Changes in soft tissue facial profile of class II skeletal malocclusion patients with retrognathic mandible treated with twin block appliance

Abstract

Introduction: The soft tissue aspect in orthodontics treatment has gained attention in the last few years. The soft tissue profile is said to reflect the underlying skeletal profile, which causes a convex profile in patients with class II skeletal malocclusion. This research was aimed to determine the changes in the soft tissue facial profile of class II skeletal malocclusion patients with retrognathic mandible after twin block treatment. Methods: The type of research used in this study was retrospective descriptive research with paired t-test. The population was children aged 10-13 years old with class II skeletal malocclusion that were treated with twin block appliance in the Faculty of Dentistry Universitas Padjadjaran, Indonesia. The results of soft tissue changes before and after twin block treatment were compared. Results: There was an insignificant increase in soft tissue profile angle and Holdaway’s soft tissue angle after twin block treatment (p > 0.05). Whereas, Holdaway’s H-angle was decreasing and Merrifield’s Z-angle was increasing after twin block treatment, with statistically significant difference (p < 0.05). Conclusion: There was a decrease of H-angle, indicates a reduction in facial convexity and improvement of the facial profile after twin block treatment, but no difference in soft tissue profile angle and Holdaway’s soft tissue angle after twin block treatment.

Keywords: Facial soft tissue profile, class II skeletal malocclusion, retrognathic mandible, twin block appliance

Full text

32
Padjadjaran J Dent. 2019; 31(1): 32-37
#Corresponding author: Gita Gayatri, Department of Orthodontics, Faculty of Dentistry, Universitas Padjadjaran,
Indonesia. Sekeloa Selatan I, Bandung, West Java, Indonesia, 40132. Phone: +6287822233418; Email: gita.gayatri@fkg.
unpad.ac.id
p-ISSN 1979-0201, e-ISSN 2549-6212; Available from: http://jurnal.unpad.ac.id/pjd/article/view/21154
DOI: 10.24198/pjd.vol31no1.21154
Submission: Aug 14, 2017; Reviewed: Jun 7, 2018; Resubmit for review: Jan 16, 2019; Accepted: Feb 21, 2019; Published
online: Mar 29, 2019
Changes in soft tissue facial prole of class II skeletal
malocclusion patients with retrognathic mandible treated
with twin block appliance
Ng Hui Lin*, Eky Soeria Soemantri*, Gita Gayatri*#
*Department of Orthodontics, Faculty of Dentistry, Universitas Padjadjaran, Indonesia
ABSTRACT
Introduction: The soft tissue aspect in orthodontics treatment has gained attention in the last few years.
The soft tissue prole is said to reect the underlying skeletal prole, which causes a convex prole in
patients with class II skeletal malocclusion. This research was aimed to determine the changes in the soft
tissue facial prole of class II skeletal malocclusion patients with retrognathic mandible after twin block
treatment. Methods: The type of research used in this study was retrospective descriptive research with
paired t-test. The population was children aged 10-13 years old with class II skeletal malocclusion that
were treated with twin block appliance in the Faculty of Dentistry Universitas Padjadjaran, Indonesia.
The results of soft tissue changes before and after twin block treatment were compared. Results: There
was an insignicant increase in soft tissue prole angle and Holdaway’s soft tissue angle after twin
block treatment (p > 0.05). Whereas, Holdaway’s H-angle was decreasing and Merrield’s Z-angle was
increasing after twin block treatment, with statistically signicant dierence (p < 0.05). Conclusion:
There was a decrease of H-angle, indicates a reduction in facial convexity and improvement of the facial
prole after twin block treatment, but no dierence in soft tissue prole angle and Holdaway’s soft
tissue angle after twin block treatment.
Keywords: Facial soft tissue prole, class II skeletal malocclusion, retrognathic mandible, twin block
appliance
INTRODUCTION
In recent years, the basic fundamental concept
of orthodontics is undergoing a paradigm shift.
Greater attention is paid to the soft tissue aspects
without neglecting the dental and skeletal
components.1 According to McNamara mandibular
skeletal retrusion is the most common single

