reading values from 0-99.
The main unit generates laser light with a wave-
length of =655nm, which is absorbed by both
organic and inorganic tooth structure and re-emit-
ted as fluorescence within the red and infrared
region. The underlying mechanism is that deminer-
alised tissue emits stronger fluorescence than intact
tissue in the red and infrared part of the spectrum.
Thus, the fluorescence from a demineralised region
greater than that from intact tissue is expressed as a
higher numerical read-out by the device.
Before using the DIAGNOdent pen, the enam-
el status of the upper and lower anterior teeth was
determined visually. First, the device was calibrat-
ed using a ceramic standard, provided by the man-
ufacturer. Its reference value (e.g., C58) was
engraved into its upper surface. The measurements
were performed after thorough drying with com-
pressed air, and a reference value from intact buc-
cal and accessible enamel surface. Polishing with
professional toothpaste was avoided because it
affects the fluorescence. Thereafter, the tapered tip
was moved along the proximal surfaces, slightly
tilted and rotated along its own axis to pick up the
area where the demineralisation was most
advanced. Three measurements were performed
between the incisal edges of two adjacent teeth and
papillas peak. The measuring site was the location
giving the highest recording, corresponding to the
deepest part of the demineralised area.
For interpretation of the results, the diagnostic
scale based on the examination of intact and altered
enamel previously performed in Bulgaria [10,11]
was used. It had involved the use of a clinical visu-
al study, DIAGNOdent and the histologic valida-
tion of the results (Table 1).
Table 1. Diagnostic scale of carious lesions
DIAGNO- Histologic Clinical
dent value validation diagnosis
0-3 No change Intact enamel
4-6 Early changes
on enamel D1a
surface
7-15 Changes in
outer half of D1b
enamel
15-20 Changes up to
enamel-dentine D2
junction
Above 21 Dentine caries D3
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OHDM - Vol. 10 - No. 3 - September, 2011
The measurements for the qualitative assess-
ment of enamel with the DIAGNOdent pen were
performed before and immediately after enamel
reduction, and then on the third and tenth days and
one month after enamel reduction. For 27 patients,
there was an additional measurement after nine
months.
Performing enamel reduction
After carrying out the diagnostic measurements and
planning the amount and location of the enamel
reduction on casts, this procedure was performed
clinically. If fixed appliances were present, the wire
was removed from the brackets in order to gain
access to the approximal surfaces. If necessary,
rubber separators or open-coil springs were placed
to create an opening between two adjacent teeth. If
the teeth were not separated, a diamond-coated
metal strip (Komet, Rock Hill, SC, USA) was used
to make the initial reduction. The size of the inter-
dental opening was equal to the thickness of the
strip, which was between 0.08 mm with extra-fine
grains (15 m), 0.10 mm with medium-fine coat
grains (30 m), and 0.13 mm with the roughest
grains (45 m).
Then, with the help of a double-coated perfo-
rated diamond separator (Komet) with a diameter
of 18 mm or 22 mm and diamond coat of 3 mm
wide and 0.15 mm thick, a reduction of a minimal
amount of enamel (0.10-0.25 mm) was made by
moving it along the axis of two adjacent teeth. In
teeth with triangular crown morphology, more
enamel was removed from the incisal edge of the
tooth and less from the middle and gingival thirds,
whereas in oval-shaped teeth more was removed
from the middle third, so that almost parallel
approximal surfaces were achieved.
Initially, minimal enamel reduction was per-
formed (range between 0.10-0.20 mm). An addi-
tional enamel reduction procedure was applied on
22 of the total 535 surfaces (up to 0.5 mm maximal-
ly) until final tooth alignment.
A diamond flame-shaped bur was used to pol-
ish and shape a final oval form to the entrance
between the approximal surfaces and the labial and
lingual surfaces.
The approximal surfaces were then polished
with a Komet perforated or non-perforated dia-
mond metal strip, with a rough, middle-fine, and
fine polish paper band and polishing discs (Sof-
Lex, 3M Espe, St Paul, MN, USA).
At every patient appointment, the amount of
enamel reduction at each of the six anterior teeth
was assessed. This was measured with a mechani-
cal thickness gauge which consisted of several
lamellae of different thickness: 0.05 mm, 0.10 mm,
0.15 mm, 0.20 mm, 0.25 mm, 0.30 mm, 0.40 mm,
0.50 mm, 0.60 mm, 0.70 mm, 0.80 mm, 0.90 mm
and 1 mm. It was perpendicular to the dental arch
and with an angle of 90 towards the labial surfaces
of two adjacent teeth. The gauge was inserted into
the interdental space without resistance and without
moving the two teeth apart.
