Thesis: A study of gummy smile in a Tunisian orthodontic population.

UNIVERSITY OF MONASTIR
FACULTY OF DENTAL MEDICINE OF MONASTIR
Year 2017 Thesis N°.....
THESIS
FOR THE NATIONAL DIPLOMA OF DOCTOR OF
DENTAL MEDICINE
Presented and defended publicly on 17/07/2017
BY
Errebai Rania
Born on 10/04/1991 in Mahres
A study of gummy smile in a Tunisian
orthodontic population
Thesis reviewers
JURY :
President:
Assessors:
Pr. Abdellatif BOUGHZALA
Pr. Anissa EL YEMNI ZINELABIDINE
Pr. Soumaya TOUZI
Dr. Sofien BEN ABDALLAH
Director
A. Pr. Ines DALLEL
Guest: Pr. Kamel BEN SALEM

AKNOWLEGEMENTS:
To our master and jury member
Professor Abdellatif BOUGHZALA
professor Anissa EL YEMNI ZINELABIDINE
professor Soumaya TOUZI
doctor Sofien BEN ABDALLAH
You honoured us by being jury members of our thesis and judging this humble work. And for
this, we are sincerely grateful.
May you find here a testimony of our sincere gratitude, acknowledgements and deep respect.
To our thesis director
Professor Ines DALEL
I would like to express my sincere gratitude for your continuous support, patience, motivation,
enthusiasm, and immense knowledge. Your guidance helped me in all the time of research and
writing of this thesis. The door to your office was always open whenever I had a question about
my research or writing. Thank you for steering me in the right direction whenever I needed it.
To our master and guest
Professor Kamel BEN SALEM
I cannot be more grateful for your precious contribution in the statistical analysis. You
accepted to help us open-heartedly and every result described in this thesis was
accomplished thanks to your help. I sincerely appreciate the time you spent guiding me
and for this I am the most thankful.

Summery
Page 1
SUMMERY
list of figures............................................................................................................4
list of tables..............................................................................................................5
INTRODUCTION...................................................................................................7
1. Materials: .......................................................................................................8
2. Method: ..........................................................................................................9
2.1. Variables:...............................................................................................12
2.1.1. Clinical and occlusal parameters:....................................................12
2.1.1.1. Qualitative measurements: ........................................................12
2.1.1.2. Quantitative variables:...............................................................14
2.1.2. Cephalometric parameters:..............................................................18
2.1.2.1. Angular measurements:.............................................................19
2.1.2.2. Linear measurements:................................................................20
2.1.2.3. Ratio measurements:..................................................................21
2.2. Folders used for each measurement: .....................................................21
3. Statistical analysis:.......................................................................................24
1. Bivariate analysis interpretation: .................................................................25
1.1. Clinical and occlusal parameters:..........................................................25
1.1.1. Qualitative parameters: ...................................................................25
1.1.1.1. Smile type:.................................................................................25
1.1.1.2. Gender: ......................................................................................25
1.1.1.3. Facial type :................................................................................26
1.1.1.4. Facial symmetry : ......................................................................27

Summery
Page 2
1.1.1.5. Facial thirds : .............................................................................27
1.1.1.6. Smile point:................................................................................28
1.1.1.7. Profile : ......................................................................................29
1.1.1.8. Relationship between upper lip’s thickness, lower lip’s
thickness and chin’s thicknesses:..............................................................29
1.1.1.9. The cervical line: .......................................................................30
1.1.1.10. Upper lip frenum’s situation:...................................................30
1.1.1.11. Upper lip line:..........................................................................31
1.1.1.12. Incisal edge's parallelism with pupillary line:.........................32
1.1.1.13. Angle’s canine class: ...............................................................32
1.1.1.14. Angle’s molar class: ................................................................32
1.1.1.15. Cross bite:................................................................................33
1.1.1.16. Smile arch:...............................................................................33
1.1.1.17. Incisal midline: ........................................................................34
1.1.2. Quantitative parameters: .................................................................35
1.2. Cephalometric parameters:....................................................................39
2. Multivariate analysis:...................................................................................40
1. Autocriticism :..............................................................................................44
1.1. Choice of posed smile for our study: [6,8,9].........................................44
1.2. Positive points:.......................................................................................45
1.3. Limits of the study:................................................................................45
2. Discussion of the results: .............................................................................46
2.1. Clinical and occlusal parameters:..........................................................46
2.1.1. Qualitative parameters: ...................................................................46

Summery
Page 3
2.1.2. Quantitative variables:.....................................................................51
2.2. Cephalometric parameters:....................................................................58
2.2.1. Angular measurements:...................................................................58
2.2.2. Linear measurements:......................................................................60
2.2.3. Ratio measurements: .......................................................................62
2.3. Multivariate approach:...........................................................................64
3. Treatment recommendations:.......................................................................65
3.1. Treatment options for Grade 1 patients:................................................65
3.2. Treatment options for Grade 2 patients:................................................66
CONCLUSION .....................................................................................................67
References .............................................................................................................69
ANNEX .................................................................................................................75

List of figures
Page 4
LIST OF FIGURES
Fig 1: The digital camera used in the study. ...........................................................8
Fig 2: AF-S DX NIKKOR 16-85mm F3.5-5.6G ED VR lens................................8
Fig 3: The graphic design software used to take the measurements.......................9
Fig 4: The device used as a reference to photograph the subjects. .......................10
Fig 5: Frontal picture at rest with the device in front of the patient’s face...........11
Fig 6: Frontal picture during smile with the device in front of the patient’s face.11
Fig 7: Frontal picture at rest without the device....................................................11
Fig 8: Frontal picture during smile without the device.........................................11
Fig 9: Side picture at rest position.........................................................................11
Fig 10: Diagram of the studied variables. .............................................................12
Fig 11: Nasolabial angle measured by the software..............................................14
Fig 12: Distance between the ala of the nose and intercommissural distance
measured by software............................................................................................15
Fig 13: Upper lip length at rest measured using the software...............................15
Fig 14: The distance from upper lip stomion to incisal edge measured by the
software. ................................................................................................................16
Fig 15: Measurement of upper lip to upper incisal edge at rest, upper lip, lower
lip and chin’s thickness on lateral radiograph.......................................................17
Fig 16: Measurement of gum exposure [6]. ..........................................................17
Fig 17: Width/length ration’s normal values on an upper central incisor [2].......18
Fig 18: The angular measurements. ......................................................................19
Fig 19: Linear dento-alveolar and skeletal variables. ...........................................20
Fig 20: Smile type distribution in the sample. ......................................................25
Fig 21: Gender distribution in the sample.............................................................26
Fig 22: The ROC curve resuming our equation....................................................42

List of tables
Page 5
LIST OF TABLES
Tab I: Measurements that were digitally taken with Corel Draw x8.0.................22
Tab II: Measurements that were taken from pictures............................................22
Tab III: Variables that were taken from patient’s folders.....................................23
Tab IV: Crosstable between smile type and gender..............................................26
Tab V: Crosstable between facial type and smile type. ........................................27
Tab VI: Crosstable between facial symmetry and smile type...............................27
Tab VII: Crosstable between facial thirds and the smile line. ..............................28
Tab VIII: Crosstable between prominent third and the smile type. ......................28
Tab IX: Crosstable between the smile point and the smile type...........................28
Tab X: Crosstable between profiles’s form and smile type. .................................29
Tab XI: Crosstable between the relationship between upper lip’s thickness, lower
lip’s thickness and chin’s thicknesses and the smile type.....................................29
Tab XII: Crosstable between cervical line and smile type....................................30
Tab XIII: Crosstable between upper lip frenum’s situation and smile type. ........30
Tab XIV: Crosstable between upper lip line's parallelism with pupillary line and
smile type...............................................................................................................31
Tab XV: Crosstable between upper lip line's situation with the labial
commissures and smile type..................................................................................31
Tab XVI: Crosstable between incisal edge's parallelism with pupillary line and
Smile type..............................................................................................................32
Tab XVII: Crosstable between Angle’s canine class and smile type. ..................32
Tab XVIII: Crosstable between angle’s molar class and smile type. ...................33
Tab XIX: Crosstable between crossbite and smile type........................................33
Tab XX: Crosstable between smile arch’s parallelism with lower lip line and
smile type...............................................................................................................33
Tab XXI: Crosstable between smile arch’s situation and smile type. ..................34

List of tables
Page 6
Tab XXII: Crosstable between smile arch’s form and smile type. .......................34
Tab XXIII: Crosstable between the coincidence of upper and lower incisal
midlines and the smile type...................................................................................34
Tab XXIV: Crosstable between the coincidence of upper incisal midline with
facial midline and the Smile type..........................................................................35
Tab XXV: Cross table between the coincidence of lower incisal midline with
facial midline and the smile type...........................................................................35
Tab XXVI: Comparison of clinical and occlusal parameters per smile group. ....36
Tab XXVII: Comparison of cephalometric parameters per smile group..............39
Tab XXVIII: Multivariate analysis for the logistic regression model. .................41
Tab XXIX: observed and predicted percentages in the regression model............41
Tab XXX: Gummy smile group’s classification...................................................65

Introduction
Page 7
INTRODUCTION
Smile is the language of the soul. It is the expression of joy, happiness and
greeting. It reflects a good mood and a healthy psychological state.
A beautiful smile can influence a person’s social integration, professional and
personal success. It is a mean of communication and spiritual connection. Thus,
aesthetics is becoming a priority making people constantly seek for perfecting
their smiles.
The beauty of the smile depends on many factors such as teeth size, shape, color
and position, the amount of exposed gingiva and the framing of the lips [1].
Although displaying a certain amount of gingiva is accepted nowadays giving a
youthful appearance to its owner, an excessive gingival display is considered
unaesthetic [2,3]. This excess of gum exposure gives what we call a gummy
smile [4, 5,1].
Many previous studies, in other countries, were conducted to determine to factors
that influence a gummy smile. Consequently, we have decided to study gummy
smile in a Tunisian orthodontic population.
The main objectives of this work are to study the different parameters of gummy
smile in an orthodontic population, to evaluate the influence of the gummy smile
on the aesthetic parameters and to determine the clinical criteria and standards to
analyze the different types of the smile.
This work will be presented following the common organization structure
IMRaD. We will start by introducing our study. Then, we will develop our
materials and explain our method. After that, we will present our results. Finally,
we will discuss our findings and propose some clinical recommendations for
gummy smile correction.

