the application of rapid prototyping technique in chin augmentation
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ORIGINAL ARTICLE
The Application of Rapid Prototyping Techniquein Chin Augmentation
Min Li Æ Xin Lin Æ Yongchen Xu
Received: 12 April 2009 / Accepted: 24 June 2009 / Published online: 30 July 2009
� Springer Science+Business Media, LLC and International Society of Aesthetic Plastic Surgery 2009
Abstract
Background This article discusses the application of
computer-aided design and rapid prototyping techniques in
prosthetic chin augmentation for mild microgenia.
Methods Nine cases of mild microgenia underwent an
electrobeam computer tomography scan. Then we per-
formed three-dimensional reconstruction and operative
design using computer software. According to the design,
we determined the shape and size of the prostheses and
made an individualized prosthesis for each chin augmen-
tation with the rapid prototyping technique.
Results With the application of computer-aided design
and a rapid prototyping technique, we could determine the
shape, size, and embedding location accurately. Prefabri-
cating the individual prosthesis model is useful in
improving the accuracy of treatment. In the nine cases of
mild microgenia, three received a silicone implant, four
received an ePTFE implant, and two received a Medpor
implant. All patients were satisfied with the results. During
follow-up at 6–12 months, all patients remained satisfied.
Conclusion The application of computer-aided design
and rapid prototyping techniques can offer surgeons the
ability to design an individualized ideal prosthesis for each
patient.
Keywords Computer-aided design � Rapid prototyping
technique � Microgenia � Chin augmentation
Microgenia is a kind of malformation of the lower face that
is caused by osteodysplasty of the chin with manifestation
as a small mental region and chin retraction. Recently,
people have been paying more attention to the shape of
their chin, and the number of patients desiring chin aug-
mentation has increased. The treatments for microgenia are
genioplasty and chin augmentation. Mild microgenia is
very common in our clinical practice. Plastic surgeons
often perform chin augmentation with a silicone or ePTFE
implant [1, 2]. In general, a surgeon evaluates a patient’s
microgenia by X-ray examination and then designs the
proper sized implant. During the operation, the surgeon
carves the implant using his clinical experiences to achieve
a satisfying outline. Even so, the surgeon can not get a
precise personalized prosthesis. To achieve a better result,
we used computer-aided design and a rapid prototyping
technique to design personalized chin implants preopera-
tively. With these two techniques, we prefabricate the
prosthesis mold as an intraoperative reference and get
satisfactory cosmetic results.
Materials and Methods
Clinical Data
There were nine female cases in this series ranging in ages
from 18 to 40 years. All cases presented with mild
microgenia and normal occlusion. All cases received chin
augmentation: three chose medical silicone implants, two
chose Medpor, and four chose ePTFE.
M. Li (&) � Y. Xu
Department of Traumatic and Aesthetic Surgery, Huangsi
Aesthetic Surgery Hospital, No. 9 Anwai Huangsi Street,
Beijing 100120, China
e-mail: elbert_lily@163.com
X. Lin
Department of Surgery, Unit 2, South Building, PLA General
Hospital, No. 28 Fuxing Road, Beijing 100853, China
123
Aesth Plast Surg (2010) 34:172–178
DOI 10.1007/s00266-009-9397-x
Three-Dimensional Reconstruction of Skull and
Prosthetic Model
All cases underwent a computer tomography (CT) scan of
the skull (C-150, Imatron, Hayward, CA, USA). Continu-
ous volume scanning was applied to collect imaging data
from the vertex of the cranial region to the mental region.
Scanning parameters were as follows: 130 kV voltage,
1.5 mm width, 216� angle of rotation, and 0.1 s exposure
time. All these data of slices were transferred to a com-
puter. Using 3DMsee (Gimmafei Technology Development
Co., Ltd., Beijing, China), three-dimensional reconstruc-
tion software, we abstracted the profiles of facies cranii and
soft tissue and got their vectorization diagrams. With these
data we were able to perform three-dimensional recon-
struction and get a stereo view of the facies cranii and soft
tissue (Figs. 1 and 2). In the same way, we scanned the
prosthesis and got its three-dimensional reconstruction
image. Then we performed the operational design and
simulation with the computer.
