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1. BONE GRAFT
INDIAN DENTAL ACADEMY
Leader in continuing dental education
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2. CONTENTS
-Introduction
- History
- Definition
- Types of Bone Graft
- Forms of Bone Graft
- Autografts
- Allografts
- Synthetic Bone Grafts
-Sinus Bone Graft
- Bone Graft Handling
- Goals of Reconstruction
- Summary and Conclusion
- References
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3. INTRODUCTION
Bone grafting is a dynamic phenomenon. A successful bone
graft is applied, heals, becomes incorporated, revascularizes and
eventually assumes the form desired. In their early application,
bone grafts were considered a mere strap lattice, and the results
were measured primarily by the graft’s ability to withstand the
mechanical stresses that surrounded them. Today, bone grafts are
viewed as biologic structures. Of course, mechanical stress, shear
stress (extrinsic and intrinsic), contouring, and remodeling are also
important in the long term and are the part of the healing process of
a bone graft.
Different forms of bone grafts vary on the basis of the
function that they must perform.
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4. Grafts that must withstand the shear pressure of mechanical
stress is usually a large cortical bone graft. A bone graft intended for
contouring, to expand the biologic boundaries of the skeleton, and to
change the three dimensional configuration of the face is usually of
the corticocancellous variety; these are soft bone grafts that can be
contoured and allowed to heal, vascularize, and augment existing
bone to produce the desired shape. Corticocancellous bone grafts are
applied to fill a discontinuity defect and require a carrier. There are
many carriers used for such applications.
Almost all bone grafts used currently by thousand of surgeons
around the globe are autogenous. Such autogenous bone grafts
constitute the best biologic bone grafting system for the human
body. They vascularize bone grafts, they heal; and they withstand
mechanical stresses in due time. The more compact the bone graft is,
the less the chance of complete and rapid vascularization. The less
compact the bone graft is, the more rapid the revascularization and
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healing.
5. Whatever specialized group of surgeons uses bone grafting,
whether on the face, the mandible, or the extremities, the principles
are the same. The techniques and indications differ, but the contra
indications may be the same (e.g. bone grafts cannot be applied in
areas that are heavily bacterially contaminated). Topical application
of antibiotics is gaining momentum, particularly the use of antibiotics
in small pellet form to obtain the maximal effect with the least
disadvantage.
We cannot really finish the introductory remarks without
noting two recent advances. The first is the use of vascularized bone
grafts, which have their own vasculature. These can be implanted
with microsurgical technique and allowed to heal appropriately. In
certain parts of the body, it may still be advantageous to allow a bone
graft to vascularize (e.g., in areas where mechanical stress and shear
stress are needed to ensure normal function).
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6. The second aspect is the use and understanding of allografts.
Allografts are becoming a more accepted form of bone grafts. The
majority of large allografts assume a near normal function in individual
who lack certain areas of the body that have been resected for
oncologic problems or for other reasons. It is frequently possible for
these areas to be replaced, and the patient can resume normal function.
However, these large bone grafts do not really completely vascularize
as allografts.
Finally, bone grafts could not have become extensively
popular, easy to implant, and widely utilized around the globe, without
the use of rigid fixation systems. The rigid fixation systems brought a
necessity for understanding biomaterials and metallurgy. Whether the
metal used is stainless steel, titanium, or vitallium, these systems
provide mechanical strength that is 200 times that of a natural bone.
These systems are gettingwww.indiandentalacademy.com
smaller and smaller, to the extent that a
system introduced in 1990 utilized screws measuring 0.8 mm.
7. Prospects for the future include the possibility that when
certain parts are needed, they can be fabricated within the same
biologic system as an autogenous bone graft and then reapplied,
particularly in discontinuity defects. This may benefit the patient
with skeletal problems undergoing oncologic treatment or the patient
with postoncologic deformities, as well as patients with post
traumatic defects.
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8. HISTORY OF AUTOGENOUS BONE
GRAFTING
In 1682 VanMeekren transplanted canine skull bone to
calvarial defect.
Von Walter 1882 described use of corticocancellous bone
graft.
Ollier 1867 reported transfer of periosteum and bone and
concluded that both must be alive to account for osteogenesis.
Barth in 1893 he revealed that several days after bone graft
transfer, the graft is dead. He felt that the graft worked via gradual
resorption and replacement of dead bone by creeping substitution of
dead graft by viable bone growing into it from living bone in contact
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with it. This is currently called as Osteoconduction.
9. Axhausen in 1907 demonstrated in an experiment that
periosteally covered bone grafts exhibited osteogenesis from surface
cells surviving at the periosteum.
Phemister in 1914 concluded after a series of studies that some
osteogenic cells on surface of bone graft survive by diffusion of
oxygen and nutrients from the recipient bed.
It was later done by Ham and Gorden in 1952 and Hancock
1963.
Gallie & Robertson 1918, agreed that survival of cells on bone
graft is important, and that rate of survival was better with cancellous
bone than with cortical.
Mowlem in 1944 and later in 1963, used cancellous bone
grafts and demonstrated its superiority over cortical bone grafts.
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10. Okland and associates in 1985 put forward that survival of
surface cells in autogenous bone grafts is much more superior to
freeze dried autogenous grafts, allografts, inorganic bone and its
substitutes.
ALLOGENIC BONE GRAFTING
History:
Bone induction principle was described by Urist for allogenic
bone in 1953. This induction was mediated through an acid-insolube
protein complex (BMP) derived from the grafted bone that directs
differentiation and activity of host osteocompetent cells towards bone
formation. Urist and Burwell in 1968 and later in 1969 that early use
of allogenic bone either fresh or frozen and dried.
Urist in 1968 also described that allogenic bone is replaced by
new host bone.
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11. Definition
A graft is a substance, foreign to the region of the body in
which it is placed, which is used to replace, augment or fill a defect
created by surgery, trauma, disease and developmental deficiency.
Graft is a living tissue, transplanted to a different site, that
continues to live and function in the new environment. If the tissues
does not survive the relocation, it is technically an implant rather than
a graft.
Graft (according to GPT) : Tissue or material used to repair a
defect or deficiency.
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12. Indication for Bone Grafting
Jaw resection following malignancy / other pathology
Extensive trauma
In orthognathic surgery
As an onlay material in facial aesthetic surgery
As a composite cartilage – bone graft in the reconstruction of
the TMJ (growth center)
Large bony defects created by cysts and tumors
In preprosthetic surgery as an onlay
In preprosthetic surgery as a fill in material
In cleft patients.
