Download CEPHALOMETRIC ANALYSIS OF THE SOFT-TISSUE PROFILE CHANGES

CEPHALOMETRIC ANALYSIS OF THE SOFT-TISSUE PROFILE CHANGES
IN PATIENTS TREATED WITH FOUR FIRST PREMOLAR AND
FOUR SECOND PREMOLAR EXTRACTIONS
Daniel J. Breha, D.M.D.
A Thesis Presented to the Graduate Faculty of
Saint Louis University in Partial Fulfillment
of the Requirements for the Degree of
Master of Science in Dentistry
2014
COMMITTEE IN CHARGE OF CANDIDACY:
Professor Rolf G. Behrents,
Chairperson and Advisor
Professor Eustaquio A. Araujo
Associate Clinical Professor Donald
R. Oliver
i
DEDICATION
This work is dedicated to my family.
Thank you for
your unending love and support while I pursue my dreams.
ii
ACKNOWLEDGEMENTS
This project was completed with the help of the
following individuals:
Dr. Rolf Behrents.
Thank you for all of your help
with this project and allowing me to pursue my
orthodontic education at Saint Louis University.
Dr. Eustaquio Araujo.
Thank you for all of your
help and encouragement with this project and in the
clinic.
Dr. Donald Oliver.
Thank you for always going the
extra mile in helping me throughout residency and with
this project.
iii
TABLE OF CONTENTS
List of Tables.........................................v
List of Figures........................................vi
Chapter 1: Introduction................................1
Chapter 2: Review of the Literature....................5
Extractions.......................................5
Effect of Extractions on Lip Position.............6
Effect of Growth and Extractions on Soft Tissue...10
Incisor and Lip Retraction........................13
Effects of Different Premolar Extraction Patterns.17
Statement of Thesis...............................22
Literature Cited..................................24
Chapter 3: Journal Article.............................28
Abstract..........................................28
Introduction......................................30
Materials and Methods.............................34
Sample.......................................34
Methodology..................................35
Statistical Analysis.........................40
Reliability..................................40
Results...........................................41
Pre-Treatment Measurements...................41
Treatment Changes............................42
Discussion........................................46
Conclusions.......................................52
Literature Cited..................................53
Appendix...............................................56
Vita Auctoris..........................................59
iv
LIST OF TABLES
Table 2.1
Lip position change to Esthetic Plane
following extraction treatment ...........8
Table 2.2
Ratio of incisor retraction to lip
retraction ...............................15
Table 3.1
Study cast measurements...................35
Table 3.2
Pre-treatment measurements................42
Table 3.3
Treatment changes four first premolar
extraction group .........................43
Table 3.4
Treatment changes four second premolar
extraction group .........................44
Table 3.5
Treatment change between extraction groups
.........................................45
Table A.1
Landmarks and definitions.................56
Table A.2
Absolute pre-treatment measurements.......57
Table A.3
Absolute treatment change between extraction
groups ...................................58
v
LIST OF FIGURES
Figure 3.1
Landmark Location.......................37
Figure 3.2
Reference Planes........................38
vi
CHAPTER 1: INTRODUCTION
On a daily basis, orthodontists are faced with the
decision whether to extract or not extract teeth when
diagnosing and treatment planning.
Angle has suggested
that an intact dentition arranged in an optimum occlusion
results in the soft tissue assuming a harmonious
position.1
On the other hand, Tweed proposed an upright
mandibular incisor over basal bone is both stable and
esthetic.2
Many studies exist in the orthodontic literature
which looked at changes in the facial profile and incisor
position as a result of orthodontic treatment with
premolar extractions.
These studies are important to
help guide the clinician in making treatment decisions
and to know the effect they might have on the patient’s
soft tissue profile.
While considerable variation has been demonstrated,
previous studies have generally shown soft tissue profile
flattening when comparing the lips to the Esthetic
Plane.3-8
Kocadereli found the upper and lower lips move
posteriorly -1.0 mm and -1.1 mm respectively to the
Esthetic Plane.3
Bishara et al. found more posterior
movement with the upper lip moving -3.7 mm and the lower
lip moving -3.4 mm to the Esthetic Plane.4
Bravo found
similar posterior movement reporting the upper lip moving
1
-3.4 mm and lower lip moving -3.8 mm posterior to the
Esthetic Plane.5
Luecke and Johnston reported -2.4 mm
posterior movement of the upper lip and -1.4 mm posterior
movement of the lower lip to the Esthetic Plane.6
Finally, Cloward reported -2.8 mm posterior movement of
the upper lip and -3.5 mm posterior movement of the lower
lip compared to the Esthetic Plane.8
The posterior
movement of the upper and lower lips can be either
beneficial or detrimental to the patient depending on how
protrusive or flat the soft tissue profile is at the
start of treatment.
Other authors have tried to quantify the amount of
incisor retraction as it affects lip retraction.
Their
results are generally variable and point to a greater
correlation between the lower incisor to lower lip
retraction than upper incisor to upper lip retraction.8-14
Cloward found an upper incisor to upper lip retraction
ratio of 2.1:1 and lower incisor to lower lip retraction
ratio of 1.1:1.8
Similarly, Kasai found the upper incisor
to upper lip retraction ratio of 2.3:1 and lower incisor
to lower lip retraction ratio of 0.8:1.9
Roos reported a
ratio of 2.5:1 for the upper incisor to upper lip
retraction and a ratio of 1.1:1 for lower incisor to
lower lip retraction.11
Rudee reported a ratio of 2.9:1
for the upper incisor to upper lip retraction and 0.6:1
for the lower incisor to lower lip retraction.13
2
Finally,
Hanson found an upper incisor to upper lip retraction
ratio of 2.0:1 and lower incisor to lower lip retraction
ratio of 1.3:1.14
When a patient presents with a balanced soft tissue
facial profile and mild to moderate tooth mass arch
length discrepancy, the orthodontist is faced with a
tough decision to treat the patient nonextraction or with
the extraction of premolars.
A few authors have proposed
the extraction of second premolars in patients whose soft
tissue facial profiles warrant little to no flattening
from lip retraction and present with mild to moderate
tooth mass arch length discrepancy.15-16
Boley looked at
51 consecutively treated patients with four second
premolars extracted and reported the “mouth area” was
improved or not affected in 92% of the patients when
judged by laypersons.17
Previous studies have shown considerable variability
of incisor retraction when comparing four first premolars
and four second premolar extractions.
In general, less
incisor retraction is seen when second premolars are
extracted compared to first premolars.18-22
Steyn et al.
found when four first premolars were extracted, the upper
incisor was retracted -4.7 mm and the lower incisor was
retracted -4.2 mm.
When four second premolars were
extracted, they reported the upper incisor to be
retracted -2.1 mm and lower incisor to be retracted
3
-1.3 mm.18
Shearn and Woods measured lower incisor
retraction to be -2.4 mm when four first premolars were
extracted and -0.5 mm when four second premolars were
extracted.19
Ong and Woods measured the upper incisor to
be retracted -4.2 mm when four first premolars were
extracted and -2.3 mm when four second premolars were
extracted.20
Kim et al. also reported more upper and
lower incisor retraction when four first premolars are
extracted.
They found the upper incisors to be retracted
-4.71 mm and lower incisors to be retracted -5.13 mm when
four first premolars were extracted.
They also found the
upper incisor retraction to be -2.33 mm and lower incisor
retraction to be -3.01 mm when four second premolars were
extracted.23
Despite the differences reported in the literature
on the amount the upper and lower incisors are retracted
when four first and four second premolars are extracted,
few studies have looked to see if there is a significant
difference in the change of the soft tissue profile as a
result of treatment.
This study aims to provide an
evidence-based answer to see if patients treated
orthodontically with four first premolar or four second
premolar extractions produce differing or similar changes
on the soft tissue profile post-treatment.
4
CHAPTER 2: REVIEW OF THE LITERATURE
Extractions
On a daily basis, orthodontists are faced with the
decision whether to extract or not extract teeth when
diagnosing and treatment planning.
This decision has
been a topic of debate for a long time.
In 1907, Angle
suggested that if the dentition was intact and arranged
in an optimum occlusion, the soft tissue would then
assume a harmonious position.1
On the other hand, Tweed
thought the removal of teeth was often necessary to
obtain normal occlusion.
He proposed the use of a
skeletal diagnostic triangle as an aid to treatment
planning, with the assumption that an upright mandibular
incisor over basal bone is both stable and esthetic.2
In 1994, Proffit completed a forty-year review of
extraction frequencies at the University of North
Carolina Orthodontic Clinic.
