Effects on the dental arch form using a /certified fixed orthodontic courses by Indian dental academy

Effects on the Dental Arch Form
Using a Preadjusted Appliance
with
Premolar Extraction in Class I
Crowding
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

 In the cases of malocclusion with anterior crowding
premolar extractions are often indicated.
 Studies which have been done earlier show that the
dental arch dimensions before and after treatment were
maintained, while morphological changes were few in
the lower dental arch and the area of the upper anterior
teeth increased.

 There is no report on the effects of premolar extraction
on positional changes of the anterior teeth and dental
arch form with use of a preadjusted appliance.
 A preadjusted appliance uses a preformed wire to
perform treatment with sliding mechanics; thus, it is
considered important to describe its effects on the dental
arch form.

Objective
 The aim of this study was to determine effects of
treatment with a preadjusted appliance after extraction
of premolars on the positional relationships of the upper
and lower anterior teeth, as well as the dental arch form
in patients with Class I crowding.

Materials and methods
 The subjects were 26 patients with Class I crowding
(20.17 SD 12.15 years ) who under went treatment
using a preadjusted appliance (MBT system, 0.022
slot) and attained a favorable occlusion.

 They were divided into the nonextraction (n 10,
25.66 SD 17.0 years) and extraction (n 16, 16.75 SD
6.3 years) groups. The inclusion criteria were as follows:
 Skeletal structure rated as Skeletal I and demonstrating
 Angle Class I malocclusion.
 No abnormality in the dental crown morphology.
 No restorative materials or occlusal wear that could
have an effect on the measurements.
 No temporomandibular joint derangement.
 Patients who had not undergone lateral expansion or
distal movement of the molars.

 Cast models and lateral cephalometric radiographs
before and after treatment were used as study
materials. For measuring the three-dimensional
coordinates of the FA point of each tooth, a three-
dimensional coordinate measuring device was used.
 The three-dimensional coordinate values were obtained
according to Otani’s method,then projected to the
reference plane and converted into two-dimensional
coordinates.

 The dental arch configuration was expressed by a
quartic polynominal expression, y =ax2 + bx4, using
Mathematica 5.1 (Wolfram Research, Champaign, Ill) to
calculate the log F value (F a3/b) from the coefficients
of the quadratic and quartic terms, which represented
the dental arch configuration.
 A dental arch configuration with a smaller log F value
indicated a squared type, while that with a larger log F
value indicated a tapered type.

 For analysis of lateral
cephalometric
radiographs, SNA, SNB,
facial angle, and
mandibular plane were
measured as well as U1-
FH, L1-Mand, U1-APo,
and L1-APo

 The maximum width of
the crown, anterior and
posterior lengths and
widths of the dental arch,
and archlength
discrepancy between the
upper and lower arch
were determined using
cast models prepared at
the time of the first
examination

 Each item was measured three times by the same
examiner using a digital micrometer caliper and a model
measuring instrument .To determine the mean of the
three measurements, the mean and standard deviation
were calculated for each of the subjects in the extraction
and nonextraction groups

Statistical Analysis
 The log F values for the extraction and nonextraction
groups were compared using a Mann-Whitney U test,
while those before and after treatment were compared
using a Wilcoxon signed-ranks test
 For cephalometric analysis, radiographs obtained before
and after treatment were compared between the
extraction and nonextraction groups.

 For comparisons between groups, an unpaired t-test was
used, while a paired ttest was used to compare
radiographs obtained before and after treatment in each
group
 For model analysis, comparisons were made between
the extraction and nonextraction groups using an
unpaired t-test

Protocol for Preadjusted Appliance Technique
 The subjects examined in the present study were treated
using a preadjusted appliance (0.022 0.028 inch slot,
MBT set up) according to the following procedure. The
bracket height was set using the Mc- Laughlin and
Bennett method for performing indirect bonding.
 The arch form (tapered, ovoid, square) was selected in
accordance with the dental arch form, which was
determined at the time of the first examination.

