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570
Angle Orthodontist, Vol 76, No 4, 2006
Original Article
Relapse Tendency after Orthodontic Correction of
Upper Front Teeth Retained with a Bonded Retainer
Sasan Naraghi
a
; Anders Andre´n
b
; Heidrun Kjellberg
c
; Bengt Olof Mohlin
d
ABSTRACT
Objective: To investigate the amount and pattern of relapse of maxillary front teeth previously
retained with a bonded retainer.
Materials and Methods: The study group consisted of 135 study casts from 45 patients. Re-
cordings from study models before treatment (T1), at debonding (T2), and 1 year after removal
of the retainer (T3) were present. All patients had been treated with fixed edgewise appliances.
The irregularity index (sum of contact point displacement [CPD]) and rotations of front teeth toward
the raphe line were calculated at T1, T2, and T3.
Results: The mean irregularity index at T1 was 10.1 (range 3.0–29.9, SD 5.4). At T2 it was 0.7
(range 0.0–2.1, SD 0.7), and at T3 it was 1.4 (range 0.0–5.1, SD 1.2). Fifty-five teeth in 42 patients
were corrected more than 208 between T1 and T2 (mean correction 31.48 range 20.0–61.7), and
mean relapse in this group was 7.38 (range 0.0–20.5). Regarding alignment of the maxillary front
teeth, the contact relationship between the laterals and centrals seems to be the most critical. A
significant positive correlation was found between the amount of correction of incisor rotation and
the magnitude of relapse but not between the amount of correction of CPD and the magnitude of
relapse. Eighty-four percent of the overcorrected CPDs returned to a desired position.
Conclusions: Minor or no relapse was noted at the 1-year follow-up. (
Angle Orthod
2005;76:
570–576.)
KEY WORDS: Retention; Rotation; Crowding; Irregularity; Incisors
INTRODUCTION
Morphologic stability is one important goal after or-
thodontic treatment, and from the patients point of
view, stability of the upper front teeth is of consider-
able importance.
1,2
Relapse, the tendency for teeth to
return toward their pretreatment positions, has been
the subject of many studies,
3–9
the long-term results
a
Consultant Orthodontist, The County Orthodontic Clinic in
Va¨xjo¨, Kronoberg, Sweden.
b
Consultant Orthodontist, The County Orthodontic Clinic in
Mariestad, Va¨stra Go¨taland, Sweden.
c
Associate Professor, Faculty of Odontology Orthodontics,
The Sahlgrenska Academy at Goteborg University, Goteborg,
Sweden.
d
Professor, Faculty of Odontology Orthodontics, The Sahl-
grenska Academy at Goteborg University, Orthodontics, Gote-
borg, Sweden.
Corresponding author: Dr. Sasan Naraghi, The County Or-
thodontic Clinic, Klostergatan 16 B, Va¨xjo¨, Kronoberg S-352 31,
Sweden (e-mail: sasan@telia.com)
Accepted: July 2005. Submitted: April 2005.
Q 2005 by The EH Angle Education and Research Foundation,
Inc.
reported from Seattle being the most extensive.
3,17
Be-
cause of type of malocclusion, treatment procedure,
cooperation during and after treatment, growth, etc,
5,7–9
variability in long-term treatment outcome is quite
common. Additional factors are type and duration of
retention.
10
There is some information in the literature
regarding maxillary irregularity after retention with a
maxillary Hawley retainer,
6,7,11,12
but many stud-
ies
8,9,10,12
do not specify the retention method in the
upper arch, the duration of retention, or the length of
the postretention period at the time of examination.
Bonded multistrand wire has been used as a meth-
od of retention for 30 years
13,14
and is now a reason-
ably reliable form of retention
15,16
in a short-term per-
spective. Bonded retainers appear to be accepted well
by patients and are relatively independent of patient
cooperation. The relapse tendency of the upper front
teeth after correction of contact point displacements
(CPDs) and rotations and after use of bonded retain-
ers has yet to be reported.
Surbeck et al
17
found that the pattern of pretreat-
ment rotational displacement of maxillary anterior
teeth had a tendency to repeat itself after retention.