Materials and method
Page 8
This study was conducted on an orthodontic population. The patients were
randomly selected from the dento-facial orthopaedics department in the dental
clinic of Monastir. The study lasted 4 months from January to April 2017.
All of the participants in the study consulted the department to improve their
smile. They were aware of the aim of the study as well as minor patients’ parents.
A written consent was obtained from the participants in accordance with the
guidelines of our institution.
All patients with a history of orthodontic treatment or under active orthodontic
treatment during the study as well as patients with prosthodontic restorations
visible on smiling or previous orthognathic surgery were excluded from the
study.
Type of the study:
It’s transversal comparative analytical study between two smile types (gummy
smile and non-gummy smile).
1. Materials:
Materials used in our study:
- A digital camera: Nikon D7100 with AF-S DX NIKKOR 16-85mm F3.5-5.6G
ED VR lens.
Fig 1: The digital camera used in the study.
Fig 2: AF-S DX NIKKOR 16-85mm F3.5-5.6G
ED VR lens.

Page 9
- A tripod.
- A device especially made for the study as a reference to have the same
framing for all patients.
- A graphic design software: Corel Draw x8 to take measurements from
patients’ pictures.
Fig 3: The graphic design software used to take the measurements.
- Patients’ orthodontic folders (documents used: clinical examination’s sheet,
lateral cephalogram radiographs and dental casts).
2. Method:
This study was conducted on 110 subjects randomly selected among patients who
consulted the clinic’s dentofacial orthodontics department before starting their
orthodontic treatment.
The patients were seated on an adjustable chair with their heads straight. In front
of them, we’ve placed the device that we made as our reference. The device was
made by a local carpenter and its conception was set according to our need. It’s

Page 10
constituted of a frame on which we’ve pasted a millimeter transparent paper. The
frame is fixed on a stick inside a slide that helps control the device’s length along
with the patient’s height (fig 4).
Fig 4: The device used as a reference to photograph the subjects.
The patients’ faces were placed 10 millimeters behind the millimeter’s paper to
avoid the steam. The camera was set on the tripod 1 meter from the patient’s face.
For each subject, 3 pictures were taken: one frontal picture at rest position, one
frontal picture during a natural posed smile and one side picture at rest position.
Pictures were taken twice: one with the device set and one without the device
keeping the head at the same position. They were all taken in the same
environment with the same lighting conditions. The pictures without the device
were taken with flash photography (fig5-9).

Page 11
Fig 5: Frontal picture at rest with the device in front of the
patient’s face.
Fig 6: Frontal picture during smile with the device in front of the
patient’s face.
Fig 7: Frontal picture at rest without the
device.
Fig 8: Frontal picture during smile
without the device.
Fig 9: Side picture at rest position.

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All of the pictures were uploaded on a computer and the pictures taken without
the device were processed with a graphic design software (Corel Draw X8) to be
able to take the measurements needed.
We started by taking our measurements from the pictures without the device. We
used a 50mm lens for the pictures so the values obtained with the software from
the pictures without the device were multiplied by 2 (Fig2). Then we compared
those numbers to the values obtained from the pictures with the device to make
sure that the software gives accurate measurements.
2.1.Variables:
For each subject, data were compiled for 87 variables divided into two categories:
Fig 10: Diagram of the studied variables.
2.1.1. Clinical and occlusal parameters:
Fourty six clinical and occlusal variables (17 qualitative and 29 quantitative)
were studied:
2.1.1.1. Qualitative measurements:
 Smile type: we divided the smiles into two categories: a smile was judged
gummy if a band of 2mm or more of contiguous gingiva is exposed and non-
gummy if less than 2mm are shown during smile.
Variables (77)
Clinical and
occlusal variables
(46)
Qualitative
variables (17) Quantitative
variables (29)
Cephalomteric
variables
(31)
Angular variables
(11)
Linear variables
(13)
Ratios (7)

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 Gender
 Facial type: 3 facial types Brachycephalic (square face)
Dolichocephalic (triangular face)
Mesocephalic (oval face)
(It was Judged clinically then confirmed by lateral cephalograms).
 Facial symmetry.
 Facial third equality: If unequal, the prominent third was mentioned.
 Smile point: the middle of the vertical line joining the pupillary line and the
chin line. It can be centered if it coincides with the upper labial point or
decentered if the opposite.
 Profile: it can be convex, concave or straight.
 Relationship between upper lip’s thickness, lower lip’s thickness and chin’s
thickness: all 3 thicknesses should be equal.
 Cervical line: defined as the line crossing the most apical points of the
gingival contour of the upper 4 incisors and the upper canines.
 Upper lip frenum’s situation.
 Upper lip line:
- Parallelism with pupillary line.
- Situation with labial commissures.
Incisal edge’s parallelism with pupillary line:
 Angle’s canine class.
 Angle’s molar class.
 Crossbite.
 Smile arch: it’s an imaginary line following the incisal edges if the maxillary
incisors.

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- Parallelism with lower lip line (consonant if it follows the lower lip line
curvature and non-consonant if the opposite).
- Situation.
- Form.
 Incisal midline:
- Coincidence of upper and lower incisal midline.
- Coincidence of upper incisal midline and lower incisal midline with facial
midline.
2.1.1.2. Quantitative variables:
 Age.
 Lower third’s length of the face: the distance from the subnasale to the chin.
 The two third of the lower third of the face’ length: distance from the lower
lip stomion to the chin.
 Nasolabial angle (fig 11).
Fig 11: Nasolabial angle measured by the software.
 Philtrum’s height: between the base of the nose and the vermilion border of
the upper lip

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 Commissural height: the distance between the commissures and their
projections on the horizontal line joining the alas of the nose
 Intercommissural distance at rest: the distance between the two angles of the
mouth (Fig 12).
 Philtrum’s width.
 The distance between the ala of the nose (Fig 12).
 Upper lip length at rest: between the base of the nose and the upper lip’s
stomion at rest position (Fig 13).
Fig 12: Distance between the ala of the nose and intercommissural distance measured by
software.
Fig 13: Upper lip length at rest measured using the software.

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 Upper lip height during smiling: measured during smile.
 Interlabial gap at rest.
 Upper lip to upper incisal edge at rest position: from upper lip’s stomion to
upper incisor’s edge at rest position (Fig 15).
 Upper lip to upper incisor edge during smiling: measured during smile (Fig
14).
Fig 14: The distance from upper lip stomion to incisal edge measured by the software.
 Upper lip’s thickness (Fig 15).
 Lower lip’s thickness (Fig 15).
 Chin’s thickness: between soft tissue pogonion and bony tissue pogonion (Fig
15).
 Exposed gingival height during smile: its value was calculated as the
difference between lip position and tooth length. When the gingival margin
was displayed, this measurement had a positive value. When the teeth
remained partly covered, a negative value was given to this variable (Fig 16).

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Fig 15: Measurement of upper lip to upper incisal edge at rest, upper lip, lower lip and
chin’s thickness on lateral radiograph.
Fig 16: Measurement of gum exposure [6].
 Clinical length of upper incisors: measured from the gingival margin to the
incisor’s edge.
 Clinical width of upper incisors: measured between the two contact points.
 Width/length ratio of upper incisors (Fig 17).

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Fig 17: Width/length ration’s normal values on an upper central incisor [2].
 Upper teeth exposure at rest: from upper lip’s lower edge to upper incisal edge
at rest. If the incisal edge is covered with the lower lip, the upper teeth
exposure will have the same value as the interlabial gap.
 Distance between upper central incisors: the horizontal distance from 11 to 12.
 Distance between upper lateral incisors: the horizontal distance from 12 to 22.
 Distance between upper canines: the horizontal distance from 13 to 23.
 Smile width: the horizontal distance between two vertical lines marking the
labial commissures during smiling.
 Buccal corridor space: the triangular space between the inner corner of the
mouth and the buccal surface of the last tooth clinically observed. Both right
and left corridor spaces were measured.
 Overjet.
 Overbite.
2.1.2. Cephalometric parameters:
Thirty-one cephalometric parameters were studied:

Page 19
2.1.2.1. Angular measurements:
Fig 18: The angular measurements.
 SNA: the angle between SN line and NA line.
 SNB: the angle between SN line and NB line.
 ANB: the difference between SNA and SNB angle.
 IMPA: the angle between the lower incisor’s big axis and the mandibular
plane.
 I/NA: the angle between upper incisal axis and NA line.
 i/NB: the angle between lower incisal axis and NB line.
 I/F: the angle between Frankfurt plane and upper incisor’s big axis.
 I/i: angle between the two big axes of upper and lower incisors.
 SN/GoGn: angle between GoGn plane and SN plane.
 SN/Occ: angle between occlusal plane and SN plane.
 SN/PP: the angle between palatal plane and SN plane.

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2.1.2.2. Linear measurements:
 AoBo: distance between A and B’ projections on the occlusal plan.
 I/NA: the distance between upper incisor’s labial face and perpendicular to
NA line.
 i/NB: the distance between lower incisor’s labial face and perpendicular to
NB line.
Fig 19: Linear dento-alveolar and skeletal variables.
 UADH (Upper anterior dental height): The perpendicular length from upper
incisor’s edge to palatal plane.
 UPDH (upper posterior dental height): The perpendicular length from the
mesial cuspid of the 6 to palatal plane.
 LADH (lower anterior dental height): The perpendicular length dropped from
lower incisor’s edge to mandible plane.

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 LPDH (lower posterior dental height): The perpendicular length from the
mesial cuspid of lower 6 to mandible plane.
 UAFH (Upper anterior facial height): The distance between N and ANS.
 LAFH (Lower anterior facial height): The distance between ANS and Me.
 UPFH (Upper posterior facial height): The distance between S and PNS.
 LPFH (Lower posterior facial height): The distance between PNS and Go.
 AFH (Anterior facial height): The distance between N and Me.
 PFH (Posterior facial height): The distance between S and Go.
2.1.2.3. Ratio measurements:
 LAFH/UAFH.
 PFH/AFH.
 UADH/AFH.
 LADH/AFH.
 UADH/UPDH.
 LADH/LPDH.
 UADH/LADH.
2.2.Folders used for each measurement:
It is important to mention from which file every variable was taken (see Tab I,
Tab II and Tab III).

