Download Eniko K. Toth, D.M.D. Saint Louis University in Partial Fulfillment

RELATIONSHIPS BETWEEN THE SOFT TISSUE IN A POSED SMILE AND
CEPHALOMETRIC SKELETAL MEASUREMENTS
Eniko K. Toth, 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:
Associate Professor Ki Beom Kim,
Advisor and Chairperson
Associate Clinical Professor Donald R. Oliver
Assistant Clinical Professor J. Michael Hudson
i
DEDICATION
This work is dedicated to my mother who has been there
every step of the way supporting me throughout my
educational journey. Without her many sacrifices I would
not be where I am today.
To Scott, who on a daily basis motivated me to keep
going and gave me the support and love I needed.
Lastly, thank you to all the faculty of Saint Louis
University’s Orthodontic Department. The knowledge and
guidance I received from them allowed me to complete this
work. To them I give credit for any future success I have
in my upcoming orthodontic career.
ii
ACKNOWLEDGEMENTS
This project would not have been possible without the
help of the following individuals:
Dr. Ki Beom Kim. Thank you for being my advisor and
giving me such key support through this thesis process.
Additionally, thank you for all the instruction in clinic
that I will take forward with me for decades to come.
Dr. Don Oliver. Thank you for being a valuable member
of my committee, and for your attention to detail when it
came to revisions. Most of all, I would like to thank you
for your unparalleled commitment to this institution and to
the clinical education of not only me, but also every
resident.
Dr. J. Michael Hudson. Thank you for also being a
valued member of my committee. I want to especially thank
you for taking the time out from your busy life and own
orthodontic practice to come and help further enrich the
clinical knowledge of the residents here at SLU. I greatly
appreciate it.
Kimberly Cox. Thank you for having all the answers and
for always solving all my problems.
iii
TABLE OF CONTENTS
List of Tables.........................................v
List of Figures........................................vi
CHAPTER 1: INTRODUCTION................................1
CHAPTER 2: REVIEW OF THE LITERATURE
Smile Esthetics...................................4
Macro-Esthetics..............................4
Mini-Esthetics...............................4
Micro-Esthetics..............................4
Attractive and Unattractive Smiles...........5
Controllable Factors.........................6
Uncontrollable Factors.......................7
The Lips..........................................8
Smile Type Based On Lip Movement.............9
Facial Types......................................11
Facial Type Characteristics..................12
Records for Smile Diagnosis and Evaluation........13
Morpheus 3d..................................15
Smile Reproducibility.............................16
Summary and Statement of Thesis...................17
Literature Cited..................................19
CHAPTER 3: JOURNAL ARTICLE
Abstract..........................................23
Introduction......................................25
Materials and Methods.............................26
Sample.......................................26
Methodology..................................27
Statistical Analysis.........................35
Reliability..................................36
Results...........................................37
Correlations.................................37
Multiple Linear Regression Analysis..........40
Discussion........................................41
Conclusions.......................................48
Literature Cited..................................49
Appendix...............................................52
Vita Auctoris..........................................53
iv
LIST OF TABLES
Table 3.1
Cephalometric Lines/Measurements and
Definitions.............................29
Table 3.2
Soft Tissue Landmarks and Definitions...31
Table 3.3
Measurements from Posed Smile...........32
Table 3.4
Significant correlations between
skeletal vertical variables and soft
tissue parameters of the smile showing
moderate strength of association........37
Table 3.5
Significant correlations between
skeletal vertical variables and soft
tissue parameters of the smile showing
weak strength of association............40
Table 3.6
Significant multiple linear regression
results.................................41
Table 3.7
Multiple Linear Regression Equations....41
Table A.1
Cephalometric Landmarks and Definitions.52
v
LIST OF FIGURES
Figure 2.1
Cuspid Smile............................10
Figure 2.2
Commissure Smile........................10
Figure 2.3
Complex Smile...........................10
Figure 3.1
Landmarks located.......................28
Figure 3.2
Soft Tissue Scan in Repose..............33
Figure 3.3
Soft Tissue Scan in Posed Smile.........34
Figure 3.4
Three Dimensional Cartesian Plane.......35
Figure 3.5
Scatterplot of mandibular plane (SN-GoGn)
and Smile Index (SI) for each subject in
the study...............................38
Figure 3.6
Scatterplot of Anterior Facial Height
(AFH) and Interlabial Gap (IG) for each
subject in the study....................38
Figure 3.7
Scatterplot of Anterior Facial Height
(AFH) and Smile Index (SI) for each
subject in the study....................39
Figure 3.8
Scatterplot of mandibular plane (SN-GoGn)
and Interlabial Gap (IG) for each subject
in the study............................39
vi
CHAPTER 1: INTRODUCTION
The smile is an important part of social interaction.
Smiles project a variety of positive emotions such as
happiness, approval, and humor.
An esthetically pleasing
smile may improve a person’s confidence in social
situations.
Therefore it may not be surprising that one of
the main reasons younger children and their parents seek
orthodontic care has been reported to reduce teasing.1
As patients become more concerned with the esthetics
of their smile, it has become more relevant for
orthodontists to pay attention to the soft tissue
framework.
It would be prudent to evaluate the parameters of a
smile before treatment in order to know not only what needs
to be done, but also what can be done, and to communicate
that with the patient and or parent.2,
3
Ackerman and
Ackerman point out that when one analyses a smile,
compromises between the opposing factors of esthetic goals
and the patients’ physiologic limitations are often made.3
Though the associations between cephalometric
measurements and clinical observations have long been
studied, less attention has been given to possible
1
associations between hard tissue characteristics as
quantified by cephalometrics and the soft tissue
characteristics of the smile.
The purpose of this study is to see if there are any
correlations present between the soft tissues of the posed
smile and cephalometric skeletal measurements, in order to
see if there may be any inherent differences in the lip
movement during smile based on the skeletal pattern.
