European Journal of Orthodontics 28 (2006) 561–566
doi:10.1093/ejo/cjl030
Advance Access publication 13 October 2006
© The Author 2006. Published by Oxford University Press on behalf of the European Orthodontic Society.
All rights reserved. For permissions, please email: journals.permissions@oxfordjournals.org.
Which orthodontic archwire sequence? A randomized
clinical trial
N. A. Mandall*, C. Lowe**, H. V. Worthington*, J. Sandler***, S. Derwent*,
M. Abdi-Oskouei* and S. Ward*
*School of Dentistry, University of Manchester, **Hightown Orthodontic Practice, Crewe, and ***Chesterfield
Hospital, Sheffield, UK
Introduction
The aim of this study was to evaluate three orthodontic
archwire sequences in terms of patient discomfort, root
resorption, and time to working archwire. This is important
because the aim is to reach the working archwire not only
efficiently but also in physiologically sound archwire steps
(Burstone and Koenig, 1974; Waters et al., 1975; Burstone,
1981; Rock and Wilson, 1988; Tidy, 1989; Waters, 1992).
However, a balance should be made between the potential
benefits of a more rapid progression to working wires and
risks such as root resorption (Remmington et al., 1989;
Linge and Linge, 1991) and patient discomfort (Ngan et al.,
1989; Wilson et al., 1989).
There is a lack of in vivo data to support the choice of
archwire sequence because of the difficulty in evaluating
intra-oral force levels. Rock and Wilson (1988) suggested
using clinical success factors as outcomes, including rate of
tooth movement, absence of iatrogenic damage, and patient
acceptance. The rate of tooth movement or time in initial
aligning archwires has been evaluated (O’Brien et al., 1990;
Jones and Chan, 1992; West et al., 1995). However, archwire
sequence past initial aligning wires has not been investigated
and thus provided the focus for this trial. The null hypothesis
tested was as follows:
There is no difference in (1) patient discomfort (2) root
resorption, and (3) time to working archwire between three
archwire sequences: A = 0.016-inch nickel titanium (NiTi),
0.018 × 0.025-inch NiTi, and 0.019 × 0.025-inch stainless
steel (SS); B = 0.016-inch NiTi, 0.016-inch SS, 0.020-inch
SS, and 0.019 × 0.025-inch SS; and C = 0.016 × 0.022inch copper (Cu) NiTi, 0.019 × 0.025-inch CuNiTi, and
0.019 × 0.025-inch SS.
Methods
Sample size calculation
Reuker (1979) reported a mean treatment time for the
straightwire appliance system of 1.8 years with a standard
deviation (SD) of 4 months. It was hypothesized in the
present investigation that if the time to reach the working
archwire were 3 months shorter for one archwire sequence,
with a SD of 4 months, this would be clinically significant
in terms of efficiency. When the sample size in each of
the three groups was 40, a one-way analysis of variance
(ANOVA) would have a 99 per cent power to detect, at the
0.05 level, a difference in means characterized by a variance
of means of 3 months assuming the common SD is 4 months.
This gave a total sample size for the trial of 120. One
hundred and fifty-four patients were registered to allow for
a drop-out rate of just over 20 per cent.
Ethical approval was obtained from the Central
Manchester Local Research Committee (No. CEN/00/185)
and written parent and child consent taken for patients at the
University Dental Hospital of Manchester, Hope Hospital
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SUMMARY The aim of this study was to compare three orthodontic archwire sequences. One hundred and
fifty-four 10- to 17-year-old patients were treated in three centres and randomly allocated to one of three
groups: A = 0.016-inch nickel titanium (NiTi), 0.018 × 0.025-inch NiTi, and 0.019 × 0.025-inch stainless steel
(SS); B = 0.016-inch NiTi, 0.016-inch SS, 0.020-inch SS, and 0.019 × 0.025-inch SS; and C = 0.016 × 0.022inch copper (Cu) NiTi, 0.019 × 0.025-inch CuNiTi, and 0.019 × 0.025-inch SS. At each archwire change
and for each arch, the patients completed discomfort scores on a seven-point Likert scale at 4 hours, 24
hours, 3 days, and 1 week. Time in days and the number of visits taken to reach a 0.019 × 0.025-inch SS
working archwires were calculated. A periapical radiograph of the upper left central incisor was taken at
the start of the treatment and after placement of the 0.019 × 0.025-inch SS wire so root resorption could
be assessed.