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Tab I: Measurements that were digitally taken with Corel Draw x8.0
Variable’s name Picture’s it was taken from
Lower third height of the face Frontal at rest position
Two thirds’ height of the lower third of the
face
Frontal at rest position
Smile point Frontal at rest position
Nasolabial angle Side at rest position
Philtrum’s height Frontal at rest position
Commissural height Frontal at rest position
Intercommissural distance Frontal at rest position
Philtrum’s width Frontal at rest position
The distance between the ala of the nose Frontal at rest position
Upper lip height at rest Frontal at rest position
Upper lip height during smiling Frontal during spontaneous smile
Interlabial gap at rest Frontal at rest position
Upper lip to upper incisor edge during
smiling
Frontal during spontaneous smile
Gingival height during smiling Frontal during spontaneous smile
Upper teeth exposure at rest Frontal at rest position
Smile width Frontal during spontaneous smile
Buccal corridor space Frontal during spontaneous smile
Tab II: Measurements that were taken from pictures.
Variable’s name Picture it was taken from
Smile type Frontal during spontaneous smile
Facial type Frontal at rest position
Facial symmetry Frontal at rest position
Facial thirds equality Frontal at rest position
Upper lip line’s parallelism with pupillary
line
Upper lip line’s situation with labial
commissures
Incisal edge’s parallelism with pupillary line Frontal during spontaneous smile
Smile arch’s parallelism with lower lip line Frontal during spontaneous smile
Smile arch’s situation Frontal during spontaneous smile
Smile arch’s form Frontal during spontaneous smile

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Tab III: Variables that were taken from patient’s folders.
Variable’s name Document used
Gender Clinical examination’s sheet
Age Clinical examination’s sheet
Upper lip to upper incisal edge at rest position Lateralcephalogramradiographs
Upper lip’s thickness Lateralcephalogramradiographs
Lower lip’s thickness Lateralcephalogramradiographs
Chin’s thickness Lateralcephalogramradiographs
Cervical line Dental casts
Clinical length of upper incisors Dental casts
Clinical width of upper incisors Dental casts
Distance between upper central incisors Dental casts
Distance between upper lateral incisors Dental casts
Distance between upper canines Dental casts
Upper lip frenum’s situation Clinical examination’s sheet
Canine Angle’s class Clinical examination’s sheet
Molar Angle’s class Clinical examination’s sheet
Overjet Clinical examination’s sheet
Overbite Clinical examination’s sheet
Crossbite Clinical examination’s sheet
Incisal midlines’ coincidence Dental casts
Upper and lower incisal midlines’ coincidence with facial
midline
Dental casts
SNA Lateral cephalogram radiographs
SNB Latera lcephalogram radiographs
ANB Lateral cephalogram radiographs
IMPA Lateral cephalogram radiographs
I/NA Lateral cephalogram radiographs
i/NB Lateral cephalogram radiographs
I/F Lateral cephalogram radiographs
I/i Lateral cephalogram radiographs
SN/GoGn Latera lcephalogram radiographs
SN/Occ Lateral cephalogram radiographs
SN/PP Latera lcephalogram radiographs
AoBo Lateral cephalogram radiographs
I/NA Lateral cephalogram radiographs
i/NB Lateral cephalogram radiographs
UADH Lateral cephalogram radiographs
UPDH Lateral cephalogram radiographs
LADH Lateral cephalogram radiographs
LPDH Lateral cephalogram radiographs
UAFH Lateral cephalogram radiographs
LAFH Lateral cephalogram radiographs
UPFH Lateral cephalogram radiographs
LPFH Lateral cephalogram radiographs
AFH Lateral cephalogram radiographs
PFH Lateral cephalogram radiographs
LAFH/UAFH Lateral cephalogram radiographs
PFH/AFH Lateral cephalogram radiographs
UADH/AFH Lateral cephalogram radiographs
LADH/AFH Lateral cephalogram radiographs
UADH/UPDH Lateral cephalogram radiographs
LADH/LPDH Latera lcephalogram radiographs
UADH/LADH Lateral cephalogram radiographs

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3. Statistical analysis:
Statistical Package for the Social Sciences SPSS (IBM SPSS version 20, Chicago
III) was used to perform the statistical analysis and Microsoft Excel for graphic
descriptive representations. A Chi-square test was used for qualitative variables
and a t test for quantitative variables to determine a correlation between the
different parameters and smile type. Finally, a multiple linear regression was
calculated. Statistical significance was set at p<0.05.

Results
Page 25
We proceeded for a bivariate analysis to find a correlation between each variable
and gummy smile. Then a multivariate analysis allowed us to obtain a
relationship to be able to classify smiles as gummy or non-gummy.
1. Bivariate analysis interpretation:
1.1.Clinical and occlusal parameters:
1.1.1. Qualitative parameters:
A Chi-square test was used to find a correlation between the different qualitative
parameters and gummy smile.
1.1.1.1. Smile type:
70 subjects of our sample presenting 63.6% of the total percentage had a gummy
smile whereas 40 presenting 37.4% had a non-gummy smile. Smile type
distribution is summarized in the graph below.
Fig 20: Smile type distribution in the sample.
1.1.1.2. Gender:
Our sample included 30% males (33 subjects out of 110) and 70% females (77
subjects out of 110) with a sex ratio 0.43. The cross table down below indicates
63.6%
37.4%
smile type
gummy smile
non gummy smile

Results
Page 26
that there’s no significant difference between females and males’ proportions
depending on the smile type.
Fig 21: Gender distribution in the sample.
Tab IV: Crosstable between smile type and gender.
Gender
Total Sig (P)
Males Females
Smile type
Gummysmile 21 49 70
0.582Non-gummysmile 12 28 40
Total 33 77 110
1.1.1.3. Facial type :
The results of our study revealed neither clinical nor a statistical significant
difference of the distribution of the sample between the gummy smile group and
the non-gummy smile group (p=0.442>0.05). Results are shown in this table.
males
30%
females
70%
Gender

Results
Page 27
Tab V: Crosstable between facial type and smile type.
Facial type
Total
Sig
(P)Brachycephalic Dolichocephalic Mesocephalic
Smile
type
Gummy smile 28 32 10 70
0.442
Non-gummy
smile
20 17 3 40
Total 48 49 13 110
1.1.1.4. Facial symmetry :
Sixty-six subjects with a gummy smile had a symmetrical face whilst only 4 of
them had an asymmetrical face. For the non-gummy smile group those proportion
were 36 for symmetrical and 4 for asymmetrical. No significant difference was
noted (p=0.405>0.05).
Tab VI: Crosstable between facial symmetry and smile type.
Facial symmetry
Total Sig (P)
Symmetrical face Asymmetrical face
Smile
type
Gummysmile 66 4 70
Total 102 8 110
1.1.1.5. Facial thirds :
Our study revealed that the facial thirds equality did not have a significant effect
on the smile type. Results are shown in the crosstable down below.

Results
Page 28
Tab VII: Crosstable between facial thirds and the smile line.
Facial thirds
Total Sig (P)
Equal Not equal
Smile type
Gummy smile 39 31 70
0.140Non-gummy smile 28 12 40
Total 67 43 110
Tab VIII: Crosstable between prominent third and the smile type.
Prominent thirds
Total
Sig
(P)
Upper
third
Middle
third
Lower
third
Medium
and lower
thirds
Upper
and
middle
thirds
Upper and
lowerthirds
Smile
type
Gummy
smile
1 3 21 1 4 1 31
0,601
Non-gummy
smile
0 1 6 1 4 0 12
Total
1 4 27 2 8 1 43
1.1.1.6. Smile point:
In our study, we found that 23 out of the 70 subjects who had a gummy smile and
9 out of 40 subjects with a non-gummy smile had a centered smile point. On the
other hand, 47 gummy smile patients and 31 non-gummy smile patients had a
decentered smile point. Statistically speaking, this difference was not significant
(p=0.250>0.05).
Tab IX: Crosstable between the smile point and the smile type.
The smile point
Total Sig (P)
Centered Decentered
Smile type
Gummysmile 23 47 70
0.250
Non-gummysmile 9 31 40

Results
Page 29
1.1.1.7. Profile :
Out of 70 patients with a gummy smile, 35 had a convex profile, 7 concave and
28 straight. On the other hand, among 40 non-gummy smile patients, 16 had a
convex profile, 6 concave and 18 straight. Correlation between this variable and
gummy smile was non-significant.
Tab X: Crosstable between profiles’s form and smile type.
Profile
Total Sig (P)
Convex Concave Straight
Smile type
0.538Non-gummy smile 16 6 18 40
Total 51 13 46 110
1.1.1.8. Relationship between upper lip’s thickness, lower lip’s
thickness and chin’s thicknesses:
According to our study, the relationship between upper and lower lip and chin’s
thicknesses was statistically non-significant (p=0.799>0.05).
The cross table obtained showing this result is shown down below.
Tab XI: Crosstable between the relationship between upper lip’s thickness, lower lip’s
thickness and chin’s thicknesses and the smile type.
Relationship between the 3
thicknesses Total Sig (P)
Equal Unequal
Smile type
Gummysmile 16 54 70
Total 26 84 110

Results
Page 30
1.1.1.9. The cervical line:
The correlation between the cervical line’s form and the smile type was poor
according to the results of our study (p=0.362>0.05).
Tab XII: Crosstable between cervical line and smile type.
Cervical line
Total Sig (P)
Convex Concave Asymmetrical
Smile type
0,362
Non-gummy smile 10 11 19 40
Total 22 39 49 110
1.1.1.10. Upper lip frenum’s situation:
Among 70 patients with a gummy smile, the upper lip frenum’s situation was low
in 29 patients, high in 20 and medium in 21. For the non-gummy smile category,
17 had a low frenum, 10 high and 13 medium. This difference was not
statistically significant (p=0.915>0.05).
Tab XIII: Crosstable between upper lip frenum’s situation and smile type.
Upper lip frenum situation
Total Sig (P)
Low High Medium
Smile type
0,915Non-gummy smile 17 10 13 40
Total 46 30 34 110

Results
Page 31
1.1.1.11. Upper lip line:
The difference between upper lip line’s parallelism with papillary line in both
gummy and non-gummy smile groups was not statistically significant. However,
upper lip line’s situation with labial commissures’ correlation with the smile type
was found highly significant with a p<0.001.
Tab XIV: Crosstable between upper lip line's parallelism with pupillary line and smile
type.
Upper lip line's parallelism with
pupillary line Total Sig (P)
Found Not found
Smile type
Gummy smile 61 9 70
Total 94 16 110
Tab XV: Crosstable between upper lip line's situation with the labial commissures and
smile type.
Upper lip line's situation with the labial
commissures
Total
Sig (P)Above the
commissures
Same level as
the
commissures
Below the
commissures
Smile type
<0.001
Non-gummy
smile
4 15 21 40
Total 34 39 37 110

Results
Page 32
1.1.1.12. Incisal edge's parallelism with pupillary line:
Incisal edge’s parallelism with papillary line was found in 38 gummy smile
patients against 24 in non-gummy-smile patients. This parallelism was not found
in 32 gummy smile patients versus 16 in non-gummy smile ones.
Tab XVI: Crosstable between incisal edge's parallelism with pupillary line and Smile
type.
Incisal edge's parallelism with
pupillary line Total
Sig
(P)
Found Not found
Smile type
Gummy smile 38 32 70
Total 62 48 110
1.1.1.13. Angle’s canine class:
According to the table below, Angle’s canine class did not present a significant
difference between gummy smile and non-gummy smile patients despite its
clinical significance (p=0.174>0.05).
Tab XVII: Crosstable between Angle’s canine class and smile type.
Smile type
Total
Sig
(P)Gummy smile Non-gummy smile
Angle canine class
Cl I 31 9 40
0,174
Cl II 19 11 30
Cl III 11 9 20
Total 61 29 90
1.1.1.14. Angle’s molar class:
Angle’s molar class’ influence on the smile type was not statistically significant
(p=0.092>0.05).