2
CHAPTER 2: REVIEW OF THE LITERATURE
When one looks back at history, during much of the
twentieth century orthodontists focused on the skeletal and
hard tissue components of malocclusion. Angle described
ideal occlusion in terms of occluding buccal cusps.4
If the
mesial-buccal cusp of the upper molar fit into the buccal
groove of the lower first molar, it was considered ideal.
After Broadbent popularized cephalometrics, skeletal linear
and angular measurements were added to the focus.5
With the
increased use of lateral cephalometrics, studying the face
from the profile view was emphasized.
A functionally
balanced occlusion and balanced profile was and still is an
important cornerstone of orthodontic treatment.
Practitioners however, eventually began to realize the
importance of the smile and the surrounding soft tissue in
the frontal view.
Most people’s motivation to seek
orthodontic treatment is primarily tied to esthetics.6
Although some patients may be aware of their profile
esthetics, on a day-to-day basis they view themselves
straight on.
With the ever-increasing media driven
emphasis on human image perfection, people are becoming
more highly critical of their smiles.
3
Smile Esthetics
Orthodontists now pay attention to concepts of “smile
design” and macro, mini, and micro-esthetics.7 These
concepts take the soft tissue framework into mind when
diagnosing. Sarver and Jacobson broke down the components
of their esthetic dentofacial analysis which follows a
gradient from large to small parameters.8
Macro-Esthetics
Macroesthetics look at the face as a whole. The
profile, vertical proportions of the face, lip fullness,
chin-nasal projection, and facial widths are all looked at.
Mini-Esthetics
Miniesthetics focuses on the framework of the smile.
This category is where the lips come into play for most of
the factors. Incisor display, the transverse dimension of
the smile, smile symmetry, the smile arc, and teeth
crowding are evaluated.
Micro-Esthetics
The final category takes a more in depth look at the
actual teeth themselves. A thorough look is taken at
gingival shapes and contours, emergence profiles, tooth
4
color and shape, contacts, connectors, and embrasures. Most
of these characteristics can be taken into consideration of
the orthodontic treatment plan, or can also be dealt with
in the restorative realm of dentistry.
Evaluating the smile as a whole and identifying
attributes of an ideal smile with more modern concepts such
as gingival zeniths, embrasures, smile arc, etc. is a good
start in achieving the best smile that can be created.
Attractive and Unattractive Smiles
Beauty, as expressed in a common idiom, “is in the eye
of the beholder,” and thus lives in the subjective realm.
However, through a number of studies over the years certain
characteristics have been identified which both
orthodontists and lay people find attractive or
unattractive.
One of the most recognized identified
factors in beauty is symmetry.9 A consonant smile arc,
minimal gingival display, symmetric commissural elevation,
and width to height ratios of 1:0.8 for maxillary central
incisors, among other attributes have all been shown to be
desirable components of a smile.10-12
Factors shown to be deemed more unattractive, among
others, include excessive gingival display, dark buccal
5
corridors, any exposure of lower incisors, greater distance
from upper incisors to lower lip, large midline deviations,
and occlusal cants.13-16
Schabel, Franchi, Baccetti, and McNamara found that
smiles were rated more unattractive when there was a
significantly greater distance between the incisal edge of
the maxillary central incisors and the lower lip during
smiling, and a significantly smaller smile index. The smile
index is obtained by dividing the intercommissural width by
the interlabial gap. Other factors rated unattractive were
excessive height of the smile or deficient smile width.15
It is important to be aware of what among these
factors can be controlled with orthodontics, what factors
may need surgical or other means for altering, and what
factors cannot be changed.
Controllable Factors
Orthodontists work towards trying to achieve an ideal
smile arc in their patients.
It is deemed ideal when the
curvature of the incisal edges of the maxillary incisors
and canines follow the curvature of the lower lip.10 The
orthodontist can control some of the factors during smile
arc development with the ability to improve or even in some
6
cases worsen it.
The orthodontist for example, has control
over factors such as the transverse dimension, levels and
locations of the gingival zeniths, heights of the incisal
edges, and vertical placement of teeth via intrusion or
extrusion.
Uncontrollable Factors
There are certain other factors that are not under the
control of the orthodontist. For example, the movement of
the lips depends on muscles that are generally not under
the influence of an orthodontist. Tjan, Miller, and The
categorized the movement of the upper lip into high, medium
and low smile lines.17 In a high smile line, a contiguous
band of maxillary gingiva is exposed, in a medium or
average smile line 75-100% of the central incisor crown
height is shown, and in a low smile line, 75% or less of
the clinical crown height of the central incisor is
revealed. Sex differences have been found.
When looking at
lift of the upper lip on smiling, females tend to exhibit
medium and high smile lines , while men show more medium
and low smile lines.18 Ageing which is an inevitable
outcome, changes the smile as well.
As an individual gets
older, the upper lip lengthens thus covering more maxillary
tooth structure and consequently revealing more mandibular
7
tooth structure.19
Zachrisson found that greater display of
mandibular teeth was an unattractive characteristic of
ageing.20
The Lips
The lips are the frames of the area in which the
orthodontist works.
The upper and lower lips effect how
much of the gingiva and teeth are seen.
Camara referred to
this as “labial unveiling,” while Ackerman and Ackerman
called it the “display zone.”2,
3
The movement of the lips depends on the muscles of
facial expression that cannot be effected through
conventional orthodontics.
The lower lip contraction
movements are controlled by risorius, mentalis triangularis
and quadratus.
