A. FEKONJA et al.: ADDITIVE MANUFACTURING IN ORTHODONTICS
165–169
ADDITIVE MANUFACTURING IN ORTHODONTICS
DODAJALNE TEHNOLOGIJE V ORTODONTIJI
Anita Fekonja
1
, Nejc Ro{er
2
, Igor Drstven{ek
3
1
University of Maribor, Faculty of Medicine, Taborska ulica 8, 2000 Maribor, Slovenia
2
Interesansa – Institute for Production Technologies and Development, Teslova ulica 27, 1000 Ljubljana, Slovenia
3
University of Maribor, Faculty of Mechanical Engineering, Smetanova ulica 17, 2000 Maribor, Slovenia
Prejem rokopisa – received: 2018-07-15; sprejem za objavo – accepted for publication: 2018-10-18
doi:10.17222/mit.2018.154
In recent years, digitalization and Additive Manufacturing (AM) have opened new perspectives in the field of personalized
complex medical and dental prostheses production and could be very useful also in orthodontics. Additively manufactured clear
aligners for treating orthodontic malocclusions have been tested and evaluated. The treatment began with a three-dimensional
scan of the patient’s study cast and occlusion, followed by a treatment simulation using the software for the orthodontic
planning and design of teeth models in a normal occlusion. The aligners were made from a thermoplastic polyurethane (TPU)
foil by thermoforming it over the model made by laser sintering. The process has been tested and evaluated. Apart from the
relatively well-known clear aligner treatment, a new appliance for the treatment of Class II malocclusions in growing patients
has been developed. The fixed sagittal guidance (FSG) appliance is individually designed to fit on the upper molars. It consists
of a crown and occlusal inclined plane. The crown has been designed using 3D dental design software and produced by selective
laser melting (SLM) technology. After finishing the FSG is bonded on both upper molars. During closing of the jaw, the
appliance provides guidance anteriorly and inferiorly to correct the sagittal and vertical deficiency in growing patients and
produces favorable and measurable dentofacial and skeletal changes. These two different types of appliances represent the first
use of additive manufacturing for orthodontic praxis in Slovenia. The results show the great potential and future perspectives of
additive manufacturing in orthodontic treatment.
Keywords: additive manufacturing (AM), three-dimensional (3D), orthodontic appliance, malocclusion
V zadnjih letih sta digitalizacija in dodajalna tehnologija odprli nove mo`nosti na podro~ju izdelave individualnih kompleksnih
medicinskih in dentalnih pripomo~kov. Dodajalna tehnologija je lahko zelo koristna tudi v ortodontiji zaradi kompleksne oblike
zob in prilagojene proizvodnje aparatov. Za zdravljenje ortodontske malokluzije smo testirali prozorni zobni aparat, izdelan s
postopkom dodajalnih tehnologij. Zdravljenje se je za~elo s tridimenzionalnim skenom odlitka zob v okluziji. Sledila je simu-
lacija zdravljenja z uporabo programske opreme za ortodontsko na~rtovanje in izvoz STL modelov zob v normalni okluziji.
Prozorni ortodontski aparati so bili izdelani iz termoplasti~ne poliuretanske folije (TPU) s termoformiranjem preko modelov,
izdelanih z laserskim sintranjem. Poleg relativno dobro znanega zdravljenja s prozornimi ortodontskimi aparati smo razvili novo
vodilo za zdravljenje malokluzije razreda II pri odra{~ajo~ih pacientih. Fiksni aparat za sagitalno vodenje je individualno zasno-
van tako, da se popolnoma prilega zgornjima zadnjima ko~nikoma. Sestavljen je iz krone (kobalt-kromove zlitine) in okluzalno
nagnjene ravnine, izdelane iz materiala SR Chromasit. Krona je bila zasnovana s 3D programsko opremo za zobne aplikacije in
izdelana s tehnologijo selektivnega laserskega taljenja. Fiksni aparat za sagitalno vodenje ve`emo na oba zgornja ko~nika in
med zapiranjem ~eljusti vodi aparat spodnjo ~eljust v pravilni sagitalni in vertikalni polo`aj pri odra{~ajo~ih pacientih. Ti dve
razli~ni vrsti aparatov predstavljata prvo prakti~no uporabo dodajalnih tehnologij v ortodontiji v Sloveniji. Rezultati ka`ejo
velik potencial in perspektivo dodajalne tehnologije pri ortodontskem zdravljenju.