33
Changes in soft tissue facial prole of class II skeletal malocclusion patients with retrognathic mandible (Lin et al.)
characteristic of Class II malocclusion.2 Soft tissue
facial prole is closely related to the underlying
skeletal prole. This character often causes
patient with Class II malocclusion to have a convex
prole.3 Male facial proles with bi-maxillary
protrusion and a female prole with retruded
mandible were considered the least attractive.
Whereas, straight facial prole was perceived
to be highly attractive by both expert and non-
expert groups.4
A study carried out in Jakarta, Indonesia
has found that the prevalence of malocclusion in
children aged 12-14 is 83.3% and the percentage
of Class II malocclusion patients is 31.6%. The
same study also found that 77.4% of the Class II
patients required orthodontic treatment.5
There are many treatment options for Class
II malocclusion and the usual option in treating
Class II skeletal problems is growth modication.
There are three types of orthodontic appliances
used for growth modication of Class II skeletal
problems namely extraoral force appliance,
functional appliance and interarch elastic
traction. The ideal indication of skeletal Class II
malocclusion with retrognathic mandible is the
functional appliances.6
The Twin Block is a kind of functional
appliance and is often regarded as the most
“patient friendly” due to its comfortable, ecient
and aesthetic design. A very unique feature of the
Twin Block is that this appliance is constructed into
two separate upper and lower appliances. Just like
any other functional appliance, the twin block is
designed to position the mandible downward and
forward to stimulate mandibular growth. The best
time to wear the twin block appliance is during
active growth period.7
Many researchers have reported the eect
of Twin Block on skeletal structure. However,
there is scant number of study on the soft tissue
changes after Twin Block treatment especially in
Bandung, Indonesia. Therefore, this research was
aimed to determine the changes in the soft tissue
facial prole of class II skeletal malocclusion
patients with retrognathic mandible after twin
block treatment.
METHODS
The type of research was retrospective
descriptive research with paired t-test whereby
the measurements of the same variable at two
dierent points were compared. In this study, the
collected data were the cephalometrics before
and after Twin Block treatment and the angular
value of the soft tissue facial prole before and
after treatment.
The sampling method was total sampling
whereby all patients who fullled the inclusion
criteria of the population will be selected as
the sample. The sample consisted of 6 subjects
who had undergone Twin Block treatment at the
Department of Orthodontics, Faculty of Dentistry,
Universitas Padjadjaran, Bandung, Indonesia.
Ethical approval for the study was obtained from
the Ethical Committee of the Faculty of Medicine
Universitas Padjadjaran. The inclusion criteria
applied for this study were male and female, class
II skeletal relationship (anb > 4°), retrognathic
mandible (snb < 78°), class II skeletal relationship
with normal maxilla (sna = 82° ± 2°), convex facial
prole.
There were a total number of six samples
that fullled the criteria. Cephalometric
radiographs of the selected samples were traced
manually. Seven landmarks used in this study
namely Po (Porion), Or (Orbitale), n (soft tissue
nasion), sn (subnasale), ls (labrale superius), li
(labrale inferius) and pg (soft tissue pogonion) as
shown in Figure 1.
Seven reference lines constructed were as
follows: (1) H line, (2) Z line, (3) soft tissue facial
line, (4) Frankfort plane, (6) n-sn line and (7) sn-
pog line. The H line is a tangent to the chin point
(pog) and upper lip (ls), whereas the soft tissue
plane is a line drawn from the skin nasion (n) to
the skin pogonion (pg). The intersection of these
two lines will form an acute angle which is known
as the H angle.
The Z line is the tangent to the soft tissue
pogonion and lips whereas the Frankfort plane is
a line that connects the lowest point of the orbit
and the upper margin of the bony auditory meatus.