In implantology e.g. : sinus lift procedure
In periodontal surgery
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13. Radiographic Assessment
Presurgically
-
Radiographs to assess the bone density at recipient and
doner site.
-
Radiographs to rule out aberrant anatomy and gross
pathology.
-
Arteriograms for free grafts
Post surgically
-
Increased or normal radio density at the grafted site.
-
Irregular margins coinciding with osteoclastic activity
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14. -
At the end of healing phase : No radio density
-
Scintography exhibits hot spots in areas of increased bone
activity – bone deposition.
-
C.T. Scans show good resolution and clarity
-
In M.R.I., shows up as high intensity images in both T1
and T2 scans.
-
M.R.I. can detect marrow activity and is helpful in
predicting initial changes.
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15. TYPES OF BONE GRAFTS
Auto graft : Bone graft transplanted from one site to
another from patients own body.
Xenograft / Heterograft : Bone taken from another
species. These can be both cancellous or cortical
Composite : Bone grafts are made partly allograft or
heterograft and partly autograft.
Allograft : Bone transplanted from one individual to
another genetically unrelated individual of same species.
Isograft : Bone graft transplanted from one person to
another genetically related individual of same species.
The donors are designated as Autologous, Heterologous,
Allologous, Isologous with respect to the recipient.
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16. FORMS OF BONE GRAFT
1.
Non-vascularised
2.
Vascularised
3.
Cancellous
4.
Cortical
5.
Corticocancellous, has properties of both types
Other types of grafts such as slurry bone, particulate bone,
bone pastes are small fragments of bones of different sizes
compacted together. The easier the penetration of blood vessel into
the graft to revascularise it, the less mechanical stress that graft can
take. More solid the bone graft is in its form to withstand
mechanical stress with appropriate stress shielding, the harder it is to
revascularise, incorporate and be viable bone.
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17. CORTICAL BONE
Cortical bone can produce good mechanical filling of defect, and give
good functional result, although it takes longer time to revascularise .
Cancellous bone also fills defect but its healing is faster.
They have some clinical limitation. They are used primarily in areas
of great mechanical stress,and hence its proper fixation is important for
the stability of graft and for its proper function. It allows the graft to
survive with or without complete viability. This form of graft is useful
in long bones, not very effective when used in facial skeleton
membranous bone site. It used for discontinuity repair, to improve
existing contours, expand on the boundary to give patient a normal
aesthetic look.
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18. CANCELLOUS BONE
This is used to get fusion and for correcting discontinuity
defects. They can be utilized in any type of wounds i.e., contaminated
or clean. These usually do not have mechanical strength desired for
reconstruction of larger defects. Because of large open areas in the
grafts, revascularisation takes place very well. Thus new cellular
regeneration, remodeling and substitution, of new bone occurs, as old
bone is removed.
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19. CORTICAL
CANCELLOUS
Cortical bone grafts
revascularise slowly. They are
not permeated by the blood
vessels until 6-7days and graft is
not completely vascular till 12months. This delay may be due
to the need to open, by the
osteoclastic activity, the existing
Volkmanns
canals
and
Haversian system. It may also
be due to smaller no of endosteal
cells available for the end to end
anestamosis.
There is end to end
anestomosis of host with grafted
vessels. This together with the
process of in-growth into the
marrow spaces takes place with
in
2
weeks.
This
revascularization also allows the
grafted cells and host cells,
induced by osteogenic cells, to
differentiate into osteoblasts.
They surround isolate dead bone
and account for increased
radiodensity of graft initially.
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20. The process of repair is
initiated by osteoclastic activity.
Here osteoclastic activity ceases
following the completion of the
task of walling off the remaining
necrotic bone. This mixture of
new necrotic bone remains until
the metabolic and the catabolic
phases of repair are complete.
Here we have viable and non
viable bone
In
time
decreased
radiodensity is seen, as a result
of removal of necrotic bone.
Also increased radio density is
due to increased no. of surviving
transplanted cells.
The no. of
viable cells are more also because
of ability of more cells to be
nourished by diffusion from
surrounding host. The process of
repair is initiated by osteoblastic
activity.
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21. This
bone
graft
decreases in mass and in
porosity, thus it is weakened
by 50% from 6 weeks to 6
months to 2 years following
grafting, the mechanical
strength is equal to normal
bone.
Here only new bone remains
and the necrotic bone is removed.
Here we have only viable bone.
Although in cancellous bone the
augmentation of new bone and its
homogenecity result in initial increase
in strength, in time mechanical
strength return to normal due to
osteoclastic activity and decreased
osteoblastic activity
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22. Bone Graft
Cancellous
Cortical
Cortico – Cancellous
Autograft
Allograft
Xenograft
Source
HIP, RIB, TIBIA
Cranium
Clinical application
varied
Clinical outcome
Accepted (special)
Not useful
Satisfactory
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Standard Procedure
23. The bone used for grafts should have a structure and form so
that when it is placed in the recipient bed, it will proceed through
the natural process of healing.
Cortical bone contains pure cortex dense bone. It is usually
layered and the only open space for revascularisation is that of
nutrient blood vessels.Hence it is used for weight bearing areas.
Cancellous bone provides more open spaces for faster
revascularisation, but it lacks mechanical strength, particularly
when used for weight bearing areas. However corticocancellous
provides the advantage of both.
Bone grafts can be developed into blocks, chips, and paste.
Block of bone developed is used such that the defect is outlined on
the donor site, donor bone cut to the specification needed and graft
corresponds exactly to size and shape of the defect.
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24. Bone chips are harvested as particulate bone. There is no
structure to such grafts. The defect must be well stented and
healing takes place as the pieces of bone become incorporated.
Rapid vascularization of grafted tissue is then ended by
solidification, then only can it withstand weight and forces. Only
disadvantage is that it takes about one year for its completion. Bone
paste is used as a carrier to bridge the defect to be closed. Thus
bone paste if made slurry can be packed in the defect.
. Some authors say addition of microfibrillar collagen
(avitene) gives form to paste, thus making it more easy to handle.
This also takes about, at least one year to become solid to withstand
mechanical forces. It should have sufficient rigidity to withstand
mechanical pressure during healing phase.
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26. I Autograft
The most preferred bone graft, sites mainly being rib,
iliac crest as the primary source. This refers to bone tissue
transferred from one site to another in same individual.
Clinically these grafts can be further classified on the basis of
SITE OF ORIGIN
Iliac
Fibula
Rib
GROSS ANATOMY
Cortical
Cancellous
Corticocancellous www.indiandentalacademy.com
28. 1. Block Bone Grafts Devoid of Periosteium
The piece of bone contain both cortical and cancellous bone. It
is shaped to fit a defect either before or after the bone has been
removed from the donor site subperiostially. This type of graft is
useful for
a.