Klju~ne besede: dodajalne tehnologije, 3-dimenzionalno, ortodontski aparati, ortodontske nepravilnosti
1 INTRODUCTION
Additive Manufacturing (AM) is a common name for
technologies that build 3D objects by adding material in
a layer-by-layer form. The principle of layered pro-
duction makes them very suitable for the low-volume
production of parts with very complex shapes. The use of
AM technologies requires a digital model of the part, an
AM machine and a layering material. Once a CAD
model is produced, the AM machine reads the data from
the CAD file and lays down or adds successive layers of
liquid, powder, sheet or other material, in a layer-upon-
layer fashion to fabricate the 3D object. Because of its
suitability for the low-volume production of complex
parts, AM technology very soon found its way into
medical and especially dental applications.
1–9
Until
recently, orthodontic applications have been lagging
behind, but with the newest research and applicable
solutions
10
it is becoming clear that AM technologies
will also have to be considered in this field.
The clear aligner treatment is already well known in
orthodontics, but it is limited to a small number of
companies that offer this kind of service. AM machines
make it possible to transfer the whole value chain of the
clear aligner market into a single orthodontic laboratory
if the work of a dental technician can be avoided. This is
only possible if the whole workflow starts and finishes
inside the computer program, which outputs the 3D data
for the additive manufacturing of the final aligners. AM
also opens new possibilities for curing malocclusions of
different types. The fixed sagittal guidance (FSG)
appliance promotes the growth of the lower jaw in
Materiali in tehnologije / Materials and technology 53 (2019) 2, 165–169 165
UDK 616.314-089.23:616-76 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 53(2)165(2019)
*Corresponding author e-mail:
anita.fekonja1@guest.arnes.si

patients with class II malocclusions. Using AM tech-
nologies and modern dental scanning and planning
software the FSG appliance can be designed and pro-
duced between two sessions, thereby reducing the costs
and the time required by the orthodontist. This review
provides a brief discussion about the use of AM in
orthodontics.
2 EXPERIMENTAL PART
In recent times, digitalization has played an import-
ant role in the manufacture of dental parts. In both
appliances, the process began with a high-quality algi-
nate impression of the upper and lower jaw for the
working model. In next stage, the working model was
scanned by an optical 3D scanner to obtain the data for
the further digital workflow. Using an intraoral scanner,
this part can be streamlined by avoiding the casting and
scanning of the working model (Figure 1). But, even
though, the whole process of optical scanning of the
working models turned out to be at least as fast as the
process of intraoral scanning. Regardless of the process
for obtaining the digital data, the data need to be
exported in the form of an exact virtual replica of the
working model (Figure 2). The output file format is
usually STL (Surface Tessellation Language).
From this stage the manipulation of the virtual mo-
dels and the production of these two appliances differs.
2.1. Fixed sagittal guidance (FSG)
The virtual model is processed by the dental software
used for designing the fixed dental prosthetic elements.
The crown of the FSG is modeled and then manufactured
into the 3D part (crown of FSG) by selective laser
melting (SLM) out of Co-Cr alloy (Figure 3). SLM is
one of the AM technologies that uses a laser beam to
melt powdered metal in a layer-by-layer manner.
11
The
resulting product metal crown of the FSG is very
accurate, which ensured a perfect fit to the structure of
the tooth. The crown is ready to be covered by the
occlusal inclined plane made from SR Chromasit
material (Ivoclar Vivadent, Figure 4).
The inclination of the inclined plane to the occlusal
plane is individually designed according to the anatomi-
cal situation of the patient, thereby actively guiding the
mandible anteriorly during jaw closure. It is individually
made in the laboratory using an articulator. The con-
struction of a wax bite is necessary for the production of
the inclined plane. To register the bite for FSG manu-
facturing, the patient was asked to close his/her mouth in
A. FEKONJA et al.: ADDITIVE MANUFACTURING IN ORTHODONTICS
166 Materiali in tehnologije / Materials and technology 53 (2019) 2, 165–169
Figure 2: 3D virtual model
Figure 1: The working model is scanned with an intraoral scanner
Figure 4: Crown covered by occlusal inclined plane made from SR
Chromasit material (Ivoclar Vivadent) guides the mandible anteriorly
during jaw closure
Figure 3: Crown of FMBG manufactured by selective laser melting
(SLM) using Co-Cr alloy

the proper sagittal and vertical dimension. The
inclination of the inclined plane can be adjusted in the
laboratory depending on the specific case (severity of
Class II relationship, deep bite).