He found the total
extraction percentage was 30% in 1953, peaked at 76% in
1968, and declined to 28% by 1993.
Some of the reasons
he hypothesized might be the cause for a decline in
extraction rates were the greater concern for facial
esthetics, data that suggests extractions might not
guarantee stability, concerns about temporomandibular
dysfunction, and changes in orthodontic treatment
techniques.24
Proffit developed contemporary guidelines
5
for orthodontic extractions for Class I crowded cases.
His guidelines suggest that extractions are rarely
indicated with less than 4 mm of tooth mass arch length
discrepancy.
With 5 to 9 mm of tooth mass arch length
discrepancy, nonextraction or extraction treatment may be
possible.
Finally, if the tooth mass arch length
discrepancy is 10 mm or greater, extractions are almost
always required.25
Effect of Extractions on Lip Position
The effect extractions have on the facial profile is
something that has been studied extensively in
orthodontics.
This is of primary concern due to the
effect extractions and incisor retraction have on the
soft tissue profile.
Previous studies have generally
shown soft tissue profile flattening when comparing the
lips to the Esthetic Plane in four premolar extraction
cases.3-8
Boley performed a survey with 25 consecutively
treated first or second premolar extraction cases and 25
consecutively treated nonextraction cases.
He asked 192
general dentists and orthodontists to identify whether
the patient was treated with or without extractions.
the survey, respondents answered correctly 54% of the
In
time.
He concluded, the face does not get “ruined” in
6
patients that are properly diagnosed and treated with
extractions.26
The Esthetic Plane and “Law of lip relationship”
were developed by Ricketts as a guideline to where the
lips should be positioned when compared to the
surrounding soft tissue.
The “Law of lip relationship”
states the lips should be contained within a line from
the nose to the chin, and the outline of the lips have a
smooth contour, the upper lip lies slightly posterior to
the lower lip when related to the line, and the mouth can
be closed with no soft tissue strain.
This line from the
tip of the nose to the chin is called the Esthetic Plane.
The lower lip should lie 4 mm +/- 3 mm behind this plane
in normal Caucasians at maturity.
In 12 to 14 year olds
the lower lip should lie 2 mm +/- 3 mm behind the
Esthetic Plane.27
Studies have used the Esthetic Plane to
measure the amount of upper and lower lip movement from
pre- to post-treatment.
The results are summarized in
table 2.1.
7
Table 2.1 Lip position change to Esthetic Plane following
extraction treatment
Author
Kocadereli3
Bishara4
Bravo5
Luecke and Johnston6
James7
Cloward8
Lip Change (mm)
Upper
Lower
Lip
Lip
-1.0
-1.1
-3.7
-3.4
-3.4
-3.8
-2.4
-1.4
-3.3
-2.8
-3.5
Kocadereli used Ricketts Esthetic Plane in his study
with 40 Class I four first premolar extraction patients
and 40 Class I nonextraction patients.
He found the
upper lip moved -1.0 mm +/- 1.9 mm and the lower lip
-1.1 mm +/- 2.0 mm in the extraction group.
In the
nonextraction group the upper lip moved -0.4 mm +/2.2 mm and lower lip -0.08 mm +/- 2.4 mm relative to the
Esthetic Plane.
The change in the lower lip position to
the Esthetic Plane was found to be statistically
significant between the extraction and nonextraction
group, but the upper lip change was not found to be
statistically significant.3
Bishara et al. also studied patients treated with
four first premolars extracted and nonextraction.
All of
the patients in their study were Class II division 1.
They found the four first premolar extraction group was
more protrusive at the start of treatment than the
nonextraction group, and finished treatment with a
8
straighter profile and more upright incisors than the
nonextraction group.
The upper lip moved -3.7 mm and
lower lip -3.4 mm to the Esthetic Plane in the extraction
group.
In the nonextraction group the upper lip moved
forward 1.2 mm and lower lip moved forward 0.5 mm to the
Esthetic Plane.4
Bravo found similar lip retraction to the Esthetic
Plane when he studied 16 females who were treated with
premolar extractions.
He found the upper lips moved
-3.4 mm and lower lip -3.8 mm to the Esthetic Plane.
also found the nasolabial angle increased 3.7˚.
He
Despite
this amount of movement of the upper and lower lips to
the Esthetic Plane and increase in the nasolabial angle,
it was found only 12% of patients finished with a
flattened profile.5
In Luecke and Johnston’s study, they looked at 42
Class II division 1 patients treated with only the upper
first premolars extracted.
They found an average upper
lip retraction of -1.4 mm to the mean functional occlusal
plane and -2.4 mm to the Esthetic Plane.
The average
lower lip retraction was -0.1 mm to the mean functional
occlusal plane and -1.4 mm to the Esthetic Plane.
They
concluded the soft tissue profile appears to be more
influenced by growth of the nose and chin than by
treatment.6
9
James conducted a study which looked at 170
consecutively treated patients, of which 108 were treated
with extractions and 62 were treated nonextraction.
He
found at pretreatment the nonextraction group was more
retrusive than the extraction group.
The extraction
group presented with a greater soft tissue lip and chin
imbalance, but improved with treatment more than the
nonextraction group.
The lower lip moved -3.3 mm to the
Esthetic Plane in the extraction group and moved forward
1.1 mm to the Esthetic Plane in the nonextraction group.
He concluded that with extraction of the proper teeth,
balanced facial esthetics can be achieved.7
Cloward found similar movement of the lower lip to
the Esthetic Plane in his study of 30 Caucasian, Class I,
minimally crowded, adolescent patients treated with four
first premolar extractions.
He found the upper and lower
lips moved -2.82 mm and -3.47 mm respectively to the
Esthetic Plane.8
Effect of Growth and Extractions on Soft Tissue
The amount that orthodontic treatment and growth
affects the soft tissue of the face has been studied by
many investigators.
Nanda and Ghosh studied 40 white
untreated subjects from the age of 7 to 18 with at least
6 cephalograms taken during this age range.
They
concluded the male upper lip increased in length an
10
average of 6.9 mm and the female upper lip increased on
average 2.7 mm in length.
They also found males grew in
a more sagittal direction making their profile more
prognathic and females grew in a more downward direction
making their profile more convex.
Finally, they found
that long faced individuals have longer lips and thicker
soft tissue than short faced individuals.28
Kasai also found that individuals with longer facial
patterns have thicker upper lips and soft tissue over B
point.
He found this by studying the soft tissue on
cephalograms of 297 Japanese women.
He also noted the
soft tissue thickness of the chin is associated with a
larger ANB angle.9
Singh also studied the soft tissue thickness over
the chin in 60 patients.
Twenty-three patients were
treated with four first premolars extracted and 37
treated nonextraction.
He registered the soft tissue
thickness of the chin at 6 points around the symphysis.
The study found the soft tissue increases around all
points during treatment and is influenced by age, sex,
and facial type.
He found females have a more even soft
tissue thickness around the chin.
Also noted, the soft
tissue in males over the chin increased in thickness more
than females.
As a whole, dolicocephalic patients have
the greatest increase in soft tissue chin thickness
during this time.
Despite changes in soft tissue
11
thickness around the chin during treatment, he did not
find a difference between the extraction and
nonextraction group and concludes orthodontics has little
impact on the change in soft tissue thickness around the
chin.29
Subtelny also found the soft tissue around the chin
increased more in males than females during growth.
He
studied the soft tissue thickness over the chin in 30
subjects from 3 to 18 years old.
The soft tissue
thickness over pogonion increased by 2.4 mm in males and
1.0 mm in females.
When excluding the nose from
analysis, he noted the soft tissue profile remained
relatively stable with growth.
With the nose, the soft
tissue profile became more convex.30
In Bhavnani’s study, she looked at 57 untreated
individuals with an average age of 16 years old matched
to 47 treated individuals.
She compared pre-treatment
cephalograms with cephalograms taken 25 years posttreatment.
In extraction patients the soft tissue
changes were generally in a forward direction.
The
nonextraction group’s soft tissue changed in a more
downward and forward direction.
It was found there were
no substantive differences between the extraction and
nonextraction groups 25 years post-treatment.31
Roos studied the effect extractions have on the
change in lip thickness from pre- to post-treatment.
12
He
studied 30 Class II division 1 patients treated with four
first bicuspid extractions.
All of his linear
measurements were indexed to the length of sella-nasion.
He found the upper lip increased 2.19 +/- 3.46 index
units and the lower lip decreased 2.39 +/- 2.55 index
units.11
This coincides with Erdinc et al. who found the
upper lip thickness increases and lower lip thickness
decreases with extractions.
