original article
Clinical and radiographic evaluation of maxillary central incisors exposure in patients undergoing maxillary advancement
Guilherme dos Santos Trento1, Felipe Bueno Rosettti Bernabé2, Delson João da Costa3, Nelson Luis Barbosa Rebellato3,
Leandro Eduardo Klüppel3, Rafaela Scariot4
DOI: http://dx.doi.org/10.1590/2177-6709.20.6.052-059.oar
Introduction: Patients with dentofacial deformities may undergo orthodontic or orthodontic-surgical treatment.
Both modalities can affect esthetics. Objective: This study aims to evaluate clinical and radiographic changes in exposure of maxillary central incisors occurring after orthognathic surgery for maxillary advancement. Methods: A total of 17
patients who underwent orthognathic surgery for maxillary advancement between September, 2010 and July, 2011 were
selected. Exposure of maxillary central incisors was evaluated clinically and by lateral cephalograms. Measurements were
taken one week before and three months after surgery. Data were paired in terms of sex, age, nasolabial angle, height and
thickness of the upper lip, the amount of maxillary advancement, clinical exposure and inclination of maxillary central
incisor by statistical tests (CI 95%). Results: After maxillary advancement, incisor clinical exposure had increased even
with relaxed lips and under forced smile. Moreover, there was a mean increase of 23.33% revealed by lateral cephalograms. There was an inverse correlation between upper lip thickness and incisors postsurgical exposure revealed by radiographic images (p = 0.002). Conclusions: Significant changes in the exposure of maxillary central incisors occur after
maxillary advancement, under the influence of some factors, especially lip thickness.
Keywords: Orthognathic surgery. Maxilla. Incisor. Esthetics.
Introdução: pacientes portadores de deformidades dentofaciais podem submeter-se a tratamento ortodôntico ou ortodôntico-cirúrgico. Ambos podem modificar a estética do paciente. Objetivo: esse estudo tem por objetivo avaliar, clinicamente e
radiograficamente, as mudanças na exposição dos incisivos centrais superiores em pacientes submetidos à cirurgia ortognática
de avanço de maxila. Métodos: foram selecionados 17 pacientes submetidos à cirurgia ortognática de avanço maxilar no período de setembro de 2010 a julho de 2011. A exposição dos incisivos centrais superiores foi avaliada clinicamente e por meio de
radiografias cefalométricas em norma lateral. Essas medidas foram tomadas uma semana antes e três meses depois da cirurgia.
Os dados foram, por meio de testes estatísticos (CI 95%), correlacionados por sexo, idade, ângulo nasolabial, altura e espessura
do lábio superior, quantidade de avanço maxilar, exposição clínica e inclinação dos incisivos centrais superiores. Resultados:
após o avanço maxilar, houve um aumento da exposição clínica dos incisivos tanto com o lábio superior relaxado quanto sob sorriso
forçado. Além disso, obteve-se um aumento médio de 23,33% na exposição dos incisivos nas radiografias cefalométricas em norma
lateral. Houve correlação inversa entre a espessura do lábio superior e a exposição pós-cirúrgica dos incisivos nas imagens radiográficas
(p = 0,002). Conclusão: mudanças significativas na exposição dos incisivos centrais superiores ocorrem após o avanço maxilar, sob
influências de certos fatores, especialmente a espessura do lábio superior.
Palavras-chave: Cirurgia ortognática. Maxila. Incisivo. Estética.
1
Resident in Oral and Maxillofacial Surgery, Universidade Federal do Paraná
(UFPR), Curitiba, Paraná, Brazil.
2
Specialist in Oral and Maxillofacial Surgery, Universidade Federal do Paraná
(UFPR), Curitiba, Paraná, Brazil.
3
Professor, Universidade Federal do Paraná (UFPR), Residency program in Oral
and Maxillofacial Surgery, Curitiba, Paraná, Brazil.
4
Professor, Universidade Positivo, Undergraduate program in Dentistry,
Curitiba, Paraná, Brazil.
» The authors report no commercial, proprietary or financial interest in the products
or companies described in this article.
© 2015 Dental Press Journal of Orthodontics
How to cite this article: Trento GS, Bernabé FBR, Costa DJ, Rebellato NLB,
Klüppel LE, Scariot R. Clinical and radiographic evaluation of maxillary central
incisors exposure in patients undergoing maxillary advancement. Dental Press J
Orthod. 2015 Nov-Dec;20(6):52-9.