34
Padjadjaran J Dent. 2019; 31(1): 32-37
The intersection of these two lines will form an
acute angle, which is known as the Z angle.
The n-sn line and sn-pog line are
constructed. The intersection of these two lines
will form an obtuse angle, which is known as the
Soft Tissue Prole angle. Lastly, the Soft Tissue
angle is an angle formed between Frankfort plane
and the soft tissue facial plane.
All the four angles mentioned above were
measured and recorded in angular measurements.
The measurements were tabulated and analysed
using the SPSS software. A paired t-test was used
to compare the changes before and after the
treatment.
To evaluate the method error, three
randomly selected cephalometrics from the
samples collected were traced manually. After
tracing, the Soft Tissue angle, Z angle, H angle and
Soft Tissue Prole angle were measured and the
values were recorded. The same cephalometrics
are retraced after one week and the same angles
as mentioned above were measured again and the
values were recorded. Paired t-test was conducted
to compare the values of the rst tracing and the
second tracing, with signicance level of 0.05.
The results showed no signicant dierences,
indicating no random error.
RESULTS
There were a total of 6 patients who fullled
the inclusion criteria. There were 3 males and
3 females aged 10-13 years. These patients
were treated with Twin Block appliance for
phase I treatment before proceeding to phase II
treatment. According to Table 1, the dierence of
the Z angle before and after Twin Block treatment
is signicant. The mean value of the Z angle before
the treatment is 55.58 degrees whereas the mean
value of the Z angle after the treatment is 62.08
degrees. This shows that the soft tissue chin has
moved forward after Twin Block treatment.
Based on Table 1, the dierence of H
angle before and after Twin Block treatment is
signicant. The mean value of H angle before
treatment is 28.58 whereas the mean value after
treatment is 24.83 degrees. The H angle is closely
related to facial convexity. Holdaway stated that
as skeletal convexity increases, the H angle must
also increase. This result showed that the facial
convexity of the patients decreased after Twin
Block treatment.
The dierence of the soft tissue angle before
and after Twin Block treatment is not signicant.
The mean value of the soft tissue angle before
treatment is 86.67 degrees, which means that the
entire sample has a slightly retrusive mandible.
After Twin Block treatment, the mean value of
the soft tissue angle is 87.33 degrees. Just as
expected, the soft tissue angle increases after
treatment because of the forward growth of the
mandible. However, the dierence that occurred
is very small and is not signicant statistically.
The dierence of Soft Tissue Prole angle
before and after treatment is not signicant. The
mean values of soft tissue prole angle before and
after treatment are 157.83 degrees and 159.75
degrees respectively. The angle increased after
Twin Block treatment due to the decrease of facial
convexity. However, the dierence that occurred
is very little and is not signicant in statistical
point of view.
DISCUSSION
Class II skeletal malocclusion is often related to
mandibular retrognathism, which results in larger
facial convexity and convex facial prole is often
Figure 1. Landmarks used in the study: Po= Porion, Or=
Orbitale, n= soft tissue nasion, sn= subnasale, ls= labrale
superius, li= labrale inferius, pg= soft tissue pogonion. Soft
tissue angular measurements: (1) Soft Tissue angle, (2) Z
angle, (3) Soft Tissue Prole angle, (4) H angle23

35
Changes in soft tissue facial prole of class II skeletal malocclusion patients with retrognathic mandible (Lin et al.)
Table 1. Descriptive statistics for the soft tissue facial prole variable before and after twin block treatment
Angular
measurement
Before After P-value Signicance
Mean SD Mean SD
Z angle 55.58 4.32 62.08 5.77 0.017 s
H angle 28.58 4.34 24.83 5.34 0.046 s
Soft tissue angle 86.67 3.06 87.33 1.54 0.516 ns
Soft tissue prole angle 157.83 7.50 159.75 7.55 0.169 ns
Notes: s, signicant; ns, non signicant
regarded as less aesthetic when compared to other
classes.8 In this current research, all six patients
had a convex facial prole and Class II skeletal
relationship with retrognathic mandible before
orthodontic treatment. Patients with retrognathic
mandible are determined by value of SNB angle.
The patients in this study all have a SNB angle of
less than 78 degrees.
Contemporary orthodontic treatment
philosophies not only aimed to produce ideal
occlusion and functional improvement, but
also to optimize dental and facial aesthetic.9
Forward growth of the maxilla is slightly lesser in
patients wearing functional appliance because the
functional appliance positioned the mandibular
forward which will create a reciprocal force acted
distally on the maxilla and restricted its growth.
In this current study, the patients had small
reduction in the SNA angle after the treatment.
However, many researchers reported no restraint
in the maxilla forward growth therefore it is not
a major factor in functional appliance therapy.10
A signicant lengthening of the mandible
can be achieved when a functional appliance
therapy is performed at pubertal or immediately
postpubertal periods of skeletal development.
Recent study reported that functional appliance
therapy indicated at pubertal spurt followed
by xed appliance is very successful in treating
patients with unfavorable Class II malocclusion.
Besides that, this timing for growth modication
was reported to produce a long-term lengthening
of the mandible. Morever, a greater increase in
mandibular length and ramus was reported when
treatment is indicated during pubertal peak when
compared to treatment before puberty begins.11
The goal of functional appliance treatment
is to stimulate or redirect the growth of the
mandible in a favorable direction. The main
dierences in the eect of various functional
appliances are associated with the technique of
fabrication, bites construction and duration of
wear. Of all the removable and xed functional
appliances, the Twin Block and Herbst appliance
are the most eective in correcting Class II
malocclusions. According to a research carried
out in North India, Twin Block appliance was
found to be more eective in increasing the
extra mandibular length. Besides that, Twin Block
appliance can also restrict the forward movement
of maxillary molars, produce mesial movement of
the mandibular molar, retroclined the maxillary
incisors and proclined the mandibular incisors.
Twin Block appliance has greater skeletal
eect in molar correction and overjet reduction in
comparison to Mandibular Protraction Appliance-
IV (MPA-IV).10 The Twin Block appliance has gained
popularity in the United Kingdom. It consists
of upper and lower separable acrylic blocks
trimmed to an angle of 70 degrees. This less
bulky appearance and freedom in movement of
the mandibular increase the patient’s acceptance
compared to other functional appliance such as
monoblock.12
The Z angle measures the position of the
lower lips in relation to the upper lips. Further
mandibular growth could add thickness to the
total chin and change the relationship to upper
lip. Increase in total chin thickness will increase
the Z angle value.13 The Twin Block is a functional
appliance that positioned the mandible forward
and this action creates a reciprocal force acted
distally on the maxilla. This reciprocal force will
cause retraction of the maxillary central incisors
and changes the relation of the lower lips to the
upper lips.10 Khoja et al. reported that Z angle
increased when compared between treatment
and control group and the results are signicant.21
Similar results were reported in Turkey, whereby
the Z angle showed signicant dierence before