Repairing a saddle nose.
b.
Restoring continuity of the mandible
c.
Filling skull defects
d.
Restoring the zygomatic prominence.
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30. 2. Osteoperiosteal Grafts
These bone grafts have the periosteum attached. They are
obtained from the flat medial surface of the tibia and from the iliac
bone.
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31. 3. Cancellous Bone Grafts
The best source for these type of grafts is the ilium.
These grafts are useful for
a.
Filling in surface bone defects
b.
Interposing between separated bony fragments
c.
Filling gaps beneath and between larger bone grafts
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32. The chips are usually packed at the junction between larger
bone graft and the host bone. The advantages of chip cancellous
bone grafts include
a.
They seem to be more resistant to infection
b.
Regeneration occurs more rapidly than with other grafts
4. The Split – Rib Graft
This type of graft has been recommended by Hongacre and
Destefano (1975) for large cranial and facial defects in children as
regeneration of bone occurs in the donor site.
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33. 5. Fibular
The free vascularised fibular graft was the first free graft
used clinically. The advantage of it in long bone defects are
strength, length and growth plate. As it is purely cortical it can
withstand daily stresses. The disadvantages of this graft are that
vascular pedicle is as short as 1 cm. This means that there must be
appropriate vasculature close to the recipient site. It is used
basically for long bone defects.
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34. In 1973, Taylor described its use as a reconstructive method. It is
used for reconstruction of mandibular deformities, craniofacial defect,
long bone defects etc. The advantage is its curvature, thickness of
vascular pedical length upto 8 cm. This can be raised as a composite
flap, myoosseous and osseocutaneous flap. Disadvantage: damage by
perforating the peritoneal cavity. The anatomy is such that either
superficial or deep circumflex iliac artery can be used as vascular
supply for flap closure.
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35. II Allografts
This is the principle alternative to autogenous bone.
Allograft or alloimplant refers to bone which is harvested
from one individual and transplanted into another within same
species.
These bone tissue implants provide the form and matrix of
bone tissue, but no viable bone cells are transplanted. Some of
articular chondrocytes may remain viable if handled carefully.
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36. 1 Freeze dried bone allograft FDBA
This is not a synthetic bone,but it is a human bone,harvested
from fresh cadavers it is then sterilised,freezed and dried .It works
primarily through conduction, thus over a period,it will resorb and bone
graft is replaced.These are commonly used in sinus bone grafting
procedures.
Barrier membrane (Gortex)
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37. This is probably the most frequently used alloimplant. It is
used mainly as a composite graft (i.e., in combination with marrow
from the recipient). In orthopaedic surgery, it is used to fill
defects resulting from the extirpation of bone tumors or cysts or as
an adjunct in spinal fusions. It is also used extensively by
periodontists to fill alveolar defects and by oral surgeons for
reconstruction in the maxillofacial region. However, lyophilized
bone has been shown to retain its antigenicity, and in applications
where larger segments of bone are required with ability to withstand
stress, the results have been very unfavorable, showing incomplete
incorporation and decreased ability to withstand torsional stress.
Longitudinal cracks have also been observed when freeze-dried
bone is rehydrated. It is suggested that freeze-dried bone be
supplemented with generous amounts of autogenous iliac bone
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38. 2 Demineralised bone matrix
It is a subset of alloimplant bone, which can be used as an
implant material. Preparation and dimineralisation of bone further
reduces antigenicity and makes bioactive proteins in bone matrix more
available for interaction with local cells. This demineralised bone matrix
has been used to induce bone formation and produce healing. It was
shown by Glowacki and coworkers that some of its use is in craniofacial
reconstruction; although its use is mostly in orthopedic procedure.
In contrast to deproteinized bone, demineralized bone retains its
osteoinductive properties and has been used by Mulliken et al for
reconstruction in the craniofacial region. It is acknowledged, however,
that the use of radiation for sterilization diminishes osteoinductivity, and
other ways to sterilize the implant are being investigated
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40. Deproteinized Bone
Such bone preparations lack osteoinductivity. Despite one
report in which good results are claimed, experimental results
indicate the failure to incorporate deproteinized bone into the host
skeleton.
Chemosterilized
(AAA) Bone
Autolysed,
Antigen-Extracted
Allogeneic
This particular alloimplant has been described and is being
used by Urist and Dawson. Cadaver bone is harvested as soon as
possible, after death, and processed so that the BMP is preserved
while nearly all the stainable intralacunar material is enzymatically
digested. It is then freeze-dried. The breaking strength is claimed
to be about one half that of whole, undemineralized wet bone. The
highest success rates come from operations on young children with
a high proliferative bone growing capacity.
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41. III Xenografts
As noted earlier, the use of xenogeneic transplants has been
abandoned by most surgeons, although sporadic reports of their
use continues. The genetic transplantation differences between
human tissue and that of other species (e.g., bovine), are such that
the fate of such grafts is their eventual sequestration without any
new bone formation.
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42. IV Synthetic bone grafts
Alloplast
These are expanding variety of synthetic or non tissue
bone graft. These includes biologic and synthetic polymers;
ceramics, matrix proteins and metals. Combinations of some of
these materials may replace autograft and allograft bone
materials.
The various alloplasts used for reconstruction or augmentation in the
craniofacial maxillary region include.
1.
Solid or mesh metals such as titanium and its alloys, 316 L
stainless steel, and Cr. Co-Mb alloys.
2.
Solid or porous polymicrons such as silicone rubber, proplast.
3.
Hydroxylapatite
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43. Selection of an alloplastic material for reconstruction involves
two considerations.
1. Physical properties dictate how such materials may be adapted to the
deficit and whether any functional load can be applied to it.
2. Biocompatibility of the material will determine whether the alloplast,
in its loaded or unloaded clinical adaptation, will be tolerated by the
tissues.
Use of such implants has been investigated as substitutes for
autogenous grafts and allogenic implants. Attempts were directed
toward creating a porous material that would allow in-growth of bone.
For the fabrication of porous implant materials, several
materials were tested by implantation in the femurs and tibias of dogs,
in the form of cylinders 1.0 cm long and 0.5 cm in diameter. Among
the materials tested, hydroxyapatite and calcium carbonate showed
complete in-growth at 8 weeks with “normal appearing and normally
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mineralizing osseous tissue.” Furthermore, it was observed that in 1
year the calcium carbonate skeleton had been resorbed.