571RETENTION AND STABILITY
Angle Orthodontist, Vol 76, No 4, 2006
TABLE 1. Distribution of Extraction and Nonextraction Treatments
Nonextraction 12
Four premolar extraction 14
Two upper premolar extraction 10
Other extracted teeth/agenesis 9
TABLE 2. Extension of Retainer
No. Patients
Eight teeth 22
Seven teeth 3
Six teeth 14
Five teeth 1
Four teeth 5
FIGURE 1. Duration of retention in months.
FIGURE 2. Irregularity index: the sum of five frontalcontactdisplace-
ments in millimeters (A 1 B 1 C 1 D 1 E).
However, relapse of CPD because of labial or lingual
position only was random relative to the pretreatment
positions. The authors also held that incomplete align-
ment during treatment was a risk factor for relapse and
suggested slight overcorrection during active treat-
ment of severely rotated teeth; however, they did not
specify the method of retention. Several questions
arise when studying the relapse tendency of the upper
front teeth after retention with a bonded retainer. For
instance, does overcorrection of rotations or labial/lin-
gual displacements retained with bonded retainer de-
crease the amount of relapse? Does overcorrection
result in teeth remaining in overcorrected positions?
How large is the relapse of rotated or displaced (or
both) maxillary front teeth after a period of bonded re-
tention?
Objectives of this study
• Study the amount of relapse of the maxillary front
teeth after retention with a bonded retainer;
• Investigate the pattern of relapse regarding type of
movement after correction of rotations and labial/lin-
gual displacements;
• Examine the effect of overcorrection of CPD in sta-
bility outcome;
• Analyze the influence of expansion of the intercanine
distance on stability outcome.
MATERIALS AND METHODS
The study group consisted of 45 patients treated
with fixed orthodontic edgewise appliances. The pa-
tients were selected from The County Orthodontic
Clinic in Mariestad, Sweden, when their upper bonded
retainer was removed. The wire used was 0.0195-inch
Wildcat (GAC International Inc., Central Islip, NY).
Their mean age at the 1-year follow-up was 18.8 years
(range 15.8–21.5). Extraction or nonextraction cases
with various diagnoses and whose upper arches were
retained with a bonded retainer only were included. All
six front permanent teeth had to be present before
treatment and presenting irregularity. Spaced denti-
tions in the upper front teeth and treatments started
as adults were excluded. Study models before treat-
ment (T1), after active treatment (T2), and 1 year out
of upper retention (T3) had to be available.
The extraction and nonextraction distribution and
number of patients is shown in Table 1, and the ex-
tension of the retainers in Table 2. The mean duration
of the retention period was 33 months (range 23–48
months) (Figure 1). Of 306 teeth with bonded retain-
ers, the bonding failed on six teeth in five patients (2%)
during the retention period. No wires fractured during
the retention period.
Method for studying CPD
Labiolingual displacements of the anatomic contact
points from the mesial of the right canine through to
the mesial of the left canine were measured with a
digital caliper on the casts from T1, T2, and T3, with
0.1 mm accuracy. CPDs less than 0.5 mm were
judged to be zero.
The irregularity index (Figure 2), ie, the sum of the
five CPDs (A 1 B 1 C 1 D 1 E), was calculated as
described by Little.
18
Method for studying rotations and
intercanine distance
An Agfa DuoScan F40 (Agfa-Gevaert N.V., Mortsel,
Belgium) scanner was used to scan the casts at 300
DPI (dots per inch) resolutions. All 45 3 3 casts were
scanned in 300 DPI and then placed on the upper third
part of the glass, with almost the same size of the
572 NARAGHI, ANDRE
´
N, KJELLBERG, MOHLIN
Angle Orthodontist, Vol 76, No 4, 2006
FIGURE 3. Teeth angles on right side to the raphe line and inter-
canine distance.
FIGURE 4. Contact point displacements before treatment (T1), after
treatment (T2), and 1 year after retention (T3).
scanned area. To avoid distortions, all front teeth were
optimally in contact with the glass surface of the scan-
ner. To measure rotation changes and intercanine dis-
tance, a computer program (Scion Image) was used
to mark points on the pictures of the scanned casts.