The lower lip contraction can be
asymmetrical and affect the overall dental exposure.21
Upper lip curvature can also vary from patient to
patient. The upper lip can curve upwards, be straight, or
curve downwards. The prevalence of these in a normal
occlusion population was 12%, 45%, and 43% respectively.22
Harati et al. found no significant associations between the
upper lip curve types and Angle occlusion classes, however
they did find significant differences associated with
8
overbite and overjet.23 A downward lip curvature is deemed
less esthetic, however since it is a result of muscle
movement it is a limiting attribute the orthodontist has to
work around.22
Smile Type Based On Lip Movement
When studying lips and their movement during smiling,
Rubin identified and named three different types of
smiles.21 The first two smiles are characterized by the
manner of elevation of the upper lip.
When all of the
upper lip elevates evenly to expose the underlying dental
structures, it is termed a ‘cuspid smile.’
The upper lip
in a ‘commissure smile,’ or what some call the ‘Mona Lisa
smile,’ will elevate after the commissures at the corner of
the mouth first extend outwards and then lift upwards.
In
contrast, the movements of both the upper and lower lip
characterize the third type of smile.
In the ‘complex
smile,’ the action of the upper lip is the same as in the
cuspid smile, while the lower lip in a similar manner
depresses synchronously with the upper lip. Figures 2.1,
2.2, and 2.3 demonstrate these types of smiles.
9
Figure 2.1. Cuspid Smile
Figure 2.2. Commissure Smile
Figure 2.3. Complex Smile
Though Rubin had described a smile type in which the
movement of the lower lip is important, it is often
forgotten or not given much importance. In “The Eight
Components of a Balanced Smile” the actions of the upper
lip is repeatedly mentioned, while there is no mention of
the movements of the lower lip.11
10
As mentioned previously, another way to classify a
smile in regards to lip movement is the amount the upper
lip elevates and exposes the maxillary incisors. A ‘low
smile’ line shows 75% or less of the maxillary incisors, an
‘average smile’ line reveals 75% to 100% of the maxillary
incisor crowns, and finally a ‘high smile’ line displays
gingiva above the incisors.17 A high smile line with a large
amount of gingiva showing has been shown to be associated
with a greater muscular ability to elevate the upper lip
and with anterior vertical excess.18,
24
Zachrisson points
out that it is quite important to take into consideration
these smile lines during treatment to try to improve the
vertical relationship of the teeth to the resting lip
position.20 Intruding maxillary incisors as opposed to
extruding posterior teeth in order to correct a deep bite
in a patient with a low smile line would be detrimental,
while in a high smile line it would be beneficial.
Facial Types
It is commonly accepted that there are three facial
types centered on vertical parameters when comparing to
what is considered standardized normal.
They have however,
been referred to with various different labels.
Examples
include, hypodivergent-neutral-hyperdivergent, long-medium-
11
short, euryprosopic-mesoprosopic-leptoprosopic, and at
times incorrectly employed brachycephalic-mesocephalicdolichocephalic.25
Facial Type Characteristics
Mesoprosopic faces average normal vertical facial
heights and widths and have the ideal proportions, while
the other two types present with their own characteristics.
Euryprosopic faces often present with a tendency for a
horizontal growth pattern, longer ramus heights, lower
mandibular plane angles, lower total facial heights, and
lower gonial angles.
Leptoprosopic faces on the other
hand, often exhibit vertical growth patterns, have short
ramus heights, higher mandibular plane angles, greater
total facial heights, greater lower facial heights, and
larger gonial angles.26,
27
The skeletal patterns of each facial type have been
widely studied. Possible soft tissue associations however,
have not been as prolifically discussed and studied.
Martins and Vigorito used cone-beam CT to assess a
variety of facial soft tissue features.28 They found that
the upper lip vermillion height was significantly greater
for euryprosopic subjects when compared to the other two
12
facial types. Mesoprosopic subjects had greater values in
this area when compared to leptoprosopic subjects. They
also reported significantly smaller teeth exposure area for
euryprosopic subjects with no significant differences in
this parameter between mesoprosopic and leptoprosopic
subjects.
Hosseinzadeh-Nik et al. did look into correlations of
the smile line with parameters of anterior facial height.29
In their study, measurements were done utilizing a caliper
chair side. Among other results, they found positive
correlation relationships between anterior facial height
with both interlabial gap and distance between maxillary
incisal edge to lower lip. Frankfort Mandibular-Plane Angle
(FMA) was also reported to have a significant association
with interlabial gap on smile. Another group from India
also evaluated some similar parameters of the posed smile
by using standardized photographs.30
Records for Smile Diagnosis and Evaluation
The records that orthodontists take on their patients
pretreatment to study the smile and occlusion and to
diagnose have evolved, as has the type of records
researchers use in their studies.
As mentioned before,
with time the composite photos highlighting different
13
facial views were commonly taken alongside the already
popular lateral cephalograms.
With the emergence of new
technologies, new ways to view and analyze the smile have
developed.
Ackerman et al. developed and first introduced the
SmileMesh (TDG Computing, Philadelphia, Pennsylvania, USA)
program in 1998.31 The program allows lip-tooth
relationships to be measured by overlaying a grid over
imported smile photos. This however, is still twodimensional while the patients live in a three-dimensional
world.
CT imaging became popular and has improved since the
1980s.32
The emergence of cone-beam computed tomography
(CBCT) scans in orthodontics allowed the profession to
further step into the three dimensional world. Before this,
three-dimensional visualization was limited to study
models. Though able to be employed for a myriad of uses,
such as visualizing an impacted canine, it still comes with
a dose of radiation that one may want to avoid if just
evaluating external soft tissue parameters. Cone beams have
also been reported to not be very accurate when it comes to
soft tissue imaging.33
14
Three-dimensional scanning systems were designed to be
able to take three-dimensional facial surface scans.