45. BONE MATRIX PROTEINS
Osteonectin
Osteopontin
Fibronectin
Osteocalcin
GROWTH FACTORS
Bone morphogenic protein factor 1 to 7
Transforming growth factor
Insulin like growth factor I & II
Fibroblast growth factor
Platelet derived growth factor
Epidermal growth factor
Retinoic acid
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46. Requirements
1.
Non immunogenic
2.
Strength and resilience to restore hard tissue form where
function is required.
3.
Bend ability, mold ability or carvability to allow for intra
operative adaptation.
4.
Stable and non-reactive surface whether loaded or not.
5.
Modulus of elasticity similar to that of connective tissue at
the implant tissue interface.
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47. HYDROXYAPATITE
It is an alloplastic material. This is a mineral substance,
basically a ceramic which is similar to cortical bone in its composition.
It is inorganic, stable, non absorbable and non biodegradable. They
are osteoconductive and not osteoinductive (ie) they will induce bone
formation when placed next to viable cells, but not when surrounded
by non bone forming tissue like skin.
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48. Hydroxyapatite implants were tested by Holmes, who
implanted them in the mandibles of dogs in which 2-cm defects were
treated with implants placed in metal cast trays. At 4 months, bone
extended into the implant for a distance of 3-5mm. At 4 months, the
entire length of the implant had been bridged in many of the porous
channels. At 6 months, all the channels had been filled with lamellar
bone with well formed osteons. At 12 months, the architecture of the
implant was notably diminished, and 88% of the implant area had
been replaced by regenerated bone. It is noteworthy, however, that
similar defects created in the mandibles of two dogs by the author and
left without an implant were also completely bridged with regenerated
bone at 6 months. In a more recent paper, Holmes tested
experimentally the possibility of cranial reconstruction with porous
hydroxyapatite. The final composition of the implant was 39.3%
hydroxyapatite matrix, 17.2% bone in growth and 43.5% soft tissue
in growth. He concluded that a satisfactory contour can be obtained
and the implant can function at least in part as a bone substitute
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50. CALCIUM PHOSPHATE
Calcium phosphate has also been tested under the form of a
ceramic biodegradable implant called “Synthos” (Miter Inc.,
Worthington, Ohio). This material can be carved into the desired
shape and provides a uniform distribution of large interconnecting
pores from 100 to 300 microns in size. Testing in the mandible, iliac
crest, and inferior orbital rims of dogs was undertaken. Progressive
invasion and replacement of the implant with bone were observed.
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51. ACRYLIC RESINS
Acrylic resin is available as a two component system; a
powder of small PMMA spheres and beads and a liquid monomer.
The polymerization is strongly exothermic (max. Temp. 120oC).
Disadvantages of solid, heat cured acrylics include
-
Difficult handling
-
Problems with thermal, electrical and X-ray conductivity.
Uses include dental implants, submucosal augmentation, contour
correction, cranial defect correction, orbital wall and floor defect
correction, intra ocular lenses
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52. SILICONE RUBBER
Widespread use of this material is due to its biocompatibility
and excellent physical characteristics such as.
-
Thermal stability
-
Oxidative stability
-
Retention of flexibility through wide temperature changes.
Basic building block is dimethylsiloxane with contributions
from other organic side chains i.e., Vinyl and Phenyl condensation
polymerization produces a high molecular weight molecule that has
a highly polar Si-O-Si backbone.
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53. Disadvantages include low tear resistance and that it is
thrombogenic
Preformed silicone rubber implants with or without polymer
fabric can be used to augment chin, zygomatic and nasal
deficiencies including reconstruction of the dorsum, nasal tip and
columella as a custom implant. The disadvantage here being that it
exhibits “Memory”. Therefore it must conform to bone contour in
the relaxed state.
Fluid silicone is clear, colourless odourless and has an oily
lubricant feel to it. It may be injected to lift depressed scars, unless
they are bound down by strong fibrous adhesions. Vertical and
oblique brown lines in the glabella region and nasolabial folds can
be lifted. Sunken facial contours can be augmented. Depressed
defects of the dorsum of nose, defects of nasal tip etc. may be
treated.
Augmentation in a flattened hemifacial contour is
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possible with this material too.
54. POLYETHENES
-
Group of polymers made from ethane type monomers and
include polyethylene and polypropylene.
-
Porous sponge form can be used in reconstruction in non load
bearing areas as in the middle ear. Also used to correct facial
and skull defects, reconstructing the external ear, the trachea
and rebasing the vocal folds.
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55. POLYTETRAFLUROETHYLENE (TEFLON)
- Tetrafluoroethylene gas at high temperature and pressure.
- Non carcinogenic, resistant to corrosion, non adherent and can be
sterilized.
- Used for repair of orbital floor fractures. Available in sheet that are
1.245 mm thick .
- Injectable form consisting of pure . particles of 50-100um.
suspended in 50% glycerin solution is used in paralyzed vocal cords.
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56. PROPLAST
Porous low modulus implant material available in
3 forms basic
material that forms the porous matrix
of proplast is prefluorocarbone polymer.
Advantages of proplast over solid polymers
1.
Improved stabilization, on or in bone, in virtue of rapid
tissue in growth rather than only fibrous encapsulation.
2.
A low modulus characteristic similar to that of soft tissue
which allows it to be bent or molded to appropriate contours.
3.
Easy wettability
4.
Light weight
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57. 5.
Radiolucency
6.
Ease of curving
7.
Stable at very high temperatures, therefore can be sterilized by
autoclaving 3 times.
8.
Proplast sheeting of 1-3mm permits repair of defects of
irregular depth.
Disadvantages
1.
Macrophage response
2.
Increased incidence of infection if contamination occurs during
emergency
3.
Decreased pore size and therefore tissue in growth of the
materials if loaded or compressed
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58. .
Contra indications
1.
As an implant by itself in weight bearing or articulating bony
surface, where compressive loading is likely (TMJ).
2.
Over sinus cavities
3.
Where there is insufficient underlying bone or soft tissue to
prevent collapse in the event of external pressure.
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59. 4.
In patients with systemic disorders that may compromise
tissue in growth or normal wound healing.
5.
In recent areas of infection.
6.
Available in block, preformed or customized implants for
chin, mandible, premaxilla, zygoma, orbit and nasal
augmentation.
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60. POLYURETHANES
-
Implanted in the form of rigid foams for bone replacement
and as bone adhesions.
-
Consists primarily of varied arrangements of polymeric
molecules that share a common structure of urethane group
-
Polyether polyurethanes are capable of long term
implantation with no significant physical changes.