2.2. Clear aligner
The virtual working model is imported into a
software package for the orthodontic treatment planning
and the design of the teeth models in a normal occlusion.
Four different software packages were tested. All of
them enable the manual movement of the teeth in the
virtual jaw. In this way, the teeth are virtually moved into
the ideal positions that should be achieved with the clear
aligners treatment. The intermediate treatment stages
(the positions of the teeth) are automatically computed
and the virtual models of these stages are prepared for
exporting. The number of stages varies depending upon
the degree of irregularity.
12
At this stage no significant
differences have been found among the different
orthodontic software packages. However, among the four
packages only one enables the export of the STL model
of the clear aligner; the other three only enable exporting
of the model, which can be a serious shortcoming as the
AM materials evolve.
13
To export the aligners the soft-
ware must provide an interface where the thickness and
gum offset of the exported aligners can be adjusted.
Conventionally, aligners are made from a thermoplastic
polyurethane (TPU) foil (Figure 5) by thermoforming it
over the model made by laser sintering (SLS).
The orthodontic forces and the moments generated
by the thermoplastic aligners depend on the amount of
activation
14
and the material thickness.
15
The results
suggest that the activation of the lingual bodily move-
ment of the maxillary central incisor should not exceed
0.5 mm and the initial4dor5disimportant with res-
pect to the orthodontic treatment incorporating an
aligner. The technology has continued to improve clear
aligner treatments since their inception. Replacing the
impressions with increasingly more accurate intraoral
scanners, 3D printing instead of plaster models, indivi-
dual tooth movement and staging in virtual setups, and
improvements in aligner materials and attachments are
all examples of recent advances.
16
During the research
directly printed aligners (Figure 6) produced by
stereolitography (SLA) were tested. Several photocuring
resins that correspond to the medical devices directive
93/42/ECC for the production of Class IIa medical
devices entered the market in recent years. By adjusting
the thickness and post-curing process, these materials
can be used to directly produce aligners. Directly printed
aligners are cheaper to produce, but not as flexible as
thermoplastic polyurethane foil and not so transparent.
Once they are in the mouth mixed with saliva the visual
difference is minimal.
3 RESULTS
3.1. Fixed sagittal guidance (FSG)
Patients with different severity of Class II mal-
occlusion due to retrognathic mandible and deep bite
were successfully treated using a FSG appliance made
by SLM. The results were assessed through an analysis
of the study cast and lateral cephalographs before and
after treatment.
The study casts of all the patients after the treatment
showed a Class I relationship, and a proper overbite and
overjet. The analysis of the lateral cephalographs of all
the patients after the treatment showed a skeletal Class I
jaw relationship with the proper mandibular position,
reduced facial convexity and increased lower anterior
facial height (Table 1). The total improvement in the
A. FEKONJA et al.: ADDITIVE MANUFACTURING IN ORTHODONTICS
Materiali in tehnologije / Materials and technology 53 (2019) 2, 165–169 167
Figure 6: Directly printed aligner Figure 5: Thermoformed aligner

occlusal and soft-tissue relationships was the result of
dental, skeletal and soft-tissue changes.
Table 1: Comparison of cephalometric variables between pre-treat-
ment (T0) and post-treatment (T1) in patients treated with FSG
Cephalometric variable T0 T1
SNB (°) 76 77.5
SNPg (°) 78.5 79.5
ANB (°) 3 2.5
Wits (mm) 4 2
SN/PL (°) 7 6.5
SN/ML (°) 26.5 31
LAFH(mm) 61 63.5
UAFH/LAFH (per cent) 76.2 74.8
FH index (per cent) 66.7 65.9
U1/PL (°) 113 108
L1/ML(°) 93 93.5
Overbite (mm) 6.5 2.5
Overjet (mm) 7 3
3.2. Clear aligner
Clear aligner treatment (CAT) is an effective proce-
dure that can align and level the arches in non-growing
subjects. The anterior intrusion movement achievable
with CAT is comparable to that reported for the straight-
wire technique, but it is not effective in controlling the
anterior extrusion movement. Contrasting results have
been reported in relation to the posterior vertical control,
and a definite conclusion cannot be drawn. CAT is not
effective in controlling rotations, especially those of
rounded teeth. In this case, attachments are necessary. It
is effective in controlling the posterior but not the
anterior buccolingual inclination. CAT is effective in
controlling the upper molar bodily movement when a
distalization of 1.5 mm has been prescribed. CAT is not
based on aligners alone; it requires the use of auxiliaries
(attachments, interarch elastics, IPR, altered aligner
geometries) to improve the predictability of the ortho-
dontic movement.