In nonextraction treatment,
the lower lip thickness was found to increase.
Erdinc et
al. also found the upper lip vermillion increased and
lower lip vermillion decreased in extraction cases.32
Perkins and Staley studied the vermillion height
change in 40 patients treated with extractions.
They
found both the upper and lower lip vermillion heights
decreased 0.76 mm and 0.78 mm respectively.
The
vermillion height decrease of the lower lip was found to
be statistically significant but not for the upper lip.10
Incisor and Lip Retraction
The relationship of incisor retraction and lip
retraction has been reported by many investigators in the
orthodontic literature.
Multiple variables affect the
amount of lip response to incisor retraction.
Oliver
studied the effect of lip strain and lip thickness on lip
response.
He found a strong correlation between upper
lip retraction and upper incisor retraction with thin
13
lips in both males (r=0.92) and females (r=0.98).
This
correlation was low in patients with thick upper lips.
The study also found a strong correlation of vermillion
border changes in the presence of high lip strain when
upper incisor retraction occurred in both males (r=0.92)
and females (r=0.82).33
Perkins and Staley found when stomion superius was
less than 6 mm from incision superius at pretreatment,
the average decrease in vermillion display was 0.88 mm
for the upper lip and 0.87 mm for the lower lip.
They
did not find a significant difference in vermillion
display from pre- to post-treatment in the upper and
lower lips when stomion superius was greater than 6 mm
from incision superius.10
Other variables that might affect the lip response
are palatal plane angulation and the change in angulation
of the maxillary incisors with treatment.
Waldman found
a moderate correlation (r=0.42) of the nasolabial angle
increasing in patients whose maxillary incisors were
tipped lingually with treatment.
He also found the
nasolabial angle increased more in patients with a large
palatal plane angle to a pterygomaxillary-vertical
reference plane.12
A common calculation in past studies is the ratio of
incisor retraction to lip retraction.
summarized below in table 2.2.
14
This data is
Table 2.2 Ratio of incisor retraction to lip retraction
Author
Cloward8
Kasai9
Perkins10
Roos11
Waldman12
Rudee 13
Hanson14
Ratio
U1:UL
L1:LL
2.1:1
1.1:1
2.3:1
0.8:1
2.2:1
2.5:1
1.1:1
3.8:1
2.9:1
0.6:1
2.0:1
1.3:1
Cloward found the ratio of upper incisor to upper
lip retraction to be 2.1:1.
The lower incisor to lower
lip retraction ratio was 1.1:1.
His study found a
moderate correlation between the upper incisor and upper
lip (r=0.62) and a strong correlation between the lower
incisor and lower lip (r=0.87).8
Kasai found similar ratios in his study of Class I
and Class II division 1 Japanese women.
He found the
upper incisor to upper lip ratio to be 2.3:1 and the
lower incisor to lower lip ratio to be 0.8:1.
He also
found the lower lip response to lower incisor retraction
to be more predictable than the upper lip response to
upper incisor retraction.9
Perkins and Staley also found a similar mean ratio
of 2.2:1 for upper incisor to upper lip retraction when
looking at 40 adult females.
Twenty of the subjects were
Class I and 20 were Class II division 1 and showed a
variability between the two subgroups.
15
In the subgroup
whose upper incisor tip was less than 6 mm to stomion
superioris at rest, the ratio was 1.8:1.
In the subgroup
whose upper incisor tip was greater than 6 mm for stomion
superioris at rest, the ratio was 6.0:1.10
Roos also found similar ratios of incisor retraction
to lip retraction in his study of 30 Class II division 1
patients treated with four first premolar extractions.
He found the upper incisor to upper lip ratio to be 2.5:1
and the lower incisor to lower lip ratio to be 1.1:1.
He
found a moderate correlation (r=0.42) for the upper
incisor to upper lip ratio and a strong correlation
(r=0.82) for the lower incisor to lower lip ratio.11
Waldman only computed a ratio for the upper incisor
to upper lip retraction in his study of 41 Class II
patients.
He found the ratio to be slightly higher than
previous studies mentioned at 3.8:1 with a moderate
correlation (r=0.42).12
Rudee also found a slightly
higher ratio for upper incisor to upper lip retraction
and a slightly lower ratio for lower incisor to lower lip
retraction than previous studies mentioned.
The ratios
he found were 2.9:1 and 0.6:1 respectively.
The author
did find a high correlation for both the upper lip
response (r=0.73) and lower lip response (r=0.70) to
incisor retraction.13
Hanson also calculated a ratio for incisor
retraction to lip response.
She looked at 180
16
orthodontically treated patients.
One hundred fifty
patients were treated with various extraction patterns
and 30 were treated nonextraction.
Her results showed an
average upper incisor to upper lip retraction of 2.0:1
and lower incisor to lower lip retraction of 1.3:1.
She
also found a high degree of correlation for upper lip
response (r=0.70) and lower lip response (r=0.73).14
Her
results are similar to the previous studies mentioned.
Collectively, all of the studies indicate a high degree
of individual variability between upper and lower incisor
retraction to upper and lower lip retraction.
Effects of Different Premolar Extraction Patterns
In 1949, Nance was one of the first orthodontists to
advocate the extraction of four second premolars instead
of the common practice of four first premolars.
He
recommended this extraction pattern in cases with mild
bimaxillary protrusion and crowding.
In such cases, he
proposed the molar would move further forward into the
extraction space than in four first premolar extraction
cases.
He felt that this does not allow as much incisor
retraction, thus the facial soft tissue will have less of
a tendency to distort.15
Dewel proposed similar
indications for four second premolar extractions.
He
proposed border-line cases with acceptable facial balance
17
and mild to moderate tooth size arch length disprepancy
were the best candidates for this extraction pattern.16
To look for criteria on how to decide to extract
four first premolars or four second premolars,
Ketterhagen evaluated 43 patients treated with these two
extraction patterns.
In a discrimanant analysis of the
two extraction groups, he found the pretreatment lips to
the Esthetic Plane and the angle of the lower incisor to
the A Point–pogonion line were statistically significant.
He found that in the four first premolar extraction group
the lips were on average 0.74 mm in front of the Esthetic
Plane and were -2.4 mm behind the Esthetic Plane in the
four second premolar extraction group.
His study also
found the lower incisor had a larger lower incisor angle
to the A Point–pogonion line in the four first premolar
extraction group than the four second premolar extraction
group.34
Boley, studied 51 consecutively treated cases with
four second premolars extracted.
From the pretreatment
records, he noted that on average the patients had mild
to moderate crowding and slightly full profiles.
He did
a survey with 95 laypersons and asked them to judge the
the change in “mouth area” from pre- to post-treatment.
Ninety-two percent of the laypersons said the “mouth
area” was not adversely affected or improved.17
18
Other authors studied the effects that different
extraction patterns have on incisor position, molar
position, and vertical dimension.
Steyn et al. compared
206 actively growing caucasian boys and girls treated
with differing extraction patterns.
They found the upper
incisors were retracted -4.7 mm in the four first
premolar extraction group and -4.2 mm in the four second
premolar extraction group.
They also found that the
lower incisors were retracted -2.1 mm in the four first
premolar group and -1.3 mm in the four second premolar
extraction group.
All pre- and post-treatment
measurements were made from the Nasion-Pogonion line.18
Shearn and Woods measured lower incisor retraction
in four first premolar and four second premolar
extraction groups from an A point-pogonion reference
plane.
They found a similar amount of lower incisor
retraction of -2.4 mm in the four first premolar
extraction group as did Steyn et al.
However, Shearn and
Woods found the lower incisors were retracted -0.5 mm in
the four second premolar extraction group which is less
than what Steyn et al. found.
Shearn and Woods also
found the lower molars moved forward more in the four
second premolar extraction group than the four first
premolar extraction group.
The amount of forward
movement was 4.4 mm and 2.8 mm respectively.19
19
Ong and Woods also found more upper incisor
retraction in the four first premolar group compared to
the four second premolar extraction group.
The
difference was found to be -4.2 mm and -2.3 mm
respectively when measured from a pterygomaxillaryvertical reference plane.
They also looked at
differences between the extraction groups at
pretreatment.
Lower incisor protrusion was the only
statistically significant difference between the two
groups.20
Luppanapornlarp and Johnston studied the effects of
premolar extraction in “clear cut” extraction and
nonextraction Class II cases.