Results
Page 33
Tab XVIII: Crosstable between angle’s molar class and smile type.
Smile type
Total
Sig
(P)Gummysmile Non-gummysmile
Angle molar class
Cl I 44 18 62
0,092
Cl II 15 8 23
Cl III 11 13 24
Total 70 39 109
1.1.1.15. Cross bite:
Crossbite and smile type did not present according to the table below a significant
correlation with the gummy smile (p=0.478>0.05).
Tab XIX: Crosstable between crossbite and smile type.
Smile type
Total
Sig
Crossbite
Non-existent 48 25 73
0,478
Anterior 18 14 32
Posterior 4 1 5
Total 70 40 110
1.1.1.16. Smile arch:
To find the relationship between the smile arch and the two types of the smile, we
studied the smile arch’s parallelism with the lower lip line, its situation and form.
All 3 variables showed no significant influence on the smile type according to our
study. Chi-square test’s results are shown in the 3 tables below.
Tab XX: Crosstable between smile arch’s parallelism with lower lip line and smile type.
Smile type
Total
Sig
(p)Gummy smile Non-gummy smile
Smile arch's
parallelism with
lower lip line
Consonant 29 14 43
0,634Non consonant 41 26 67
Total 70 40 110

Results
Page 34
Tab XXI: Crosstable between smile arch’s situation and smile type.
Tab XXII: Crosstable between smile arch’s form and smile type.
Smile type
Total
Sig
Smile arch's form
Convex 31 16 47
0,319
Concave 8 1 9
Plain 10 7 17
Irregular 21 16 37
Total 70 40 110
1.1.1.17. Incisal midline:
The two incisal midlines’ coincidence (upper and lower) as well as the
coincidence of each midline with the facial midline’s significance values were all
three superior to 0.05 meaning that correlation between the incisal midline and
the smile type was found poor.
Tab XXIII: Crosstable between the coincidence of upper and lower incisal midlines and
the smile type.
Smile type
Total
Sig
Coincidence of
upper and lower
midline
Found 30 15 45
0,583Not found 40 25 65
Total 70 40 110
Smile type
Total
Sig
Smile arch's
situation
Low 40 30 70
0,095
High 2 2 4
Medium 28 8 36
Total 70 40 110

Results
Page 35
Tab XXIV: Crosstable between the coincidence of upper incisal midline with facial
midline and the Smile type.
Smile type
Total
Sig
Coincidence of upper
incisal midline with
facial midline
Found 54 25 79
0,101Not found 16 15 31
Total 70 40 110
Tab XXV: Cross table between the coincidence of lower incisal midline with facial
midline and the smile type.
Smile type
Total
Sig
Coincidence of lower
incisal midline with
facial midline
Found 31 17 48
0,856Not found 39 23 62
Total 70 40 110
1.1.2. Quantitative parameters:
Means, standard deviations and p values for all the quantitative variables
measured are reported in the table down below. A t test was executed for all the
clinical and occlusal quantitative parameters. The results are shown in the table
down below.
Among the 39 quantitative variables that we studied, only 6 were significant. The
most significant variables were:
 Upper lip to upper incisal edge during smiling: p<0.001 and mean value
12.12 for gummy smile patients and 7.93 for non-gummy smile patients.
 Exposed gingival height during smiling: p<0.001 with a mean value in
gummy smile patients 3.86 versus -0.80 for non-gummy smile patients.
 Overjet: p=0.003<0.05 and mean value varies from 3.23 for gummy smile
to 2.39 in non-gummy smile.

Results
Page 36
Interlabial gap at rest had the value p=0.034<0.05 which indicates a significant
difference between gummy smile and non-gummy smile. Width/length ration of
maxillary left lateral incisors was significant as well with p=0.031<0.05. Upper
teeth exposure at rest also was found significantly related to smile type
(p=0.041<0.05).
On the other hand, many variables were not found statistically significant despite
their clinical importance such as lower third height of the face, upper lip height
during smiling, and upper lip thickness.
Tab XXVI: Comparison of clinical and occlusal parameters per smile group.
Variable
Gummy smile Non-gummy smile
PM SD N M SD N
Age 17.81 5.176 70 17.38 7.594 40 0.720
Lower third
height of the face
70.12 11.175 70 66.73 9.838 40 0.113
The two lower
thirds height of
the lower third of
the face
46.30 6.645 70 44.73 7.029 40 0.246
Nasolabial angle 97.14 12.184 70 100.72 12.604 40 0.146
Philtrum height 16.16 4.172 70 15.78 3.191 40 0.617
Commissural
height
24.04 5.589 70 22.74 3.411 40 0.183
Intercommissural
distance at rest
47.60 8.736 70 46.68 7.967 40 0.587
philtrum’s width 12.65 3.595 70 12.58 2.860 40 0.923
The distance
between the ala of
the nose
36.52 5.776 70 34.90 6.380 40 0.177
Upper lip height 23.37 4.469 70 22.07 3.483 40 0.118

Results
Page 37
at rest
Upper lip height
during smiling
15.83 3.616 70 16.04 4.515 40 0.785
Interlabial gap at
rest
1.15 2.062 70 0.395 1.190 40 0.034
Upper lip to
upper Incisor
edge at rest
position
4.43 2.468 70 4.16 2.486 40 0.579
Upper lip to
upper incisor edge
during smiling
12.12 4.760 70 7.93 1.716 40 <0.001
Upper lip
thickness
11.27 1.92.5 70 11.40 1.836 40 0.733
Lower
Lip thickness
10.20 1.938 70 10.67 1.366 40 0.174
Chin thickness
11.23 2.783 70 11.85 2.057 40 0.227
Exposed gingival
height during
smile
3.86 1.924 70 -0.80 2.743 40 <0.001
11 clinical length 9.83 1.051 70 9.87 0.965 40 0.847
21 clinical length 9.87 0.991 70 9.82 0.957 40 0.811
12 clinical length 7.58 0.955 70 7.63 1.097 37 0.810
22 clinical length 7.55 0.926 70 7.70 1.102 37 0.471
11 clinical width 8.96 0.633 70 8.90 0.871 40 0.657
12 clinical width 6.92 0.597 70 6.85 0.771 37 0.568
21 clinical width 8.95 0.626 70 8.90 0.841 40 0.724
22 clinical width 6.90 0.562 70 6.95 0,819 37 0.659
Width/length
ratio of maxillary
right central
incisors
0.91 0.092 70 0.90 0.109 40 0.471

Results
Page 38
Width/length
ratio of maxillary
left central
incisors
0.91 0.093 70 0.90 0.097 40 0.885
Width/length
ratio of maxillary
right lateral
incisors
0.92 0.154 70 2.74 12.044 37 0.207
Width/length
ratio of maxillary
left lateral incisors
0.92 0.135
70
0.83 0.270 37 0.031
Upper teeth
exposure at rest
1.01 1.844 70 0.35 1.082 40 0.041
Distance between
upper central
incisors
19.48 1.775 70 19.51 1.715 40 0.939
Distance between
upper lateral
incisors
34.54 5.491 70 33.63 4.814 40
0.388
Distance between
upper canines
51.76 4.342 69 50.53 5.571 39 0.206
Smile width
62.82 8.941 70 59.60 12.276 40 0.117
Right buccal
corridor space
1.21 1.582 70 1.65 1.931 40 0.202
Left buccal
corridor space
1.52 1.786 70 1.77 1.737 40 0.477
Overjet 3.46 3.006 70 1.73 2.727 40 0.003
Overbite 3.23 2.328 70 2.39 2.685 40 0.088

Results
Page 39
1.2.Cephalometric parameters:
Statistical t test allowed us to compare the mean value and the standard
deviations of the cephalometric variables. Four variables were found significant:
 The most significant variable was UPDH with p=0.001<0.05.
 The three other significant variables that were found were: IMPA
(p=0.016<0.05), UADH (p=0.025<0.05) and LAFH/UAFH
(p=0.029<0.05).
The rest of the parameters studied were not found statistically significant in
accordance with smile type (results are shown in tab26).
Tab XXVII: Comparison of cephalometric parameters per smile group.
Variables
P
M SD N M SD N
SNA 79.81 4.28 70 79.65 3.78 40 0.841
SNB 75.97 3.99 70 77.25 3.22 40 0.087
ANB 5.29 8.40 70 3.08 3.19 40 0.113
IMPA 96.66 7.07 70 92.08 12.62 40 0.016
I/NA angle 26.64 8.60 70 25.30 7.82 40 0.418
i/NB angle 29.34 6.40 70 27.40 7.67 40 0.158
I/F 115.54 15.75 70 114.13 12.21 40 0.625
I/i 120.37 16.07 70 123.45 14.63 40 0.321
SN/GoGn 37.32 13.92 70 34.15 6.02 40 0.174
SN/Occ 18.03 5.27 70 17.90 4.67 40 0.898
SN/PP 9.86 3.89 70 10.28 3.58 40 0.579
AoBo 1.80 5.32 70 0.1 4.65 40 0.113
I/NA linear 6.70 3.19 70 5.85 2.37 40 0.145
i/NB linear 6.70 2.97 70 5.68 2.44 40 0.067
UADH 31.56 5.24 70 29.30 4.53 40 0.025
UPDH 25.07 3.60 70 22.58 3.70 40 0.001
LADH 44.27 5.45 70 42.48 4.47 40 0.080
LPDH 33.70 4.09 70 32.15 3.72 40 0.051

Results
Page 40
UAFH 55.29 5.65 70 55.43 5.36 40 0.899
LAFH 71.74 9.10 70 68.68 6.98 40 0.068
UPFH 48.84 6.83 70 47.60 4.57 40 0.307
LPFH 45.79 6.24 70 43.35 6.35 40 0.053
AFH 125.06 12.19 70 122.15 10.45 40 0.209
PFH 77.46 8.87 70 75.45 8.05 40 0.241
LAFH/UAFH 1.299 0.147 70 1.240 0.109 40 0.029
PFH/AFH 0.615 0.054 70 0.614 0.048 40 0.901
UADH/AFH 0.248 0.031 70 0.236 0.039 40 0.088
LADH/AFH 0.873 4.261 70 0.340 0.034 40 0.431
UADH/UPDH 1.261 0.158 70 1.277 0.276 40 0.713
UADH/LADH 1.2873 0.192 70 1.273 0.241 40 0.743
LADH/LPDH 0.721 0.132 70 0.689 0.120 40 0.201
2. Multivariate analysis:
A multivariate approach to all the parameters that were studied (clinical, occlusal
and cephalometric parameters) was elaborated. Only variables that had values of
p<0.25 in the bivariate analysis were included in the multivariate model of
regression. Due to the important number of the variables, the logistic model was
constructed step by step backward. We finally obtained a multivariate model of 6
variables that are respectively:
 Smile arch’s situation (with 0 for low, 1 for high and 2 for medium).
 Exposed gingival height during smile.
 UPDH (upper posterior dental height).
 LADH (lower anterior dental height).
 Overjet.
 ANB.

