Dr. Ahmed M. Adawy Professor Emeritus, Dep. Oral & Maxillofacial Surg. Former Dean, Faculty of Dental Medicine Al-Azhar University. Numerous etiologies lie behind mandibular defects including pathologic lesions, trauma related, infectious diseases and congenital defects. At present, the methods to restore mandibular defects can be classified into four basic categories: 1.Autogenous bone grafts in the form of nonvascularized free bone transfer, or vascularized tissue transfer, either pedicled or based on microvascular anastomosis 2. Distraction osteogenesis 3. Alloplastic materials (with or without bone) 4. Tissue engineered grafts

2. Dr. Ahmed M. Adawy
Professor Emeritus, Dep. Oral & Maxillofacial Surg.
Former Dean, Faculty of Dental Medicine
Al-Azhar University

3. Bone defect is a lack of bone where it should normally
occur. Numerous etiologies lie behind mandibular defects
including pathologic lesions, trauma related, infectious
diseases and congenital defects. Meanwhile, the most
common indication for mandibular reconstruction remains
resection of benign or malignant lesions, posttraumatic
deformities and osteoradionecrosis

4. Etiology of mandibular defects

5. Locally invasive benign tumors such as ameloblastoma,
giant cell granuloma, keratocystic odontogenic tumor, and
odontogenic myxoma are a benign, invasive, lesions of the
jaws that predominantly affects the mandible. Despite the
benign nature of these lesions, there is a high rate of local
recurrence after curettage, which usually requires resection.
Resection leads to segmental defects. Even, when treated
conservatively, curettage results in the so called “critical
size defects”. Critical sized defect has been defined as a
defect which shows less than 10 percent bony regeneration
during the lifetime of the animal (1)

6. Mandibular defects can generally be considered by their
location and extent and can be divided into defects
involving the anterior mandible ( Central defects “C”)
and lateral mandible ( Lateral segment “L” ). When the
condyle is resected together with the lateral mandible, the
defect is designated ‘‘H”. Eight permutations of these
capital letters; C, L, H, LC, HC, LCL, HCL, and HH- are
encountered for mandibular defects (2). The classification
was modified to include a soft tissue description as well,
with ‘‘t’’ representing a significant tongue defect, ‘‘m’’ a
mucosal defect, and ‘‘s’’ an external skin defect (3)

7. Classification of mandibular defects

8. When undertaking mandibular reconstruction, the restoration
of bony continuity alone should not be considered the
measure of success. The functions of chewing, swallowing,
speech articulation, and oral competence must also be
addressed. The goals of mandibular reconstruction are:
1) establishment of mandibular continuity, 2) establishment
of an osseous-alveolar base, 3) correction of soft-tissue
defects, and 4) establishment of mandibular function

9. The first step in undertaking mandibular reconstruction
involves careful evaluation of the patients’ anatomy in order
to define the full extent of the existing or proposed defect.
The quality and quantity of the remaining hard and soft
tissue components must be examined. Advances in
diagnostic technologies can be very helpful when
formulating a plan for mandibular reconstruction. Virtual
surgical planning (VSP) and computer aided design (CAD) /
computer aided modeling (CAM) is an exciting new
technology that presents advantages in complex
craniomaxillofacial reconstruction (4)

10. Diagnostic aids

11. CAD / CAM technology

12. In previous decades, delayed reconstruction of mandibular
defects was favored over primary reconstruction. The
believe was that primary reconstruction could potentially
mask tumor recurrence. Further, the success rates following
primary reconstruction were not very high. The defects
were bridged by reconstruction plates. The most common
complications were plate exposure, loose osteosynthesis
screws and fractures of the reconstruction plate. Low
success rates of plate-only reconstruction have been
reported, ranging from 34% at 6 months, and 13 to 64% at
1-year follow-up (5)

13. Plate exposure

14. Fracture of reconstruction plate

15. At present, the methods to restore mandibular defects can
be classified into four basic categories:
1.Autogenous bone grafts in the form of nonvascularized
free bone transfer, or vascularized tissue transfer, either
pedicled or based on microvascular anastomosis
2. Distraction osteogenesis
3. Alloplastic materials (with or without bone)
4. Tissue engineered grafts
The proper selection of the graft materials and technique is
based on the size, site, shape, and dimensions of the defect