Malar augmentation Mandibular repair Orbital Floor repair Surface scan
model Complex fracture analysis Fetal heart model
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61. POLYAMIDE
-
Is used successfully
in facial augmentation..
-
Can be used alone or in combination with autogenous
tissue in growth as an onlay material for the chin, maxilla,
nasal dorsum.
Disadvantages
Difficulty in contouring and handling and in placement of
the material during surgery.
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62. CALCIUM PHOSPHATE CERAMICS
.
- These are polycrystalline ceramics, and either in porous or dense
forms, serve as permanent bone implants showing no tendency to
resorb in vivo.
- These are are hard tissue prosthetic materials that interact with and
may ultimately become an integral part of living bone.
Limitation :
-
Brittle, low impact resistance and relatively low strength.
-
Biocompatible
- Lack of local systemic toxicity. They bond directly to bone
without the need for porosity.
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63. APPLICATIONS
Osteo Gen is clinically indicated for the contouring and improvement
of alveolar ridge deformities, support and filling of tooth sockets and
cyst defects following extraction or removal, and, for the filling and
repair of marginal, periapical, and periodontal alveolar bony defects.
The granular material is mixed with sterile water or the patient’s blood
to form a putty like material. This material is then transferred to the
osteotomy.
When OsteoGen is implanted into a defect that has been
demonstrated to have healthy vascular circulation, it serves in part as a
material that physically occupies an empty bony void. Thus, a
physical connection is achieved between all sides of the bony void. As
this occurs, the void fills with natural body fluids from each side of
the bony void. OsteoGen then serves as a material platform that allows
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osteoblasts and other cellular material to invade the bony void.
64. OsteoGen granules serve as a osteoconductive material
allowing new bone to be slowly created over several months. An
osteoconductive material such as OsteoGen is defined as a material
that does not inhibit the necessary cellular material from invading the
bony void to lay down new bone. In fact, on osteoconductive
material serves as a physical platform for the osteoblasts to move
into the bony void to lay down the new bone.
A second advantage of OsteoGen is that, as new bone is laid
down, the OsteoGen material resorbs. The resorption process of
OsteoGen occurs progressively over a six to eight month period;
however, depending on the size of the defect and the patient’s age, a
large percentage will have resorbed some time between three to five
months. The net results is that the void is predominately filled with
bone, not a “Bone filling and Augmentation material”.
OsteoGen is avoidate in three sizes: 0.75 gm, 1.50 gm and
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3.00gm.
65. TefGen-FD
Regenerative Membrane, designed for use in treating osseous and
periodontal defects with guided tissue regeneration.
It is available in a size of 25 mm x 30 mm x 0.2 mm.
It finds application in Periodontics, Implantology and Oral Surgery
where particulate bone graft is indicated.
It is available in quantities of 0.5cc and 1cc.
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66. THE SINUS BONE GRAFT
The first use of bone grafting of the maxillary sinus, to
increase bony depth and bulk of osseous tissue for prosthodontic
reasons was in the 1960s by Boyne.
Grafting of maxillary sinus was used at that time to increase
the bulk of bone for later maxillary posterior ridge reduction to
obtain optimal prosthodontic inter arch distance.
However some patients presenting for conventional
complete maxillary and mandibular prosthesis had bulbous or
enlarged tuberosities that was impinging on the inter arch space,
and therefore it was impossible to construct a complete denture.The
removal of bone from mandible is not feasible, and therfore
removal of bone from the maxillary tuberosity was the option
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67. To correct this condition, a Caldwell Luc opening was made
in maxillary antrum, the sinus membrane was elevated, and then an
autogenous particulate marrow cancellous bone (PMCB) graft was
placed in the sinus floor. Approximately 3 months later, the bone
of tuberosity could be reduced along with excess soft tissue.
Additional osseous structure had been obtained by the previous
grafting procedure.
Bone grafting of the maxillary sinus for metallic implants
-
Blade implants
-
Root form implants
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68. Blade implants - During late 1970’s grafting was undertaken
for patients who had large, pneumatized antra and needed blade
implant for construction of fixed ,semi-fixed, or removal
prosthesis for edentulous areas of posterior maxilla.
Autogenous PMCB was usually used as a grafting material and
after a period of three months, blade implant was placed.
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69. Root form implants
With the advent of titanium root form implants, it became
obvious that many possible, posterior maxillary reception sites for
implants were deficient in vertical bone height and width.
Various practitioners then undertook different surgical
techniques to enter the antrum to elevate the sinus membrane and
to place various types of bone graft
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70. Three anatomic locations were utilized to enter the antrum.
1.The classic superior position of the Caldwell Luc opening,
located just anterior to the zygomatic buttress.
2. A mid maxillary entrance, between the level of the crest of the
alveolar ridge and the level of the zygomatic buttress area.
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71. 3. A low position along the anterior surface of the maxilla,
practically at the level of the existing alveolar ridge. Of the three
locations, the third area became quite popular because it gave a
quick access to the sinus floor and enabled the practitioner to make
an antral window to impact the buccal osseous plate into the
antrum, expediously implant the bone graft material, and close the
incision.
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72. Indications for maxillary subantral augmentation
1.
Implant placement in areas of insufficient bone volume
or
decreased inter arch space.
2.
Oro-antral fistula repair.
3.
Alveolar cleft reconstruction
4.
Le fort I down fracture with inter positional grafting
5.
Cancer reconstruction for craniofacial prosthesis
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73. Guidelines to follow for sinus grafting for dental implants may
also include.
1.
Alveolar ridge bone height of less than 10 mm
2.
Less than 4mm of residual bone width
3.
No history of pathosis
4.
No significant history of sinus disease
No anatomic limitations presented by anatomic structures or
scarring after previous surgery
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74. Contraindications to maxillary subantral augmentation
General medical contra indications
1.
Radiation treatment to the maxillary region
2.
Sepsis
3.
Severe medical fragility
4.
Uncontrolled systemic disease
5.
Excessive tobacco abuse
6.
Excessive alcohol or substance abuse
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75. Local factors that may contra indicate subantral augmentation
1.
Maxillary sinus infections (empyema)
2.
Chronic sinusitis
3.
Alveolar scar ablation
4.
Odontogenic infections
5.
Inflammatory or pathologic lesions.
6.
Severe allergic rhinitis.
Healing period for the graft
Because severe atrophy results in an unfavorable
vascularization of the maxillary alveolar process and the
adjacent maxillary sinus, the grafting material should be allowed
to heal 1 to 2 months longer than normal.