 After completing leveling and alignment of the lateral
teeth using a 0.016-inch round heat-activated Ni-Ti wire
and a 0.019 *0.025 inch heat-activated Ni- Ti wire, a
0.019 * 0.025 inch stainless steel wire was attached for
performing distal movement of the canine, followed by
leveling and alignment of the incisor

Results
dental arch configuration
 For the upper dental arch configuration, no statistically
significant differences were observed before treatment
between the extraction and nonextraction groups
 for the upper dental arch form after treatment, the log F
values of the extraction group were significantly larger
(P >0.05), as the median was -0.33 and interquartile
range was 2.29, compared with -2.76 and 3.07,
respectively, for the nonextraction group

 In contrast, no statistically significant difference was
observed for the lower dental arch configuration before
and after treatment or between the extraction and
nonextraction groups

Analysis of cephalometric radiology
 the extraction and nonextraction groups before
treatment demonstrated that the mean U1- APo of the
extraction group (9.71 mm) was significantly larger than
that of the nonextraction group
 However, no statistically significant differences were
observed for other measurements obtained using the
skeletal and dental measurements.

 As for the dental arch configuration after treatment, the
mean L1-APo of the extraction group (4.40 mm) was
significantly smaller than that of the nonextraction group
(6.56 mm) (P < .01).
However, no statistically significant differences were
observed for the other measurements.
 When the quantity of changes before and after
treatment were compared, a statistically significant
difference was observed between the extraction and
nonextraction groups for U1-APo, which was decreased
by 1.31 mm in the extraction group and increased by
1.43 mm in the nonextraction group

Analysis of cast models
 comparisons of the cast models before treatment
between the extraction and nonextraction groups
revealed statistically significant differences in the upper
posterior width (UPW) and lower posterior width (LPW).
 The intermolar widths of the upper and lower arches of
the extraction group were smaller

 Comparisons of the models after treatment
revealed statistically significant differences in
UPW, LPW, upper posterior length (UPL), and
lower posterior length (LPL) between the
groups. Also, the intermolar width and length of
the upper and lower arches were smaller in the
extraction group
 In the extraction group, comparisons of the
models before and after treatment revealed a
significant difference in UPW, while the
intermolar width of the upper arch was
decreased.

 Statistically significant differences were observed for
upper arch length (UAL) and lower arch length (LAL)
before and after treatment, while the upper and lower
anterior lengths were increased.
 Statistically significant differences were also observed for
UPL and LPL; the UPL and LPL were decreased.
 In the nonextraction group, comparisons of the models
before and after treatment revealed significant
differences in UAL and UPL, while the upper anterior and
posterior lengths were increased.

 As for maximum crown width, the extraction group
showed significantly greater widths for all teeth except
the second molar in the upper arch. In the lower arch,
the width of the canine, as well as the first and second
premolars, was significantly greater

 In addition, the arch length discrepancy (ALD) at the
time of the first examination in the extraction group was
significantly greater for both the upper (8.16 mm) and
lower arches (6.54 mm) compared with those (1.29 mm
and 1.82 mm, respectively) in the nonextraction group

Discussion
 In the present study of Class I crowding patients, no
statistically significant differences were observed for the
configuration of the upper and lower arches at the time
of the first examination between the extraction and
nonextraction groups. These results suggest that the
dental arch form might be determined irrespective of the
amount of discrepancy.

 The dental arch form for the lower arch between
Japanese and Indian females with normal occlusion was
studied by Ukere et al, they reported that Japanese
females had a smaller and more squared dental arch
form, and showed more considerable variation than the
Indian subjects
 In the present study, the log F value for the upper
dental arch was significantly increased from -1.35 before
treatment to -0.33 after treatment in the extraction
group. Since the log F value of the extraction group after
treatment was larger than that of the nonextraction
group (-2.76), the dental arch demonstrated a tapered
pattern.

 In the nonextraction group, no statistically significant
differences in log F values were observed for the upper
and lower arch between the groups before and after
treatment, indicating no changes in the dental arch form
 Hnat et al reported, the dental arch form might be
compensated by an increase in dental arch length.
Accordingly, it can be considered that a decline in
number of teeth might produce a tapered pattern.

 Heiser et al studied the dental arch form using a three-
dimensional methodwith extraction and nonextraction
groups and reported that the anterior length of the
upper dental arch was increased as a result of
extraction, while the area of the anterior teeth was
increased in both groups
 for the subjects in the present study, the width was
greater for all teeth, excluding the upper second molar,
in the extraction group than in the nonextractrion group.