Several types employing different technical methods have
emerged such as structured light that projects a pattern
onto a surface, laser scanning, and stereophotogrammetry
that uses images with slight differences in viewpoints.34
The optic system is in the structured light category and
employs white light from diodes that pose no known harms to
the patient.35 One of these systems is the Morpheus3d
(version 2.0; Morpheus, Seoul, Korea) software that will be
utilized in this study.
Morpheus3d
This particular scanner and software was used
successfully in prior studies looking at soft tissue
changes following orthognathic surgery.35 This 3d white
light scanner uses a spatial encoding method where 256
split planes are acquired by 8 images being taken in 0.8
seconds. Three separate shots are taken of the subject. The
front, left, and right images are then used to produce one
final output image of the face.
15
Smile Reproducibility
When doing any analysis on the smile it is important
to have a reproducible smile which captures the true
representation of that smile. Past studies have looked into
the stages of the smile, and investigated which was more
reproducible.
Two distinct stages of the smile were identified. The
first, which now is referred to as the ‘posed smile’ is
characterized by the upper lip rising to the nasiolabial
fold. When the levator labii superiories muscles,
zygomaticus major and the buccinators get involved the
second stage of smiling is reached. This is referred to as
the ‘unposed smile’ or in some cases the ‘dynamic smile’
and goes along with squinting of the eyes.31,
36
Though the
unposed smile is considered more dynamic and conveys the
true emotions of a person, it is generally involuntary. The
posed smile has been shown to be more reproducible and
voluntary, thus is the more studied of the two smiles.10,
31,
37
Walder et al. found that objective measures of the
posed smile was reproducible when captured in either still
pictures or videography, when given a verbal or visual cue,
or at day 1 or day 2.37 To capture the posed smile, the
16
verbal instruction given to the participants was to “give a
nice, big smile, one that shows your teeth.” It is to be
noted however, that in their study they also found that
practitioners preferred a dynamic video of a patient
smiling for diagnostic information over still photography.
Summary and Statement of Thesis
In orthodontics today, evaluating the smile as a whole
is an important step in diagnosis and treatment. The
orthodontist can be aware of how to place teeth most
optimally in the soft tissue framework, and know what the
limitations are if he adequately diagnoses all parameters
of the smile. He can then communicate this to the patient
so that the patient knows what can be expected from
treatment.
Though the associations between cephalometric
measurements and occlusions have long been widely studied,
less attention has been given to possible associations
between hard tissue characteristics as quantified by
cephalometrics and the soft tissue parameters of the smile.
The purpose of this study is to measure parameters of
the posed smile three dimensionally and see if there are
17
any correlations with vertical cephalometric skeletal
measurements.
18
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smile lines. Dental Press Journal of Orthodontics
2010;118-31.
3. Ackerman MB, Ackerman JL. Smile analysis and design in
the digital era. J Clin Orthod 2002;221-36.
4. Angle EH. Treatment of malocclusion of the teeth.
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dental manufacturing Co.; 1907.
5. Broadbent BH. A new x-ray technique and its application
to orthodontia. The Angle Orthodontist 1931;45-66.
6. Gosney MB. An investigation into some of the factors
influencing the desire for orthodontic treatment. Br J
Orthod 1986;87-94.
7. Davis NC. Smile design. Dent Clin North Am 2007;299-318.
8. Sarver D, Jacobson RS. The Aesthetic Dentofacial
Analysis. Clinics in Plastic Surgery 2007;369-94.
9. Grammer K, Thornhill R. Human (Homo sapiens) facial
attractiveness and sexual selection: the role of
symmetry and averageness. J Comp Psychol 1994;233-42.
10. Sarver DM. The importance of incisor positioning in the
esthetic smile: the smile arc. Am J Orthod Dentofacial
Orthop 2001;98-111.
11. Sabri R. The eight components of a balanced smile. J
Clin Orthod 2005;155-67.
12. Cooper GE, Tredwin CJ, Cooper NT, Petrie A, Gill DS.
The influence of maxillary central incisor height-towidth ratio on perceived smile aesthetics. Br Dent J
2012;589-99.
19
13. Ioi H, Nakata S, Counts AL. Influence of gingival
display on smile aesthetics in Japanese. Eur J Orthod
2010;633-7.
14. Martin AJ, Buschang PH, Boley JC, Taylor RW, McKinney
TW. The impact of buccal corridors on smile
attractiveness. Eur J Orthod 2007;530-7.
15. Schabel BJ, Franchi L, Baccetti T, McNamara JA.
Subjective vs objective evaluations of smile
esthetics. Am J Orthod Dentofacial Orthop 2009;72-9.
16. Kokich VO, Jr., Kiyak HA, Shapiro PA. Comparing the
perception of dentists and lay people to altered
dental esthetics. J Esthet Dent 1999;311-24.
17. Tjan AH, Miller GD, The JG. Some esthetic factors in a
smile. J Prosthet Dent 1984;24-8.
18. Peck S, Peck L, Kataja M. The gingival smile line.
Angle Orthodontist 1992;91-100.
19. Vig RG, Brundo GC. The kinetics of anterior tooth
display. J Prosthet Dent 1978;502-4.
20. Zachrisson BU. Esthetic factors involved in anterior
tooth display and the smile: vertical dimension. J
Clin Orthod 1998;432-45.
21. Rubin LR. The anatomy of a smile: its importance in the
treatment of facial paralysis. Plast Reconstr Surg
1974;384-7.
22. Dong JK, Jin TH, Cho HW, Oh SC. The esthetics of the
smile: a review of some recent studies. Int J
Prosthodont 1999;9-19.
23. Harati M, Mastofi SN, Jalalian E, Rezvani G. Smile line
and occlusion: An epedemiological study. Dent Res
J(Isfahan) 2013; 723-7.
24. Mack MR. Perspective of facial esthetics in dental
treatment planning. J Prosthet Dent 1996;169-76.