DOI: http://dx.doi.org/10.1590/2177-6709.20.6.052-059.oar
Submitted: December 14, 2014 - Revised and accepted: August 04, 2015
Contact address: Guilherme dos Santos Trento
Av. Prof. Lothario Meissner, 632 - Jardim Botânico - Curitiba - PR - Brazil
CEP: 80210-170 – E-mail: guilhermetrento@yahoo.com.br
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Dental Press J Orthod. 2015 Nov-Dec;20(6):52-9
Trento GS, Bernabé FBR, Costa DJ, Rebellato NLB, Klüppel LE, Scariot R
original article
cephalometric study, Van Butsele et al17 evaluated soft
and hard tissue ratios in relation to maxillary advancement. The authors concluded that, for each millimeter
of maxillary advancement, the upper lip moved upward
in almost 30% the amount of advancement, in addition
to having an elongation of 1.7 mm. Del Santo et al18
evaluated 19 patients undergoing Le Fort I osteotomy
in order to study changes in the lips. The authors concluded that significant horizontal changes occur in the
upper lip when the maxilla is moved significantly anteroposteriorly at a ratio of 0.6 : 1. This is because the
vertical changes of the upper lip only occur when there
is a significant change in the anteroposterior position of
the maxillary basal bone. Given the above statement,
the objective of this study was to evaluate the clinical
and radiographic changes, with exposure of maxillary
central incisors, occurring after maxillary advancement.
INTRODUCTION
Severe malocclusion requires combined treatment of
surgery and Orthodontics. Less severe dentofacial deformities can be treated only by orthodontic treatment.1
Changes in the facial skeleton produced by this treatment modality affect not only the bones of the facial
skeleton, but also the relationship between hard and soft
tissues of the face.2 The most widely used technique for
repositioning the maxilla is Le Fort I osteotomy which
can be used for correction of vertical, anteroposterior and
transverse problems that involve the maxilla by means of
osteotomies across the anterior and lateral walls of this
structure.3 In cases of Class III malocclusion, maxillary
advancement aims to correct the bite, improve facial esthetics and harmonize the facial profile. Therefore, it is
important for the clinician to be able to predict soft tissue changes resulting from alterations of hard tissues.4
Soft tissue changes resulting from maxillary advancement via Le Fort I osteotomy have been reported to be
between 33% and 100%.5,6 Studies that describe the influence of soft tissue surgical corrections are limited.7-10
Nevertheless, some studies have shown that changes in
the soft tissues of the lips are influenced by the magnitude and direction of the jaw segment during surgery,11
and mainly by tone and lip thickness.5,12,13,14 In the case
of impaction, and with posterior or anterior movement
of the maxilla, it was found that the nasolabial angle is
increased despite a wide variation in tissue responses.9,15
Bundgaar, Melsen, and Terp7 hypothesized that angular
changes may be related to muscle function on the site of
osteotomy, and assessment of patient’s muscle pattern
could be important for predictive tracing of hard and soft
tissues. Stella et al,16 in order to assess the predictability
of changes in the soft tissue of the upper lip as a result of
maxillary advancement by the Le Fort I technique, selected 20 adult patients with a follow-up of six months.
Patients were subdivided into two groups based on lip
thickness: Group 1 (lips between 10 and 17-mm thick)
and Group 2 (greater than 17-mm thick). Most patients
showed a reduction in thickness of the upper lip, and
presented no increase in thickness. The reduction of lip
thickness was greater than 25% in most patients. It was
further stated that clinically relevant correlations cannot be made between the change of soft tissues and
bone advancement; however, when the reference is
the thickness of the upper lip, there is a better relationship between these two variables.15,16 In a retrospective
© 2015 Dental Press Journal of Orthodontics
MATERIAL AND METHODS
Sample selection: A total of 17 patients were selected
to undergo orthognathic surgery for maxillary advancement in the Department of Oral and Maxillofacial Surgery, Universidade Federal do Paraná, in the period of
September, 2010 to July, 2011. All patients (aged 18
or older) included in the study had Class III malocclusion and underwent maxillary advancement alone
or combined with mandibular surgery, with previous
orthodontic decompensation. Those who did not get
V-Y closure on the upper lip, did not present central
incisors and did not attend postoperative control were
excluded from the sample. This research was approved
by the Ethical Research Committee on Human Beings at the Human Health Department under number
CEP/ D: 921.046.10.05 and CAAE: 0033.0.091.00010. All patients signed an informed consent form.