Results
Page 41
Tab XXVIII: Multivariate analysis for the logistic regression model.
B E.S Wald ddl Sig. Exp(B)
CI 95% for
EXP(B)
Inferior Superior
Smile arch’s
situation
-1.677 0.614 7.448 1 0.006 0.187 0.056 0.623
Exposed gingival
height during smile -1.355 0.371 13.341 1 <0.001 0.258 0.125 0.534
UPDH -0.557 0.205 7.411 1 0.006 0.573 0.384 0.856
LADH 0.244 0.130 3.537 1 0.060 1.276 0.990 1.645
Overjet -0.630 0.229 7.571 1 0.006 0.532 0.340 0.834
ANB -0.181 0.159 1.296 1 0.255 0.834 0.610 1.140
Constant 7.975 4.205 3.597 1 0.058 2908.811
The model of logistic regression correctly classified 91.8% of the subjects as
gummy smile patients or non-gummy smile patients, but the specificity to
diagnose gummy smile patients was lower (85%) than the sensibility (95.7%).
This means that the model is better to classify the presence of gummy smile than
to detect its absence (Tab XXVIII). The goodness of fit of the model, according to
Hosmer and Lemeshow test [7] indicates that the difference between observed
and estimated by the model values is p=0.048< 0.05 which is close to the limit of
significance but is still acceptable.
Tab XXIX: observed and predicted percentages in the regression model.
Observed
Prediction
Correct prediction
%
Smile
type
Gummy smile 67 3 95.7
Non-gummy smile 6 34 85.0
Overall percentage 91.8

Results
Page 42
The six variables included in the model explained 80% of the variability in the
frequency of GS (Coefficient of Regression R2 of Nagelkerke).
The logistic model of regression obtained in the present study provides the
following equation to estimate the probability to have a non-gummy smile as
p<0.25:
Logit(p)=7.975-1.677*SAS-1.355*GE-0.557*UPDH+0.244*LADH-
0.63*overjet-0.181*ANB
In this equation, SAS stands for smile arc’s situation and GE stands for gingival
exposure.
This equation is resumed by the ROC curve down below:
Fig 22: The ROC curve resuming our equation.

Results
Page 43
The critical score is equal to 0.38 for which the smile is considered non-gummy
with 77.5% sensibility and 85% specificity. The area under the ROC curve is
0.966 >0.9 which indicates that the sensitivity and specificity that we get from
our equation are favorable.

Discussion
Page 44
In the present study, the bivariate analysis showed the following results:
 Clinical and occlusal parameters:
A significant difference in the upper lip’s situation with the labial commissures
(above, same level as or below the commissures) was found between gummy
smile patients and non-gummy smile patients.
Among the quantitative variables, upper lip to upper incisor’s edge during smile,
exposed gingival height during smile and overjet were the most significant.
Interlabial gap at rest showed a significant difference between the two smile
types as well as width/length ratio of maxillary left lateral incisors and upper
teeth exposure at rest.
 Cephalometric parameters:
The most significant parameter above the thirty-one cephalometric ones was
UPDH (upper posterior dental height). Three other variables showed a
statistically significant difference between the two smile type patients which
are IMPA (the angle between the lower incisor’s big axis and the mandibular
plane), UADH (upper anterior dental height) and LAFH (lower anterior facial
height).
1. Autocriticism :
1.1.Choice of posed smile for our study: [6,8,9]
To begin with, it is primordial to distinguish between the posed smile and the
spontaneous smile.
The posed smile is a voluntary expression and is not elicited or accompanied by
emotions. It is static in the sense that it can be sustained.
The spontaneous smile on the other hand or forced smile is involuntary and
driven by emotions. It is not simply repeatable over time.

Discussion
Page 45
Most studies in orthodontics refer to the posed smile since it is repeatable over
time and reproducible unlike the spontaneous smile.
Furthermore, with the traditional photographic techniques that we disposed, only
a posed smile was considered adequate to obtain a reproducible diagnostic
record. A spontaneous smile is better captured with a digital videographic
technology rather than static photography.
1.2.Positive points:
 The use of photography for the study:
The use of this method in the gathering of the sample allowed us to include an
important number of variables without taking a lot of the patients’ time which
could have made them uncomfortable and the study more difficult.
 The number of variables:
In this study, we have analyzed an important number of variables which allowed
us to determine the maximum of factors that influence the gummy smile in our
orthodontic population. This helped us at the end to find an equation that helps us
in the diagnosis of a gummy smile.
1.3.Limits of the study:
 The size of the sample:
Taking in the consideration the great number of the variables that we’ve studied,
our sample’s size is considered reduced. in fact, while collecting the sample,
many patients refused to be photographed. We ended up photographing 132
patients. However, amongst those 132, we only had 110 complete orthodontic
records due to the lack of cooperation of some of them, the bad quality of lateral
cephalographs and the bad quality of some of the pictures that we took.
 Cultural and communication issues:

Discussion
Page 46
Most of our subjects were too shy to smile. This is related to the social
conservatism of some Tunisian families. There were also some communication
issues related to explaining the posed smile which made photographing time
longer for some patients.
 Monocentrism:
Our study was monocentric. It was led in the orthodontic department in
Monastir’s dental clinic. This means that the majority of our sample was from the
Sahel considering the proximity of the clinic. Our results could’ve reflected more
the Tunisian population if our study have been multicentric.
2. Discussion of the results:
2.1.Clinical and occlusal parameters:
2.1.1. Qualitative parameters:
 To judge the smile, there are many classifications the most known is Tjan et
al’s [10] dividing the smiles into three categories: a “low smile” when less
than 75% of the clinical crown height of the maxillary anterior teeth are
displayed, an “average smile” revealing 75% to 100% of the maxillary
anterior crown height, and a “high smile” when a band of contiguous
maxillary gingiva is exposed. However, a 2mm limit should be established
above and below the gingival edge to differentiate the smile types that lead
patients to seek treatment [11]. Therefore, we chose to describe a smile type
as “gummy smile” if the lip line is 2mm or more above the gingival margin
and “non-gummy smile” if less than 2mm of gingiva is exposed which helped
us to simplify the filling of our study sheets as well as the statistical analysis
and interpretation. In our sample, the prevalence of gummy smile was 63.6%.
This number is considered very high in comparison with a study led by Rais
M [12] who found the prevalence of gummy smile 21% in a Moroccan
population and the study led by Faye MA [13] with a percentage of 28.5% in

Discussion
Page 47
favor of gummy smile in a Senegalese population. This notable difference
between the numbers may be explained by the fact that unlike those two
studies, all of the subjects of our sample consulted to improve their smile.
Moreover, our study was monocentric.
 The sample of this study was composed of 30% males (33) and 70% females
(77) which means that the number of females is more than twice the males.
This can be attributed to the fact that women are more likely to consult in
orthodontic department than men since aesthetics present a greater importance
to them. This study showed no statistically significant correlation between
gender and smile type. Forty-nine females had gummy smile against 21males
which presents the same percentage of each gender (63.63%). Barbosa et al
[14] also found this sexual difference insignificant. On the other hand, clinical
observations found that smile height is influenced by age [11]. Al-Habahbeh
R et al [15] found the gender effect significant on the gingival exposure.
Sepolia S et al [16] found that women revealed more gingiva than men during
smile. Miron, Calderon et Allon found a significant sexual dimorphism related
to sex [17]. Jensen et al [18] reported that women had higher smile lines in
comparison to males. Tjan et al [10] who did a study on 20 to 30-year-old
students also found that high and very high smile lines were found more in
women (14% and 75%) than in men (7% and 63%).
 According to our study, facial type (brachycephalic, dolichocephalic and
mesocephalic) had no significant effect on the smile type. It was found in
other studies [2] that smile arc’s form changes depending on the facial type
which is related to the fact that facial type has an influence on teeth’s form
and size.
 Facial symmetry also had no statistical difference between gummy smile
group and non-gummy smile groups. This may be explained by the rarity of
transverse anomalies in our sample. No studies related to the relationship
between facial symmetry and gummy smile prevalence have been found.

Discussion
Page 48
 To objectively evaluate its appearance, the face was divided into vertical
thirds. These thirds are based on horizontal lines drawn at the hairline, the
brow line, the nasal base, and chin. The thirds should be equal in length
according to Panossian AJ et al [19]. Otherwise, a skeletal or soft tissue
deformity exists. In our study, this proportionality did not have a significant
difference depending on the smile type (p=0.140> 0.05). The prominent third
in case of inequality also had a very low significance (p=0,601>0.05). These
results can be due to our sample’s reduced size.
 The smile point is the middle of the vertical line joining the bipupillary line
and the chin line. Its position should coincide with the upper lip point
according to Aboucaya [20] (central). In our study, 60.9% of the 110 subjects
had central smile point. ABOUCAYA studied smile point on a sample of 30
Merina ethnic persons. He found the smile point central in 60% of the
population which is almost the same percentage that we found in a larger
sample. However, this variable showed no influence on the smile type in our
study with the value of p=0.25>0.05.
 Profile did not have an influence according to this study (p=0.538>0.05).
 A 1:1:1 relationship exists among soft tissue anterior-posterior thickness in
particular the upper lip, lower lip and chin [19]. If there is a difference in the
thickness of these areas, the general balance of the lower third will appear less
esthetic. In our study, this relationship did not present a significant difference
between gummy smile subjects and non-gummy smile subject
(p=0.799>0.05). A percentage of 76.36% of our sample had unfavorable
relationship between those three thicknesses. This may be due to the fact that
our sample is composed of patients with orthodontic problems.
 Cervical line is ideally convex while concave form (when the gingival contour
of the canines is below the lateral incisors) is less pleasing [11]. The last form
that we found was asymmetrical cervical line when the heights of the anterior
teeth were asymmetrical. The study led to no significant correlation between