There were no statistically significant differences between archwire sequences A, B, or C for patient
discomfort (P > 0.05) or root resorption (P = 0.58). The number of visits required to reach the working
archwire was greater for sequence B than for A (P = 0.012) but this could not be explained by the increased
number of archwires used in sequence B.
562
Intervention and outcome measures
The planned intervention was one of three archwire
sequences used to reach the working archwire (0.019 ×
0.025-inch SS). All archwires were manufactured by Ormco
(Amersfoort, The Netherlands), including 35 degrees
thermoactive CuNiTi.
All archwires were left in place until they were passively
engaged in all bracket slots before proceeding to the next
archwire in the sequence. Since this was a ‘realistic’ study,
it was left to clinical judgement whether to use elastic or
wire ligatures and canine lacebacks. As a result of the
randomization process, variables such as method and extent
of ligation, lacebacks, push coil, and duration of time
between appointments were divided with equal probability
between groups A, B, and C.
Full or partial engagement of the initial aligning wires
was not thought to influence discomfort levels because of
the nature of the hysteresis curve exhibited by the NiTi
archwires, whereby an increased wire deflection does not
result in a proportional increase in force levels. However,
the clinicians were asked not to place a palatal arch,
quadhelix, or headgear at the same visit as the initial
archwire so that discomfort from the former appliances did
not influence archwire discomfort scores.
Three outcome measures were assessed: (1) patient
discomfort at each archwire change and total discomfort for
each archwire sequence, (2) root resorption (root length) of
an upper left central incisor (in mm), and (3) time to reach
upper and lower working archwire (0.019 × 0.025-inch SS)
in months, and also the number of visits.
The following baseline data were collected: age and
gender, operator level (staff or postgraduate student),
type of malocclusion, extraction or non-extraction
treatment, upper and lower labial segment crowding,
irregularity index (Little, 1975) for upper and lower labial
segments, and start of treatment periapical of the upper
left central incisor.
When the archwires were changed, the patients recorded
their discomfort on a seven-point Likert scale at 4 hours, 24
hours, 3 days, and 1 week for the upper and lower arches
separately (Ngan et al., 1989; Wilson et al., 1989). The
patients were given discomfort data sheets, as required, at
the end of their adjustment appointment and asked to return
them at the following visit.
The upper left central incisor was used as an indicator of
likely root resorption and root length measurements were
recorded by two authors (SD and MA-O) who were
previously calibrated to use dial callipers (Mitutoyo,
Andover, Hampshire, UK) accurate to a 10th of a millimetre.
An upper incisor was chosen because it has been suggested
that these are at most risk of root resorption (Remmington
et al., 1989). The length of the crown from the cementoenamel junction to the incisal tip was measured from a
periapical radiograph taken at the start of treatment (C1)
and after the working archwire was placed (C2). A
correction factor for enlargement between the start and
end-point radiograph was calculated as C1/C2. Apical root
resorption was measured as root length at the start of
treatment (R1) minus root length at the end of alignment
(R2) and multiplied by the correction factor (Linge and
Linge, 1991):
Apical root resorption = R1−R2×(C1/C2).
Labial segment crowding was assessed by one author
(NAM) by calculating the difference between the sum of
the mesio-distal widths of the incisors and canines and the
arch space available between the distal contact points of
the canines. The latter was measured by summing the
distance between the distal contact point of the canine and
the mesial contact point of the central incisor on both sides
of the arch. Labial segment irregularity was recorded
according to the irregularity index (Little, 1975). Intraexaminer reliability was assessed by remeasuring 20 cases
at least 1 week later.
At the end-point of the trial, when 0.019 × 0.025-inch SS
wire had been passively placed in both arches for at least 4
weeks, a second periapical radiograph of the upper left
central incisor was taken. The time taken and the number of
visits to reach the working archwire were recorded from the
patient notes.
At the end of the trial, the case notes were checked for
any other protocol violations i.e. designated archwire
sequence not being used, and the reasons for this were
recorded. Such patients were still included in the intention
to treat analysis. For some patients, 0.016 × 0.022-inch
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(Salford), and a specialist orthodontic practice (Crewe,
UK). Patients with pain from any other medical or dental
condition that may have affected their reported discomfort
scores were excluded. The inclusion criteria were <18 years,
upper and lower pre-adjusted edgewise appliance (0.22inch slot), and non-extraction or up to four premolar
extractions.