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76. Treatment Planning for Sinus Grafts
Treatment planning for dental implants must be based on
prosthetic considerations and, in all but the most simple cases,
should involve a complete dental restorative workup. In most
cases, this will minimally involve the following :
1.
Facebow-mounted, articulated casts placed in centric
relation.
2.
Diagnostic wax up.
3.
Presurgical equilibration or restorative measures
4.
Surgical stent manufactured by using a surveyor.
5.
Radiographic or computerized tomographic verification
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77. Use of Allografts for Sinus Grafting
The development of the sinus elevation procedure
originates from the clinical reports of Boyne, James and Tatum,
who recognized the need to supplement bone inferior to the
maxillary sinus to enable clinicians to perform alveolectomies and
subsequently place implants. Their efforts led to the development
of a technique whereby the external wall of bone, surrounding the
maxillary sinus was perforated with a careful osteotomy. In
Tatum’s technique, the osseous wall and underlying membrane
were infractured medially and pushed in a superior direction.. The
space created by this infracture was filled with an autogenous bone
graft. Boyne and James made no attempt to retain this external
wall of bone, when dissecting the sinus membrane away from the
underlying bone.
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78. Allografts
Most of the cases are limited to the use of one specific type
of allograft. is demineralized freeze dried bone, without any other
supplements. The choice of the demineralized material over the
mineralized sources was merely to add an extra degree of safety to
the material.
The material has been used successfully for bone grafting
both in periodontal defects and around implants for reasonable
amount of time. It also gives a patient the option to avoid a
secondary site from which bone is harvested. (hip, chin, etc), which
may be more traumatic than placement of the implants.
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79. As in all procedures, there are conditions that are not
conducive to the use of an allograft for sinus augmentation. The
main situation would be in those patients who lack adequate bone in
the premaxillary area to support implants under loading (patients
who have fewer than 7 mm of bone from canine to canine). While
the antral augmentation might be successful, all the forces of
occlusion will be generated on the sinus placed implants, ultimately
causing overload and failure.
The second contra indication would be inadequate
buccopalatal width of bone, in association with the deficiency in
height, adjacent to the maxillary sinus.
Finally, patients who have fewer than 4 to 5 mm of bone and wish
to have the implants placed at the time of sinus augmentation would
best be treated with a large block inlay graft, which could receive
the implant simultaneously. Major vertical height advances, which
are difficult, are also best treated with autogenous block grafts.
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80. The bone resorption process that occurs following tooth loss
is four times greater in the maxilla than in the mandible. The bone
loss encountered in the posterior regions of the edentulous
maxillary arch is higher than in the posterior mandible due to the
pneumatization of the maxillary sinus. Furthermore, the maxillary
cortex is thinner and the trabecular structure is less dense than in the
mandible ; the posterior maxilla usually exhibits the poorest bone
quality. Hence, the quantity and quality of bone necessary for
implant supported restorations are less likely to be available in the
maxilla. For these reasons, dental implants placed in the posterior
maxilla are likely to have higher failure rates than implants placed in
the anterior maxilla or mandible.
Different bone grafting materials have been used for this
purpose, including autogenous graft that the iliac crest and chin
region, allo-grafts such as freeze dried demineralized bone, and
alloplasts such as porous hydroxyapatite and non-porous
hydroxyapatite.
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82. Sinus Grafting with Calvarial Bone
The cranial vault has always been an extremely valuable
source of bone grafts. Facility in harvesting, a simple post surgical
period, and solid construction make calvarial bone an ideal material
for reconstruction of the cranial or facial skeleton.
Although bone from the cranial vault had been used as early
as 1980 as part of an osteocutaneous flap by Konig and Muller, the
first autogenous cranial bone graft was apparently performed by
Dandy in 1929. Tessier, however, was the first to popularize the
use of the calvarium as a donor site of grafts for cranial and facial
reconstruction.
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83. Harvesting of the cranial bone grafts
The harvesting is done in the parietal region, generally on the
right side (nondominant hemisphere) behind the coronal suture, and
approximately 3cm lateral to the sagittal suture or midline of the
skull.
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84. Grafting of the sinus floor
The construction is homogenous only if the sinus cavity is
partitioned in its inferior part by a large graft that rests on the sinus walls
and becomes the roof of the cavity to be filled. Thus, the sinus graft
starts with the positioning of a large rectangular strip of cranial bone 10
to 15mm above the floor. Before its insertion, the vertical side of the
graft is thinned with a bur, and several holes are made to facilitate its
revascularization
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85. Tibial Cancellous Autograft for Sinus Grafting
Various donor sites and bone harvesting technique are used
for the augmentation of the sinus floor prior to the placement of
osseointegrated implants, but seldom has the proximal lateral tibial
graft been utilized, despite its excellent accessibility and
availability. When the bone volume or bone quality is extremely
deficient, tibial graft is recommended.
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86. Healing
The cancellous autogenous bone graft contains endosteal
osteoblasts, which can survive the transplantation process when handled
appropriately. Also transplanted are a host of growth factors, which
provide the stimulus for mesenchymal cell differentiation into
osteoblasts, and growth promoters, which accelerate bone production by
these newly differentiated cells.
The cancellous graft heals by a combination of formation of new
bone by the transplanted osteoblasts, followed by the formation and
remodeling of new bone by the cells recruited from the periphery.
The cortioccancellous block graft provides transplanted
osteoblasts and growth factors as well as structural rigidity, which is
frequently required when implants are placed simultaneously. However,
the cortical portion of the graft is slow to revascularize and thus may be
more prone to infection. The structural rigidity of the graft allows
accurate implant placement, independent of the thickness of the sinus
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floor.
87. The healing of these bone grafts follows a course of events
that starts with basic wound healing and follows with bone
remodeling. Phase I bone healing includes osteoid production and
cellular proliferation.
Phase 2 includes remodeling of the
disorganized phase 1 osteoid and replacement with lamellar bone.
In autogenous grafts, surviving osteoblasts and other cells are
responsible for primary bone production. These transplanted cells
survive through diffusion of nutrients during the first 4 days of
transplantation, during graft revascularization. The amount of bone
eventually produced by the transplanted cells is directly proportional
to the density of the surviving endosteal osteoblasts.
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88. Autogenous Bone Combined with Demineralized Bone
Demineralized bone is bone that has had its mineral removed
through an acid treatment and then is washed and lyophilized until
reconstituted for use. When autogenous bone is demineralized, the
remaining organic substrate contains bone morphogenetic proteins.