Clinical analysis: All clinical measurements were
performed with patients seated and with their head in
natural position. Clinical analysis of maxillary central
incisors exposure with a relaxed lip and under forced
smile was performed one week before surgery and
three months after surgery. Clinical measurements
were taken with the aid of a digital caliper (VonderTM).
These measurements consisted of the distance between the lowest upper lip point and the incisal edge
of maxillary incisors.
Radiographic analysis: Lateral cephalograms were
performed one week before and three months after the
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original article
Clinical and radiographic evaluation of maxillary central incisors exposure in patients undergoing maxillary advancement
surgical procedure. All radiographs were performed by
the equipment Orthophos model 90 KV/12 mA (SiemensTM, Germany) located at the Department of Dental
Radiology. All radiographs were taken with the lips at
rest and in natural head position. Presurgical and postsurgical cephalograms were traced and analyzed at three different time intervals in order to perform intra-examiner
calibration, and through the intraclass correlation coefficient (pre ICC = 0.984 and post ICC = 0.993), which
allowed radiographic interpretation to be conducted by
the same examiner. After identifying the cephalometric
landmarks of interest to the study, we assessed exposure of maxillary central incisors in pre and postsurgical cephalograms. Three planes were traced from the
cephalometric landmarks: Frankfort horizontal plane
passing through the porion (higher point in the contour
of the ear canal) and orbitale (lowest point of the lower
edge of the contour of the orbital cavity); a plane passing
through the incisal edge of maxillary incisor; and a plane
passing through the stomion superius. These last two
planes were traced parallel to Frankfort horizontal plane.
Thus, after the three planes had been outlined, a measurement was made using Rickets’ rule from the incisal
edge of the maxillary central incisor to the stomion superius (distance between the plane passing through the
incisal edge and the plane passing through the stomion
Plane 1
superius) (Fig 1). Moreover, the nasolabial angle in the
presurgical radiographs was traced and measured (angle
formed by a line tangent to the columella through the
subnasale landmark and by a line tangent to the upper lip passing through the labial superius) (Fig 2). The
height (line joining subnasale and stomion superius) and
the width of the upper lip in the presurgical radiographs
were also traced and measured (Figs 3 and 4). Finally,
inclination of maxillary central incisors before and after
surgery were measured by the angle formed by the long
axis of the maxillary central incisor to the sella-nasion
line (plane passing through nasion and sella landmarks)
(Fig 5). Because surgeries were performed by different
surgeons, measurements were also taken on pre- and
postoperative radiographs to ensure that there were no
vertical movements of the maxillary segment. Thus, the
Frankfort horizontal plane and a line perpendicular to
this plane through the incisal edge were traced. Measurement was performed by the distance from the incisal
edge to the Frankfort horizontal plane (Fig 6).
Statistical analysis: Results were submitted to descriptive and statistical analysis. Statistical evaluation
was performed by frequency analysis and specific statistical tests using the Statistical Package for Social SciencesTM (version 15.0; SPSS Inc., Chicago, IL, USA) with
a 95% confidence interval.
Po
Or
Nasolabial angle
Plane 2
Plane 3
Figure 1 - Radiographic analysis of exposure of maxillary central incisor.
Plane 1: Frankfort horizontal plane (FH). Plane 2: Plane passing through stomion superius parallel to FH. Plane 3: Plane passing through the edge of
maxillary central incisor parallel to FH. Po = Porion. Or = Orbitale.
© 2015 Dental Press Journal of Orthodontics
Figure 2 - Measure of nasolabial angle (angle formed by a line tangent to
the columella through the subnasale and by a line tangent to the upper lip
passing through the labial superius).
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Trento GS, Bernabé FBR, Costa DJ, Rebellato NLB, Klüppel LE, Scariot R
original article
ANS
PNS
PNS
ANS
Sb
Ss
Figure 3 - Measure of upper lip height (plane passing through subnasale and
stomion superius). PNS = Posterior nasal spine. ANS = Anterior nasal spine.
Sb = Subnasale. Ss = Stomion superiorius.
S
Plane 1
Figure 4 - Measure of upper lip thickness. PNS = Posterior nasal spine.
ANS = Anterior nasal spine.
Na
Angle
Plane 2
Plane 1
Or
Plane 2
Figure 5 - Inclination of the upper central incisor to the Sella-Nasion plane.
Plane 1: Plane passing through sella and nasion. Plane 2: Plane passing
through the long axis of the upper central incisor. S = Sella. Na = Nasion.