After interdental enamel reduction and polish-
ing, with the help of a brush or a cotton pad, fluo-
ride-gel was applied to the dried stripped surfaces
(Duraphat, Colgate, Pharbil Waltrop GmbH,
Germany) (1 ml of the gel containing 50 mg NaF,
which is equal to 22.6 mg fluoride) until there was
a homogeneous layer on the tooth. Tooth surfaces
turned yellow, which was helpful for control of the
application. This gel can be applied to a tooth again
after three months, except in cases where some
hypersensitivity occurs on the tooth, in which case
it can be applied two or three times a week [10,11].
In order not to remove the gel, patients were
instructed not to consume hard food or drinks and
not to brush their teeth for four to six hours after
application. They were also recommended to brush
their teeth with a desensitising toothpaste
(Sensodyne; GlaxoSmithKline, Brentford, UK) with
higher fluoride content (calcium fluoride and NaF,
1400ppm) for three months after enamel reduction.
Statistical methods
The resulting data were entered into statistical soft-
ware (Statistical Package for Social Sciences,
Windows Version 15.0; SPSS Inc, Chicago, USA).
Fischers exact test was used for statistical analysis
of the research results and non-parametric
McNemars test for the categorised clinical scores.
The level of significance was set to 5%. Excel
Version 2003 (Microsoft Corporation, Redmond,
WA, USA) was used for the graphic design.
Results
The initial measurements with the DIAGNOdent
pen before enamel reduction were at a total of 535
surfaces; of these, 394 (73.6%) recorded values
between 0 and 3, 127 (23.7%) values between 4 and
6, and only 14 surfaces had values between 7 and
15, which showed that only in limited cases (2.7%)
were changes in the outer half of the enamel
observed (Table 2). Results after enamel reduction
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OHDM - Vol. 10 - No. 3 - September, 2011
and final polishing of the treated dental surfaces are
presented in Table 2 and Figure 1.
There was a statistically insignificant decrease
in the number of the dental surfaces with values
between 0 and 3, falling from 394 to 384. During
the investigation, only 10 out of 127 dental surfaces
(7.9%) with values of 4 to 6 (early outer surface
alteration) maintained the same value, whereas the
other 117 dental surfaces (92.1%), with an initial
value of 4 to 6, recorded values of intact enamel (0-
3), which showed a statistical decrease of the cases
with initial demineralisation.
It is important to note that 14 surfaces which
showed values of DIAGNOdent 7-15 before enam-
el reduction (initial changes on the outer enamel
layer) improved their status after the procedure, as
nine surfaces registered values of 0 to 3 and the
other five surfaces values of 4-6 (Table 2).
Three days after enamel reduction, 381 of 394
healthy enamel surfaces (value 0-3 before enamel
reduction) remained within this range but only 13
of them (3.3%) showed values 4-6 (i.e., initial
changes of enamel), which may be explained by the
deterioration of oral hygiene in these cases.
On the other hand, there was a significant
reduction in the number of surfaces that showed
values between 4 and 6 before enamel reduction;
that is, a decrease from 127 to 118. Three days after
enamel reduction, these already showed a normal
reaction (0-3) and only in nine cases (7%) did the
value remain at 4-6. It is of particular importance
that out of 14 surfaces (2.7% of total surfaces) with
initial changes in the outer enamel layer, three days
after stripping 12 (85.7%) registered values of 0-3
and only two (14.3%) registered values between 4-
6. On the day 3, damages in the outer half of the
enamel (7-15 values) were not found in any of the
three groups of surfaces.
The quality of the enamel was measured again
ten days after enamel reduction. The data are pre-
Table 2. Comparison of DIAGNOdent values before and after enamel reduction
Figure 1. Percentage distribution of dental surfaces by DIAGNOdent values before and after enamel reduction.
* Statistical significance P<0.05; ** Statistical significance P<0.01; *** Statistical significance P<0.001
Time of Before enamel reduction After enamel reduction
measurement
DIAGNOdent Number
values surfaces % 0-3 % 4-6 % 7-15 %
0-3 394 73.6% 384 97.5% 10 2.5% 0 0%
4-6 127* 23.7% 117 92.1% 10* 7.9% 0 0%
7-15 14** 2.7% 9 64.3% 5** 35.7% 0 0%
Total number
surfaces 535 100% 510 95.3% 25 4.7% 0 0%
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OHDM - Vol. 10 - No. 3 - September, 2011
sented in Table 4 and Figure 3. The results showed
a slight increase of surfaces which presented with
values of 0-3 before enamel reduction compared
with those recorded on day 3 (from 381 to 384) and
normalised surfaces that showed initial deminerali-
sation (4-6) from 118 to 121. Out of nine surfaces
with values 4-6 on the third day, three of them on
the tenth day were observed to have values equal to
intact enamel (0-3).