Because the amount of autogenous bone available from the
jaws may be limited, demineralized bone can be combined with
autogenous bone to expand the graft’s volume. This combination of
autogenous bone expanded with allogeneic demineralized bone is a
useful method for obtaining phase I bone formation from the
autogenous bone graft as well as phase II bone formation from the
demineralized bone, and establishing the bulk of the graft.
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89. Subnasal Elevation and Augmentation Procedure.
Surgical scrub is performed in the usual manner for the
placement of implants. After the surgical team scrubs, the patient is
draped. For intra oral preparation of the surgical site, a Chlorhexidine
antiseptic scrub and rinse can be used. Iodophor or Chlorhexidine
antiseptics can be used for preoperative extra oral scrubbing of the skin.
Infiltration anesthesia has been successfully used, however a
more significant regional anesthesia occurs when the secondary division
of the maxillary nerve (V2) is blocked. With this technique, anesthesia
of the hemimaxilla, side of the nose, cheek, lip and sinus area can be
achieved.
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90. Proper angulation of the needle prevents penetration into the
nasal cavity through the medial wall of the pterygopalatal fossa.
A full thickness incision is made on the crest of the maxillary
ridge, from the distal end of the canine region to the distal end of the
contra lateral canine region.
A nasal undercut region is typically formed at the junction of the
lateral and inferior piriform rim that often corresponds to the area of
placement for implant (canine area). The nasal mucosa in this region is
elevated with a soft tissue curette in a manner similar to that used for
elevation of the mucoperiosteum in subantral augmentation procedures.
Depending on the depth of the impression behind the piriform rim, the
nasal mucosa is elevated approximately 3 to 5 mm and then augmented
with graft material.
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91. For subnasal augmentation, approximately 5 ml of cortical and
trabecular autogenous bone is harvested from the mandibular symphysis
and ground in a mill. This bone can then be mixed with freeze dried
bone allograft (if necessary to expand the volume) in 50 : 50 ratio and
compressed into a 1 - and 3 -ml tuberculin syringe. The mixture is
applied from the posterior regions of the nasal space to the most anterior
labial region of the nasal spine and piriform rim.
When subnasal augmentation is performed in conjunction with
iliac graft reconstruction of the maxilla, a 2- to 5- mm septal reduction is
performed in the anterior septum, taking care to avoid tears of the
mucosal lining of the nasal septum. A block graft that is 5 to 7 mm in
height is fixed with one or two miniscrews placed laterally; these can be
left permanently if facial augmentation is performed over them. This
provides enough stabilization for standard implants. If additional ridge
width is necessary, block grafts from the anterior mandible or ramus can
be used by fixation to the buccal aspect of the anterior maxilla. After
maturization of the graft, the appropriate sized implants can be placed.
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92. Prior to suturing, the periosteum of the mucosal flap
covering the graft is horizontally scored with a scalpel to allow
tension free wound closure. The primary crestal incision and the
vertical relieving incisions are closed with 3-0 chromic or silk
sutures in either an interrupted or continuous mattress fashion. This
area should be permitted to heal for 4 to 6 months before implant
placement. In addition, the provisional partial denture or complete
denture should be adjusted to avoid contact with the grafted area.
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97. BONE GRAFT HANDLING
It is essential that the viability of the bone in the period
between its harvest and its placement be maintained. There are 4
important factors affecting graft cell viability .
1. Tonicity of storage medium
2. Temperature of storage medium
3. Sterility of bone cell handling
4. Trauma of bone handling.
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98. 1. STORAGE MEDIA
Distilled water and other hypotonic solutions are
contraindicated as bone cell storage media. These hypotonic
solution diffuse through the cell membrane resulting in swelling of
cytoplasm, leading to cell death by physical rupture. Hypertonic
solution are also contra indicated as they draw the free water away
from cytoplasmic bone cells.
Blood and blood soaked sponges should not be used as
clotted blood has many membrane toxic intermediates of platelet
aggregation and fibrin clot formation including lysozyme, fibrin
split products, osteoclastic, chemotactic, factors etc. Also the blood
soaked cells undergo a certain degree of drying, causing cell death.
Saline is a good storage media, however the cellular activity
is reduced after saline immersion because bone cell growth factors
are washed out of cells stored in saline.
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99. Tissue culture media, is an ideal storage medium. These are
isotonic balanced solution buffered at Ph. 7.42 and have organic and
inorganic cell nutrients. The advantage of tissue storage media is that
they maintain absolute cell viability, cell activity and do not deplete intra
cellular bone maintenance and growth factors.
2. TEMPERATURE
Chilling to point of physical freezing, maintains better cell
viability. Heating a storage medium is detrimental to survival as it
causes direct membrane and intra cellular protein coagulation with
enhanced toxicity from exogeneous agents. The media is kept
refrigerated at 4oC until its use. It is then allowed to warm towards room
temperature until placement.
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100. 3. STERILITY OF HANDLING
Incorporation of just a small inoculum of microorganism can
result in either clinical infection or subclinical graft cell death
yielding little bone. If overt contamination occur, graft should be
discarded, with another harvest taken. Graft can be irregular with
storage medium and finally antibiotic solution. Never autoclave
irradiate or treat it with any disinfectants or soaps.
4. ROUGH HANDLING
Bone cells are relatively resistant to rough handling by
compression or shearing forces. However excessive trauma by
crushing or when particulated into very small pieces, has caused
inflammation within tissue bud. Therefore trauma should be minimal
and tissue handling should be done with utmost care.
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101. BIOLOGICAL MECHANISMS IN BONE GRAFTING
New bone formation occurs through three biologic
mechanisms
1.
Osteogenesis
2.
Osteo conduction
3.
Osteo induction
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102. 1. Osteogenesis : Is the production of new bone by proliferation,
osteoid production and mineralization by transplanted osteocompetent cells. It is the main mechanism exploited by surgeons to
graft large loss defects and it accounts for the greatest amount of bone
formed by the graft.
2. Osteoconductive : Is the production of new bone by the
proliferation and migration of local host osteocompetent cells along a
conduct. The conduct may be local vessels, epincurium allogeneic
bone or certain alloplasts the HA blocks. This accounts for a small
amount of the bone derived in bone reconstruction. This bone usually
originates from the endosteum of the host bone ends or residual
periosteum.
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103. 3. Osteoinduction: Is the formation of bone by connective tissue
cells trans formed into osteocompetent cells by inductive agents
usually proteins such as bone morphogenetic protein (BMP), skeletal
growth factor and osteogenin. This mechanism accounts for a small
amount of the bone produced by bone graft systems. This is an
important mechanism in inducing the recipient connective tissue
fibroblasts about the graft into a periosteum which accounts, partily
for its longevity.