17
Simple cases have been successfully
treated, typical for treating with clear aligners. Treating
more complicated cases, such as open bite, is harder to
achieve and includes the use of auxiliaries.
4 DISCUSSION
Freedom of design, mass customization, waste mini-
mization and the ability to manufacture complex struc-
tures, as well as fast prototyping, are the main benefits of
Additive Manufacturing (AM). In recent years, digitali-
zation and Additive Manufacturing (AM) have opened
new perspectives in the field of personalized complex
medical and dental prostheses production.
18
AM could
also be very useful in orthodontics because of the com-
plex shape of teeth and the customized production of
appliances.
2–10
The FSG appliance is completely individually de-
signed for patients with a Class II relationship due to a
retrognathic mandible. The FSG appliance, in closing the
jaw, guides the mandible anteriorly and inferiorly to
correct the sagittal and vertical deficiency, which
achieved an increase in the mandibular length and the
forward and downward movement of the mandible.
The function of the FSG appliance is similar to
elastic and flexible fixed units (Jasper jumper, Herbst
appliance) but without an influence on the lower
incisors’ proclination, reported by Pancherz,
19
Stucki and
Ingervall,
20
Weiland et al.,
21
Gohilot et al.,
22
Neves et
al.
23
So, the FSG is ideal in the case of proclined inci-
sors, because there is a great need to control the incisor
inclination.
Using the FSG appliance, the upper and lower jaw
are not connected, which allows the patient to open the
mouth fully and all the functional movements are almost
frictionless. Other fixed units (Jusper jumper, Herbst
appliance) connect the upper and lower jaws together
and therefore somewhat restrict the jaw’s movement.
A deep bite due to an excessive curve of the Spee
often accompanies a Class II malocclusion. With the
FSG appliance it is possible to level an excessive curve
of the Spee in the lower arch. The presented research
identified a decrease in the overbite due to leveling of the
Spee curve and a mandibular downward rotation.
FSG enables the concomitant use of a palatal arch in
the case of a narrow upper jaw, which is an additional
advantage of this method of treatment.
CAs are designed for each person individually. One
of the advantages of using the CA is the ability to
selectively orchestrate the dental movements. The
velocities of every tooth can be dictated and monitored
as the treatment is planned and executed. Periodontally
compromised teeth can also be almost left stationary
during the treatment with minimum and/or no mecha-
nical pressure.
Teeth are not 100 % predictable, so overcorrections
are necessary. During the research, an approximately
70 % predictability can be certified.
This method of treatment for simple cases is equally
effective as conventional fixed appliances. Conventional
fixed appliances have been more effective in malocclu-
sion treating, but treating with clear aligners is 30 %
faster
24
and they are barely visible.
CAs are easy to remove, and hence do not interfere
with maintaining hygiene. They are transparent and do
not interfere with speech.
5 CONCLUSIONS
In a treatment with a digital and fast procedure in
patients with Class II malocclusion due to a retrognathic
mandible, the results for the patients are promising,
although long-term results are not yet available.
Over the past 16 years, CA treatment has developed
from a technique for only treating mild crowding or the
spacing of anterior teeth to a technique that can be used
to treat almost any type of orthodontic problem. How-
A. FEKONJA et al.: ADDITIVE MANUFACTURING IN ORTHODONTICS
168 Materiali in tehnologije / Materials and technology 53 (2019) 2, 165–169

ever, to do so, it is important to understand the limi-
tations of the appliance and to be able to think "out of
the box" in treatment planning. Aligner materials and
attachments will continue to improve, which will allow
aligners to fit better and for longer periods of time and
result in better outcomes.
Acknowledgment
The authors would like to thank the Healthcare
Centre Maribor, Slovenia, for technical manufacturing of
the FSG and CA.
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Materiali in tehnologije / Materials and technology 53 (2019) 2, 165–169 169