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smile type and cervical line’s form (p=0,362>0.05) despite its clinical
contribution in the smile.
 Upper lip’s frenum also showed no statistical significance in our study
(p=0,915>>0.05) although we’ve expected a certain relationship between a
high frenum and a high smile line.
 Upper lip line is the lower edge of the lip. It dictates the exposure of upper
teeth [11]. Based on the lip line’s situation with the labial commissures, a
smile can be classified into 3 types: one above the commissures or gummy
smile, one commissural or cuspid smile and one below the commissures or
commissure smile [20,21]. The parallelism of this variable with pupillary line
did not have a statistical significance according to our study. However, smile
line’s situation with the labial commissures had a very high correlation with
smile type with a value of p=0<0.05. In our sample, 34 patients (30.9%) had a
gummy smile, 39 (35.45%) had a cuspid smile and 37 (33.63) had a
commissure smile. Our findings do not coincide with Liang L Z et al’s study
on a young Chinese population [21] who found 60.6% commissural smile and
only 5.9% gummy smile. Aboucaya [20] found similar results on Merina
ethnic people with 53.4% commissural smile. This difference might be the
result of the ethnic difference between Chinese and Merina people and
Tunisians whom are, according to a genetic study led in 2010 by El Moncer
W et al [22], are mostly composed of North African Berbers.
 Upper incisors’ edge’s parallelism with papillary line did not have a
significant correlation with smile type despite its influence on smile’s
harmony and appearance.
 Angle’s dental class (canine and molar) did not present a significant effect on
the smile in this study. Other studies found a significant correlation between
angle’s class and smile. Alkhlaf M and Al sabbagh R [23] who studied the
effect of clI, clII div1 and 2 on the upper lip’s height and thickness at smile
position, have found that the upper lip length at smile position in class II div1

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was higher compared with class I, II div2. Harati M and co [24] confirmed the
concept that the beauty of smile is independent of the intermaxillary relation
by studying angle’s molar’s class’s effect on the smile.
 Crossbite did not have a statistically notable effect on the smile line’s situation
according to our findings (p=0,478>0.05). The only study found including this
parameter was an Iranian study conducted by Harati M et al [24]. They have
studied the effect of posterior crossbite on the smile line’s form and have
found that it was mostly associated with reversed smile lines and least
associated with parallel ones. Unfortunately, no previous research about the
relationship between smile type and cross bite was found to compare our
results with.
 The smile arch is a hypothetical line following the edges of anterior maxillary
teeth. To be considered an esthetic and youthful smile, this curvature must be
parallel to the superior margin of the lower lip giving it a convex form also
called a “deep plate”. It’s also preferable for the lower lip to barely touch or
not touch the smile arch to be considered more aesthetic [2,11, 25, 8]. In our
study, the smile arch’s parallelism with lower lip line, situation and form did
not turn out having a significant influence on the smile type. P values were
respectively 0,634, 0,095 and 0,319 (all > 0.05). Our results support Parekh H
et al’s [9] who studied the consonance and non-consonance of the smile arch
and found no correlation between the smile arch and the smile height. Harati
M et al [24] assumed on the other hand that the smile arch’s form might affect
the smile. On the other hand, Kaya and Uyar [26] studied the influence of both
smile arch and gingival display on smile’s perception using a series of photos
digitally modified. They found a significant correlation between these two
parameters combined and the way that people judged the smile.
 Upper and lower incisal midlines’ coincidence is an important criterion for a
beautiful smile [27]. The deviation between those two is not noticed under
4mm according to a study by Kokich, Kiyaket Shapiro in 1999 [28]. Upper

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and lower incisal midlines’ coincidence as well as their coincidence with the
facial midline were not significant factors influencing the gummy smile
according to our study (values of significance respectively: p=0,583>0.05,
p=0,101>0.05 and p=0.856>0.05). We have found no studies that were
interested in the correlation between incisal midline and the gummy smile.
2.1.2. Quantitative variables:
 Age is considered an important factor contributing in the smile. Children are
more likely to have more gingival display than adults [29] since the aging
process affects the skin, soft tissues and structural support tissues [30]. In our
study, no significant difference in the mean ages of the subjects of the two
smile type groups was found (17.81 for gummy smile group versus 17.38 for
non-gummy smile group with p=0.72>0.05). This can be due to the fact that
our sample is relatively young and mostly composed of teenagers. Sepolia S
and co [16] found the relationship between age and the smile line situation not
significant. However, Van der Geld [31] had other findings then ours. He
confirmed the lowering of the smile line by aging as well as Padmasree. S
[32] who found that age and maxillary incisor’s visibility had a significant
relationship.
 The lower third of the face is the distance between the subnasale (the base of
the nose) to the chin (the most inferior point on the mandibular symphysis)
[19]. Our study did not reveal a significant correlation between the lower third
of the face and gummy smile (p=0.113>0.05). Our findings support the
findings of Barbosa D et al [14] who had a non-significant difference in the
low facial height between gummy smile and non-gummy smile group.
 The lower two thirds of the lower third are measured from the lower lip
stomion (top surface of the lower lip) to the chin. Normal values are 51± 3
mm for males and 48 ± 3mm for females [19]. In our study, we found that the
mean value of the lower 2/3 of the lower 1/3 in the gummy smile group was

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46,30 versus 44,73 in non-gummy smile group which can be considered
normal and the difference also was non-significant (p=0.246>0.05).
 This study did not lead to a significant correlation between nasolabial angle
and the smile type. No study has been found that studied this parameter before
ours.
 The philtrum height is measured from subspinale (the base of the nose at the
midline) to the most inferior portion of the upper lip on the vermilion tip
beneath the philtral columns [33]. According to our findings, patients with a
gummy smile had a mean value of the philtrum’s height 16.16 while non-
gummy smile’s philtrum’s height’s mean value was 15.78. This difference
was not found statistically significant in this study. No previous study has
been found that studied the relationship between philtrum’s height and
gummy smile.
 Commissural height is obtained by measuring perpendicularly the distance
between labial commissures and their projections in a horizontal line that joins
the two wing bases [2]. Lip length should be roughly equal to the commissure
height [8] which was almost found by comparing the mean values that we
found. In our study, we measured the vertical distance between the
commissural line (the line that joins the two commissures) and the base of the
nose. Its mean value in gummy smile patients was 24.04 and 22.74 for non-
gummy smile ones. This difference was not considered statistically significant
(p=0. 183>0.05). There’s no previous study that we could find that could have
supported our study. Another study was conducted by Drummond and Capelli
[30] looking for a correlation of commissure height with age and gender and
they found that commissure height increases significantly with age and that it
was higher amongst men.
 Inter-commissural distance at rest (or mouth width) is the distance between
the two corners of the mouth at rest position. This study led to no significant
difference between this measurement in gummy smile group and non-gummy

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smile group. This may be explained by fact that gummy smile is more related
to vertical dimension.
 Philtrum’s width as well as the distance between the ala of the nose did not
have a significant influence on the smile type (respectively p=0.923 and
p=0.177 both >0.05). We are the first to take the initiative and include these
parameters in a study about gummy smile.
 Upper lip height at rest is the vertical distance between the subnasale and the
stomion [19, 8]. The mean value of upper lip’s height at rest in our sample
was 23.37 in the case of gummy smile and 22.07 in the case of non-gummy
smile. This difference was statistically non-significant contrarily to our
predictions. Peck and Peck [34] found that the mean value for gingival smile
line group was 22.3 against 22.3 in the reference group so no significant
correlation was found between this variable and gummy smile. Barbosa D et
al [14] as well support our findings. They found no significant difference
between upper lip’s height in gummy smile group and non-gummy smile
group (p=0.154>0.05). Miron, Calderon and Allon [17] contrary to these
observations, found that the higher the smile pattern, the shorter the upper lip
length same as Alkhalaf and al sabbagh [23].
 Upper lip height during smiling’s mean values did not have a significant
difference between the gummy smile group and the non-gummy smile group.
P value was 0.785 which is way higher than 0.05. However, Barbosa D et al
[14] found the difference between the gummy smile group and the non-
gummy smile group very high (p<0.001). Differences between the studies
might be explained by age differences since our sample is older than the one
in Barbosa’s study.
 Interlabial gap at rest is the distance between upper and lower lip’s borders at
rest position. There was a long-standing belief that patients with short upper
lip and increased interlabial space have an excessive gingival display [2]. Our
findings support this assumption since the relationship between intelabial gap

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and the presence of a gummy smile was found statistically significant
(p=0.034<0.05). However, Peck and Peck [34] supported our results and
found that interlabial gap at rest position had a very significant effect on
gummy smile.
 The distance between upper lip and upper incisor’s edge at rest position was
measured on the lateral cephalometric radiographs. The difference between
the mean values of the two smile groups was found in our study non-
significant (p=0.579>0.05). Peck and Peck [34] on their behalf found this
relationship between this measurement and the gummy smile highly
significant with a p value <0.001. This inconformity may be attributed to the
fact that in peck’s study they worked on patients undergoing an orthodontic
treatment unlike ours in which we only included patients before starting any
kind of orthodontic treatment.
 The mean distance between upper lip and upper incisor’s edge during smile in
our sample changed from 12.12 in the gummy smile group to 7.93 in the non-
gummy smile group. This difference was highly significant with p=0. Peck
and Peck [34] also found that this variable’s mean value varied from 7.1 in the
gummy smile group to 5 in the control group with p<0.001. The concordance
of our results can be due to the fact that this distance is directly related to the
upper lip position which is one of the main components of the gummy smile.
 Thin lips are known to be responsible of greater exposure of the dentoalveolar
structures [2]. McNamara L et al [35] found in their study a positive
correlation between upper vertical lip thickness and smile aesthetics. They
found that upper lip thickness is 1 of 2 variables that accounted mostly for
discrimination between pleasant and unpleasant smiles. Our study on the other
hand studied the correlation between upper lip thickness and the presence of a
gummy smile judged unaesthetic. However, this correlation was found non-
significant. The same study previously mentioned [35] found similar positive
correlation between the lower lip thickness and the smile aesthetics. Same as