The comparison between the values of the sur-
faces before enamel reduction and one month after
the procedure are at Table 5 and Figure 4.
Table 3. Comparison of DIAGNOdent values before enamel reduction and 3 days later
* Statistical significance P<0.05; ** Statistical significance P<0.01; *** Statistical significance P<0.001
Time of Before enamel reduction 3rd day
measurement
DIAGNOdent Number
values surfaces % 0-3 % 4-6 % 7-15 %
0-3 394 73.6% 381 96.7% 13 3.3% 0 0%
4-6 127** 23.7% 118 92.9% 9** 7.1% 0 0%
7-15 14** 2.7% 12 85.7% 2 14.3% 0** 0%
Total number
surfaces 535 100% 511 95.5% 24 4.5% 0 0%
Table 4. Comparison of DIAGNOdent values before enamel reduction and 10 days later
* Statistical significance P<0.05; ** Statistical significance P<0.01; *** Statistical significance P<0.001
Time of Before enamel reduction 10th day
measurement
DIAGNOdent Number
values surfaces % 0-3 % 4-6 % 7-15 %
0-3 394 73.6% 384 97.4% 10 2.6% 0 0%
4-6 127** 23.7% 121 95.3% 6** 4.7% 0 0%
7-15 14** 2.7% 12 85.7% 2 14.3% 0** 0%
Total number
surfaces 535 100% 517 96.6% 18 3.4% 0 0%
Figure 2. Percentage distribution of dental surfaces by DIAGNOdent values before enamel reduction
and 3 days later.
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OHDM - Vol. 10 - No. 3 - September, 2011
Table 5. Comparison of DIAGNOdent values before enamel reduction and 1 month later
* Statistical significance P<0.05; ** Statistical significance P<0.01; *** Statistical significance P<0.001
Time of Before enamel reduction 1 month after enamel reduction
measurement
DIAGNOdent Number
values surfaces % 0-3 % 4-6 % 7-15 %
0-3 394 73.6% 383 97.2% 11 2.8% 0 0%
4-6 127 23.7% 118 92.9% 9 7.1% 0 0%
7-15 14** 2.7% 11 78.6% 3 21.4% 0** 0%
Total number
surfaces 535 100% 512 95.7% 23 4.3% 0 0%
Figure 3. Percentage distribution of dental surfaces by DIAGNOdent values before enamel reduction and
10 days later.
Figure 4. Percentage distribution of dental surfaces by DIAGNOdent values before enamel reduction
and 1 month later.
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OHDM - Vol. 10 - No. 3 - September, 2011
Figure 5. Percentage tracing of DIAGNOdent enamel status for 1 month after enamel reduction.
Figure 6. Longitudinal 9-month follow-up of enamel changes on 291 surfaces after enamel reduction.
Table 6. Longitudinal 9-month follow-up of enamel changes after enamel reduction
Time of
measurement Before After 3rd day 10th day 1 month 9 months after
DIAGNO enamel enamel enamel
values reduction reduction reduction
0-3 216 269 272 276 274 282
4-6 65 22 19 15 17 9
7-15 10 0 0 0 0 0
Total 291 291 291 291 291 291
Compared to the tenth day after enamel reduction,
five previously intact surfaces were observed with
values equal to initial enamel changes (4-6). This
can be attributed to deterioration of oral hygiene in
these patients.
A longitudinal nine-month follow-up study of
the results was carried out. It included only 27 of
the original sample of 53 patients. They were the
patients who managed to come to the additional
nine-month appointment. Two hundred and ninety-
one stripped surfaces of a total 535 were observed.
Data from these 27 patients are presented in Table
6 and Figure 6.
After nine months, only nine enamel surfaces
registered scores of 4-6. The rest all registered 0 to
3 (Table 6 and Figure 6). Five of these nine sur-
faces originally registered 0-3. Of the 65 surfaces
that originally registered values of 4-6, 61 gave val-
ues of 0-3 after nine months and only four surfaces
remained at values of 4-6 (initial enamel change).
All 10 surfaces that showed changes in the outer
half of enamel (value 7-15) before initial measure-
ments improved over the nine months and gave
intact enamel (values 0-3), which may be explained
by remineralising procedures and well-maintained
oral hygiene by the patients.