Patients reporting a history of trauma (crown fracture or
avulsion and re-implantation), central incisor root filling, or
pre-existing root resorption (identified as radiographic
blunting of the root apex of the upper left central incisor)
were not excluded, but these factors were taken into account
in the statistical analysis.
Randomization was carried out by throwing an
unweighted die where 1 and 2 = archwire sequence A, 3 and
4 = sequence B, and 5 and 6 = sequence C. A restricted
randomization was used in blocks of 12 to ensure equal
allocation of patients to the treatment groups. Random
allocation was concealed in thick opaque envelopes. Only
when the patient was registered was the next consecutive
envelope opened, ensuring that the clinician and patient
were blind to the treatment allocation until the patient was
registered in the trial.
N. A. MANDALL ET AL.
563
CLINICAL CHOICE OF ORTHODONTIC ARCHWIRES
CuNiTi was ineffective for severely rotated premolars.
Therefore, if 0.016 × 0.022-inch CuNiTi was ineffective
and had been in place >6 months, it was agreed to keep the
patient in the study but change the initial aligning wire to
0.016-inch NiTi.
Statistics
Summary statistics were calculated and the data checked
for normality. ANOVA was used to compare archwire
sequence groups for the main outcome measures. Intraexaminer reliability for the dial calliper measurement was
assessed using intra-class correlation coefficients (ICCs).
Systematic error was quantified by examination of the
difference and 95 per cent confidence intervals.
Results
Table 1 shows the number of patients in each group and the
reasons for any dropouts. There was no apparent systematic
error for any of the outcomes, as the differences between
means were very small and the 95 per cent confidence limits
narrow. ICC revealed high intra-examiner reliability for
Little’s index (0.99), labial segment crowding (0.96), and
root length (0.98).
The characteristics of the patients in each archwire
sequence group are summarized in Tables 2 and 3. Up to
one-third of patients had reported upper incisor trauma.
There were more females than males, which reflects the
uptake of orthodontic treatment, with the exception of
group A where 60.8 per cent of patients were male. The
distribution of the type of malocclusion and extraction/
non-extraction cases was similar between the archwire
sequence groups. ANOVA revealed no statistically
significant differences between archwire sequences
for labial segment crowding (P = 0.56) or Little’s index
(P = 0.46). An intention to treat statistical analysis was
carried out, whereby data for patients who did not receive
the correct allocated archwires were included in the
analysis (n = 4).
T-tests were used to evaluate whether operator experience
influenced any of the outcome variables. In summary,
reported discomfort at 24 hours (maximum discomfort) was
similar for postgraduate (n = 8) and staff (n = 2) patients
(P > 0.05) except for lower arch/sequence C where mean
discomfort was 3.3 for staff and 5.2 for postgraduates
(P = 0.015). Root resorption was not statistically significantly
different for staff or postgraduates (P = 0.41). Postgraduates
took a slightly longer time to reach the upper working
archwire only (P = 0.022) and more visits to reach upper
and lower working archwires (P < 0.05). Therefore, operator
experience was factored into the analysis for time and
number of months to working archwire.
Archwire sequence and patient discomfort
Mean discomfort scores at different time intervals for each
archwire sequence are shown in Table 4. For example, the
score at 4 hours for sequence A indicates the mean discomfort
experienced for the whole archwire sequence at 4 hours
(0.016-inch NiTi, 0.018 × 0.025-inch NiTi, and 0.019 ×
0.025-inch SS). ANOVA did not reveal any statistically
significant difference in reported discomfort between
archwire sequences A, B, or C (F ratio, P > 0.05). In
addition, there was no statistically significant difference
between the proportion of patients who returned/did not
return discomfort data in groups A, B, or C [chi-square
value 0.49, P = 0.79, 2 degrees of freedom (df)]. This
suggested that there was no evidence of bias towards
patients returning data as potentially they may have
experienced more discomfort.
Table 1 Trial profile.
Archwire sequence
Received standard
intervention
Protocol violations
Followed up
Withdrawn (total)
Reasons for withdrawal
Lost for follow-up
(failed appointments)
Patient requested
appliance removal
Obtained treatment
elsewhere
Operator stopped treatment
Repeated breakages
Poor oral hygiene
Completed trial
Sequence A
Sequence B
Sequence C
51
50
53
0
41
10
2*
44
6
2*
44
9
7
4
5
2
0
2
0
1
0
1
0
41
0
1
44
1
1
44
*Patients with protocol violations in sequence B and C were still included
in the analysis as an ‘intention to treat’ statistical analysis was used.