The rotations were measured as the angle between a
line through the mesial and distal points on the incisal
edge of the teeth and the raphe line. The intercanine
distance was measured between the cusp tips of the
upper canines (Figure 3).
Statistical analysis
Paired
t
-tests were applied to test differences in
CPD, rotations, and intercanine distance between T1,
T2, and T3. Pearson’s product-moment correlationtest
was applied to test correlations between CPD and ro-
tations at T1 and changes during treatment and the
follow-up period. The SAST v8.2 program (SAS Insti-
tute Inc, Cary, NC) was used for all statistical analysis.
For all statistical analyses, the statistical significance
level was set to 5%.
Measurement error
The reproducibility of the measurements for rota-
tions and intercanine distance was determined by dou-
ble measurements of 45 scanned models from 15 pa-
tients at T1, T2, and T3. The error of the method was
calculated using Dahlberg’s equation.
19
2
D
O
S 5
Î
x
2N
Where D is the difference between repeated measure-
ments and N is the number of measurements. The
errors were 3.18 for canines, 2.88 for laterals, and 2.48
for centrals. The error of measuring the intercanine
distance was 1.1 mm.
Double measurements of 60 models in 20 patients
were used to calculate the error of measuring CPD.
Using this procedure, the measuring error for CPD
was 0.14 mm.
RESULTS
Contact point discrepancies
Before treatment (T1).
The mean irregularity index
at T1 was 10.1 (range 3.0–29.9, SD 5.4). The largest
displacements were recorded between laterals and
centrals followed by the displacement betweenlaterals
and canines, whereas the smallest deviations were
found between the centrals (Figure 4).
After treatment (T2).
At T2, the mean irregularity in-
dex was 0.7 (range 0.0–2.1, SD 0.7). There was a
significant difference in the index between T1 and T2
(
P
, .0001). Forty-three contacts were overcorrected
(Figure 5a). When overcorrections were excludedfrom
the calculation, the mean irregularity index was 0.3.
Eighteen overcorrections were less than 0.5 mm (all
were nonmeasurable) and could only be detected at
close inspection.
After retention (T3).
The mean irregularity index at
T3 was 1.4 (range 0–5.1, SD 1.2), ie, 14% of the ir-
regularity at T1. There was a significant difference in
the index between T2 and T3 (
P
, .0001). Of the 225
CPDs from 45 patients, those with the largest CPD at
T1 (5–11 mm, n 5 17) had a mean CPD at T3 of 0.5
(range 0–1.8). The intermediary CPD at T1 (3.0–4.9
mm, n 5 33) had a mean CPD at T3 of 0.4 (range 0–
1.5). The smallest CPD at T1 (1–2.9 mm, n 5 97) had
a mean CPD at T3 of 0.3 (range 0–1.5). None of these
differences was statistically significant (
P
5 .733).
Sixteen contacts in 11 patients were displaced more
than 1 mm, 1 year after retention.
Four CPDs changed from T2 to T3 in the opposite
direction to their pretreatment positions.
Seven of 25 contacts remained overcorrected. Six
of these seven contacts were displaced because of
rotations and one because of buccolingual displace-
ment at T1.
Four overcorrected CPDs at T2 had relapsed de-
573RETENTION AND STABILITY
Angle Orthodontist, Vol 76, No 4, 2006
FIGURE 5. (a) Overcorrected contacts after treatment and 1 year after retention. (b) Patient JB: overcorrected contact between 22/23, no
rebound, overcorrection remains. (c) Patient EH: 22/21 overcorrected 0.5 mm and relapse of 1.5 mm.
spite overcorrection; three of these were because of
rotations recorded at T1 (Figure 5a–c).
Rotations
There was a significant correlation between the
amount of rotational change (for all six teeth) because
of treatment and relapse (
P
, .0001). However, when
looking at each tooth, group centrals (
P
, .0130) and
laterals (
P
, .0001) showed significant correlations
but not the canines (
P
5 .0622).