16. Bone grafts are often described by the terms osteogenicity,
osteoinductivity and osteoconductivity. Osteogenicity is
the presence of bone forming cells within the bone graft.
Osteoinductivity is the ability of a graft to stimulate or
promote bone formation. Osteoconductivity is the ability
of the graft to function as a scaffold for ingrowth of new
bone and migration of local osteocompetent cells originate
from the endostium or residual periostium of the host bone

17. Nonvascularized autologous bone grafts can be used for
reconstruction of small to medium size L- defects of the
mandible. Many donor sites are available for autologous
bone graft harvest such as calvarium, rib, ilium, tibia,
fibula, scapula, humerus, radius, metatarsus, and
mandibular symphysis, and provide viable and
immunocompatible osteoblastic cells. These sites are
different in terms of embryologic characteristics, type of
bone and architecture. This could be the potential source
of advantages and disadvantages (6)

18. Cranial bone is an acceptable site for obtaining bone for
grafting. The technique can yield considerable amounts of
cortical bone but limited amounts of cancellous bone.
Obtaining grafts from the ribs is another option that yield
both bony and cartilaginous tissues. The cartilaginous
component is useful for providing an articular surface for
the temporomandibular joint and as a growth center in
growing patients. However, rib graft is limited by the size,
curvature, and strength of the rib plus donor site
complications, such as pneumothorax, rib fracture, and
pleural puncture

19. Harvesting calvarium bone graft

20. Costochondoral rib graft for ramus
and condyle reconstruction

21. Many surgeons choose a cortico-cancellous block graft
taken from the anterior or posterior iliac crest for jaw
reconstruction. These grafts contain the greatest absolute
cancellous bone volume and have the highest cancellous-
to-cortical bone ratio. From a single side, the maximum
amount of obtainable bone from the anterior ilium
approaches 50 cc. From the posterior ilium, the maximum
obtainable bone volume is about 90 cc. Donor site
complications include hematoma, seroma, nerve and
arterial injuries, gait disturbances, fractures of the iliac
wing, peritoneal perforation, infection, sacroiliac
instability, and pain (7)

22. Bone graft harvested from the anterior
part of the iliac crest

23. However, there are two major limitation of using
an autogenous bone graft: poor osteointegration and
excessive resorption when the defect is larger than 6 to 9
cm. Insufficient blood supply for the surrounding tissues
secondary to irradiation, scarring, and infection is major
detrimental factor. Moreover, donor site morbidity limits
the use of autogenous bone graft (8)

24. The use of vascularized bone grafts has considerably
improved treatment outcomes for patients with significant
mandibular and soft tissue defects, particularly after
ongoing radiation therapy. Direct comparisons of
nonvasculized bone grafts and vascularized bone grafts
have shown superiority of the latter in terms of bony union
(69% vs. 96% ) (9), as well as superior functional and
aesthetic scores for diet, speech, and midline symmetry
(10). Superiority increases significantly in case of
mandibular defects greater than 6 cm. Today the most
commonly used grafts with microvascular anastomosis
are: fibula; iliac crest; scapula; and radial forearm with the
fibula graft being the most popular for mandibular
reconstruction

25. The use of free vascularized fibula has become the “gold
standard” for mandibular reconstruction since its
introduction in 1989 (11). The fibula graft offers a good
length of dense cortical bone, up to 25 cm in adults, as
well as a long pedicle based on the peroneal artery for the
reconstruction of long bony defects. Further, the graft may
provide skin islands, up to 25 cm long and 14 cm wide,
suitable for reconstruction of associated soft tissue defects.
Moreover, the technique permits two team approach. This
decreases the time of operation, and reduces the critical
ischemia time (5 hours) of the graft. A 98% graft survival
and good aesthetic and functional outcomes have been
reported (12). Morbidity is mostly avoidable with careful
planning and appropriate technique

26. One disadvantage of the free fibula graft is the height
discrepancy between the native mandible and the
transplanted fibula, especially at the anterior segment. The
‘double-barreling’ of the fibula to create equal struts is a
useful modification with good aesthetic and functional
outcomes (12). The ‘double-barreling’ of the fibula
enables immediate osseointegrated dental implantation,
obtaining better results and lower complication rates
compared to vertical distraction devices (13)

27. Diagrammatic representation of
harvesting vascularized fibula
graft

28. Double-barreling fibula graft

29. Distraction osteogenesis is a biologic process of new bone
formation in a gap between two separated bone segments.
The gap is gradually filled by incremental traction. A
callus forms between the separated bone segments as long
as the traction proceeds. There have been a number of
small series describing success with transport-disk
distraction osteogenesis. One study described a two-step
transport-disk distraction technique with internal
distracters to reconstruct body or ramus defects in both
horizontal and vertical dimensions (14). All patients had
benign odontogenic tumors, which allowed preservation of
periosteum and no required radiation. Also, the distraction
requires 14–18 months of treatment