Operational Design and Simulation
We performed the operative design through computer-
aided three-dimensional reconstruction. First, we deter-
mined how long the mental region should be extended. We
measured the distance from the hairline to the glabella
(D1), from the glabella to the subnasal point (D2), and
between the subnasal point and the submentum (D3). The
difference between D3 and D1 or D3 and D2 was the
length of the chin extension (Fig. 3). Second, we had to
determine the thickness of the mental region. We marked
the nasal tip and lower lip, and extended the line from these
two points to the mental region. Then we measured the
vertical distance from this line to the pogonion; this was the
extended thickness of the mental region (Fig. 4). After that,
we simulated on the computer the implantation of the
Fig. 1 Three-dimensional reconstruction of skull
Fig. 2 Three-dimensional reconstruction of facial contour
Fig. 3 To determine how long the mental region should be extended,
the distances from the glabella to the subnasal point (D2) and from the
subnasal point to the submentum (D3) were measured. The difference
between D3 and D2 was the length of chin extension
Fig. 4 To determination the thickness of mental region, the nasal tip
and lower lip were marked and a line was extended from these two
points to the mental region. The vertical distance from this line to the
pogonion was the ideally extended thickness of the mental region
Aesth Plast Surg (2010) 34:172–178 173
123
prosthesis into the mental region. In accordance with the
above measurements and aesthetic standards, we per-
formed the operative design, adjusting the location of
prosthesis implantation to keep the connection of the
prosthesis border and mandible natural and smooth
(Fig. 5).
Manufacture of Prosthetic Mold
Using the rapid prototyping technique, we transferred the
computer-aided design of the prosthetic implant to a rapid-
form machine and made the prosthetic mold (Fig. 6). From
it we can make individual silicone implants.
Operative Procedure
First we put the prosthetic mold into the mental region and
marked the central line and its designed location with
methylene blue according to the preoperative plan. Then
we started local anesthesia and made a V-shaped incision
in the gingival sulcus of the intraoral mucous membrane of
the lower lip, which was more than 0.5 cm away from the
gingiva. After incising the mucous membrane, submucosa,
and periosteum, we dissected the periosteum in the pre-
marked region as a plane with a detacher. It was extremely
important to control bleeding and place the prosthesis
under the periosteum in the mental region. Finally, the
Fig. 5 Computer simulation of the implantation of the prosthesis into
the mental region. a Anterior view of skull with prosthesis. b Lateral
view of skull with prosthesis. c Loxosis view of skull with prosthesis.
d Anterior view of face with prosthesis. e Delineation of mental
region with prosthesis. Yellow line marks the extended length of the
mental region
174 Aesth Plast Surg (2010) 34:172–178
123
operational field was flushed with saline containing gen-
tamicin and the periosteum and mucous membrane were
sutured. We recommend pressure dressing for the opera-
tional field, a liquid diet for 3 days postoperatively, and
taking antibiotics orally for prophylaxis of infection.
Results
In our nine cases of mild microgenia, three received a
silicone implant, four received an ePTFE implant, and two
received a Medpor implant. All these prostheses were made
according to a preoperative design. Silicone implants can
be manufactured directly with the designed prosthetic
mold. However, Medpor and ePTFE implants had to be
carved to the shapes of the designed prosthetic molds. Each
prosthesis was implanted in accordance with the computer-
assisted preoperative design. Each operation resulted in a
satisfactory chin and facial shape (Figs. 7, 8, 9, 10, 11, 12,
13, 14, 15, 16, 17, 18) without complications. In the 6–12-
month follow-up, all patients were satisfied on the whole.
Fig. 6 a Anterior view of the
prosthetic model. b Dorsal view
of the recess of the prosthetic
model. c Anterior view of three-
dimensional reconstructed skull
model with prosthesis
Fig. 7 Preoperative front view of case 1
Fig. 8 Postoperative front view of case 1, six months after ePTFE
implantation
Aesth Plast Surg (2010) 34:172–178 175
123
Discussion
The mental region is an important part of the face. Its shape
and relative position with respect to the upper mandible
and nose directly affect their harmony and facial outlook.
Different from micrognathia, microgenia appears mainly as
the retraction of the mental region with normal, decreased,
or increased mandible length in the lengthwise direction.
McCarthy [3] classified microgenia into two categories:
normal occlusion and abnormal occlusion accompanied by
abnormal articulation. McCarthy et al. [4] had another
classification of microgenia according to the longitude
proportion of the vertical and sagittal mandible planes.
Type I included decreased sagittal length but normal ver-
tical length. Type II included decreased vertical length but
normal sagittal length. Type III had decreased sagittal and
vertical lengths. Type IV had decreased sagittal length but
increased vertical length. A short chin, mild mandibular
retraction, and microgenia with normal occlusion were all
indications for mental region augmentation. Silicone,
Fig. 9 Preoperative profile view of case 1
Fig. 10 Postoperative profile view of case 1, six months after ePTFE
implantation
Fig. 11 Preoperative front view of case 2
Fig. 12 Postoperative front view of case 2, six months after ePTFE
implantation
176 Aesth Plast Surg (2010) 34:172–178
123
ePTFE, and Medpor were optional filling materials. In
general, silicone and ePTFE implants did not need fixation
but Medpor implants had to be fixed with titanium nails.