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for the upper lip thickness’ influence on the gummy smile, lower lip
thickness’s correlation with the smile type was found also statistically non-
significant by our study. The chin also contributes in the harmony of the lower
third of the face by its thickness. In our study, we searched for a possible
correlation between the chin and the smile. However, statistical analysis
showed that this correlation was non-significant. The non-significant
influence of these three different variables on the smile can be attributed to the
narrowness of the simple’s size or also the facies of Tunisian population in
which the smile might not depend on these parameters.
 Exposed gingival height during smile is the first criteria used to clinically
diagnose a gummy smile. It directly influences the smile aesthetics and our
perception of it. Moreover, based on this parameter, Tjan and Miller (1984)
[10] gave a classification to the smile: low smile line (a part of the teeth is
covered), average smile line (all the teeth height is exposed) and high smile
line (a ban of gingival is exposed). This classification was updated Liébart
MFet al [35] who added a fourth category which is the gummy smile line
(more than 2mm of gingival is exposed). In our study, the gum exposure had
as expected a high significant influence on the smile type (p=0). Its mean
value was 3.86 in the gummy smile group against -0.8 in the non-gummy
smile group. Peck and Peck [34] had a significant difference (p<0.01) between
the gingival smile group (mean value= 6.2) and the reference group (mean=
5.2). Furthermore, Loi H et al [1] found that it was agreed by both
orthodontists and dental students that over 2mm of gingival display was
unattractive. Kaya and Uyar [26] also found that the gingival display amount
had a statistically significant influence on the perception of smile
attractiveness.
 In this study, we’ve measured the length and width of the four upper incisors
as well as the width/length ratio of all four. Results showed neither a
significant correlation of the length nor the width of each upper incisor with

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the gummy smile. However, among the four width/length ratios of the upper
incisors, only the width/length ratio of maxillary left lateral incisors was
significantly increased in the gummy smile group in comparison with the non-
gummy smile one. This ratio should be around 70% otherwise the tooth would
be square [2]. However, the mean value of 22’s width/length ratio found was
92% for gummy smile patients and 83% for non-gummy smile patients. This
suggests that our sample’s upper left laterals are more likely to look square.
Moreover, the significant relationship with the gummy smile of this
width/length ratio of the 22 can be due to the fact that laterals’ situation in the
mouth is lower than centrals which suggests a higher amount of gingival
exposure than the centrals. Indeed, Crispin and Watson [36] reported that
upper lateral incisor was the most common visible tooth during his evaluation
of 425 dental school students.
 The upper teeth exposure at rest position is the distance between the upper
lip’s lower border and the incisal edge. Upper incisor intrusion,
dolichocephalic facial pattern, vertical maxillary excess and short upper lip
might increase this dimension [2]. We found that upper teeth exposure at rest
significantly varied between gummy smile group and non-gummy smile group
(p=0.041<0.05) which was supported by other studies [17,32].
 Measuring the distances between upper central incisors, upper lateral incisors
and upper canines on dental casts and comparing them led us to no significant
variation in the measurements that we took between the two smile groups.
 Smile width is the distance between the outer commissures of the lips [37].
We found in our study that smile width’s mean value decreased from 62.82
for gummy smile group to 59.6. However, this difference was not statistically
significant (p=0.117>0.05). Van Der Geld et al [6] studied the difference of
smile width between posed and spontaneous smile (that was found higher than
the posed smile by the same author) and found a significant reduction in inter-
commissure distance between the two smile types. This means that smile

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width increases by the increased smile height yet this statistical non-
significance that we found can be related to the size of the sample or the
number of the variables that made some of them more significant than others.
 The buccal corridor space is the distance from the inner lip commissure to the
most posterior visible maxillary tooth on each side. This space is considered
negative by orthodontists and is targeted in the orthodontic treatment [8, 37].
In our study, we’ve measured both the right and the left corridor spaces for
each patient. Both showed no significant difference between gummy smile
patients and non-gummy smile patients. Other studies have disclosed the
correlation between buccal corridor space and smile attractiveness [38] as well
as gender [9] but no study studied the effect of this space on the gummy smile
like we did.
 Overjet’s correlation with the smile type was found very significant with
p=0.003. Its mean value for gummy smile patients was the double of the non-
gummy smile’s. Peck and Peck [34] also found that the overjet had a very
high influence on the smile height with p<0.001 when they compared this
measurement between two groups: one with a gingival smile and one
reference group. However, our findings diverge with Barbosa D et al’s [14] in
which this correlation between overjet and gummy smile was found non-
significant. This non-concordance might be due to the age difference between
their sample (nearly 9) and ours (in the range of 17) and the ethnical
backgrounds between Latinos (Brazilian) and Berbers (Tunisians) [22].
 In our study, overbite did not present a significant difference between the
gummy smile group and the non-gummy smile group (p=0.088>0.05). These
results differ from those found by Peck and Peck [34] who found that overbite
had a significant difference between gingival smile group and control group.
Barbosa D et al [14] found overbite’s correlation with the smile ty significant
(p<0.001). This divergence in the results between our study and the two other

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studies found might be due to the difference in the facies between their
population and ours.
2.2.Cephalometric parameters:
2.2.1. Angular measurements:
 SNA informs us about the antero-posterior position of the maxilla in the
cranial base. This study led to no significant difference between the mean
values of SNA in the two smile groups. This means that according to our
study, the gummy smile does not depend on the position of the upper incisor
in the maxillary. Hayani A et al [39] conducted a study on 40 Syrian females
and studied the correlation between 30 cephalometric parameters and the
gummy smile including SNA. They found that the difference between SNA in
the gummy smile group and the controle group was not statistically
significant.
 SNB informs us about the antero-posterior position of the mandibule in the
cranial base. We found that the correlation between SNB and the gummy
smile statistically non-significant. Hayani A et al [39] had similar results and
found the relationship between this measurement and gummy smile non-
significant. In other words, our study-supported by the Syrian study- found
that the lower incisor does not interfere with the smile type.
 ANB is used to determine the skeletal class of the patients. The mean value of
ANB in our sample decreased from 5.29 for gummy smile patients to 3.08 for
non-gummy smile patients. This means that the patients with gummy smile in
our sample mostly have a skeletal clII (ANB>4°) against a predominance of
skeletal clI for non-gummy smile patients (0<ANB<4). However, in contrary
to our predictions, this difference was not found statistically significant
(p=0.113>0.05). Hayani A et al [39] on the other hand found the relationship
between the gummy smile and ANB significant and they explained that by the
possibility of the retrusion of point B due to the increase of all the linear and

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angular measurements in the vertical direction. This difference between their
results and ours can be attributable to the fact that in the Syrian study, the
sample size was smaller and more fairly distributed than ours.
 IMPA is the angle between the lower incisor’s axis and the mandibular plane.
Its normal value is 90° [19]. In our study, this angle’s mean value decreased
from 96.66° in gummy smile group to 92.08° in non-gummy smile group
(both >90°). This difference was found statistically significant according to
the value of p=0.016<0.05. These measurements give us the impression that,
in this sample, the more the lower central incisor protrudes the higher the
smile line is.
 I/NA determines the position of the upper incisor inside its socket. Our study
as well as Hayani A et al [39] found the correlation between I/NA and gummy
smile non-significant.
 i/NB determines the position of the lower incisor inside its socket. Same as
I/NA, this parameter was not found significant towards the smile type by our
study. Hayani A et al [39] on the other hand, found that the lower incisor was
significantly protruded in the gummy smile group as a dental compensation
for the increased ANB angle they found.
 The angle between Frankfort plane and the axis of the upper central incisor
(I/F) had no significant influence on the gummy smile according to our study.
This angle gives the inclination of the upper central incisor in relation to the
Frankfort plane. This means that upper central incisor’s protrusion is not a
factor of gummy smile in our sample.
 The normal value of I/i or interincisal angle is 135± 5° [19]. In this study, this
variable did not show a significant difference between the two smile type
groups yet the mean values in the two groups were sharper than the normal
value (120.37 in gummy smile group and 123.45 in the non-gummy smile
group). This observation might lead us to think that this sample has a
protrusion of both upper and lower incisors.

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 SN/GoGn, unexpectedly had a non-significant difference between the two
smile groups (p=0.174) since we generally suspect an increase in the anterior
vertical dimension in case of a gummy smile. However, we notice that the
mean value of this angle in the gummy smile is superior to the non-gummy
smile’s which supports our suspicion. Hayani A et al [39] found this angle’s
difference between the two groups highly significant (p=0). Peck and peck
[34] who studied the angle between the mandibular plane and SN to evaluate
the anterior vertical dimension’s influence on the gingival smile line found no
statistical significance of this angle on the gummy smile.
 The normal value of the angle SN/Occ is 14°. In our sample, we noticed that
in both gummy and non-gummy smile groups, SN/Occ was > 14 which leads
us to conclude that the majority of this sample’s subjects have a low occlusal
plane. However, the difference between the two smile type patients was not
significant. Hayani A et al [39] confirmed those results since they also found
no significant influence of SN/Occ on the smile type.
 In our study, the angle between the palatal plane and SN (SN/PP) did not have
a significant influence on the smile type (p=0.579>0.05). This suggests that
the inclination of the maxilla was not a contributing factor in the occurrence
of a gummy smile. Hayani A et al [39], Peck and Peck [34] and Wu et al [40]
supported our findings through the non-significance of the difference in this
measure (all p values were superior to 0.05).
2.2.2. Linear measurements:
 AoBo was not found statistically significant in our study.
 I/NA and i/NB’s relationship with the smile were found non-significant.
However, Hayani A et al [39] found them both significant.
 The UADH’s mean value decreased from 31.56 in gummy smile group to
29.30 in the non-gummy smile group. This difference was statistically
significant. Hayani A et al [39], Peck et al [34] and Wu et al [40] also found

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the upper anterior dental height’s difference significant between gummy smile
group and the control group (of 2-3mm).
 The upper posterior dentoalveolar height also had a significant difference
between the two groups in our study. It was almost 2.5mm higher in the non-
gummy smile group. These results are similar to Hayani A et al’s [39]. They
have suggested that the increase of both upper anterior and posterior
dentoalveolar height might have contributed in the increase of posterior
rotation of the mandibule.
 Although LADH was increased in favor of the gummy smile, this was not
found statistically significant in this study. Hayani A et al [39] found that the
lower anterior dentoalveolar height was significantly larger in the gummy
smile group.
 The lower posterior dentoalveolar height’s mean value was higher in the
gummy smile group. This difference was found significant. Hayani A et al’s
[39] on confirmed our results and found it significant. This may lead us to
think that the height of lower first molar has an impact on the gummy smile
by causing an anterior rotation to the mandibule which makes the upper have
a higher position while smiling. However, a study by Wu et al [40] found that
the LPDH was significantly smaller in the G.S. group. This might be due to
the fact that they used a different mandibular plane reference to measure this
dimension (GoGn) than ours (Down’s mandibular plane).
 UAFH did not have a significant difference between the two smile groups in
this study (p=0.899>0.05). Hayani A et al [39] found that the influence of
UAFH on the gummy smile was significant.
 LAFH was 3mm more increased among gummy smile patients. This
difference was not significant in our study despite its clinical contribution in
the gummy smile. Hayani A et al [39] on their side found this difference
highly significant with p=0<0.05. This non-significance of this measure in our