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Method error
Systematic error was reduced by ensuring that the examiner
was blind to the archwire allocation when labial segment
crowding, Little’s index, and root resorption were measured.
In addition, root resorption measurements were made
in a random order so that patients’ start and end-point
radiographs were not measured consecutively. It was not
possible to blind either the treating clinicians or the
examiner (SW) who recorded time to working archwire
from the patient notes.
Random error was reduced by taking measurements
twice and calculating a mean score for root lengths, labial
segment crowding, and Little’s index.
The influence of operator experience on
outcome variables
564
N. A. MANDALL ET AL.
Table 2 Descriptive statistics for each archwire sequence for the
patients enrolled in the trial.
Archwire sequence
Mean age in years (SD)
Gender (%)
Male
Female
A
B
C
13.8 (1.6)
14.4 (1.9)
14.4 (1.8)
13 (26.0)
37 (74.0)
18 (34.0)
35 (66.0)
14 (27.5)
37 (72.5)
6 (12.0)
44 (88.0)
11 (20.8)
42 (79.2)
Root filled upper left central incisor (%)
Yes
1 (2.0)
No
50 (98.0)
0 (0)
50 (100)
0 (0)
53 (100)
Pre-existing root resorption upper left central incisor (%)
Yes
1 (2.0)
0 (0)
No
50 (98)
50 (100)
0 (0)
53 (100)
History of incisor trauma (%)
Yes
No
Table 3 Occlusal descriptives according to archwire sequence
for patients enrolled in the trial.
Archwire sequence
A
B
C
Type of malocclusion (%)
Class I
Class II division 1
Class II division 2
Class III
13 (25.5)
18 (35.3)
12 (23.5)
8 (15.7)
13 (26.0)
18 (36.0)
9 (18.0)
10 (20.0)
19 (35.8)
17 (32.1)
6 (11.3)
11 (20.8)
Extraction/non-extraction (%)
Extraction
Non-extraction
32 (68.1)
15 (31.9)
35 (70.0)
15 (30.0)
37 (71.2)
15 (28.8)
Mean labial segment crowding [mm (SD)]
Upper
4.01 (4.3)
Lower
3.26 (2.63)
Little’s index [mm (SD)]
Upper
Lower
3.77 (4.71) 3.20 (4.26)
3.10 (2.36) 3.55 (2.66)
10.70 (6.10) 10.48 (6.54) 9.60 (6.40)
6.49 (5.05) 5.72 (4.31) 6.05 (4.75)
Archwire sequence and root resorption
Mean root resorption for archwire sequence A was 0.96 mm
(SD 1.0 mm), sequence B 1.39 mm (SD 1.8 mm), and
sequence C 1.19 mm (SD 1.5 mm). ANOVA revealed no
statistically significant difference between archwire
sequences, for upper left central incisor root resorption (F
ratio, P = 0.58). However, this should be interpreted with
caution as the SDs were large. There was also no statistically
significant difference between the proportion of patients
with/without root resorption data between archwire
sequences (chi-square value 5.0, P = 0.80, 2 df). Additionally,
reported history of incisor trauma was not associated with
increased root resorption (t-test: P = 0.59).
The mean time taken and the number of visits to reach 0.019
× 0.025-inch SS working archwire are shown in Tables 5
and 6. Operator experience was factored into the ANOVA
for this variable. Although there was a trend for sequence B
to take longer, there was no statistically significant difference
between archwire sequences for time taken (F ratio, P >
0.05). However, sequence B required statistically
significantly more visits, before the working archwire was
placed, compared with sequence A (F ratio, P = 0.007 for
upper arch and P < 0.001 for lower arch).
There was no statistically significant difference between
the proportion of patients with complete/incomplete data
for this variable (chi-square value 0.70, P = 0.71, 2 df).
Discussion
This trial showed that no archwire sequence tested was more
effective than another, in terms of reported patient discomfort
or upper incisor root resorption. However, clinicians may
choose a NiTi sequence with the aim of reducing the number
of visits to reach the working archwire. There are other
factors that influence the choice of archwire progression,
such as personal preference and cost, and these should be
considered equally alongside the clinical evidence
presented.
Importantly, the archwire sequences investigated do not
appear to cause unacceptable iatrogenic root resorption or
high levels of patient discomfort.