Figure 6 - Measure from the incisal edge to the Frankfort horizontal plane.
Plane 1: Frankfort horizontal plane (FH). Plane 2: Plane perpendicular to
FH through the incisal edge of the upper central incisor. Po = Porion.
Or = Orbitale.
RESULTS
The sample consisted of 17 patients (14 females and
3 males). Sex was not correlated with increased clinical
and radiographic exposure of maxillary central incisors
after maxillary advancement (p = 0.423). Patients had
a mean age of 23 years in the sample (18-41). Age was
not correlated with increased clinical and radiographic
exposure of maxillary central incisors after orthognathic surgery (p = 0.650). Table 1 shows all values found
in the clinical and radiographic exposure of maxillary
central incisors both pretreatment and post-treatment.
Mean clinical exposure of maxillary central incisors
© 2015 Dental Press Journal of Orthodontics
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original article
Clinical and radiographic evaluation of maxillary central incisors exposure in patients undergoing maxillary advancement
with relaxed lip was 3.20 mm (0 – 7 mm) at the preoperative stage and 4.21 mm (0 – 6.60 mm) at the postoperative stage. Thus, there was a mean increase of 31%
after maxillary advancement. Mean clinical exposure of
maxillary central incisors under forced smile was 8.30
mm (4.50 – 14.10 mm) at the preoperative stage and
9.16 mm (5.10 – 15.02 mm) at the postoperative stage.
There was a statistical association between pre and postoperative measurements (Wilcoxon test / p = 0.001 CI 95%). Mean exposure of maxillary central incisors in
lateral cephalograms (presurgical) was 3.00 ± 1.46 mm,
while postsurgical mean was 3.70 ± 1.59 mm. Thus,
there was a mean increase in the exposure of central
incisors of 0.70 mm which corresponds to 23.33%.
The variables of exposure were also correlated with
these same teeth on preoperative and postoperative radiographs (paired Student’s t-test / p < 0.001 – CI 95%).
The mean amount of maxillary advancement was
5.11 mm. There was no statistical association between
increased radiographic exposure of maxillary central
incisors and the amount of maxillary advancement
(p = 0.951). Mean lip thickness was 14.05 ± 2.58 mm.
There was a statistically significant correlation between increased exposure of maxillary central incisors and lip thickness after maxillary advancement in
lateral cephalograms (p = 0.002 / r = 0.696 – CI 99%).
In this study, the nasolabial angle had a mean value of
101.70 ± 13.30°. This angle is not related to increased
exposure of maxillary central incisors in any measures
revealed by radiographic images (p = 0.398 – Spearman
Correlation Coefficient – CI 95%). Mean lip height
was 20.00 ± 2.29 mm. There was no statistically significant correlation between lip height and increased radiographic exposure of these teeth after surgery (Pearson’s
Correlation Coefficient – p = 0.357). Mean maxillary
incisors inclination was 113.35 ± 8.39° preoperatively.
This variable was not correlated with increased radiographic exposure of incisors (p = 0.533). Postoperative
inclination of maxillary incisors ranged as from an average of 114.88 ± 7.50°. There was no association between
postoperative inclination and radiographic exposure of
incisors after surgery (p = 0.814). It was not possible to
associate inclination of maxillary central incisors preoperatively with postoperatively by means of paired
Student’s t-test (p = 0.059), which had an average increase of one degree between these two surgical times.
There was no statistical association between increased
radiographic exposure of maxillary central incisors and
the difference in inclination before and after surgery
(p = 0.259). All results can be seen in Table 1.
Table 1 - Values of clinical and radiographic exposure of maxillary central incisors, pre and postoperatively; maxillary advancement; upper lip thickness preoperatively; nasolabial angle preoperatively; preoperatively height of the upper lip, and inclination of maxillary central incisor in pre and postoperative periods.
Mean ± SD
Median (Min-Max)
Radiographic exposure of maxillary
Preop.
3.00 ± 1.46
———
central incisor (mm)
Postop.
3.70 ± 1.59
p (CI = 95%)
< 0.001*
Preop.
Relaxed lip (mm)
3.20 (0 – 7.00)
———
Postop.
Preop.
Forced smile (mm)
= 0.004**
4.21 (0 – 6.61)
8.30 (4.50 - 14.10)
———
Postop.