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study can be due to the difference of the sample size and the high number of
variables of our study.
 UPFH was not significant in our study (p=0.307>0.05). Hayani A et al [39]
also found its influence non-significant on the gummy smile.
 LPFH was more than 2mm higher in our gummy smile group. This difference
was significant according to our study (p=0.05). Contrarily to what we found,
Hayani A et al [39] found this measurement insignificant (p=0.942>0.05). The
divergence found in the results can be explained by the differences of facies
between Tunisians (mostly composed of Berbers [22]) and Syrian population
(basically Arabs). Also, we must recall that the sample in Hayani A et al’s
study included only post pubertal females.
 Clinically speaking, the anterior height of the face is usually recalled when a
patient presents a gummy smile. In this study, AFH was 3mm higher in the
mean value of the gummy smile group than in the non-gummy smile group.
However, this difference was found statistically non-significant. Hayani A et
al [39] on the other hand found AFH highly significant. The reason of this
non-concordance of the results is that in our study, both UAFH and LAFH
were non-significant whereas in the Syrian study both measurements were
significant which led to the significant increase of AFH.
 PFH was found non-significant in both our study and Hayani A et al’s study
[39].
2.2.3. Ratio measurements:
 LAFH/UAFH was found significant in our study (p=0.029<0.05). This
suggests that in the anterior dimension, the lower anterior facial height is
prominent in the gummy smile patients compared to non-gummy smile ones.
Hayani A et al [39] also found this ratio significant in their study. Bishara [41]
reported that any increase in the lower facial height may result in a lip gap and
an excessive gingival display on a full smile.

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 PFH/AFH did not have any significant effect on the smile according to our
study (p=0.901>0.05). This might be explained by the fact that both PFH and
AFH were insignificant in our study. However, Hayani A et al [39] found a
significant decrease in PFH/AFH in the gummy smile group (p=0.003<0.05)
as well as Wu et al [40] who identified the craniofacial features of adolescents
with a gummy smile.
 UADH/AFH was slightly increased in the gummy smile group but it was not
found significant (p>0.05). LADH/AFH was higher in the gummy smile group
than the non-gummy smile group (mean value for gummy smile group 0,873
against 0,34 in the non-gummy smile group) yet was not significant in our
study. Hayani A et al [39] found the increased UADH/AFH ratio in the
gummy smile group statistically significant (p<0.05). However, they found
LADH/AFH ratio non-significant in their study. This increase in the
dentoalveolar measurements that we’ve mentioned can be interpreted as a
compensation for the increase of LAFH. Janson et al [42] confirms this
interpretation in his study in which he found a significant increase in
dentoalveolar heights in patients with increased lower facial height.
 UADH/UPDH did not present in our study a significant difference between
the gummy smile group and the non-gummy smile group (p=0.713>0.05).
Hayani A et al [39] also found this ratio non-significant.
 In this study, UADH/LADH ratio was found non-significant (p=0.743>0.05).
Hayani A et al [39] found that the increase of this variable in the gummy
smile group was not significant.
 LADH/LPDH ratio was found in our study non-significant (p=0.201>0.05).
On the other hand, Hayani A et al [39] found the difference between this ratio
in the gummy smile group and in the control group statistically significant
(p=0.01<0.05).

Discussion
Page 64
2.3.Multivariate approach:
The logistic regression model shows that a high smile arc, an increased exposed
gingival height during smile, a reduced UPDH, a decreased LADH, a reduced
overjet and a decreased ANB are the most significant parameters explaining the
presence of a non-gummy smile in this population. ANB did not have a
significant p value but it was kept in the model since it had a major influence on
the model.
The equation found was the following:
Logit(p)=7.975-1.677*SAS-1.355*GE-0.557*UPDH+0.244*LADH-
0.63*overjet-0.181*ANB.
(With SAS= smile arch’s situation, GE= gingival exposure, UPDH= upper
posterior dentoalveolar height and LADH= lower anterior dentoalveolar height).
Among those six variables, three were in our predictive model. The variables
included in the model explain 80% of the variationin the dependant variable
(non-gummy smile) which is a favorable percentage.
These variables found in our regression model were different than those that were
found by Barbosa D et al [9] in a study that they conducted on 163 children with
mixed dentition. They worked on occlusal and soft tissue variables. In their
regression model, they found four significant variables (malocclusion, facial low
third height, upper lip length smiling and incisor clinical crown height in
photogram) on which depends the presence of a gummy smile. Their model
explained only 48% of the variation in the dependent variable.
The reasons behind this difference between our study and Barbosa’s study might
be the age range chosen (they worked on a pediatric population whilst ours were
mainly young adults), the variables studied (we studied 87 variables whilst they
only studied 13) and the ethnic differences (South American Latinos against
North Africain Berbers).

Discussion
Page 65
Our study proved that smile arch’s situation and exposed gingival height as well
as occlusal relations and dentoalveolar factors are associated with a gummy
smile. Thus, they are preferably to be included in the clinical examination to have
a precise diagnosis and to target our treatment.
3. Treatment recommendations:
Thanks to our statistical analysis, we found an equation that helps in the
diagnosis of gummy smile. This equation is composed of six variables that
influence the smile line height. Among these variables, gingival exposure is the
first to notice when examining a patient with a gummy smile. Therefore, the first
thoughts of treatment plan are directly related to this specific factor. It is later,
when treatment details are planned, the other variables are evoked.
To be able to normalize our treatment options, we classified our patients who had
a gummy smile (gum exposure≥ 2mm) into a 2-grade scale based on the amount
of exposed gingiva as following:
 Grade 1: gum exposure is ≥ 2mm and <4mm.
 Grade 2: gum exposure ≥ 4mm.
Tab XXX: Gummy smile group’s classification.
Grade
Total
Grade 1 Grade 2
Count 44 26 70
% of Total 62.9% 37.1% 100,0%
Among our gummy smile patients, 62.9% were in grade one whilst 37.1% had a
grade 2 gummy smile.
Using this classification, the overall treatment options have become clearer.
3.1.Treatment options for Grade 1 patients:
For patients with a gum exposure between 2mm and strictly inferior to 4mm,
treatment options depend on the etiology.

Discussion
Page 66
We generally tend to treat a gummy smile with dentoalveolar origin with an
orthodontic treatment.
A gingivectomy can be preceded either associated to an orthodontic treatment if
the crown height is clinically decreased or associated to a gingival hypertrophy or
on its own in simpler cases when gummy smile has only a mucco-gingival
etiology.
This procedure can be made by simply removing the excess gingival tissue
overlaying the cervical enamel if periodontal probing indicates a normal sulcus
depth [2]. It can also be associated with an osteotomy in case where the probing
is not favorable.
Botulinum toxin type A (Botox) injections are also used in cases of a hypertonic
upper lip.
Hyaluronic acid can also be injected to increase the upper lip’s volume and
minimize the gum exposure.
3.2.Treatment options for Grade 2 patients:
These patients with a gingival display that exceeds 4mm present more complex
cases of gummy smile treatment.
Generally, treatment in these cases is multidisciplinary evoking an orthognathic
surgery associated to an orthodontic treatment and in some cases a periodontal
intervention as well.
Handling grade 2 gummy smile patients requires a lot of patience and time and a
good cooperation between the different specialists.

Conclusion
Page 67
CONCLUSION
A certain gingival exposure in a smile is considered a youthful feature. However,
if this gum display exceeds a certain height, the smile is perceived less attractive
and a gummy smile diagnosis is evoked.
Although the height of exposed gingival tissue from which smile is considered
unattractive is a bit of a controversy, a maximum height of 2 mm of gum
exposure seem to be tolerated by orthodontists [1,16,39].
Gummy smile’s prevalence found was increased compared to the expected
percentage. This phenomenon presents more than the half of this population.
A high smile is related to different factors. A low smile arc and an increased
height of exposed gingiva are highly associated to a high smile line. Increased
upper posterior dentoalveolar height, a decreased lower anterior dentoalveolar
height and an increased overjet and ANB play a significant role in the risk of
having a gummy smile.
Consequently, gummy smile is associated to the interaction of soft tissues,
dentoalveolar, skeletal and occlusal parameters. Therefore, treatment can include
in some complex cases a multidisciplinary approach.
Gummy smile is a challenge that orthodontists face every day and its treatment is
becoming more problematic considering the increase of social demands. This
study provides us with tools to establish a precise diagnosis and to target our
treatment following a classification of two grade scale.
This study is the first in Tunisia handling this subject. Its mean objective is to
participate in keeping dentistry updated and to simplify the treatment procedure.
It is important to mention that this study only reflects an orthodontic population
and not the whole Tunisian people due to its monocentrism.

Conclusion
Page 68
Further multicentric studies are required in Tunisia to give us a formula that can
be applied in a larger demographic spectrum.
Monastir, le …………………………
Avis des Directeurs de la Thèse Vu et permis d’imprimer
Le Doyen
Pr. Ag. Inès Dalel Omezzine Pr. Ben Rahma Ali

References
Page 69
REFERENCES
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Influence of gingival display on smile aesthetics in Japanese
European Journal of Orthodontics 2010; 32: 633–637
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Checklist of esthetic features to consider indiagnosing and treating excessive
gingivaldisplay (gummy smile).
Dental Press J Orthod 2011;16(2):131-57.
3. Van der Geld P, Oosterveld P, Schols J,Kuijpers-Jagtmand AM.
Smile line assessment comparing quantitativemeasurement and visual estimation
American Journal of Orthodontics and Dentofacial Orthopedics February
2011;139(2):131-157.
4.Toca E, Paris JC, Brouillet JL.
Exposition gingivale excessive quels sourires ?
L’information dentaire 2008 ; 11 :514-519.
5. Piral T.
Le sourire gingival.
Actualités Odonto-Stomatologiques 2008;242:167-178.
6. Van Der Geld P, Oosterveld P, Berge SJ, Kuijpers-Jagtman AM.
Tooth display and lip position during spontaneous and posed smilingin adults.
Acta Odontologica Scandinavica, 2008; 66: 207-213.
7. Lemeshow S, Hosmer DW J.
A review of goodness of fit statistics for use in the development of logistic
regression models.
Am J Epidemiol 1982; 115(1):92–106.
8.Sabri R.
Overview: The Eight Components of a Balanced Smile.
Journal of Clinical orthodontics 2005;39:155-167.

Thesis: A study of gummy smile in a Tunisian orthodontic population.

Thesis: A study of gummy smile in a Tunisian orthodontic population.

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