Bone regeneration is responsible for healing of a bony graft
consisting of autogenous particulate bone and cancellous bone
marrow. The amount of bone produced in the graft is dependent on
the cellular density of the transplanted cancellous bone.
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104. The critical bone transplant density as suggested by
simmons at the donor site is 2000 osteoblasts /mg of bone and
Frieden stein has reported that 1 106 osteocomponent cells/ cum are
needed within the recipient tissue bed for the formation of new
bone. The principle is basically to use cellular cancellous bone,
harvest a sufficient quantity of it and compact it into a high cell/unit
volume for maximal bone formation. It is for this reason the ilium is
the preferred donor site (4 times ostogenic cellularity of either
cortical bone sources and twice that of other cancellous bone
sources) 8-10cc of cancellous bone for each 1 cm of defect is a
simple yardstict one can fellow to ensure sufficient harvest of donor
bone. The bone can be compacted in by simple syringe compression
or hand instrument compression.
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105. The transplanted cellular bone mainly the endosteal
osteoblasts on the cancellous surface, proliferate and produce new
osteoild. This bone produced is a cellular woven type of bone with
little structural organization. This is the first phase of bone and this
soon undergoes resorption and replacement to be replaced by a
second phase bone which is derived from the local cell population
of the host and is more structural. This phase is also responsible for
the longevity of the bone ossicle. Both the naturation of the bone
oesicle as well as its volume maintaining endosteal and periosteal
systems determine not only the longevity of the graft but as its
ability to remodel under applicances and even to osteointegrate
dental implants. It is also seen that the height and width of the graft
obtained at the time of its placement to the maximum it will ever be
as the osteocompetent cells proliferate and produce osteoid within
the limits of the cancellous bone volume.
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106. GOALS OF RECONSTRUCTION / CRITERIA OF SUCCESS
There are certain goals toward which reconstruction should strive.
These are :
1. Restoration of bone continuity
This, especially, in respect to the mandible helps in three ways
namely.
a. Mandibular continuity restores much of the mechanical stability to
the function of mastication, speech and deglutition. Residual
musculature, adaptation of accessory muscles and the muscle of facial
expression provide adequate and sufficient function.
b. The patients self image improves. Thus he become more willing to
return to a normal life style.
c. Bony continuity of any part of the facial skeleton adds to more
normal contours and appearance, thereby providing foundation upon
which more enacting cosmetic procedure may be performed.
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107. 2.
Restoration of osseous bulk : A thin and volume deficient
transplant is often associated with certain problems such as
a. They are prone to fractures
b. Usually do not supply sufficient contour.
c. Rarely support a prosthetic appliance
Osseous bulk is achieved by adhering to the biologic
principles of graft healing i.e.
i. Sufficient quantity of cellular cancellous graft materials
should be placed.
ii. Should be firmly fixated into a vascular and cellular tissue bed
free of contamination.
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108. 3. Restoration of alveolar bone height
Sufficient alveolar bone height is essential for the retention and
stability of conventional prosthesis and is necessary for implant
systems to osteointegrate effectively. Good alveolar bone height is
accomplished in the dissection to prepare the soft tissue for the graft.
The dissection must free all scar within the space of the mandible to a
this overlying mucosa (1-3mm), without perforation into the oral
cavity. This is achieved by blunt dissection in this area with the
instruments spread parallel to the ridge or crestal scar, or by sharp
dissection palpating the maxillary dentition as a guide to tissue
thickness, or by dissecting under guidance from another member of
the surgical team who has placed a gloved hand within the oral
cavity.
4. Bone maintenance
Maintenance of the bone ossicle throughout the left time of the
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patient is one of the most important aspects of a successful
109. Lack of bone formation or
b. Resorption of their non viable mineral matrix in the first 6
months.
Grafts that fail in the second phase will show resorption with
in 6-18 months. Grafts that maintain or increase their radiographic
mineral density beyond 18 months almost always maintain their
aside throughout the patients lifetime and can be considered
successful.
5. Elimination Soft tissue deficiencies
Residual soft tissue deficiencies often restrict tongue and lip
function and create unseating forces, and prevent a seal for
prosthesis. Such soft tissue deficiencies are eliminated either prior
to bone graft tissue flaps or after bone grafting with releasing
procedures using SSE or dermal grafts.
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110. 6. Restoration of facial contours
It is essential that facial form and function be restored and it is
only after this is done that cosmetic onlay grafts, contouring procedures
and scar revisions care staged.
ALLOPLASTIC CRIBS
All have features of biologic encapsulation non resorbability and
biologic inadaptability.
1. Dacron coated polyurethane crubs.
- Radiolucent therefore do not obscure post operative radiographic
of graft consolidation.
- Easily cut for contouring and shaping.
- Moderately flexible material but rigid enough to maintain its
shape.
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- Pore size is small but large enough to allow capillary in growth.
115. Summary and conclusion
The essence of a successful bone grafting is the variable
transplantation of osteocompetent cells. These cells must be sufficient
in number and recipient tissue bed must be sufficiently cellular and
vascular to develop and maintain a self remodeling bone.
Numerous grafts and its harvesting techniques have been
proposed. there is no real difference in the osteogenic potential of
osteocompetent cells from any of the popular donor sites.
The use of cortico-cancellous bone grafts for reconstruction was
proposed as it has a higher biomechanical rigitidy.
Autogenous bone grafts are used for various purposes like
bridging gaps in orthognathic surgeries and in preparing the implant
sites. The advantage of these graft is that large open areas will yield to
revascularisation easily hence bringing about new bone formation.
Various techniques of harvesting bone either black or particulate bone
by the use of trephine has advantages over open technique as morbidity
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and gait disturbance chance are low.
116. REFERENCES
1. Adll R, Eriksson B, Lekholm U, Branemark P.I. Jemt T.A. longterm folow-up study of osseointegrated implants in the
treatment of totally edentulous jaws. Int J Oral Maxillofac
Implants 1990;5:347-35.
2. Albrektsson T, Zarb GA, Worthington P, Eriksson RA. The
Long-term efficcacy of currently used dental implants: a
review and proposed criteria of success. Int J oral Maxillofac
Impalnts 1986;1:11-25.
3. Boyne PJ, James RA. Grafting of the maxillary sinus floor with
autogenous marrow and bone. J Oral Surg 1980; 38:63-616.
4. Branemark P-1, Adell R, Albrektsson T. An expermental and
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