It is difficult to compare this data with the previous
literature as other archwire trials evaluated initial aligning
wires only (O’Brien et al., 1990; Jones and Chan, 1992;
West et al., 1995). However, it would seem that an efficient
archwire sequence of 0.016-inch NiTi, 0.018 × 0.025-inch
NiTi, and 0.019 × 0.025-inch SS suggested by Tidy (1989)
is now clinically supported.
When separate outcomes are considered, root resorption
in this study was similar to that reported by Linge and Linge
(1991) of 1.54 mm. Additionally, when clinically significant
root loss is considered as >2.5 mm, the results are also
comparable with Linge and Linge (1991) reporting 16.5 per
cent of patients affected and this trial 18.1 per cent. It may
be that the present results underestimate root resorption as
the data only record up to the passive placement of working
archwires and not to the end of treatment. In addition,
although baseline risk variables such as the presence of a
root filling were recorded, these were small in number and
statistical analysis was not carried out.
A previous trial by Jones and Chan (1992) showed no
statistically significant differences in discomfort between
0.015-inch twistflex and 0.014-inch Japanese NiTi. Although
different archwires and sequences of archwire were
compared, the results of this trial support their data in that
patient discomfort was not influenced by the type of archwire.
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31 (60.8)
20 (39.2)
Archwire sequence and time to 0.019 × 0.025-inch
SS working archwire
565
CLINICAL CHOICE OF ORTHODONTIC ARCHWIRES
Table 4 Mean discomfort scores over time for each archwire sequence*.
Sequence
Mean discomfort
at 4 hours (SD)
Mean discomfort at
24 hours (SD)
Mean discomfort
at 3 days (SD)
Mean discomfort
at 1 week (SD)
Lower
Upper
Lower
Upper
Lower
Upper
Lower
Upper
A
2.9 (1.8)
3.5 (2.1)
2.9 (1.6)
3.3 (1.7)
1.9 (1.1)
2.2 (1.8)
1.2 (0.4)
1.3 (0.9)
B
3.8 (1.7)
3.9 (2.0)
4.2 (1.8)
4.0 (1.8)
2.3 (1.2)
2.3 (1.0)
1.5 (0.9)
1.4 (0.6)
C
3.6 (1.6)
3.3 (1.7)
4.0 (1.6)
3.6 (1.5)
2.7 (1.1)
2.5 (1.3)
1.5 (0.4)
1.7 (0.8)
Likert scale 1–7: 1 = no discomfort at all, 7 = significant discomfort.
*No statistically significant difference between archwire sequences (ANOVA; F ratio, P > 0.05).
Table 7 Number of patients with complete data for main
outcomes.
Archwire
sequence
Mean time taken to
placement of working
archwire in months (SD)
Mean number of visits
to placement of working
archwire (SD)
Outcome
Archwire
sequence
Number or
range of
subjects with
complete data
Number of
subjects
registered
in trial
Number of
subjects
completing
trial
Lower
Upper
6.8 (2.5)
6.7 (3.5)
5.7 (2.1)
5.4 (2.1)
Pain
41
44
44
9.3 (4.4)
7.9 (3.5)
7.5 (1.9)
7.1 (2.6)
Root
resorption
Range 15–22
Range 11–16
Range 15–16
28
29
37
51
50
53
Lower
Upper
A
B
C
A
B
C
Lower
Upper
8.3 (4.2)
7.1 (3.4)
6.4 (2.2)
5.9 (2.8)
Time/months to working archwire
Upper
A
41
B
41
C
39
Lower
A
35
B
40
C
34
A
B
C
Table 6 ANOVA (Bonferroni correction) comparing the
number of visits to placement of working archwire.
Dependent Archwire Mean
Standard P value 95% confidence
variable
sequence difference error
interval
Numbers in archwire groups are based on an ‘intention to treat analysis’
where patients not receiving the allocated treatment are still included in
the statistical analysis. The number of patients remaining in the trial, in
each group, is included in the table for reference.
Number
of visits
to upper
working
wire
A
B
B
C
C
−1.6
−0.5
1.1
0.5
0.5
0.5
0.007
1.00
0.10
−2.9 to −0.4
−1.8 to 0.8
−0.15 to 2.4
Missing data
Number
of visits
to lower
working
wire
A
B
B
C
C
−1.8
−0.7
1.1
0.4
0.5
0.4
<0.001
0.34
0.06
−3.0 to −0.7
−1.8 to 0.4
−0.02 to 2.1
As this study did not find any clinical factors that may
influence the choice of archwire, consideration may be
given to cost. It is also clinically important to note that two
patients receiving sequence C had severe premolar rotations
where 0.016 × 0.022-inch CuNiTi was ineffective. This
was because it could not be tied in adequately due to a
very short interbracket span. It may therefore be more
advantageous to use another aligning archwire in these
instances.