= 0.002**
9.16 (5.10 – 15.02)
Maxillary advancement (mm)
———
———
5.00 (4.00 – 8.00)
———
Lip thickness (mm)
Preop.
14.05 ± 2.58
———
———
Nasolabial angle (degrees)
Preop.
102.29 ± 12.73
———
———
Lip height (mm)
Preop.
20.00 ± 5.36
———
———
Maxillary central incisor inclination
Preop.
113.35 ± 8.39
———
= 0.059*
(degrees)
Postop.
114.88 ± 7.50
———
= 0.059*
*Paired Student’s t-test; **Wilcoxon Test.
© 2015 Dental Press Journal of Orthodontics
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Trento GS, Bernabé FBR, Costa DJ, Rebellato NLB, Klüppel LE, Scariot R
original article
between movement of soft and hard tissues. Younger
adults with lack of dentoalveolar support do not show
facial concavity, which is usually associated with an older age group. Tonicity and thickness of soft tissues are
considered to be responsible for this difference.19 Flexibility of soft tissues, especially the lips, is directly influenced by tone and thickness.12 In this study, age was not
related to increased exposure of maxillary central incisors after surgery, since the vast majority of patients
were young adults (20 to 30 years old). In most patients
who underwent maxillary advancement alone or combined with another procedure in the mandible, the results indicated an increase in radiographic exposure of
maxillary central incisors after orthognathic surgery
(23.33%). There are two factors described in the literature that may influence this condition: soft tissue changes after orthognathic surgery and changes in bone and
tooth structure itself. Thus, with regard to a potential
change of soft tissues, we consider in this study some
factors that may contribute to this increase in exposure
of maxillary central incisors after maxillary advancement as far as the nasolabial angle, height, and thickness
of the lips. With regard to a potential change of hard
tissue, the amount of maxillary advancement, the inclination of maxillary central incisors before and after surgery, and the difference in inclination of these same
structures before and after surgery were considered. According to the results of this study, only soft tissue
changes influenced the increased exposure of incisors
after maxillary advancement. Soft tissue changes after
maxillary advancement may include changes in the positioning of the apex of the nose and nasolabial angle.15
The literature shows an increase in the nasolabial angle
of 1.20° with anterior repositioning of the maxilla and a
mean value of 0.65° for every 1 mm of advancement,
although there is a wide variation in tissue response,
some patients show an increase,9,15,19 while others show
a reduction12 in the postsurgical period. Bundgaar,
Melsen, and Terp7 hypothesized that an angular change
may be related to muscle function on the site of the osteotomy.7 Therefore, this change in the nasolabial angle
would influence exposure of maxillary central incisors,
which did not occur in this study. Of the variables analyzed in soft tissues, lip thickness was the most important, as there was a statistically significant correlation
between this variable and the radiographic measures.
At the same time, it is known that the clinical measure-
DISCUSSION
It is essential to be able to predict postoperative hard
tissue and facial profile changes resulting from orthognathic surgery in order to achieve functional and esthetic success of the procedure.13,19,20,21 The literature suggests that the etiology of soft tissue changes is postsurgical edema, increased support of bone tissue and the elevation of periosteum and muscles near the nose without correct repositioning.13 Facial changes in patients
undergoing orthognathic surgery performed in the upper jaw are multifactorial.15,19 If there was a pattern to
predict the amount of exposure of maxillary central incisors after orthodontic-surgical combined treatment,
there would be an ideal preoperative predictability.