Totally, 55 teeth in 42 patients were corrected more
than 20.08 between T1 and T2 (mean correction 31.48,
range 20.0–61.7). Mean relapse in this group was 7.38
(range 0.0–20.5) (Figure 6). Of these 55 teeth, 18 re-
lapsed more than 108 (Table 3).
Intercanine distance
The intercanine distance in 31 patients did not
change during treatment. In 14 patients, the intercan-
ine distance was expanded equal to or more than 1.5
mm (range 1.5–6.4). Four of these 14 patients showed
a reduction of the intercanine width at T3 of 1 mm or
more (range 1.0–2.3). Patients in this small group
were not more irregular regarding CPDs and rotations
than the rest of the sample.
Fiberotomy
Three laterals and six centrals were subjected to cir-
cumferential supracrestal fiberotomy. This technique
resulted in a mean correction of 338 (27–41) and a
574 NARAGHI, ANDRE
´
N, KJELLBERG, MOHLIN
Angle Orthodontist, Vol 76, No 4, 2006
FIGURE 6. Patient A
˚
G: tooth 22 corrected 438; 22 relapse 20.58, highest rotational relapse.
TABLE 3. Teeth That Were Derotated More Than 20.08 (n 5 55)
n
x¯
Correction
in Degrees
x¯
Relapse
in Degrees % Relapse
Cuspids 13 28 6 21
Laterals 23 34.8 9 26
Centrals 19 26.3 6.5 25
relapse of 7.68. If the nine teeth subjected to fibero-
tomy were excluded from the group of 55 corrected
rotations, the 46 remaining teeth had a mean relapse
of 7.18.
DISCUSSION
This study has demonstrated that 89% of the pa-
tients had a score of less than 3 for the maxillary ir-
regularity index, 1 year out of retention. The change
from a mean irregularity index of 0.7 after treatment to
1.4 after retention can be regarded as a minor relapse
compared with the corrections achieved during treat-
ment. No correlations were observed between the se-
verity of pretreatment irregularity and the amount of
relapse.
Of 306 teeth with bonded retainers, there were a few
bonding failures (six teeth in five patients) during the
retention period. Bonding failures may occur in cases
when lower teeth interfere with the retainers. In this
study, most patients achieved a proper overbite with
almost no interferences. In cases with pointed lower
canines, the technicians were informed to position the
wire more cervically on the upper canine and on the
distal part of the upper lateral. In patients with short
upper clinical crowns, the wire was placed more cerv-
ically.
Difficulty in locating the raphe line equally on the
pretreatment, posttreatment, and postretention study
models is probably the main reason for the relatively
large measurement errors when measuring rotations.
By using fixed reference points such as implants, this
problem could have been easily avoided. Variation in
the quality of the plaster casts is another factor that
might have increased the error. Changes in archform,
which frequently occur during both the treatment and
posttreatment period, may have also influenced the
measurements. If the arch changes to a wider form,
the angular measurement will tend to increase, even
if no contact point discrepancy has occurred relative
to the dental arch. The position of the incisors in buc-
colingual direction gives different angles to the raphe
line, meaning that more proclined teeth give a smaller
angle and more retroclined teeth give a larger angle.
A computer-generated archform as a reference is a
method used by Surbeck et al.
17
Rotation of the inci-
sors relative to the dental arch was measured as the
angle between the line connecting the points repre-
senting the mesial and distal point angles and the line
connecting the projections of these points on the arch,
recorded as positive if mesially rotated and negative if
distally rotated. Surbeck et al
17
state that this method
indicates CPD and incisor rotations even in a group
selected for perfect alignment. This shows that a com-
puter-generated archform may not represent the ac-
tual dental arch.
Because the follow-up period was short, being only
1 year, the results are to be considered as short term.
Of course, we believe that 1-year postretention control
is short and not sufficient, but registrations 1-year
postretention were done within the routine treatment
program. A recall visit 1 year out of retention was, in
most cases, the patients’ last visit to the orthodontist.