They noted a mean 3 mm
retraction on the lower incisors when lower first
premolars were extracted and a mean 2 mm retraction of
the lower incisors when lower second premolars were
extracted.21
Al-Nimri looked at 70 Class II division 1 patients
who were treated with extractions.
No lower incisor
retraction was planned, and it was found the lower
incisors were retracted -1.3 mm when lower first
premolars were extracted and -0.8 mm when lower second
premolars were extracted.
Multiple regression analysis
was performed on the data and it was found residual space
had the highest correlation and accounted for 36% of the
change in lower incisor position.22
20
Chen et al. looked at 26 four second premolar
extraction patients with mild crowding, Class I, slight
dental protrusion, and normal FMA.
They found the
incisors and molars take up roughly equal amounts of the
extraction spaces.
The mean upper incisor and lower
incisor retraction was -3.3 mm and -2.9 mm respectively.
The mean upper molar and lower molar movement forward was
3.2 mm and 3.4 mm respectively.
The measurements were
all made by regional superimpositions of the mandible and
maxilla.35
Other authors have studied the effect on facial
vertical dimension between four first premolar and four
second premolar extraction cases.
Kim et al. looked at
54 high angle cases where 27 were treated with first
premolars extracted and 27 were treated with second
premolars extracted.
They did not find a statistically
significant difference in facial vertical dimension
between the two groups.
However, like previously
mentioned studies, they did find differences in the
amount of incisor retraction and forward movement of the
molars between the two groups.
In the four first
premolar extraction group the upper incisors were
retracted -4.71 mm and lower incisors were retracted
-5.13 mm.
The four second premolar extraction group had
the upper incisors retracted -2.33 mm and the lower
incisors were retracted -3.01 mm.
21
The authors also found
a statistically significant difference in how much the
upper and lower molars moved forward.
The upper molars
moved forward 2.72 mm and lower molars 2.14 mm in the
four first premolar extraction group.
In the second
premolar extraction group the upper molars moved forward
3.84 mm and lower molars 3.62 mm.
Their findings are
similar to Chen et al. where incisor retraction and
forward molar movement took up roughly half of the
extraction space.23
Hadavand also looked at different extraction
patterns and their effect on the mandibular plane angle.
He did not find a statistically significant difference
when comparing the four first premolar extraction group
to the upper first, lower second premolar extracion
group.36
Statement of Thesis
Extractions in orthodontics are often used to
relieve crowding, correct anterio-posterior
discrepancies, and protrusion.
The effect of extractions
on the soft-tissue has been studied extensively in the
literature.
Generally, some flattening in the soft
tissue profile is seen when the upper and lower incisors
are retracted.
This may be benificial for patients with
a protrusive profile, but may be detrimental in patients
with an already flat soft tissue profile.
22
The second
premolar extracton pattern has been presented as an
option in patients with acceptable facial balance and
mild to moderate tooth size arch length discrepancy.15-16
Previous studies in the orthodontic literature have
shown more incisor retraction when first premolars are
extracted in comparison to second premolars.
Few studies
have looked to see if there is a statistically
significant difference in the pre- and post-treatment
change in soft tissue profile.
This study aims to provide an evidence-based answer
to see whether different premolar extraction patterns
produce differing or similar changes on the soft tissue
profile during treatment.
23
Literature Cited
1. Angle E. Treatments of Malocclusion of Teeth. 7th ed.
Philadelphia: SS White Dent Mfg Co; 1907.
2. Tweed CH. Indications for the extraction of teeth in
orthodontic procedure. Am J Orthod Oral Surg.
1944;42(30):405-28.
3. Kocadereli I. Changes in soft tissue profile after
orthodontic treatment with and without extractions.
Am J Orthod Dentofacial Orthop. 2002;122(1):67-72.
4. Bishara SE, Cummins DM, Jakobsen JR, Zaher AR.
Dentofacial and soft tissue changes in Class II,
division 1 cases treated with and without
extractions. Am J Orthod Dentofacial Orthop.
1995;107(1):28-37.
5. Bravo LA. Soft tissue facial profile changes after
orthodontic treatment with four premolars extracted.
Angle Orthod. 1994;64(1):31-42.
6. Luecke PE, 3rd, Johnston LE, Jr. The effect of
maxillary first premolar extraction and incisor
retraction on mandibular position: testing the
central dogma of "functional orthodontics". Am J
Orthod Dentofacial Orthop. 1992;101(1):4-12.
7. James RD. A comparative study of facial profiles in
extraction and nonextraction treatment. Am J Orthod
Dentofacial Orthop. 1998;114(3):265-76.
8. Cloward DJ. Facial profile changes with extraction of
four first premolars in caucasian, Class I,
minimally-crowded, adolescent patients. Saint Louis:
Saint Louis University; 2013.
9. Kasai K. Soft tissue adaptability to hard tissues in
facial profiles. Am J Orthod Dentofacial Orthop.
1998;113(6):674-84.
10. Perkins RA, Staley RN. Change in lip vermilion height
during orthodontic treatment. Am J Orthod
Dentofacial Orthop. 1993;103(2):147-54.
11. Roos N. Soft-tissue profile changes in Class II
treatment. Am J Orthod. 1977;72(2):165-75.
24
12. Waldman BH. Change in lip contour with maxillary
incisor retraction. Angle Orthod. 1982;52(2):129-34.
13. Rudee DA. Proportional profile changes concurrent
with orthodontic therapy. Am J Orthod.
1964;50(6):421-34.
14. Hanson RA. Incisor retraction and lip response with
various extraction patterns in caucasian females.
Saint Louis: Saint Louis University; 2003.
15. Nance HN. The removal of second premolars in
orthodontic treatment. Am J Orthod. 1949;35(9):68596.
16. Dewel BF. Second premolar extraction in orthodontics:
Principles, procedures, and case analysis. Am J
Orthod. 1955;41(2):107-20.
17. Boley JC. An extraction approach to borderline tooth
size to arch length problems in patients with
satisfactory profiles. Semin Orthod. 2001;7(2):1006.
18. Steyn CL, du Preez RJ, Harris AM. Differential
premolar extractions. Am J Orthod Dentofacial
Orthop. 1997;112(5):480-6.
19. Shearn BN, Woods MG. An occlusal and cephalometric
analysis of lower first and second premolar
extraction effects. Am J Orthod Dentofacial Orthop.
2000;117(3):351-61.
20. Ong HB, Woods MG. An occlusal and cephalometric
analysis of maxillary first and second premolar
extraction effects. Angle Orthod. 2001;71(2):90-102.
21. Luppanapornlarp S, Johnston LE, Jr. The effects of
premolar-extraction: a long-term comparison of
outcomes in "clear-cut" extraction and nonextraction
Class II patients. Angle Orthod. 1993;63(4):257-72.
22. Al-Nimri KS. Changes in mandibular incisor position
in Class II division 1 malocclusion treated with
premolar extractions. Am J Orthod Dentofacial
Orthop. 2003;124(6):708-13.
23. Kim TK, Kim JT, Mah J, Yang WS, Baek SH. First or
second premolar extraction effects on facial
vertical dimension. Angle Orthod. 2005;75(2):177-82.
25
24. Proffit WR. Forty-year review of extraction
frequencies at a university orthodontic clinic.
Angle Orthod. 1994;64(6):407-14.
25. Proffit WR, Fields HW, Sarver DM. Contemporary
Orthodontics. Fifth ed. St. Louis: Mosby Elsevier;
2013. 224-5 p.
26. Boley JC, Pontier JP, Smith S, Fulbright M. Facial
changes in extraction and nonextraction patients.
Angle Orthod. 1998;68(6):539-46.
27. Ricketts RM. Esthetics, environment, and the law of
lip relation. Am J Orthod. 1968;54(4):272-89.
28. Nanda RS, Ghosh J. Facial soft tissue harmony and
growth in orthodontic treatment. Semin Orthod.
1995;1(2):67-81.
29. Singh RN. Changes in the soft tissue chin after
orthodontic treatment. Am J Orthod Dentofacial
Orthop. 1990;98(1):41-6.
30. Subtelny JD. A longitudinal study of soft tissue
facial structures and their profile characteristics,
defined in relation to underlying skeletal
structures. Am J Orthod. 1959;45(7):481-507.
31. Bhavnani AN. A longitudinal cephalometric study
evaluating the soft tissue profiles of patients
treated with extraction mechanics 25 years posttreatment. Saint Louis: Saint Louis University;
2012.
32. Erdinc AE, Nanda RS, Dandajena TC. Profile changes of
patients treated with and without premolar
extractions. Am J Orthod Dentofacial Orthop.
2007;132(3):324-31.
