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“Gingival (gummy) smile” – diagnostic value and treatment with botulinum neurotoxin

“Gingival (gummy) smile” –
diagnostic value and treatment
with botulinum neurotoxin
M.I. Soykher1, O.R. Orlova 1, M.G. Soyher1, L.R. Mingazova 1, EM Soyher2

Gummy smile, facial aesthetics, aetiology, treatment, botulinum toxin
Summary:
Smile is an important human facial expression of nonverbal communication.
Smile aesthetics represent a target for minimal invasive procedures
such as botulinum neurotoxin injections for improvement and
correction. We present pathogenesis, diagnostic relevance and treatment
options of so-called gingival or gummy smile. The aesthetic correction
of gummy smile is a multidisciplinary task.

Introduction
Today, more and more people are striving to realize [4, 14] in
their own life the motto: “everything in a human being should
be perfect” [15]. Mostly, we pay a lot of attention to our appearance
and special importance is attached to our face [5, 6].
Every unique human face has important personal significance
for each of us. Smile and lips are the leading factors in the
perception of face aesthetics. Many authors like Pererverzev
(1978), Khoroshilkina (1979), Persin (1988), Polma L (1996,
2010), Arsemima (1998), Ricketts (1981), Bishara (1985), Bacceti
(2000), Sarver (2001), and Ackerman (2004) made great
contributions to the study of the issue of face aesthetics and
its violations.
The motivation of patients for dental treatment in recent
years is increasingly aimed at obtaining an aesthetic result.
Analysis of the reasons why patients turn to dentists showed
[7, 11], that 23.0 % of patients want to improve the aesthetic
appearance of their teeth, 71.2 % orthodontic patients want to
improve face and teeth aesthetics such as reconstruction of the
teeth rows. During the last years, facial aesthetics is especially
associated with the smile zone. The smile zone is a special
structural, a functional and aesthetically significant area. It
consists of different macro- (facial and labial) and micro- (gingival
and tooth crowning) parameters [3].

The smile formation process divides into 4 stages:
1. stage – lips are closed
2. stage – lips are ajar (half-opened)
3. stage – natural smile (three quarters opened lips)
4. stage – broad smile.
Currently, smile analysis is the key to diagnosis and planning
of rehabilitation of dental patients. A smile can destroy or
emphasize the face harmony. Therefore, an attractive smile
becomes an important indicator of successful dental rehabilitation.
The clinical value of a harmonious balance is determined
by the limits of the possible effect on soft tissues and
the direction of orthopedic treatment, which allows to achieve
the best aesthetic result.
What is “the perfect smile”? Are there any clear criteria for
this concept? We can easily tell which smile is beautiful, but
it is difficult for us to describe those characteristics, that creates
it. Many investigations of the problem of aesthetic facial
disorders of young patients indicates the presence of “gingival
smile” in 10–15 % of cases.
Actually, smile aesthetics depends on: ratio parameters
between teeth and gums, their compliance with the rules of
structural beauty, the ratio between the teeth and lips parameters
and their harmonious integration with the components
of the face. Mimic muscles are the main component of a smile
[32, 33]. Approximately 7 % of men and 14 % of women have
excessive visualization of gums with a smile. Excessive gum
visualization is a descriptive term rather than diagnosis that
involves the mandatory conduct of a specific treatment.
Gummy smile (or gingival smile) – it’s a kind of structure
of tissues of the oral cavity, wherein smile occurs during displacement
of the upper lip exposing the gums. For the correct
diagnosis doctor requires knowledge in the field of facial aesthetics.
The main parameter of the estimation is the height of
the face oval. The height of the middle part of the face should
be equal to the height of the lower part with a relaxed state of
mimic muscles. A „gummy smile“ may be a symptom of a disorder
in structures of the facial skeleton and hyperactive facial
muscles (Fig. 1).
Anatomical reference point of the middle part of the face
is glabella – the most prominent point of the frontal bone
between the superciliary arches and the lower point of the nasal septum. The lower part is measured from the bottom
point of the nasal septum to the lowest point of the soft tissues
of the mandibula, i.e. the lower edge of the chin.
It is necessary to measure the length of the upper lip after
making assessment of the height of the face. In the state of
relaxation of the facial muscles length from the bottom of the
nasal septum up to the lower edge of the upper lip is 20–22 mm
on average for young women (Fig. 2a) and 22–24 mm for young
men. In this case for women, 3–4 mm maxillary central incisors
are usually visualized (Fig. 2b), and 2 mm less for men. Over
time, there is a trend to upper lip lengthening.
Short or hyperactive upper lip is one of the factors forming
a “gummy smile”. Usually, with a broad smile, teeth crowns
10–11 mm long are completely visible. However, for patient
with a hyperactive upper lip these parameters can be raised in
1.5 2 times (Fig. 3).
In addition, excessive lengthening of the teeth of the frontal
group of the maxilla [20] leads to a displacement of the gingiva
together with the underlying bone, and their lower position
leads to the appearance of a „gummy smile“.
The reason of excessive visualization of the gum also might
be an increase in the height of the mandible, which makes
the lower part of the face longer relatively to the middle part
[16, 18, 22]. According to Jiao Wei et al. (2015), one of the aetiological
factors of the „gingival smile“ may be dysplasia of the
nasal septum [21]. The most complicated case that require special
attention – is a combination of several factors.
Smile is unique for each person. There are several classifications
of smiles. According to the Rubin and Philips classification,
there are three basic types of smile [12, 30, 31].
The first type is a commissural smile („La Gioconda‘s smile“)
– occurs in 67 % of people. When smiling, the corners of the
lips move laterally upwards by 7–22 mm. The corners of the
lips (commissures) occupy a position above the upper lip and
the lateral part of the lips forms an angle of 40° (more often
24–38°) to the horizon. Lips form two curved arcs, in the gleam
of them only the upper teeth are visible, sometimes even wisdom
teeth. Zygomaticus major and minor muscles are involved
in the formation of this type of smile.
The second type of smile – „canine“ or „labial“ – is observed
at 31 % of people. It is formed without a significant shift up the
corners of the mouth. Upper lip rises upwards, exposing 6–8
upper teeth, lower teeth are closed with lower lip. The lower lip
takes the form of an arch, the upper one has curves, in one of
which the canines are exposed (this is the reason of the characteristic
name). Muscles lifting the upper lip and the one lifting
the upper lip and the wing of the nose are involved in the
formation of this type of smile.
The third type – „full denture“ or „complex“ smile – found
at 2 % of people. With a smile, both upper and lower teeth are
exposed and the lips have the form of two practically parallel
lines. The maximum number of antagonist muscles of middle
and lower third of the face is involved in the formation of this
type of smile. Therefore, the key characteristic of this smile –
strong muscular tension and displacement of the lower lip down
and backward [13].
Multifactor analysis [10] (2009) carried out by Polma
allowed to reveal a syndrome, accompanying unaesthetic types
of smiles, for which patients complain. A high type of smile
(„gummy“ smile) is common not only due to vertical enlargement
of the upper jaw, or the increase in the height of the
lower part of the face and the prevalence of the vertical type
of growth, but also as a result of soft tissue anatomy. In 90 %
of cases a straight or downward bending of the upper lip is
noted. Large percentage of „gummy“ smiles (90 %) arises due to anterior rotation of the upper jaw, and in 75 % of cases it is
accompanied by a retraction of incisors of the upper jaw.
There are five variations for exposing teeth and gums
in a smile:
Type 1 – only the upper teeth;
Type 2 – upper teeth and more than 3 mm of gum;
Type 3 – only lower teeth;
Type 4 – upper and lower teeth;
Type 5 – neither upper nor lower teeth.