However, small contact displacements 1 year after re-
tention may be potential starting points for increasing
irregularity. The failure rate of bonded retained teeth
(2%) is consistent with the findings of Zachrisson
15
and
must be considered acceptable, especially because
four of six loose retainer bonds in our study affected
premolars. Fortunately, none of the bond failures
caused any measurable relapse.
The contact relationship between laterals and cen-
trals showed the largest CPD at T1, which is in ac-
cordance with the earlier findings.
7
The mean irregu-
larity index after treatment was 0.7, including overcor-
rections that accounted for most of the displacements.
The irregularity 1 year after retention was 14% of the
value before treatment. In comparison with other stud-
575RETENTION AND STABILITY
Angle Orthodontist, Vol 76, No 4, 2006
ies
6,7,10,11
using Hawley retainers, our results seem to
be favorable; ie, less postretention changes were ob-
served in our study. However, the studies are very dif-
ficult to compare because of different follow-up peri-
ods. The severe displacements at T1 did not rebound
more than the medium CPD at T1. Four CPDs
changed from T2 to T3 in the opposite direction of the
expected relapse with some rotations involved. There-
fore, we cannot posit that only labiolingual displace-
ments relapsed at random to the pretreatment posi-
tions. Our data do not confirm the finding of Surbeck
et al
17
that rotations and labiolingual displacements
have different relapse patterns.
Regarding alignment of the maxillary anterior teeth,
the contact relationship between the lateral and central
seems to be most critical. The correction of a bodily
displaced tooth, often laterals, includes selective root
torque to minimize the relapse tendency. In patient EH
(Figure 5c), the torque of the left lateral was not quite
successful. During the postretention period, the crown
tended to upright over the root resulting in a small re-
lapse despite overcorrection.
The most severe rotations were found among the
laterals. The number of severely rotated laterals and
centrals were slightly higher than for the canines,
which confirm the trend reflected in the CPD mea-
surements (Figure 4). This finding, together with a
larger error of method when measuring canine rota-
tions, might be a plausible explanation for the lack of
significant correlations between rotational correction
and relapse of canines.
Only a few individuals exhibited an increased inter-
canine width during treatment. No obvious changes
could be recorded in the intercanine distance between
T2 and T3, which is in accordance with other studies.
6–
8,17
Because four subjects showed a decreased width,
no firm conclusions can be drawn from these findings.
Fiberotomy was performed on only nine incisors.
Their degree of relapse was not different from the re-
maining 46 teeth corrected more than 208. However,
because of the small number of teeth treated with fi-
berotomy, it is hard to draw any conclusions as to
whether fiberotomy has any influence on the relapse
tendency. Studies that used Hawley retainers
11,20
as
retention found less relapse in a group with fiberoto-
mies as compared with a group without fiberotomies.
Of the 25 measurable overcorrections at T2, 14 had
returned to zero CPD at T3. We do not know if the
four overcorrections that relapsed toward the original
position (T1) would have been of a different magnitude
without overcorrection, but it is unlikely that the influ-
ence of overcorrection was negative. The seven re-
maining overcorrections were so small (0.5–1.1 mm)
that they probably did not cause the patients any dis-
satisfaction. It can be concluded that overcorrections
should be small because there is a risk that some do
not rebound to zero CPD. It is uncertain how much the
result can be improved by overcorrection.
From a clinical point of view, only 11% of the pa-
tients had an irregularity index of more than 3 at the
follow-up. The patient with the largest index (5.1) had
a deviant growth pattern after treatment, which caused
an open bite and an asymmetric mandible, resulting in
instability. This could account for the relapse in this
specific case. A combined orthodontic and surgical
treatment approach is now planned for this patient.
CONCLUSIONS
• Minor or no relapse in short-term follow-up (1 year)
was noted in the maxillary front after correction of
irregularity and a 2- to 4-year period of bonded re-
tention.
• There was a significant positive correlation between
the amount of correction of incisor rotation and the
magnitude of relapse.
• No significant relation was found between the
amount of correction of CPD and magnitude of re-
lapse.
• There was no difference in the relapse pattern be-
tween rotational displacements and labiolingual dis-
placement.
• 84% of the overcorrected CPDs returned to a de-
sired position.
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