 In addition, the widths of the canine and first and
second premolars were greater in the lower arch.
Accordingly, it was considered that crowding might be
produced by the width of the crown.
 Shigenobu et al speculated that ALD might be important
for a symmetrical crowding pattern of the anterior teeth.
 It was considered that tapering of the upper dental arch
in the present extraction group, which showed a large
ALD value, might have resulted from an increase in
anterior arch length to resolve crowding of the anterior
teeth produced by a large amount of tooth width

 BeGole et al suggested that intermolar width was likely
to be increased by nonextraction treatment, and
Weinberg and Sadowsky reported that the dental
arch expanded as a whole because of the performance
of nonextraction therapy.
In the present study, the length increased in the
extraction group, whereas the intercanine and intermolar
widths did not.

 As for the dynamic state of the upper and lower anterior
teeth, U1-APO was significantly reduced after treatment
in the extraction group, which demonstrated posterior
movement of the upper anterior teeth. Because U1-FH
did not show any changes, it was considered that the
teeth might have moved in a posterior direction by
sliding mechanics, while the torque of the upper anterior
teeth was kept and controlled properly
 This result also suggested that a torque of -17* and
angulation of 4* incorporated to the bracket for the
upper central incisor would function effectively

 For the inclination of the lower anterior teeth, no
significant difference was observed between before and
after treatment. The lower incisor moved toward the
posterior direction after treatment in the extraction
group and toward the anterior direction in the
nonextraction group. Nevertheless, a torque of -6* and
angulation of 0* incorporated to the bracket for the
lower incisor might be effective

 Further, space remained after improvement of anterior
teeth crowding, which suggested that the space was
closed by mesial movement of the molars, as the
intermolar width and anterior length of the dental arch
were reduced
 One of the out come of this study is that the sum of
tooth widths of teeth anterior of the canine is greatly
involved in determining the dental arch form.

CONCLUSION
 It is necessary to select an arch form that assumes a
possible tapered pattern of the upper dental arch after
extraction treatment in patients with Class I crowding

Wolfgang Heiser,
Andreas Niederwanger,
Beatrix Bancher,
Gabriele Bittermann,
Nikolaus Neunteufel,
Siegfried Kulmer
AJODO;2004;126
Three-dimensional dental arch and
palatal form changes after
extraction and
nonextractiontreatment.
Part 1. Arch length

 Most investigators believe that the success of
orthodontic treatment is judged by the long term
stability of the results. Treatment decisions are strongly
influenced by this thinking. The “extraction versus
nonextraction” debate is almost as old as the specialty of
orthodontics.
 Today, most orthodontists find themselves some where
in the middle, treating some patients with extractions
and some without.
 Karl Popper said that one of the biggest mistakes a
scientist can make is to always try to prove his own
thesis rather than seeking arguments that disprove it.

OBJECTIVE
 The purpose of this study was to investigate changes in
arch length, and irregularity index in patients treated
with and without premolar extractions

MATERIAL AND METHODS
 All patients had been treated in the private orthodontic
practice of the first author . The only criterion for
inclusion was good occlusion at bracket removal.
 Neither cephalometric characteristics nor postretention
occlusion was considered in sample selection. All
patients wore removable retainers; no fixed retainers
were used. The groups were formed before the follow-
up examination. Records were collected at 4 points:
pretreatment, bracket removal, end of retention, and
follow-up.

 The nonextraction group consisted originally of 25 Class
II patients (19 girls, 6 boys; average age, 11 years 4
months) who were treated between 1981 and 1991 with
fixed appliances (straightwire) without premolar
extractions.
The follow-up examination was carried out 6.3 years out
of retention. Twenty-two patients (17 women, 5 men;
average age, 20 years 7 months) returned for the follow-
up examination.
The mean irregularity index was 5.1 before orthodontic
treatment. The average active treatment time was 1
year 9 months; the average retention period was 1 year
3 months.

 The extraction group consisted originally of 24 patients
(18 girls, 6 boys; average age, 13 years 7 months) who
were treated between 1981 and 1991 with fixed
appliances (straightwire) and premolar (first or second)
extractions.
Twenty patients (16 women, 4 men; average age, 21
years 10 months) were examined at follow-up. The
mean irregularity index was 5.8 before orthodontic
treatment

 The average active treatment time was 1 year 9 months,
and the average retention period was 1 year 10 months.
The follow-up examination was carried out 4 years 8
months out of retention

 The complete treatment time for the nonextraction
group was 3 years; this was considerably shorter than
the treatment time for the extraction group—3 years 7
months.
 The average active treatment time was 1 year 9 months,
and the average retention period was 1 year 10 months.
The follow-up examination was carried out 4 years 8
months out of retention.