36
Padjadjaran J Dent. 2019; 31(1): 32-37
and after Twin Block treatment.14 However,
Janardhanan et al. reported non signicant
changes in Z angle.20
The H angle is closely related to the upper
lip position.15 According to a study in Turkey,
prole changes can happen after an orthodontic
treatment because of the retraction of upper
incisors.16 The Twin Block is usually designed with
a labial bow in the upper arch of the appliance and
this will create a maxillary dental retraction. This
eect of treatment will decrease the prominence
of the upper lip in relation to the overall soft
tissue prole.21 According to the analysis proposed
by Holdaway, the results of the current study
showed that the samples had a decrease in soft
tissue facial convexity. Although the values had
decreased, however the post-treatment values
did not fall within the ideal range as stated by
Holdaway. Baysal and Uysal reported similar
changes whereby the H angle was decreased after
Twin Block therapy.17 Khoja et al. also reported
similar results and their changes are statistically
signicant.21 In contrast, another study on the
soft tissue changes after twin block treatment by
Janardhanan et al. showed that the changes in H
angle was not signicant.20
The soft-tissue facial angle measures the
position of the lower jaw in relation to the upper
jaw. Holdaway ideally preferred this angle to
range between 90 to 92 degree. Value lesser than
91 degree shows retrusive mandible. However,
Holdaway recognized a wide range of acceptable
value, as high as ± seven degrees for some cases.16
However, the Twin block is an appliance that
increases the length of the mandible, at the same
time also increases the lower anterior face height.
Every increase of one-millimeter of the anterior
facial height will hide one-millimeter increase of
the mandible length and causes the chin point to
rotate downward and backward.18 This explains
why the increment of the soft tissue angle is so
small and is not signicant statistically.
Hard tissue prole tends to become
straighter with age however the soft tissue prole
shows fewer tendencies to straighten with age.
This is due to the dierences in growth of soft
tissue thickness covering the underlying hard
tissue. Findings have shown that there is a greater
increase in the thickness of soft tissue covering
the maxilla than in the mandibular symphysis.
Even though the soft tissue prole follows closely
to the skeletal chin growth, however this extra
soft tissue thickness growth around the maxilla has
compensate the dierences.19 The forward growth
of the mandible had increased the soft tissue
prole angle. However, at the same time the extra
growth of soft tissue covering the maxilla has
compensated the mandible growth. Therefore, the
dierence that occurred is very little and is not
signicant in statistical point of view. In contrast,
Baysal and Uysal reported similar changes, where
the soft tissue convexity measurements increased
after Twin Block treatment but their results are
signicant.17 Similar results were reported by
Chaudhary et al. whereby the soft tissue prole
angle increased signicantly after treatment.22
One of the benets of this research is to
guide the thinking and practice of orthodontists
and to aid in explaining the outcome of the
treatment to the patient. Besides, the results from
this research may also contribute information on
the changes of soft tissue facial prole using
Twin Block appliance and as a base data for
future research in orthodontics. However, there
are also limitations in this research. Khoja et al
mentioned about the importance of having control
group in order to assess the inuence of normal
growth that would have occurred without using
functional appliances21, which was not applied in
this research due to the lack of data in the Faculty
of Dentistry Universitas Padjadjaran.
CONCLUSION
There was a decrease of H-angle, indicates a
reduction in facial convexity and improvement
of the facial prole after twin block treatment,
but no dierence in soft tissue prole angle and
Holdaway’s soft tissue angle after twin block
treatment.
REFERENCES
1. Nanda R. Esthetics and Biomechanics in
Orthodontics. Elsevier Health Sciences 2012:
54.
2. McNamara JA. Components of class II
malocclusion in children 8-10 years of age.
The Angle Orthodontist. 1981; 51(3):177-202.
3. Singh MG, Vashisth P, Chaudhary S, Sinha