20
25. Franco FC, de Araujo TM, Vogel CJ, Quintao CC.
Brachycephalic, dolichocephalic and mesocephalic: Is
it appropriate to describe the face using skull
patterns? Dental Press J Orthod 2013;159-63.
26. Siriwat PP, Jarabak JR. Malocclusion and Facial
Morphology Is there a Relationship? Angle Orthod
1985;127-38.
27. Fields HW, Proffit WR, Nixon WL, Phillips C, Stanek E.
Facial pattern differences in long-faced children and
adults. Am J Orthod 1984;217-23.
28. Martins
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smile,
Dental
LF, Vigorito JW. Cone beam tomographic study of
structures characteristics at rest and wide
and their correlation with the facial types.
Press J Orthod 2013;38-44.
29. Hosseinzadeh-Nik T, Yazdani-Damavandi L, Kharazi-Fard
MJ. The correlation of smile line with the vertical
cephalometric parameters of anterior facial height.
Journal of Dentistry, Tehran University of Medical
Sciences 2005;21-8.
30. Krishnan V, Daniel ST, Lazar D, Asok A.
Characterization of posed smile by using visual analog
scale, smile arc, buccal corridor measures, and
modified smile index. Am J Orthod Dentofacial Orthop
2008;515-23.
31. Ackerman JL, Ackerman MB, Brensinger CM, Landis JR. A
morphometric analysis of the posed smile. Clin Orthod
Res 1998;2-11.
32. Moss JP. The use of three-dimensional imaging in
orthodontics. European Journal of Orthodontics
2006;416-25.
33. Nahm KY, Kim Y, Choi YS, Lee J, Kim SH, Nelson G.
Accurate registration of cone-beam computed tomography
scans to 3-dimensional facial photographs. Am J Orthod
Dentofacial Orthop 2014;256-64.
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Graber LW, Vanarsdall RL, Jr., Vig KWL. Orthodontics
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Philadelphia: Elsevier; 2012.
21
35. Kim SJ, Choi JY, Baek SH. Evaluation of canting
correction of the maxillary transverse occlusal plane
and change of the lip canting in Class III two-jaw
orthognathic surgery. Angle Orthod 2012;1092-7.
36. Peck S, Peck L. Selected aspects of the art and science
of facial esthetics. Semin Orthod 1995;105-26.
37. Walder JF, Freeman K, Lipp MJ, Nicolay OF, Cisneros GJ.
Photographic and videographic assessment of the smile:
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2013;793-801.
22
CHAPTER 3: JOURNAL ARTICLE
Abstract
Purpose: The purpose of this study is to measure parameters
of the posed smile and see if there are any correlations
with cephalometric skeletal measurements. Materials and
Methods: Pretreatment records from a sample of 110
Caucasian female subjects between the ages of 12 and 18
were gathered. The measurements of SN-GoGn, anterior facial
height, and lower and upper facial height percentages were
obtained from tracing lateral cephalograms. Superimposing
the repose and posed smile facial scans allowed for
measurements to be obtained showing the movements in x,y,
and z dimensions of the upper and lower lips, commissures,
and Cupid’s bows. Correlations and multiple linear
regression analyses were run to check for associations and
predictive relationships between the cephalometric skeletal
measurements and soft tissue change. Results: There were
significant moderate correlations and weak correlations
found. Significant multiple regression models were found
for intercommissural width, smile index, and the lower lip
in the y and z dimensions. Conclusions: There were moderate
correlations showing that as SN-GoGn and anterior facial
height increased, the interlabial gap increased as smile
23
index decreased. Significant relationships were found
between certain hard tissue cephalometric measurements and
the width of the smile as well as with the movements of the
lower lip.
24
Introduction
The smile is an important part of social interaction.
Smiles project a variety of positive emotions such as
happiness, approval, and humor.
An esthetically pleasing
smile may improve a person’s confidence in social
situations.
Therefore it may not be surprising that one of
the main reasons younger children and their parents seek
orthodontic care has been reported to reduce teasing.1
As patients become more concerned with the esthetics
of their smile, it has become more relevant for
orthodontists to pay attention to the soft tissue
framework.
It would be prudent to evaluate the parameters of a
smile before treatment in order to know not only what needs
to be done, but also what can be done, and to communicate
that with the patient and or parent.2,
3
Ackerman and
Ackerman point out that when one analyses a smile,
compromises between the opposing factors of esthetic goals
and the patients’ physiologic limitations are often made.3
Though the associations between cephalometric
measurements and clinical observations have long been
studied, less attention has been given to possible
25
associations between hard tissue characteristics as
quantified by cephalometrics and the soft tissue
characteristics of the smile.
The purpose of this study is to see if there are any
correlations present between the soft tissues of the posed
smile and cephalometric skeletal measurements, in order to
see if there may be any inherent differences in the lip
movement during smile based on the skeletal pattern.
Materials and Methods
Sample
A sample of 110 subjects was selected from the
pretreatment records at the orthodontic department at Saint
Louis University Center for Advanced Dental Education. The
records used for this study all came from the initial
records that were taken following the initial diagnostic
protocol of the clinic.
Subjects were selected based on the following
inclusion criteria: 1) Caucasian, 2) female 3) between the
ages of 12 and 18 at the time of initial records. The
exclusion criteria was: 1) previous orthodontic treatment
2) appliances on the dentition 3) craniofacial
abnormalities.
26
The average age of the 110 subjects in the study was
14.05 ± 1.65 years.
Methodology
To obtain the skeletal landmark measurements initial
digital lateral cephalograms were taken with a Carestream
9300 radiography unit (Carestream Health, CS9300 Rochester,
NY, USA). They were then uploaded and traced in the Dolphin
Imaging Software (Dolphin Imaging, Version 11.0,
Chatsworth, Ca, USA). Each cephalogram was traced by the
principal investigator. For each of the cephalograms, the
following 6 hard tissue anatomical landmarks were located
1) Sella 2) Nasion 3) Gonion 4) Gnathion 5) Menton 6) ANS.