 The groups’ irregularity index values differed, although
this difference was not statistically significant. The mean
irregularity index values at the end of retention and at
follow-up were almost identical for both patient groups

 Accurate alginate mandibular and maxillary impressions
were taken for each patient at pretreatment, bracket
removal, the end of retention, and follow-up. The
impressions were poured in stone, and the maxillary
model was provided with a split-cast
 With the aid of an anatomic face-bow, the maxillary
model was mounted skull-related onto a semi-adjustable
SAM 2 articulator . Then the mandibular model was
mounted joint-related to the maxillary model according
to a central wax record.

System of coordinates
 Casts mounted in a SAM 2 articulator can be
transferred exactly to the 3-dimensional (3D)
digitizer.
 The 3D digitizer has a measuring pin that is
connected to the electronic precision gauge and
moves freely in all 3 planes of space.
 The digital signals of each measured point were
calculated as the x, y, and z coordinates by
means of custom software

 Missing points could be entered as such into the
computer. If a second molar was missing, the area up to
the first molars was calculated. If deciduous molars were
still present, their mesiobuccal and mesiolingual cusps
were digitized.

 Arch length was defined
as the sum of the
distances of the various
digitized points around
the arch
 The arch lengths of the
maxilla (upper length,
UL) were measured at
the following points—
 UL 3
 UL4
 UL5

 The arch lengths of the
mandible (lower length,
LL) were measured at the
following points—
 LL4
 LL5

Error study
 To assess measurement precision and reliability, 5
models were randomly selected. They were mounted on
the 3D digitizer and measured 3 times

Data analysis
 The 2 patient groups (nonextraction and extraction)
were compared by independent t test to identify
statistically significant differences between pretreatment,
bracket removal, end of retention, and follow-up (t test
for independent samples).
 Changes between pretreatment, bracket removal, end of
retention, and follow-up within the same group were
analyzed by paired t test (t test for dependent samples).
Statistical significance was determined at P < .05, P
<.01, and P < .001

RESULT
Arch length
 The nonextraction group had a statistically significant
increase (P < .05) in UL3 of 2.06 mm and in UL4 of 3.27
mm between pretreatment and bracket removal. This
was probably the effect of treatment.
 In the nonextraction group, UL3 and UL4 rebounded
(decreased) slightly from bracket removal to end of
retention; this was significant only for UL3 (P <.05).
 From end of retention to follow-up, UL3 and UL4
behaved contrarily: UL3 increased slightly (not
significantly), whereas UL4 decreased significantly (P <
.001) . UL5 lost length slightly from every evaluation
period to the next.

 Between pretreatment and followup, UL3 increased 1.5
mm, UL4 remained almost stable (0.06 mm), and UL5
decreased 1.45 mm.
 In the extraction group, statically significant decreases
(P .001) were found for UL3, UL4, and UL5 between
pretreatment and bracket removal as the treatment
result of premolar extraction.

 All the other changes in UL3, UL4, and UL5 were
nonsignificant, with the exception of the decrease in UL4
(P< .01) from the end of retention to follow-up.
 Comparing the nonextraction and extraction groups,
UL3, UL4, LL4, and LL5 showed almost identical changes
between bracket removal and end of retention.
 In the nonextraction group, LL4 increased from
pretreatment to bracket removal, but the increase
(0.59mm) was not significant. Arch length continued to
decrease to follow-up.

 The decrease of 1.38 mm from end of retention to
follow-up was statistically significant (P <.05). All
gained arch length was lost between bracket removal
and end of retention, resulting in a net decrease from
pretreatment and follow-up

 LL5 decreased over all the observation periods in both
patient groups. For the nonextraction group, the loss
was significant (P< .001) only between bracket removal
and end of retention.
For LL4 and LL5, the extraction group showed a highly
significant decrease from pretreatment to bracket
removal (P < .001); this was the consequence of
premolar extraction. Both arch lengths decreased further
until follow-up.
Although the losses were significant from bracket removal
to end of retention (P< .01 and P <.001), they were
not significant between end of retention and follow-up.

DISCUSSION
Arch length
 For nonextraction patients, Sadowsky et al found
maxillary arch lengths were unchanged during and after
treatment. Bishara et al and Glenn et al demonstrated a
postretention decrease in arch length. These results
contrast with the findings in this study of a net increase
in the maxillary arch length UL3 of 1.62 mm between
pretreatment and follow-up for the nonextraction group.