With aging, there is an elongation of the upper lip occurs with
simultaneous reduction of the alveolar processes of the upper
jaw and the maxillary bone in general. Against this background,
the exposure of the gum with a smile is leveled. Mazzuco
and Hexsel suggested an aesthetic-functional classification
of „gingival smile“ [23, 24] (Tab. 1).

Multifactorial analysis of the smile and its consistent design
are the key stages of diagnosis and planning aesthetic correction.
Diagnosis of smile aesthetics disorders should be conducted
on an interdisciplinary basis, acknowledging the standards
of harmonious smile, professionally installed for different
age-sex and ethnic groups.
The plan for aesthetic correction of the „gummy smile“ is developed
after an accurate diagnosis and includes the use of both
orthodontic correction and maxillofacial surgery, also the use of
botulinum neuroprotein, for mimic muscle relaxation [21] (Fig. 4).
According to various authors injections of botulinum neuroprotein
(or botulinum toxin) are necessary for patients with
gingival smile for reduce hypermobility of the upper lip [8, 12,
25, 29]. The main target muscle is the one that lifts the upper
lip (m. levator labii superioris) together with m. zygomaticus
minor, m. zygomaticus major, m. depressor septi nasi, m. orbicularis
oris [17, 28] (Fig. 5).
Injection of botulinum toxin into the muscle lifting the upper
lip may be accompanied sometimes by ptosis of the upper lip
and its excessive elongation, protrusion of the lower lip and its
asymmetry [19, 32].
The mechanism of action of the botulinum neuroprotein is due
to the progress of chemodenervation – direct peripheral influence
on motor fibers (neuromuscular transmission), binding to
the presynaptic terminal and blockade of transport protein, that
takes from 1 to 3 days, so the effect of muscle relaxation begins to
manifest a few days after the injection of botulinum toxin into the
muscles [1]. The use botulinum toxin for the correction of muscle
hypertonicity is based on the following positions [3]:
1. Botulinum toxin provides long lasting muscle relaxation,
that allows to break the vicious circle of muscle tension and
pain, and to eliminate nerve compression by the tense muscle,
if the last exists.
2. Important advantages of treating with botulinum toxin are
its local, predictable, dose- dependent effect and a low risk of
systemic side effects......

Authors Correspondence:
M. I. Soykher, M.D.
Biotechnology and Interdisciplinary Dentistry Institute
Komsomolsky Prospect 32, corpus 2
Moscow, Russia
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Group
I
II
III
IV
Type of smile
Frontal
Side
Mixed
Asymmetrical
GD (mm) M\F
After 7 days
17
14
16.5
13.5
GD (mm) M\F
After 14 days
12
10
13
10
GD (mm) M\F
After 28 days
9
9
10
9
GD (mm) M\F
After 6 months
20
18
20
18
Table 4. The dynamics of treatment response.
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