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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_980_Библиотеки_им_академика_М_И_Перельмана
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Functional Bone Replacement in Oral and Maxillofacial Surgery: Denition…
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titanium prosthesis problems in the glenoid fossa. Nonetheless, these reports did
not determine the biomechanical characteristics of the patient-specic implants
before surgery. Khojasteh etal. have reported another approach for using patientspecic titanium prosthesis for the reconstruction of bilateral RCU defects preserving both the autogenous condylar segments [13]. Before fabrication of the
prosthesis, they conrmed biomechanical characteristics of their novel prosthesis
using the nite element analysis.
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4 Total Mandibular Reconstruction
Reconstruction of total mandibular defect is a much more challenging issue, and
publications in this eld are extremely limited and have reported only individual
clinical cases [37, 38]. Functional replacement of total jaw defects is intensely difcult from anatomical, topographic, and technical viewpoint. It should be noted that
creating clear guidelines for total mandibular reconstruction is extremely tough due
to the small number of well-documented patients.
A new concept of total mandibular defects treatment with an original design of
the solid titanium endoprosthesis manufacturing was offered by Xilloc Co., together
with Layer Wise, in 2009 [7]. Poukens successfully reconstructed the mandibular
defect of a patient, removed due to bisphosphonate-related osteonecrosis of the jaw
(BRONJ), by the developed design. Then, Professor Jules Poukens and Xilloc CEO
Maikel Beerens in 2011 have reported the successful complete mandibular replacement in an 83-year-old patient following the removal of the mandible due to progressive osteomyelitis [7]. This approach has been introduced as an alternative to
autogenous free bone grafting in complex cases and has the maximum conformity
to the anatomical shape and size of the mandible. However, there has been no data
in the literature on the effectiveness and risks of the technique with long-term
follow-up.
In a recent case report, Chernohorskyi etal. demonstrated a functional replacement of total mandible by a patient-specic implant, immediately after total mandibulectomy due to the history of prolonged diffuse infection and osteonecrosis of
the jaw [7]. Only a foreign body sensation and some limited mouth opening was
observed in the early postoperative time with no other complications, and good
aesthetic outcomes were obtained. They indicated that two factors were important:
weight reduction of the implant with preservation of the strength and soft tissue
integration of the prosthesis.
5 Delayed Functional Bone Replacement
In pathologic lesions especially those with high recurrence rate or malignancies,
simultaneous reconstruction after primary tumor resection may not be rational. In
fact, the main problem is the need for a second revisional surgery, which lessens the
effectiveness of the one-stage reconstructive surgery [39, 40]. A few clinical studies,
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F. Bastami and A. Khojasteh
case reports, and experimental studies support the one-stage reconstruction using
porous titanium implants after tumor resection of the mandible [41]. Indeed, the
resection of tumor with safe margin may not be reliably investigated at the operation
time, and the necessity to do a second resection is mandatory [42]; hence, using a
permanent prosthesis would be perilous and can jeopardize the possibility of a second surgery.
In these situations, one of the treatment options is the use of a temporary prosthesis after tumor resection. Then, a permanent customized titanium prosthesis
can replace the temporary prosthesis after conrming the absence of tumor in the
surgical margin. Several clinical and experimental studies demonstrated the possibility of the bio-integration of a secondary implant. It is conrmed that surface
texture has signicant effects on bone apposition around the titanium implants
[43]. In addition, titanium implants showed reintegration with native bone even in
the condition of articial peri-implantitis in experimental studies [44, 45].
Dolgolev etal. in 2020, used customized plastic prosthesis after tumor resection
in an ewes model, and later on, replaced it by a patient-specic porous titanium
prosthesis in a second surgery [46]. They demonstrated signicant osseointegration of the titanium prosthesis and recommended using this technique to postpone
the use of permanent prosthesis to gain better therapeutic results and consider the
possible complications of tumor resection. However, using titanium prosthesis in
the second surgery has remained a controversial issue in clinical settings [47].
6 Case Presentation
A 49-year-old patient presented with the chief complaint of bilateral mandibular
pathologic lesion, diagnosed central giant cell granuloma (CGCG), an aggressive
benign tumor, according to the pathologic report of the incisional biopsy. He had no
considerable nding in his medical history.
Panoramic imaging demonstrated bilateral mandible had been involved from the
distal area of the second molars and the ascending ramus to the condylar region and
coronoid process even though the condyles were intact (Fig.1).
Fig. 1 Panoramic imaging
of the patient’s jaws [13]
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6.1 Prosthesis Design andManufacturing
A series of slices from the patient’s anatomy (642 images, 0.625 thickness, slice
increment= 0.300mm) was provided, and the DIOCM data was translated into
axial, coronal, and sagittal planes (Fig.2). For accurate surgical resection of the
tumor, four guiding plans were necessary, regarding which bilateral condyles were
remained intact. Because the pathologic lesion had changed the normal shape of the
mandible, two important factors should be considered for prosthesis design: (1)
restoring the normal mandibular shape and (2) providing adequate durability and
stability for the bilateral condyles and remaining mandibular bone (Fig.3). For better xation of the prosthesis to the remaining anterior part of the mandible, several
holes were designed with a diameter of 2mm in the superior part and 2.7mm in the
inferior part. The ramus prosthesis was xed to the remaining condyle using miniplates with three holes (diameter of 2mm). We used solid titanium like the natural
inferior border of mandible to reinforce the inferior part of the prosthesis.
Macroporosity was created in the other parts (pore size of 3mm) to decrease the
weight of prosthesis.