 La Cruz et al took almost the same measuring points
used in this study and copied them to the occlusal plane
to get a 2-dimensional (2D) picture; in the present
study, the 3D changes could be calculated. This means
that changes in the curve of Spee have influenced the
length measurements. Present study findings contrast
with the decrease in arch length found in that study.

 Sadowsky et al found that mandibular arch length was
unchanged during treatment; we detected increases in
nboth mandibular and maxillary arch length between
pretreatment and bracket removal for the nonextraction
group
 Sadowsky et al and Glenn et al,studying nonextraction
groups, found that mandibular arch length did not
increase significantly during treatment but showed
significant postretention reductions. These findings for
the mandibular arch correspond to present studywww.indiandentalacademy.com

 For the extraction group, our finding of mandibular arch-
length reduction agreed with Little et al and Bishara et al
 On the other hand, Little et al and Herberger
demonstrated that arch-length decrease is accompanied
by mandibular incisor crowding
 Further more, recrowding has often been noted even in
patients treated with mandibular incisor extraction

 Comparing the lengths of the maxillary and mandibular
arches, a different behavior in the nonextraction group
can be seen. Whereas the maxillary arch had a net
increase in arch length (UL3), LL4 decreased. In the
extraction group, the maxillary and mandibulararch
lengths increased slightly from bracket removal to
follow-up .

 In both the nonextraction and extraction groups, UL3
increased from end of retention to follow-up. This could
be the result of torque relapse. The increase of UL3 is in
contrast to the decrease of almost all other length
measurements (UL4, LL4, and LL5).
 Generally speaking, maxillary and mandibular arch
lengths tended to decrease, with few exceptions

CONCLUSION
 This study investigated changes in maxillary and
mandibular arch lengths in patients treated with
edgewise appliances, with and without premolar
extractions. The results were----
 In the maxilla, arch length UL3 increased in
nonextraction patients; all other lengths in both arches
and both groups decreased
 The relapse tendency was less in the maxillary arch than
in the mandibular.
 The extraction group showed similar relapse tendencies
in both arches www.indiandentalacademy.com

Ellen A. BeGole,
Deborah L. Fox, and
Cyril Sadowsky
AJODO;1998;113
Analysis of change in arch form
with premolar expansion

 The arch forms of 38 cases (53 nonextraction and 23
extraction arches) in which expansion, while maintaining
arch form, was the objective of the practitioner, were
analyzed before treatment, after treatment, and an
average of 6 to 8 years after retention.
 The cubic spline was used to fit a curve representing
arch form. By superimposing the spline curves, changes
in arch form were analyzed with the variables rebound
change (RC), rebound index (RI), rebound number (RN),
and stability number (SN). Traditional linear intraarch
dimensions were also analyzed

 Analysis of variance was used to determine differences
between the maxillary and mandibular arches and
between the extraction and nonextraction cases.
 Pearson correlation coefficients between spline variables
and arch width variables were also computed. There was
significantly more expansion in the maxillary arch than
the mandibular arch during treatment, irrespective of
extraction or nonextraction strategies

 In the nonextraction cases, a greater amount of net
expansion was achieved for all dimensions for the
maxillary arch as compared with the mandibular arch.
 Overall, a relatively high stability in arch form was found.
The findings suggest that stability may not be related to
the amount of change produced during treatment.

 Significant expansion can be gained throughout the
premolar regions and may be expected to be stable.
 The order of greatest net arch width gained was for the
second premolars followed by first premolars, molars,
and then the canines.
 The intercanine widths for both arches decreased toward
pretreatment values, but were more stable in the
maxillary arch in nonextraction cases. The cubic spline
permits measurement of change in arch form both
during treatment and retention periods.

CONCLUSIONS
 Use of the cubic spline permits measurement of changes
in shape and size, but does not distinguish between
them.
 There does not appear to be any meaningful
relationship between the amount of change
duringtreatment and the degree of stability of a case
 Significant stable expansion of the premolar and molar
widths may be possible in both the maxillary and
mandibular arches in nonextraction cases.

Thank you
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Effects on the dental arch form using a /certified fixed orthodontic courses by Indian dental academy

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Effects on the dental arch form using a /certified fixed orthodontic courses by Indian dental academy