The definitions of these landmarks can be viewed in the
Appendix Table A.1. The diagram of their locations can be
found in Figure 3.1. Using these landmarks the following
measurements were recorded 1) Mandibular plane (SN-GoGN)
2) Anterior facial height (Na-Me) 3) Upper facial height as
a percentage 4) Lower facial height as a percentage. The
definitions of these measurements are found in Table 3.1.
27
Figure 3.1. Landmarks located
28
Table 3.1. Cephalometric Lines/Measurements and Definitions
Abbreviation Landmark
SN-GoGn
SellaNasionGonionGnathion
AFH
Anterior Facial
Height
UFH%
LFH%
Definition
Angle derived from the
bisection of the line
connecting the landmarks
Sella and Nasion and the
line connecting the
landmarks Gonion and
Gnathion
Millimetric measurement
of the line connecting
the landmarks Nasion and
Menton
Upper Facial Height
as a percentage
Lower Facial Height
as a percentage
(N-Ans)/(N-ANS+ANS-Me) *
100
(ANS-Me)/(N-ANS+ANS-Me)
*100
Each subject had a three-dimensional soft tissue
facial scan in repose and in posed smile taken by the same
technician utilizing the Morpheus 3d scanner that were then
uploaded into the Morpheus3d software (Morpheus3d, version
2.0, Seoul, Korea). The patients were sat via a marker on
the floor at the recommended 60-70cm range from the
scanner. To obtain a posed smile the technician would
practice with the subject instructing them to smile big
with their teeth showing. On each scan, the following 6
soft tissue landmarks were digitized by the principal
investigator 1) Lip superior (Ls) 2) Lip inferior (Li) 3)
Commissure Right (CR) 4) Commissure Left (CL) 5)Cupid’s Bow
29
Right (CBR) 6) Cupid’s Bow Left (CBL). On each posed smile
scan, interlabial gap and intercommissural width were
identified. The definitions of these soft tissue parameters
can be found in Table 3.2. An example of a digitized scan
in repose and one in smile are shown in Figures 3.2 and 3.3
respectively. Using the Morpheus3d software, for each
subject the posed smile scan was superimposed on the repose
scan. The software employs the iterative closest point
algorithm for superimpositions. From the superimpositions,
the change for each point from repose to smiling was
recorded in the x, y, and z dimensions. An example of the
three dimensional Cartesian plane can be seen in Figure
3.4. Measurements were recorded from the posed smile scans
for interlabial gap and intercommissural width, and smile
index was calculated. These can be found in Table 3.3.
30
Table 3.2. Soft Tissue Landmarks and Definitions
Abbreviation Landmark
Definition
CBLx
CBLy
CBLz
Cupid's Bow
Left
(in the x,y and
z dimensions)
CBRx
CBRy
CBRz
Cupid's Bow
Right
(in the x,y and
z dimensions)
CLx
CLy
CLz
Commissure Left
(in the x,y and
z dimensions)
CRx
CRy
CRz
Commissure
Right
(in the x,y and
z dimensions)
Lix
Liy
Liz
Lsx
Lsy
Lsz
Lip Inferior
(in the x,y and
z dimensions)
Lip Superior
(in the x,y and
z dimensions)
31
The apex where the curve
of the vermillion border
of the lip coming from the
commissure meets the curve
of the vermillion border
coming up from the
philtrum on the left side
of the mouth
The apex where the curve
of the vermillion border
of the lip coming from the
commissure meets the curve
of the vermillion border
coming up from the
philtrum on the ride side
of the mouth
Corner of the left side of
the mouth where the
vermillion border of the
upper lip meets the
vermillion border of the
lower lip
Corner of the right side
of the mouth where the
vermillion border of the
upper lip meets the
vermillion border of the
lower lip
The most inferior point on
the midline of the lower
lip
The most superior point on
the midline of the upper
lip
Table 3.3. Measurements from Posed Smile
IG
ICW
SI
Interlabial Gap
Millimetric
measurement of the
line connecting the
most inferior portion
on the midline of the
upper lip and the
most superior point
on the midline of the
lower lip.
Millimetric
measurement of the
Intercommissural line connecting the
Width
right and left
commissures of the
mouth
Smile Index
ICW÷IG
32
Figure 3.2. Soft Tissue Scan in Repose
33
Figure 3.3. Soft Tissue Scan in Posed Smile
34
Figure 3.4. Three Dimensional Cartesian Plane
Statistical Analysis
All descriptive data and statistical analysis was done
with the Statistical Package for the Social Science (IBM
SPSS, Version 20, Armonk, NY, USA). The study tested the
null hypothesis that there are no relationships present
35
between the cephalometric skeletal measurements and the
soft tissue characteristics of the smile. Pearson
Correlation Coefficients were generated to see if there
were any associations present. Multiple linear regression
analysis was used to test for relationships among the
variables, with a p value less than .05 being significant.
Since one of the assumptions for multiple linear regression
is that there are no outliers, each dependent variable
measurement set was checked for outliers and if found the
individual measurement from that subject was dropped from
the analysis.
Reliability
Intra-class correlations greater than or equal to 0.80
are considered to be adequately reliable. Ten percent of
the lateral cephalograms and soft tissue scans were
randomly selected and re-measured by the principal
investigator to test for intra-examiner reliability. All
measurements in both the cephalograms and the soft tissue
facial scans yielded a Cronbach’s alpha well above 0.80.
This demonstrates that the original and repeated
measurements showed an acceptable level of consistency when
looking at the examiner’s landmark location identification.