Finite element study validated the prosthesis design to examine stability of the
prosthesis and stress shielding in bones adjacent the prosthesis (Fig.4). No stress
shielding was in the condyles, the remaining mandible, and the novel prosthesis
(Fig.5). The maximum stress on the cortical and spongy bones of the left condyle
was 19.46 and 1.13MPa and the right condyle was 17.07 and 1.29MPa, respectively. The preserved condyles undergone less yield stress than the native mandibular bone (108 and 3MPa for cortical and spongy bone, respectively). The
highest stress on the cortical and spongy bones of the remaining mandible was
a
c
Fig. 2 (a) Coronal, (b) axial, and (c) sagittal views and (d) 3D reconstruction of the patient’s
mandible from CT scan in which the CGCG involvement is shown in the red part [13]
b
d
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F. Bastami and A. Khojasteh
ab c
de
Fig. 3 (a) The original model of the patient’s mandible extracted from CT images. Tumor areas
have been determined. (b) Cutting guides for cutting tumor areas, marked in red, from the mandible (green, left guide, and blue, right guide). The arrows demonstrate the cutting edges. (c) The
primary design of the prosthesis includes registration of a normal mandible model onto the
patient’s defectious mandible. (d) The secondary design of the prosthesis includes an offset in the
inferior margin of the remaining mandible and removing the extra parts from primary design. (e)
In the nal design, the prosthesis near the mandibular body was created as porous structure for
decreasing the weight and using bone graft into this part [13]
51.00 and 2.81MPa, respectively, less than the native mandibular bone. In addition, the greatest stress on the left and right prostheses were 65.80 and 45.67MPa,
respectively, less than the yield stress of titanium (790MPa). The pores showed a
stress distribution model, according to which they did not affect the prosthesis
strength.
We fabricated the Ti6Al4V prosthesis via SLM technique with a wavelength
range of 1070nm. Briey, Ti6Al4V-ELI powder with a particle size of 20–63μm
(grade 23) from SLM Solution Group (AG, Lubeck, Germany) underwent SLM
processing, with a scan velocity of 650mm/s and a laser thickness of 30μm in an
inert atmosphere with oxygen concentrations below 50ppm. Heat treatment was
performed on the implants at 810°C (10°C/min) for 4h in a furnace under argon
shield and then was gradually cooled down to room temperature. Then, the implant
underwent a sandblasting process to reach the mean nal roughness of Ra=2.2μm.
Finally, the prosthesis became sterile using an autoclave under 121° C and 15psi
for at least 30min. In addition, we manufacture cutting guides by fused deposition
modeling (FDM) technique from poly lactic acid (PLA).
Functional Bone Replacement in Oral and Maxillofacial Surgery: Denition…
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ac
b
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Fig. 4 (a) Assembled prosthesis 3D model on the remaining mandibular bone, condyles, and
teeth. (b) Mechanical properties of bone model with various colors. (c) Boundary condition and
loadings [13]
6.2 Treatment Procedure
The patient underwent surgical procedures by general anesthesia (Fig.6). Bilateral
5cm submandibular incisions were made through the skin and platysma. Dissection
plane was subplatysmal, and submandibular gland capsule, facial vessels, and the
marginal mandibular branch of the facial nerve were identied and preserved.
Dividing the pterygomasseteric sling and complete subperiosteal dissection of the
mandibular body and ramus exposed the tumor totally. The guiding plane helped the
tumor resection. Osteotomy from the ramus preserved the bilateral condyles, and
the articular discs and their superior spaces were intact. Then, the condyles and the
remaining mandibular body were xed to the prostheses.
Buccal fat pad-derived stem cells (BFSCs) were isolated from the harvested
bilateral buccal fat pad (BFP) [48], seeded on a natural bovine bone mineral
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Fig. 5 (a) Von Mises stress contour on the whole model. (b) Von Mises stress contours on both
condyles. (c) Von Mises stress contour on the remaining mandibular bone. (d) Von Mises stress on
the prosthesis. (e and f) clinical view of the surgical site after implantation of prothesis [13]
Functional Bone Replacement in Oral and Maxillofacial Surgery: Denition…
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a
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b
Fig. 6 (a) The guiding plan is matched to the mandibular bone before resection, (b) the resected
mandibular bone and the guiding plan, (c) posterior and (d) anterior view of the condyle xed to
the prosthesis, (e) the prosthesis xed to the mandibular body, and (f) the space into the prosthesis
lled with natural bovine bone mineral in combination with BFSCs [13]
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F. Bastami and A. Khojasteh
c
d
e
Fig. 6 (continued)
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f
Fig. 6 (continued)
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(Cerabone, Botiss, Germany) [49], and transferred into the pores of the prosthesis
[50]. A Hemovac drain was applied, and the wound was closed in three layers. For
8weeks, the patient had a soft diet and placed training elastics on the anterior part
of the jaws just at nights. The patient started active physical therapy 5–7days after
surgery, followed by a passive physical therapy 4weeks postoperatively.
The follow-ups of the patient were weekly during the rst postoperative month,
then twice a month during the next 2months, and then monthly for 6months postoperatively. CT scan showed favorable outcomes of prosthesis insertion after
6months (Fig.7a). The patient expressed signicant improvement in chewing and
speech and pain relief after 6months compared to the baseline. Radiologic images
obtained from preserved condyles showed no sign of osteolysis, dislocation, or
other complications after 18months (Fig.7b). Also, some opacication was found
into the porous parts of the prosthesis, which may indicate new bone formation.
Both functional and esthetic needs of the patient have desirably improved after a
30-month follow-up, with a maximum mouth opening of more than 30mm, and no
deviation during opening and closure of the mouth. Moreover, no screw loosening
or history of jaw dislocation was indicated.
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a
b
Fig. 7 (a) 3D reconstruction of CT scan performed 6months after surgery. (b) Radiography of
condyles from the lateral and posteroanterior sides [13]
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