33. Oliver BM. The influence of lip thickness and strain
on upper lip response to incisor retraction. Am J
Orthod. 1982;82(2):141-9.
34. Ketterhagen DH. First premolar or second premolar
extractions: formula or clinical judgment? Angle
Orthod. 1979;49(3):190-8.
35. Chen K, Han X, Huang L, Bai D. Tooth movement after
orthodontic treatment with 4 second premolar
extractions. Am J Orthod Dentofacial Orthop.
2010;138(6):770-7.
26
36. Hadavand RR. Mandibular response to different
extraction patterns. Saint Louis: Saint Louis
University; 2004.
27
CHAPTER 3: JOURNAL ARTICLE
Abstract
Purpose:
The purpose of this study is to investigate if
different premolar extraction patterns have different or
similar effects on the soft tissue profile.
and Methods:
Materials
A sample of 125 subjects was selected from
the records at Saint Louis University Center for Advanced
Dental Education.
The cases were selected based on the
following criteria: 1) Caucasian, 2) Class I or Class II
division 1, 3) 10 to 16 years of age at start of
treatment, 4) treatment with extractions of four first
premolars or four second premolars, 5) good quality preand post-treatment cephalometric radiographs, and 6) good
quality pre-treatment mandibular orthodontic study
models.
The sample was divided into two groups; 63
patients in the four first premolar extraction group and
62 patients in the four second premolar extraction group.
Pre-treatment mandibular crowding was calculated using
Profitt’s segmental technique.
Pre-treatment and post-
treatment cephalograms were analyzed.
Linear
cephalometric measurements were converted to indices of
the sella-nasion distance.
Independent sample t-tests
were used for each variable to detect pre-treatment
differences between the groups and differences in mean
changes as a result of treatment.
28
Results:
At pre-
treatment, the four first premolar extraction group had
1.58 mm more crowding, 1.75 mm less residual space, a
more protrusive lip position compared to the Esthetic
Plane, and 1.12 index units more incisal overjet.
Compared to the four second premolar extraction group,
the four first premolar extraction group had 0.90 index
units more overjet reduction and 1.68 index units more
upper incisor retraction.
The four second premolar group
had 2.07 and 2.40 index units more forward movement of
the upper and lower molars respectively.
The mean change
of upper and lower lip position was not statistically
significant between the two extraction groups.
Conclusions:
The results of this study do not support
choosing one extraction pattern over the other in hopes
of achieving a different soft tissue response.
It does
confirm different amounts of upper incisor retraction and
forward movement of the upper and lower molars between
the two extraction patterns.
29
Introduction
On a daily basis, orthodontists are faced with the
decision whether to extract or not extract teeth when
diagnosing and treatment planning.
Angle has suggested
that an intact dentition arranged in an optimum occlusion
results in the soft tissue assuming a harmonious
position.1
On the other hand, Tweed proposed an upright
mandibular incisor over basal bone is both stable and
esthetic.2
Many studies exist in the orthodontic literature
which looked at changes in the facial profile and incisor
position as a result of orthodontic treatment with
premolar extractions.
These studies are important to
help guide the clinician in making treatment decisions
and to know the effect they might have on the patient’s
soft tissue profile.
While considerable variation has been demonstrated,
previous studies have generally shown soft tissue profile
flattening when comparing the lips to the Esthetic
Plane.3-8
Kocadereli found the upper and lower lips move
posteriorly -1.0 mm and -1.1 mm respectively to the
Esthetic Plane.3
Bishara et al. found more posterior
movement with the upper lip moving -3.7 mm and the lower
lip moving -3.4 mm to the Esthetic Plane.4
Bravo found
similar posterior movement reporting the upper lip moving
30
-3.4 mm and lower lip moving -3.8 mm posterior to the
Esthetic Plane.5
Luecke and Johnston reported -2.4 mm
posterior movement of the upper lip and -1.4 mm posterior
movement of the lower lip to the Esthetic Plane.
Finally, Cloward reported -2.8 mm posterior movement of
the upper lip and -3.5 mm posterior movement of the lower
lip compared to the Esthetic Plane.8
The posterior
movement of the upper and lower lips can be either
beneficial or detrimental to the patient depending on how
protrusive or flat the soft tissue profile is at the
start of treatment.
Other authors have tried to quantify the amount of
incisor retraction as it affects lip retraction.
Their
results are generally variable and point to a greater
correlation between the lower incisor to lower lip
retraction than upper incisor to upper lip retraction.8-14
Cloward found an upper incisor to upper lip retraction
ratio of 2.1:1 and lower incisor to lower lip retraction
ratio of 1.1:1.8
Similarly, Kasai found the upper incisor
to upper lip retraction ratio of 2.3:1 and lower incisor
to lower lip retraction ratio of 0.8:1.9
Roos reported a
ratio of 2.5:1 for the upper incisor to upper lip
retraction and a ratio of 1.1:1 for lower incisor to
lower lip retraction.11
Rudee reported a ratio of 2.9:1
for the upper incisor to upper lip retraction and 0.6:1
for the lower incisor to lower lip retraction.13
31
Finally,
Hanson found an upper incisor to upper lip retraction
ratio of 2.0:1 and lower incisor to lower lip retraction
ratio of 1.3:1.14
When a patient presents with a balanced soft tissue
facial profile and mild to moderate tooth mass arch
length discrepancy, the orthodontist is faced with a
tough decision to treat the patient nonextraction or with
the extraction of premolars.
A few authors have proposed
the extraction of second premolars in patients whose soft
tissue facial profiles warrant little to no flattening
from lip retraction and present with mild tooth mass arch
length discrepancy.15-16
Boley looked at 51 consecutively
treated patients with four second premolars extracted and
reported the “mouth area” was improved or not affected in
92% of the patients when judged by laypersons.17
Previous studies have shown considerable variability
of incisor retraction when comparing four first premolars
and four second premolar extractions.
In general, less
incisor retraction is seen when second premolars are
extracted compared to first premolars.18-22
Steyn et al.
found when four first premolars were extracted, the upper
incisor was retracted -4.7 mm and the lower incisor was
retracted -4.2 mm.
When four second premolars were
extracted, they reported the upper incisor to be
retracted -2.1 mm and lower incisor to be retracted
-1.3 mm.18
Shearn and Woods measured lower incisor
32
retraction to be -2.4 mm when four first premolars were
extracted and -0.5 mm when four second premolars were
extracted.19
Ong and Woods measured the upper incisor to
be retracted -4.2 mm when four first premolars were
extracted and -2.3 mm when four second premolars were
extracted.20
Kim et al. also reported more upper and
lower incisor retraction when four first premolars are
extracted.
They found the upper incisors to be retracted
-4.71 mm and lower incisors to be retracted -5.13 mm when
four first premolars were extracted.
They also found the
upper incisor retraction to be -2.33 mm and lower incisor
retraction to be -3.01 mm when four second premolars were
extracted.23
Despite the differences reported in the literature
on the amount the upper and lower incisors are retracted
when four first and four second premolars are extracted,
few studies have looked to see if there is a significant
difference in the change of the soft tissue profile as a
result of treatment.
This study aims to provide an
evidence-based answer to see if patients treated
orthodontically with four first premolar or four second
premolar extractions produce differing or similar changes
on the soft tissue profile post-treatment.
33
Materials and Methods
Sample
The sample of 125 subjects was selected from the
records at Saint Louis University Center for Advanced
Dental Education.
The cases were selected on the basis
of the following inclusion criteria: 1) Caucasian, 2)
Class I or Class II division 1, 3) 10 to 16 years old at
start of treatment 4) treatment with extractions of four
first premolars or four second premolars, 5) good quality
pre- and post-treatment cephalometric radiographs, and 6)
good quality pre-treatment mandibular orthodontic study
models.
The 63 subjects in the four first premolar
extraction group consisted of 35 females and 28 males.
The average age at onset of treatment was 13.08 +/- 1.48
years old.
44 subjects were Class I and 19 subjects were
Class II division 1 at the start of treatment.
The 62 subjects in the four second bicuspid
extraction group consisted of 37 females and 25 males.
The average age at onset of treatment was 13.22 +/- 1.28
years old.
Forty-three subjects were Class I and 19
subjects were Class II division 1 at the start of
treatment.
34
Methodology
From each of the patients, pre-treatment mandibular
crowding was calculated.
Proffit’s segmental method was
used by subtracting the pretreatment segmental total from
the added mesio-distal widths of mandibular right second
premolar to mandibular left second premolar.24
Residual
space was calculated by adding the mesio-distal widths of
the extracted premolars to the crowding.