However, it is difficult to have a standard or a universal
method to measure the exposure of teeth with relaxed
lips and at smiling because of the number of variables
that may be associated with it, such as the degree of
muscle activity, individual diversity factors and age.22
In addition, there are differences in the studies regarding
the selection of the sample, namely: the inclusion of patients with birth defects or syndromes in the same sample of patients with facial deformity; the use of different
radiological equipment to perform presurgical and postsurgical radiographs; the difficulty maintaining the correct position of the head and patients’ lips at the time of
radiograph; the exclusion or non-exclusion of segmental surgeries in the sample; only one or multiple motion
vectors in the maxilla in this sample; using the same
technique of incision and suture in the sample; in addition to osteoplasty (e.g., recontour of the anterior nasal
spine) and follow-up time.13,18,19 Other prominent factors are the complexity of anatomical structures in this
region of the face, the technical difficulty of correctly
visualizing the outline on the radiograph, the absence of
a specific and unique methodology as the means of performance, and comparison of tracings. Due to this diversity of factors that can alter the results, there is a limitation in comparing studies.18 Although women tend
to display greater maxillary incisor exposure at rest and
movement than men,23 the study found no relationship
of sex with increased exposure of maxillary central incisors after maxillary advancement. It is worth noting that
the research sample had a small number of men (n = 3),
which interfered in the analysis of results. Lee, Bailey,
and Proffit8 claimed that the physiological variation of
age and loss of muscle tone may explain the difference
© 2015 Dental Press Journal of Orthodontics
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Dental Press J Orthod. 2015 Nov-Dec;20(6):52-9
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Clinical and radiographic evaluation of maxillary central incisors exposure in patients undergoing maxillary advancement
ment of a muscular component is unattainable in practice. Radiograph measurements depend on the positioning of the lips during the radiographic procedure
which introduces the same significant variation.8,10,20
Considering natural lip thickness, the literature shows
that lips with thickness greater than 17 mm have a
smaller effect in relation to the movement of maxillary
advancement; however, the opposite occurs with thinner lips in comparison to those that had excellent correlation.24 Thinner lips tend to expose more of incisors
after maxillary advancement, which can be explained by
the fact that these lips follow maxillary advancement to
a greater degree compared to thicker lips.5,13,14 It is also
known that a thick lip can absorb the upper jaw amount
of advancement by distension,18 in addition to having a
firmer grip on the base of the nose, which prevents vertical and horizontal movements of the upper lip in response to maxillary movement.24 In our study, we did
not find any relation between the preoperative height of
the upper lip and increased radiographic exposure of
maxillary central incisors after maxillary advancement.
Although we found, in the literature, that shorter lips
tend to have greater vertical movement after surgery,25
small changes were observed in the vertical alteration of
the lip with insignificant statistical correlations after
maxillary advancement.9,21 Additionally, recent cephalometric investigations have found that movement of
hard and soft tissues after orthognathic operations were
strongly correlated horizontally but not vertically, and
the position of the lips could not be predicted accurately.12 Regarding the influence of hard tissues that concern the increased exposure of maxillary central incisors
after maxillary advancement, we evaluated the amount
of maxillary advancement. This anterior movement is
accompanied by a vertical and horizontal movement
that influences the exposure of incisors.17,20 In our study,
the amount of maxillary advancement was not statistically significant, since the vast majority of advances
were of the same size, between 4 mm (47%) and 5 mm
(23%). Another factor that could influence the final exposure of maxillary incisors could be an increased inclination of the incisor after orthognathic surgery for maxillary advancement, since orthodontic movement of
anterior teeth can influence and result in a change of
© 2015 Dental Press Journal of Orthodontics
upper lip position, thus influencing the exposure of
maxillary central incisors.19 It is worth noting that the option to measure the inclination of maxillary central incisors, before and after surgery, was based on the fact that
the second measurement was performed three months
after the procedure, which could lead to a biased result if
there was a change in the inclination of incisors by orthodontic movement, thus influencing the exposure of
maxillary incisors after surgery. In our study, the difference between inclination (pre- and postsurgical period)
of these teeth was not significant. There is no relationship
between the inclination of maxillary incisors by preoperatively increasing their exposure after surgery. There
was also no relationship between the difference in inclination before and after surgery of maxillary incisors and
increased exposure of these teeth after surgery.
CONCLUSIONS
1) Significant clinical change in the exposure of
maxillary central incisors occurs after maxillary advancement, with a mean increase of 31% with a relaxed
upper lip and 10.36% under forced smile.
2) Significant radiographic change in the exposure
of maxillary central incisors occurs after maxillary advancement, with a mean increase of 23.33% in lateral
cephalograms.
3) Increased exposure of maxillary central incisors
after maxillary advancement is mainly influenced by
upper lip thickness. Thin lips tend to expose more of
incisors after maxillary advancement, while thicker lips
expose less due to their greater adherence to the base of
the nose and by presenting more consistency.
4) There is a need for further studies relating to the
change in exposure of maxillary central incisors after
maxillary advancement.
Author contributions
Conceived and designed the study: RS, GST, FBRB;
Acquisition, analysis or interpretation: RS, GST, FBRB;
Drafted the study: RS, GST, FBRB; Data collection:
RS, FBRB; Wrote the article: RS, GST, FBRB; Critical revision of the article: RS, DJC, LEK, NLBR; Final
approval of the article: RS, DJC; Statistical analysis: RS;
Overall responsibility: RS, FBRB, DJC, LEK, NLBR.
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original article
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