36
Results
Correlations
Significant Pearson’s Correlations with a ‫׀‬r‫>׀‬0.7 are
considered strong correlations. A correlation with a ‫׀‬r‫׀‬
between 0.3-0.5 is considered moderate in strength, while a
weak correlation will yield a ‫׀‬r‫ ׀‬in the range of 0.1-0.3.
This study did not yield any significant correlations that
were in the strong range. The significant Pearson’s
Correlations that were found in this study are summarized
in Table 3.4 and 3.5 below, with the corresponding
scatterplots of the moderate strength correlations shown in
Figures 3.5-3.8.
Table 3.4. Significant correlations between vertical
variables and soft tissue parameters of the smile showing
moderate strength of association
r-value
SNGoGn-Smile Index
-0.399
AFH-Interlabial Gap
+0.399
AFH-Smile Index
-0.368
SNGoGn-Interlabial Gap
+0.366
p<.05 (two-tailed)
37
Figure 3.5. Scatterplot of mandibular plane (SN-GoGn)and
Smile Index (SI) for each subject in the study
Figure 3.6. Scatterplot of Anterior Facial Height (AFH) and
Interlabial Gap (IG) for each subject in the study
38
Figure 3.7. Scatterplot of Anterior Facial Height (AFH) and
Smile Index (SI) for each subject in the study
Figure 3.8. Scatterplot of mandibular plane (SN-GoGn) and
Interlabial Gap (IG) for each subject in the study
39
Table 3.5. Significant correlations between skeletal
vertical variables and soft tissue parameters of the smile
showing weak strength of association
r-value
UFH%-IG
-0.288
LFH%-IG
0.288
UFH%-CLx
-0.253
LFH%-CLx
0.253
UFH%-Liz
0.251
LFH%-Liz
-0.251
UFH%-Liy
-0.246
LFH%-Liy
0.246
UFH%-CRx
-0.222
LFH%-CRx
0.222
UFH%-CLz
0.230
LFH%-CLz
-0.230
UFH%-Lsz
0.227
LFH%--Lsz
-0.227
UFH%-CBRz
0.190
LFH%-CBRz
-0.190
AFH-CLz
-0.221
UFH%-CBLz
0.215
LFH%-CBLz
-0.215
AFH-Liy
0.192
SNGoGn-CLx
0.189
p<.05 (two-tailed)
Multiple Linear Regression Analysis
Multiple linear regression analyses were run to see if
there were any significant relationships where the
cephalometric skeletal measurements could be used to
predict the individual soft tissue smile landmark
movements. The significant findings are shown in Tables
3.6-3.7.
40
Table 3.6. Significant multiple linear regression results
Independent Dependent
Variable
Variable
SNGoGn
AFH
SNGoGn
LFH%
UFH%
AFH
F Value
R
Square
Adjusted
R Square
p
ICW
4.577
0.115
0.090
0.005
SI
7.836
0.183
0.160
0.000
Liy
2.766
0.073
0.046
0.045
Liz
2.862
0.075
0.049
0.040
Table 3.7. Multiple linear regression equations
Equation
Intercommissural Width'= 28.5-0.3(SNGoGn)+0.2(AFH)
Smile Index'= 13.1-0.1(SNGoGn)
Liy'= -16.2+0.3(LFH%)-0.3(UFH%)
Liz'= 11.8+0.3(LFH%)-0.3(UFH%)
Discussion
In orthodontics, considerable attention has been
placed on evaluating and correcting not only malocclusions
of the dentition and unharmonious skeletal relationships,
but also the overlying soft tissue.4-8 Many studies have
been done looking at relationships between hard tissue
measurements in the vertical dimension and certain
malocclusions, such as the association of posterior
maxillary vertical excess and open bites.9,
10
More recently,
investigators have started to focus on whether any
41
associations are present between the hard tissue
measurements and the soft tissues.11 Since the lips are a
prominent factor in a smile, this study aimed to see if
there was any relationships present between vertical hard
tissue measurements and movement of the lips when smiling.
Since most people do not consciously think of how they
are moving their lips when they smile, the movement of the
lips and how they frame the smile can be considered a
limiting factor in orthodontic treatment. It can be pointed
out however, that in the study by Lin et al. the
participants were trained to be able to produce certain
type of smiles in order to measure facial muscle activity.12
Several Pearson’s correlations were found to be
significant, though none in this study were at a very
strong level. The moderate correlations showed that as
mandibular plane (SN-GoGn) or anterior facial height
increased, the interlabial gap increased while the smile
index decreased. Since the interlabial gap is the
denominator in the smile index equation, it would be
expected that it would decrease if interlabial gap was
increasing. This was similar to the findings of
Hosseinzadeh-Nik et al. In their study they found positive
significant correlations between anterior facial height and
42
the angular measurement of Frankfort Mandibular Plane Angle
and Y-axis with interlabial gap.11
The majority of the significant weak correlations
found in this study were with upper and lower facial height
percentages. Generally the associations showed as lower
facial height percentage increased, interlabial gap
increased, the lower lip depressed (Liy) more and went
backwards (Liz) more, the upper lip (Lsz) and both cupid’s
bows (CBRz,CBLz)also went backwards more. It is to be
expected that the opposite associations were found with
upper facial height percentage because whenever lower
facial height percentage increases, upper facial height
percentage decreases by the same magnitude.