30. Another study reported a series of seven patients with
segmental defects after composite resections for oral
cavity squamous cell carcinoma (15). The initial
reconstruction used soft tissue flaps and reconstructive
bridging plates. At an average 20 months later, transport
disk distraction osteogenesis was performed with an
external fixator. One patient received radiotherapy and had
insufficient callus formation. The other six patients had
successful bony reconstruction.
Although distraction osteogenesis has been successful in
the reconstruction of large segmental defects, its
application is limited by a requirement for intact soft
tissue and periosteum, an incompatibility with adjuvant
radiotherapy and the need for a long period of treatment

31. Transport-disk distraction osteogenesis

32. Panoramic X-ray after installation of the distraction device
One year after distraction osteogenesis,
very good bone formation is noted

33. Currently , there has been great interest in the
development of synthetic grafting materials to be used in
osseous reconstruction surgeries (16).The ideal bone
substitute is osteoconductive, osteoinductive,
biocompatible, and bioresorbable. Moreover, it should
induce minimal or no fibrotic reaction, undergo
remodeling and support new bone formation. From a
mechanical point of view bone substitutes should have
similar strengths to that of the bone being replaced.
Finally, it should be cost-effective and be available in the
amount required

34. Multiple products, containing combinations of
hydroxyapatite, tricalcium phosphate, dicalcium
phosphate, calcium sulphate, or bioactive glass are
currently available for use in trauma and orthopedic
surgery. The crystalline and porous qualities of these
materials aid in anchoring surrounding tissues to facilitate
proper fixation. However, an evidence-based guideline to
assist surgeons in selecting the best product for specific
clinical indications is not available yet

35. Tissue engineering is the application of scientific
principles to the design, fabrication, modification and
growth of living tissues using biomaterials, cells and
growth factors (17). There are many approaches to bone
tissue engineering. One popular approach involves the
utilization of biomaterial scaffolds combined with bone
marrow-derived stromal cells and growth factors.
Numerous scaffolds matrices, including allogenic,
xenogenic, and synthetic graft materials have been used

36. Tissue engineering technology

37. Ideally, the scaffolds should be (1) three dimensional and
highly porous with an interconnected pore network for cell
growth and flow transport of nutrients and metabolic
waste as well as (2) biocompatible and bioresorbable with
a controllable degradation and resorption rate to match cell
or tissue growth. Furthermore, these scaffolds should
possess (3) suitable surface chemistry for cell attachment,
proliferation, and differentiation, and (4) mechanical
properties to match those of the tissues at the site of
implantation (18)

38. Bone marrow derived stromal cells can be grouped under
the term mesenchymal stem cells. They are characterized
by their ability to self renew and differentiate into multiple
cell types, including osteoblasts, adipocytes and
chondrocytes. It has been widely accepted that regeneration
of bone defects is advanced by bone marrow stem cells that
migrate to the site of damage and undergo differentiation
promoting structural and functional repair (19). Bone
marrow stromal cells are induced to differentiate into
osteoblasts and restore bone defects

39. Mesenchymal stem cells have the potential
to differentiate into various lineages

40. Many growth factors are involved in osteogenesis. Bone
morphogenetic proteins (BMP-2 and BMP-7),
transforming growth factor beta (TGF-β), insulin-like
growth factors I and II (IGF I and II), platelet-derived
growth factor (PDGF), fibroblast growth factors (FGFs),
and vascular endothelial growth factor (VEGF) have been
proposed for use in bone tissue engineering. Bone
morphogenetic proteins; BMP-2 and BMP-7 are known
for their osteoinductive qualities (20)

41. In an interesting study, Herford and Boyne (21) presented
the practice of reconstruction of large defects of the
mandible using rhBMP-2 on collagen carrier and titanium
mesh in 14 patients. All cases achieved complete bone
formation and high levels of functional rehabilitation.
Radiologic indications of a newly formed bone appeared
in 5-6 months after the reconstruction.
Tissue bioengineering technology appears to be a very
promising technique. It could have significant impact on
the reconstruction of maxillofacial defects. However, more
comparative studies and randomized controlled clinical
trials are needed to determine the true efficacy of this
technique

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