37
Changes in soft tissue facial prole of class II skeletal malocclusion patients with retrognathic mandible (Lin et al.)
A. Early treatment outcomes of class II
malocclusion with twin-block facial prole
and cephalometric changes. Journal of Oral
Biology and Craniofacial Research. 2012; 2(1):
61–6.
4. Abu Arqoub SH, Al-Khateeb SN. Perception
of facial prole attractiveness of dierent
antero-posterior and vertical proportions.
European Journal of Orthodontics. 2011;
33(1): 103–11.
5. Saptarini R, Gartika M, Runkat J. Penggunaan
Twin Block pada perawatan maloklusi kelas
II angle anak-anak. Journal of Dentistry
Indonesia. 2005; 12(2): 50-54.
6. Bishara SE. Textbook of Orthodontics.
Saunders. 2001: 335-351.
7. Clark W. Twin Block Functinal Therapy. Jp
Medical Ltd UK. 2014: 7-15.
8. Stephanos MSR, Facial Prole Self-
Identication. Proquest 2007: 12-13.
9. Shell TL, Woods MG. Perception of facial
esthetics: a comparison of similar class II cases
treated with attempted growth modication
or later orthognathic surgery. The Angle
Orthodontist. 2003; 73(4): 365-373.
10. Jena AK, Duggal R. Treatment eects of twin-
block and mandibular protraction appliance-
IV in the correctio of class II malocclusion. The
Angle Orthodontist. 2010; 80(3): 485-491.
11. Franchi L, Pavoni C, Faltin K Jr, McNamara JA
Jr, Cozza MP. Long-term skeletal and dental
eects and treatment timing for functional
appliances in class II malocclusion. The Angle
Orthodontist. 2013; 83(2), 334-340.
12. Flores-Mir C, Major MP, Major PW. Soft tissue
changes with xed functional appliances in
class II division 1. The Angle Orthodontist.
2006; 76(4): 712-720.
13. Merrield LL. The prole line as an aid in
critically evaluating facial esthetics. Am J
Orthodontics. 1966; 52(11), 804-822.
14. Varlik SK, Gültan A, Tümer N. Comparison
of the eects of twin block and activator
treatment on the soft tissue prole. European
Journal of Orthodontics. 2008; 30(2008): 128-
134.
15. Holdaway RA. A soft-tissue cephalometric
analysis and its use in orthodontic treatment
planning: Part II. American Journal of
Orthodontics. 1984; 85: 279-293.
16. Basciftci FA, Uysal T, Buyukerkmen A, Demir
A. The inuence of extraction treatment on
Holdaway soft-tisse measurements. The Angle
Orthodontist. 2004; 74(2): 167-173.
17. Baysal A, Uysal T. Soft tissue eects of twin
block and herbst appliances in patients with
class II division 1 mandibular retrognathy.
European Journal of Orthodontics. 2013;
35(1): 71-81.
18. Sharma AK, Sachdev V, Singla A, Kirtaniya
BC. Skeletal and dentoalveolar changes
concurrent to use of twin block appliance
in class II division I cases with a decient
mandible: A cephalometric study. Journal of
Indian Society of Pedodontics and Preventive
Dentistry. 2012; 30(3): 218-226.
19. Subtelny JD. The soft tissue prole, growth and
treatment changes. The Angle Orthodontist.
1961; 31(2), 105- 122.
20. Janardhanan, K., S Tamizharasi, KP Senthil
Kumar. Soft tissue cephalometric changes
after correction of skeletal class II with Twin
Block functional appliance therapy: A pilot
study. Journal of Indian Academy of Dental
Specialist Researchers. 2014; 1(2): 50-52.
21. Khoja A, Fida M,Shaikh A. Cephalometric
evaluation of the eects of the Twin Block
appliance in subjects with class II, divison
1 malocclusion amongst dierent cervical
vertebral maturation stages. Dental Press
Journal of Orthodontics. 2016; 21(3): 73-84.
22. Chaudhary D.C., Kumar P, Sharma M, Nehra K.
Comparative evaluation of soft tissue changes
one year post-treatment in Twin Block and
FORSUS FRD treated patients. Med J Armed
Forces India. 2016; 72(4): 362-366.
23. Kusnoto H. Penggunaan cephalometri
radiogra dalam bidang orthodonti. Jakarta:
Penerbit Universitas Trisakti; 1977.