If canines or
premolars were unerupted or missing, their size was
estimated using the Tanaka and Johnston prediction values
formula.25
Table 3.1 Study cast measurements
Measurement
(mm)
Arch segments
Study Cast Measurements
Definition
Distance between the lines perpendicular
to the contact points of a segment of
teeth; between the mesial contact of the
first molar and the distal contact point
of the lateral incisor and between the
distal contact point of the lateral
incisor and the mesial contact point of
the central incisor
Crowding
Proffit's segmental technique; subtract
pre-treatment segmental total from summed
widths of mandibular right second premolar
to mandibular left second premolar
Residual Space Widths of extracted premolars plus
crowding
Tanaka and
1/2 the sum of the widths of the
Johnston
mandibular incisors, plus 10.5 mm
Prediction
Values
Tooth width
Distance from mesial contact point to
distal contact point
35
From each of the patient records, pre-treatment and
post-treatment cephalograms were traced on high quality
acetate.
Six hard tissue and four soft tissue landmarks
were located.
A diagram of landmark location can be seen
in Figure 3.1 and their definitions can be located in
Appendix Table A.1.
The pre-treatment and post-treatment
tracings were digitized using Dentofacial Planner
software (Dentofacial Software, Inc. Dentofacial Planner,
Version 7.0, Toronto, Canada).
36
N
S
Prn
UL
U6
L6
L1
U1 LL
Pog’
Figure 3.1 Landmark location
An X-Y coordinate grid was constructed utilizing the
Dentofacial Planner software. The x-axis was represented
by a constructed line, which was created by decreasing
the SN line by 7˚ (SN-7˚).
The y-axis was represented by
a vertical line perpendicular to SN-7˚ through sella.
These reference planes are depicted in figure 3.2.
37
SN
SN-7˚ (X-axis)
Y-axis
Figure 3.2 Reference planes
From the reference planes and landmarks, six
horizontal and vertical measurements were computed by the
Dentofacial Planner software.
Horizontal linear
measurements were made from the y-axis parallel to the xaxis for landmarks upper lip, lower lip, upper incisor,
lower incisor, upper molar, and lower molar.
Vertical
linear measurements were made from the x-axis parallel to
the y-axis for the landmarks upper lip, lower lip, upper
38
incisor, lower incisor, upper molar, and lower molar.
Pre-treatment to post-treatment horizontal and vertical
changes were computed by subtracting the pre-treatment
landmark position from the post-treatment landmark
position.
Pre-treatment and post-treatment measurements
for upper and lower lip to Esthetic Plane were computed
using the Dentofacial Planner software.
Changes were
computed by subtracting the pre-treatment upper lip and
lower lip position to Esthetic Plane from the posttreatment upper lip and lower lip position to Esthetic
Plane.
Finally, pre-treatment and post-treatment overjet
was calculated parallel to the x-axis by subtracting the
horizontal lower incisor tip position from the horizontal
upper incisor tip position.
Change in overjet was
computed by subtracting the pre-treatment overjet from
the post-treatment overjet.
To correct for size differences between subjects and
magnification differences between cephalograms, all
linear measurements were converted to indices of the
sella-nasion distance.
The indices were calculated by
dividing the linear measurements from the same subject by
the calculated sella-nasion distance for that subject and
multiplying the quotient by 100. For absolute pretreatment measurements and treatment changes between
extraction groups see Table A.2 and Table A.3 in
Appendix.
39
Statistical Analysis
Descriptive data was obtained for all measurements
and statistical analysis was done utilizing the
Statistical Package for the Social Science (IBM SPSS,
Version 20, Armonk, NY).
Independent sample t-tests were
used for each variable to detect differences at the start
of treatment between the four first premolar and four
second premolar extraction groups.
Paired t-tests were
used for each variable to detect differences between pretreatment and post-treatment measurements within each
extraction group.
Independent sample t-tests were used
for each variable to detect differences in mean changes
between the four first premolar and four second premolar
extraction groups.
A significance level of p <.05 was
set to detect differences for all statistical analyses.
Reliability
To determine the consistency of measurements,
Chronbach’s alpha was used.
Intra-class correlations
greater than or equal to 0.80 were considered to be
reliable.
All measurements for 13 randomly selected
subjects were re-measured to test for intra-examiner
reliability.
measurements.
Chronbach’s alpha was above 0.80 for all
This indicates original and repeated
measurements were at an acceptable level of reliability
for accuracy of measurements.
40
Results
Pre-Treatment Measurements
Descriptive data was obtained for pre-treatment
measurements.
Independent sample t-tests were calculated
for each variable to detect differences at the start of
treatment between the four first premolar and four second
premolar extraction groups.
The results showed more pre-
treatment crowding and less residual space in the four
first premolar extraction group.
The average upper and
lower lip position in the four second premolar extraction
group was farther behind the Esthetic Plane.
Finally,
the four first premolar extraction group had a larger
pre-treatment overjet.
Details are given below in Table
3.2.
41
Table 3.2 Pre-treatment measurements
Pre-treatment Measurements
Four First
Four Second
Group
Premolar
Premolar
Extractions
Extractions
Variable
Mean
SD
Mean
SD
Sig.
Crowding (mm)**
-4.16 3.24
-2.58 3.11 0.006*
Residual Space
10.88 3.20
12.63 3.14 0.003*
(mm)**
E plane to UL
-2.25 3.62
-3.69 2.84 0.014*
E plane to LL
0.41 4.17
-1.74 3.30 0.002*
Overjet
6.51 2.70
5.39 1.77 0.007*
Horizontal-U1
100.32 7.19
99.79 6.10
0.662
Horizontal-L1
93.81 6.57
94.41 5.91
0.595
Horizontal-U6
59.54 5.63
59.81 5.05
0.779
Horizontal-L6
59.70 6.50
60.06 5.39
0.739
Horizontal-UL
119.46 6.75
120.30 5.83
0.461
Horizontal-LL
114.12 7.24
114.74 6.85
0.623
Vertical-U1
-102.31 6.84 -102.09 6.47
0.851
Vertical-L1
-97.28 7.53
-96.42 6.49
0.498
Vertical-U6
-89.10 6.40
-89.03 5.65
0.945
Vertical-L6
-98.34 6.55
-97.81 5.98
0.635
Vertical-UL
-89.64 6.97
-89.52 5.65
0.921
Vertical-LL
-109.87 8.58 -108.59 7.79
0.386
*P<.05
**All measurements converted to index units of
sella-nasion except where noted otherwise
Treatment Changes
Descriptive data was obtained for the pre- to posttreatment changes for each variable.
calculated for each variable.
Paired t-tests were
All variables in both the
four first premolar and four second premolar extraction
groups showed statistically significant changes.
are given below in Table 3.3 and Table 3.4.
42
Details
Table 3.3 Treatment changes four first premolar
extraction group
Pre- to Post-Treatment Change
Variable
Mean Change
SD
Sig.
E plane to UL
-3.73 2.67 0.000*
E plane to LL
-3.78 2.42 0.000*
Overjet
-2.75 2.89 0.000*
Horizontal-U1
-5.75 5.16 0.000*
Horizontal-L1
-3.00 3.72 0.000*
Horizontal-U6
3.36 2.21 0.000*
Horizontal-L6
4.43 2.77 0.000*
Horizontal-UL
-2.48 3.74 0.000*
Horizontal-LL
-2.51 3.92 0.000*
Vertical-U1
-1.10 2.90 0.004*
Vertical-L1
-3.39 3.20 0.000*
Vertical-U6
-2.83 2.75 0.000*
Vertical-L6
-2.61 2.90 0.000*
Vertical-UL
-1.73 2.76 0.000*
Vertical-LL
-1.48 3.64 0.001*
*P<.05
All measurements converted to index
units of sella-nasion
43
Table 3.4 Treatment changes four second premolar
extraction group
Pre- to Post-Treatment Change
Variable
Mean Change
SD
Sig.
E plane to UL
-3.89 2.37 0.000*
E plane to LL
-3.55 2.33 0.000*
Overjet
-1.85 1.50 0.000*
Horizontal-U1
-4.07 3.75 0.000*
Horizontal-L1
-2.22 3.59 0.000*
Horizontal-U6
5.43 2.75 0.000*
Horizontal-L6
6.83 2.84 0.000*
Horizontal-UL
-1.81 3.69 0.000*
Horizontal-LL
-1.83 3.73 0.000*
Vertical-U1
-1.32 3.26 0.002*
Vertical-L1
-3.75 3.40 0.000*
Vertical-U6
-3.05 2.70 0.000*
Vertical-L6
-3.04 2.90 0.000*
Vertical-UL
-1.75 3.12 0.000*
Vertical-LL
-1.20 4.33 0.035*
*P<.05
All measurements converted to index
units of sella-nasion
Independent sample t-tests were calculated for each
variable to detect differences in mean changes between
the four first premolar and four second premolar
extraction groups.