Computer aided surgery (CAS) [5] has become a part of
clinical medicine. With the application of computer-assis-
ted image analysis and three dimensional reconstructions,
we can get more precise information than by traditional
methods. Also, model surgery based on a rapid prototyping
technique has become an important adjuvant to modern
surgery. Rapid prototyping techniques began at the end of
the 1980s. With the integration of computer-aided design,
computer-aided manufacturing, numerical control tech-
niques, laser techniques, and material science, surgical
operations can be performed in a more precise and
systematic manner. Recently, although CAS and rapid
prototyping techniques can be used in craniomaxillofacial
surgery, e.g., the rectification of congenital craniofacial
malformations (ocular hypertelorism, craniostenosis, first
and second branchial arch syndrome) and traumatic and
postoperative osseous defection, those techniques still had
limited application in cosmetic surgery. The improvement
of surgical accuracy is the inexorable trend in cosmetic
surgery, especially for those surgical operations associated
with filling materials such as rhinoplasty, chin augmenta-
tion and temporal augmentation. These operations depend
more on a rigorous and individual preoperative design
consistent with aesthetics than on a surgeon’s experience
Fig. 13 Preoperative profile view of case 2
Fig. 14 Postoperative profile view of case 2, six months after ePTFE
implantation
Fig. 15 Preoperative front view of case 3
Fig. 16 Postoperative front view of case 3, six months after Medpor
implantation
Aesth Plast Surg (2010) 34:172–178 177
123
and stereotyped feature. In our clinical practice, the rapid
prototyping technique was used to design individual pros-
thetic filling implants for the mental region. We designed
and prefabricated the mold for the prosthesis preopera-
tively using CAS and rapid prototyping techniques. Then
we carved the filling material following the predesigned
mold or directly used the silicone implant which was made
according to the predesigned mold. It simplified the oper-
ating procedure and shortened the operating time. In our
series, all patients underwent preoperative design accord-
ing to facial and mental aesthetics using computer-aided
three-dimensional reconstruction techniques. After deter-
mination of prosthetic size, shape, and location, we made
the personalized mold with the rapid prototyping tech-
nique. Then we carved and implanted the filling material
using the predesigned mold or directly used the silicone
implant which was made according to the mold. This
procedure was totally different from traditional operative
methods which depended on visual measurement and
experience. It not only shortened the operating time and
improved the accuracy of rectification, but also achieved
the best personal profile matching.
At present, this technique still has its limitations. For
example, implant materials such as Medpor and ePTFE
could not be sintered directly except for unitane, and with
the rapid prototyping technique we have to manufacture the
model for prosthetic material first and then trim the pros-
thetic material in accordance with the prosthetic mold. That
affects the accuracy of the rectification. Besides, the
computer-assisted designation could not picture the chan-
ges of soft tissue following osseous changes [6], i.e., when
designing chin filling, the effect on local soft tissue could
not be pictured. This means that the surgeon could not get
information on the result of the rectification. All these
limitations still need further research. We are sure that in
the future the rapid prototyping technique will be used
increasingly in medicine.
References
1. Guyuron B, Michelow BJ, Willis L (1995) Practical classification
of chin deformities. Aesthet Plast Surg 19:257–264
2. Stambaugh KI (1992) Chin augmentation: an important adjunctive
procedure to rhinoplasty. Arch Otolaryngol Head Neck Surg
118:682–686
3. McCarthy JG (1990) Plastic surgery. WB Saunders, Philladephia,
pp 1350–1332
4. McCarthy JG, Ruff GL, Zide MB (1991) A surgical system for the
correction of bony chin deformity. Clin Plast Surg 18:139–152
5. Li Y, Zhen Y (2007) Application of rapid prototyping in
craniofacial surgery. Chin J Aesth Med 16(9):1309–1311
6. Liu XJ, Gui L, Zhang ZY, Peng X, Liu C (2006) The application of
three-dimensional skull model in the treatment of craniofacial
malformation. Zhonghua Zheng Xing Wai Ke Za Zhi [Chin J Plast
Surg] 22(3):169–171
Fig. 17 Preoperative profile view of case 3
Fig. 18 Postoperative profile view of case 3, six months after
Medpor implantation
178 Aesth Plast Surg (2010) 34:172–178
123
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