Though both individual commissures (CRx,CLx)showed a
positive association where they would go greater sagittal
distances as lower facial height percentage increased,
overall intercommissural width did not show a significant
correlation with lower facial height percentage. This may
suggest a prevalence of asymmetry between the two sides of
the commissures during smile within subjects. Facial
movement studies have found that lip corner movements are
more asymmetric in deliberate smiles than spontaneous
smiles.13,
14
Overall, facial asymmetry occurs to a greater
43
extent in emotional rather than neutral responses and posed
emotional responses rather than spontaneous emotional
responses.14 Finally, though overall facial asymmetry is
usually more on the left side due to the right cerebral
hemisphere influence, right side asymmetry has been found
in positive emotional expressions.15
Through multiple linear regression analysis,
significant predictive equations were found for several
soft tissue dependent variables. As intercommissural width
(ICW) increased by 1.0mm, mandibular plane (SN-GoGn)
decreased by 0.3 degrees and anterior facial height (AFH)
increased by 0.2mm . Anterior facial height is measured in
millimeters, thus it is to be taken into consideration that
some of the positive correlation between intercommissural
width and anterior facial height could be due to some
subjects being simply larger as a whole when compared to
norms. Higher smile index ratios correspond to smiles with
greater horizontal components and less vertical components.
As the smile index (SI) increased by one, the mandibular
plane (SN-GoGn) decreased by 0.1 degrees. Though this study
did not divide subjects into facial type groups this
overall picture corresponds well with Martins and
Vigorito’s study which found that euryprosopic face types
44
had greater sagittal lip contraction resulting in narrower
smiles.16 Interestingly in our study, the movement of the
lower lip, not the upper lip, had relationships with the
cephalometric skeletal measurements. The lower lip would
depress (Liy) 1.0mm more for every increase of 0.3 percent
units of lower facial height percentage (LFH%) and decrease
of 0.3 percent units of upper facial height percentage
(UFH%). Finally, the lower lip upon smiling would go
backwards (Liz) 1.0mm for every increase of 0.3 percentage
units of lower facial height(LFH%) and decrease of 0.3
percentage units of upper facial height (UFH%). The R
square values though significant, ranged from .073 to .183
suggesting that these regression models do not explain a
large amount of the variance of the response data around
the mean, or in other words that the data was not tightly
fit to the linear regression line.
Since the literature in orthodontics focuses a good
amount on the upper lip, this study suggests that it may be
worthwhile to pay attention to the lower lip since its
overall amount of movement may differ as lower facial
height percentage varies and can affect the shape of the
display zone. The lower lip depressing more can lead to
more of the mandibular incisors being exposed which has
45
been shown to be viewed as less attractive by both
orthodontists and laypersons, and is also associated with a
more aged look.17-19 In the future one could look to see if
there are any changes in the lower lip at smile after
vertical chin reduction surgery.
In prosthodontic literature, the effects of occlusal
vertical dimension on lip positions at smile have been
investigated. Chou et al. found that as they increased
vertical occlusal dimension with bite registrations in
dental students with full complements of dentition no
effect was had on maxillary gingival display or buccal
corridor display, but rather the lower lip shifted downward
and consequently the interlabial gap increased while the
smile index decreased.20 It may be worthwhile in a future
study to include the posterior occlusal vertical
measurement.
Since this study was a cross-sectional study, future
studies that would equalize the number of subjects falling
into different vertical groups by dividing the subjects
into facial types could possibly lead to new findings or
stronger relationships to be detected.
Using the three-dimensional scanning system in this
study came with several advantages. Unlike other setups,
46
natural head position during image acquisition does not
have to be accounted for like it does in photography for
instance, thus removing that parameter from overall error,
and allowing the patient to be more comfortable and natural
by not having to have their head in a contraption when
attempting to smile naturally. Unlike cone-beam tomography,
the optic white light technology in this system poses no
hazardous risk for the subjects. Some studies have employed
calipers to measure directly on the soft tissue however,
this could lead to some error due to possible soft tissue
distortion.11,
21
The white light scanning system takes only
0.8 seconds to take one scan, unlike its laser counterpart
which takes approximately 25.6 seconds per scan.
47
Conclusions
According to the results within the context of this
study we can conclude the following:
1. There were moderate correlations showing that as
mandibular plane (SN-GoGn) and anterior facial
height increased, the interlabial gap increased as
smile index decreased.
2. Relationships existed where intercommissural width
increased as Sn-GoGn decreased and anterior facial
height increased, where smile index increased as
mandibular plane
(SN-GoGn) decreased, where the
lower lip depressed more as lower facial height
increased and upper facial height decreased, and
where the lower lip moved backwards more as lower
facial height increased and upper facial height
decreased.
48
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51
Appendix
Table A.1. Cephalometric Landmarks and Definitions
Abbreviation Landmark
ANS
Anterior
Nasal
Spine
Gn
Gnathion
Go
Gonion
Me
Menton
N
Nasion
S
Sella
Definition
The tip of the median, sharp
bony process of the maxilla at
the lower margin of the anterior
nasal opening
Midpoint between the most
anterior and inferior point on
the bony chin
The midpoint of the angle of the
mandible corresponding to the
most convex point along the
inferior border of the ramus
The most inferior point on the
symphyseal outline
The junction of the frontonasal
suture at the most posterior
point on the curve at the bridge
of the nose
The center of the pituitary
fossa of the sphenoid bone
52
VITA AUCTORIS
Eniko Katalin Toth was born in Budapest, Hungary on
January 29th, 1986 to Zoltan and Marianna Toth. She is the
middle of three children, having one older sister and a
younger brother.
She grew up in Miami, Florida and stayed there to
attend the University of Miami where she received a
Bachelor’s of Science degree in the concentration of
Neuroscience in 2008.
Following her undergraduate years, Eniko attended the
University of Florida for her Doctor of Dental Medicine
degree in Gainesville, Florida until 2012.
She now resides in Saint Louis, Missouri where she
attends Saint Louis University. At the completion of her
Orthodontic residency in December 2014, she will have
gained a Master of Science in Dentistry degree along with
her Orthodontic certificate. Eniko upon graduation plans to
leave Missouri and practice orthodontics full time as an
associate.
53