The results show the four first
premolar extraction group had a greater reduction in
overjet and more retraction of the upper incisor.
The
four second premolar extraction group had more forward
horizontal movement of the upper and lower first molars.
Details are provided in Table 3.5.
44
Table 3.5 Treatment change between extraction groups
Pre- to Post-Treatment Change
Four First
Four Second
Group
Premolar
Premolar
Extractions
Extractions
Mean
Mean
Variable
SD
SD
Sig.
Change
Change
E plane to UL
-3.73 2.67
-3.89 2.37
0.719
E plane to LL
-3.78 2.42
-3.55 2.33
0.580
Overjet
-2.75 2.89
-1.85 1.50 0.041*
Horizontal-U1
-5.75 5.16
-4.07 3.75 0.039*
Horizontal-L1
-3.00 3.72
-2.22 3.59
0.237
Horizontal-U6
3.36 2.21
5.43 2.75 0.000*
Horizontal-L6
4.43 2.77
6.83 2.84 0.000*
Horizontal-UL
-2.48 3.74
-1.81 3.69
0.314
Horizontal-LL
-2.51 3.92
-1.83 3.73
0.323
Vertical-U1
-1.10 2.90
-1.32 3.26
0.695
Vertical-L1
-3.39 3.20
-3.75 3.40
0.543
Vertical-U6
-2.83 2.75
-3.05 2.70
0.656
Vertical-L6
-2.61 2.90
-3.04 2.90
0.418
Vertical-UL
-1.73 2.76
-1.75 3.12
0.973
Vertical-LL
-1.48 3.64
-1.20 4.33
0.690
*P<.05
All measurements converted to index units of sellanasion
45
Discussion
An analysis of soft tissue profile changes in
patients treated with four first premolars and four
second premolar extractions has not been found in the
orthodontic literature.
Nance and Dewel each promoted
the extraction of four second premolars in patients whose
soft tissue profiles were acceptable at pre-treatment and
presented with mild to moderate tooth mass arch length
discrepancy.
Both of them thought this extraction
pattern would distort the soft tissue facial profile less
than extracting four first premolars.15-16
The present
study aimed to provide an evidence-based answer to see if
patients treated orthodontically with four first premolar
or four second premolar extractions have different or
similar changes on the soft tissue profile posttreatment.
The findings of this study do not support the
rationale for choosing one extraction pattern over the
other in the hopes of a more favorable soft tissue
response.
This study looked at 125 Caucasian patients
treated orthodontically with either four first premolar
extractions or four second premolar extractions.
All
patients were under the age of 16 years old at the start
of treatment and were either Class I or Class II
division 1.
46
This study found the upper lip was retracted -0.67
index units more and the lower lip was retracted -0.68
index units more in the four first premolar extraction
group compared to the four second premolar extraction
group.
This finding was not found to be statistically
significant.
Also, the upper and lower lips changed
roughly the same amount in both extraction groups when
compared to the Esthetic Plane.
It was found the upper
lip was retracted -3.73 index units and lower lip
retracted -3.78 index units in the four first premolar
extraction group.
In the four second premolar extraction
group the upper lip was retracted -3.89 index units and
lower lip -3.55 index units when compared to the Esthetic
Plane.
Pre-treatment measurements of both extraction groups
were compared and it was found the four first premolar
extraction group had -1.58 mm more mandibular crowding,
1.75 mm less residual space, and 1.12 index units more
incisal overjet than the four second premolar extraction
group.
The second premolar extraction group on average
had the upper and lower lips positioned further behind
the Esthetic Plane than the four first premolar
extraction group.
The pre-treatment difference in lip position to the
Esthetic Plane in this study coincides with the results
from Ketterhagen’s study.
He looked for differences
47
between the four first premolar and four second premolar
extraction groups at pre-treatment to try to find the
reason why one extraction pattern was chosen over the
other.
He found the lower lip was positioned 0.41 mm in
front of the Esthetic Plane in the four first premolar
extraction group and -2.4 mm behind the Esthetic Plane in
the four second premolar extraction group.
This study
also found the lower lip to be positioned in front of the
Esthetic Plane in the four first premolar extraction
group and behind the Esthetic Plane in the four second
premolar extraction group.
However, this study did find
a statistically significant difference in the amount of
tooth mass arch length discrepancy between the two
extraction groups at pre-treatment and Ketterhagen did
not.26
This study found the mandibular tooth mass arch
length discrepancy was -4.16 mm and -2.58 mm in the four
first and four second premolar extraction groups
respectively.
In previous studies, the amount of upper and lower
incisor retraction between the two groups has been
variable.
Generally, the four first premolar extraction
group has been found to exhibit more upper and lower
incisor retraction when compared to the four second
premolar extraction group.
The findings of the present
study are consistent in that the upper incisors were
retracted -1.68 index units more in the four first
48
premolar extraction group.
Also, the lower incisors were
retracted -0.78 index units more in the four first
premolar extraction group compared to the four second
premolar extraction group.
Between the extraction
groups, only the upper incisor retraction was
statistically significant.
The findings of the present study are consistent
with Steyn et al. who also found more incisor retraction
in the four first premolar extraction group compared to
the four second premolar extraction group.
They found
the difference to be -0.5 mm for the upper incisor and
-0.8 mm for the lower incisor in their sample of 206
actively growing Caucasian males and females.18
Shearn
and Woods only compared lower incisor retraction between
the two extraction groups and found -1.9 mm more lower
incisor retraction in the four first premolar extraction
group.19
Ong and Woods only looked at the difference in
upper incisor retraction and found -1.8 mm more
retraction in the four first premolar extraction group.20
Finally, Kim et al. also found the upper incisors to be
retracted -2.38 mm and lower incisors -2.12 mm more in
the four first premolar extraction group.23
A reason the upper incisor may have been retracted
more in the four first premolar extraction group of the
present study is the group started with more pretreatment overjet.
To achieve an ideal occlusion at the
49
end of treatment, the overjet would have to be reduced
more in the four first premolar extraction group compared
to the four second premolar extraction group.
Future
studies may want to account for pre-treatment differences
between the two extraction groups.
An ideal sample of
patients to study would be the same ethnicity, have a
narrow age range, have the same amount of pre-treatment
crowding, overjet, molar classification, and lip
protrusion to the Esthetic Plane.
All patients should be
treated with the same treatment protocol as it pertains
to anchorage.
The present study found the molars to move forward
more in the four second premolar extraction group
compared to the four first premolar extraction group.
The difference was found to be 2.07 index units more for
the upper molar and 2.40 index units more for the lower
molar.
The differences in upper and lower forward
movement between the two extraction groups were both
statistically significant.
This finding is consistent with Shearn and Woods who
found the lower molar to move forward 1.6 mm more in the
four second premolar extraction group compared to the
four first premolar extraction group.19
Kim et al. also
found a difference of forward movement for the upper and
lower molars between the two extraction groups.
They
found the upper molar to move forward 1.12 mm more and
50
the lower molar to move forward 1.48 mm more in the four
second premolar extraction group.23
51
Conclusions
Given the results of this study, the following
conclusions can be made:
1. Choosing one extraction pattern over the other in
hopes of achieving a different soft tissue
response is not supported by the findings of this
study.
2. More upper incisor retraction can be expected when
four first premolars are extracted compared to
when four second premolars are extracted.
A
difference in lower incisor retraction should not
be expected.
3. More forward movement of the upper and lower
molars can be expected when four second premolars
are extracted compared to when four first
premolars are extracted.
4. Future studies should account for pre-treatment
differences between the two extraction groups.
An
ideal sample of patients to study would be the
same ethnicity, have a narrow age range, have the
same amount of pre-treatment crowding, overjet,
molar classification, and lip protrusion to the
Esthetic Plane.
All patients should be treated
with the same anchorage protocol.
52
Literature Cited
1. Angle E. Treatments of Malocclusion of Teeth. 7th ed.
Philadelphia: SS White Dent Mfg Co; 1907.
2. Tweed CH. Indications for the extraction of teeth in
orthodontic procedure. Am J Orthod Oral Surg.
1944;42(30):405-28.