Discussion
As far as the authors are aware, this was the first in
vivo study that has been performed to investigate,
with the help of a laser fluorescence device
DIAGNOdent pen, the relationship between the
qualitative changes of enamel after enamel reduc-
tion, and to evaluate the remineralisation process
that occurs in enamel surfaces after enamel reduc-
tion has been performed.
Previous studies [31,34] have suggested that
DIAGNOdent can be used for detecting caries and
initial demineralisation on the occlusal or approxi-
mal tooth surfaces. Some of these studies [33,37]
have been in vitro and none of them has assessed in
vivo the quality of the enamel before and after
enamel reduction. There are no previously pub-
lished data or studies of approximal surfaces of
anterior teeth with DIAGNOdent in vivo in order to
evaluate enamel changes.
DIAGNOdent is known to be influenced by
plaque and calculus, saliva bacteria and body tem-
perature. Nevertheless, it is one of the most objec-
tive devices for qualitative enamel assessment. It
was therefore used in the current study.
Clinically, working with the DIAGNOdent pen
and recording the values was quick and easy to per-
form and was well accepted by the patients. The
study can be criticised for not dividing the results
by gender and the simplistic visual methods that
were used to diagnose initially intact or damaged
enamel. Control groups were not used in this study
because of the difficulty of having in a single
mouth one side with stripped surfaces and one side
without enamel reduction. It was unfortunate that
not all patients could be followed up for the period
of nine months. However, the resulting data have
provided a promising indication of the effect of
enamel reduction on intact or even initially dam-
aged enamel when this procedure is performed.
Two studies [38,39] have shown that enamel
reduction can increase the susceptibility of proxi-
mal enamel surfaces to demineralisation and lead to
greater plaque retention and increased risk of sec-
ondary caries because of residual furrows on the
enamel surface compared with non-treated enamel
surfaces [2,40-45].
Results immediately after enamel reduction
showed that in cases of initial reversible lesions in
the outer enamel surface, enamel reduction
removed the demineralised section of the enamel
and although generally less-mineralised enamel
remained on the surface, there remained a more
mineralised area [46,47]. Therefore, in these cases
it can be claimed that appropriately performed
enamel reduction has a positive effect on enamel.
On the third and tenth days after enamel reduction,
there was a slight but not statistically significant
increase in the number of surfaces that registered
values (0-3) and a decrease in the number of sur-
faces showing initial enamel changes (4-6).
Surfaces with values that equated to damage in the
outer half of the enamel were not found. The fol-
low-up study recordings taken after nine months
showed that 282 of 291 surfaces with initial
changes before enamel reduction could be consid-
ered as healthy after properly performed enamel
reduction.
The study indicated that performing enamel
reduction is appropriate for intact approximal tooth
surfaces or even in those with initial enamel dem-
ineralisation. Enamel reduction can be successfully
implemented in early carious lesions within the
outer half of the enamel. Such lesions demand more
intensive and periodical remineralisation by apply-
ing fluoride gel, if tooth sensitivity continues
longer. Systematic oral hygiene checks were car-
ried out after enamel reduction in order to motivate
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OHDM - Vol. 10 - No. 3 - September, 2011
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166
and follow-up the oral hygiene in patients with
stripped teeth. In a future study, it would be worth-
while to assess the connection between the oral
hygiene and the remineralisation after enamel
reduction, as well as its relation to tooth sensitivity.
Conclusions
The results of the current study indicate that:
The DIAGNOdent pen can be used for the
objective clinical assessment of the dental
enamel status before and after performing
interproximal enamel reduction.
Most (95.3%) of the stripped surfaces reg-
istered DIAGNOdent values of 0-3 (as
intact enamel) after interproximal enamel
reduction.
After reduction, surfaces with initial dem-
ineralisation registered values as intact
enamel.
Oral hygiene control and remineralisation
procedures are needed to maintain the
enamel status in a healthy range after inter-
proximal enamel reduction
The results from this study demonstrate that
with correct diagnosis, as well as selection of intact
or even slightly demineralised enamel surfaces,
successful implementation of enamel reduction
within enamel is possible. This technique, precise-
ly planned, correctly executed and followed by
remineralisation procedures, eliminates the risk of
enamel demineralisation.
Acknowledgements
This study received support through Research
Grant 2008 from the Medical University of Sofia.
Contribution of each author
PMK performed the clinical examinations and
measurements.
MDP tested DIAGNOdent pen and modified a
diagnostic scale for enamel histologic changes.
PMK and VYM planned the study and wrote the
paper.
Statement of conflict of interests
As far as the authors are aware, there is no conflict
of interests.
OHDM - Vol. 10 - No. 3 - September, 2011
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