There was some missing data in this trial mostly because of
patients not returning their discomfort scores, inadequate or
illegible information in the notes, and radiographs not showing
the root apex of the upper incisor. Table 7 shows the number
of patients with complete data for each outcome. However,
analysis suggested that there was no statistically significant
difference, and therefore no bias, between the proportion of
patients for whom data were or were not available.
It is possible that patients not returning discomfort sheets
experienced less pain than those who returned data. However,
as the reported discomfort was low, non-returners experiencing
less discomfort are likely to be clinically insignificant.
Conclusions
The archwire sequences investigated were not statistically
significantly different in terms of patient discomfort and
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Table 5 Mean time taken to placement of 0.019 × 0.025-inch SS
working archwire according to archwire sequence.
566
upper incisor root resorption. However, clinicians may
choose sequence A to minimize the number of visits to the
working archwire.
Address for correspondence
Dr N. A. Mandall
School of Dentistry
University of Manchester
Higher Cambridge Street
Manchester M15 6FH
UK
E-mail: nicola.a.mandall@manchester.ac.uk
Acknowledgements
References
Burstone C J 1981 Variable modulus orthodontics. American Journal of
Orthodontics 80: 1–16
Burstone C J, Koenig H A 1974 Force systems in an ideal arch. American
Journal of Orthodontics 65: 270–289
View publication stats
Jones M, Chan C 1992 The pain and discomfort experienced during
orthodontic treatment: a randomised controlled clinical trial of two
initial aligning archwires. American Journal of Orthodontics and
Dentofacial Orthopedics 102: 373–381
Linge L, Linge B O 1991 Patients characteristics and treatment variables
associated with apical root resorption during orthodontic treatment.
American Journal of Orthodontics and Dentofacial Orthopedics 99:
35–43
Little R 1975 The irregularity index: a quantitative score of mandibular
anterior alignment. American Journal of Orthodontics 68: 554–563
Ngan P, Kess B, Wilson S 1989 Perception of discomfort by patients
undergoing orthodontic treatment. American Journal of Orthodontics
and Dentofacial Orthopedics 96: 47–53
O’Brien K D, Lewis D, Shaw W, Combe E 1990 A clinical trial of aligning
archwires. European Journal of Orthodontics 12: 380–384
Remmington D N, Joondeph D R, Årtun J, Riedel R A, Chapko K 1989
Long term evaluation of root resorption occurring during orthodontic
treatment. American Journal of Orthodontics and Dentofacial
Orthopedics 96: 43–46
Reuker H A J 1979 Straight wire versus conventional full edgewise. Thesis,
University of Nijmegen
Rock W P, Wilson H J 1988 Forces exerted by orthodontic aligning
archwires. British Journal of Orthodontics 15: 255–259
Tidy D C 1989 New wires for old. Dental Update May: 137–145
Waters N E 1992 A rationale for selection of orthodontic archwires.
European Journal of Orthodontics 14: 240–245
Waters N E, Stephens C D, Houston W J B 1975 Physical characteristics of
orthodontic wires and archwires Part 2. British Journal of Orthodontics
2: 73–78
West A E, Jones M L, Newcombe R G 1995 Multiflex versus superelastic:
a randomised clinical trial of the tooth alignment ability of initial
archwires. American Journal of Orthodontics and Dentofacial
Orthopedics 108: 464–471
Wilson S, Ngan P, Kess B 1989 Time course of the discomfort in
young patients undergoing orthodontic treatment. Pediatric Dentistry
11: 107–110
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This study was supported by the British Orthodontic Society
Research/Audit Fund. Many thanks go to the following
specialised registrars who registered and treated a number
of patients for this trial and who also collected patient
discomfort data and periapical radiographs: L. Harvey, B.
Doherty, N. Manning, B. Kiptanui, K. Ioannou, M. Heanue,
J. Miller, A.-M. Isaac, S. Vine, and S. Deacon, School of
Dentistry, University of Manchester, UK.
N. A. MANDALL ET AL.