3. Kocadereli I. Changes in soft tissue profile after
orthodontic treatment with and without extractions.
Am J Orthod Dentofacial Orthop. 2002;122(1):67-72.
4. Bishara SE, Cummins DM, Jakobsen JR, Zaher AR.
Dentofacial and soft tissue changes in Class II,
division 1 cases treated with and without
extractions. Am J Orthod Dentofacial Orthop.
1995;107(1):28-37.
5. Bravo LA. Soft tissue facial profile changes after
orthodontic treatment with four premolars extracted.
Angle Orthod. 1994;64(1):31-42.
6. Luecke PE, 3rd, Johnston LE, Jr. The effect of
maxillary first premolar extraction and incisor
retraction on mandibular position: testing the
central dogma of "functional orthodontics". Am J
Orthod Dentofacial Orthop. 1992;101(1):4-12.
7. James RD. A comparative study of facial profiles in
extraction and nonextraction treatment. Am J Orthod
Dentofacial Orthop. 1998;114(3):265-76.
8. Cloward DJ. Facial profile changes with extraction of
four first premolars in caucasian, Class I,
minimally-crowded, adolescent patients. Saint Louis:
Saint Louis University; 2013.
9. Kasai K. Soft tissue adaptability to hard tissues in
facial profiles. Am J Orthod Dentofacial Orthop.
1998;113(6):674-84.
10. Perkins RA, Staley RN. Change in lip vermilion height
during orthodontic treatment. Am J Orthod
Dentofacial Orthop. 1993;103(2):147-54.
11. Roos N. Soft-tissue profile changes in Class II
treatment. Am J Orthod. 1977;72(2):165-75.
53
12. Waldman BH. Change in lip contour with maxillary
incisor retraction. Angle Orthod. 1982;52(2):129-34.
13. Rudee DA. Proportional profile changes concurrent
with orthodontic therapy. Am J Orthod.
1964;50(6):421-34.
14. Hanson RA. Incisor retraction and lip response with
various extraction patterns in caucasian females.
Saint Louis: Saint Louis University; 2003.
15. Nance HN. The removal of second premolars in
orthodontic treatment. Am J Orthod. 1949;35(9):68596.
16. Dewel BF. Second premolar extraction in orthodontics:
Principles, procedures, and case analysis. Am J
Orthod. 1955;41(2):107-20.
17. Boley JC. An extraction approach to borderline tooth
size to arch length problems in patients with
satisfactory profiles. Semin Orthod. 2001;7(2):1006.
18. Steyn CL, du Preez RJ, Harris AM. Differential
premolar extractions. Am J Orthod Dentofacial
Orthop. 1997;112(5):480-6.
19. Shearn BN, Woods MG. An occlusal and cephalometric
analysis of lower first and second premolar
extraction effects. Am J Orthod Dentofacial Orthop.
2000;117(3):351-61.
20. Ong HB, Woods MG. An occlusal and cephalometric
analysis of maxillary first and second premolar
extraction effects. Angle Orthod. 2001;71(2):90-102.
21. Luppanapornlarp S, Johnston LE, Jr. The effects of
premolar-extraction: a long-term comparison of
outcomes in "clear-cut" extraction and nonextraction
Class II patients. Angle Orthod. 1993;63(4):257-72.
22. Al-Nimri KS. Changes in mandibular incisor position
in Class II division 1 malocclusion treated with
premolar extractions. Am J Orthod Dentofacial
Orthop. 2003;124(6):708-13.
23. Kim TK, Kim JT, Mah J, Yang WS, Baek SH. First or
second premolar extraction effects on facial
vertical dimension. Angle Orthod. 2005;75(2):177-82.
54
24. Proffit WR, Fields HW, Sarver DM. Contemporary
Orthodontics. Fifth ed. St. Louis: Mosby Elsevier;
2013. 427-30 p.
25. Tanaka MM, Johnston LE. The prediction of the size of
unerupted canines and premolars in a contemporary
orthodontic population. J Am Dent Assoc.
1974;88(4):798-801.
26. Ketterhagen DH. First premolar or second premolar
extractions: formula or clinical judgment? Angle
Orthod. 1979;49(3):190-8.
55
Appendix
Table A.1 Landmarks and definitions
Landmark
Sella
Nasion
Abbreviation Definition
S
The center of the pituitary
fossa
N
The most anterior point of the
frontonasal suture
Pronasale
Prn
Most anterior point on the
nasal tip
Upper Lip
UL
The most anterior point on the
upper lip
Lower Lip
LL
The most anterior point on the
lower lip
Soft Tissue Pog'
Pogonion
The most anterior point on the
contour of the chin
Maxillary
U1
Incisor Tip
The incisal tip of the
maxillary central incisor
Mandibular
L1
Incisor Tip
The incisal tip of the
mandibular central incisor
Maxillary
Molar
Mesial
Contact
Mandibular
Molar
Mesial
Contact
U6
The mesial contact point of the
maxillary first molar
L6
The mesial contact point of the
mandibular first molar
56
Table A.2 Absolute pre-treatment measurements
Pre-treatment Measurements
Four First
Four Second
Group
Premolar
Premolar
Extractions
Extractions
Variable (mm)
Mean
SD
Mean
SD
Crowding
-4.16 3.24
-2.58 3.11
Residual Space
10.88 3.20
12.63 3.14
E plane to UL
-1.62 2.62
-2.67 2.01
E plane to LL
0.32 3.01
-1.27 2.38
Overjet
4.76 2.01
3.93 1.35
Horizontal-U1
73.28 6.04
72.58 5.28
Horizontal-L1
68.52 5.50
68.65 4.93
Horizontal-U6
43.52 4.79
43.52 4.26
Horizontal-L6
43.63 5.24
43.71 4.53
Horizontal-UL
87.28 6.20
87.50 5.60
Horizontal-LL
83.37 6.30
83.45 5.91
Vertical-U1
-74.66 4.65 -74.19 4.72
Vertical-L1
-70.98 5.06 -70.07 4.61
Vertical-U6
-65.03 4.46 -64.70 4.08
Vertical-L6
-71.76 4.36 -71.08 4.26
Vertical-UL
-65.42 4.83 -65.09 4.49
Vertical-LL
-80.19 6.09 -78.93 5.77
*P<.05
57
Sig.
0.006*
0.003*
0.013*
0.001*
0.008*
0.490
0.895
0.996
0.929
0.837
0.945
0.575
0.294
0.665
0.374
0.693
0.237
Table A.3 Absolute treatment change between extraction
groups
Pre- to Post-Treatment Change
Four First
Four Second
Group
Premolar
Premolar
Extractions
Extractions
Mean
Mean
Variable (mm)
SD
SD
Change
Change
E plane to UL
-2.74 1.98
-2.82 1.72
E plane to LL
-2.77 1.78
-2.62 1.76
Overjet
-2.01 2.14
-1.35 1.41
Horizontal-U1
-4.21 3.80
-2.95 2.73
Horizontal-L1
-2.20 2.71
-1.60 2.61
Horizontal-U6
2.46 1.63
3.97 2.02
Horizontal-L6
3.25 2.04
4.96 2.06
Horizontal-UL
-1.81 2.75
-1.33 2.70
Horizontal-LL
-1.84 2.86
-1.32 2.70
Vertical-U1
-0.78 2.13
-0.94 2.37
Vertical-L1
-2.47 2.34
-2.71 2.46
Vertical-U6
-2.06 2.00
-2.19 1.95
Vertical-L6
-1.91 2.12
-2.18 2.10
Vertical-UL
-1.26 2.01
-1.24 2.28
Vertical-LL
-1.24 2.95
-0.85 3.13
*P<.05
58
Sig.
0.790
0.927
0.045*
0.035*
0.208
0.000*
0.000*
0.318
0.296
0.691
0.576
0.724
0.473
0.955
0.473
Vita Auctoris
Daniel Joseph Breha was born on August 19th, 1986 in
Parma, Ohio to Paul and Susan Breha.
He grew up in Seven Hills, Ohio and graduated from
Normandy High School in 2005.
After high school, he
attended The Ohio State University in Columbus, Ohio and
concentrated his studies in biochemistry for three years.
In 2008, he started dental school at Case Western Reserve
University and graduated with a Doctor of Dental Medicine
degree in 2012.
He then attended Saint Louis
University’s Orthodontic residency program.
He expects
to receive his Masters of Science in Dentistry degree in
December 2014.
Daniel plans to practice orthodontics in Ohio after
receiving his degree and marry his fiancée Michelle
Gerstenhaber on May 24th, 2015.
59